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Abstract: Separating concentrations of carbon monoxide (CO) in the boundary layer from the rest of the atmosphere with nadir satellite measurements is of particular importance to differentiate emission from transport. Although thermal infrared (TIR) satellite sounders are considered to have limited sensitivity to the composition of the near-surface atmosphere, previous studies show that they can provide information on CO close to the ground in case of high thermal contrast. In this work we investigate the capability of IASI (Infrared Atmospheric Sounding Interferometer) to retrieve near-surface CO concentrations, and we quantitatively assess the influence of thermal contrast on such retrievals. We present a 3-part analysis, which relies on both theoretical forward simulations and retrievals on real data, performed for a large range of negative and positive thermal contrast situations. First, we derive theoretically the IASI detection threshold of CO enhancement in the boundary layer, and we assess its dependence on thermal contrast. Then, using the optimal estimation formalism, we quantify the role of thermal contrast on the error budget and information content of near-surface CO retrievals. We demonstrate that, contrary to what is usually accepted, large negative thermal contrast values (ground cooler than air) lead to a better decorrelation between CO concentrations in the low and the high troposphere than large positive thermal contrast (ground warmer than the air). In the last part of the paper we use Mexico City and Barrow as test cases to contrast our theoretical predictions with real retrievals, and to assess the accuracy of IASI surface CO retrievals through comparisons to ground-based in-situ measurements. © 2017 Elsevier Ltd
BibTeX:
@article{Bauduin2017,
  author = {Bauduin, S. and Clarisse, L. and Theunissen, M. and George, M. and Hurtmans, D. and Clerbaux, C. and Coheur, P.-F.},
  title = {IASI's sensitivity to near-surface carbon monoxide (CO): Theoretical analyses and retrievals on test cases},
  journal = {Journal of Quantitative Spectroscopy and Radiative Transfer},
  year = {2017},
  volume = {189},
  pages = {428-440},
  doi = {10.1016/j.jqsrt.2016.12.022}
}
Abstract: In order to recognize the importance of ozone (O3) in the troposphere and lower stratosphere in the tropics, a DIAL (differential absorption lidar) tropospheric O3 lidar system (LIO3TUR) was developed and installed at the Université de la Réunion campus site (close to the sea) on Reunion Island (southern tropics) in 1998. From 1998 to 2010, it acquired 427 O3 profiles from the low to the upper troposphere and has been central to several studies. In 2012, the system was moved up to the new Maïdo Observatory facility (2160-l. - metres above mean sea level) where it started operation in February 2013. The current system (LIO3T) configuration generates a 266 beam obtained with the fourth harmonic of a Nd:YAG laser sent into a Raman cell filled up with deuterium (using helium as buffer gas), generating the 289 and 316 beams to enable the use of the DIAL method for O3 profile measurements. The optimal range for the actual system is 6-19ga.m.s.l., depending on the instrumental and atmospheric conditions. For a 1gh integration time, vertical resolution varies from 0.7gkm at 6ga.m.s.l. to 1.3gkm at 19ga.m.s.l., and mean uncertainty within the 6-19gkm range is between 6 and 13g%. Comparisons with eight electrochemical concentration cell (ECC) sondes simultaneously launched from the Maïdo Observatory show good agreement between data sets with a 6.8g% mean absolute relative difference (D) between 6 and 17ga.m.s.l. (LIO3T lower than ECC). Comparisons with 37 ECC sondes launched from the nearby Gillot site during the daytime in a ±24gh window around lidar shooting result in a 9.4g% D between 6 and 19ga.m.s.l. (LIO3T lower than ECC). Comparisons with 11 ground-based Network for Detection of Atmospheric Composition Change (NDACC) Fourier transform infrared (FTIR) spectrometer measurements acquired during the daytime in a ±24gh window around lidar shooting show good agreement between data sets with a D of 11.8g% for the 8.5-16gkm partial column (LIO3T higher than FTIR), and comparisons with 39 simultaneous Infrared Atmospheric Sounding Interferometer (IASI) observations over Reunion Island show good agreement between data sets with a D of 11.3g% for the 6-16gkm partial column (LIO3T higher than IASI). ECC, LIO3TUR and LIO3T O3 monthly climatologies all exhibit the same range of values and patterns. In particular, the Southern Hemisphere biomass burning seasonal enhancement and the ozonopause altitude decrease in late austral winter-spring, as well as the sign of deep convection bringing boundary layer O3-poor air masses up to the middle-upper troposphere in late austral summer, are clearly visible in all data sets. © Author(s) 2017.
BibTeX:
@article{Duflot2017,
  author = {Duflot, V. and Baray, J.-L. and Payen, G. and Marquestaut, N. and Posny, F. and Metzger, J.-M. and Langerock, B. and Vigouroux, C. and Hadji-Lazaro, J. and Portafaix, T. and De Mazière, M. and Coheur, P.-F. and Clerbaux, C. and Cammas, J.-P.},
  title = {Tropospheric ozone profiles by DIAL at Maïdo Observatory (Reunion Island): System description, instrumental performance and result comparison with ozone external data set},
  journal = {Atmospheric Measurement Techniques},
  year = {2017},
  volume = {10},
  pages = {3359-3373},
  doi = {10.5194/amt-10-3359-2017}
}
Abstract: The isotopic composition of water vapour in the North Atlantic free troposphere is investigated with Infrared Atmospheric Sounding Interferometer (IASI) measurements of the D/H ratio (δD) above the ocean. We show that in the vicinity of West Africa, the seasonality of δD is particularly strong (130 ‰), which is related with the influence of the Saharan heat low (SHL) during summertime. The SHL indeed largely influences the dynamic in that region by producing deep turbulent mixing layers, yielding a specific water vapour isotopic footprint. The influence of the SHL on the isotopic budget is analysed on various time and space scales and is shown to be large, highlighting the importance of the SHL dynamics on the moistening and the HDO enrichment of the free troposphere over the North Atlantic. The potential influence of the SHL is also investigated on the inter-annual scale as we also report important variations in δD above the Canary archipelago region. We interpret the variability in the enrichment, using backward trajectory analyses, in terms of the ratio of air masses coming from the North Atlantic and air masses coming from the African continent. Finally, the interest of IASI high sampling capabilities is further illustrated by presenting spatial distributions of δD and humidity above the North Atlantic from which we show that the different sources and dehydration pathways controlling the humidity can be disentangled thanks to the added value of δD observations. More generally, our results demonstrate the utility of δD observations obtained from the IASI sounder to gain insight into the hydrological cycle processes in the West African region. © Author(s) 2017.
BibTeX:
@article{Lacour2017,
  author = {Lacour, J.-L. and Flamant, C. and Risi, C. and Clerbaux, C. and Coheur, P.-F.},
  title = {Importance of the Saharan heat low in controlling the North Atlantic free tropospheric humidity budget deduced from IASI δd observations},
  journal = {Atmospheric Chemistry and Physics},
  year = {2017},
  volume = {17},
  pages = {9645-9663},
  doi = {10.5194/acp-17-9645-2017}
}
Abstract: Methane (CH4) and ammonia (NH3) directly and indirectly affect the atmospheric radiative balance with the latter leading to aerosol generation. Both have important spectral features in the Thermal InfraRed (TIR) that can be studied by remote sensing, with NH3allowing discrimination of husbandry from other CH4sources. Airborne hyperspectral imagery was collected for the Chino Dairy Complex in the Los Angeles Basin as well as in situ CH4, carbon dioxide (CO2) and NH3data. TIR data showed good spatial agreement with in situ measurements and showed significant emissions heterogeneity between dairies. Airborne remote sensing mapped plume transport for ∼20 km downwind, documenting topographic effects on plume advection. Repeated multiple gas in situ measurements showed that emissions were persistent on half-year timescales. Inversion of one dairy plume found annual emissions of 4.1 × 105 kg CH4, 2.2 × 105 kg NH3, and 2.3 × 107 kg CO2, suggesting 2300, 4000, and 2100 head of cattle, respectively, and Chino Dairy Complex emissions of 42 Gg CH4and 8.4 Gg NH3implying ∼200k cows, ∼30% more than Peischl et al. (2013) estimated for June 2010. Far-field data showed chemical conversion and/or deposition of Chino NH3occurs within the confines of the Los Angeles Basin on a four to six h timescale, faster than most published rates, and likely from higher Los Angeles oxidant loads. Satellite observations from 2011 to 2014 confirmed that observed in situ transport patterns were representative and suggests much of the Chino Dairy Complex emissions are driven towards eastern Orange County, with a lesser amount transported to Palm Springs, CA. Given interest in mitigating husbandry health impacts from air pollution emissions, this study highlights how satellite observations can be leveraged to understand exposure and how multiple gas in situ emissions studies can inform on best practices given that emissions reduction of one gas could increase those of others. © 2016 Elsevier Ltd
BibTeX:
@article{Leifer2017,
  author = {Leifer, I. and Melton, C. and Tratt, D.M. and Buckland, K.N. and Clarisse, L. and Coheur, P. and Frash, J. and Gupta, M. and Johnson, P.D. and Leen, J.B. and Van Damme, M. and Whitburn, S. and Yurganov, L.},
  title = {Remote sensing and in situ measurements of methane and ammonia emissions from a megacity dairy complex: Chino, CA},
  journal = {Environmental Pollution},
  year = {2017},
  volume = {221},
  pages = {37-51},
  doi = {10.1016/j.envpol.2016.09.083}
}
Abstract: Concentrated agricultural activities and animal feeding operations in the northeastern plains of Colorado represent an important source of atmospheric ammonia (NH3). The NH3 from these sources contributes to regional fine particle formation and to nitrogen deposition to sensitive ecosystems in Rocky Mountain National Park (RMNP), located ∼80 km to the west. In order to better understand temporal and spatial differences in NH3 concentrations in this source region, weekly concentrations of NH3 were measured at 14 locations during the summers of 2010 to 2015 using Radiello passive NH3 samplers. Weekly (biweekly in 2015) average NH3 concentrations ranged from 2.66 to 42.7μ-3, with the highest concentrations near large concentrated animal feeding operations (CAFOs). The annual summertime mean NH3 concentrations were stable in this region from 2010 to 2015, providing a baseline against which concentration changes associated with future changes in regional NH3 emissions can be assessed. Vertical profiles of NH3 were also measured on the 300 m Boulder Atmospheric Observatory (BAO) tower throughout 2012. The highest NH3 concentration along the vertical profile was always observed at the 10 m height (annual average concentration of 4.63 μgm-3), decreasing toward the surface (4.35g μg-3) and toward higher altitudes (1.93g μg-3). The NH3 spatial distributions measured using the passive samplers are compared with NH3 columns retrieved by the Infrared Atmospheric Sounding Interferometer (IASI) satellite and concentrations simulated by the Comprehensive Air Quality Model with Extensions (CAMx). The satellite comparison adds to a growing body of evidence that IASI column retrievals of NH3 provide very useful insight into regional variability in atmospheric NH3, in this case even in a region with strong local sources and sharp spatial gradients. The CAMx comparison indicates that the model does a reasonable job simulating NH3 concentrations near sources but tends to underpredict concentrations at locations farther downwind. Excess NH3 deposition by the model is hypothesized as a possible explanation for this trend. © 2017 Author(s).
BibTeX:
@article{Li2017,
  author = {Li, Y. and Thompson, T.M. and Van Damme, M. and Chen, X. and Benedict, K.B. and Shao, Y. and Day, D. and Boris, A. and Sullivan, A.P. and Ham, J. and Whitburn, S. and Clarisse, L. and Coheur, P.-F. and Collett, J.L.},
  title = {Temporal and spatial variability of ammonia in urban and agricultural regions of northern Colorado, United States},
  journal = {Atmospheric Chemistry and Physics},
  year = {2017},
  volume = {17},
  pages = {6197-6213},
  doi = {10.5194/acp-17-6197-2017}
}
Abstract: Aerosols have a potentially large effect on climate, particularly through their interactions with clouds, but the magnitude of this effect is highly uncertain. Large volcanic eruptions produce sulfur dioxide, which in turn produces aerosols; these eruptions thus represent a natural experiment through which to quantify aerosol-cloud interactions. Here we show that the massive 2014-2015 fissure eruption in Holuhraun, Iceland, reduced the size of liquid cloud droplets - consistent with expectations - but had no discernible effect on other cloud properties. The reduction in droplet size led to cloud brightening and global-mean radiative forcing of around -0.2 watts per square metre for September to October 2014. Changes in cloud amount or cloud liquid water path, however, were undetectable, indicating that these indirect effects, and cloud systems in general, are well buffered against aerosol changes. This result will reduce uncertainties in future climate projections, because we are now able to reject results from climate models with an excessive liquid-water-path response. © 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.
BibTeX:
@article{Malavelle2017,
  author = {Malavelle, F.F. and Haywood, J.M. and Jones, A. and Gettelman, A. and Clarisse, L. and Bauduin, S. and Allan, R.P. and Karset, I.H.H. and Kristjánsson, J.E. and Oreopoulos, L. and Cho, N. and Lee, D. and Bellouin, N. and Boucher, O. and Grosvenor, D.P. and Carslaw, K.S. and Dhomse, S. and Mann, G.W. and Schmidt, A. and Coe, H. and Hartley, M.E. and Dalvi, M. and Hill, A.A. and Johnson, B.T. and Johnson, C.E. and Knight, J.R. and O'Connor, F.M. and Stier, P. and Myhre, G. and Platnick, S. and Stephens, G.L. and Takahashi, H. and Thordarson, T.},
  title = {Strong constraints on aerosol-cloud interactions from volcanic eruptions},
  journal = {Nature},
  year = {2017},
  volume = {546},
  pages = {485-491},
  doi = {10.1038/nature22974}
}
Abstract: Emission of volcanic gas is thought to be the dominant process by which volatiles transit from the deep earth to the atmosphere. Volcanic gas emissions, remain poorly constrained, and volcanoes of Peru are entirely absent from the current global dataset. In Peru, Sabancaya and Ubinas volcanoes are by far the largest sources of volcanic gas. Here, we report the first measurements of the compositions and fluxes of volcanic gases emitted from these volcanoes. The measurements were acquired in November 2015. We determined an average SO2 flux of 15.3 ± 2.3 kg s− 1 (1325-ton day− 1) at Sabancaya and of 11.4 ± 3.9 kg s− 1 (988-ton day− 1) at Ubinas using scanning ultraviolet spectroscopy and dual UV camera systems. In-situ Multi-GAS analyses yield molar proportions of H2O, CO2, SO2, H2S and H2 gases of 73, 15, 10 1.15 and 0.15 mol% at Sabancaya and of 96, 2.2, 1.2 and 0.05 mol% for H2O, CO2, SO2 and H2S at Ubinas. Together, these data imply cumulative fluxes for both volcanoes of 282, 30, 27, 1.2 and 0.01 kg s− 1 of H2O, CO2, SO2, H2S and H2 respectively. Sabancaya and Ubinas volcanoes together contribute about 60% of the total CO2 emissions from the Central Volcanic zone, and dominate by far the total revised volatile budget of the entire Central Volcanic Zone of the Andes. © 2017 Elsevier B.V.
BibTeX:
@article{Moussallam2017,
  author = {Moussallam, Y. and Tamburello, G. and Peters, N. and Apaza, F. and Schipper, C.I. and Curtis, A. and Aiuppa, A. and Masias, P. and Boichu, M. and Bauduin, S. and Barnie, T. and Bani, P. and Giudice, G. and Moussallam, M.},
  title = {Volcanic gas emissions and degassing dynamics at Ubinas and Sabancaya volcanoes; implications for the volatile budget of the central volcanic zone},
  journal = {Journal of Volcanology and Geothermal Research},
  year = {2017},
  volume = {343},
  pages = {181-191},
  doi = {10.1016/j.jvolgeores.2017.06.027}
}
Abstract: Satellite-derived enhancement ratios of NH3 relative to CO column burden (ERNH3/CO) in fires over Alaska, the Amazon, and South Equatorial Africa are 35, 45, and 70% lower than the corresponding ratio of their emissions factors (ERNH3/CO) from biomass burning derived from in situ observations. Simulations performed using the Geophysical Fluid Dynamics Laboratory AM3 global chemistry-climate model show that these regional differences may not entirely stem from an overestimate of NH3 emissions but rather from changes in the gas-aerosol partitioning of NH3 to NH4 +. Differences between (ERNH3/CO) and (EFNH3/CO) are largest in regions where is high, consistent with the production of NH4NO3. Biomass burning is estimated to contribute 11–23% of the global burden and direct radiative effect (DRE) of NH4NO3 (−15 to −28 mW m−2), despite accounting for less than 6% of the global source of NH3. Production of NH4NO3 is largely concentrated over the Amazon and South Equatorial Africa, where its DRE can reach −1.9 W m−2 during the biomass burning season. ©2017. American Geophysical Union. All Rights Reserved.
BibTeX:
@article{Paulot2017,
  author = {Paulot, F. and Paynter, D. and Ginoux, P. and Naik, V. and Whitburn, S. and Van Damme, M. and Clarisse, L. and Coheur, P.-F. and Horowitz, L.W.},
  title = {Gas-aerosol partitioning of ammonia in biomass burning plumes: Implications for the interpretation of spaceborne observations of ammonia and the radiative forcing of ammonium nitrate},
  journal = {Geophysical Research Letters},
  year = {2017},
  volume = {44},
  pages = {8084-8093},
  doi = {10.1002/2017GL074215}
}
Abstract: Formic acid (HCOOH) concentrations are often underestimated by models, and its chemistry is highly uncertain. HCOOH is, however, among the most abundant atmospheric volatile organic compounds, and it is potentially responsible for rain acidity in remote areas. HCOOH data from the Infrared Atmospheric Sounding Interferometer (IASI) are analyzed from 2008 to 2014 to estimate enhancement ratios from biomass burning emissions over seven regions. Fire-affected HCOOH and CO total columns are defined by combining total columns from IASI, geographic location of the fires from Moderate Resolution Imaging Spectroradiometer (MODIS), and the surface wind speed field from the European Centre for Medium-Range Weather Forecasts (ECMWF). Robust correlations are found between these fire-affected HCOOH and CO total columns over the selected biomass burning regions, allowing the calculation of enhancement ratios equal to 7.30g × g 10g'3g ±g 0.08g × g 10g'3g molg molg'1 over Amazonia (AMA), 11.10g × g 10g'3g ±g 1.37g × g 10g'3g molg molg'1 over Australia (AUS), 6.80g × g 10g'3g ±g 0.44g × g 10g'3g molg molg'1 over India (IND), 5.80g × g 10g'3g ±g 0.15g × g 10g'3g molg molg'1 over Southeast Asia (SEA), 4.00g × g 10g'3g ±g 0.19g × g 10g'3g molg molg'1 over northern Africa (NAF), 5.00g × g 10g'3g ±g 0.13g × g 10g'3g molg molg'1 over southern Africa (SAF), and 4.40g × g 10g'3g ±g 0.09g × g 10g'3g molg molg'1 over Siberia (SIB), in a fair agreement with previous studies. In comparison with referenced emission ratios, it is also shown that the selected agricultural burning plumes captured by IASI over India and Southeast Asia correspond to recent plumes where the chemistry or the sink does not occur. An additional classification of the enhancement ratios by type of fuel burned is also provided, showing a diverse origin of the plumes sampled by IASI, especially over Amazonia and Siberia. The variability in the enhancement ratios by biome over the different regions show that the levels of HCOOH and CO do not only depend on the fuel types. © Author(s) 2017.
BibTeX:
@article{Pommier2017,
  author = {Pommier, M. and Clerbaux, C. and Coheur, P.-F.},
  title = {Determination of enhancement ratios of HCOOH relative to CO in biomass burning plumes by the Infrared Atmospheric Sounding Interferometer (IASI)},
  journal = {Atmospheric Chemistry and Physics},
  year = {2017},
  volume = {17},
  pages = {11089-11105},
  doi = {10.5194/acp-17-11089-2017}
}
Abstract: We analyze the ozone (O3) variability in the troposphere (from ground to 300 hPa) using 8 years (January 2008 to March 2016) of O3 profile measurements provided by the Infrared Atmospheric Sounding Interferometer (IASI) on board the MetOp satellite. The capability of IASI to monitor the year-to-year variability in that layer is examined first in terms of vertical sensitivity, a priori contribution, and correlations in the deseasonalized anomalies with the upper layers. We present global patterns of the main geophysical drivers (e.g., solar flux, Quasi-biennal Oscillation-QBO, North Atlantic Oscillation-NAO, and El Niño-Southern Oscillation-ENSO) of IASI O3 variations, obtained by applying appropriate annual and seasonal multivariate regression models on time series of spatially gridded averaged O3. The results show that the models are able to explain most of the O3 variability captured by IASI. Large O3 changes in the North Arctic/Euro-Atlantic sector and over the equatorial band are attributed to the NAO and the QBO effects, respectively. ENSO is modeled as the main contributor to the O3 variations in the tropical band where direct effects of warm and cool ENSO phases are highlighted with a clear tropical-extratropical gradient. A strong west-east gradient in the tropics is also found and likely reflects an indirect effect related to ENSO dry conditions. Finally, we also show that the ENSO perturbs the O3 variability far from the tropics into middle and high latitudes where a significant 4-month time-lag in the response of O3 to ENSO is identified for the first time. © 2017. American Geophysical Union. All Rights Reserved.
BibTeX:
@article{Wespes2017,
  author = {Wespes, C. and Hurtmans, D. and Clerbaux, C. and Coheur, P.-F.},
  title = {O3 variability in the troposphere as observed by IASI over 2008-2016: Contribution of atmospheric chemistry and dynamics},
  journal = {Journal of Geophysical Research},
  year = {2017},
  volume = {122},
  pages = {2429-2451},
  doi = {10.1002/2016JD025875}
}
Abstract: Vegetation fires are a major source of ammonia (NH3) in the atmosphere. Their emissions are mainly estimated using bottom-up approaches that rely on uncertain emission factors. In this study, we derive new biome-specific NH3 enhancement ratios relative to carbon monoxide (CO), ERNH3 / CO (directly related to the emission factors), from the measurements of the IASI sounder onboard the Metop-A satellite. This is achieved for large tropical regions and for an 8-year period (2008-2015). We find substantial differences in the ERNH3 / CO ratios between the biomes studied, with calculated values ranging from 7 × 10-3 to 23 × 10-3. For evergreen broadleaf forest these are typically 50-75% higher than for woody savanna and savanna biomes. This variability is attributed to differences in fuel types and size and is in line with previous studies. The analysis of the spatial and temporal distribution of the ERNH3 / CO ratio also reveals a (sometimes large) within-biome variability. On a regional level, woody savanna shows, for example, a mean ERNH3 / CO ratio for the region of Africa south of the Equator that is 40-75% lower than in the other five regions studied, probably reflecting regional differences in fuel type and burning conditions. The same variability is also observed on a yearly basis, with a peak in the ERNH3 / CO ratio observed for the year 2010 for all biomes. These results highlight the need for the development of dynamic emission factors that take into better account local variations in fuel type and fire conditions. We also compare the IASI-derived ERNH3 / CO ratio with values reported in the literature, usually calculated from ground-based or airborne measurements. We find general good agreement in the referenced ERNH3 / CO ratio except for cropland, for which the ERNH3 / CO ratio shows an underestimation of about 2-2.5 times. © 2017 Author(s).
BibTeX:
@article{Whitburn2017,
  author = {Whitburn, S. and Van Damme, M. and Clarisse, L. and Hurtmans, D. and Clerbaux, C. and Coheur, P.-F.},
  title = {IASI-derived NH3 enhancement ratios relative to CO for the tropical biomass burning regions},
  journal = {Atmospheric Chemistry and Physics},
  year = {2017},
  volume = {17},
  pages = {12239-12252},
  doi = {10.5194/acp-17-12239-2017}
}
Abstract: The vulnerability of the European airspace to volcanic eruptions was brought to the attention of the public and the scientific community by the 2010 eruptions of the Icelandic volcano Eyjafjallajökull. As a consequence of this event, ash concentration thresholds replaced the ĝ zero tolerance to ashĝ€ rule, drastically changing the requirements on satellite ash retrievals. In response to that, the ESA funded several projects aiming at creating an optimal end-to-end system for volcanic ash plume monitoring and prediction. Two of them, namely the SACS-2 and SMASH projects, developed and improved dedicated satellite-derived ash plume and sulfur dioxide level assessments. The validation of volcanic ash levels and height extracted from the GOME-2 and IASI instruments on board the MetOp-A satellite is presented in this work. EARLINET lidar measurements are compared to different satellite retrievals for two eruptive episodes in April and May 2010. Comparisons were also made between satellite retrievals and aircraft lidar data obtained with the UK's BAe-146-301 Atmospheric Research Aircraft (managed by the Facility for Airborne Atmospheric Measurements, FAAM) over the United Kingdom and the surrounding regions. The validation results are promising for most satellite products and are within the estimated uncertainties of each of the comparative data sets, but more collocation scenes would be desirable to perform a comprehensive statistical analysis. The satellite estimates and the validation data sets are better correlated for high ash optical depth values, with correlation coefficients greater than 0.8. The IASI retrievals show a better agreement concerning the ash optical depth and ash layer height when compared with the ground-based and airborne lidar data. © Author(s) 2016. CC Attribution 3.0 License.
BibTeX:
@article{Balis2016a,
  author = {Balis, D. and Koukouli, M.-E. and Siomos, N. and Dimopoulos, S. and Mona, L. and Pappalardo, G. and Marenco, F. and Clarisse, L. and J Ventress, L. and Carboni, E. and G Grainger, R. and Wang, P. and Tilstra, G. and Van Der A, R. and Theys, N. and Zehner, C.},
  title = {Validation of ash optical depth and layer height retrieved from passive satellite sensors using EARLINET and airborne lidar data: the case of the Eyjafjallajökull eruption},
  journal = {Atmospheric Chemistry and Physics},
  year = {2016},
  volume = {16},
  pages = {5705-5720},
  doi = {10.5194/acp-16-5705-2016}
}
Abstract: The 2010 eruptions of the Icelandic volcano Eyjafjallajokull attracted the attention of the public and the scientific community to the vulnerability of the European airspace to volcanic eruptions. The European Space Agency project "Satellite Monitoring of Ash and Sulphur Dioxide for the mitigation of Aviation Hazards", called for the creation of an optimal End-to-End System for Volcanic Ash Plume Monitoring and Prediction. This system is based on improved and dedicated satellite-derived ash plume and sulphur dioxide level assessments, as well as an extensive validation, using among others ground-based measurements (Koukouli et al., 2014). The validation of volcanic ash levels and height extracted from IASI/MetopA is presented in this work with emphasis on the ash plume height and ash optical depth levels. European Aerosol Research Lidar Network [EARLINET] lidar measurements are compared to different satellite estimates for two eruptive episodes. The validation results are extremely promising within the estimated uncertainties of each of the comparative datasets. © 2016 Owned by the authors, published by EDP Sciences.
BibTeX:
@conference{Balis2016,
  author = {Balis, D. and Siomos, N. and Koukouli, M. and Clarisse, L. and Carboni, E. and Ventress, L. and Grainger, R. and Mona, L. and Pappalardo, G.},
  title = {Validation of ASH Optical Depth and Layer Height from IASI using Earlinet Lidar Data},
  journal = {EPJ Web of Conferences},
  year = {2016},
  volume = {119},
  article number = {07006},
  doi = {10.1051/epjconf/201611907006}
}
Abstract: SO2 from volcanic eruptions is now operationally monitored from space in both the ultraviolet (UV) and thermal infrared (TIR) spectral range, but anthropogenic SO2 has almost solely been measured from UV sounders. Indeed, TIR instruments are well known to have a poor sensitivity to the planetary boundary layer (PBL), due to generally low thermal contrast (TC) between the ground and the air above it. Recent studies have demonstrated the capability of the Infrared Atmospheric Sounding Interferometer (IASI) to measure near-surface SO2 locally, for specific atmospheric conditions. In this work, we develop a retrieval method allowing the inference of SO2 near-surface concentrations from IASI measurements at a global scale. This method consists of two steps. Both are based on the computation of radiance indexes representing the strength of the SO2 ν3 band in IASI spectra. The first step allows the peak altitude of SO2 to be retrieved and near-surface SO2 to be selected. In the second step, 0-4 km columns of SO2 are inferred using a look-up table (LUT) approach. Using this new retrieval method, we obtain the first global distribution of near-surface SO2 from IASI-A, and identify the dominant anthropogenic hotspot sources and volcanic degassing. The 7-year daily time evolution of SO2 columns above two industrial source areas (Beijing in China and Sar Cheshmeh in Iran) is investigated and correlated to the seasonal variations of the parameters that drive the IASI sensitivity to the PBL composition. Apart from TC, we show that humidity is the most important parameter which determines IR sensitivity to nearsurface SO2 in the ν3 band. As IASI provides global measurements twice daily, the differences between the retrieved columns for the morning and evening orbits are investigated. This paper finally presents a first intercomparison of the measured 0-4 km columns with an independent iterative retrieval method and with observations of the Ozone Monitoring Instrument (OMI). © Author(s) 2016.
BibTeX:
@article{Bauduin2016,
  author = {Bauduin, S. and Clarisse, L. and Hadji-Lazaro, J. and Theys, N. and Clerbaux, C. and Coheur, P.-F.},
  title = {Retrieval of near-surface sulfur dioxide (SO2) concentrations at a global scale using IASI satellite observations},
  journal = {Atmospheric Measurement Techniques},
  year = {2016},
  volume = {9},
  pages = {721-740},
  doi = {10.5194/amt-9-721-2016}
}
Abstract: The 2014-2015 Holuhraun lava-flood eruption of Bároarbunga volcano (Iceland) emitted prodigious amounts of sulfur dioxide into the atmosphere. This eruption caused a large-scale episode of air pollution throughout Western Europe in September 2014, the first event of this magnitude recorded in the modern era. We gathered chemistry-transport simulations and a wealth of complementary observations from satellite sensors (OMI, IASI), ground-based remote sensing (lidar, sunphotometry, differential optical absorption spectroscopy) and ground-level air quality monitoring networks to characterize both the spatial-temporal distributions of volcanic SO2 and sulfate aerosols as well as the dynamics of the planetary boundary layer. Time variations of dynamical and microphysical properties of sulfate aerosols in the aged low-tropospheric volcanic cloud, including loading, vertical distribution, size distribution and single scattering albedo, are provided. Retrospective chemistry-transport simulations at low horizontal resolution (25 km × 25 km) capture the correct temporal dynamics of this far-range air pollution event but fail to reproduce the correct magnitude of SO2 concentration at ground-level. Simulations at higher spatial resolution, relying on two nested domains with finest resolution of 7.3 km × 7.3 km, improve substantially the far-range vertical distribution of the volcanic cloud and subsequently the description of ground-level SO2 concentrations. However, remaining discrepancies between model and observations are shown to result from an inaccurate representation of the planetary boundary layer (PBL) dynamics. Comparison with lidar observations points out a systematic under-estimation of the PBL height by the model, whichever the PBL parameterization scheme. Such a shortcoming impedes the capture of the overlying Bároarbunga cloud into the PBL at the right time and in sufficient quantities. This study therefore demonstrates the key role played by the PBL dynamics in accurately modelling large-scale volcanogenic air pollution. © 2016 Author(s).
BibTeX:
@article{Boichu2016,
  author = {Boichu, M. and Chiapello, I. and Brogniez, C. and Péré, J.-C. and Thieuleux, F. and Torres, B. and Blarel, L. and Mortier, A. and Podvin, T. and Goloub, P. and Söhne, N. and Clarisse, L. and Bauduin, S. and Hendrick, F. and Theys, N. and Van Roozendael, M. and Tanré, D.},
  title = {Current challenges in modelling far-range air pollution induced by the 2014-2015 Bároarbunga fissure eruption (Iceland)},
  journal = {Atmospheric Chemistry and Physics},
  year = {2016},
  volume = {16},
  pages = {10831-10845},
  doi = {10.5194/acp-16-10831-2016}
}
Abstract: This paper presents an extensive intercomparison and validation for the ozone (O3) product measured by the two Infrared Atmospheric Sounding Interferometers (IASIs) launched on board the MetOp-A and MetOp-B satellites in 2006 and in 2012 respectively. IASI O3 total columns and vertical profiles obtained from Fast Optimal Retrievals on Layers for IASI (FORLI) v20140922 software (running up until recently) are validated against independent observations during the period 2008-2014 on a global scale. On average for the period 2013-2014, IASI-A and IASI-B total ozone columns (TOCs) retrieved using FORLI are consistent, with IASI-B providing slightly lower values with a global difference of only 0.2±0.8%. The comparison between IASI-A and IASI-B O3 vertical profiles shows differences within ±2% over the entire altitude range. Global validation results for 7 years of IASI TOCs from FORLI against the Global Ozone Monitoring Experiment-2 (GOME-2) launched on board MetOp-A and Brewer-Dobson data show that, on average, IASI overestimates the ultraviolet (UV) data by 5-6% with the largest differences found in the southern high latitudes. The comparison with UV-visible SAOZ (Système d'Analyse par Observation Zénithale) measurements shows a mean bias between IASI and SAOZ TOCs of 2-4% in the midlatitudes and tropics and 7% at the polar circle. Part of the discrepancies found at high latitudes can be attributed to the limited information content in the observations due to low brightness temperatures. The comparison with ozonesonde vertical profiles (limited to 30km) shows that on average IASI with FORLI processing underestimates O3 by ∼ 5-15% in the troposphere while it overestimates O3 by ∼ 10-40% in the stratosphere, depending on the latitude. The largest relative differences are found in the tropical tropopause region; this can be explained by the low O3 amounts leading to large relative errors. In this study, we also evaluate an updated version of FORLI-O3 retrieval software (v20151001), using look-up tables recalculated to cover a larger spectral range using the latest HITRAN spectroscopic database (HITRAN 2012) and implementing numerical corrections. The assessment of the new O3 product with the same set of observations as that used for the validation exercise shows a correction of ∼ 4% for the TOC positive bias when compared to the UV ground-based and satellite observations, bringing the overall global comparison to ∼ 1-2% on average. This improvement is mainly associated with a decrease in the retrieved O3 concentration in the middle stratosphere (above 30hPa/25km) as shown by the comparison with ozonesonde data. © Author(s) 2016.
BibTeX:
@article{Boynard2016,
  author = {Boynard, A. and Hurtmans, D. and Koukouli, M.E. and Goutail, F. and Bureau, J. and Safieddine, S. and Lerot, C. and Hadji-Lazaro, J. and Wespes, C. and Pommereau, J.-P. and Pazmino, A. and Zyrichidou, I. and Balis, D. and Barbe, A. and Mikhailenko, S.N. and Loyola, D. and Valks, P. and Van Roozendael, M. and Coheur, P.-F. and Clerbaux, C.},
  title = {Seven years of IASI ozone retrievals from FORLI: Validation with independent total column and vertical profile measurements},
  journal = {Atmospheric Measurement Techniques},
  year = {2016},
  volume = {9},
  pages = {4327-4353},
  doi = {10.5194/amt-9-4327-2016}
}
Abstract: Satellite instruments have been providing measurements of global volcanic emissions of sulfur dioxide (SO2) since 1978, based on observations in the ultraviolet (UV), infrared (IR) and microwave spectral bands. We review recent advances in satellite remote sensing of volcanic gases, focusing on increased instrument sensitivity to tropospheric SO2 emissions and techniques to determine volcanic plume altitude. A synthesis of  36 years of global UV, IR and microwave satellite measurements yields an updated assessment of the volcanic SO2 flux to the upper troposphere and lower stratosphere (UTLS) between 1978 and 2014 ( 1-Tg/yr). The present availability of multiple UV and IR satellite SO2 products provides increased confidence in calculated SO2 loadings for many eruptions. We examine the temporal and latitudinal distribution of volcanic SO2 emissions and reassess the relationship between eruptive SO2 discharge and eruption magnitude, finding a first-order correlation between SO2 emission and volcanic explosivity index (VEI), but with significant scatter. Based on the observed SO2-VEI relation, we estimate the fraction of eruptive SO2 emissions released by the smallest eruptions ( 0.48 Tg/yr), which is not recorded by satellite observations. A detailed breakdown of the sources of measured SO2 emissions reveals intuitively expected correlations between eruption frequency, SO2 loading and volcanic degassing style. We discuss new constraints on e-folding times for SO2 removal in volcanic plumes, and highlight recent measurements of volcanic hydrogen chloride (HCl) injections into the UTLS. An analysis of passive volcanic emissions of SO2 detected in Ozone Monitoring Instrument (OMI) SO2 data since 2004 provides new insight into the location and stability of the dominant sources of volcanic SO2 over the past decade. Since volcanic SO2 emissions constitute a random, highly variable perturbation to the atmosphere-climate system, continued monitoring of volcanic SO2 emissions from space by multiple UV and IR instruments to extend the current multi-decadal record is essential, and near-global, geostationary measurements of SO2 may be available by the end of the current decade. © 2016 The Authors.
BibTeX:
@article{Carn2016,
  author = {Carn, S.A. and Clarisse, L. and Prata, A.J.},
  title = {Multi-decadal satellite measurements of global volcanic degassing},
  journal = {Journal of Volcanology and Geothermal Research},
  year = {2016},
  volume = {311},
  pages = {99-134},
  doi = {10.1016/j.jvolgeores.2016.01.002}
}
Abstract: In the first part of this chapter, the spectral content of the thermal infrared spectral region for the sounding of volcanic eruptions is explored through analysis of simulated and real observed spectra. Next, we review the literature on algorithms for the identification and retrieval of volcanic ash, both from broadband and hyperspectral infrared measurements. The final part of this chapter treats the topic of validation of satellite-based ash retrievals. © 2016 Elsevier Ltd. All rights reserved.
BibTeX:
@book{Clarisse2016,
  author = {Clarisse, L. and Prata, F.},
  title = {Infrared Sounding of Volcanic Ash},
  journal = {Volcanic Ash: Hazard Observation},
  year = {2016},
  pages = {189-215},
  doi = {10.1016/B978-0-08-100405-0.00017-3}
}
Abstract: Global distributions of atmospheric ammonia (NH3) measured with satellite instruments such as the Infrared Atmospheric Sounding Interferometer (IASI) contain valuable information on NH3 concentrations and variability in regions not yet covered by ground-based instruments. Due to their large spatial coverage and (bi-)daily overpasses, the satellite observations have the potential to increase our knowledge of the distribution of NH3 emissions and associated seasonal cycles. However the observations remain poorly validated, with only a handful of available studies often using only surface measurements without any vertical information. In this study, we present the first validation of the IASI-NH3 product using ground-based Fourier transform infrared spectroscopy (FTIR) observations. Using a recently developed consistent retrieval strategy, NH3 concentration profiles have been retrieved using observations from nine Network for the Detection of Atmospheric Composition Change (NDACC) stations around the world between 2008 and 2015. We demonstrate the importance of strict spatio-temporal collocation criteria for the comparison. Large differences in the regression results are observed for changing intervals of spatial criteria, mostly due to terrain characteristics and the short lifetime of NH3 in the atmosphere. The seasonal variations of both datasets are consistent for most sites. Correlations are found to be high at sites in areas with considerable NH3 levels, whereas correlations are lower at sites with low atmospheric NH3 levels close to the detection limit of the IASI instrument. A combination of the observations from all sites (<i>N</i>obs Combining double low line 547) give a mean relative difference of ĝ'32.4ĝ€±ĝ€(56.3)ĝ€%, a correlation <i>r</i> of 0.8 with a slope of 0.73. These results give an improved estimate of the IASI-NH3 product performance compared to the previous upper-bound estimates (-50 to +100%). © Author(s) 2016.
BibTeX:
@article{Dammers2016,
  author = {Dammers, E. and Palm, M. and Van Damme, M. and Vigouroux, C. and Smale, D. and Conway, S. and Toon, G.C. and Jones, N. and Nussbaumer, E. and Warneke, T. and Petri, C. and Clarisse, L. and Clerbaux, C. and Hermans, C. and Lutsch, E. and Strong, K. and Hannigan, J.W. and Nakajima, H. and Morino, I. and Herrera, B. and Stremme, W. and Grutter, M. and Schaap, M. and Kruit, R.J.W. and Notholt, J. and Coheur, P.-F. and Erisman, J.W.},
  title = {An evaluation of IASI-NH3 with ground-based Fourier transform infrared spectroscopy measurements},
  journal = {Atmospheric Chemistry and Physics},
  year = {2016},
  volume = {16},
  pages = {10351-10368},
  doi = {10.5194/acp-16-10351-2016}
}
Abstract: Ammonia (NH3), whose main source in the troposphere is agriculture, is an important gaseous precursor of atmospheric particulate matter (PM). We derived daily ammonia emissions using NH3 total columns measured from the Infrared Atmospheric Sounding Interferometer (IASI) on board Metop-A, at a relatively high spatial resolution (grid cell of 0.5° × 0.5°). During the European spring haze episodes of 24–31 March 2012 and 8–15 March 2014, IASI reveals NH3 total column magnitudes highlighting higher NH3 emissions over central Europe (especially over Germany, Czech Republic, and eastern France) from the ones provided by the European reference European Monitoring and Evaluation Programme inventory. These ammonia emissions exhibit in addition a large day-to-day variability, certainly due to spreading practices. The increase of NH3 emissions in the model, that reaches +300% locally, leads to an increase of both NH3 and PM2.5 surface concentrations and allows for a better comparison with independent measurements (in terms of bias, root-mean-square error, and correlation). This study suggests that there are good prospects for better quantifying NH3 emissions by atmospheric inversions. ©2016. American Geophysical Union. All Rights Reserved.
BibTeX:
@article{Fortems-Cheiney2016,
  author = {Fortems-Cheiney, A. and Dufour, G. and Hamaoui-Laguel, L. and Foret, G. and Siour, G. and Van Damme, M. and Meleux, F. and Coheur, P.-F. and Clerbaux, C. and Clarisse, L. and Favez, O. and Wallasch, M. and Beekmann, M.},
  title = {Unaccounted variability in NH3 agricultural sources detected by IASI contributing to European spring haze episode},
  journal = {Geophysical Research Letters},
  year = {2016},
  volume = {43},
  pages = {5475-5482},
  doi = {10.1002/2016GL069361}
}
Abstract: Interest in stratospheric aerosol and its role in climate have increased over the last decade due to the observed increase in stratospheric aerosol since 2000 and the potential for changes in the sulfur cycle induced by climate change. This review provides an overview about the advances in stratospheric aerosol research since the last comprehensive assessment of stratospheric aerosol was published in 2006. A crucial development since 2006 is the substantial improvement in the agreement between in situ and space-based inferences of stratospheric aerosol properties during volcanically quiescent periods. Furthermore, new measurement systems and techniques, both in situ and space based, have been developed for measuring physical aerosol properties with greater accuracy and for characterizing aerosol composition. However, these changes induce challenges to constructing a long-term stratospheric aerosol climatology. Currently, changes in stratospheric aerosol levels less than 20% cannot be confidently quantified. The volcanic signals tend to mask any nonvolcanically driven change, making them difficult to understand. While the role of carbonyl sulfide as a substantial and relatively constant source of stratospheric sulfur has been confirmed by new observations and model simulations, large uncertainties remain with respect to the contribution from anthropogenic sulfur dioxide emissions. New evidence has been provided that stratospheric aerosol can also contain small amounts of nonsulfate matter such as black carbon and organics. Chemistry-climate models have substantially increased in quantity and sophistication. In many models the implementation of stratospheric aerosol processes is coupled to radiation and/or stratospheric chemistry modules to account for relevant feedback processes. ©2016. American Geophysical Union. All Rights Reserved.
BibTeX:
@article{Kremser2016,
  author = {Kremser, S. and Thomason, L.W. and von Hobe, M. and Hermann, M. and Deshler, T. and Timmreck, C. and Toohey, M. and Stenke, A. and Schwarz, J.P. and Weigel, R. and Fueglistaler, S. and Prata, F.J. and Vernier, J.-P. and Schlager, H. and Barnes, J.E. and Antuña-Marrero, J.-C. and Fairlie, D. and Palm, M. and Mahieu, E. and Notholt, J. and Rex, M. and Bingen, C. and Vanhellemont, F. and Bourassa, A. and Plane, J.M.C. and Klocke, D. and Carn, S.A. and Clarisse, L. and Trickl, T. and Neely, R. and James, A.D. and Rieger, L. and Wilson, J.C. and Meland, B.},
  title = {Stratospheric aerosol—Observations, processes, and impact on climate},
  journal = {Reviews of Geophysics},
  year = {2016},
  volume = {54},
  pages = {278-335},
  doi = {10.1002/2015RG000511}
}
Abstract: Formic acid (HCOOH) is one of the most abundant volatile organic compounds in the atmosphere. It is a major contributor to rain acidity in remote areas. There are, however, large uncertainties on the sources and sinks of HCOOH and therefore HCOOH is misrepresented by global chemistry-transport models. This work presents global distributions from 2008 to 2014 as derived from the measurements of the Infrared Atmospheric Sounding Interferometer (IASI), based on conversion factors between brightness temperature differences and representative retrieved total columns over seven regions: Northern Africa, southern Africa, Amazonia, Atlantic, Australia, Pacific, and Russia. The dependence of the measured HCOOH signal on the thermal contrast is taken into account in the conversion method. This conversion presents errors lower than 20% for total columns ranging between 0.5 and 1×1016 molec cm-2 but reaches higher values, up to 78 %, for columns that are lower than 0:3×1016 molec cm-2. Signatures from biomass burning events are highlighted, such as in the Southern Hemisphere and in Russia, as well as biogenic emission sources, e.g., over the eastern USA. A comparison between 2008 and 2014 with ground-based Fourier transform infrared spectroscopy (FTIR) measurements obtained at four locations (Maido and Saint-Denis at La Réunion, Jungfraujoch, and Wollongong) is shown. Although IASI columns are found to correlate well with FTIR data, a large bias (> 100 %) is found over the two sites at La Réunion. A better agreement is found at Wollongong with a negligible bias. The comparison also highlights the difficulty of retrieving total columns from IASI measurements over mountainous regions such as Jungfraujoch. A comparison of the retrieved columns with the global chemistry-transport model IMAGESv2 is also presented, showing good representation of the seasonal and interannual cycles over America, Australia, Asia, and Siberia. A global model underestimation of the distribution and a misrepresentation of the seasonal cycle over India are also found. A small positive trend in the IASI columns is observed over Australia, Amazonia, and India over the 2008-2014 period (from 0.7 to 1.5%year-1), while a decrease of ∼0.8% year-1 is measured over Siberia. © Author(s) 2016.
BibTeX:
@article{Pommier2016,
  author = {Pommier, M. and Clerbaux, C. and Coheur, P.-F. and Mahieu, E. and Müller, J.-F. and Paton-Walsh, C. and Stavrakou, T. and Vigouroux, C.},
  title = {HCOOH distributions from IASI for 2008-2014: Comparison with ground-based FTIR measurements and a global chemistry-transport model},
  journal = {Atmospheric Chemistry and Physics},
  year = {2016},
  volume = {16},
  pages = {8963-8981},
  doi = {10.5194/acp-16-8963-2016}
}
Abstract: Producing a global and comprehensive description of atmospheric aerosols requires integration of ground-based, airborne, satellite and model datasets. Due to its complexity, aerosol monitoring requires the use of several data records with complementary information content. This paper describes the lessons learned while developing and qualifying algorithms to generate aerosol Climate Data Records (CDR) within the European Space Agency (ESA) Aerosol_cci project. An iterative algorithm development and evaluation cycle involving core users is applied. It begins with the application-specific refinement of user requirements, leading to algorithm development, dataset processing and independent validation followed by user evaluation. This cycle is demonstrated for a CDR of total Aerosol Optical Depth (AOD) from two subsequent dual-view radiometers. Specific aspects of its applicability to other aerosol algorithms are illustrated with four complementary aerosol datasets. An important element in the development of aerosol CDRs is the inclusion of several algorithms evaluating the same data to benefit from various solutions to the ill-determined retrieval problem. The iterative approach has produced a 17-year AOD CDR, a 10-year stratospheric extinction profile CDR and a 35-year Absorbing Aerosol Index record. Further evolution cycles have been initiated for complementary datasets to provide insight into aerosol properties (i.e., dust aerosol, aerosol absorption). © 2016 by the authors.
BibTeX:
@article{Popp2016,
  author = {Popp, T. and De Leeuw, G. and Bingen, C. and Brühl, C. and Capelle, V. and Chedin, A. and Clarisse, L. and Dubovik, O. and Grainger, R. and Griesfeller, J. and Heckel, A. and Kinne, S. and Klüser, L. and Kosmale, M. and Kolmonen, P. and Lelli, L. and Litvinov, P. and Mei, L. and North, P. and Pinnock, S. and Povey, A. and Robert, C. and Schulz, M. and Sogacheva, L. and Stebel, K. and Zweers, D.S. and Thomas, G. and Tilstra, L.G. and Vandenbussche, S. and Veefkind, P. and Vountas, M. and Xue, Y.},
  title = {Development, production and evaluation of aerosol climate data records from European satellite observations (Aerosol_cci)},
  journal = {Remote Sensing},
  year = {2016},
  volume = {8},
  article number = {421},
  doi = {10.3390/rs8050421}
}
BibTeX:
@article{Predoi-Cross2016,
  author = {Predoi-Cross, A. and Unni, A.V. and Liu, W. and Schofield, I. and Holladay, C. and McKellar, A.R.W. and Hurtmans, D.},
  title = {Corrigendum to "Line shape parameters measurement and computations for self-broadened carbon dioxide transitions in the 30012 ← 00001 and 30013 ← 00001 bands, line mixing, and speed dependence" [J. Mol. Spectrosc. 245 (2007) 34-51]},
  journal = {Journal of Molecular Spectroscopy},
  year = {2016},
  volume = {322},
  pages = {55},
  doi = {10.1016/j.jms.2015.11.005}
}
Abstract: The ability of seven state-of-the-art chemistry-aerosol models to reproduce distributions of tropospheric ozone and its precursors, as well as aerosols over eastern Asia in summer 2008, is evaluated. The study focuses on the performance of models used to assess impacts of pollutants on climate and air quality as part of the EU ECLIPSE project. Models, run using the same ECLIPSE emissions, are compared over different spatial scales to in situ surface, vertical profiles and satellite data. Several rather clear biases are found between model results and observations, including overestimation of ozone at rural locations downwind of the main emission regions in China, as well as downwind over the Pacific. Several models produce too much ozone over polluted regions, which is then transported downwind. Analysis points to different factors related to the ability of models to simulate VOC-limited regimes over polluted regions and NOx limited regimes downwind. This may also be linked to biases compared to satellite NO2, indicating overestimation of NO2 over and to the north of the northern China Plain emission region. On the other hand, model NO2 is too low to the south and west of this region and over South Korea/Japan. Overestimation of ozone is linked to systematic underestimation of CO particularly at rural sites and downwind of the main Chinese emission regions. This is likely to be due to enhanced destruction of CO by OH. Overestimation of Asian ozone and its transport downwind implies that radiative forcing from this source may be overestimated. Model-observation discrepancies over Beijing do not appear to be due to emission controls linked to the Olympic Games in summer 2008.

With regard to aerosols, most models reproduce the satellite-derived AOD patterns over eastern China. Our study nevertheless reveals an overestimation of ECLIPSE model mean surface BC and sulphate aerosols in urban China in summer 2008. The effect of the short-term emission mitigation in Beijing is too weak to explain the differences between the models. Our results rather point to an overestimation of SO2 emissions, in particular, close to the surface in Chinese urban areas. However, we also identify a clear underestimation of aerosol concentrations over northern India, suggesting that the rapid recent growth of emissions in India, as well as their spatial extension, is underestimated in emission inventories. Model deficiencies in the representation of pollution accumulation due to the Indian monsoon may also be playing a role. Comparison with vertical aerosol lidar measurements highlights a general underestimation of scattering aerosols in the boundary layer associated with overestimation in the free troposphere pointing to modelled aerosol lifetimes that are too long. This is likely linked to too strong vertical transport and/or insufficient deposition efficiency during transport or export from the boundary layer, rather than chemical processing (in the case of sulphate aerosols). Underestimation of sulphate in the boundary layer implies potentially large errors in simulated aerosol-cloud interactions, via impacts on boundary-layer clouds.

This evaluation has important implications for accurate assessment of air pollutants on regional air quality and global climate based on global model calculations. Ideally, models should be run at higher resolution over source regions to better simulate urban-rural pollutant gradients and/or chemical regimes, and also to better resolve pollutant processing and loss by wet deposition as well as vertical transport. Discrepancies in vertical distributions require further quantification and improvement since these are a key factor in the determination of radiative forcing from short-lived pollutants.
BibTeX:
@article{Quennehen2016,
  author = {Quennehen, B. and Raut, J.-C. and Law, K.S. and Daskalakis, N. and Ancellet, G. and Clerbaux, C. and Kim, S.-W. and Lund, M.T. and Myhre, G. and Olivié, D.J.L. and Safieddine, S. and Skeie, R.B. and Thomas, J.L. and Tsyro, S. and Bazureau, A. and Bellouin, N. and Hu, M. and Kanakidou, M. and Klimont, Z. and Kupiainen, K. and Myriokefalitakis, S. and Quaas, J. and Rumbold, S.T. and Schulz, M. and Cherian, R. and Shimizu, A. and Wang, J. and Yoon, S.-C. and Zhu, T.},
  title = {Multi-model evaluation of short-lived pollutant distributions over east Asia during summer 2008},
  journal = {Atmospheric Chemistry and Physics},
  year = {2016},
  volume = {16},
  pages = {10765-10792},
  doi = {10.5194/acp-16-10765-2016}
}
Abstract: Knowing the spatial and seasonal distributions of nitric acid (HNO3/ around the globe is of great interest and allows us to comprehend the processes regulating stratospheric ozone, especially in the polar regions. Due to its unprecedented spatial and temporal sampling, the nadir-viewing Infrared Atmospheric Sounding Interferometer (IASI) is capable of sounding the atmosphere twice a day globally, with good spectral resolution and low noise. With the Fast Optimal Retrievals on Layers for IASI (FORLI) algorithm, we are retrieving, in near real time, columns as well as vertical profiles of several atmospheric species, among which is HNO3. We present in this paper the first characterization of the FORLI-HNO3 profile products, in terms of vertical sensitivity and error budgets. We show that the sensitivity of IASI to HNO3 is highest in the lower stratosphere (10-20 km), where the largest amounts of HNO3 are found, but that the vertical sensitivity of IASI only allows one level of information on the profile (degrees of freedom for signal, DOFS; ∼1). The sensitivity near the surface is negligible in most cases, and for this reason, a partial column (5-35 km) is used for the analyses. Both vertical profiles and partial columns are compared to FTIR ground-based measurements from the Network for the Detection of Atmospheric Composition Change (NDACC) to characterize the accuracy and precision of the FORLI-HNO3 product. The profile validation is conducted through the smoothing of the raw FTIR profiles by the IASI averaging kernels and gives good results, with a slight overestimation of IASI measurements in the upper troposphere/lower stratosphere (UTLS) at the six chosen stations (Thule, Kiruna, Jungfraujoch, Izaña, Lauder and Arrival Heights). The validation of the partial columns (5-35 km) is also conclusive with a mean correlation of 0.93 between IASI and the FTIR measurements. An initial survey of the HNO3 spatial and seasonal variabilities obtained from IASI measurements for a 1-year (2011) data set shows that the expected latitudinal gradient of concentrations from low to high latitudes and the large seasonal variability in polar regions (cycle amplitude around 30% of the seasonal signal, peak to peak) are well represented by IASI data. © Author(s) 2016.
BibTeX:
@article{Ronsmans2016,
  author = {Ronsmans, G. and Langerock, B. and Wespes, C. and Hannigan, J.W. and Hase, F. and Kerzenmacher, T. and Mahieu, E. and Schneider, M. and Smale, D. and Hurtmans, D. and De Mazière, M. and Clerbaux, C. and Coheur, P.-F.},
  title = {First characterization and validation of FORLI-HNO3 vertical profiles retrieved from IASI/Metop},
  journal = {Atmospheric Measurement Techniques},
  year = {2016},
  volume = {9},
  pages = {4783-4801},
  doi = {10.5194/amt-9-4783-2016}
}
Abstract: Satellite measurements from the thermal Infrared Atmospheric Sounding Interferometer (IASI), aircraft data from the MOZAIC/IAGOS project, as well as observations from ground-based stations, are used to assess the tropospheric ozone (O3) variability during the East Asian Summer Monsoon (EASM). Six years 2008-2013 of IASI data analysis reveals the ability of the instrument to detect the onset and the progression of the monsoon seen by a decrease in the tropospheric 0-6km O3 column due to the EASM, and to reproduce this decrease from one year to the other. The year-to-year variability is found to be mainly dependent on meteorology. Focusing on the period of May-August 2011, taken as an example year, IASI data show clear inverse relationship between tropospheric 0-6km O3 on one hand and meteorological parameters such as cloud cover, relative humidity and wind speed, on the other hand. Aircraft data from the MOZAIC/IAGOS project for the EASM of 2008-2013 are used to validate the IASI data and to assess the effect of the monsoon on the vertical distribution of the tropospheric O3 at different locations. Results show good agreement with a correlation coefficient of 0.73 (12%) between the 0-6km O3 column derived from IASI and aircraft data. IASI captures very well the inter-annual variation of tropospheric O3 observed by the aircraft data over the studied domain. Analysis of vertical profiles of the aircraft data shows a decrease in the tropospheric O3 that is more important in the free troposphere than in the boundary layer and at 10-20°N than elsewhere. Ground station data at different locations in India and China show a spatiotemporal dependence on meteorology during the monsoon, with a decrease up to 22ppbv in Hyderabad, and up to 5ppbv in the North China Plain. © Author(s) 2016.
BibTeX:
@article{Safieddine2016,
  author = {Safieddine, S. and Boynard, A. and Hao, N. and Huang, F. and Wang, L. and Ji, D. and Barret, B. and Ghude, S.D. and Coheur, P.-F. and Hurtmans, D. and Clerbaux, C.},
  title = {Tropospheric ozone variability during the East Asian summer monsoon as observed by satellite (IASI), aircraft (MOZAIC) and ground stations},
  journal = {Atmospheric Chemistry and Physics},
  year = {2016},
  volume = {16},
  pages = {10489-10500},
  doi = {10.5194/acp-16-10489-2016}
}
Abstract: The variability of atmospheric ammonia (NH3), emitted largely from agricultural sources, is an important factor when considering how inorganic fine particulate matter (PM2.5) concentrations and nitrogen cycling are changing over the United States. This study combines new observations of ammonia concentration from the surface, aboard aircraft, and retrieved by satellite to both evaluate the simulation of ammonia in a chemical transport model (GEOS-Chem) and identify which processes control the variability of these concentrations over a 5-year period (2008-2012). We find that the model generally underrepresents the ammonia concentration near large source regions (by 26% at surface sites) and fails to reproduce the extent of interannual variability observed at the surface during the summer (JJA). Variability in the base simulation surface ammonia concentration is dominated by meteorology (64%) as compared to reductions in SO2 and NOx emissions imposed by regulation (32%) over this period. Introduction of year-to-year varying ammonia emissions based on animal population, fertilizer application, and meteorologically driven volatilization does not substantially improve the model comparison with observed ammonia concentrations, and these ammonia emissions changes have little effect on the simulated ammonia concentration variability compared to those caused by the variability of meteorology and acid-precursor emissions. There is also little effect on the PM2.5 concentration due to ammonia emissions variability in the summer when gas-phase changes are favored, but variability in wintertime emissions, as well as in early spring and late fall, will have a larger impact on PM2.5 formation. This work highlights the need for continued improvement in both satellite-based and in situ ammonia measurements to better constrain the magnitude and impacts of spatial and temporal variability in ammonia concentrations. © 2016 The Author(s).
BibTeX:
@article{Schiferl2016,
  author = {Schiferl, L.D. and Heald, C.L. and Damme, M.V. and Clarisse, L. and Clerbaux, C. and Coheur, P.F. and Nowak, J.B. and Neuman, J.A. and Herndon, S.C. and Roscioli, J.R. and Eilerman, S.J.},
  title = {Interannual variability of ammonia concentrations over the United States: Sources and implications},
  journal = {Atmospheric Chemistry and Physics},
  year = {2016},
  volume = {16},
  pages = {12305-12328},
  doi = {10.5194/acp-16-12305-2016}
}
Abstract: The large-scale burning of crop residues in the North China Plain (NCP), one of the most densely populated world regions, was recently recognized to cause severe air pollution and harmful health effects. A reliable quantification of the magnitude of these fires is needed to assess regional air quality. Here, we use an eight-year record (2005-2012) of formaldehyde measurements from space to constrain the emissions of volatile organic compounds (VOCs) in this region. Using inverse modelling, we derive that satellite-based post-harvest burning fluxes are, on average, at least a factor of 2 higher than state-of-the-art bottom-up statistical estimates, although with significant interannual variability. Crop burning is calculated to cause important increases in surface ozone (+7%) and fine aerosol concentrations (+18%) in the North China Plain in June. The impact of crop fires is also found in satellite observations of other species, glyoxal, nitrogen dioxide and methanol, and we show that those measurements validate the magnitude of the top-down fluxes. Our study indicates that the top-down crop burning fluxes of VOCs in June exceed by almost a factor of 2 the combined emissions from other anthropogenic activities in this region, underscoring the need for targeted actions towards changes in agricultural management practices. © 2016 The Author(s).
BibTeX:
@article{Stavrakou2016,
  author = {Stavrakou, T. and Müller, J.-F. and Bauwens, M. and De Smedt, I. and Lerot, C. and Van Roozendael, M. and Coheur, P.-F. and Clerbaux, C. and Boersma, K.F. and Van Der, A.R. and Song, Y.},
  title = {Substantial Underestimation of Post-Harvest Burning Emissions in the North China Plain Revealed by Multi-Species Space Observations},
  journal = {Scientific Reports},
  year = {2016},
  volume = {6},
  article number = {32307},
  doi = {10.1038/srep32307}
}
Abstract: This paper studies the seasonal variation of surface and column CO at three different sites (Paris, Jungfraujoch and Wollongong), with an emphasis on establishing a link between the CO vertical distribution and the nature of CO emission sources. We find the first evidence of a time lag between surface and free tropospheric CO seasonal variations in the Northern Hemisphere. The CO seasonal variability obtained from the total columns and free tropospheric partial columns shows a maximum around March-April and a minimum around September-October in the Northern Hemisphere (Paris and Jungfraujoch). In the Southern Hemisphere (Wollongong) this seasonal variability is shifted by about 6 months. Satellite observations by the IASI-MetOp (Infrared Atmospheric Sounding Interferometer) and MOPITT (Measurements Of Pollution In The Troposphere) instruments confirm this seasonality. Ground-based FTIR (Fourier transform infrared) measurements provide useful complementary information due to good sensitivity in the boundary layer. In situ surface measurements of CO volume mixing ratios at the Paris and Jungfraujoch sites reveal a time lag of the near-surface seasonal variability of about 2 months with respect to the total column variability at the same sites. The chemical transport model GEOS-Chem (Goddard Earth Observing System chemical transport model) is employed to interpret our observations. GEOS-Chem sensitivity runs identify the emission sources influencing the seasonal variation of CO. At both Paris and Jungfraujoch, the surface seasonality is mainly driven by anthropogenic emissions, while the total column seasonality is also controlled by air masses transported from distant sources. At Wollongong, where the CO seasonality is mainly affected by biomass burning, no time shift is observed between surface measurements and total column data. © Author(s) 2016. CC Attribution 3.0 License.
BibTeX:
@article{Te2016,
  author = {Té, Y. and Jeseck, P. and Franco, B. and Mahieu, E. and Jones, N. and Paton-Walsh, C. and Griffith, D.W.T. and Buchholz, R.R. and Hadji-Lazaro, J. and Hurtmans, D. and Janssen, C.},
  title = {Seasonal variability of surface and column carbon monoxide over the megacity Paris, high-altitude Jungfraujoch and Southern Hemispheric Wollongong stations},
  journal = {Atmospheric Chemistry and Physics},
  year = {2016},
  volume = {16},
  pages = {10911-10925},
  doi = {10.5194/acp-16-10911-2016}
}
Abstract: In this paper, we assess how daily ozone (O3) measurements from the Infrared Atmospheric Sounding Interferometer (IASI) on the MetOp-A platform can contribute to the analyses of the processes driving O3 variability in the troposphere and the stratosphere and, in the future, to the monitoring of long-term trends. The temporal evolution of O3 during the first 6 years of IASI (2008-2013) operation is investigated with multivariate regressions separately in four different layers (ground-300, 300-150, 150-25, 25-3ĝ€hPa), by adjusting to the daily time series averaged in 20° zonal bands, seasonal and linear trend terms along with important geophysical drivers of O3 variation (e.g. solar flux, quasi-biennial oscillation (QBO)). The regression model is shown to perform generally very well with a strong dominance of the annual harmonic terms and significant contributions from O3 drivers, in particular in the equatorial region where the QBO and the solar flux contribution dominate. More particularly, despite the short period of the IASI data set available up to now, two noticeable statistically significant apparent trends are inferred from the daily IASI measurements: a positive trend in the upper stratosphere (e.g. 1.74ĝ€±ĝ€0.77ĝ€DUĝ€yearĝ'1 between 30 and 50°ĝ€S), which is consistent with other studies suggesting a turnaround for stratospheric O3 recovery, and a negative trend in the troposphere at the mid-latitudes and high northern latitudes (e.g. ĝ'0.26ĝ€±ĝ€0.11ĝ€DUĝ€yearĝ'1 between 30 and 50°ĝ€N), especially during summer and probably linked to the impact of decreasing ozone precursor emissions. The impact of the high temporal sampling of IASI on the uncertainty in the determination of O3 trend has been further explored by performing multivariate regressions on IASI monthly averages and on ground-based Fourier transform infrared (FTIR) measurements. © Author(s) 2016. CC Attribution 3.0 License.
BibTeX:
@article{Wespes2016,
  author = {Wespes, C. and Hurtmans, D. and K Emmons, L. and Safieddine, S. and Clerbaux, C. and Edwards, D.P. and Coheur, P.-F.},
  title = {Ozone variability in the troposphere and the stratosphere from the first 6 years of IASI observations (2008-2013)},
  journal = {Atmospheric Chemistry and Physics},
  year = {2016},
  volume = {16},
  pages = {5721-5743},
  doi = {10.5194/acp-16-5721-2016}
}
Abstract: In this paper, we describe a new flexible and robust NH3 retrieval algorithm from measurements of the Infrared Atmospheric Sounding Interferometer (IASI). The method is based on the calculation of a spectral hyperspectral range index (HRI) and subsequent conversion to NH3 columns via a neural network. It is an extension of the method presented in Van Damme et al. (2014a) who used lookup tables (LUT) for the radiance-concentration conversion. The new method inherits the advantages of the LUT-based method while providing several significant improvements. These include the following: (1) Complete temperature and humidity vertical profiles can be accounted for. (2) Third-party NH3 vertical profile information can be used. (3) Reported positive biases of LUT retrieval are reduced, and finally (4) a full measurement uncertainty characterization is provided. A running theme in this study, related to item (2), is the importance of the assumed vertical NH3 profile. We demonstrate the advantages of allowing variable profile shapes in the retrieval. As an example, we analyze how the retrievals change when all NH3 is assumed to be confined to the boundary layer. We analyze different averaging procedures in use for NH3 in the literature, introduced to cope with the variable measurement sensitivity and derive global averaged distributions for the year 2013. A comparison with a GEOS-Chem modeled global distribution is also presented, showing a general good correspondence (within ±3×1015 molecules.cm-2) over most of the Northern Hemisphere. However, IASI finds mean columns about 1-1.5×1016 molecules.cm-2 (∼50-60%) lower than GEOS-Chem for India and the North China plain. © 2016. American Geophysical Union. All Rights Reserved.
BibTeX:
@article{Whitburn2016,
  author = {Whitburn, S. and Van Damme, M. and Clarisse, L. and Bauduin, S. and Heald, C.L. and Hadji-Lazaro, J. and Hurtmans, D. and Zondlo, M.A. and Clerbaux, C. and Coheur, P.-F.},
  title = {A flexible and robust neural network IASI-NH3 retrieval algorithm},
  journal = {Journal of Geophysical Research},
  year = {2016},
  volume = {121},
  pages = {6581-6599},
  doi = {10.1002/2016JD024828}
}
Abstract: Among the atmospheric emission sources, wildfires are episodic events characterized by large spatial and temporal variability. Therefore, accurate information on gaseous and aerosol emissions from fires for specific regions and seasons is critical for air quality forecasts. The Spinning Enhanced Visible and Infrared Imager (SEVIRI) in geostationary orbit provides fire observations over Africa and the Mediterranean with a temporal resolution of 15 min. It thus resolves the complete fire life cycle and captures the fires' peak intensities, which is not possible in Moderate Resolution Imaging Spectroradiometer (MODIS) fire emission inventories like the Global Fire Assimilation System (GFAS). We evaluate two different operational fire radiative power (FRP) products derived from SEVIRI, by studying a large forest fire in Antalya, Turkey, in July-August 2008. The EUMETSAT Land Surface Analysis Satellite Applications Facility (LSA SAF) has higher FRP values during the fire episode than the Wildfire Automated Biomass Burning Algorithm (WF-ABBA). It is also in better agreement with the co-located, gridded MODIS FRP. Both products miss small fires that frequently occur in the region and are detected by MODIS. Emissions are derived from the FRP products. They are used along-side GFAS emissions in smoke plume simulations with the Weather Research and Forecasting (WRF) model and the Community Multiscale Air Quality (CMAQ) model. In comparisons with MODIS aerosol optical thickness (AOT) and Infrared Atmospheric Sounding Interferometer (IASI), CO and NH3 observations show that including the diurnal variability of fire emissions improves the spatial distribution and peak concentrations of the simulated smoke plumes associated with this large fire. They also show a large discrepancy between the currently available operational FRP products, with the LSA SAF being the most appropriate. © Author(s) 2015.
BibTeX:
@article{Baldassarre2015,
  author = {Baldassarre, G. and Pozzoli, L. and Schmidt, C.C. and Unal, A. and Kindap, T. and Menzel, W.P. and Whitburn, S. and Coheur, P.-F. and Kavgaci, A. and Kaiser, J.W.},
  title = {Using SEVIRI fire observations to drive smoke plumes in the CMAQ air quality model: A case study over Antalya in 2008},
  journal = {Atmospheric Chemistry and Physics},
  year = {2015},
  volume = {15},
  pages = {8539-8558},
  doi = {10.5194/acp-15-8539-2015}
}
Abstract: We show the results and evaluation with independent measurements from assimilating both MOPITT (Measurements Of Pollution In The Troposphere) and IASI (Infrared Atmospheric Sounding Interferometer) retrieved profiles into the Community Earth System Model (CESM). We used the Data Assimilation Research Testbed ensemble Kalman filter technique, with the full atmospheric chemistry CESM component Community Atmospheric Model with Chemistry. We first discuss the methodology and evaluation of the current data assimilation system with coupled meteorology and chemistry data assimilation. The different capabilities of MOPITT and IASI retrievals are highlighted, with particular attention to instrument vertical sensitivity and coverage and how these impact the analyses. MOPITT and IASI CO retrievals mostly constrain the CO fields close to the main anthropogenic, biogenic, and biomass burning CO sources. In the case of IASI CO assimilation, we also observe constraints on CO far from the sources. During the simulation time period (June and July 2008), CO assimilation of both instruments strongly improves the atmospheric CO state as compared to independent observations, with the higher spatial coverage of IASI providing better results on the global scale. However, the enhanced sensitivity of multispectral MOPITT observations to near surface CO over the main source regions provides synergistic effects at regional scales. © 2015. American Geophysical Union. All Rights Reserved.
BibTeX:
@article{Barre2015,
  author = {Barré, J. and Gaubert, B. and Arellano, A.F.J. and Worden, H.M. and Edwards, D.P. and Deeter, M.N. and Anderson, J.L. and Raeder, K. and Collins, N. and Tilmes, S. and Francis, G. and Clerbaux, C. and Emmons, L.K. and Pfister, G.G. and Coheur, P.-F. and Hurtmans, D.},
  title = {Assessing the impacts of assimilating IASI and MOPITT CO retrievals using CESM-CAM-chem and DART},
  journal = {Journal of Geophysical Research},
  year = {2015},
  volume = {120},
  pages = {10501-10529},
  doi = {10.1002/2015JD023467}
}
Abstract: Sulfur-rich degassing, which is mostly composed of sulfur dioxide (SO2), plays a major role in the overall impact of volcanism on the atmosphere and climate. The accurate assessment of this impact is currently hampered by the poor knowledge of volcanic SO2 emissions. Here, using an inversion procedure, we show how assimilating snapshots of the volcanic SO2 load derived from the Infrared Atmospheric Sounding Interferometer (IASI) allows for reconstructing both the flux and altitude of the SO2 emissions with an hourly resolution. For this purpose, the regional chemistry-transport model CHIMERE is used to describe the dispersion of SO2 when released in the atmosphere. As proof of concept, we study the 10 April 2011 eruption of the Etna volcano (Italy), which represents one of the few volcanoes instrumented on the ground for the continuous monitoring of SO2 degassing. We find that the SO2 flux time-series retrieved from satellite imagery using the inverse scheme is in agreement with ground observations during ash-poor phases of the eruption. However, large discrepancies are observed during the ash-rich paroxysmal phase as a result of enhanced plume opacity affecting ground-based ultraviolet (UV) spectroscopic retrievals. As a consequence, the SO2 emission rate derived from the ground is underestimated by almost one order of magnitude. Altitudes of the SO2 emissions predicted by the inverse scheme are validated against an RGB image of the Moderate Resolution Imaging Spectroradiometer (MODIS) capturing the near-source atmospheric pathways followed by Etna plumes, in combination with forward trajectories from the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model. At a large distance from the source, modelled SO2 altitudes are compared with independent information on the volcanic cloud height. We find that the altitude predicted by the inverse scheme is in agreement with snapshots of the SO2 height retrieved from recent algorithms exploiting the high spectral resolution of IASI. The validity of the modelled SO2 altitude is further confirmed by the detection of a layer of particles at the same altitude by the spaceborne Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). Analysis of CALIOP colour and depolarization ratios suggests that these particles consist of sulfate aerosols formed from precursory volcanic SO2. The reconstruction of emission altitude, through inversion procedures which assimilate volcanic SO2 column amounts, requires specific meteorological conditions, especially sufficient wind shear so that gas parcels emitted at different altitudes follow distinct trajectories. We consequently explore the possibility and limits of assimilating in inverse schemes infrared (IR) imagery of the volcanic SO2 cloud altitude which will render the inversion procedure independent of the wind shear prerequisite. © Author(s) 2015.
BibTeX:
@article{Boichu2015,
  author = {Boichu, M. and Clarisse, L. and Péré, J.-C. and Herbin, H. and Goloub, P. and Thieuleux, F. and Ducos, F. and Clerbaux, C. and Tanré, D.},
  title = {Temporal variations of flux and altitude of sulfur dioxide emissions during volcanic eruptions: Implications for long-range dispersal of volcanic clouds},
  journal = {Atmospheric Chemistry and Physics},
  year = {2015},
  volume = {15},
  pages = {8381-8400},
  doi = {10.5194/acp-15-8381-2015}
}
Abstract: During 7-12 July 2012, extreme moist and warm conditions occurred over Greenland, leading to widespread surface melt. To investigate the physical processes during the atmospheric moisture transport of this event, we study the water vapor isotopic composition using surface in situ observations in Bermuda Island, South Greenland coast (Ivittuut), and northwest Greenland ice sheet (NEEM), as well as remote sensing observations (Infrared Atmospheric Sounding Interferometer (IASI) instrument on board MetOp-A), depicting propagation of similar surface and midtropospheric humidity and δD signals. Simulations using Lagrangian moisture source diagnostic and water tagging in a regional model showed that Greenland was affected by an atmospheric river transporting moisture from the western subtropical North Atlantic Ocean, which is coherent with observations of snow pit impurities deposited at NEEM. At Ivittuut, surface air temperature, humidity, and δD increases are observed. At NEEM, similar temperature increase is associated with a large and long-lasting  100‰δD enrichment and  15‰ deuterium excess decrease, thereby reaching Ivittuut level. We assess the simulation of this event in two isotope-enabled atmospheric general circulation models (LMDz-iso and ECHAM5-wiso). LMDz-iso correctly captures the timing of propagation for this event identified in IASI data but depict too gradual variations when compared to surface data. Both models reproduce the surface meteorological and isotopic values during the event but underestimate the background deuterium excess at NEEM. Cloud liquid water content parametrization in LMDz-iso poorly impacts the vapor isotopic composition. Our data demonstrate that during this atmospheric river event the deuterium excess signal is conserved from the moisture source to northwest Greenland. © 2015. American Geophysical Union. All Rights Reserved.
BibTeX:
@article{Bonne2015,
  author = {Bonne, J.-L. and Steen-Larsen, H.C. and Risi, C. and Werner, M. and Sodemann, H. and Lacour, J.-L. and Fettweis, X. and Cesana, G. and Delmotte, M. and Cattani, O. and Vallelonga, P. and Kjær, H.A. and Clerbaux, C. and Sveinbjörnsdóttir, Á.E. and Masson-Delmotte, V.},
  title = {The summer 2012 Greenland heat wave: In situ and remote sensing observations of water vapor isotopic composition during an atmospheric river event},
  journal = {Journal of Geophysical Research},
  year = {2015},
  volume = {120},
  pages = {2970-2989},
  doi = {10.1002/2014JD022602}
}
Abstract: The IASI mission flying onboard the MetOp satellites has been providing global observations of the air composition twice a day since 2007. From the atmospheric spectra recorded by the instruments in the thermal infrared spectral range, concentrations of a series of trace gases can be monitored, enhanced levels of pollution can be detected, and particle types can be determined to some extent. This paper recalls the historical context for the IASI remote sensor, reviews its capability to observe some key species for global and regional pollution monitoring, and reports on information services that benefit from the mission. © 2015 Academie des sciences
BibTeX:
@article{Clerbaux2015,
  author = {Clerbaux, C. and Hadji-Lazaro, J. and Turquety, S. and George, M. and Boynard, A. and Pommier, M. and Safieddine, S. and Coheur, P.-F. and Hurtmans, D. and Clarisse, L. and Van Damme, M.},
  title = {Tracking pollutants from space: Eight years of IASI satellite observation},
  journal = {Comptes Rendus - Geoscience},
  year = {2015},
  volume = {347},
  pages = {134-144},
  doi = {10.1016/j.crte.2015.06.001}
}
Abstract: We present a retrieval method for ammonia (NH3) total columns from ground-based Fourier transform infrared (FTIR) observations. Observations from Bremen (53.10° N, 8.85° E), Lauder (45.04° S, 169.68° E), Reúnion (20.9° S, 55.50° E) and Jungfraujoch (46.55° N, 7.98° E) were used to illustrate the capabilities of the method. NH3 mean total columns ranging 3 orders of magnitude were obtained, with higher values at Bremen (mean of 13.47 × 1015 molecules cm-2) and lower values at Jungfraujoch (mean of 0.18 × 1015 molecules cm-2). In conditions with high surface concentrations of ammonia, as in Bremen, it is possible to retrieve information on the vertical gradient, as two layers can be distinguished. The retrieval there is most sensitive to ammonia in the planetary boundary layer, where the trace gas concentration is highest. For conditions with low concentrations, only the total column can be retrieved. Combining the systematic and random errors we have a mean total error of 26 % for all spectra measured at Bremen (number of spectra (N)= 554), 30 % for all spectra from Lauder (N = 2412), 25 % for spectra from Reúnion (N = 1262) and 34 % for spectra measured at Jungfraujoch (N = 2702). The error is dominated by the systematic uncertainties in the spectroscopy parameters. Station-specific seasonal cycles were found to be consistent with known seasonal cycles of the dominant ammonia sources in the station surroundings. The developed retrieval methodology from FTIR instruments provides a new way of obtaining highly time-resolved measurements of ammonia burdens. FTIR-NH3 observations will be useful for understanding the dynamics of ammonia concentrations in the atmosphere and for satellite and model validation. It will also provide additional information to constrain the global ammonia budget. © 2015 Author(s).
BibTeX:
@article{Dammers2015,
  author = {Dammers, E. and Vigouroux, C. and Palm, M. and Mahieu, E. and Warneke, T. and Smale, D. and Langerock, B. and Franco, B. and Van Damme, M. and Schaap, M. and Notholt, J. and Erisman, J.W.},
  title = {Retrieval of ammonia from ground-based FTIR solar spectra},
  journal = {Atmospheric Chemistry and Physics},
  year = {2015},
  volume = {15},
  pages = {12789-12803},
  doi = {10.5194/acp-15-12789-2015}
}
Abstract: Ozone is an important greenhouse gas in terms of anthropogenic radiative forcing (RF). RF calculations for ozone were until recently entirely model based, and significant discrepancies were reported due to different model characteristics. However, new instantaneous radiative kernels (IRKs) calculated from hyperspectral thermal IR satellites have been able to help adjudicate between different climate model RF calculations. IRKs are defined as the sensitivity of the outgoing longwave radiation (OLR) flux with respect to the ozone vertical distribution in the full 9.6 μm band. Previous methods applied to measurements from the Tropospheric Emission Spectrometer (TES) on Aura rely on an anisotropy approximation for the angular integration. In this paper, we present a more accurate but more computationally expensive method to calculate these kernels. The method of direct integration is based on similar principles to the anisotropy approximation, but it deals more precisely with the integration of the Jacobians. We describe both methods and highlight their differences with respect to the IRKs and the ozone longwave radiative effect (LWRE), i.e., the radiative impact in OLR due to absorption by ozone, for both tropospheric and total columns, from measurements of the Infrared Atmospheric Sounding Interferometer (IASI) onboard MetOp-A. Biases between the two methods vary from -25 to +20 % for the LWRE, depending on the viewing angle. These biases point to the inadequacy of the anisotropy method, especially at nadir, suggesting that the TES-derived LWREs are biased low by around 25 % and that chemistry-climate model OLR biases with respect to TES are underestimated. In this paper we also exploit the sampling performance of IASI to obtain first daily global distributions of the LWRE, for 12 days (the 15th of each month) in 2011, calculated with the direct integration method. We show that the temporal variation of global and latitudinal averages of the LWRE shows patterns which are controlled by changes in the surface temperature and ozone variation due to specific processes, such as the ozone hole in the polar regions and stratospheric intrusions into the troposphere. © Author(s) 2015.
BibTeX:
@article{Doniki2015,
  author = {Doniki, S. and Hurtmans, D. and Clarisse, L. and Clerbaux, C. and Worden, H.M. and Bowman, K.W. and Coheur, P.-F.},
  title = {Instantaneous longwave radiative impact of ozone: An application on IASI/MetOp observations},
  journal = {Atmospheric Chemistry and Physics},
  year = {2015},
  volume = {15},
  pages = {12971-12987},
  doi = {10.5194/acp-15-12971-2015}
}
Abstract: We present global distributions of C2H2 and hydrogen cyanide (HCN) total columns derived from the Infrared Atmospheric Sounding Interferometer (IASI) for the years 2008-2010. These distributions are obtained with a fast method allowing to retrieve C2H2 abundance globally with a 5 % precision and HCN abundance in the tropical (subtropical) belt with a 10 % (25 %) precision. IASI data are compared for validation purposes with ground-based Fourier transform infrared (FTIR) spectrometer measurements at four selected stations. We show that there is an overall agreement between the ground-based and space measurements with correlation coefficients for daily mean measurements ranging from 0.28 to 0.81, depending on the site. Global C2H2 and subtropical HCN abundances retrieved from IASI spectra show the expected seasonality linked to variations in the anthropogenic emissions and seasonal biomass burning activity, as well as exceptional events, and are in good agreement with previous spaceborne studies. Total columns simulated by the Model for Ozone and Related Chemical Tracers, version 4 (MOZART-4) are compared to the ground-based FTIR measurements at the four selected stations. The model is able to capture the seasonality in the two species in most of the cases, with correlation coefficients for daily mean measurements ranging from 0.50 to 0.86, depending on the site. IASI measurements are also compared to the distributions from MOZART-4. Seasonal cycles observed from satellite data are reasonably well reproduced by the model with correlation coefficients ranging from g'0.31 to 0.93 for C2H2 daily means, and from 0.09 to 0.86 for HCN daily means, depending on the considered region. However, the anthropogenic (biomass burning) emissions used in the model seem to be overestimated (underestimated), and a negative global mean bias of 1 % (16 %) of the model relative to the satellite observations was found for C2H2 (HCN). © Author(s) 2015.
BibTeX:
@article{Duflot2015,
  author = {Duflot, V. and Wespes, C. and Clarisse, L. and Hurtmans, D. and Ngadi, Y. and Jones, N. and Paton-Walsh, C. and Hadji-Lazaro, J. and Vigouroux, C. and De Mazière, M. and Metzger, J.-M. and Mahieu, E. and Servais, C. and Hase, F. and Schneider, M. and Clerbaux, C. and Coheur, P.-F.},
  title = {Acetylene (C2H2) and hydrogen cyanide (HCN) from IASI satellite observations: Global distributions, validation, and comparison with model},
  journal = {Atmospheric Chemistry and Physics},
  year = {2015},
  volume = {15},
  pages = {10509-10527},
  doi = {10.5194/acp-15-10509-2015}
}
Abstract: An overview of the achievements and the current state of knowledge on reactive nitrogen in Europe, focusing on deposition, critical load exceedances, and modeled and measured trends.
BibTeX:
@article{Erisman2015,
  author = {Erisman, J.W. and Dammers, E. and Van Damme, M. and Soudzilovskaia, N. and Schaap, M.},
  title = {Trends in EU nitrogen deposition and impacts on ecosystems},
  journal = {EM: Air and Waste Management Association's Magazine for Environmental Managers},
  year = {2015},
  volume = {65},
  pages = {31-35}
}
Abstract: Carbon monoxide (CO) is a key atmospheric compound that can be remotely sensed by satellite on the global scale. Fifteen years of continuous observations are now available from the MOPITT/Terra mission (2000 to present). Another 15 and more years of observations will be provided by the IASI/MetOp instrument series (2007-2023 >). In order to study long-term variability and trends, a homogeneous record is required, which is not straightforward as the retrieved quantities are instrument and processing dependent. The present study aims at evaluating the consistency between the CO products derived from the MOPITT and IASI missions, both for total columns and vertical profiles, during a 6-year overlap period (2008-2013). The analysis is performed by first comparing the available 2013 versions of the retrieval algorithms (v5T for MOPITT and v20100815 for IASI), and second using a dedicated reprocessing of MOPITT CO profiles and columns using the same a priori information as the IASI product. MOPITT total columns are generally slightly higher over land (bias ranging from 0 to 13 %) than IASI data. When IASI and MOPITT data are retrieved with the same a priori constraints, correlation coefficients are slightly improved. Large discrepancies (total column bias over 15 %) observed in the Northern Hemisphere during the winter months are reduced by a factor of 2 to 2.5. The detailed analysis of retrieved vertical profiles compared with collocated aircraft data from the MOZAIC-IAGOS network, illustrates the advantages and disadvantages of a constant vs. a variable a priori. On one hand, MOPITT agrees better with the aircraft profiles for observations with persisting high levels of CO throughout the year due to pollution or seasonal fire activity (because the climatology-based a priori is supposed to be closer to the real atmospheric state). On the other hand, IASI performs better when unexpected events leading to high levels of CO occur, due to a larger variability associated with the a priori. © 2015 Author(s).
BibTeX:
@article{George2015,
  author = {George, M. and Clerbaux, C. and Bouarar, I. and Coheur, P.-F. and Deeter, M.N. and Edwards, D.P. and Francis, G. and Gille, J.C. and Hadji-Lazaro, J. and Hurtmans, D. and Inness, A. and Mao, D. and Worden, H.M.},
  title = {An examination of the long-term CO records from MOPITT and IASI: Comparison of retrieval methodology},
  journal = {Atmospheric Measurement Techniques},
  year = {2015},
  volume = {8},
  pages = {4313-4328},
  doi = {10.5194/amt-8-4313-2015}
}
Abstract: The Infrared Atmospheric Sounding Interferometer (IASI) flying onboard MetOpA and MetOpB is able to capture fine isotopic variations of the HDO to H2O ratio (δD) in the troposphere. Such observations at the high spatio-temporal resolution of the sounder are of great interest to improve our understanding of the mechanisms controlling humidity in the troposphere. In this study we aim to empirically assess the validity of our error estimation previously evaluated theoretically. To achieve this, we compare IASI δD retrieved profiles with other available profiles of δD, from the TES infrared sounder onboard AURA and from three ground-based FTIR stations produced within the MUSICA project: the NDACC (Network for the Detection of Atmospheric Composition Change) sites Kiruna and Izaña, and the TCCON site Karlsruhe, which in addition to near-infrared TCCON spectra also records mid-infrared spectra. We describe the achievable level of agreement between the different retrievals and show that these theoretical errors are in good agreement with empirical differences. The comparisons are made at different locations from tropical to Arctic latitudes, above sea and above land. Generally IASI and TES are similarly sensitive to δD in the free troposphere which allows one to compare their measurements directly. At tropical latitudes where IASI's sensitivity is lower than that of TES, we show that the agreement improves when taking into account the sensitivity of IASI in the TES retrieval. For the comparison IASI-FTIR only direct comparisons are performed because the sensitivity profiles of the two observing systems do not allow to take into account their differences of sensitivity. We identify a quasi negligible bias in the free troposphere (-3 ‰) between IASI retrieved δD with the TES, which are bias corrected, but important with the ground-based FTIR reaching -47 ‰. We also suggest that model-satellite observation comparisons could be optimized with IASI thanks to its high spatial and temporal sampling. © Author(s) 2015.
BibTeX:
@article{Lacour2015,
  author = {Lacour, J.-L. and Clarisse, L. and Worden, J. and Schneider, M. and Barthlott, S. and Hase, F. and Risi, C. and Clerbaux, C. and Hurtmans, D. and Coheur, P.-F.},
  title = {Cross-validation of IASI/MetOp derived tropospheric δd with TES and ground-based FTIR observations},
  journal = {Atmospheric Measurement Techniques},
  year = {2015},
  volume = {8},
  pages = {1447-1466},
  doi = {10.5194/amt-8-1447-2015}
}
BibTeX:
@article{Predoi-Cross2015,
  author = {Predoi-Cross, A. and Liu, W. and Murphy, R. and Povey, C. and Gamache, R. and Laraia, A. and McKellar, A.R.W. and Hurtmans, D. and Devi, V.M.},
  title = {Corrigendum to "Measurement and computations for temperature dependences of self-broadened carbon dioxide transitions in the 30012-00001 and 30013-00001 bands" [J. Quant. Spectrosc. Radiat. Transf., 111 (9) (2010) 1065-1079] doi: 10.1016/j.jqsrt.2010.01.003},
  journal = {Journal of Quantitative Spectroscopy and Radiative Transfer},
  year = {2015},
  volume = {164},
  pages = {256},
  doi = {10.1016/j.jqsrt.2015.06.017}
}
Abstract: The vertical columns of formaldehyde (HCHO) retrieved from two satellite instruments, the Global Ozone Monitoring Instrument-2 (GOME-2) on Metop-A and the Ozone Monitoring Instrument (OMI) on Aura, are used to constrain global emissions of HCHO precursors from open fires, vegetation and human activities in the year 2010. To this end, the emissions are varied and optimized using the adjoint model technique in the IMAGESv2 global CTM (chemical transport model) on a monthly basis and at the model resolution. Given the different local overpass times of GOME-2 (09:30 LT) and OMI (13:30 LT), the simulated diurnal cycle of HCHO columns is investigated and evaluated against ground-based optical measurements at seven sites in Europe, China and Africa. The modeled diurnal cycle exhibits large variability, reflecting competition between photochemistry and emission variations, with noon or early afternoon maxima at remote locations (oceans) and in regions dominated by anthropogenic emissions, late afternoon or evening maxima over fire scenes, and midday minima in isoprene-rich regions. The agreement between simulated and ground-based columns is generally better in summer (with a clear afternoon maximum at mid-latitude sites) than in winter, and the annually averaged ratio of afternoon to morning columns is slightly higher in the model (1.126) than in the ground-based measurements (1.043). The anthropogenic VOC (volatile organic compound) sources are found to be weakly constrained by the inversions on the global scale, mainly owing to their generally minor contribution to the HCHO columns, except over strongly polluted regions, like China. The OMI-based inversion yields total flux estimates over China close to the bottom-up inventory (24.6 vs. 25.5 TgVOC yrg-1 in the a priori) with, however, pronounced increases in the northeast of China and reductions in the south. Lower fluxes are estimated based on GOME-2 HCHO columns (20.6 TgVOC yrg-1), in particular over the northeast, likely reflecting mismatches between the observed and the modeled diurnal cycle in this region. The resulting biogenic and pyrogenic flux estimates from both optimizations generally show a good degree of consistency. A reduction of the global annual biogenic emissions of isoprene is derived, of 9 and 13 % according to GOME-2 and OMI, respectively, compared to the a priori estimate of 363 Tg in 2010. The reduction is largest (up to 25-40 %) in the Southeastern US, in accordance with earlier studies. The GOME-2 and OMI satellite columns suggest a global pyrogenic flux decrease by 36 and 33 %, respectively, compared to the GFEDv3 (Global Fire Emissions Database) inventory. This decrease is especially pronounced over tropical forests, such as in Amazonia, Thailand and Myanmar, and is supported by comparisons with CO observations from IASI (Infrared Atmospheric Sounding Interferometer). In contrast to these flux reductions, the emissions due to harvest waste burning are strongly enhanced over the northeastern China plain in June (by ca. 70 % in June according to OMI) as well as over Indochina in March. Sensitivity inversions showed robustness of the inferred estimates, which were found to lie within 7 % of the standard inversion results at the global scale. © Author(s) 2015.
BibTeX:
@article{Stavrakou2015,
  author = {Stavrakou, T. and Müller, J.-F. and Bauwens, M. and De Smedt, I. and Van Roozendael, M. and De Mazière, M. and Vigouroux, C. and Hendrick, F. and George, M. and Clerbaux, C. and Coheur, P.-F. and Guenther, A.},
  title = {How consistent are top-down hydrocarbon emissions based on formaldehyde observations from GOME-2 and OMI?},
  journal = {Atmospheric Chemistry and Physics},
  year = {2015},
  volume = {15},
  pages = {11861-11884},
  doi = {10.5194/acp-15-11861-2015}
}
Abstract: We present a new data set of sulfur dioxide (SO2) vertical columns from observations of the Ozone Monitoring Instrument (OMI)/AURA instrument between 2004 and 2013. The retrieval algorithm used is an advanced Differential Optical Absorption Spectroscopy (DOAS) scheme combined with radiative transfer calculation. It is developed in preparation for the operational processing of SO2 data product for the upcoming TROPOspheric Monitoring Instrument/Sentinel 5 Precursor mission. We evaluate the SO2 column results with those inferred from other satellite retrievals such as Infrared Atmospheric Sounding Interferometer and OMI (Linear Fit and Principal Component Analysis algorithms). A general good agreement between the different data sets is found for both volcanic and anthropogenic SO2 emission scenarios. We show that our algorithm produces SO2 columns with low noise and is able to provide accurate estimates of SO2. This conclusion is supported by important validation results over the heavily polluted site of Xianghe (China). Nearly 4 years of OMI and ground-based multiaxis DOAS SO2 columns are compared, and an excellent match is found. We also highlight the improved performance of the algorithm in capturing weak SO2 sources by detecting shipping SO2 emissions in long-term averaged data, an unreported measurement from space. © 2015. American Geophysical Union. All Rights Reserved.
BibTeX:
@article{Theys2015,
  author = {Theys, N. and De Smedt, I. and Van Gent, J. and Danckaert, T. and Wang, T. and Hendrick, F. and Stavrakou, T. and Bauduin, S. and Clarisse, L. and Li, C. and Krotkov, N. and Yu, H. and Brenot, H. and Van Roozendael, M.},
  title = {Sulfur dioxide vertical column DOAS retrievals from the Ozone Monitoring Instrument: Global observations and comparison to ground-based and satellite data},
  journal = {Journal of Geophysical Research},
  year = {2015},
  volume = {120},
  pages = {2470-2491},
  doi = {10.1002/2014JD022657}
}
Abstract: Limited availability of ammonia (NH3) observations is currently a barrier for effective monitoring of the nitrogen cycle. It prevents a full understanding of the atmospheric processes in which this trace gas is involved and therefore impedes determining its related budgets. Since the end of 2007, the Infrared Atmospheric Sounding Interferometer (IASI) satellite has been observing NH3 from space at a high spatio-temporal resolution. This valuable data set, already used by models, still needs validation. We present here a first attempt to validate IASI-NH3 measurements using existing independent ground-based and airborne data sets. The yearly distributions reveal similar patterns between ground-based and space-borne observations and highlight the scarcity of local NH3 measurements as well as their spatial heterogeneity and lack of representativity. By comparison with monthly resolved data sets in Europe, China and Africa, we show that IASI-NH3 observations are in fair agreement, but they are characterized by a smaller variation in concentrations. The use of hourly and airborne data sets to compare with IASI individual observations allows investigations of the impact of averaging as well as the representativity of independent observations for the satellite footprint. The importance of considering the latter and the added value of densely located airborne measurements at various altitudes to validate IASI-NH3 columns are discussed. Perspectives and guidelines for future validation work on NH3 satellite observations are presented. © Author(s) 2015.
BibTeX:
@article{VanDamme2015,
  author = {Van Damme, M. and Clarisse, L. and Dammers, E. and Liu, X. and Nowak, J.B. and Clerbaux, C. and Flechard, C.R. and Galy-Lacaux, C. and Xu, W. and Neuman, J.A. and Tang, Y.S. and Sutton, M.A. and Erisman, J.W. and Coheur, P.F.},
  title = {Towards validation of ammonia (NH3) measurements from the IASI satellite},
  journal = {Atmospheric Measurement Techniques},
  year = {2015},
  volume = {8},
  pages = {1575-1591},
  doi = {10.5194/amt-8-1575-2015}
}
Abstract: We exploit 6 years of measurements from the Infrared Atmospheric Sounding Interferometer (IASI)/MetOp-A instrument to identify seasonal patterns and interannual variability of atmospheric NH3. This is achieved by analyzing the time evolution of the monthly mean NH3 columns in 12 subcontinental areas around the world, simultaneously considering measurements from IASI morning and evening overpasses. For most regions, IASI has a sufficient sensitivity throughout the years to capture the seasonal patterns of NH3 columns, and we show that each region is characterized by a well-marked and distinctive cycle, with maxima mainly related to underlying emission processes. The largest column abundances and seasonal amplitudes throughout the years are found in southwestern Asia, with maxima twice as large as what is observed in southeastern China. The relation between emission sources and retrieved NH3 columns is emphasized at a smaller regional scale by inferring a climatology of the month of maximum columns. Key Points Six years of NH3 morning and evening IASI measurements are analyzed Seasonal cycles of atmospheric NH3 are characterized for subcontinental areas Source processes are attributed from a climatology of the month of NH3 maximum © 2015. American Geophysical Union. All Rights Reserved.
BibTeX:
@article{VanDamme2015a,
  author = {Van Damme, M. and Erisman, J.W. and Clarisse, L. and Dammers, E. and Whitburn, S. and Clerbaux, C. and Dolman, A.J. and Coheur, P.-F.},
  title = {Worldwide spatiotemporal atmospheric ammonia (NH3) columns variability revealed by satellite},
  journal = {Geophysical Research Letters},
  year = {2015},
  volume = {42},
  pages = {8660-8668},
  doi = {10.1002/2015GL065496}
}
Abstract: Two major droughts in the past decade had large impacts on carbon exchange in the Amazon. Recent analysis of vertical profile measurements of atmospheric CO2 and CO by Gatti et al. (2014) suggests that the 2010 drought turned the normally close-to-neutral annual Amazon carbon balance into a substantial source of nearly 0.5 PgC/yr, revealing a strong drought response. In this study, we revisit this hypothesis and interpret not only the same CO2/CO vertical profile measurements but also additional constraints on carbon exchange such as satellite observations of CO, burned area, and fire hot spots. The results from our CarbonTracker South America data assimilation system suggest that carbon uptake by vegetation was indeed reduced in 2010 but that the magnitude of the decrease strongly depends on the estimated 2010 and 2011 biomass burning emissions. We have used fire products based on burned area (Global Fire Emissions Database version 4), satellite-observed CO columns (Infrared Atmospheric Sounding Interferometer), fire radiative power (Global Fire Assimilation System version 1), and fire hot spots (Fire Inventory from NCAR version 1), and found an increase in biomass burning emissions in 2010 compared to 2011 of 0.16 to 0.24 PgC/yr. We derived a decrease of biospheric uptake ranging from 0.08 to 0.26 PgC/yr, with the range determined from a set of alternative inversions using different biomass burning estimates. Our numerical analysis of the 2010 Amazon drought results in a total reduction of carbon uptake of 0.24 to 0.50 PgC/yr and turns the balance from carbon sink to source. Our findings support the suggestion that the hydrological cycle will be an important driver of future changes in Amazonian carbon exchange. Key Points Amazon carbon budget estimated by CarbonTracker South America Biospheric uptake decreases by 0.08-0.26 PgC/yr in response to 2010 drought Amazon biomass burning emissions more than doubled during 2010 drought ©2015. American Geophysical Union. All Rights Reserved.
BibTeX:
@article{VanDerLaan-Luijkx2015,
  author = {Van Der Laan-Luijkx, I.T. and Van Der Velde, I.R. and Krol, M.C. and Gatti, L.V. and Domingues, L.G. and Correia, C.S.C. and Miller, J.B. and Gloor, M. and Van Leeuwen, T.T. and Kaiser, J.W. and Wiedinmyer, C. and Basu, S. and Clerbaux, C. and Peters, W.},
  title = {Response of the Amazon carbon balance to the 2010 drought derived with CarbonTracker South America},
  journal = {Global Biogeochemical Cycles},
  year = {2015},
  volume = {29},
  pages = {1092-1108},
  doi = {10.1002/2014GB005082}
}
Abstract: The Monitoring Atmospheric Composition and Climate (MACC) project represents the European Union's Copernicus Atmosphere Monitoring Service (CAMS) (http://www.copernicus.eu/), which became fully operational during 2015. The global near-real-time MACC model production run for aerosol and reactive gases provides daily analyses and 5-day forecasts of atmospheric composition fields. It is the only assimilation system worldwide that is operational to produce global analyses and forecasts of reactive gases and aerosol fields. We have investigated the ability of the MACC analysis system to simulate tropospheric concentrations of reactive gases covering the period between 2009 and 2012. A validation was performed based on carbon monoxide (CO), nitrogen dioxide (NO2) and ozone (O3) surface observations from the Global Atmosphere Watch (GAW) network, the O3 surface observations from the European Monitoring and Evaluation Programme (EMEP) and, furthermore, NO2 tropospheric columns, as well as CO total columns, derived from satellite sensors. The MACC system proved capable of reproducing reactive gas concentrations with consistent quality; however, with a seasonally dependent bias compared to surface and satellite observations - for northern hemispheric surface O3 mixing ratios, positive biases appear during the warm seasons and negative biases during the cold parts of the year, with monthly modified normalised mean biases (MNMBs) ranging between -30 and 30 % at the surface. Model biases are likely to result from difficulties in the simulation of vertical mixing at night and deficiencies in the model's dry deposition parameterisation. Observed tropospheric columns of NO2 and CO could be reproduced correctly during the warm seasons, but are mostly underestimated by the model during the cold seasons, when anthropogenic emissions are at their highest level, especially over the US, Europe and Asia. Monthly MNMBs of the satellite data evaluation range from values between -110 and 40 % for NO2 and at most -20 % for CO, over the investigated regions. The underestimation is likely to result from a combination of errors concerning the dry deposition parameterisation and certain limitations in the current emission inventories, together with an insufficiently established seasonality in the emissions. © Author(s) 2015.
BibTeX:
@article{Wagner2015,
  author = {Wagner, A. and Blechschmidt, A.-M. and Bouarar, I. and Brunke, E.-G. and Clerbaux, C. and Cupeiro, M. and Cristofanelli, P. and Eskes, H. and Flemming, J. and Flentje, H. and George, M. and Gilge, S. and Hilboll, A. and Inness, A. and Kapsomenakis, J. and Richter, A. and Ries, L. and Spangl, W. and Stein, O. and Weller, R. and Zerefos, C.},
  title = {Evaluation of the MACC operational forecast system - Potential and challenges of global near-real-time modelling with respect to reactive gases in the troposphere},
  journal = {Atmospheric Chemistry and Physics},
  year = {2015},
  volume = {15},
  pages = {14005-14030},
  doi = {10.5194/acp-15-14005-2015}
}
Abstract: Most satellite models of production have been designed and calibrated for use in the open ocean. Coastal waters are optically more complex, and the use of chlorophyll a (chl a) as a first-order predictor of primary production may lead to substantial errors due to significant quantities of coloured dissolved organic matter (CDOM) and total suspended material (TSM) within the first optical depth. We demonstrate the use of phytoplankton absorption as a proxy to estimate primary production in the coastal waters of the North Sea and Western English Channel for both total, micro- and nano+pico-phytoplankton production. The method is implemented to extrapolate the absorption coefficient of phytoplankton and production at the sea surface to depth to give integrated fields of total and micro- and nano+pico-phytoplankton primary production using the peak in absorption coefficient at red wavelengths. The model is accurate to 8% in the Western English Channel and 22% in this region and the North Sea. By comparison, the accuracy of similar chl a based production models was >250%. The applicability of the method to autonomous optical sensors and remotely sensed aircraft data in both coastal and estuarine environments is discussed. © Inter-Research 2014.
BibTeX:
@article{Barnes2014,
  author = {Barnes, M.K. and Tilstone, G.H. and Smyth, T.J. and Suggett, D.J. and Astoreca, R. and Lancelot, C. and Kromkamp, J.C.},
  title = {Absorption-based algorithm of primary production for total and size-fractionated phytoplankton in coastal waters},
  journal = {Marine Ecology Progress Series},
  year = {2014},
  volume = {504},
  pages = {73-89},
  doi = {10.3354/meps10751}
}
Abstract: We estimate the CO2 flux over Tropical Asia in 2009, 2010, and 2011 using Greenhouse Gases Observing Satellite (GOSAT) total column CO 2(XCO2) and in situ measurements of CO2. Compared to flux estimates from assimilating surface measurements of CO 2, GOSAT XCO2 estimates a more dynamic seasonal cycle and a large source in March-May 2010. The more dynamic seasonal cycle is consistent with earlier work by Patra et al. (2011), and the enhanced 2010 source is supported by independent upper air CO2 measurements from the Comprehensive Observation Network for Trace gases by Airliner (CONTRAIL) project. Using Infrared Atmospheric Sounding Interferometer (IASI) measurements of total column CO (XCO), we show that biomass burning CO2 can explain neither the dynamic seasonal cycle nor the 2010 source. We conclude that both features must come from the terrestrial biosphere. In particular, the 2010 source points to biosphere response to above-average temperatures that year. Key Points GOSAT estimates a dynamic seasonal cycle over Tropical Asia The GOSAT-estimated seasonal cycle is confirmed by CONTRAIL data IASI CO shows that the dynamism is not caused by biomass burning ©2014. American Geophysical Union. All Rights Reserved.
BibTeX:
@article{Basu2014,
  author = {Basu, S. and Krol, M. and Butz, A. and Clerbaux, C. and Sawa, Y. and Machida, T. and Matsueda, H. and Frankenberg, C. and Hasekamp, O.P. and Aben, I.},
  title = {The seasonal variation of the CO2 flux over Tropical Asia estimated from GOSAT, CONTRAIL, and IASI},
  journal = {Geophysical Research Letters},
  year = {2014},
  volume = {41},
  pages = {1809-1815},
  doi = {10.1002/2013GL059105}
}
Abstract: Norilsk is one of the most polluted cities in the world, largely because of intense mining of heavy metals. Here we present satellite observations of SO2 in a large area surrounding the city, derived from 4 years of measurements from the Infrared Atmospheric Sounding Interferometer (IASI), the nadir thermal infrared (TIR) sounder onboard the MetOp platforms. TIR instruments are conventionally considered to be inadequate for monitoring near-surface composition, because their sensitivity to the lowest part of the atmosphere is limited by the thermal contrast between the ground and the air above it. We demonstrate that IASI is capable of measuring SO2 (here as a partial column from 0 to 2 km) in Norilsk, thanks to the large temperature inversions and the low humidity in wintertime. We discuss the influence of thermal contrast and of surface humidity on the SO2 retrieved columns and estimate the retrieval errors. Using a simple box model, we derive the yearly total emissions of SO2 from Norilsk and compare them to previously reported values. More generally, we present in this work the first large-scale demonstration of the capability of space-based TIR sounders to measure near-surface SO2 anthropogenic pollution. © 2014. American Geophysical Union. All Rights Reserved.
BibTeX:
@article{Bauduin2014,
  author = {Bauduin, S. and Clarisse, L. and Clerbaux, C. and Hurtmans, D. and Coheur, P.-F.},
  title = {IASI observations of sulfur dioxide (SO2) in the boundary layer of Norilsk},
  journal = {Journal of Geophysical Research},
  year = {2014},
  volume = {119},
  pages = {4253-4263},
  doi = {10.1002/2013JD021405}
}
Abstract: Forecasting the dispersal of volcanic clouds during an eruption is of primary importance, especially for ensuring aviation safety. As volcanic emissions are characterized by rapid variations of emission rate and height, the (generally) high level of uncertainty in the emission parameters represents a critical issue that limits the robustness of volcanic cloud dispersal forecasts. An inverse modeling scheme, combining satellite observations of the volcanic cloud with a regional chemistry-transport model, allows reconstructing this source term at high temporal resolution. We demonstrate here how a progressive assimilation of freshly acquired satellite observations, via such an inverse modeling procedure, allows for delivering robust sulfur dioxide (SO2) cloud dispersal forecasts during the eruption. This approach provides a computationally cheap estimate of the expected location and mass loading of volcanic clouds, including the identification of SO2-rich parts. Key Points Refined SO2 cloud dispersal forecasts by assimilation of satellite observations Refined estimation of source emissions using an inverse modeling approach Compared to standard methods, cloud SO2-rich parts are robustly forecasted © 2014. American Geophysical Union. All Rights Reserved.
BibTeX:
@article{Boichu2014,
  author = {Boichu, M. and Clarisse, L. and Khvorostyanov, D. and Clerbaux, C.},
  title = {Improving volcanic sulfur dioxide cloud dispersal forecasts by progressive assimilation of satellite observations},
  journal = {Geophysical Research Letters},
  year = {2014},
  volume = {41},
  pages = {2637-2643},
  doi = {10.1002/2014GL059496}
}
Abstract: In this paper we investigate a severe pollution episode that occurred in Beijing, Tianjin, and the Hebei province in January 2013. The episode was caused by the combination of anthropogenic emissions and a high-pressure system that trapped pollutants in the boundary layer. Using IASI (Infrared Atmospheric Sounding Interferometer) satellite measurements, high concentrations of key trace gases such as carbon monoxide (CO), sulfur dioxide (SO2), and ammonia (NH3) along with ammonium sulfate aerosol ((NH 4)2SO4) are found. We show that IASI is able to detect boundary layer pollution in case of large negative thermal contrast combined with high levels of pollution. Our findings demonstrate that anthropogenic key pollutants, such as CO and SO2, can be monitored by IASI in the North China Plain during wintertime in support of air quality evaluation and management. ©2013. American Geophysical Union. All Rights Reserved.
BibTeX:
@article{Boynard2014,
  author = {Boynard, A. and Clerbaux, C. and Clarisse, L. and Safieddine, S. and Pommier, M. and Van Damme, M. and Bauduin, S. and Oudot, C. and Hadji-Lazaro, J. and Hurtmans, D. and Coheur, P.-F.},
  title = {First simultaneous space measurements of atmospheric pollutants in the boundary layer from IASI: A case study in the North China Plain},
  journal = {Geophysical Research Letters},
  year = {2014},
  volume = {41},
  pages = {645-651},
  doi = {10.1002/2013GL058333}
}
Abstract: Volcanic eruptions emit plumes of ash and gases into the atmosphere, potentially at very high altitudes. Ash-rich plumes are hazardous for airplanes as ash is very abrasive and easily melts inside their engines. With more than 50 active volcanoes per year and the ever-increasing number of commercial flights, the safety of airplanes is a real concern. Satellite measurements are ideal for monitoring global volcanic activity and, in combination with atmospheric dispersion models, to track and forecast volcanic plumes. Here we present the Support to Aviation Control Service (SACS, http://sacs.aeronomie.be), which is a free online service initiated by the European Space Agency (ESA) for the near-real-time (NRT) satellite monitoring of volcanic plumes of SO2 and ash. It combines data from three ultraviolet (UV)-visible and three infrared (IR) spectrometers. The UV-vis sensors are the Ozone Monitoring Instrument (OMI) and the Global Ozone Monitoring Experiment-2 (GOME-2) on-board the two polar orbiting meteorological satellites (MetOp-A & MetOp-B) operated by the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT). The IR sensors are the Atmospheric InfraRed Sounder (AIRS) and the Infrared Atmospheric Sounding Interferometer (IASI) on-board MetOp-A & MetOp-B. This new multi-sensor warning system of volcanic emissions is based on the selective detection of SO2 and ash. This system is optimised to avoid false alerts while at the same time limiting the number of notifications in case of large plumes. A successful rate with more than 95% of notifications corresponding to true volcanic activity is obtained by the SACS system. copyright © Author(s) 2014.
BibTeX:
@article{Brenot2014,
  author = {Brenot, H. and Theys, N. and Clarisse, L. and Van Geffen, J. and Van Gent, J. and Van Roozendael, M. and Van Der A, R. and Hurtmans, D. and Coheur, P.-F. and Clerbaux, C. and Valks, P. and Hedelt, P. and Prata, F. and Rasson, O. and Sievers, K. and Zehner, C.},
  title = {Support to aviation control service (SACS): An online service for near-real-time satellite monitoring of volcanic plumes},
  journal = {Natural Hazards and Earth System Sciences},
  year = {2014},
  volume = {14},
  pages = {1099-1123},
  doi = {10.5194/nhess-14-1099-2014}
}
Abstract: In the wake of the June 2011 Nabro eruption, large stratospheric plumes were observed by several instruments up to altitudes of 21 km, much higher than initial reported injection heights. It has been debated whether deep convection associated with the Asian Summer Monsoon anticyclone played a vital role in the vertical transport of the plume. Here we present a new and fast SO2 height retrieval algorithm for observations of the Infrared Atmospheric Sounding Interferometer (IASI). A comprehensive validation with forward trajectories and coincident CALIOP measurements is presented which indicates an accuracy better than 2 km for plumes below 20 km and SO2 columns up to the 1 DU level. We use this new product to analyse the Nabro eruption. Our findings indicate an initial plume located mainly between 15 and 17 km for which the lower parts underwent in succession rapid descent and uplift, within the Asian Monsoon anticyclone circulation, up to the stable thermal tropopause between 16 and 18 km, from where it slowly ascended further into the stratosphere. Evidence is presented that emissions in the first week of the eruption also contributed to the stratospheric sulfur input. This includes a second eruption between 15 and 17 km on the 16th and continuous emissions in the mid-troposphere of which some were also entrained and lifted within the anticyclonic circulation. © 2014 Author(s).
BibTeX:
@article{Clarisse2014,
  author = {Clarisse, L. and Coheur, P.-F. and Theys, N. and Hurtmans, D. and Clerbaux, C.},
  title = {The 2011 Nabro eruption, a SO2 plume height analysis using IASI measurements},
  journal = {Atmospheric Chemistry and Physics},
  year = {2014},
  volume = {14},
  pages = {3095-3111},
  doi = {10.5194/acp-14-3095-2014}
}
Abstract: This paper interprets tropical tropospheric nitric acid columns from the Infrared Atmospheric Sounding Interferometer (IASI) satellite instrument with a global chemical transport model (GEOS-Chem). GEOS-Chemand IASI columns generally agree over the tropical ocean to within 10%. However, the GEOS-Chem simulation underestimates IASI nitric acid over Southeast Asia by a factor of 2. The regional nitric acid bias is confirmed by comparing the GEOS-Chem simulation with additional satellite (High Resolution Dynamics Limb Sounder, Atmospheric Chemistry Experiment Fourier Transform Spectrometer) and aircraft (Pacific Exploratory Mission (PEM)-Tropics A and PEM-West B) observations of the middle and upper troposphere. This bias appears to be driven by the lightning NOx parameterization, both in terms of the magnitude of the NOx source and the ozone production efficiency of concentrated lightning NOx plumes. We tested a subgrid lightning plume parameterization and found that an ozone production efficiency of 15 mol/mol in lightning plumes over Southeast Asia in conjunction with an additional 0.5 Tg N would reduce the regional nitric acid bias from 92% to 6% without perturbing the rest of the tropics. Other sensitivity studies such as modified NOx yield per flash, increased altitude of lightning NOx emissions, decreased convective mass flux, or increased scavenging of nitric acid required unrealistic changes to reduce the bias. © 2014. American Geophysical Union. All Rights Reserved.
BibTeX:
@article{Cooper2014,
  author = {Cooper, M. and Martin, R.V. and Wespes, C. and Coheur, P.-F. and Clerbaux, C. and Murray, L.T.},
  title = {Tropospheric nitric acid columns from the IASI satellite instrument interpreted with a chemical transport model: Implications for parameterizations of nitric oxide production by lightning},
  journal = {Journal of Geophysical Research: Atmospheres},
  year = {2014},
  volume = {119},
  pages = {10068-10079},
  doi = {10.1002/2014JD021907}
}
Abstract: Besides their strong contribution to weather forecast improvement through data assimilation, thermal infrared sounders onboard polar-orbiting platforms are now playing a key role for monitoring atmospheric composition changes. The Infrared Atmospheric Sounding Interferometer (IASI) instrument developed by the French space agency (CNES) and launched by EUMETSAT onboard the Metop satellite series is providing essential inputs for weather forecasting and pollution/climate monitoring owing to its smart combination of large horizontal swath, good spectral resolution and high radiometric performance. EUMETSAT is currently preparing the next polar-orbiting program (EPS-SG) with the Metop-SG satellite series that should be launched around 2020. In this framework, CNES is studying the concept of a new instrument, the IASI-New Generation (IASI-NG), characterized by an improvement of both spectral and radiometric characteristics as compared to IASI, with three objectives: (i) continuity of the IASI/Metop series; (ii) improvement of vertical resolution; and (iii) improvement of the accuracy and detection threshold for atmospheric and surface components. In this paper, we show that an improvement of spectral resolution and radiometric noise fulfil these objectives by leading to (i) a better vertical coverage in the lower part of the troposphere, thanks to the increase in spectral resolution; and (ii) an increase in the accuracy of the retrieval of several thermodynamic, climate and chemistry variables, thanks to the improved signal-to-noise ratio as well as less interference between the signatures of the absorbing species in the measured radiances. The detection limit of several atmospheric species is also improved. We conclude that IASI-NG has the potential to strongly benefit the numerical weather prediction, chemistry and climate communities now connected through the European GMES/Copernicus initiative. © Author(s) 2014.
BibTeX:
@article{Crevoisier2014,
  author = {Crevoisier, C. and Clerbaux, C. and Guidard, V. and Phulpin, T. and Armante, R. and Barret, B. and Camy-Peyret, C. and Chaboureau, J.-P. and Coheur, P.-F. and Crépeau, L. and Dufour, G. and Labonnote, L. and Lavanant, L. and Hadji-Lazaro, J. and Herbin, H. and Jacquinet-Husson, N. and Payan, S. and Péquignot, E. and Pierangelo, C. and Sellitto, P. and Stubenrauch, C.},
  title = {Towards IASI-New Generation (IASI-NG): Impact of improved spectral resolution and radiometric noise on the retrieval of thermodynamic, chemistry and climate variables},
  journal = {Atmospheric Measurement Techniques},
  year = {2014},
  volume = {7},
  pages = {4367-4385},
  doi = {10.5194/amt-7-4367-2014}
}
Abstract: Peak stratospheric chlorofluorocarbon (CFC) and other ozone depleting substance (ODS) concentrations were reached in the mid-to late 1990s. Detection and attribution of the expected recovery of the stratospheric ozone layer in an atmosphere with reduced ODSs as well as efforts to understand the evolution of stratospheric ozone in the presence of increasing greenhouse gases are key current research topics. These require a critical examination of the ozone changes with an accurate knowledge of the spatial (geographical and vertical) and temporal ozone response. For such an examination, it is vital that the quality of the measurements used be as high as possible and measurement uncertainties well quantified.

In preparation for the 2014 United Nations Environment Programme (UNEP)/World Meteorological Organization (WMO) Scientific Assessment of Ozone Depletion, the SPARC/IO3C/IGACO-O3/NDACC (SI2N) Initiative was designed to study and document changes in the global ozone profile distribution. This requires assessing long-term ozone profile data sets in regards to measurement stability and uncertainty characteristics. The ultimate goal is to establish suitability for estimating long-term ozone trends to contribute to ozone recovery studies. Some of the data sets have been improved as part of this initiative with updated versions now available.

This summary presents an overview of stratospheric ozone profile measurement data sets (ground and satellite based) available for ozone recovery studies. Here we document measurement techniques, spatial and temporal coverage, vertical resolution, native units and measurement uncertainties. In addition, the latest data versions are briefly described (including data version updates as well as detailing multiple retrievals when available for a given satellite instrument). Archive location information for each data set is also given. © Author(s) 2014.
BibTeX:
@article{Hassler2014,
  author = {Hassler, B. and Petropavlovskikh, I. and Staehelin, J. and August, T. and Bhartia, P.K. and Clerbaux, C. and Degenstein, D. and De Mazière, M. and Dinelli, B.M. and Dudhia, A. and Dufour, G. and Frith, S.M. and Froidevaux, L. and Godin-Beekmann, S. and Granville, J. and Harris, N.R.P. and Hoppel, K. and Hubert, D. and Kasai, Y. and Kurylo, M.J. and Kyrölä, E. and Levelt, P.F. and McElroy, C.T. and McPeters, R.D. and Munro, R. and Nakajima, H. and Parrish, A. and Raspollini, P. and Remsberg, E.E. and Rosenlof, K.H. and Rozanov, A. and Sano, T. and Sasano, Y. and Shiotani, M. and Smit, H.G.J. and Stiller, G. and Tamminen, J. and Tarasick, D.W. and Urban, J. and Van Der A, R.J. and Veefkind, J.P. and Vigouroux, C. and Von Clarmann, T. and Von Savigny, C. and Walker, K.A. and Weber, M. and Wild, J. and Zawodny, J.M.},
  title = {Past changes in the vertical distribution of ozone – Part 1: Measurement techniques, uncertainties and availability},
  journal = {Atmospheric Measurement Techniques},
  year = {2014},
  volume = {7},
  pages = {1395-1427},
  doi = {10.5194/amt-7-1395-2014}
}
Abstract: Gravity waves are an important driver for the atmospheric circulation and have substantial impact on weather and climate. Satellite instruments offer excellent opportunities to study gravity waves on a global scale. This study focuses on observations from the Atmospheric Infrared Sounder (AIRS) onboard the National Aeronautics and Space Administration Aqua satellite and the Infrared Atmospheric Sounding Interferometer (IASI) onboard the European MetOp satellites. The main aim of this study is an intercomparison of stratospheric gravity wave observations of both instruments. In particular, we analyzed AIRS and IASI 4.3 μm brightness temperature measurements, which directly relate to stratospheric temperature. Three case studies showed that AIRS and IASI provide a clear and consistent picture of the temporal development of individual gravity wave events. Statistical comparisons based on a 5-year period of measurements (2008-2012) showed similar spatial and temporal patterns of gravity wave activity. However, the statistical comparisons also revealed systematic differences of variances between AIRS and IASI that we attribute to the different spatial measurement characteristics of both instruments. We also found differences between day- and nighttime data that are partly due to the local time variations of the gravity wave sources. While AIRS has been used successfully in many previous gravity wave studies, IASI data are applied here for the first time for that purpose. Our study shows that gravity wave observations from different hyperspectral infrared sounders such as AIRS and IASI can be directly related to each other, if instrument-specific characteristics such as different noise levels and spatial resolution and sampling are carefully considered. The ability to combine observations from different satellites provides an opportunity to create a long-term record, which is an exciting prospect for future climatological studies of stratospheric gravity wave activity. © Author(s) 2014.
BibTeX:
@article{Hoffmann2014,
  author = {Hoffmann, L. and Alexander, M.J. and Clerbaux, C. and Grimsdell, A.W. and Meyer, C.I. and Rößler, T. and Tournier, B.},
  title = {Intercomparison of stratospheric gravity wave observations with AIRS and IASI},
  journal = {Atmospheric Measurement Techniques},
  year = {2014},
  volume = {7},
  pages = {4517-4537},
  doi = {10.5194/amt-7-4517-2014}
}
Abstract: A method to constrain carbon dioxide (CO2) emissions from open biomass burning by using satellite observations of co-emitted species and a chemistry-transport model (CTM) is proposed and applied to the case of wildfires in Siberia. CO2emissions are assessed by means of an emission model assuming a direct relationship between the biomass burning rate (BBR) and the fire radiative power (FRP) derived from MODIS measurements. The key features of the method are (1) estimating the FRP-to-BBR conversion factors (α) for different vegetative land cover types by assimilating the satellite observations of co-emitted species into the CTM, (2) optimal combination of the estimates of α derived independently from satellite observations of different species (CO and aerosol in this study), and (3) estimation of the diurnal cycle of the fire emissions directly from the FRP measurements. Values of α for forest and grassland fires in Siberia and their uncertainties are estimated using the Infrared Atmospheric Sounding Interferometer (IASI) carbon monoxide (CO) retrievals and MODIS aerosol optical depth (AOD) measurements combined with outputs from the CHIMERE mesoscale chemistry-transport model. The constrained CO emissions are validated through comparison of the respective simulations with independent data of ground-based CO measurements at the ZOTTO site. Using our optimal regional-scale estimates of the conversion factors (which are found to be in agreement with earlier published estimates obtained from local measurements of experimental fires), the total CO2emissions from wildfires in Siberia in 2012 are estimated to be in the range from 280 to 550 Tg C, with the optimal (maximum likelihood) value of 392 Tg C. Sensitivity test cases featuring different assumptions regarding the injection height and diurnal variations of emissions indicate that the derived estimates of the total CO2emissions in Siberia are robust with respect to the modeling options (the different estimates vary within less than 15% of their magnitude). The CO2emission estimates obtained for several years are compared with independent estimates provided by the GFED3.1 and GFASv1.0 global emission inventories. It is found that our "top-down" estimates for the total annual biomass burning CO2emissions in the period from 2007 to 2011 in Siberia are by factors of 2.5 and 1.8 larger than the respective bottom-up estimates; these discrepancies cannot be fully explained by uncertainties in our estimates. There are also considerable differences in the spatial distribution of the different emission estimates; some of those differences have a systematic character and require further analysis. © Author(s) 2014. CC Attribution 3.0 License.
BibTeX:
@article{Konovalov2014,
  author = {Konovalov, I.B. and Berezin, E.V. and Ciais, P. and Broquet, G. and Beekmann, M. and Hadji-Lazaro, J. and Clerbaux, C. and Andreae, M.O. and Kaiser, J.W. and Schulze, E.-D.},
  title = {Constraining CO2emissions from open biomass burning by satellite observations of co-emitted species: A method and its application to wildfires in Siberia},
  journal = {Atmospheric Chemistry and Physics},
  year = {2014},
  volume = {14},
  pages = {10383-10410},
  doi = {10.5194/acp-14-10383-2014}
}
Abstract: The European Space Agency project Satellite Monitoring of Ash and Sulphur Dioxide for the mitigation of Aviation Hazards, was introduced after the eruption of the Icelandic volcano Eyjafjallajökull in the spring of 2010 to facilitate the development of an optimal End­to­End System for Volcanic Ash Plume Monitoring and Prediction. The Eyjafjallajökull plume drifted towards Europe and caused major disruptions of European air traffic for several weeks affecting the everyday life of millions of people. The limitations in volcanic plume monitoring and prediction capabilities gave birth to this observational system which is based on comprehensive satellite­derived ash plume and sulphur dioxide [SO2] level estimates, as well as a widespread validation using supplementary satellite, aircraft and ground­based measurements. Inter­comparison of the volcanic total SO2 column and plume height observed by GOME­2/Metop­A and IASI/Metop­A are shown before, during and after the Eyjafjallajökull 2010 eruptions as well as for the 2011 Grímsvötn eruption. Co­located ground­based Brewer Spectro­photometer data extracted from the World Ozone and Ultraviolet Radiation Data Centre for de Bilt, the Netherlands, are also compared to the different satellite estimates. Promising agreement is found for the two different types of instrument for the SO2 columns with linear regression coefficients ranging around from 0.64 when comparing the different instruments and 0.85 when comparing the two different IASI algorithms. The agreement for the plume height is lower, possibly due to the major differences between the height retrieval part of the GOME2 and IASI algorithms. The comparisons with the Brewer ground­based station in de Bilt, The Netherlands show good qualitative agreement for the peak of the event however stronger eruptive signals are required for a longer quantitative comparison. © 2014, Editrice Compositori s.r.l., All rights reserved.
BibTeX:
@article{Koukouli2014,
  author = {Koukouli, M.E. and Clarisse, L. and Carboni, E. and Van Gent, J. and Spinetti, C. and Balis, D. and Dimopoulos, S. and Grainger, R. and Theys, N. and Tampellini, L. and Zehner, C.},
  title = {Intercomparison of Metop-A SO2 measurements during the 2010- 2011 Icelandic eruptions},
  journal = {Annals of Geophysics},
  year = {2014},
  volume = {57},
  article number = {A007},
  doi = {10.4401/ag-6613}
}
Abstract: We present the results of an extensive validation program of the most recent version of ozone vertical profiles retrieved with the IMK/IAA (Institute for Meteorology and Climate Research/Instituto de Astrofísica de Andalucía) MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) research level 2 processor from version 5 spectral level 1 data. The time period covered corresponds to the reduced spectral resolution period of the MIPAS instrument, i.e., January 2005-April 2012. The comparison with satellite instruments includes all post-2005 satellite limb and occultation sensors that have measured the vertical profiles of tropospheric and stratospheric ozone: ACE-FTS, GOMOS, HALOE, HIRDLS, MLS, OSIRIS, POAM, SAGE II, SCIAMACHY, SMILES, and SMR. In addition, balloon-borne MkIV solar occultation measurements and ground-based Umkehr measurements have been included, as well as two nadir sensors: IASI and SBUV. For each reference data set, bias determination and precision assessment are performed. Better agreement with reference instruments than for the previous data version, V5R-O3-220 (Laeng et al., 2014), is found: the known high bias around the ozone vmr (volume mixing ratio) peak is significantly reduced and the vertical resolution at 35 km has been improved. The agreement with limb and solar occultation reference instruments that have a known small bias vs. ozonesondes is within 7% in the lower and middle stratosphere and 5% in the upper troposphere. Around the ozone vmr peak, the agreement with most of the satellite reference instruments is within 5%; this bias is as low as 3% for ACE-FTS, MLS, OSIRIS, POAM and SBUV. © Author(s) 2014.
BibTeX:
@article{Laeng2014,
  author = {Laeng, A. and Grabowski, U. and Von Clarmann, T. and Stiller, G. and Glatthor, N. and Höpfner, M. and Kellmann, S. and Kiefer, M. and Linden, A. and Lossow, S. and Sofieva, V. and Petropavlovskikh, I. and Hubert, D. and Bathgate, T. and Bernath, P. and Boone, C.D. and Clerbaux, C. and Coheur, P. and Damadeo, R. and Degenstein, D. and Frith, S. and Froidevaux, L. and Gille, J. and Hoppel, K. and Mchugh, M. and Kasai, Y. and Lumpe, J. and Rahpoe, N. and Toon, G. and Sano, T. and Suzuki, M. and Tamminen, J. and Urban, J. and Walker, K. and Weber, M. and Zawodny, J.},
  title = {Validation of MIPAS IMK/IAA V5R-O3-224 ozone profiles},
  journal = {Atmospheric Measurement Techniques},
  year = {2014},
  volume = {7},
  pages = {3971-3987},
  doi = {10.5194/amt-7-3971-2014}
}
Abstract: The advent of high-resolution spectrographs and detailed stellar atmosphere modelling has strengthened the need for accurate molecular data. Carbon-enhanced metal-poor (CEMP) stars spectra are interesting objects with which to study transitions from the CH molecule. We combine programs for spectral analysis of molecules and stellar-radiative transfer codes to build an extensive CH linelist, including predissociation broadening as well as newly identified levels. We show examples of strong predissociation CH lines in CEMP stars, and we stress the important role played by the CH features in the Bond-Neff feature depressing the spectra of barium stars by as much as 0.2 mag in the λ = 3000-5500 Å range. Because of the extreme thermodynamic conditions prevailing in stellar atmospheres (compared to the laboratory), molecular transitions with high energy levels can be observed. Stellar spectra can thus be used to constrain and improve molecular data. © 2014 ESO.
BibTeX:
@article{Masseron2014,
  author = {Masseron, T. and Plez, B. and Van Eck, S. and Colin, R. and Daoutidis, I. and Godefroid, M. and Coheur, P.-F. and Bernath, P. and Jorissen, A. and Christlieb, N.},
  title = {CH in stellar atmospheres: An extensive linelist},
  journal = {Astronomy and Astrophysics},
  year = {2014},
  volume = {571},
  article number = {A47},
  doi = {10.1051/0004-6361/201423956}
}
Abstract: Modeling the transport of volcanic ash and gases released during volcanic eruptions is crucially dependent on knowledge of the source term of the eruption, that is, the source strength as a function of altitude and time. For the first time, an inversion method is used to estimate the source terms of both volcanic sulfur dioxide (SO2) and ash. It was applied to the explosive volcanic eruption of Grímsvötn, Iceland, in May 2011. The method uses input from the particle dispersion model, FLEXPART (flexible particle dispersion model), a priori source estimates, and satellite observations of SO2 or ash total columns from Infrared Atmospheric Sounding Interferometer to separately obtain the source terms for volcanic SO2 and fine ash. The estimated source terms show that SO2 was emitted mostly to high altitudes (5 to 13 km) during about 18 h (22 May, 00-18 UTC) while fine ash was emitted mostly to low altitudes (below 4 km) during roughly 24 h (22 May 06 UTC to 23 May 06 UTC). FLEXPART simulations using the estimated source terms show a clear separation of SO2 (transported mostly northwestward) and the fine ash (transported mostly southeastward). This corresponds well with independent satellite observations and measured aerosol mass concentrations and lidar measurements at surface stations in Scandinavia. Aircraft measurements above Iceland and Germany confirmed that the ash was located in the lower atmosphere. This demonstrates that the inversion method, in this case, is able to distinguish between emission heights of SO2 and ash and can capture resulting differences in transport patterns. Key Points Ash and SO2 source terms estimated using inverse techniques and satellite data The transport and separation of ash and SO2 are modeled Model simulations correspond well with a range of independent observations ©2014. The Authors.
BibTeX:
@article{Moxnes2014,
  author = {Moxnes, E.D. and Kristiansen, N.I. and Stohl, A. and Clarisse, L. and Durant, A. and Weber, K. and Vogel, A.},
  title = {Separation of ash and sulfur dioxide during the 2011 Grímsvötn eruption},
  journal = {Journal of Geophysical Research: Atmospheres},
  year = {2014},
  volume = {119},
  pages = {7477-7501},
  doi = {10.1002/2013JD021129}
}
Abstract: We apply the Tropospheric Emission Spectrometer (TES) ozone retrieval algorithm to Infrared Atmospheric Sounding Instrument (IASI) radiances and characterise the uncertainties and information content of the retrieved ozone profiles. This study focuses on mid-latitudes for the year 2008. We validate our results by comparing the IASI ozone profiles to ozone sondes. In the sonde comparisons, we find a negative bias (1-10%) in the IASI profiles in the lower to mid-troposphere and a positive bias (up to 14%) in the upper troposphere/lower stratosphere (UTLS) region. For the described cases, the degrees of freedom for signal are on average 3.2, 0.3, 0.8, and 0.9 for the columns 0 km - top of atmosphere, (0-6), (0-11), and (8-16) km, respectively. We find that our biases with respect to sondes and our degrees of freedom for signal for ozone are comparable to previously published results from other IASI ozone algorithms. In addition to evaluating biases, we validate the retrieval errors by comparing predicted errors to the sample covariance matrix of the IASI observations themselves. For the predicted versus empirical error comparison, we find that these errors are consistent and that the measurement noise and the interference of temperature and water vapour on the retrieval together mostly explain the empirically derived random errors. In general, the precision of the IASI ozone profiles is better than 20%. © 2014 Author(s).
BibTeX:
@article{Oetjen2014,
  author = {Oetjen, H. and Payne, V.H. and Kulawik, S.S. and Eldering, A. and Worden, J. and Edwards, D.P. and Francis, G.L. and Worden, H.M. and Clerbaux, C. and Hadji-Lazaro, J. and Hurtmans, D.},
  title = {Extending the satellite data record of tropospheric ozone profiles from Aura-TES to MetOp-IASI: Characterisation of optimal estimation retrievals},
  journal = {Atmospheric Measurement Techniques},
  year = {2014},
  volume = {7},
  pages = {4223-4236},
  doi = {10.5194/amt-7-4223-2014}
}
Abstract: This study presents the joint H2 16O and HDO retrieval from Infrared Atmospheric Sounding Interferometer (IASI) spectra over western Siberia. IASI is an instrument on board the MetOp-A European satellite. The global coverage of the instrument and the good signal-to-noise ratio allow us to provide information on δD over this remote region. We show that IASI measurements may be used to estimate integrated δD between the surface and 3 km altitude or from 1 to 5 km depending on the thermal contrast, with observational errors lower than 4% and 7 %, respectively. The retrieved data are compared to simulations from an isotopic general circulation model, LMDZ-iso for 2011. The satellite measurements and the model agree well and they reproduce well the seasonal and day-to-day variations for δD, presenting a good correlation (r up to 0.8 with the smoothed data in summer). The IASI-based retrievals also show the seasonal variation of the specific humidity in both altitude ranges. © Author(s) 2014.
BibTeX:
@article{Pommier2014,
  author = {Pommier, M. and Lacour, J.-L. and Risi, C. and Bréon, F.M. and Clerbaux, C. and Coheur, P.-F. and Gribanov, K. and Hurtmans, D. and Jouzel, J. and Zakharov, V.},
  title = {Observation of tropospheric δd by IASI over western Siberia: Comparison with a general circulation model},
  journal = {Atmospheric Measurement Techniques},
  year = {2014},
  volume = {7},
  pages = {1581-1595},
  doi = {10.5194/amt-7-1581-2014}
}
Abstract: Over the Mediterranean region, elevated tropospheric ozone (O3) values are recorded, especially in summer. We use the thermal Infrared Atmospheric Sounding Interferometer (IASI) and the Weather Research and Forecasting Model with Chemistry (WRF-Chem) to understand and interpret the factors and emission sources responsible for the high O3concentrations observed in the Mediterranean troposphere. Six years (2008-2013) of IASI data have been analyzed and results show consistent maxima during summer, with an increase of up to 22% in the [0-8] km O3column in the eastern part of the basin compared to the middle of the basin. We focus on summer 2010 to investigate the processes that contribute to these summer maxima. Using two modeled O3tracers (inflow to the model domain and local anthropogenic emissions), we show that, between the surface and 2 km, O3is mostly formed from anthropogenic emissions, while above 4 km it is mostly transported from outside the domain or from stratospheric origins. Evidence of stratosphere-to-troposphere exchange (STE) events in the eastern part of the basin is shown, and corresponds to a low water vapor mixing ratio and high potential vorticity. © 2014 Author(s).
BibTeX:
@article{Safieddine2014,
  author = {Safieddine, S. and Boynard, A. and Coheur, P.-F. and Hurtmans, D. and Pfister, G. and Quennehen, B. and Thomas, J.L. and Raut, J.-C. and Law, K.S. and Klimont, Z. and Hadji-Lazaro, J. and George, M. and Clerbaux, C.},
  title = {Summertime tropospheric ozone assessment over the Mediterranean region using the thermal infrared IASI/MetOp sounder and the WRF-Chem model},
  journal = {Atmospheric Chemistry and Physics},
  year = {2014},
  volume = {14},
  pages = {10119-10131},
  doi = {10.5194/acp-14-10119-2014}
}
Abstract: Mt. Etna volcano in Italy is one of the most active degassing volcanoes worldwide, emitting a mean of 1.7 Mt/year of Sulphur Dioxide (SO2) in quiescent periods. In this work, SO2 measurements retrieved by Moderate Resolution Imaging Spectroradiometer (MODIS), hyper-spectral Infrared Atmospheric Sounding Interferometer (IASI) and the second Global Ozone Monitoring Experiment (GOME-2) data are compared with the ground-based data from the FLux Automatic MEasurement monitoring network (FLAME). Among the eighteen lava fountain episodes occurring at Mt. Etna in 2011, the 10 April paroxysmal event has been selected as a case-study for the simultaneous observation of the SO2 cloud by satellite and ground-based sensors. For each data-set two retrieval techniques were adopted and the measurements of SO2 mass and flux with their respective uncertainty were obtained. With respect to the FLAME SO2 mass of 4.5 Gg, MODIS, IASI and GOME-2 differ by about 10%, 15% and 30%, respectively. The SO2 flux correlation coefficient between MODIS and FLAME is 0.84. All the retrievals within the respective errors are in agreement with the ground-based measurements supporting the validity of these space measurements. © 2014, Editrice Compositori s.r.l. All rights reserved.
BibTeX:
@article{Spinetti2014,
  author = {Spinetti, C. and Salerno, G.G. and Caltabiano, T. and Carboni, E. and Clarisse, L. and Corradini, S. and Grainger, R.G. and Hedelt, P.A. and Koukouli, M.E. and Merucci, L. and Siddans, R. and Tampellini, L. and Theys, N. and Valks, P. and Zehner, C.},
  title = {Volcanic SO2 by UV-TIR satellite retrievals: Validation by using ground-based network at Mt. Etna},
  journal = {Annals of Geophysics},
  year = {2014},
  volume = {57},
  doi = {10.4401/ag-6641}
}
Abstract: Despite the developments in the global modelling of chemistry and of the parameterization of the physical processes, carbon monoxide (CO) concentrations remain underestimated during Northern Hemisphere (NH) winter by most state-of-the-art chemistry transport models. The consequential model bias can in principle originate from either an underestimation of CO sources or an overestimation of its sinks. We address both the role of surface sources and sinks with a series of MOZART (Model for Ozone And Related Tracers) model sensitivity studies for the year 2008 and compare our results to observational data from ground-based stations, satellite observations, and vertical profiles from measurements on passenger aircraft. In our base case simulation using MACCity (Monitoring Atmospheric Composition and Climate project) anthropogenic emissions, the near-surface CO mixing ratios are underestimated in the Northern Hemisphere by more than 20 ppb from December to April, with the largest bias of up to 75 ppb over Europe in January. An increase in global biomass burning or biogenic emissions of CO or volatile organic compounds (VOCs) is not able to reduce the annual course of the model bias and yields concentrations over the Southern Hemisphere which are too high. Raising global annual anthropogenic emissions with a simple scaling factor results in overestimations of surface mixing ratios in most regions all year round. Instead, our results indicate that anthropogenic CO and, possibly, VOC emissions in the MACCity inventory are too low for the industrialized countries only during winter and spring. Reasonable agreement with observations can only be achieved if the CO emissions are adjusted seasonally with regionally varying scaling factors. A part of the model bias could also be eliminated by exchanging the original resistance-type dry deposition scheme with a parameterization for CO uptake by oxidation from soil bacteria and microbes, which reduces the boreal winter dry deposition fluxes. The best match to surface observations, satellite retrievals, and aircraft observations was achieved when the modified dry deposition scheme was combined with increased wintertime road traffic emissions over Europe and North America (factors up to 4.5 and 2, respectively). One reason for the apparent underestimation of emissions may be an exaggerated downward trend in the Representative Concentration Pathway (RCP) 8.5 scenario in these regions between 2000 and 2010, as this scenario was used to extrapolate the MACCity emissions from their base year 2000. This factor is potentially amplified by a lack of knowledge about the seasonality of emissions. A methane lifetime of 9.7 yr for our basic model and 9.8 yr for the optimized simulation agrees well with current estimates of global OH, but we cannot fully exclude a potential effect from errors in the geographical and seasonal distribution of OH concentrations on the modelled CO. © Author(s) 2014. CC Attribution 3.0 License.
BibTeX:
@article{Stein2014,
  author = {Stein, O. and Schultz, M.G. and Bouarar, I. and Clark, H. and Huijnen, V. and Gaudel, A. and George, M. and Clerbaux, C.},
  title = {On the wintertime low bias of Northern Hemisphere carbon monoxide found in global model simulations},
  journal = {Atmospheric Chemistry and Physics},
  year = {2014},
  volume = {14},
  pages = {9295-9316},
  doi = {10.5194/acp-14-9295-2014}
}
Abstract: Volcanoes release large amounts of halogen species such as HCl and HBr, which can be converted into reactive halogens by heterogeneous photochemical reactions that are currently not fully characterized. Here we report on the first satellite detection of volcanic chlorine dioxide (OClO). Measurements were performed using the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography instrument for the ash-laden plume emitted after the 2011 eruption of Puyehue-Cordõn Caulle in Chile. We also identified volcanic BrO using the Ozone Monitoring Instrument, as well as enhanced HCl in data of the Microwave Limb Sounder instrument. These observations suggest that OClO was formed in the plume by the ClO + BrO reaction in presence of a large excess of ClO. The present satellite data set could help better understand reactive halogen chemistry in volcanic plumes and its impact on atmospheric composition. ©2013. American Geophysical Union. All Rights Reserved.
BibTeX:
@article{Theys2014,
  author = {Theys, N. and De Smedt, I. and Van Roozendael, M. and Froidevaux, L. and Clarisse, L. and Hendrick, F.},
  title = {First satellite detection of volcanic OClO after the eruption of Puyehue-Cordõn Caulle},
  journal = {Geophysical Research Letters},
  year = {2014},
  volume = {41},
  pages = {667-672},
  doi = {10.1002/2013GL058416}
}
Abstract: Ammonia (NH3) emissions in the atmosphere have increased substantially over the past decades, largely because of intensive livestock production and use of fertilizers. As a short-lived species, NH3 is highly variable in the atmosphere and its concentration is generally small, except near local sources. While ground-based measurements are possible, they are challenging and sparse. Advanced infrared sounders in orbit have recently demonstrated their capability to measure NH3, offering a new tool to refine global and regional budgets. In this paper we describe an improved retrieval scheme of NH3 total columns from the measurements of the Infrared Atmospheric Sounding Interferometer (IASI). It exploits the hyperspectral character of this instrument by using an extended spectral range (800-1200 cm-1) where NH3 is optically active. This scheme consists of the calculation of a dimensionless spectral index from the IASI level1C radiances, which is subsequently converted to a total NH3 column using look-up tables built from forward radiative transfer model simulations. We show how to retrieve the NH3 total columns from IASI quasi-globally and twice daily above both land and sea without large computational resources and with an improved detection limit. The retrieval also includes error characterization of the retrieved columns. Five years of IASI measurements (1 November 2007 to 31 October 2012) have been processed to acquire the first global and multiple-year data set of NH3 total columns, which are evaluated and compared to similar products from other retrieval methods. Spatial distributions from the five years data set are provided and analyzed at global and regional scales. In particular, we show the ability of this method to identify smaller emission sources than those previously reported, as well as transport patterns over the ocean. The five-year time series is further examined in terms of seasonality and interannual variability (in particular as a function of fire activity) separately for the Northern and Southern Hemispheres. © Author(s) 2014.
BibTeX:
@article{VanDamme2014a,
  author = {Van Damme, M. and Clarisse, L. and Heald, C.L. and Hurtmans, D. and Ngadi, Y. and Clerbaux, C. and Dolman, A.J. and Erisman, J.W. and Coheur, P.F.},
  title = {Global distributions, time series and error characterization of atmospheric ammonia (NH3) from IASI satellite observations},
  journal = {Atmospheric Chemistry and Physics},
  year = {2014},
  volume = {14},
  pages = {2905-2922},
  doi = {10.5194/acp-14-2905-2014}
}
Abstract: Monitoring ammonia (NH3) concentrations on a global to regional scale is a challenge. Due to the limited availability of reliable ground-based measurements, the determination of NH3 distributions generally relies on model calculations. Novel remotely sensed NH3 burdens provide valuable insights to complement traditional assessments for clear-sky conditions. This paper presents a first quantitative comparison between Atmospheric Sounding Interferometer (IASI) satellite observations and LOTOS-EUROS model results over Europe and Western Russia. A methodology to account for the variable retrieval sensitivity of the measurements is described. Four years of data (2008–2011) highlight three main agricultural hot spot areas in Europe: the Po Valley, the continental part of Northwestern Europe, and the Ebro Valley. The spatial comparison reveals a good overall agreement of the NH3 distributions not only in these source regions but also over remote areas and over sea when transport is observed. On average, the measured columns exceed the modeled ones, except for a few cases. Large discrepancies over several industrial areas in Eastern Europe and Russia point to underestimated emissions in the underlying inventories. The temporal analysis over the three hot spot areas reveals that the seasonality is well captured by the model when the lower sensitivity of the satellite measurements in the colder months is taken into account. Comparison of the daily time series indicates possible misrepresentations of the timing and magnitude of the emissions. Finally, specific attention to biomass burning events shows that modeled plumes are less spread out than the observed ones. This is confirmed for the 2010 Russian fires with a comparison using in situ observations. © 2014. American Geophysical Union. All Rights Reserved.
BibTeX:
@article{VanDamme2014,
  author = {Van Damme, M. and Wichink Kruit, R.J. and Schaap, M. and Clarisse, L. and Clerbaux, C. and Coheur, P.-F. and Dammers, E. and Dolman, A.J. and Erisman, J.W.},
  title = {Evaluating 4 years of atmospheric ammonia (NH3) over Europe using IASI satellite observations and LOTOS-EUROS model results},
  journal = {Journal of Geophysical Research},
  year = {2014},
  volume = {119},
  pages = {9549-9566},
  doi = {10.1002/2014JD021911}
}
Abstract: Vegetation fires emit large amounts of nitrogen compounds in the atmosphere, including ammonia (NH3). These emissions are still subject to large uncertainties. In this study, we analyze time series of monthly NH3 total columns (molec cm-2) from the IASI sounder on board MetOp-A satellite and their relation with MODIS fire radiative power (MW) measurements. We derive monthly NH3 emissions estimates for four regions accounting for a major part of the total area affected by fires (two in Africa, one in central South America and one in Southeast Asia), using a simplified box model, and we compare them to the emissions from both the GFEDv3.1 and GFASv1.0 biomass burning emission inventories. In order to strengthen the analysis, we perform a similar comparison for carbon monoxide (CO), also measured by IASI and for which the emission factors used in the inventories to convert biomass burned to trace gas emissions are thought to be more reliable. In general, a good correspondence between NH3 and CO columns and the FRP is found, especially for regions in central South America with correlation coefficients of 0.82 and 0.66, respectively. The comparison with the two biomass burning emission inventories GFASv1.0 and GFEDv3.1 shows good agreements, particularly in the time of the maximum of emissions for the central South America region and in the magnitude for the region of Africa south of the equator. We find evidence of significant non-pyrogenic emissions for the regions of Africa north of the equator (for NH3) and Southeast Asia (for NH3 and CO). On a yearly basis, total emissions calculated from IASI measurements for the four regions reproduce fairly well the interannual variability from the GFEDv3.1 and GFASv1.0 emissions inventories for NH3 but show values about 1.5-2 times higher than emissions given by the two biomass burning emission inventories, even when assuming a fairly long lifetime of 36 h for that species. © 2015 Elsevier Ltd.
BibTeX:
@article{Whitburn2014,
  author = {Whitburn, S. and Van Damme, M. and Kaiser, J.W. and Van Der Werf, G.R. and Turquety, S. and Hurtmans, D. and Clarisse, L. and Clerbaux, C. and Coheur, P.-F.},
  title = {Ammonia emissions in tropical biomass burning regions: Comparison between satellite-derived emissions and bottom-up fire inventories},
  journal = {Atmospheric Environment},
  year = {2014},
  volume = {121},
  pages = {42-54},
  doi = {10.1016/j.atmosenv.2015.03.015}
}
Abstract: Depending on the magnitude of their eruptions, volcanoes impact the atmosphere at various temporal and spatial scales. The volcanic source remains a major unknown to rigorously assess these impacts. At the scale of an eruption, the limited knowledge of source parameters, including time variations of erupted mass flux and emission profile, currently represents the greatest issue that limits the reliability of volcanic cloud forecasts. Today, a growing number of satellite and remote sensing observations of distant plumes are becoming available, bringing indirect information on these source terms. Here, we develop an inverse modelling approach combining satellite observations of the volcanic plume with an Eulerian regional chemistry-transport model (CHIMERE) to characterise the volcanic SO2 emissions during an eruptive crisis. The May 2010 eruption of Eyjafjallajökull is a perfect case study to apply this method as the volcano emitted substantial amounts of SO2 during more than a month. We take advantage of the SO2 column amounts provided by a vast set of IASI (Infrared Atmospheric Sounding Interferometer) satellite images to reconstruct retrospectively the time series of the mid-tropospheric SO2 flux emitted by the volcano with a temporal resolution of ∼2 h, spanning the period from 1 to 12 May 2010. We show that no a priori knowledge on the SO2 flux is required for this reconstruction. The initialisation of chemistry-transport modelling with this reconstructed source allows for reliable simulation of the evolution of the long-lived tropospheric SO2 cloud over thousands of kilometres. Heterogeneities within the plume, which mainly result from the temporal variability of the emissions, are correctly tracked over a timescale of a week. The robustness of our approach is also demonstrated by the broad similarities between the SO2 flux history determined by this study and the ash discharge behaviour estimated by other means during the phases of high explosive activity at Eyjafjallajö kull in May 2010. Finally, we show how a sequential IASI data assimilation allows for a substantial improvement in the forecasts of the location and concentration of the plume compared to an approach assuming constant flux at the source. As the SO2 flux is an important indicator of the volcanic activity, this approach is also of interest to monitor poorly instrumented volcanoes from space. © Author(s) 2013.
BibTeX:
@article{Boichu2013,
  author = {Boichu, M. and Menut, L. and Khvorostyanov, D. and Clarisse, L. and Clerbaux, C. and Turquety, S.},
  title = {Inverting for volcanic SO2 flux at high temporal resolution using spaceborne plume imagery and chemistry-transport modelling: the 2010 Eyjafjallajökull eruption case study},
  journal = {Atmospheric Chemistry and Physics},
  year = {2013},
  volume = {13},
  pages = {8569-8584},
  doi = {10.5194/acp-13-8569-2013}
}
Abstract: Atmospheric aerosols impact air quality and global climate. Space based measurements are the best way to observe their spatial and temporal distributions, and can also be used to gain better understanding of their chemical, physical and optical properties. Aerosol composition is the key parameter affecting the refractive index, which determines how much radiation is scattered and absorbed. Composition of aerosols is unfortunately not measured by state of the art satellite remote sounders. Here we use high resolution infrared measurements for aerosol type differentiation, exploiting, in that part of spectrum, the dependency of their refractive index on wavelength. We review existing detection methods and present a unified detection method based on linear discrimination analysis. We demonstrate this method on measurements of the Infrared Atmospheric Sounding Interferometer (IASI) and five different aerosol types, namely volcanic ash, windblown sand, sulfuric acid droplets, ammonium sulfate and smoke particles. We compare these with traditional MODIS AOD measurements. The detection of the last three types is unprecedented in the infrared in nadir mode, but is very promising, especially for sulfuric acid droplets which are detected in the lower troposphere and up to 6 months after injection in the upper troposphere/lower stratosphere. © 2013 Author(s).
BibTeX:
@article{Clarisse2013,
  author = {Clarisse, L. and Coheur, P.-F. and Prata, F. and Hadji-Lazaro, J. and Hurtmans, D. and Clerbaux, C.},
  title = {A unified approach to infrared aerosol remote sensing and type specification},
  journal = {Atmospheric Chemistry and Physics},
  year = {2013},
  volume = {13},
  pages = {2195-2221},
  doi = {10.5194/acp-13-2195-2013}
}
BibTeX:
@article{Clerbaux2013,
  author = {Clerbaux, C. and Crevoisier, C.},
  title = {New Directions: Infrared remote sensing of the troposphere from satellite: Less, but better},
  journal = {Atmospheric Environment},
  year = {2013},
  volume = {72},
  pages = {24-26},
  doi = {10.1016/j.atmosenv.2013.01.057}
}
Abstract: Hydrogen cyanide (HCN) and acetylene (C2H2) are ubiquitous atmospheric trace gases with medium lifetime, which are frequently used as indicators of combustion sources and as tracers for atmospheric transport and chemistry. Because of their weak infrared absorption, overlapped by the CO2 Q branch near 720 cm-1, nadir sounders have up to now failed to measure these gases routinely. Taking into account CO 2 line mixing, we provide for the first time extensive measurements of HCN and C2H2 total columns at Reunion Island (21° S, 55° E) and Jungfraujoch (46° N, 8° E) in 2009-2010 using observations from the Infrared Atmospheric Sounding Interferometer (IASI). A first order comparison with local ground-based Fourier transform infraRed (FTIR) measurements has been carried out allowing tests of seasonal consistency which is reasonably captured, except for HCN at Jungfraujoch. The IASI data shows a greater tendency to high C2H2 values. We also examine a nonspecific biomass burning plume over austral Africa and show that the emission ratios with respect to CO agree with previously reported values. © Author(s) 2013.
BibTeX:
@article{Duflot2013,
  author = {Duflot, V. and Hurtmans, D. and Clarisse, L. and R'honi, Y. and Vigouroux, C. and De Mazière, M. and Mahieu, E. and Servais, C. and Clerbaux, C. and Coheur, P.-F.},
  title = {Measurements of hydrogen cyanide (HCN) and acetylene (C2H 2) from the Infrared Atmospheric Sounding Interferometer (IASI)},
  journal = {Atmospheric Measurement Techniques},
  year = {2013},
  volume = {6},
  pages = {917-925},
  doi = {10.5194/amt-6-917-2013}
}
Abstract: Validation of ozone profiles measured from a nadir looking satellite instrument over Antarctica is a challenging task due to differences in their vertical sensitivity with ozonesonde measurements. In this paper, ozone observations provided by the Infrared Atmospheric Sounding Interferometer (IASI) instrument onboard the polar-orbiting satellite MetOp are compared with ozone profiles collected between August and October 2010 at McMurdo Station, Antarctica, during the Concordiasi measurement campaign. The main objective of the campaign was the satellite data validation. With this aim 20 zero-pressure sounding balloons carrying ozonesondes were launched during this period when the MetOp satellite was passing above McMurdo. This makes the dataset relevant for comparison, especially because the balloons covered the entire altitude range of IASI profiles. The validation methodology and the collocation criteria vary according to the availability of global positioning system auxiliary data with each electro-chemical cell ozonesonde observation. The relative mean difference is shown to depend on the vertical range investigated. The analysis shows a good agreement in the troposphere (below 10 km) and middle stratosphere (25-40 km), where the differences are lower than 10%. However a significant positive bias of about 10-26% is estimated in the lower stratosphere at 10-25 km, depending on altitude. The positive bias in the 10-25 km range is consistent with previously reported studies comparing in situ data with thermal infrared satellite measurements. This study allows for a better characterization of IASI-retrieved ozone over the polar region during ozone depletion/recovery processes. © Author(s) 2013.
BibTeX:
@article{Gazeaux2013,
  author = {Gazeaux, J. and Clerbaux, C. and George, M. and Hadji-Lazaro, J. and Kuttippurath, J. and Coheur, P.-F. and Hurtmans, D. and Deshler, T. and Kovilakam, M. and Campbell, P. and Guidard, V. and Rabier, F. and Thépaut, J.-N.},
  title = {Intercomparison of polar ozone profiles by IASI/MetOp sounder with 2010 Concordiasi ozonesonde observations},
  journal = {Atmospheric Measurement Techniques},
  year = {2013},
  volume = {6},
  pages = {613-620},
  doi = {10.5194/amt-6-613-2013}
}
Abstract: We present the results of total column measurements of CO, C2H6 and fine-mode aerosol optical depth (AOD) during the "Quantifying the impact of BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellites" (BORTAS-B) campaign over eastern Canada. Ground-based observations, using Fourier transform spectrometers (FTSs) and sun photometers, were carried out in July and August 2011. These measurements were taken in Halifax, Nova Scotia, which is an ideal location to monitor the outflow of boreal fires from North America, and also in Toronto, Ontario. Measurements of fine-mode AOD enhancements were highly correlated with enhancements in coincident trace gas (CO and C2H6) observations between 19 and 21 July 2011, which is typical for a smoke plume event. In this paper, we focus on the identification of the origin and the transport of this smoke plume. We use back trajectories calculated by the Canadian Meteorological Centre as well as FLEXPART forward trajectories to demonstrate that the enhanced CO, C2H6 and fine-mode AOD seen near Halifax and Toronto originated from forest fires in northwestern Ontario that occurred between 17 and 19 July 2011. In addition, total column measurements of CO from the satellite-borne Infrared Atmospheric Sounding Interferometer (IASI) have been used to trace the smoke plume and to confirm the origin of the CO enhancement. Furthermore, the enhancement ratio-that is, in this case equivalent to the emission ratio (ERC2H6/CO)-was estimated from these ground-based observations. These C2H6 emission results from boreal fires in northwestern Ontario agree well with C2H6 emission measurements from other boreal regions, and are relatively high compared to fires from other geographical regions. The ground-based CO and C2H6 observations were compared with outputs from the 3-D global chemical transport model GEOS-Chem, using the Fire Locating And Modeling of Burning Emissions (FLAMBE) inventory. Agreement within the stated measurement uncertainty (∼3% for CO and ∼8% for C2H6) was found for the magnitude of the enhancement of the CO and C2H6 total columns between the measured and modelled results. However, there is a small shift in time (of approximately 6 h) of arrival of the plume over Halifax between the results. © Author(s) 2013.
BibTeX:
@article{Griffin2013,
  author = {Griffin, D. and Walker, K.A. and Franklin, J.E. and Parrington, M. and Whaley, C. and Hopper, J. and Drummond, J.R. and Palmer, P.I. and Strong, K. and Duck, T.J. and Abboud, I. and Bernath, P.F. and Clerbaux, C. and Coheur, P.-F. and Curry, K.R. and Dan, L. and Hyer, E. and Kliever, J. and Lesins, G. and Maurice, M. and Saha, A. and Tereszchuk, K. and Weaver, D.},
  title = {Investigation of CO, C2H6 and aerosols in a boreal fire plume over eastern Canada during BORTAS 2011 using ground-and satellite-based observations and model simulations},
  journal = {Atmospheric Chemistry and Physics},
  year = {2013},
  volume = {13},
  pages = {10227-10241},
  doi = {10.5194/acp-13-10227-2013}
}
Abstract: An eight-year long reanalysis of atmospheric composition data covering the period 2003-2010 was constructed as part of the FP7-funded Monitoring Atmospheric Composition and Climate project by assimilating satellite data into a global model and data assimilation system. This reanalysis provides fields of chemically reactive gases, namely carbon monoxide, ozone, nitrogen oxides, and formaldehyde, as well as aerosols and greenhouse gases globally at a horizontal resolution of about 80 km for both the troposphere and the stratosphere. This paper describes the assimilation system for the reactive gases and presents validation results for the reactive gas analysis fields to document the data set and to give a first indication of its quality. Tropospheric CO values from the MACC reanalysis are on average 10-20% lower than routine observations from commercial aircrafts over airports through most of the troposphere, and have larger negative biases in the boundary layer at urban sites affected by air pollution, possibly due to an underestimation of CO or precursor emissions. Stratospheric ozone fields from the MACC reanalysis agree with ozonesondes and ACE-FTS data to within ±10% in most seasons and regions. In the troposphere the reanalysis shows biases of -5% to +10% with respect to ozonesondes and aircraft data in the extratropics, but has larger negative biases in the tropics. Area-averaged total column ozone agrees with ozone fields from a multi-sensor reanalysis data set to within a few percent. NO2 fields from the reanalysis show the right seasonality over polluted urban areas of the NH and over tropical biomass burning areas, but underestimate wintertime NO2 maxima over anthropogenic pollution regions and overestimate NO2 in northern and southern Africa during the tropical biomass burning seasons. Tropospheric HCHO is well simulated in the MACC reanalysis even though no satellite data are assimilated. It shows good agreement with independent SCIAMACHY retrievals over regions dominated by biogenic emissions with some anthropogenic input, such as the eastern US and China, and also over African regions influenced by biogenic sources and biomass burning. © Author(s) 2013.
BibTeX:
@article{Inness2013,
  author = {Inness, A. and Baier, F. and Benedetti, A. and Bouarar, I. and Chabrillat, S. and Clark, H. and Clerbaux, C. and Coheur, P. and Engelen, R.J. and Errera, Q. and Flemming, J. and George, M. and Granier, C. and Hadji-Lazaro, J. and Huijnen, V. and Hurtmans, D. and Jones, L. and Kaiser, J.W. and Kapsomenakis, J. and Lefever, K. and Leitão, J. and Razinger, M. and Richter, A. and Schultz, M.G. and Simmons, A.J. and Suttie, M. and Stein, O. and Thépaut, J.-N. and Thouret, V. and Vrekoussis, M. and Zerefos, C.},
  title = {The MACC reanalysis: An 8 yr data set of atmospheric composition},
  journal = {Atmospheric Chemistry and Physics},
  year = {2013},
  volume = {13},
  pages = {4073-4109},
  doi = {10.5194/acp-13-4073-2013}
}
Abstract: Aerosols from the Sarychev volcano eruption (Kuril Islands, northeast of Japan) were observed in the Arctic lower stratosphere a few days after the strongest SO2 injection which occurred on 15 and 16 June 2009. From the observations provided by the Infrared Atmospheric Sounding Interferometer (IASI) an estimated 0.9 Tg of sulphur dioxide was injected into the upper troposphere and lower stratosphere (UTLS). The resultant stratospheric sulphate aerosols were detected from satellites by the Optical Spectrograph and Infrared Imaging System (OSIRIS) limb sounder and by the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and from the surface by the Network for the Detection of Atmospheric Composition Changes (NDACC) lidar deployed at OHP (Observatoire de Haute-Provence, France). By the first week of July the aerosol plume had spread out over the entire Arctic region. The Sarychev-induced stratospheric aerosol over the Kiruna region (north of Sweden) was measured by the Stratospheric and Tropospheric Aerosol Counter (STAC) during eight balloon flights planned in August and September 2009. During this balloon campaign the Micro Radiomètre Ballon (MicroRADIBAL) and the Spectroscopie d'Absorption Lunaire pour l'Observation des Minoritaires Ozone et NOx (SALOMON) remote-sensing instruments also observed these aerosols. Aerosol concentrations returned to near-background levels by spring 2010. The effective radius, the surface area density (SAD), the aerosol extinction, and the total sulphur mass from STAC in situ measurements are enhanced with mean values in the range 0.15-0.21 μm, 5.5-14.7 μm2 cm-3, 5.5-29.5 × 10-4 km-1, and 4.9-12.6 × 10-10 kg[S] kg-1[air], respectively, between 14 km and 18 km. The observed and modelled e-folding time of sulphate aerosols from the Sarychev eruption is around 70-80 days, a value much shorter than the 12-14 months calculated for aerosols from the 1991 eruption of Mt Pinatubo. The OSIRIS stratospheric aerosol optical depth (AOD) at 750 nm is enhanced by a factor of 6, with a value of 0.02 in late July compared to 0.0035 before the eruption. The HadGEM2 and MIMOSA model outputs indicate that aerosol layers in polar region up to 14-15 km are largely modulated by stratosphere-troposphere exchange processes. The spatial extent of the Sarychev plume is well represented in the HadGEM2 model with lower altitudes of the plume being controlled by upper tropospheric troughs which displace the plume downward and upper altitudes around 18-20 km, in agreement with lidar observations. Good consistency is found between the HadGEM2 sulphur mass density and the value inferred from the STAC observations, with a maximum located about 1 km above the tropopause ranging from 1 to 2 × 10 -9 kg[S] kg-1[air], which is one order of magnitude higher than the background level. © Author(s) 2013.
BibTeX:
@article{Jegou2013,
  author = {Jégou, F. and Berthet, G. and Brogniez, C. and Renard, J.-B. and François, P. and Haywood, J.M. and Jones, A. and Bourgeois, Q. and Lurton, T. and Auriol, F. and Godin-Beekmann, S. and Guimbaud, C. and Krysztofiak, G. and Gaubicher, B. and Chartier, M. and Clarisse, L. and Clerbaux, C. and Balois, J.Y. and Verwaerde, C. and Daugeron, D.},
  title = {Stratospheric aerosols from the Sarychev volcano eruption in the 2009 Arctic summer},
  journal = {Atmospheric Chemistry and Physics},
  year = {2013},
  volume = {13},
  pages = {6533-6552},
  doi = {10.5194/acp-13-6533-2013}
}
Abstract: The fires around Moscow in July and August 2010 emitted a large amount of pollutants to the atmosphere. Here we estimate the carbon monoxide (CO) source strength of the Moscow fires in July and August by using the TM5-4DVAR system in combination with CO column observations of the Infrared Atmospheric Sounding Interferometer (IASI). It is shown that the IASI observations provide a strong constraint on the total emissions needed in the model. Irrespective of the prior emissions used, the optimised CO fire emission estimates from mid-July to mid-August 2010 amount to approximately 24TgCO. This estimate depends only weakly (< 15%) on the assumed diurnal variations and injection height of the emissions. However, the estimated emissions might depend on unaccounted model uncertainties such as vertical transport. Our emission estimate of 22-27 TgCO during roughly one month of intense burning is less than suggested by another recent study, but substantially larger than predicted by the bottom-up inventories. This latter discrepancy suggests that bottom-up emission estimates for extreme peat burning events require improvements. © Author(s) 2013.
BibTeX:
@article{Krol2013,
  author = {Krol, M. and Peters, W. and Hooghiemstra, P. and George, M. and Clerbaux, C. and Hurtmans, D. and McInerney, D. and Sedano, F. and Bergamaschi, P. and El Hajj, M. and Kaiser, J.W. and Fisher, D. and Yershov, V. and Muller, J.-P.},
  title = {How much CO was emitted by the 2010 fires around Moscow?},
  journal = {Atmospheric Chemistry and Physics},
  year = {2013},
  volume = {13},
  pages = {4737-4747},
  doi = {10.5194/acp-13-4737-2013}
}
Abstract: During the last decades, remote sensing sounders have demonstrated their capability for monitoring atmospheric composition and pollution. With now 5 years of continuous observations of IASI instrument, flying on board of MetOp-A platform, we are able to analyze long term variations of atmospheric molecules. This article involves new tendencies for CO and CO2 molecules based on IASI LIC radiances. Comparisons with total columns are also provided. © 2013 AIP Publishing LLC.
BibTeX:
@conference{Oudot2013,
  author = {Oudot, C. and Clerbaux, C. and Lazaro, J.H. and George, M. and Safieddine, S. and Clarisse, L. and Hurtmans, D. and Coheur, P.},
  title = {IASI/MetOp sounder contribution for atmospheric composition monitoring: 4-year study of radiance data},
  journal = {AIP Conference Proceedings},
  year = {2013},
  volume = {1531},
  pages = {212-215},
  doi = {10.1063/1.4804744}
}
Abstract: In July 2010, several hundred forest and peat fires broke out across central Russia during its hottest summer on record. Here, we analyze these wildfires using observations of the Infrared Atmospheric Sounding Interferometer (IASI). Carbon monoxide (CO), ammonia (NH3) and formic acid (HCOOH) total columns are presented for the year 2010. Maximum total columns were found to be one order (for CO and HCOOH) and two orders (for NH3) of magnitude larger than typical background values. The temporal evolution of NH3 and HCOOH enhancement ratios relative to CO are presented. Evidence of secondary formation of HCOOH is found, with enhancement ratios exceeding reported emission ratios in fresh plumes. We estimate the total emitted masses for the period July-August 2010 over the center of western Russia; they are 19-33 Tg (CO), 0.7-2.6 Tg (NH3) and 0.9-3.9 Tg (HCOOH). For NH3 and HCOOH, these quantities are comparable to what is emitted in the course of a whole year by all extratropical forest fires. © Author(s) 2013.
BibTeX:
@article{RHoni2013,
  author = {R'Honi, Y. and Clarisse, L. and Clerbaux, C. and Hurtmans, D. and Duflot, V. and Turquety, S. and Ngadi, Y. and Coheur, P.-F.},
  title = {Exceptional emissions of NH3 and HCOOH in the 2010 Russian wildfires},
  journal = {Atmospheric Chemistry and Physics},
  year = {2013},
  volume = {13},
  pages = {4171-4181},
  doi = {10.5194/acp-13-4171-2013}
}
Abstract: Tropospheric ozone (O3) columns in urban and rural regions as seen by the Infrared Atmospheric Sounding Interferometer (IASI) are analyzed along with the Global Ozone Monitoring Experiment (GOME-2) tropospheric nitrogen dioxide (NO2) columns. Results over nine cities of the Northern Hemisphere for the period 2008-2011 show a typical seasonal behavior of tropospheric O3, with a first maximum reached in late spring because of stratospheric intrusion mainly and a continuous rise till the summer because of the anthropogenic-based ozone production. Over the East Asian cities, a decrease in the O3 tropospheric column is detected during the monsoon period. Seasonal cycling of tropospheric NO2 shows consistent higher values during winter because of the higher anthropogenic sources and longer lifetime. In rural regions, a complex relation between the O3 and NO2 columns is found, with good correlation in summer and winter. O3 concentrations in rural sites are found to be comparable to those closest to the anthropogenic emission sources, with peak values in spring and summer. Furthermore, the effect of the reduction of pollutant emissions in the Beijing region during the Olympic Games of 2008 compared to the same summer period in the following 3 years is studied. GOME-2 NO2 measurements show a reduction up to 54% above Beijing during this period compared to the following 3 years. IASI O3 measurements show an increase of 12% during July 2008 followed by a decrease of 5-6% during the months of August and September. Key Points Study the seasonal variation of tropospheric ozone and nitrogen dioxideCompare between urban and rural tropospheric O3 and NO2Analyze the relationship between tropospheric NO2 and O3 in rural regions ©2013. American Geophysical Union. All Rights Reserved.
BibTeX:
@article{Safieddine2013,
  author = {Safieddine, S. and Clerbaux, C. and George, M. and Hadji-Lazaro, J. and Hurtmans, D. and Coheur, P.-F. and Wespes, C. and Loyola, D. and Valks, P. and Hao, N.},
  title = {Tropospheric ozone and nitrogen dioxide measurements in urban and rural regions as seen by IASI and GOME-2},
  journal = {Journal of Geophysical Research Atmospheres},
  year = {2013},
  volume = {118},
  pages = {10555-10566},
  doi = {10.1002/jgrd.50669}
}
Abstract: Sulfur concentrations have been measured in 28 melt inclusions (MIs) in plagioclase, clinopyroxene, and olivine crystals extracted from tephra produced during the explosive eruption of Grímsvötn in May 2011. The results are compared to sulfur concentrations in the groundmass glass in order to estimate the mass of sulfur brought to surface during the eruption. Satellite measurements yield order of magnitude lower sulfur ( 0.2 Tg) in the eruption plume than estimated from the difference between MI and the groundmass glass. This sulfur "deficit" is readily explained by sulfur adhering to tephra grains but principally by sulfide globules caused by basalt-sulfide melt exsolution before degassing. A mass balance calculation reveals that approximately  0.8 Tg of SO2 is present as globules, representing  50% of the total sulfur budget. Most of the sulfide globules likely reside at depth due to their elevated density, for potential later remobilization by new magma or hydrothermal circulation. Key Points H2S and SO2 degassing is estimated for the 2011 eruption of Grímsvötn Satellite-based SO2 mass loading is lower than from mineral melt inclusions Half of S resides as sulfide globules; 25% enter the stratosphere ©2013. American Geophysical Union. All Rights Reserved.
BibTeX:
@article{Sigmarsson2013,
  author = {Sigmarsson, O. and Haddadi, B. and Carn, S. and Moune, S. and Gudnason, J. and Yang, K. and Clarisse, L.},
  title = {The sulfur budget of the 2011 Grímsvötn eruption, Iceland},
  journal = {Geophysical Research Letters},
  year = {2013},
  volume = {40},
  pages = {6095-6100},
  doi = {10.1002/2013GL057760}
}
Abstract: Continuous carbon monoxide (CO) total column densities above the Universidad Nacional Autónoma de México (UNAM) campus in Mexico City have been derived from solar absorption infrared spectroscopic measurements since October 2007. Its diurnal evolution is used in the present study in conjunction with other ground-based and satellite data to develop a top-down emission estimate of the annual CO emission of the Mexico City Metropolitan Area (MCMA). The growth-rate of the total column around noon under low ventilation conditions is calculated and allows us to derive the average surface emission-flux at UNAM, while similar measurements taken at the edge of the MCMA in Tecámac provide information on background CO levels in the Mexico basin. Based on 3 yr of measurements, CO column measurements from the Infrared Atmospheric Sounding Interferometer (IASI) satellite instrument are used to reconstruct the spatial distribution of this anthropogenic pollutant over the MCMA. The agreement between the measured columns of the satellite and ground-based measurements is excellent, particularly when a comparison strategy based on time-displaced air masses is used. The annual emission of the Mexico Megacity is estimated to be (2.15 ± 0.5) Tg yr-1 for the year 2008, while the official inventory for that year reported 1.6 Tg yr -1. The difference is slightly higher than the conservative uncertainty estimated in this work suggesting that the emission might be underestimated by the conventional bottom-up method. A larger discrepancy is found in the spatial distribution of the emissions, when comparing the emission flux over UNAM (derived from the ground-based measurement) with that of the inventory integrated over a representative area. The methodology presented here represents a new and useful strategy to evaluate the contribution of megacities to the global anthropogenic gas emissions. Additionally, three different strategies to compare ground and space-based measurements above an inhomogeneous and strongly contaminated area like Mexico City are presented and discussed. © Author(s) 2013.
BibTeX:
@article{Stremme2013,
  author = {Stremme, W. and Grutter, M. and Rivera, C. and Bezanilla, A. and Garcia, A.R. and Ortega, I. and George, M. and Clerbaux, C. and Coheur, P.-F. and Hurtmans, D. and Hannigan, J.W. and Coffey, M.T.},
  title = {Top-down estimation of carbon monoxide emissions from the Mexico Megacity based on FTIR measurements from ground and space},
  journal = {Atmospheric Chemistry and Physics},
  year = {2013},
  volume = {13},
  pages = {1357-1376},
  doi = {10.5194/acp-13-1357-2013}
}
Abstract: Existing descriptions of bi-directional ammonia (NH3) land-atmosphere exchange incorporate temperature and moisture controls, and are beginning to be used in regional chemical transport models. However, such models have typically applied simpler emission factors to upscale the main NH3 emission terms. While this approach has successfully simulated the main spatial patterns on local to global scales, it fails to address the environment- and climate- dependence of emissions. To handle these issues, we outline the basis for a new modelling paradigm where both NH3 emissions and deposition are calculated online according to diurnal, seasonal and spatial differences in meteorology. We show how measurements reveal a strong, but complex pattern of climatic dependence, which is increasingly being characterized using ground-based NH3 monitoring and satellite observations, while advances in process-based modelling are illustrated for agricultural and natural sources, including a global application for seabird colonies. A future architecture for NH3 emission-deposition modelling is proposed that integrates the spatio-temporal interactions, and provides the necessary © 2013 The Author(s) Published by the Royal Society. All rights reserved.
BibTeX:
@article{Sutton2013,
  author = {Sutton, M.A. and Reis, S. and Riddick, S.N. and Dragosits, U. and Nemitz, E. and Theobald, M.R. and Tang, Y.S. and Braban, C.F. and Vieno, M. and Dore, A.J. and Mitchell, R.F. and Wanless, S. and Daunt, F. and Fowler, D. and Blackall, T.D. and Milford, C. and Flechard, C.R. and Loubet, B. and Massad, R. and Cellier, P. and Personne, E. and Coheur, P.F. and Clarisse, L. and Van Damme, M. and Ngadi, Y. and Clerbaux, C. and Skjøth, C.A. and Geels, C. and Hertel, O. and Kruit, R.J.W. and Pinder, R.W. and Bash, J.O. and Walker, J.T. and Simpson, D. and Horváth, L. and Misselbrook, T.H. and Bleeker, A. and Dentener, F. and de Vries, W.},
  title = {Towards a climate-dependent paradigm of ammonia emission and deposition},
  journal = {Philosophical Transactions of the Royal Society B: Biological Sciences},
  year = {2013},
  volume = {368},
  doi = {10.1098/rstb.2013.0166}
}
Abstract: To further our understanding of the effects of biomass burning emissions on atmospheric composition, the BORTAS campaign (BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellites) was conducted on 12 July to 3 August 2011 during the boreal forest fire season in Canada. The simultaneous aerial, ground and satellite measurement campaign sought to record instances of boreal biomass burning to measure the tropo-spheric volume mixing ratios (VMRs) of short- and long-lived trace molecular species from biomass burning emissions. The goal was to investigate the connection between the composition and the distribution of these pyrogenic outflows and their resulting perturbation to atmospheric chemistry, with particular focus on oxidant species to determine the overall impact on the oxidizing capacity of the free troposphere. Measurements of pyrogenic trace species in boreal biomass burning plumes were made by the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) onboard the Canadian Space Agency (CSA) SCISAT-1 satellite during the BORTAS campaign. Even though biomass burning emissions are typically confined to the boundary layer, outflows are often injected into the upper troposphere by isolated convection and fire-related convective processes, thus allowing space-borne instruments to measure these pyrogenic outflows. An extensive set of 14 molecules - CH 3OH, C2H2, C2H6, C 3H6O, CO, HCN, HCOOH, HNO3, H2CO, NO, NO2, OCS, O3, and PAN -have been analysed. Included in this analysis is the calculation of age-dependent sets of enhancement ratios for each of the species originating from fires in North America (Canada, Alaska) and Siberia for a period of up to 7 days. Ratio values for the shorter lived primary pyrogenic species decrease over time primarily due to oxidation by the OH radical as the plume ages and values for longer lived species such as HCN and C2H6 remain relatively unchanged. Increasing negative values are observed for the oxidant species, including O3, indicating a destruction process in the plume as it ages such that concentrations of the oxidant species have dropped below their off-plume values. Results from previous campaigns have indicated that values for the molar ratios of ΔO 3 / ΔCO obtained from the measurements of the pyrogenic outflow from boreal fires are highly variable and range from negative to positive, irrespective of plume age. This variability has been attributed to pollution effects where the pyrogenic outflows have mixed with either local urban NO x emissions or pyrogenic emissions from the long-range transport of older plumes, thus affecting the production of O3 within the plumes. The results from this study have identified another potential cause of the variability in O3 concentrations observed in the measurements of biomass burning emissions, where evidence of stratosphere-troposphere exchange due to the pyroconvective updrafts from fires has been identified. Perturbations caused by the lofted emissions in these fire-aided convective processes may result in the intrusion of stratospheric air masses into the free troposphere and subsequent mixing of stratospheric O3 into the pyrogenic outflows causing fluctuations in observed ΔO3/ΔCO molar ratios. © Author(s) 2013.
BibTeX:
@article{Tereszchuk2013,
  author = {Tereszchuk, K.A. and González Abad, G. and Clerbaux, C. and Hadji-Lazaro, J. and Hurtmans, D. and Coheur, P.-F. and Bernath, P.F.},
  title = {ACE-FTS observations of pyrogenic trace species in boreal biomass burning plumes during BORTAS},
  journal = {Atmospheric Chemistry and Physics},
  year = {2013},
  volume = {13},
  pages = {4529-4541},
  doi = {10.5194/acp-13-4529-2013}
}
Abstract: Sulphur dioxide (SO2) fluxes of active degassing volcanoes are routinely measured with ground-based equipment to characterize and monitor volcanic activity. SO2 of unmonitored volcanoes or from explosive volcanic eruptions, can be measured with satellites. However, remote-sensing methods based on absorption spectroscopy generally provide integrated amounts of already dispersed plumes of SO2 and satellite derived flux estimates are rarely reported. Here we review a number of different techniques to derive volcanic SO2 fluxes using satellite measurements of plumes of SO 2 and investigate the temporal evolution of the total emissions of SO2 for three very different volcanic events in 2011: Puyehue-Cordón Caulle (Chile), Nyamulagira (DR Congo) and Nabro (Eritrea). High spectral resolution satellite instruments operating both in the ultraviolet-visible (OMI/Aura and GOME-2/MetOp-A) and thermal infrared (IASI/MetOp-A) spectral ranges, and multispectral satellite instruments operating in the thermal infrared (MODIS/Terra-Aqua) are used. We show that satellite data can provide fluxes with a sampling of a day or less (few hours in the best case). Generally the flux results from the different methods are consistent, and we discuss the advantages and weaknesses of each technique. Although the primary objective of this study is the calculation of SO 2 fluxes, it also enables us to assess the consistency of the SO 2 products from the different sensors used. © 2013 Author(s).
BibTeX:
@article{Theys2013,
  author = {Theys, N. and Campion, R. and Clarisse, L. and Brenot, H. and Van Gent, J. and Dils, B. and Corradini, S. and Merucci, L. and Coheur, P.-F. and Van Roozendael, M. and Hurtmans, D. and Clerbaux, C. and Tait, S. and Ferrucci, F.},
  title = {Volcanic SO2 fluxes derived from satellite data: A survey using OMI, GOME-2, IASI and MODIS},
  journal = {Atmospheric Chemistry and Physics},
  year = {2013},
  volume = {13},
  pages = {5945-5968},
  doi = {10.5194/acp-13-5945-2013}
}
Abstract: We present a regional emission inventory constructed based on satellite observations of fire activity (MODIS) and the ORCHIDEE vegetation model, and its application to air quality forecasting. After a brief description of the variability of fire activity in the Euro-Mediterranean region during the past 8 years, a full evaluation of the emissions is performed for the case study of the summer of 2007, during the large Greek fires event. Therefore, regional simulations undertaken with the CHIMERE chemistry-transport model (CTM) are compared to surface and satellite observations of trace gases and aerosols. © Springer Science+Business Media Dordrecht 2014.
BibTeX:
@article{Turquety2013,
  author = {Turquety, S. and Messina, P. and Stromatas, S. and Anav, A. and Menut, L. and Bessagnet, B. and Péré, J.-C. and Drobinski, P. and Coheur, P.F. and Rhoni, Y. and Clerbaux, C. and Tanré, D.},
  title = {Impact of Fire Emissions on Air Quality in the Euro-Mediterranean Region},
  journal = {NATO Science for Peace and Security Series C: Environmental Security},
  year = {2013},
  volume = {137},
  pages = {363-367},
  doi = {10.1007/978-94-007-5577-2_61}
}
Abstract: Atmospheric carbon monoxide (CO) distributions are controlled by anthropogenic emissions, biomass burning, transport and oxidation by reaction with the hydroxyl radical (OH). Quantifying trends in CO is therefore important for understanding changes related to all of these contributions. Here we present a comprehensive record of satellite observations from 2000 through 2011 of total column CO using the available measurements from nadir-viewing thermal infrared instruments: MOPITT, AIRS, TES and IASI. We examine trends for CO in the Northern and Southern Hemispheres along with regional trends for Eastern China, Eastern USA, Europe and India. We find that all the satellite observations are consistent with a modest decreasing trend ∼-1 % yr-1 in total column CO over the Northern Hemisphere for this time period and a less significant, but still decreasing trend in the Southern Hemisphere. Although decreasing trends in the United States and Europe have been observed from surface CO measurements, we also find a decrease in CO over E. China that, to our knowledge, has not been reported previously. Some of the interannual variability in the observations can be explained by global fire emissions, but the overall decrease needs further study to understand the implications for changes in anthropogenic emissions. © 2013 Author(s).
BibTeX:
@article{Worden2013,
  author = {Worden, H.M. and Deeter, M.N. and Frankenberg, C. and George, M. and Nichitiu, F. and Worden, J. and Aben, I. and Bowman, K.W. and Clerbaux, C. and Coheur, P.F. and De Laat, A.T.J. and Detweiler, R. and Drummond, J.R. and Edwards, D.P. and Gille, J.C. and Hurtmans, D. and Luo, M. and Martínez-Alonso, S. and Massie, S. and Pfister, G. and Warner, J.X.},
  title = {Decadal record of satellite carbon monoxide observations},
  journal = {Atmospheric Chemistry and Physics},
  year = {2013},
  volume = {13},
  pages = {837-850},
  doi = {10.5194/acp-13-837-2013}
}
Abstract: Suspended particles play an important role in coastal waters by controlling to a large extent the variability of the water inherent optical properties (IOPs). In this study, focused on the complex waters of the Southern North Sea, the relationships between the concentration, composition and size of suspended particles and their optical properties (light absorption, and attenuation in the visible and near-infrared spectral regions) are investigated. Over a one-year period, field measurements were carried out along regular transects from the Belgian to the English coasts to cover a wide gradient of water masses. Results show that the area can be divided into three geographical zones, each one having specific biogeochemical and optical properties: Scheldt coastal zone (SCZ), Middle of the Southern North Sea (MSNS) and Thames coastal zone (TCZ). Concentrations of organic (inorganic) particles were always higher in the SCZ (TCZ). The MSNS was characterized by a high proportion of organic particles in low concentration. The spectral shape of particle attenuation reveals a wide range from negative to positive slopes. Particle size distributions reveal a power-law shape along the coasts (especially in the TCZ) and a bimodal distribution in the MSNS notably during the spring phytoplankton bloom. This bimodal size distribution and more precisely a size peak around 7 μm results in an unexpected negative spectral slope of the particle attenuation coefficient. Variations in the particulate mass-specific IOPs between the three regions were observed to predominate over seasonal variations. The implications in terms of inversion of IOPs into biogeochemical parameters, such as chlorophyll a and total suspended matter, in coastal waters are discussed. © 2012 Elsevier Ltd.
BibTeX:
@article{Astoreca2012,
  author = {Astoreca, R. and Doxaran, D. and Ruddick, K. and Rousseau, V. and Lancelot, C.},
  title = {Influence of suspended particle concentration, composition and size on the variability of inherent optical properties of the Southern North Sea},
  journal = {Continental Shelf Research},
  year = {2012},
  volume = {35},
  pages = {117-128},
  doi = {10.1016/j.csr.2012.01.007}
}
Abstract: Using an extended cavity diode laser referenced to a femtosecond frequency comb, the P(11) absorption line in the ν 1+ν 3 combination band of the most abundant isotopologue of pure acetylene was studied at temperatures of 296, 240, 200, 175, 165, 160, 155, and 150 K to determine pressure-dependent line shape parameters at these temperatures. The laser emission profile, the instrumental resolution, is a Lorentz function characterized by a half width at half the maximum emission (HWHM) of 8.3×10-6 cm-1 (or 250 kHz) for these measurements. Six collision models were tested in fitting the experimental data: Voigt, speed-dependent Voigt, Rautian-Sobel'man, Galatry, and two Rautian-Galatry hybrid models (with and without speed-dependence). Only the speed-dependent Voigt model was able to fit the data to the experimental noise level at all temperatures and for pressures between 3 and nearly 360 torr. The variations of the speed-dependent Voigt profile line shape parameters with temperature were also characterized, and this model accurately reproduces the observations over their entire range of temperature and pressure. © 2011 Springer-Verlag.
BibTeX:
@article{Cich2012,
  author = {Cich, M.J. and McRaven, C.P. and Lopez, G.V. and Sears, T.J. and Hurtmans, D. and Mantz, A.W.},
  title = {Temperature-dependent pressure broadened line shape measurements in the ν 1+ν 3 band of acetylene using a diode laser referenced to a frequency comb},
  journal = {Applied Physics B: Lasers and Optics},
  year = {2012},
  volume = {109},
  pages = {373-384},
  doi = {10.1007/s00340-011-4829-0}
}
Abstract: Thermal infrared sounding of sulphur dioxide (SO 2) from space has gained appreciation as a valuable complement to ultraviolet sounding. There are several strong absorption bands of SO 2 in the infrared, and atmospheric sounders, such as AIRS (Atmospheric Infrared Sounder), TES (Tropospheric Emission Spectrometer) and IASI (Infrared Atmospheric Sounding Interferometer) have the ability to globally monitor SO 2 abundances. Most of the observed SO 2 is found in volcanic plumes. In this paper we outline a novel algorithm for the sounding of SO 2 above ∼5 km altitude using high resolution infrared sounders and apply it to measurements of IASI. The main features of the algorithm are a wide applicable total column range (over 4 orders of magnitude, from 0.5 to 5000 dobson units), a low theoretical uncertainty (3-5%) and near real time applicability. We make an error analysis and demonstrate the algorithm on the recent eruptions of Sarychev, Kasatochi, Grimsvötn, Puyehue-Cordón Caulle and Nabro. © 2012 Author(s). CC Attribution 3.0 License.
BibTeX:
@article{Clarisse2012,
  author = {Clarisse, L. and Hurtmans, D. and Clerbaux, C. and Hadji-Lazaro, J. and Ngadi, Y. and Coheur, P.-F.},
  title = {Retrieval of sulphur dioxide from the infrared atmospheric sounding interferometer (IASI)},
  journal = {Atmospheric Measurement Techniques},
  year = {2012},
  volume = {5},
  pages = {581-594},
  doi = {10.5194/amt-5-581-2012}
}
Abstract: The IASI (Infrared Atmospheric Sounding Interferometer) nadir-looking thermal infrared sounder onboard MetOp-A enables the monitoring of atmospheric constituents on a global scale. This paper presents a quality assessment of IASI CO profiles retrieved by the two different retrieval algorithms SOFRID and FORLI, by an intercomparison with airborne in-situ CO profiles from the MOZAIC program for the 2008-2009 period. Lower (surface-480 hPa) and upper tropospheric partial column (480-225 hPa) comparisons as well as profile comparisons are made. The retrieval errors of the IASI products are less than 21% in the lower troposphere and less than 10% in the upper troposphere. A statistical analysis shows similar correlation coefficients for the two retrieval algorithms and smoothed MOZAIC of r ∼ 0.8 and r ∼ 0.7 in the lower and upper troposphere respectively. Comparison with smoothed MOZAIC data of the temporal variation of the CO profiles at the airports of Frankfurt and Windhoek demonstrates that the IASI products are able to capture the seasonal variability at these sites. At Frankfurt SOFRID (respectively FORLI) is positively biased by 10.5% (13.0%) compared to smoothed MOZAIC in the upper (lower) troposphere, and the limited sensitivity of the IASI instrument to the boundary layer when thermal contrast is low is identified. At Windhoek, the impact of the vegetation fires in Southern Africa from July to November is captured by both SOFRID and FORLI, with an overestimation of the CO background values (fire maxima) by SOFRID (FORLI) by 12.8% (10%). Profile comparisons at Frankfurt and Windhoek show that the largest discrepancies are found between the two IASI products and MOZAIC for the nighttime retrievals. © 2012 Author(s).
BibTeX:
@article{DeWachter2012,
  author = {De Wachter, E. and Barret, B. and Le Flochmoën, E. and Pavelin, E. and Matricardi, M. and Clerbaux, C. and Hadji-Lazaro, J. and George, M. and Hurtmans, D. and Coheur, P.-F. and Nedelec, P. and Cammas, J.P.},
  title = {Retrieval of MetOp-A/IASI CO profiles and validation with MOZAIC data},
  journal = {Atmospheric Measurement Techniques},
  year = {2012},
  volume = {5},
  pages = {2843-2857},
  doi = {10.5194/amt-5-2843-2012}
}
Abstract: Three scientific ozone products from the Infrared Atmospheric Sounding Interferometer (IASI) aboard MetOp-A, retrieved in three different research teams (LA, LATMOS/ULB, LISA) with different retrieval schemes, are characterized and validated using ozonesondes measurements. The characteristics of the products are analyzed in terms of retrieval sensitivity, systematic and random errors, and ability to retrieve the natural variability of ozone and focus on different partial columns from the lower troposphere up to 30 km. The validation covers the midlatitudes and the tropics and the period from January to December 2008. The products present degrees of freedom (DOF) in the troposphere between 1 and 1.2 on average in the midlatitudes and between 1 and 1.4 in the tropics. The DOF are distributed differently on the vertical depending on the profiles and the season: summer leading to a better sensitivity to the lower troposphere, as expected. The error estimates range between 10 and 20% from the lower tropospheric partial columns (0-6 km and 0-8 km for the midlatitudes and the tropics respectively) to the UTLS partial columns (8-16 km and 11-20 km for the midlatitudes and the tropics respectively) for all the products and are about 5% in the stratosphere (16-30 km) and for the column up to 30 km. The main feature that arises from the comparison with the ozonesondes is a systematic overestimation of ozone in the UTLS (between 10 and 25%) by the three products in the midlatitudes and the tropics, attributed to the moderate vertical resolution of IASI and possibly to spectroscopic inconsistencies. The ability of the products to reproduce natural variability of tropospheric ozone is fairly good and depends on the considered season and region. © 2012 Author(s).
BibTeX:
@article{Dufour2012,
  author = {Dufour, G. and Eremenko, M. and Griesfeller, A. and Barret, B. and Leflochmoën, E. and Clerbaux, C. and Hadji-Lazaro, J. and Coheur, P.-F. and Hurtmans, D.},
  title = {Validation of three different scientific ozone products retrieved from IASI spectra using ozonesondes},
  journal = {Atmospheric Measurement Techniques},
  year = {2012},
  volume = {5},
  pages = {611-630},
  doi = {10.5194/amt-5-611-2012}
}
Abstract: The global distribution of dust column burden derived from MODIS Deep Blue aerosol products is compared to NH 3 column burden retrieved from IASI infrared spectra. We found similarities in their spatial distributions, in particular their hot spots are often collocated over croplands and to a lesser extent pastures. Globally, we found 22% of dust burden collocated with NH 3, with only 1% difference between land-use databases. This confirms the importance of anthropogenic dust from agriculture. Regionally, the Indian subcontinent has the highest amount of dust mixed with NH 3 (26%), mostly over cropland and during the pre-monsoon season. North Africa represents 50% of total dust burden but accounts for only 4% of mixed dust, which is found over croplands and pastures in Sahel and the coastal region of the Mediterranean. In order to evaluate the radiative effect of this mixing on dust optical properties, we derive the mass extinction efficiency for various mixtures of dust and NH 3, using AERONET sunphotometers data. We found that for dusty days the coarse mode mass extinction efficiency decreases from 0.62 to 0.48 m 2 g -1 as NH 3 burden increases from 0 to 40 mg m -2. The fine mode extinction efficiency, ranging from 4 to 16 m 2 g -1, does not appear to depend on NH 3 concentration or relative humidity but rather on mineralogical composition and mixing with other aerosols. Our results imply that a significant amount of dust is already mixed with ammonium salt before its long range transport. This in turn will affect dust lifetime, and its interactions with radiation and cloud properties. © 2012 Author(s).
BibTeX:
@article{Ginoux2012,
  author = {Ginoux, P. and Clarisse, L. and Clerbaux, C. and Coheur, P.-F. and Dubovik, O. and Hsu, N.C. and Van Damme, M.},
  title = {Mixing of dust and NH 3 observed globally over anthropogenic dust sources},
  journal = {Atmospheric Chemistry and Physics},
  year = {2012},
  volume = {12},
  pages = {7351-7363},
  doi = {10.5194/acp-12-7351-2012}
}
Abstract: We use in situ observations from the Interagency Monitoring of PROtected Visual Environments (IMPROVE) network, the Midwest Ammonia Monitoring Project, 11 surface site campaigns as well as Infrared Atmospheric Sounding Interferometer (IASI) satellite measurements with the GEOS-Chem model to investigate inorganic aerosol loading and atmospheric ammonia concentrations over the United States. IASI observations suggest that current ammonia emissions are underestimated in California and in the springtime in the Midwest. In California this underestimate likely drives the underestimate in nitrate formation in the GEOS-Chem model. However in the remaining continental United States we find that the nitrate simulation is biased high (normalized mean bias &gt; Combining double low line 1.0) year-round, except in Spring (due to the underestimate in ammonia in this season). None of the uncertainties in precursor emissions, the uptake efficiency of N 2O 5 on aerosols, OH concentrations, the reaction rate for the formation of nitric acid, or the dry deposition velocity of nitric acid are able to explain this bias. We find that reducing nitric acid concentrations to 75% of their simulated values corrects the bias in nitrate (as well as ammonium) in the US. However the mechanism for this potential reduction is unclear and may be a combination of errors in chemistry, deposition and sub-grid near-surface gradients. This "updated" simulation reproduces PM and ammonia loading and captures the strong seasonal and spatial gradients in gas-particle partitioning across the United States. We estimate that nitrogen makes up 15-35% of inorganic fine PM mass over the US, and that this fraction is likely to increase in the coming decade, both with decreases in sulfur emissions and increases in ammonia emissions. © 2012 Author(s).
BibTeX:
@article{Heald2012,
  author = {Heald, C.L. and Collett Jr., J.L. and Lee, T. and Benedict, K.B. and Schwandner, F.M. and Li, Y. and Clarisse, L. and Hurtmans, D.R. and Van Damme, M. and Clerbaux, C. and Coheur, P.-F. and Philip, S. and Martin, R.V. and Pye, H.O.T.},
  title = {Atmospheric ammonia and particulate inorganic nitrogen over the United States},
  journal = {Atmospheric Chemistry and Physics},
  year = {2012},
  volume = {12},
  pages = {10295-10312},
  doi = {10.5194/acp-12-10295-2012}
}
Abstract: The UK Met Office's Numerical Atmospheric-dispersion Modeling Environment (NAME) is used both operationally and for research investigations. It has previously been used to model volcanic ash at the London Volcanic Ash Advisory Centre (VAAC), including that from the eruptions in Iceland of Eyjafjallajökull in 2010 and Grímsvtn in 2011. In this paper, the ability of NAME to model the release and dispersion of volcanic SO2, the chemical processes leading to the production of sulphate aerosol, and the subsequent dispersion of sulphate aerosol, has been investigated. Sensitivity tests were carried out to investigate the suitability of the NAME chemistry scheme for use in both the troposphere and the stratosphere. The eruptions of Sarychev in 2009, Kasatochi in 2008 and Eyjafjallajökull in 2010 were simulated and results for SO2 column density and sulphate aerosol optical depth (AOD) were compared with satellite retrievals. NAME results compare favorably with available observations in terms of both geographical distribution and magnitude for all three cases. The NAME modeled values of SO2 show a correlation of 0.8 with the corresponding observations for Sarychev. Ninety percent of modeled values of northern hemisphere averaged sulphate AOD are within a factor of 2 of those observed for Kasatochi and 71% are within a factor of 2 of those observed for Sarychev. Although significant uncertainties are present in both the model and observations, this work demonstrates that NAME's current chemistry scheme shows promise as a tool for modeling SO2 and sulphate from volcanoes. © 2012 by the American Geophysical Union.
BibTeX:
@article{Heard2012,
  author = {Heard, I.P.C. and Manning, A.J. and Haywood, J.M. and Witham, C. and Redington, A. and Jones, A. and Clarisse, L. and Bourassa, A.},
  title = {A comparison of atmospheric dispersion model predictions with observations of SO2 and sulphate aerosol from volcanic eruptions},
  journal = {Journal of Geophysical Research Atmospheres},
  year = {2012},
  volume = {117},
  article number = {D00U22},
  doi = {10.1029/2011JD016791}
}
Abstract: The first Infrared Atmospheric Sounding Interferometer (IASI) was launched in October 2006 on the European Organization for the Exploitation of Meteorological Satellites' (EUMETSAT) Meteorological Operation (MetOp)-A satellite. The instrument and its successors will continue to operate until 2020 on the current MetOp platform and two follow-on satellites. The stability of the instrument is monitored routinely by the CNES Technical Expertise Center, using onboard measurements, and by EUMETSAT, where stable, clear fields of view are compared with simulated radiances from numerical weather prediction model output. Routine monitoring of IASI data and calibration and validation activities by CNES and EUMETSAT ensure full characterization of the instrument and verify that the performance meets the requirements. In-depth evaluation is routinely performed by comparing IASI with other instruments, such as AVHRR and the High Resolution Infrared Radiation Sounder (HIRS) on the MetOp platform.
BibTeX:
@article{Hilton2012,
  author = {Hilton, F. and Armante, R. and August, T. and Barnet, C. and Bouchard, A. and Camy-Peyret, C. and Capelle, V. and Clarisse, L. and Clerbaux, C. and Coheur, P.-F. and Collard, A. and Crevoisier, C. and Dufour, G. and Edwards, D. and Faijan, F. and Fourrié, N. and Gambacorta, A. and Goldberg, M. and Guidard, V. and Hurtmans, D. and Illingworth, S. and Jacquinet-Husson, N. and Kerzenmacher, T. and Klaes, D. and Lavanant, L. and Masiello, G. and Matricardi, M. and McNally, A. and Newman, S. and Pavelin, E. and Payan, S. and Péquignot, E. and Peyridieu, S. and Phulpin, T. and Remedios, J. and Schlüssel, P. and Serio, C. and Strow, L. and Stubenrauch, C. and Taylor, J. and Tobin, D. and Wolf, W. and Zhou, D.},
  title = {Hyperspectral earth observation from IASI},
  journal = {Bulletin of the American Meteorological Society},
  year = {2012},
  volume = {93},
  pages = {347-370},
  doi = {10.1175/BAMS-D-11-00027.1}
}
Abstract: This paper lays down the theoretical bases and the methods used in the Fast Optimal Retrievals on Layers for IASI (FORLI) software, which is developed and maintained at the "Université Libre de Bruxelles" (ULB) with the support of the "Laboratoire Atmosphères, Milieux, Observations Spatiales" (LATMOS) to process radiance spectra from the Infrared Atmospheric Sounding Interferometer (IASI) in the perspective of local to global chemistry applications. The forward radiative transfer model (RTM) and the retrieval approaches are formulated and numerical approximations are described. The aim of FORLI is near-real-time provision of global scale concentrations of trace gases from IASI, either integrated over the altitude range of the atmosphere (total columns) or vertically resolved. To this end, FORLI uses precalculated table of absorbances. At the time of writing three gas-specific versions of this algorithm have been set up: FORLI-CO, FORLI-O 3 and FORLI-HNO 3. The performances of each are reviewed and illustrations of results and early validations are provided, making the link to recent scientific publications. In this paper we stress the challenges raised by near-real-time processing of IASI, shortly describe the processing chain set up at ULB and draw perspectives for future developments and applications. © 2012 Elsevier Ltd.
BibTeX:
@article{Hurtmans2012,
  author = {Hurtmans, D. and Coheur, P.-F. and Wespes, C. and Clarisse, L. and Scharf, O. and Clerbaux, C. and Hadji-Lazaro, J. and George, M. and Turquety, S.},
  title = {FORLI radiative transfer and retrieval code for IASI},
  journal = {Journal of Quantitative Spectroscopy and Radiative Transfer},
  year = {2012},
  volume = {113},
  pages = {1391-1408},
  doi = {10.1016/j.jqsrt.2012.02.036}
}
Abstract: Carbon monoxide (CO) is retrieved daily and globally from space-borne IASI radiance spectra using the Fast Optimal Retrievals on Layers for IASI (FORLI) software developed at the Université Libre de Bruxelles (ULB). The IASI CO total column product for 2008 from the most recent FORLI retrieval version (20100815) is evaluated using correlative CO profile products retrieved from ground-based solar absorption Fourier transform infrared (FTIR) observations at the following FTIR spectrometer sites from the Network for the Detection of Atmospheric Composition Change (NDACC): Ny-Ã..lesund, Kiruna, Bremen, Jungfraujoch, Izaña and Wollongong. In order to have good statistics for the comparisons, we included all IASI data from the same day, within a 100 km radius around the ground-based stations. The individual ground-based data were adjusted to the lowest altitude of the co-located IASI CO profiles. To account for the different vertical resolutions and sensitivities of the ground-based and satellite measurements, the averaging kernels associated with the various retrieved products have been used to properly smooth coincident data products. It has been found that the IASI CO total column products compare well on average with the co-located ground-based FTIR total columns at the selected NDACC sites and that there is no significant bias for the mean values at all stations. © 2012 Author(s).
BibTeX:
@article{Kerzenmacher2012,
  author = {Kerzenmacher, T. and Dils, B. and Kumps, N. and Blumenstock, T. and Clerbaux, C. and Coheur, P.-F. and Demoulin, P. and García, O. and George, M. and Griffith, D.W.T. and Hase, F. and Hadji-Lazaro, J. and Hurtmans, D. and Jones, N. and Mahieu, E. and Notholt, J. and Paton-Walsh, C. and Raffalski, U. and Ridder, T. and Schneider, M. and Servais, C. and De Mazière, M.},
  title = {Validation of IASI FORLI carbon monoxide retrievals using FTIR data from NDACC},
  journal = {Atmospheric Measurement Techniques},
  year = {2012},
  volume = {5},
  pages = {2751-2761},
  doi = {10.5194/amt-5-2751-2012}
}
Abstract: This work evaluates the IASI CO product against independent in-situ aircraft data from the MOZAIC program and the POLARCAT aircraft campaign. The validation is carried out by analysing the impact of assimilation of eight months of IASI CO columns retrieved for the period of May to December 2008 into the global chemistry transport model LMDz-INCA. A modelling system based on a sub-optimal Kalman filter was developed and a specific treatment that takes into account the representativeness of observations at the scale of the model grid is applied to the IASI CO columns and associated errors before their assimilation in the model. Comparisons of the assimilated CO profiles with in situ CO measurements indicate that the assimilation leads to a considerable improvement of the model simulations in the middle troposphere as compared with a control run with no assimilation. Model biases in the simulation of background values are reduced and improvement in the simulation of very high concentrations is observed. The improvement is due to the transport by the model of the information present in the IASI CO retrievals. Our analysis also shows the impact of assimilation of CO on the representation of transport into the Arctic region during the POLARCAT summer campaign. A considerable increase in CO mixing ratios over the Asian source region was observed when assimilation was used leading to much higher values of CO during the cross-pole transport episode. These higher values are in good agreement with data from the POLARCAT flights that sampled this plume. © 2012 Author(s).
BibTeX:
@article{Klonecki2012,
  author = {Klonecki, A. and Pommier, M. and Clerbaux, C. and Ancellet, G. and Cammas, J.-P. and Coheur, P.-F. and Cozic, A. and Diskin, G.S. and Hadji-Lazaro, J. and Hauglustaine, D.A. and Hurtmans, D. and Khattatov, B. and Lamarque, J.-F. and Law, K.S. and Nedelec, P. and Paris, J.-D. and Podolske, J.R. and Prunet, P. and Schlager, H. and Szopa, S. and Turquety, S.},
  title = {Assimilation of IASI satellite CO fields into a global chemistry transport model for validation against aircraft measurements},
  journal = {Atmospheric Chemistry and Physics},
  year = {2012},
  volume = {12},
  pages = {4493-4512},
  doi = {10.5194/acp-12-4493-2012}
}
Abstract: The SPIRALE and SWIR balloon-borne instruments were launched in the Arctic polar region (near Kiruna, Sweden, 67.9° N-21.1° E) during summer on 7 and 24 August 2009 and on 14 August 2009, respectively. The SPIRALE instrument performed in situ measurements of several trace gases including CO and O 3 at altitudes between 9 and 34 km, with very high vertical resolution (∼ 5 m). The SWIR-balloon instrument measured total and partial column of several species including CO. The CO stratospheric profile from SPIRALE for 7 August 2009 shows some specific structures with large concentrations in the low levels (potential temperatures between 320 and 380 K, i.e. 10-14 km height). These structures are not present in the CO vertical profile of SPIRALE for 24 August 2009, for which the volume mixing ratios are typical from polar latitudes (∼ 30 ppb). CO total columns retrieved from the IASI-MetOp satellite sounder for the three dates of flights are used to understand this CO variability. SPIRALE and SWIR CO partial columns between 9 and 34 km are compared, allowing us to confirm that the enhancement of CO is localised in the stratosphere. The measurements are also investigated in terms of CO:O3 correlations and using several modelling approaches (trajectory calculations, potential vorticity fields, results of chemistry transport model) in order to characterize the origin of the air masses sampled. The emission sources are qualified in terms of source type (fires, urban pollution) using NH3 and CO measurements from IASI-MetOp and fires detection from MODIS on board the TERRA/AQUA satellite. The results give strong evidence that the unusual abundance of CO on 7 August is due to surface pollution plumes from East Asia and North America transporting to the upper troposphere and then entering the lower stratosphere by isentropic advection. This study strengthens evidence that the composition of low polar stratosphere in summer may be affected by anthropogenic surface emissions through long-range transport. © 2012 Author(s).
BibTeX:
@article{Krysztofiak2012,
  author = {Krysztofiak, G. and Thiéblemont, R. and Huret, N. and Catoire, V. and Té, Y. and Jégou, F. and Coheur, P.F. and Clerbaux, C. and Payan, S. and Drouin, M.A. and Robert, C. and Jeseck, P. and Attié, J.-L. and Camy-Peyret, C.},
  title = {Detection in the summer polar stratosphere of pollution plume from East Asia and North America by balloon-borne in situ CO measurements},
  journal = {Atmospheric Chemistry and Physics},
  year = {2012},
  volume = {12},
  pages = {11889-11906},
  doi = {10.5194/acp-12-11889-2012}
}
Abstract: In this paper we retrieve atmospheric HDO, H2O concentrations and their ratio δD from IASI radiances spectra. Our method relies on an existing radiative transfer model (Atmosphit) and an optimal estimation inversion scheme, but goes further than our previous work by explicitly considering correlations between the two species. A global HDO and H 2O a priori profile together with a covariance matrix were built from daily LMDz-iso model simulations of HDO and H2O profiles over the whole globe and a whole year. The retrieval parameters are described and characterized in terms of errors. We show that IASI is mostly sensitive to δD in the middle troposphere and allows retrieving δD for an integrated 3-6 km column with an error of 38‰ on an individual measurement basis. We examine the performance of the retrieval to capture the temporal (seasonal and short-term) and spatial variations of δD for one year of measurement at two dedicated sites (Darwin and Izan∼a) and a latitudinal band from g-60° to 60° for a 15 day period in January. We report a generally good agreement between IASI and the model and indicate the capabilities of IASI to reproduce the large scale variations of δD (seasonal cycle and latitudinal gradient) with good accuracy. In particular, we show that there is no systematic significant bias in the retrieved δD values in comparison with the model, and that the retrieved variability is similar to the one in the model even though there are certain local differences. Moreover, the noticeable differences between IASI and the model are briefly examined and suggest modeling issues instead of retrieval effects. Finally, the results further reveal the unprecedented capabilities of IASI to capture short-term variations in δD, highlighting the added value of the sounder for monitoring hydrological processes. © 2012 Author(s).
BibTeX:
@article{Lacour2012,
  author = {Lacour, J.-L. and Risi, C. and Clarisse, L. and Bony, S. and Hurtmans, D. and Clerbaux, C. and Coheur, P.-F.},
  title = {Mid-tropospheric δd observations from IASI/MetOp at high spatial and temporal resolution},
  journal = {Atmospheric Chemistry and Physics},
  year = {2012},
  volume = {12},
  pages = {10817-10832},
  doi = {10.5194/acp-12-10817-2012}
}
Abstract: Volcanic degassing produces abundant H2O and CO2, as well as SO2, HCl, H2S, S2, H2, HF, CO, and SiF4. Volcanic SO2, HCl, and H2S have been detected from satellites in the past; the remaining species are analyzed in situ or using airborne instruments, with all the consequent limitations in safety and sampling, and at elevated costs. We report identification of high CO concentrations consistent with a volcanic origin (the 2010 Eyjafjallajkull and 2011 Grímsvtn eruptions in Iceland) in data from the Measurements of Pollution in the Troposphere instrument (MOPITT) onboard EOS/Terra. The high CO values coincide spatially and temporally with ash plumes emanating from the eruptive centers, with elevated SO2 and aerosol optical thickness, as well as with high CO values in data from the Infrared Atmospheric Sounding Interferometer (IASI), onboard MetOp-A. CO has a positive indirect radiative forcing; climate models currently do not account for volcanic CO emissions. Given global volcanic CO2 emissions between 130 and 440 Tg/year and volcanic CO:CO2 ratios from the literature, we estimate that average global volcanic CO emissions may be on the order of ∼5.5 Tg/year, equivalent to the CO emissions caused by combined fossil fuel and biofuel combustion in Australia. © 2012. American Geophysical Union. All Rights Reserved.
BibTeX:
@article{Martinez-Alonso2012,
  author = {Martínez-Alonso, S. and Deeter, M.N. and Worden, H.M. and Clerbaux, C. and Mao, D. and Gille, J.C.},
  title = {First satellite identification of volcanic carbon monoxide},
  journal = {Geophysical Research Letters},
  year = {2012},
  volume = {39},
  article number = {L21809},
  doi = {10.1029/2012GL053275}
}
Abstract: This study analyzes relationships between concentration of suspended particles represented by dry mass, [SPM], or area, [AC], and optical properties including particulate beam attenuation (cp), side scattering (bs), and backscattering (bbp), obtained from an intensive sampling program in coastal and offshore waters around Europe and French Guyana. First-order optical properties are driven by particle concentration with best predictions of [SPM] by bbp and bs, and of [AC] by cp. Second-order variability is investigated with respect to particle size, apparent density (dry weight-to-wet-volume ratio), and composition. Overall, the mass-specific particulate backscattering coefficient, bmp (=bbp: [SPM]), is relatively well constrained, with variability of a factor of 3-4. This coefficient is well correlated with particle composition, with inorganic particles having values about three times greater (brmp= 0.012 m2 g_1) than organic particles (brmp= 0.005 m2 g_1). The mass-specific particulate attenuation coefficient, cm (= cp: [SPM]), on the other hand, varies over one order of magnitude and is strongly driven (77% of the variability explained) by particle apparent density. In this data set particle size does not affect cm and affects b bmp only weakly in clear (case 1) waters, despite size variations over one order of magnitude. A significant fraction (40-60%) of the variability in bmp remains unexplained. Possible causes are the limitation of the measured size distributions to the 2-302-mm range and effects of particle shape and internal structure that affect bbp more than cp and were not accounted for. © 2012, by the Association for the Sciences of Limnology and Oceanography, Inc.
BibTeX:
@article{Nekermans2012,
  author = {Nekermans, G. and Loisel, H. and Meriaux, X. and Astoreca, R. and McKee, D.},
  title = {In situ variability of mass-specific beam attenuation and backscattering of marine particles with respect to particle size, density, and composition},
  journal = {Limnology and Oceanography},
  year = {2012},
  volume = {57},
  pages = {124-144},
  doi = {10.4319/lo.2011.57.1.0124}
}
Abstract: An extensive set of airborne and satellite observations of volcanic ash from the Eyjafjallajökull Icelandic eruption are analyzed for a case study on 17 May 2010. Data collected from particle scattering probes and backscatter lidar on the Facility for Airborne Atmospheric Measurements (FAAM) BAe 146 aircraft allow estimates of ash concentration to be derived. Using radiative transfer simulations we show that airborne and satellite infrared radiances can be accurately modeled based on the in situ measured size distribution and a mineral dust refractive index. Furthermore, airborne irradiance measurements in the 0.3-1.7 m range are well modeled with these properties. Retrievals of ash mass column loading using Infrared Atmospheric Sounding Interferometer (IASI) observations are shown to be in accord with lidar-derived mass estimates, giving for the first time an independent verification of a hyperspectral ash variational retrieval method. The agreement of the observed and modeled solar and terrestrial irradiances suggests a reasonable degree of radiative closure implying that the physical and optical properties of volcanic ash can be relatively well constrained using data from state-of-the-science airborne platforms such as the FAAM BAe 146 aircraft. Comparisons with IASI measurements during recent Grímsvötn and Puyehue volcanic eruptions demonstrate the importance of accurately specifying the refractive index when modeling the observed spectra.
BibTeX:
@article{Newman2012,
  author = {Newman, S.M. and Clarisse, L. and Hurtmans, D. and Marenco, F. and Johnson, B. and Turnbull, K. and Havemann, S. and Baran, A.J. and O'Sullivan, D. and Haywood, J.},
  title = {A case study of observations of volcanic ash from the Eyjafjallajökull eruption: 2. Airborne and satellite radiative measurements},
  journal = {Journal of Geophysical Research Atmospheres},
  year = {2012},
  volume = {117},
  article number = {D00U13},
  doi = {10.1029/2011JD016780}
}
Abstract: We have analysed the sensitivity of the tropospheric ozone distribution over North America and the North Atlantic to boreal biomass burning emissions during the summer of 2010 using the GEOS-Chem 3-D global tropospheric chemical transport model and observations from in situ and satellite instruments. We show that the model ozone distribution is consistent with observations from the Pico Mountain Observatory in the Azores, ozonesondes across Canada, and the Tropospheric Emission Spectrometer (TES) and Infrared Atmospheric Sounding Instrument (IASI) satellite instruments. Mean biases between the model and observed ozone mixing ratio in the free troposphere were less than 10 ppbv. We used the adjoint of GEOS-Chem to show the model ozone distribution in the free troposphere over Maritime Canada is largely sensitive to NOx emissions from biomass burning sources in Central Canada, lightning sources in the central US, and anthropogenic sources in the eastern US and south-eastern Canada. We also used the adjoint of GEOS-Chem to evaluate the Fire Locating And Monitoring of Burning Emissions (FLAMBE) inventory through assimilation of CO observations from the Measurements Of Pollution In The Troposphere (MOPITT) satellite instrument. The CO inversion showed that, on average, the FLAMBE emissions needed to be reduced to 89% of their original values, with scaling factors ranging from 12% to 102%, to fit the MOPITT observations in the boreal regions. Applying the CO scaling factors to all species emitted from boreal biomass burning sources led to a decrease of the model tropospheric distributions of CO, PAN, and NOx by as much as -20 ppbv, -50 pptv, and -20 pptv respectively. The modification of the biomass burning emission estimates reduced the model ozone distribution by approximately -3 ppbv (-8%) and on average improved the agreement of the model ozone distribution compared to the observations throughout the free troposphere, reducing the mean model bias from 5.5 to 4.0 ppbv for the Pico Mountain Observatory, 3.0 to 0.9 ppbv for ozonesondes, 2.0 to 0.9 ppbv for TES, and 2.8 to 1.4 ppbv for IASI. © 2012 Author(s).
BibTeX:
@article{Parrington2012,
  author = {Parrington, M. and Palmer, P.I. and Henze, D.K. and Tarasick, D.W. and Hyer, E.J. and Owen, R.C. and Helmig, D. and Clerbaux, C. and Bowman, K.W. and Deeter, M.N. and Barratt, E.M. and Coheur, P.-F. and Hurtmans, D. and Jiang, Z. and George, M. and Worden, J.R.},
  title = {The influence of boreal biomass burning emissions on the distribution of tropospheric ozone over North America and the North Atlantic during 2010},
  journal = {Atmospheric Chemistry and Physics},
  year = {2012},
  volume = {12},
  pages = {2077-2098},
  doi = {10.5194/acp-12-2077-2012}
}
Abstract: Ozone data retrieved in the Arctic region from infrared radiance spectra recorded by the Infrared Atmospheric Sounding Interferometer (IASI) on board the MetOp-A European satellite are presented. They are compared with in situ and lidar observations obtained during a series of aircraft measurement campaigns as part of the International Polar Year POLARCAT activities in spring and summer 2008. Different air masses were sampled during the campaigns including clean air, polluted plumes originating from anthropogenic sources, forest fire plumes from the three northern continents, and stratospheric-influenced air masses. The comparison between IASI O 3 [0-8 km], [0-12 km] partial columns and profiles with collocated aircraft observations is achieved by taking into account the different sensitivity and geometry of the sounding instruments. A detailed analysis is provided and the agreement is discussed in terms of vertical sensitivity and surface properties at the location of the observations. Overall, IASI O3 profiles are found to be in relatively good agreement with smoothed in situ and lidar profiles in the free troposphere with differences of less than 40% (25% over sea for both seasons) and 10%, respectively. The correlation between IASI O 3 retrieved partial columns and the smoothed aircraft partial columns is good with DC-8 in situ data in spring over North America (r= Combining double low line 0.68), and over Greenland with ATR-42 lidar measurements in summer (r= Combining double low line 0.67). Correlations with other data are less significant highlighting the difficulty of IASI to capture precisely the O 3 variability in the Arctic upper troposphere and lower stratosphere (UTLS). This is particularly noted in comparison with the [0-12 km] partial columns. The IASI [0-8 km] partial columns display a low negative bias (by less than 26% over snow) compared to columns derived from in situ measurements. Despite the relatively high biases of the IASI retrievals in the Arctic UTLS, our analysis shows that IASI can be used to identify, using O 3/CO ratios, stratospheric intrusions. © 2012 Author(s).
BibTeX:
@article{Pommier2012,
  author = {Pommier, M. and Clerbaux, C. and Law, K.S. and Ancellet, G. and Bernath, P. and Coheur, P.-F. and Hadji-Lazaro, J. and Hurtmans, D. and Nédélec, P. and Paris, J.-D. and Ravetta, F. and Ryerson, T.B. and Schlager, H. and Weinheimer, A.J.},
  title = {Analysis of IASI tropospheric O3 data over the Arctic during POLARCAT campaigns in 2008},
  journal = {Atmospheric Chemistry and Physics},
  year = {2012},
  volume = {12},
  doi = {10.5194/acp-12-7371-2012}
}
Abstract: In this study we have retrieved the self-broadened widths, self-pressure-induced shifts, and Dicke narrowing coefficients for 20 R-branch transitions in the v1+v2+v4+v5 band of acetylene. The spectra were recorded using a three-channel diode laser spectrometer, a temperature-controlled cell of fixed length and a second, room temperature cell. The soft collision (Galatry) and hard collision (Rautian) profiles with inclusion of line mixing effects were used to retrieve the line parameters. We determined the temperature dependencies for line broadening, shift, and Dicke narrowing coefficients. We performed comparisons between our retrieved line parameters and published line parameters for acetylene transitions. © 2012 Taylor and Francis.
BibTeX:
@article{Povey2012,
  author = {Povey, C. and Predoi-Cross, A. and Hurtmans, D.R.},
  title = {Low-pressure line shape study of acetylene transitions in the v1 + v2 + v4 + v5 band over a range of temperatures},
  journal = {Molecular Physics},
  year = {2012},
  volume = {110},
  pages = {2633-2644},
  doi = {10.1080/00268976.2012.705908}
}
Abstract: N2-broadened line widths and N2-pressure induced line shifts have been measured for transitions in the v1+v3 band of acetylene at seven temperatures in the range 213-333K to obtain the temperature dependences of broadening and shift coefficients. For the room-temperature spectra the line mixing effects have been also investigated. The Voigt and hard-collision line profile models were used to retrieve the line parameters. All spectra were recorded using a 3-channel tuneable diode laser spectrometer. The line-broadening and line-shifting coefficients as well as their temperature-dependence parameters have been also evaluated theoretically, in the frame of a semi-classical approach based on an exponential representation of the scattering operator, an intermolecular potential composed of electrostatic quadrupole-quadrupole and pairwise atom-atom interactions as well as on exact trajectories driven by an effective isotropic potential. © 2012 Taylor and Francis.
BibTeX:
@article{Rozario2012,
  author = {Rozario, H. and Garber, J. and Povey, C. and Hurtmans, D. and Buldyreva, J. and Predoi-Cross, A.},
  title = {Experimental and theoretical study of N2-broadened acetylene line parameters in the v1+v3 band over a range of temperatures},
  journal = {Molecular Physics},
  year = {2012},
  volume = {110},
  pages = {2645-2663},
  doi = {10.1080/00268976.2012.720040}
}
Abstract: Measurements of ozone vertical profiles are valuable for the evaluation of atmospheric chemistry models and contribute to the understanding of the processes controlling the distribution of tropospheric ozone. The longest record of ozone vertical profiles is provided by ozone sondes, which have a typical frequency of 4 to 12 profiles a month. Here we quantify the uncertainty introduced by low frequency sampling in the determination of means and trends. To do this, the high frequency MOZAIC (Measurements of OZone, water vapor, carbon monoxide and nitrogen oxides by in-service AIrbus airCraft) profiles over airports, such as Frankfurt, have been subsampled at two typical ozone sonde frequencies of 4 and 12 profiles per month. We found the lowest sampling uncertainty on seasonal means at 700 hPa over Frankfurt, with around 5% for a frequency of 12 profiles per month and 10% for a 4 profile-a-month frequency. However the uncertainty can reach up to 15 and 29% at the lowest altitude levels. As a consequence, the sampling uncertainty at the lowest frequency could be higher than the typical 10% accuracy of the ozone sondes and should be carefully considered for observation comparison and model evaluation. We found that the 95% confidence limit on the seasonal mean derived from the subsample created is similar to the sampling uncertainty and suggest to use it as an estimate of the sampling uncertainty. Similar results are found at six other Northern Hemisphere sites. We show that the sampling substantially impacts on the inter-annual variability and the trend derived over the period 1998-2008 both in magnitude and in sign throughout the troposphere. Also, a tropical case is discussed using the MOZAIC profiles taken over Windhoek, Namibia between 2005 and 2008. For this site, we found that the sampling uncertainty in the free troposphere is around 8 and 12% at 12 and 4 profiles a month respectively. © 2012 Author(s).
BibTeX:
@article{Saunois2012,
  author = {Saunois, M. and Emmons, L. and Lamarque, J.-F. and Tilmes, S. and Wespes, C. and Thouret, V. and Schultz, M.},
  title = {Impact of sampling frequency in the analysis of tropospheric ozone observations},
  journal = {Atmospheric Chemistry and Physics},
  year = {2012},
  volume = {12},
  pages = {6757-6773},
  doi = {10.5194/acp-12-6757-2012}
}
Abstract: In this paper we present a study of the ozone hole as observed by the Infrared Atmospheric Sounding Interferometer (IASI) on-board the MetOp-A European satellite platform from the beginning of data dissemination, August 2008, to the end of December 2010. Here we demonstrate IASI's ability to capture the seasonal characteristics of the ozone hole, in particular during polar night. We compare IASI ozone total columns and vertical profiles with those of the Global Ozone Monitoring Experiment 2 (GOME-2, also on-board MetOp-A) and electrochemical concentration cell (ECC) ozone sonde measurements. Total ozone column from IASI and GOME-2 were found to be in excellent agreement for this region with a correlation coefficient of 0.97, for September, October and November 2009. On average IASI exhibits a positive bias of approximately 7% compared to the GOME-2 measurements over the entire ozone hole period. Comparisons between IASI and ozone sonde measurements were also found to be in good agreement with the difference between both ozone profile measurements being less than ±30% over the altitude range of 0-40 km. The vertical structure of the ozone profile inside the ozone hole is captured remarkably well by IASI. © Author(s) 2012.
BibTeX:
@article{Scannell2012,
  author = {Scannell, C. and Hurtmans, D. and Boynard, A. and Hadji-Lazaro, J. and George, M. and Delcloo, A. and Tuinder, O. and Coheur, P.-F. and Clerbaux, C.},
  title = {Antarctic ozone hole as observed by IASI/MetOp for 2008-2010},
  journal = {Atmospheric Measurement Techniques},
  year = {2012},
  volume = {5},
  pages = {123-139},
  doi = {10.5194/amt-5-123-2012}
}
Abstract: Formic acid contributes significantly to acid rain in remote environments. Direct sources of formic acid include human activities, biomass burning and plant leaves. Aside from these direct sources, sunlight-induced oxidation of non-methane hydrocarbons (largely of biogenic origin) is probably the largest source. However, model simulations substantially underpredict atmospheric formic acid levels, indicating that not all sources have been included in the models. Here, we use satellite measurements of formic acid concentrations to constrain model simulations of the global formic acid budget. According to our simulations, 100- 120Tg of formic acid is produced annually, which is two to three times more than that estimated from known sources. We show that 90% of the formic acid produced is biogenic in origin, and largely sourced from tropical and boreal forests. We suggest that terpenoids- volatile organic compounds released by plants- are the predominant precursors. Model comparisons with independent observations of formic acid strengthen our conclusions, and provide indirect validation for the satellite measurements. Finally, we show that the larger formic acid emissions have a substantial impact on rainwater acidity, especially over boreal forests in the summer, where formic acid reduces pH by 0.25- 0.5.
BibTeX:
@article{Stavrakou2012,
  author = {Stavrakou, T. and Müller, J.-F. and Peeters, J. and Razavi, A. and Clarisse, L. and Clerbaux, C. and Coheur, P.-F. and Hurtmans, D. and De Mazière, M. and Vigouroux, C. and Deutscher, N.M. and Griffith, D.W.T. and Jones, N. and Paton-Walsh, C.},
  title = {Satellite evidence for a large source of formic acid from boreal and tropical forests},
  journal = {Nature Geoscience},
  year = {2012},
  volume = {5},
  pages = {26-30},
  doi = {10.1038/ngeo1354}
}
Abstract: Merapi volcano (Indonesia) is one of the most active and hazardous volcanoes in the world. It is known for frequent small to moderate eruptions, pyroclastic flows produced by lava dome collapse, and the large population settled on and around the flanks of the volcano that is at risk. Its usual behavior for the last decades abruptly changed in late October and early November 2010, when the volcano produced its largest and most explosive eruptions in more than a century, displacing at least a third of a million people, and claiming nearly 400 lives. Despite the challenges involved in forecasting this 'hundred year eruption', we show that the magnitude of precursory signals (seismicity, ground deformation, gas emissions) was proportional to the large size and intensity of the eruption. In addition and for the first time, near-real-time satellite radar imagery played an equal role with seismic, geodetic, and gas observations in monitoring eruptive activity during a major volcanic crisis. The Indonesian Center of Volcanology and Geological Hazard Mitigation (CVGHM) issued timely forecasts of the magnitude of the eruption phases, saving 10,000-20,000 lives. In addition to reporting on aspects of the crisis management, we report the first synthesis of scientific observations of the eruption. Our monitoring and petrologic data show that the 2010 eruption was fed by rapid ascent of magma from depths ranging from 5 to 30km. Magma reached the surface with variable gas content resulting in alternating explosive and rapid effusive eruptions, and released a total of  0.44Tg of SO2. The eruptive behavior seems also related to the seismicity along a tectonic fault more than 40km from the volcano, highlighting both the complex stress pattern of the Merapi region of Java and the role of magmatic pressurization in activating regional faults. We suggest a dynamic triggering of the main explosions on 3 and 4 November by the passing seismic waves generated by regional earthquakes on these days. © 2012 Elsevier B.V.
BibTeX:
@article{Surono2012,
  author = {Surono and Jousset, P. and Pallister, J. and Boichu, M. and Buongiorno, M.F. and Budisantoso, A. and Costa, F. and Andreastuti, S. and Prata, F. and Schneider, D. and Clarisse, L. and Humaida, H. and Sumarti, S. and Bignami, C. and Griswold, J. and Carn, S. and Oppenheimer, C. and Lavigne, F.},
  title = {The 2010 explosive eruption of Java's Merapi volcano-A '100-year' event},
  journal = {Journal of Volcanology and Geothermal Research},
  year = {2012},
  volume = {241-242},
  pages = {121-135},
  doi = {10.1016/j.jvolgeores.2012.06.018}
}
Abstract: The characterization and the precise measurements of atmospheric pollutant's concentration are essential to improve the understanding and modeling of urban air pollution processes. The QualAir platform at the Université Pierre et Marie Curie (UPMC) is an experimental research platform dedicated to urban air quality and pollution studies. As one of the major instruments, the ground-based QualAir Fourier transform spectrometer (FTS) provides information on the air composition of a megacity like Paris, France. Operating in solar infrared absorption, it enables the monitoring of several important pollutants involved in tropospheric chemistry and atmospheric transport around the Ile de France region. Results on nitrous oxide (N 2O), methane (CH 4), and carbon monoxide (CO) will be presented in this paper, as well as the CO measurements comparison with satellite and in situ measurements showing the capabilities and strengths of this groundbased FTS with the other instruments of the QualAir platform. © 2012 American Meteorological Society.
BibTeX:
@article{Te2012,
  author = {Té, Y.V. and Dieudonné, E. and Jeseck, P. and Hase, F. and Hadji-Lazaro, J. and Clerbaux, C. and Ravetta, F. and Payan, S. and Pépin, I. and Hurtmans, D. and Pelon, J. and Camy-Peyret, C.},
  title = {Carbon monoxide urban emission monitoring: A ground-based FTIR case study},
  journal = {Journal of Atmospheric and Oceanic Technology},
  year = {2012},
  volume = {29},
  pages = {911-921},
  doi = {10.1175/JTECH-D-11-00040.1}
}
Abstract: The Eyjafjallajökull ash that crossed over Spain and Portugal on 6-12 May 2010 has been monitored by a set of operational sun photometer sites within AERONET-RIMA and satellite sensors. The sun photometer observations (aerosol optical depth, coarse mode concentrations) and ash products from IASI and SEVIRI satellite sensors, together with FLEXPART simulations of particle transport, allow identifying the volcanic aerosols. The aerosol columnar properties derived from inversions were investigated, indicating specific properties, especially regarding the absorption. The single scattering albedo was high (0.95 at 440nm) and nearly wavelength independent, although with slight decrease with wavelength. Other parameters, like the fine mode fraction of the volume size distributions (0.20-0.80) or the portion of spherical particles (15-90%), were very variable among the sites and indicated that the various ash clouds were inhomogeneous with respect to particle size and shape. © 2011 Elsevier Ltd.
BibTeX:
@article{Toledano2012,
  author = {Toledano, C. and Bennouna, Y. and Cachorro, V. and Ortiz de Galisteo, J.P. and Stohl, A. and Stebel, K. and Kristiansen, N.I. and Olmo, F.J. and Lyamani, H. and Obregón, M.A. and Estellés, V. and Wagner, F. and Baldasano, J.M. and González-Castanedo, Y. and Clarisse, L. and de Frutos, A.M.},
  title = {Aerosol properties of the Eyjafjallajökull ash derived from sun photometer and satellite observations over the Iberian Peninsula},
  journal = {Atmospheric Environment},
  year = {2012},
  volume = {48},
  pages = {22-32},
  doi = {10.1016/j.atmosenv.2011.09.072}
}
Abstract: Methanol retrievals from nadir-viewing space-based sensors offer powerful new information for quantifying methanol emissions on a global scale. Here we apply an ensemble of aircraft observations over North America to evaluate new methanol measurements from the Tropospheric Emission Spectrometer (TES) on the Aura satellite, and combine the TES data with observations from the Infrared Atmospheric Sounding Interferometer (IASI) on the MetOp-A satellite to investigate the seasonality of methanol emissions from northern midlatitude ecosystems. Using the GEOS-Chem chemical transport model as an intercomparison platform, we find that the TES retrieval performs well when the degrees of freedom for signal (DOFS) are above 0.5, in which case the model:TES regressions are generally consistent with the model:aircraft comparisons. Including retrievals with DOFS below 0.5 degrades the comparisons, as these are excessively influenced by the a priori. The comparisons suggest DOFS >0.5 as a minimum threshold for interpreting retrievals of trace gases with a weak tropospheric signal. We analyze one full year of satellite observations and find that GEOS-Chem, driven with MEGANv2.1 biogenic emissions, underestimates observed methanol concentrations throughout the midlatitudes in springtime, with the timing of the seasonal peak in model emissions 1-2 months too late. We attribute this discrepancy to an underestimate of emissions from new leaves in MEGAN, and apply the satellite data to better quantify the seasonal change in methanol emissions for midlatitude ecosystems. The derived parameters (relative emission factors of 11.0, 0.26, 0.12 and 3.0 for new, growing, mature, and old leaves, respectively, plus a leaf area index activity factor of 0.5 for expanding canopies with leaf area index <1.2) provide a more realistic simulation of seasonal methanol concentrations in midlatitudes on the basis of both the IASI and TES measurements. © 2012 Author(s).
BibTeX:
@article{Wells2012,
  author = {Wells, K.C. and Millet, D.B. and Hu, L. and Cady-Pereira, K.E. and Xiao, Y. and Shephard, M.W. and Clerbaux, C.L. and Clarisse, L. and Coheur, P.-F. and Apel, E.C. and De Gouw, J. and Warneke, C. and Singh, H.B. and Goldstein, A.H. and Sive, B.C.},
  title = {Tropospheric methanol observations from space: Retrieval evaluation and constraints on the seasonality of biogenic emissions},
  journal = {Atmospheric Chemistry and Physics},
  year = {2012},
  volume = {12},
  pages = {5897-5912},
  doi = {10.5194/acp-12-5897-2012}
}
Abstract: In this paper, we analyze tropospheric O3 together with HNO 3 during the POLARCAT (Polar Study using Aircraft, Remote Sensing, Surface Measurements and Models, of Climate, Chemistry, Aerosols, and Transport) program, combining observations and model results. Aircraft observations from the NASA ARCTAS (Arctic Research of the Composition of the Troposphere from Aircraft and Satellites) and NOAA ARCPAC (Aerosol, Radiation and Cloud Processes affecting Arctic Climate) campaigns during spring and summer of 2008 are used together with the Model for Ozone and Related Chemical Tracers, version 4 (MOZART-4) to assist in the interpretation of the observations in terms of the source attribution and transport of O 3 and HNO 3 into the Arctic (north of 60°N). The MOZART-4 simulations reproduce the aircraft observations generally well (within 15%), but some discrepancies in the model are identified and discussed. The observed correlation of O3 with HNO 3 is exploited to evaluate the MOZART-4 model performance for different air mass types (fresh plumes, free troposphere and stratospheric-contaminated air masses). Based on model simulations of O 3 and HNO 3 tagged by source type and region, we find that the anthropogenic pollution from the Northern Hemisphere is the dominant source of O 3 and HNO 3 in the Arctic at pressures greater than 400 hPa, and that the stratospheric influence is the principal contribution at pressures less 400 hPa. During the summer, intense Russian fire emissions contribute some amount to the tropospheric columns of both gases over the American sector of the Arctic. North American fire emissions (California and Canada) also show an important impact on tropospheric ozone in the Arctic boundary layer. Additional analysis of tropospheric O 3 measurements from ground-based FTIR and from the IASI satellite sounder made at the Eureka (Canada) and Thule (Greenland) polar sites during POLARCAT has been performed using the tagged contributions. It demonstrates the capability of these instruments for observing pollution at northern high latitudes. Differences between contributions from the sources to the tropospheric columns as measured by FTIR and IASI are discussed in terms of vertical sensitivity associated with these instruments. The first analysis of O 3 tropospheric columns observed by the IASI satellite instrument over the Arctic is also provided. Despite its limited vertical sensitivity in the lowermost atmospheric layers, we demonstrate that IASI is capable of detecting low-altitude pollution transported into the Arctic with some limitations. © 2012 Author(s).
BibTeX:
@article{Wespes2012,
  author = {Wespes, C. and Emmons, L. and Edwards, D.P. and Hannigan, J. and Hurtmans, D. and Saunois, M. and Coheur, P.-F. and Clerbaux, C. and Coffey, M.T. and Batchelor, R.L. and Lindenmaier, R. and Strong, K. and Weinheimer, A.J. and Nowak, J.B. and Ryerson, T.B. and Crounse, J.D. and Wennberg, P.O.},
  title = {Analysis of ozone and nitric acid in spring and summer Arctic pollution using aircraft, ground-based, satellite observations and MOZART-4 model: Source attribution and partitioning},
  journal = {Atmospheric Chemistry and Physics},
  year = {2012},
  volume = {12},
  pages = {237-259},
  doi = {10.5194/acp-12-237-2012}
}
Abstract: One of the most important atmospheric composition products derived from the first EUMETSAT Meteorological Operational satellite (MetOp-A) is the total ozone column (TOC). For this purpose, MetOp-A has two instruments on board: the Global Ozone Monitoring Experiment 2 (GOME-2) that retrieves the TOC data from the backscattered solar ultraviolet-visible (UV-Vis) radiance, and the Infrared Atmospheric Sounding Interferometer (IASI) that uses the thermal infrared radiance to derive TOC data. This paper focuses on the simultaneous validation of the TOC data provided by these two MetOp-A instruments using the measurements recorded by five well-calibrated Brewer UV spectrophotometers located at the Iberian Peninsula during the complete 2009. The results show an excellent correlation between the ground-based data and the GOME-2 and IASI satellite observations (R2 higher than 0.91). Differences between the ground-based and satellite TOC data show that the IASI instrument significantly overestimates the Brewer measurements (about 4.4% when all five ground-based stations are jointly used). In contrast, the GOME-2 instrument shows a slight underestimation ( 1.6%). In addition, the absolute relative differences between the Brewer and GOME-2 data are quite smaller (about a factor higher than 2) than the Brewer-IASI absolute differences. The satellite viewing geometry (solar zenith angle and the view zenith angle) has no significant influence on the Brewer-satellite relative differences. Moreover, the analysis of these relative differences with respect to the ground-based TOC data indicates that GOME-2 instrument presents a slight underestimation for high TOC values. Finally, the IASI-GOME-2 correlation is high (R2 0.92), but with a mean relative difference of about ±6% which could be associated with the bias between UV-Vis and infrared spectroscopy used in the retrieval processes. © 2011 Elsevier Inc.
BibTeX:
@article{Anton2011,
  author = {Antón, M. and Loyola, D. and Clerbaux, C. and López, M. and Vilaplana, J.M. and Bañón, M. and Hadji-Lazaro, J. and Valks, P. and Hao, N. and Zimmer, W. and Coheur, P.F. and Hurtmans, D. and Alados-Arboledas, L.},
  title = {Validation of the MetOp-A total ozone data from GOME-2 and IASI using reference ground-based measurements at the Iberian Peninsula},
  journal = {Remote Sensing of Environment},
  year = {2011},
  volume = {115},
  pages = {1380-1386},
  doi = {10.1016/j.rse.2011.01.018}
}
Abstract: Hydrogen sulphide (H2S) is one of the main trace gases released from volcanoes with yearly global emissions estimated between 1 and 37 Tg. With sulfur dioxide (SO2, 15-21 Tg/year), it dominates the volcanic sulfur budget, and the emission ratio H2S:SO2 is an important geochemical probe for studying source conditions, sulfur chemistry and magma-water interactions. Contrary to SO2, measurements of H 2S are sparse and difficult. Here we report the first measurements of a large H2S plume from space. Observations were made with the infrared sounder IASI of the volcanic plume released after the 7-8 August 2008 eruption of Kasatochi volcano. The eruption was characterized by 5 consecutive explosive events. The first events were phreatomagmatic producing a plume rich in water vapor and poor in ash and SO2. We show that the observed H2S plume, calculated at 29±10 kT with integrated columns exceeding 140±25 Dobson Units (DU), is likely associated with these first explosions. H2S:SO2 ratios with maximum values of 12±2 are found, representative of redox conditions in the hydrothermal envelop. With a detection threshold of 25 DU, future space observations of H2S plumes are certain. These will be important for improving the atmospheric sulfur budget and characterizing the H2S:SO2 fingerprint of different eruptions. Copyright 2011 by the American Geophysical Union.
BibTeX:
@article{Clarisse2011,
  author = {Clarisse, L. and Coheur, P.-F. and Chefdeville, S. and Lacour, J.-L. and Hurtmans, D. and Clerbaux, C.},
  title = {Infrared satellite observations of hydrogen sulfide in the volcanic plume of the August 2008 Kasatochi eruption},
  journal = {Geophysical Research Letters},
  year = {2011},
  volume = {38},
  article number = {L10804},
  doi = {10.1029/2011GL047402}
}
Abstract: Using 3 years worth of IASI (the Infrared Atmospheric Sounder Interferometer aboard METOP-A) measurements, we have identified 24 major events of uplift and transport of anthropogenic sulfur dioxide. These were all first observed over East Asia, and could be traced for over 60 hours. On 7 November 2010 a sulfur dioxide plume was observed over Northeast China and tracked for five days to North America. We discuss this event in detail with respect to build up; uplift and in-plume chemistry. We found a host of trace gas enhancements in the plume (SO2, CO, PAN, CH3OH, HCOOH and C2H2). A reasonable to very good agreement was found with MOZART-4 modeled ambient columns for all species except methanol, which was underestimated by the model by an order of magnitude. We calculate correlations of the different species and give observational evidence of secondary in-plume formation of methanol and PAN. Copyright 2011 by the American Geophysical Union.
BibTeX:
@article{Clarisse2011a,
  author = {Clarisse, L. and Fromm, M. and Ngadi, Y. and Emmons, L. and Clerbaux, C. and Hurtmans, D. and Coheur, P.-F.},
  title = {Intercontinental transport of anthropogenic sulfur dioxide and other pollutants: An infrared remote sensing case study},
  journal = {Geophysical Research Letters},
  year = {2011},
  volume = {38},
  article number = {L19806},
  doi = {10.1029/2011GL048976}
}
Abstract: [1] Thermal infrared nadir sounders are ideal for observing total columns or vertical profiles of atmospheric gases such as water, carbon dioxide and ozone. High resolution sounders with a spectral resolution below 5 cm -1 can distinguish fine spectral features of trace gases. Forty years after the launch of the first hyperspectral sounder IRIS, we have now several state of the art instruments in orbit, with improved instrumental specifications. In this letter we give an overview of the trace gases which have been observed by infrared nadir sounders, focusing on new observations of the Infrared Atmospheric Sounding Interferometer (IASI). We present typical observations of 14 rare reactive trace gas species. Several species are reported here for the first time in nadir view, including nitrous acid, furan, acetylene, propylene, acetic acid, formaldehyde and hydrogen cyanide, observations which were made in a pyrocumulus cloud from the Australian bush fires of February 2009. Being able to observe this large number of reactive trace gases will likely improve our knowledge of source emissions and their impact on the environment and climate.
BibTeX:
@article{Clarisse2011b,
  author = {Clarisse, L. and R'Honi, Y. and Coheur, P.-F. and Hurtmans, D. and Clerbaux, C.},
  title = {Thermal infrared nadir observations of 24 atmospheric gases},
  journal = {Geophysical Research Letters},
  year = {2011},
  volume = {38},
  article number = {L10802},
  doi = {10.1029/2011GL047271}
}
Abstract: We evaluate climatologies of upper tropospheric ozone and nitric acid retrieved from two satellite instruments (ACE-FTS and OSIRIS) with long-term in situ measurements from aircraft (MOZAIC, CR-AVE, PRE-AVE, PEM Tropics, and TC4) and ozonesondes. A global chemical transport model (GEOS-Chem) is used to guide the evaluation and to relate sparse in situ measurements with the satellite retrievals. Both satellite retrievals generally reproduce broad ozone features in the upper troposphere such as summer enhancements in the northern subtropics and larger concentrations over the tropical Atlantic versus the tropical Pacific. These comparisons indicate biases in annual, tropical mean ozone concentrations from both ACE-FTS (10-13%) and OSIRIS (5%) relative to aircraft and ozonesonde observations. More uncertain evidence suggests that nitric acid from ACE-FTS has a positive mean bias of 15%. We demonstrate that an upper limit on the ozone production efficiency in the upper troposphere can be determined using ACE-FTS satellite measurements of O3 and HNO3. The resulting value of 196 (+34, -61) mol/mol is in broad agreement with model simulations. Higher OPE values inferred from ACE-FTS over the tropical Pacific (249 (+21, -68) mol/mol) than the tropical Atlantic (146 (+16, -41) mol/mol) reflect increasing ozone production efficiency with decreasing pollution. This analysis indicates a new capability of satellite observations to provide insight into ozone production in the tropical troposphere. Copyright 2011 by the American Geophysical Union.
BibTeX:
@article{Cooper2011,
  author = {Cooper, M. and Martin, R.V. and Sauvage, B. and Boone, C.D. and Walker, K.A. and Bernath, P.F. and McLinden, C.A. and Degenstein, D.A. and Volz-Thomas, A. and Wespes, C.},
  title = {Evaluation of ACE-FTS and OSIRIS Satellite retrievals of ozone and nitric acid in the tropical upper troposphere: Application to ozone production efficiency},
  journal = {Journal of Geophysical Research Atmospheres},
  year = {2011},
  volume = {116},
  article number = {D12306},
  doi = {10.1029/2010JD015056}
}
Abstract: The Eyjafjallajökull volcano in Iceland erupted explosively on 14 April 2010, emitting a plume of ash into the atmosphere. The ash was transported from Iceland toward Europe where mostly cloud-free skies allowed ground-based lidars at Chilbolton in England and Leipzig in Germany to estimate the mass concentration in the ash cloud as it passed overhead. The UK Met Office's Numerical Atmospheric-dispersion Modeling Environment (NAME) has been used to simulate the evolution of the ash cloud from the Eyjafjallajökull volcano during the initial phase of the ash emissions, 14-16 April 2010. NAME captures the timing and sloped structure of the ash layer observed over Leipzig, close to the central axis of the ash cloud. Relatively small errors in the ash cloud position, probably caused by the cumulative effect of errors in the driving meteorology en route, result in a timing error at distances far from the central axis of the ash cloud. Taking the timing error into account, NAME is able to capture the sloped ash layer over the UK. Comparison of the lidar observations and NAME simulations has allowed an estimation of the plume height time series to be made. It is necessary to include in the model input the large variations in plume height in order to accurately predict the ash cloud structure at long range. Quantitative comparison with the mass concentrations at Leipzig and Chilbolton suggest that around 3% of the total emitted mass is transported as far as these sites by small (<100 μm diameter) ash particles. Copyright 2011 by the American Geophysical Union.
BibTeX:
@article{Dacre2011,
  author = {Dacre, H.F. and Grant, A.L.M. and Hogan, R.J. and Belcher, S.E. and Thomson, D.J. and Devenish, B.J. and Marenco, F. and Hort, M.C. and Haywood, J.M. and Ansmann, A. and Mattis, I. and Clarisse, L.},
  title = {Evaluating the structure and magnitude of the ash plume during the initial phase of the 2010 Eyjafjallajökull eruption using lidar observations and NAME simulations},
  journal = {Journal of Geophysical Research Atmospheres},
  year = {2011},
  volume = {116},
  article number = {D00U03},
  doi = {10.1029/2011JD015608}
}
Abstract: The Measurements of Pollution in the Troposphere (MOPITT) retrievals are used as top-down constraints in an inversion for global CO emissions, for the past 10 years (from March 2000 to December 2009), at 8 day and 3.75° × 2.75° (longitude, latitude) resolution. The method updates a standard prior inventory and yields large increments in terms of annual regional budgets and seasonality. Our validation strategy consists in comparing our posterior-modeled concentrations with several sets of independent measurements: surface measurements, aircraft, and satellite. The posterior emissions, with a global 10 year average of 1430 TgCO/yr, are 37% higher than the prior ones, built from the EDGAR 3.2 and the GFEDv2 inventories (1038 TgCO/yr on average). In addition, they present some significant seasonal variations in the Northern Hemisphere that are not present in our prior nor in others' major inventories. Our results also exhibit some large interannual variability due to biomass burning emissions, climate, and socioeconomic factors; CO emissions range from 1504 TgCO (in 2007) to 1318 TgCO (in 2009). Copyright 2011 by the American Geophysical Union.
BibTeX:
@article{Fortems-Cheiney2011,
  author = {Fortems-Cheiney, A. and Chevallier, F. and Pison, I. and Bousquet, P. and Szopa, S. and Deeter, M.N. and Clerbaux, C.},
  title = {Ten years of CO emissions as seen from Measurements of Pollution in the Troposphere (MOPITT)},
  journal = {Journal of Geophysical Research Atmospheres},
  year = {2011},
  volume = {116},
  article number = {D05304},
  doi = {10.1029/2010JD014416}
}
Abstract: We report measurements of self- and nitrogen-pressure broadening of the P(11) line in the ν1 + ν3 combination band of acetylene at 195 739.649 5135(80) GHz by absorption of radiation emitted by an extended cavity diode laser referenced to a femtosecond frequency comb. Broadening, shift and narrowing parameters were determined at 296 K. For the most appropriate, hard collision, model in units of cm-1/atm, we find 0.146317(27), 0.047271(104) and -0.0070819(22) for the acetylene self-broadening, narrowing and shift, and 0.081129(35), 0.022940(74) and -0.0088913(25) respectively, for the nitrogen-broadening parameters. The uncertainties are expressed as one standard deviation (in parenthesis) in units of the last digit reported. These parameters are 2-3 orders of magnitude more precise than those reported in previous measurements. Similar analyses of the experimental data using soft collision and simple Voigt lineshape models were made for comparison. © 2011 Elsevier Inc. All rights reserved.
BibTeX:
@article{McRaven2011,
  author = {McRaven, C.P. and Cich, M.J. and Lopez, G.V. and Sears, T.J. and Hurtmans, D. and Mantz, A.W.},
  title = {Frequency comb-referenced measurements of self- and nitrogen-broadening in the ν1 + ν3 band of acetylene},
  journal = {Journal of Molecular Spectroscopy},
  year = {2011},
  volume = {266},
  pages = {43-51},
  doi = {10.1016/j.jms.2011.02.016}
}
Abstract: In this study we have retrieved the line intensities, self broadened widths, pressure-induced shifts and selected line mixing coefficients for 20 R-branch transitions in the ν1 + ν2 + ν4 + ν5 band of acetylene. The spectra were recorded using our 3-channels diode laser spectrometer, a temperature controlled cell of fixed length and a second, room temperature cell. The Voigt and speed-dependent Voigt profiles with inclusion of line mixing effects were used to retrieve the line parameters. We determined the temperature dependencies for line broadening, shift and line mixing coefficients. © 2011 Elsevier Inc. All rights reserved.
BibTeX:
@article{Povey2011,
  author = {Povey, C. and Predoi-Cross, A. and Hurtmans, D.R.},
  title = {Line shape study of acetylene transitions in the ν1 + ν2 + ν4 + ν5 band over a range of temperatures},
  journal = {Journal of Molecular Spectroscopy},
  year = {2011},
  volume = {268},
  pages = {177-188},
  doi = {10.1016/j.jms.2011.04.020}
}
Abstract: Methanol (CH3OH) and formic acid (HCOOH) are among the most abundant volatile organic compounds present in the atmosphere. In this work, we derive the global distributions of these two organic species using for the first time the Infrared Atmospheric Sounding Interferometer (IASI) launched onboard the MetOp-A satellite in 2006. This paper describes the method used and provides a first critical analysis of the retrieved products. The retrieval process follows a two-step approach in which global distributions are first obtained on the basis of a simple radiance indexing (transformed into brightness temperatures), and then mapped onto column abundances using suitable conversion factors. For methanol, the factors were calculated using a complete retrieval approach in selected regions. In the case of formic acid, a different approach, which uses a set of forward simulations for representative atmospheres, has been used. In both cases, the main error sources are carefully determined: the average relative error on the column for both species is estimated to be about 50%, increasing to about 100% for the least favorable conditions. The distributions for the year 2009 are discussed in terms of seasonality and source identification. Time series comparing methanol, formic acid and carbon monoxide in different regions are also presented. © 2011 Author(s).
BibTeX:
@article{Razavi2011,
  author = {Razavi, A. and Karagulian, F. and Clarisse, L. and Hurtmans, D. and Coheur, P.F. and Clerbaux, C. and Müller, J.F. and Stavrakou, T.},
  title = {Global distributions of methanol and formic acid retrieved for the first time from the IASI/MetOp thermal infrared sounder},
  journal = {Atmospheric Chemistry and Physics},
  year = {2011},
  volume = {11},
  pages = {857-872},
  doi = {10.5194/acp-11-857-2011}
}
Abstract: Presently only limited sets of tropospheric ammonia (NH3) measurements in the Earth's atmosphere have been reported from satellite and surface station measurements, despite the well-documented negative impact of NH3 on the environment and human health. Presented here is a detailed description of the satellite retrieval strategy and analysis for the Tropospheric Emission Spectrometer (TES) using simulations and measurements. These results show that: (i) the level of detectability for a representative boundary layer TES NH3 mixing ratio value is ∼0.4 ppbv, which typically corresponds to a profile that contains a maximum level value of ∼1 ppbv; (ii) TES NH3 retrievals generally provide at most one degree of freedom for signal (DOFS), with peak sensitivity between 700 and 900 mbar; (iii) TES NH3 retrievals show significant spatial and seasonal variability of NH3 globally; (iv) initial comparisons of TES observations with GEOS-CHEM estimates show TES values being higher overall. Important differences and similarities between modeled and observed seasonal and spatial trends are noted, with discrepancies indicating areas where the timing and magnitude of modeled NH3 emissions from agricultural sources, and to lesser extent biomass burning sources, need further study. © Author(s) 2011. CC Attribution 3.0 License.
BibTeX:
@article{Shephard2011,
  author = {Shephard, M.W. and Cady-Pereira, K.E. and Luo, M. and Henze, D.K. and Pinder, R.W. and Walker, J.T. and Rinsland, C.P. and Bash, J.O. and Zhu, L. and Payne, V.H. and Clarisse, L.},
  title = {TES ammonia retrieval strategy and global observations of the spatial and seasonal variability of ammonia},
  journal = {Atmospheric Chemistry and Physics},
  year = {2011},
  volume = {11},
  pages = {10743-10763},
  doi = {10.5194/acp-11-10743-2011}
}
Abstract: During the POLARCAT summer campaign in 2008, two episodes (2g-5 July and 7g-10 July 2008) occurred where low-pressure systems traveled from Siberia across the Arctic Ocean towards the North Pole. The two cyclones had extensive smoke plumes from Siberian forest fires and anthropogenic sources in East Asia embedded in their associated air masses, creating an excellent opportunity to use satellite and aircraft observations to validate the performance of atmospheric transport models in the Arctic, which is a challenging model domain due to numerical and other complications. Here we compare transport simulations of carbon monoxide (CO) from the Lagrangian transport model FLEXPART and the Eulerian chemical transport model TOMCAT with retrievals of total column CO from the IASI passive infrared sensor onboard the MetOp-A satellite. The main aspect of the comparison is how realistic horizontal and vertical structures are represented in the model simulations. Analysis of CALIPSO lidar curtains and in situ aircraft measurements provide further independent reference points to assess how reliable the model simulations are and what the main limitations are. The horizontal structure of mid-latitude pollution plumes agrees well between the IASI total column CO and the model simulations. However, finer-scale structures are too quickly diffused in the Eulerian model. Applying the IASI averaging kernels to the model data is essential for a meaningful comparison. Using aircraft data as a reference suggests that the satellite data are biased high, while TOMCAT is biased low. FLEXPART fits the aircraft data rather well, but due to added background concentrations the simulation is not independent from observations. The multi-data, multi-model approach allows separating the influences of meteorological fields, model realisation, and grid type on the plume structure. In addition to the very good agreement between simulated and observed total column CO fields, the results also highlight the difficulty to identify a data set that most realistically represents the actual pollution state of the Arctic atmosphere. © 2011 Adis Data Information BV. All rights reserved.
BibTeX:
@article{Sodemann2011,
  author = {Sodemann, H. and Pommier, M. and Arnold, S.R. and Monks, S.A. and Stebel, K. and Burkhart, J.F. and Hair, J.W. and Diskin, G.S. and Clerbaux, C. and Coheur, P.-F. and Hurtmans, D. and Schlager, H. and Blechschmidt, A.-M. and Kristjánsson, J.E. and Stohl, A.},
  title = {Episodes of cross-polar transport in the Arctic troposphere during July 2008 as seen from models, satellite, and aircraft observations},
  journal = {Atmospheric Chemistry and Physics},
  year = {2011},
  volume = {11},
  pages = {3631-3651},
  doi = {10.5194/acp-11-3631-2011}
}
Abstract: This study provides improved methanol emission estimates on the global scale, in particular for the largest methanol source, the terrestrial biosphere, and for biomass burning. To this purpose, one complete year of spaceborne measurements of tropospheric methanol columns retrieved for the first time by the thermal infrared sensor IASI aboard the MetOp satellite are compared with distributions calculated by the IMAGESv2 global chemistry-transport model. Two model simulations are performed using a priori biogenic methanol emissions either from the new MEGANv2.1 emission model, which is fully described in this work and is based on net ecosystem flux measurements, or from a previous parameterization based on net primary production by Jacob et al. (2005). A significantly better model performance in terms of both amplitude and seasonality is achieved through the use of MEGANv2.1 in most world regions, with respect to IASI data, and to surface- and air-based methanol measurements, even though important discrepancies over several regions are still present. As a second step of this study, we combine the MEGANv2.1 and the IASI column abundances over continents in an inverse modelling scheme based on the adjoint of the IMAGESv2 model to generate an improved global methanol emission source. The global optimized source totals 187 Tg yr&minus;1 with a contribution of 100 Tg yr&minus;1 from plants, only slightly lower than the a priori MEGANv2.1 value of 105 Tg yr&minus;1. Large decreases with respect to the MEGANv2.1 biogenic source are inferred over Amazonia (up to 55 %) and Indonesia (up to 58 %), whereas more moderate reductions are recorded in the Eastern US (20-25 %) and Central Africa (25-35 %). On the other hand, the biogenic source is found to strongly increase in the arid and semi-arid regions of Central Asia (up to a factor of 5) and Western US (factor of 2), probably due to a source of methanol specific to these ecosystems which is unaccounted for in the MEGANv2.1 inventory. The most significant error reductions achieved by the optimization concern the derived biogenic emissions over the Amazon and over the Former Soviet Union. The robustness of the derived fluxes to changes in convective updraft fluxes, in methanol removal processes, and in the choice of the biogenic a priori inventory is assessed through sensitivity inversions. Detailed comparisons of the model with a number of aircraft and surface observations of methanol, as well as new methanol measurements in Europe and in the Reunion Island show that the satellite-derived methanol emissions improve significantly the agreement with the independent data, giving thus credence to the IASI dataset. © 2011 Author(s).
BibTeX:
@article{Stavrakou2011,
  author = {Stavrakou, T. and Guenther, A. and Razavi, A. and Clarisse, L. and Clerbaux, C. and Coheur, P.-F. and Hurtmans, D. and Karagulian, F. and De MaziÃ̈re, M. and Vigouroux, C. and Amelynck, C. and Schoon, N. and Laffineur, Q. and Heinesch, B. and Aubinet, M. and Rinsland, C. and Müller, J.-F.},
  title = {First space-based derivation of the global atmospheric methanol emission fluxes},
  journal = {Atmospheric Chemistry and Physics},
  year = {2011},
  volume = {11},
  pages = {4873-4898},
  doi = {10.5194/acp-11-4873-2011}
}
Abstract: The Aprilg-May, 2010 volcanic eruptions of Eyjafjallajökull, Iceland caused significant economic and social disruption in Europe whilst state of the art measurements and ash dispersion forecasts were heavily criticized by the aviation industry. Here we demonstrate for the first time that large improvements can be made in quantitative predictions of the fate of volcanic ash emissions, by using an inversion scheme that couples a priori source information and the output of a Lagrangian dispersion model with satellite data to estimate the volcanic ash source strength as a function of altitude and time. From the inversion, we obtain a total fine ash emission of the eruption of 8.3 ± 4.2 Tg for particles in the size range of 2.8g-28 μm diameter. We evaluate the results of our model results with a posteriori ash emissions using independent ground-based, airborne and space-borne measurements both in case studies and statistically. Subsequently, we estimate the area over Europe affected by volcanic ash above certain concentration thresholds relevant for the aviation industry. We find that during three episodes in April and May, volcanic ash concentrations at some altitude in the atmosphere exceeded the limits for the "Normal" flying zone in up to 14 % (6g-16 %), 2 % (1g-3 %) and 7 % (4g-11 %), respectively, of the European area. For a limit of 2 mg mĝ̂'3 only two episodes with fractions of 1.5 % (0.2g-2.8 %) and 0.9 % (0.1g-1.6 %) occurred, while the current "No-Fly" zone criterion of 4 mg mg-3 was rarely exceeded. Our results have important ramifications for determining air space closures and for real-time quantitative estimations of ash concentrations. Furthermore, the general nature of our method yields better constraints on the distribution and fate of volcanic ash in the Earth system. © 2011 Author(s).
BibTeX:
@article{Stohl2011,
  author = {Stohl, A. and Prata, A.J. and Eckhardt, S. and Clarisse, L. and Durant, A. and Henne, S. and Kristiansen, N.I. and Minikin, A. and Schumann, U. and Seibert, P. and Stebel, K. and Thomas, H.E. and Thorsteinsson, T. and Tørseth, K. and Weinzierl, B.},
  title = {Determination of time-and height-resolved volcanic ash emissions and their use for quantitative ash dispersion modeling: The 2010 Eyjafjallajökull eruption},
  journal = {Atmospheric Chemistry and Physics},
  year = {2011},
  volume = {11},
  pages = {4333-4351},
  doi = {10.5194/acp-11-4333-2011}
}
Abstract: To further our understanding of the effects of biomass burning emissions on atmospheric composition, we report measurements of trace species in biomass burning plumes made by the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) instrument on the SCISAT-1 satellite. An extensive set of 15 molecules, C 2H 2, C 2H 6, CH 3OH, CH 4, CO, H 2CO, HCN, HCOOH, HNO 3, NO, NO 2, N 2O 5, O 3, OCS and SF6 are used in our analysis. Even though most biomass burning smoke is typically confined to the boundary layer, some of these emissions are injected directly into the free troposphere via fire-related convective processes and transported away from the emission source. Further knowledge of the aging of biomass burning emissions in the free troposphere is needed. Tracer-tracer correlations are made between known pyrogenic species in these plumes in an effort to characterize them and follow their chemical evolution. Criteria such as age and type of biomass material burned are considered. © 2011 Author(s).
BibTeX:
@article{Tereszchuk2011,
  author = {Tereszchuk, K.A. and González Abad, G. and Clerbaux, C. and Hurtmans, D. and Coheur, P.-F. and Bernath, P.F.},
  title = {ACE-FTS measurements of trace species in the characterization of biomass burning plumes},
  journal = {Atmospheric Chemistry and Physics},
  year = {2011},
  volume = {11},
  pages = {12169-12179},
  doi = {10.5194/acp-11-12169-2011}
}
Abstract: We present a new method for measuring SO2 with the data from the ASTER (Advanced Spaceborne Thermal Emission and Reflectance radiometer) orbital sensor. The method consists of adjusting the SO2 column amount until the ratios of radiance simulated on several ASTER bands match the observations. We present a sensitivity analysis for this method, and two case studies. The sensitivity analysis shows that the selected band ratios depend much less on atmospheric humidity, sulfate aerosols, surface altitude and emissivity than the raw radiances. Measurements with &lt;25% relative precision are achieved, but only when the thermal contrast between the plume and the underlying surface is higher than 10K. For the case studies we focused on Miyakejima and Etna, two volcanoes where SO2 is measured regularly by COSPEC or scanning DOAS. The SO2 fluxes computed from a series of ten images of Miyakejima over the period 2000-2002 is in agreement with the long term trend of measurement for this volcano. On Etna, we compared SO2 column amounts measured by ASTER with those acquired simultaneously by ground-based automated scanning DOAS. The column amounts compare quite well, providing a more rigorous validation of the method. The SO2 maps retrieved with ASTER can provide quantitative insights into the 2D structure of non-eruptive volcanic plumes, their dispersion and their progressive depletion in SO2. © 2010 .
BibTeX:
@article{Campion2010,
  author = {Campion, R. and Salerno, G.G. and Coheur, P.-F. and Hurtmans, D. and Clarisse, L. and Kazahaya, K. and Burton, M. and Caltabiano, T. and Clerbaux, C. and Bernard, A.},
  title = {Measuring volcanic degassing of SO2 in the lower troposphere with ASTER band ratios},
  journal = {Journal of Volcanology and Geothermal Research},
  year = {2010},
  volume = {194},
  pages = {42-54},
  doi = {10.1016/j.jvolgeores.2010.04.010}
}
Abstract: We present a sophisticated radiative transfer code for modeling outgoing IR radiation from planetary atmospheres and, conversely, for retrieving atmospheric properties from high-resolution nadir-observed spectra. The forward model is built around a doubling-adding routine and calculates, in a spherical refractive geometry, the outgoing radiation emitted by the Earth and the atmosphere containing one layer of aerosol. The inverse model uses an optimal estimation approach and can simultaneously retrieve atmospheric trace gases, aerosol effective radius, and concentration. It is different from existing codes, as most forward codes dealing with multiple scattering assume a plane-parallel atmosphere, and as for the retrieval, it does not rely on precalculated spectra, the use of microwindows, or two-step retrievals. The simultaneous retrieval on a broad spectral range exploits the full potential of current state-of-the-art hyperspectral IR sounders, such as AIRS and IASI, and should be particularly useful in studying major pollution events. We present five example retrievals of IASI spectra observed in the range from 800 to 1200 cm-1 above dust, volcanic ash, sulfuric acid, ice particles, and biomass burning aerosols. © 2010 Optical Society of America.
BibTeX:
@article{Clarisse2010b,
  author = {Clarisse, L. and Hurtmans, D. and Prata, A.J. and Karagulian, F. and Clerbaux, C. and De Mazière, M. and Coheur, P.-F.},
  title = {Retrieving radius, concentration, optical depth, and mass of different types of aerosols from high-resolution infrared nadir spectra},
  journal = {Applied Optics},
  year = {2010},
  volume = {49},
  pages = {3713-3722},
  doi = {10.1364/AO.49.003713}
}
Abstract: Remote satellite detection of airborne volcanic ash is important for mitigating hazards to aviation and for calculating plume altitudes. Infrared sounders are essential for detecting ash, as they can distinguishing aerosol type and can be used day and night. While broadband sensors are mainly used for this purpose, they have inherent limitations. Typically, water and ice can mask volcanic ash, while wind blown dust can yield false detection. High spectral resolution sounders should be able to overcome some of these limitations. However, existing detection methods are not easily applicable to hyperspectral sounders and there is therefore a pressing need for novel techniques. In response, we propose a sensitive and robust volcanic ash detection method for hyperspectral sounders based on correlation coefficients and demonstrate it on IASI observations. We show that the method differentiates ash from clouds and dust. Easy to implement, it could contribute to operational volcanic hazard mitigation. © 2010 by the American Geophysical Union.
BibTeX:
@article{Clarisse2010a,
  author = {Clarisse, L. and Prata, F. and Lacour, J.-L. and Hurtmans, D. and Clerbaux, C. and Coheur, P.-F.},
  title = {A correlation method for volcanic ash detection using hyperspectral infrared measurements},
  journal = {Geophysical Research Letters},
  year = {2010},
  volume = {37},
  article number = {L19806},
  doi = {10.1029/2010GL044828}
}
Abstract: [1] Atmospheric ammonia (NH3) has recently been observed with infrared sounders from space. Here we present 1 year of detailed bidaily satellite retrievals with the Infrared Atmospheric Sounding Interferometer and some retrievals of the Tropospheric Emission Spectrometer over the San Joaquin Valley, California, a highly polluted agricultural production region. Several sensitivity issues are discussed related to the sounding of ammonia, in terms of degrees of freedom, averaging kernels, and altitude of maximum sensitivity and in relation to thermal contrast and concentration. We also discuss their seasonal dependence and sources of errors. We demonstrate boundary layer sensitivity of infrared sounders when there is a large thermal contrast between the surface and the bottom of the atmosphere. For the San Joaquin Valley, large thermal contrast is the case for daytime measurements in spring, summer, and autumn and for nighttime measurements in autumn and winter when a large negative thermal contrast is amplified by temperature inversion. © 2010 by the American Geophysical Union.
BibTeX:
@article{Clarisse2010,
  author = {Clarisse, L. and Shephard, M.W. and Dentener, F. and Hurtmans, D. and Cady-Pereira, K. and Karagulian, F. and Van Damme, M. and Clerbaux, C. and Coheur, P.-F.},
  title = {Satellite monitoring of ammonia: A case study of the San Joaquin Valley},
  journal = {Journal of Geophysical Research Atmospheres},
  year = {2010},
  volume = {115},
  article number = {D13302},
  doi = {10.1029/2009JD013291}
}
Abstract: Atmospheric remote sensing from satellites is an essential component of the observational strategy deployed to monitor atmospheric pollution and changing composition. During this decade, remote sensors using the thermal infrared (TIR) spectral range have demonstrated their ability to sound the troposphere and provide global distribution for some of the key atmospheric species. This article illustrates three operational applications made possible with the IASI instrument onboard the European satellite MetOp, which opens new perspectives for routine observation of the evolution of atmospheric composition from space. © 2009 Académie des sciences.
BibTeX:
@article{Clerbaux2010,
  author = {Clerbaux, C. and Turquety, S. and Coheur, P.},
  title = {Infrared remote sensing of atmospheric composition and air quality: Towards operational applications},
  journal = {Comptes Rendus - Geoscience},
  year = {2010},
  volume = {342},
  pages = {349-356},
  doi = {10.1016/j.crte.2009.09.010}
}
Abstract: High-spectral resolution infrared spectra of the earth's atmosphere and surface are routinely available from satellite sensors, such as the Atmospheric Infrared Sounder (AIRS) and the Infrared Atmospheric Sounding Interferometer (IASI). We exploit the spectral content of AIRS data to demonstrate that airborne volcanic ash has a unique signature in the infrared (8-12 μm) that can be used to infer particle size, infrared opacity and composition. The spectral signature is interpreted with the aid of a radiative transfer model utilizing the optical properties of andesite, rhyolite and quartz. Based on the infrared spectral signature, a new volcanic ash detection algorithm is proposed that can discriminate volcanic ash from other airborne substances and we show that the algorithm depends on particle size, optical depth and composition. The new algorithm has an improved sensitivity to optically thin ash clouds, and hence can detect them for longer (  4 days) and at greater distances from the source(  5000 km). © 2009 Elsevier Inc. All rights reserved.
BibTeX:
@article{Gangale2010,
  author = {Gangale, G. and Prata, A.J. and Clarisse, L.},
  title = {The infrared spectral signature of volcanic ash determined from high-spectral resolution satellite measurements},
  journal = {Remote Sensing of Environment},
  year = {2010},
  volume = {114},
  pages = {414-425},
  doi = {10.1016/j.rse.2009.09.007}
}
Abstract: In June 2009 the Sarychev volcano located in the Kuril Islands to the northeast of Japan erupted explosively, injecting ash and an estimated 1.2 0.2 Tg of sulfur dioxide into the upper troposphere and lower stratosphere, making it arguably one of the 10 largest stratospheric injections in the last 50 years. During the period immediately after the eruption, we show that the sulfur dioxide (SO2) cloud was clearly detected by retrievals developed for the Infrared Atmospheric Sounding Interferometer (IASI) satellite instrument and that the resultant stratospheric sulfate aerosol was detected by the Optical Spectrograph and Infrared Imaging System (OSIRIS) limb sounder and CALIPSO lidar. Additional surface-based instrumentation allows assessment of the impact of the eruption on the stratospheric aerosol optical depth. We use a nudged version of the HadGEM2 climate model to investigate how well this state-of-the-science climate model can replicate the distributions of SO 2 and sulfate aerosol. The model simulations and OSIRIS measurements suggest that in the Northern Hemisphere the stratospheric aerosol optical depth was enhanced by around a factor of 3 (0.01 at 550 nm), with resultant impacts upon the radiation budget. The simulations indicate that, in the Northern Hemisphere for July 2009, the magnitude of the mean radiative impact from the volcanic aerosols is more than 60% of the direct radiative forcing of all anthropogenic aerosols put together. While the cooling induced by the eruption will likely not be detectable in the observational record, the combination of modeling and measurements would provide an ideal framework for simulating future larger volcanic eruptions. Copyright 2010 by the American Geophysical Union.
BibTeX:
@article{Haywood2010,
  author = {Haywood, J.M. and Jones, A. and Clarisse, L. and Bourassa, A. and Barnes, J. and Telford, P. and Bellouin, N. and Boucher, O. and Agnew, P. and Clerbaux, C. and Coheur, P. and Degenstein, D. and Braesicke, P.},
  title = {Observations of the eruption of the Sarychev volcano and simulations using the HadGEM2 climate model},
  journal = {Journal of Geophysical Research Atmospheres},
  year = {2010},
  volume = {115},
  article number = {D21212},
  doi = {10.1029/2010JD014447}
}
Abstract: In this work we use infrared spectra recorded by the Infrared Atmospheric Sounding Interferometer (IASI) to characterize the emissions from the Mount Kasatochi volcanic eruption on 7 and 8 August 2008. We first derive the total atmospheric load of sulfur dioxide (SO2) and its evolution over time. For the initial plume, we found values over 1.7 Tg Of SO2, making it the largest eruption since the 1991 eruptions of Pinatubo and Hudson. Vertical profiles were retrieved using a line-by-line radiative transfer model and an inversion procedure based on the optimal estimation method (OEM). For the Kasatochi eruption, we found a plume altitude of 12.5 ± 4 km. Taking advantage of IASI's broad spectral coverage, we used the v3 band (∼ 1362 cm-1) and, for the first time, the v1 + v 3 band (∼2500 cm-1) of SO2 for the retrievals. While the v3 band saturates easily for high SO 2 concentrations, preventing accurate retrieval, the v1 + v3 band has a much higher saturation threshold. We also analyzed the broadband signature observed in the radiance spectra in the 1072-1215 cm -1 range associated with the presence of aerosols. In the initial volcanic plume the signature matches closely that of mineral ash, while by 10 August most mineral ash is undetectable, and the extinction is shown to match closely the absorption spectrum of liquid H2SO4 drops. The extinction by sulphuric acid particles was confirmed by comparing spectra before and a month after the eruption, providing the first spectral detection of such aerosols from nadir view radiance data. Copyright 2010 by the American Geophysical Union.
BibTeX:
@article{Karagulian2010,
  author = {Karagulian, F. and Clarisse, L. and Clerbaux, C. and Prata, A.J. and Hurtmans, D. and Coheur, P.F.},
  title = {Detection of volcanic SO2, ash, and H2SO4 using the infrared atmospheric sounding interferometer (IASI)},
  journal = {Journal of Geophysical Research Atmospheres},
  year = {2010},
  volume = {115},
  article number = {D00L02},
  doi = {10.1029/2009JD012786}
}
BibTeX:
@article{Keim2010,
  author = {Keim, C. and Eremenko, M. and Orphal, J. and Dufour, G. and Flaud, J.-M. and Höpfner, M. and Boynard, A. and Clerbaux, C. and Payan, S. and Coheur, P.-F. and Hurtmans, D. and Claude, H. and De Backer, H. and Dier, H. and Johnson, B. and Kelder, H. and Kivi, R. and Koide, T. and López Bartolomé, M. and Lambkin, K. and Moore, D. and Schmidlin, F.J. and Stübi, R.},
  title = {Erratum: Tropospheric ozone from IASI: Comparison of different inversion algorithms and validation with ozone sondes in the northern middle latitudes (Atmospheric Chemistry and Physics (2009) 9 (9329-9347) DOI: 10.5194/acp-9-9329-2009)},
  journal = {Atmospheric Chemistry and Physics},
  year = {2010},
  volume = {10},
  pages = {6345},
  doi = {10.5194/acp-10-6345-2010}
}
Abstract: In this paper, we provide a detailed comparison between carbon monoxide (CO) data measured by the Infrared Atmospheric Sounding Interferometer (IASI)/MetOp and aircraft observations over the Arctic. The CO measurements were obtained during North American (NASA ARCTAS and NOAA ARCPAC) and European campaigns (POLARCAT-France, POLARCAT-GRACE and YAK-AEROSIB) as part of the International Polar Year (IPY) POLARCAT activity in spring and summer 2008. During the campaigns different air masses were sampled including clean air, polluted plumes originating from anthropogenic sources in Europe, Asia and North America, and forest fire plumes originating from Siberia and Canada. The paper illustrates that CO-rich plumes following different transport pathways were well captured by the IASI instrument, in particular due to the high spatial coverage of IASI. The comparison between IASI CO total columns, 0ĝ€"5 km partial columns and profiles with collocated aircraft data was achieved by taking into account the different sensitivity and geometry of the sounding instruments. A detailed analysis is provided and the agreement is discussed in terms of information content and surface properties at the location of the observations. For profiles, the data were found to be in good agreement in spring with differences lower than 17%, whereas in summer the difference can reach 20% for IASI profiles below 8 km for polluted cases. For total columns the correlation coefficients ranged from 0.15 to 0.74 (from 0.47 to 0.77 for partial columns) in spring and from 0.26 to 0.84 (from 0.66 to 0.88 for partial columns) in summer. A better agreement is seen over the sea in spring (0.73 for total column and 0.78 for partial column) and over the land in summer (0.69 for total columns and 0.81 for partial columns). The IASI vertical sensitivity was better over land than over sea, and better over land than over sea ice and snow allowing a higher potential to detect CO vertical distribution during summer. © 2010 Author(s).
BibTeX:
@article{Pommier2010,
  author = {Pommier, M. and Law, K.S. and Clerbaux, C. and Turquety, S. and Hurtmans, D. and Hadji-Lazaro, J. and Coheur, P.-F. and Schlager, H. and Ancellet, G. and Paris, J.-D. and Néd́lec, P. and Diskin, G.S. and Podolske, J.R. and Holloway, J.S. and Bernath, P.},
  title = {IASI carbon monoxide validation over the Arctic during POLARCAT spring and summer campaigns},
  journal = {Atmospheric Chemistry and Physics},
  year = {2010},
  volume = {10},
  pages = {10655-10678},
  doi = {10.5194/acp-10-10655-2010}
}
Abstract: Ash particles and sulfur dioxide gas are two significant components of volcanic clouds that are important because of their effects on the atmosphere. Several different satellite instruments are capable of delivering quantitative measurements of ash and SO2, but few can provide simultaneous assessments. High-spectral resolution (ν/Δν ∼ 1200) infrared satellite data from the Atmospheric Infrared Sounder (AIRS) are utilized to detect volcanic ash within the 8-12 μm window region, and at the same time exploit the 4.0 μm and 7.3 μm bands of SO2 to detect SO 2 at two different heights. The purpose is to study the interaction between gas and particles in dispersing volcanic clouds, and investigate the circumstances when the gas-rich and ash-rich parts of the plume are collocated and when they separate. Simultaneous retrievals of ash and SO2 in the eruption clouds from Okmok and Kasatochi suggest that the two components were transported together for at least the first 3 days after the initial injection. Later (several days) transport is difficult to infer because of the lack of sensitivity of the ash algorithm to thin, dispersing ash clouds. For Kasatochi and Okmok, AIRS measured maximum masses of approximately 1.21 ± 0.01 Tg and 0.29 ± 0.01 Tg of SO2, and 0.31 ± 0.03 Tg and 0.07 ±0.03 Tg of fine ash (1 μm < radii < 10 μm), respectively. The retrieval schemes described here are capable of detecting the distribution of SO2 simultaneously with estimates of ash concentrations from the same satellite instrument and represent an important improvement for observations of multispecies dispersing volcanic clouds. Analyses of other volcanic eruptions show that SO2 and ash do not always travel together. Consequently, it is concluded that for dispersing volcanic clouds it is vital to be able to detect both SO2-rich and ash-rich clouds simultaneously in order to diagnose their effect on the atmosphere and the aviation hazard. © 2010 by the American Geophysical Union.
BibTeX:
@article{Prata2010,
  author = {Prata, A.J. and Gangale, G. and Clarisse, L. and Karagulian, F.},
  title = {Ash and sulfur dioxide in the 2008 eruptions of Okmok and Kasatochi: Insights from high spectral resolution satellite measurements},
  journal = {Journal of Geophysical Research Atmospheres},
  year = {2010},
  volume = {115},
  article number = {D00L18},
  doi = {10.1029/2009JD013556}
}
Abstract: Using a Fourier transform spectrometer setup we have measured the self-broadened half width, pressure shift, and line asymmetry coefficients for transitions in the 30012←00001 and 30013←00001 vibrational bands of carbon dioxide for four different temperatures. A total of 46 pure CO2 spectra were recorded at 0.008 and 0.009cm-1 resolution and at pressures varying from a few Torr to nearly an atmosphere. The individual spectral line profiles have been fitted by a Voigt profile and a speed-dependent Voigt profile, to which we have added dispersion profiles to account for weak line mixing. A comparison of the sets of results obtained for each band showed no vibrational dependence of the broadening coefficients. The self-broadening and self-shift coefficients are compared to semiclassical calculations based on the Robert-Bonamy formalism and were found to be in good agreement. The line asymmetry results are compared to line mixing calculations based on the Energy Corrected Sudden (ECS) and Exponential Power Gap models. © 2010 Elsevier Ltd.
BibTeX:
@article{Predoi-Cross2010,
  author = {Predoi-Cross, A. and Liu, W. and Murphy, R. and Povey, C. and Gamache, R.R. and Laraia, A.L. and McKellar, A.R.W. and Hurtmans, D.R. and Malathy Devi, V.},
  title = {Measurement and computations for temperature dependences of self-broadened carbon dioxide transitions in the 30012←00001 and 30013←00001 bands},
  journal = {Journal of Quantitative Spectroscopy and Radiative Transfer},
  year = {2010},
  volume = {111},
  pages = {1065-1079},
  doi = {10.1016/j.jqsrt.2010.01.003}
}
Abstract: The variability and origin of the Coloured Dissolved Organic Matter (CDOM) were studied in the Belgian coastal and adjacent areas including offshore waters and the Scheldt estuary, through the parameters: absorption at 375 nm, aCDOM(375), and the slope of the absorption curve, S. aCDOM(375) varied between 0.20 and 1.31 m-1 and between 0.97 and 4.30 m-1 in the marine area and Scheldt estuary, respectively. S fluctuated between 0.0101 and 0.0203 nm-1 in the marine area and between 0.0167 and 0.0191 nm-1 in the Scheldt estuary. The comparative analysis of aCDOM(375) and S variations evidenced different origins of CDOM in the BCZ. The Scheldt estuarine waters showed decreasing aCDOM(375) values with increasing salinity but constant S value of ∼0.018 nm-1 suggesting a dominant terrestrial origin of CDOM. On the contrary, samples collected in the marine domain showed a narrow range of aCDOM(375) but highly variable S suggesting the additional presence of autochthonous sources of CDOM. This source was evidenced based on the sorting of the marine offshore data according to the stage of the phytoplankton bloom when they were collected. A clear distinction was made between CDOM released during the growth stage characterized by high S (∼0.017 nm-1) and low aCDOM(375) and the decay phase characterized by low S (∼0.013 nm-1) and high aCDOM(375). This observation was supported by CDOM measurements performed on pure phytoplankton cultures which showed increased CDOM release along the wax and wane of the bloom but decreasing S. We concluded that the high variability of the CDOM signature in offshore waters is explained by the local biological production and processing of CDOM. © 2009 Elsevier Ltd. All rights reserved.
BibTeX:
@article{Astoreca2009,
  author = {Astoreca, R. and Rousseau, V. and Lancelot, C.},
  title = {Coloured dissolved organic matter (CDOM) in Southern North Sea waters: Optical characterization and possible origin},
  journal = {Estuarine, Coastal and Shelf Science},
  year = {2009},
  volume = {85},
  pages = {633-640},
  doi = {10.1016/j.ecss.2009.10.010}
}
Abstract: While mapping algal blooms from space is now well-established, mapping undesirable algal blooms in eutrophicated coastal waters raises further challenge in detecting individual phytoplankton species. In this paper, an algorithm is developed and tested for detecting Phaeocystis globosa blooms in the Southern North Sea. For this purpose, we first measured the light absorption properties of two phytoplankton groups, P. globosa and diatoms, in laboratory-controlled experiments. The main spectral difference between both groups was observed at 467 nm due to the absorption of the pigment chlorophyll c3 only present in P. globosa, suggesting that the absorption at 467 nm can be used to detect this alga in the field. A Phaeocystis-detection algorithm is proposed to retrieve chlorophyll c3 using either total absorption or water-leaving reflectance field data. Application of this algorithm to absorption and reflectance data from Phaeocystis-dominated natural communities shows positive results. Comparison with pigment concentrations and cell counts suggests that the algorithm can flag the presence of P. globosa and provide quantitative information above a chlorophyll c3 threshold of 0.3 mg m -3 equivalent to a P. globosa cell density of 3 × 10 6 cells L-1. Finally, the possibility of extrapolating this information to remote sensing reflectance data in these turbid waters is evaluated. © 2008 The Author(s).
BibTeX:
@article{Astoreca2009a,
  author = {Astoreca, R. and Rousseau, V. and Ruddick, K. and Knechciak, C. and Van Mol, B. and Parent, J.-Y. and Lancelot, C.},
  title = {Development and application of an algorithm for detecting Phaeocystis globosa blooms in the Case 2 Southern North Sea waters},
  journal = {Journal of Plankton Research},
  year = {2009},
  volume = {31},
  pages = {287-300},
  doi = {10.1093/plankt/fbn116}
}
Abstract: In this paper, we present measurements of total and tropospheric ozone, retrieved from infrared radiance spectra recorded by the Infrared Atmospheric Sounding Interferometer (IASI), which was launched on board the MetOp-A European satellite in October 2006. We compare IASI total ozone columns to Global Ozone Monitoring Experiment-2 (GOME-2) observations and groundbased measurements from the Dobson and Brewer network for one full year of observations (2008). The IASI total ozone columns are shown to be in good agreement with both GOME-2 and ground-based data, with correlation coefficients of about 0.9 and 0.85, respectively. On average, IASI ozone retrievals exhibit a positive bias of about 9DU (3.3%) compared to both GOME-2 and ground-based measurements. In addition to total ozone columns, the good spectral resolution of IASI enables the retrieval of tropospheric ozone concentrations. Comparisons of IASI tropospheric columns to 490 collocated ozone soundings available from several stations around the globe have been performed for the period of June 2007-August 2008. IASI tropospheric ozone columns compare well with sonde observations, with correlation coefficients of 0.95 and 0.77 for the [surface-6 km] and [surface-12 km] partial columns, respectively. IASI retrievals tend to overestimate the tropospheric ozone columns in comparison with ozonesonde measurements. Positive average biases of 0.15DU (1.2%) and 3DU (11%) are found for the [surface-6 km] and for the [surface-12 km] partial columns respectively. © 2009 Author(s).
BibTeX:
@article{Boynard2009,
  author = {Boynard, A. and Clerbaux, C. and Coheur, P.-F. and Hurtmans, D. and Turquety, S. and George, M. and Hadji-Lazaro, J. and Keim, C. and Meyer-Arnek, J.},
  title = {Measurements of total and tropospheric ozone from IASI: Comparison with correlative satellite, ground-based and ozonesonde observations},
  journal = {Atmospheric Chemistry and Physics},
  year = {2009},
  volume = {9},
  pages = {6255-6271}
}
Abstract: Global ammonia emissions have more than doubled since pre-industrial times, largely owing to agricultural intensification and widespread fertilizer use1. In the atmosphere, ammonia accelerates particulate matter formation, thereby reducing air quality. When deposited in nitrogen-limited ecosystems, ammonia can act as a fertilizer. This can lead to biodiversity reductions in terrestrial ecosystems, and algal blooms in aqueous environments2-8. Despite its ecological significance, there are large uncertainties in the magnitude of ammonia emissions, mainly owing to a paucity of ground-based observations and a virtual absence of atmospheric measurements3,8-11. Here we use infrared spectra, obtained by the IASI/MetOp satellite, to map global ammonia concentrations from space over the course of 2008. We identify several ammonia hotspots in middle-low latitudes across the globe. In general, we find a good qualitative agreement between our satellite measurements and simulations made using a global atmospheric chemistry transport model. However, the satellite data reveal substantially higher concentrations of ammonia north of 30° N, compared with model projections. We conclude that ammonia emissions could have been significantly underestimated in the Northern Hemisphere, and suggest that satellite monitoring of ammonia from space will improve our understanding of the global nitrogen cycle. © 2009 Macmillan Publishers Limited. All rights reserved.
BibTeX:
@article{Clarisse2009,
  author = {Clarisse, L. and Clerbaux, C. and Dentener, F. and Hurtmans, D. and Coheur, P.-F.},
  title = {Global ammonia distribution derived from infrared satellite observations},
  journal = {Nature Geoscience},
  year = {2009},
  volume = {2},
  pages = {479-483},
  doi = {10.1038/ngeo551}
}
Abstract: Atmospheric remote sounding from satellites is an essential component of the observational strategy deployed to monitor atmospheric pollution and changing composition. The IASI nadir looking thermal infrared sounder onboard MetOp will provide 15 years of global scale observations for a series of key atmospheric species, with unprecedented spatial sampling and coverage. This paper gives an overview of the instrument's capability for measuring atmospheric composition in the perspective of chemistry and air quality. The assessment is made in terms of species, accuracy and vertical information. Global distributions are presented for CO, CH4, O3 (total and tropospheric), HNO3, NH3, and volcanic SO2. Local distributions of organic species measured during fire events, such as C2H4, CH3OH, HCOOH, and PAN are also shown. For each species or process, the link is made to specialized papers in this issue. © 2009 Author(s).
BibTeX:
@article{Clerbaux2009,
  author = {Clerbaux, C. and Boynard, A. and Clarisse, L. and George, M. and Hadji-Lazaro, J. and Herbin, H. and Hurtmans, D. and Pommier, M. and Razavi, A. and Turquety, S. and Wespes, C. and Coheur, P.-F.},
  title = {Monitoring of atmospheric composition using the thermal infrared IASI/MetOp sounder},
  journal = {Atmospheric Chemistry and Physics},
  year = {2009},
  volume = {9},
  pages = {6041-6054}
}
Abstract: This work presents observations of a series of short-lived species in biomass burning plumes from the Infrared Atmospheric Sounding Interferometer (IASI), launched onboard the MetOp-A platform in October 2006. The strong fires that have occurred in the Mediterranean Basin - and particularly Greece - in August 2007, and those in Southern Siberia and Eastern Mongolia in the early spring of 2008 are selected to support the analyses. We show that the IASI infrared spectra in these fire plumes contain distinctive signatures of ammonia (NH3), ethene (C2H4), methanol (CH 3OH) and formic acid (HCOOH) in the atmospheric window between 800 and 1200 cm-1, with some noticeable differences between the plumes. Peroxyacetyl nitrate (CH3COOONO2, abbreviated as PAN) was also observed with good confidence in some plumes and a tentative assignment of a broadband absorption spectral feature to acetic acid (CH3COOH) is made. For several of these species these are the first reported measurements made from space in nadir geometry. The IASI measurements are analyzed for plume height and concentration distributions of NH3, C2H 4 and CH3OH. The Greek fires are studied in greater detail for the days associated with the largest emissions. In addition to providing information on the spatial extent of the plume, the IASI retrievals allow an estimate of the total mass emissions for NH3, C2H 4 and CH3OH. Enhancement ratios are calculated for the latter relative to carbon monoxide (CO), giving insight in the chemical processes occurring during the transport, the first day after the emission.
BibTeX:
@article{Coheur2009,
  author = {Coheur, P.-F. and Clarisse, L. and Turquety, S. and Hurtmans, D. and Clerbaux, C.},
  title = {IASI measurements of reactive trace species in biomass burning plumes},
  journal = {Atmospheric Chemistry and Physics},
  year = {2009},
  volume = {9},
  pages = {5655-5667}
}
Abstract: Between July and November 2008, simultaneous observations were conducted by several orbiting instruments that monitor carbon monoxide in the atmosphere, among them the Infrared Atmospheric Sounding Instrument (IASI) and Measurements Of Pollution In The Troposphere (MOPITT). In this paper, the concentration retrievals at about 700 hPa from these two instruments are successively used in a variational Bayesian system to infer the global distribution of CO emissions. Starting from a global emission budget of 479 Tg for the considered period, the posterior estimate of CO emissions using IASI retrievals gives a total of 643 Tg, which is in close agreement with the budget calculated with version 3 of the MOPITT data (649 Tg). The regional totals are also broadly consistent between the two inversions. Even though our theoretical error budget indicates that IASI constrains the emissions slightly less than MOPITT, because of lesser sensitivity in the lower troposphere, these first results indicate that IASI may play a major role in the quantification of the emissions of CO.
BibTeX:
@article{Fortems-Cheiney2009,
  author = {Fortems-Cheiney, A. and Chevallier, F. and Pison, I. and Bousquet, P. and Carouge, C. and Clerbaux, C. and Coheur, P.-F. and George, M. and Hurtmans, D. and Szopa, S.},
  title = {On the capability of IASI measurements to inform about CO surface emissions},
  journal = {Atmospheric Chemistry and Physics},
  year = {2009},
  volume = {9},
  pages = {8735-8743}
}
Abstract: The Infrared Atmospheric Sounding Interferometer (IASI) onboard the MetOp satellite measures carbon monoxide (CO) on a global scale, twice a day. CO total columns and vertical profiles are retrieved in near real time from the nadir radiance spectra measured by the instrument in the thermal infrared (TIR) spectral range. This paper describes the measurement vertical sensitivity and provides a first assessment of the capabilities of IASI to measure CO distributions. On the global scale, 0.8 to 2.4 independent pieces of information are available for the retrieval. At mid latitudes, the information ranges between 1.5 and 2, which enables the lower and upper troposphere to be distinguished, especially when thermal contrast is significant. Global distributions of column CO are evaluated with correlative observations available from other nadir looking TIR missions currently in operation: the Measurements of Pollution in the Troposphere (MOPITT) onboard TERRA, the Atmospheric Infrared Sounder (AIRS) onboard AQUA and the Tropospheric Emission Spectrometer (TES) onboard AURA. The IASI CO columns are compared with MOPITT, AIRS and TES CO columns, adjusted with the a priori, for three different months: August 2008, November 2008 and February 2009. On average, total column discrepancies of about 7% are found between IASI and the three other sounders in the Northern Hemisphere and in the equatorial region. However when strong CO concentrations are present, such as during fire events, these discrepancies can climb as high as 17%. Instrument specifications of IASI versus other missions are also discussed.
BibTeX:
@article{George2009,
  author = {George, M. and Clerbaux, C. and Hurtmans, D. and Turquety, S. and Coheur, P.-F. and Pommier, M. and Hadji-Lazaro, J. and Edwards, D.P. and Worden, H. and Luo, M. and Rinsland, C. and McMillan, W.},
  title = {Carbon monoxide distributions from the IASI/METOP mission: Evaluation with other space-borne remote sensors},
  journal = {Atmospheric Chemistry and Physics},
  year = {2009},
  volume = {9},
  pages = {8317-8330}
}
Abstract: This work reports the first measurements of ethene (C2H 4) distributions in the upper troposphere. These are obtained by retrieving vertical profiles from 5 to 20 km infrared solar occultation spectra recorded in 2005 and 2006 by the Atmospheric Chemistry Experiment-Fourier Transform Spectrometer (ACE-FTS). Background volume mixing ratios (vmrs) ranging from a few to about 50 pptv (10-12) are measured at the different altitudes, while for certain occultations, vmrs as high as 200 pptv are observed. Zonal distributions and vertically resolved latitudinal distributions are derived for the two year period analyzed, highlighting spatial -including a North-South gradient- as well as seasonal variations. We show the latter to be more pronounced at the highest latitudes, presumably as a result less active photochemistry during winter. The observation of C2H4 enhancements in remote Arctic regions at high latitudes is consistent with the occurrence fast transport processes of gaseous pollution from the continents leading to Arctic haze. © 2009.
BibTeX:
@article{Herbin2009,
  author = {Herbin, H. and Hurtmans, D. and Clarisse, L. and Turquety, S. and Clerbaux, C. and Rinsland, C.P. and Boone, C. and Bernath, P.F. and Coheur, P.-F.},
  title = {Distributions and seasonal variations of tropospheric ethene (C 2H4) from Atmospheric Chemistry Experiment (ACE-FTS) solar occupation spectra},
  journal = {Geophysical Research Letters},
  year = {2009},
  volume = {36},
  article number = {L04801},
  doi = {10.1029/2008GL036338}
}
Abstract: In this paper we analyze distributions of water vapour isotopologues in the troposphere using infrared spectra recorded by the Infrared Atmospheric Sounding Interferometer (IASI), which operates onboard the Metop satellite in nadir geometry. The simultaneous uncorrelated retrievals of H2 16O and HDO are performed on radiance measurements using a line-by-line radiative transfer model and an inversion procedure based on the Optimal Estimation Method (OEM). The characterizations of the retrieved products in terms of vertical sensitivity and error budgets show that IASI measurements contain up to 6 independent pieces of information on the vertical distribution of H216O and up to 3.5 for HDO from the surface up to the upper troposphere (0-20 km). Although the purpose of the paper is not validation, a restricted comparison with sonde measurements shows that the retrieved H216O profiles capture the seasonal/latitudinal variations of the water content, with good accuracy in the lowest layer but with larger uncertainties higher in the free and upper troposphere. Our results then demonstrate the ability of the IASI instrument to monitor atmospheric isotopologic water vapour distributions and to provide information on the partitioning of HDO as compared to H216O. The derivation of the δD is challenging and associated with large errors in the uncorrelated retrieval approach chosen here. As a result averaging on the vertical to produce a column-averaged δD is required to produce meaningful results for geophysical interpretation. As a case study, we analyse concentration distributions and spatio-temporal variations of H2 16O and δD during the October 2007 Krosa super-typhoon over South-East Asia. We show that individual δD have uncertainties of 37&amp;permil; for the vertically averaged values. Using the latter, we suggest that the typhoon produces a so-called amount-effect, where the δD is negatively correlated to the water amounts as a result of intense depletion of the deuterated species.
BibTeX:
@article{Herbin2009a,
  author = {Herbin, H. and Hurtmans, D. and Clerbaux, C. and Clarisse, L. and Coheur, P.-F.},
  title = {H216O and HDO measurements with IASI/MetOp},
  journal = {Atmospheric Chemistry and Physics},
  year = {2009},
  volume = {9},
  pages = {9433-9447}
}
Abstract: High resolution measurements of room temperature absorption with a controlled tunable diode laser (TDL) spectrometer have been made for R(2) and P(14) lines in the HCl fundamental band perturbed by N2, Xe, Ar and He at pressures lower than one atmosphere. Pressure broadening, shift and collisional narrowing parameters have been extracted by least-squares fitting of several collisional profiles to the spectra. Asymmetries are observed for P(14) broadened by Xe at the lowest pressures and attributed to correlations between velocity- and phase-changing collisions. © 2009 Elsevier Inc. All rights reserved.
BibTeX:
@article{Hurtmans2009,
  author = {Hurtmans, D. and Henry, A. and Valentin, A. and Boulet, C.},
  title = {Narrowing broadening and shifting parameters for R(2) and P(14) lines in the HCl fundamental band perturbed by N2 and rare gases from tunable diode laser spectroscopy},
  journal = {Journal of Molecular Spectroscopy},
  year = {2009},
  volume = {254},
  pages = {126-136},
  doi = {10.1016/j.jms.2009.01.015}
}
Abstract: In the northern Gulf of Eilat (Aqaba), sharp increases in the biomass of diatoms and rates of primary production occurred in April 2008. Within 24 h, diatom abundance rose from 8 Ã- 103 to 228 Ã- 10 3 cells l-1, and photosynthetic rates concomitantly doubled from 15 to 35 μg C l-1 d-1. Water transparency declined, as indicated by the vertical diffusion attenuation coefficient K d for photosynthetically active radiation (PAR), which increased from 0.076 to 0.090 m-1 and decreased the euphotic depth from 60 to 45 m. During this time, a significant increase in silica deposition by the diatoms was also detected. We attribute the mentioned changes in environmental characteristics to wind-generated surface currents. Strong winds (up to 10 m s-1) during the measurements enriched the surface layers with unusually high nutrient concentrations within.
BibTeX:
@article{Iluz2009,
  author = {Iluz, D. and Dishon, G. and Capuzzo, E. and Meeder, E. and Astoreca, R. and Montecino, V. and Znachor, P. and Ediger, D. and Marra, J.},
  title = {Short-term variability in primary productivity during a wind-driven diatom bloom in the Gulf of Eilat (Aqaba)},
  journal = {Aquatic Microbial Ecology},
  year = {2009},
  volume = {56},
  pages = {205-215},
  doi = {10.3354/ame01321}
}
Abstract: This paper presents a first statistical validation of tropospheric ozone products derived from measurements of the IASI satellite instrument. Since the end of 2006, IASI (Infrared Atmospheric Sounding Interferometer) aboard the polar orbiter Metop-A measures infrared spectra of the Earth's atmosphere in nadir geometry. This validation covers the northern mid-latitudes and the period from July 2007 to August 2008. Retrieval results from four different sources are presented: three are from scientific products (LATMOS, LISA, LPMAA) and the fourth one is the pre-operational product distributed by EUMETSAT (version 4.2). The different products are derived from different algorithms with different approaches. The difference and their implications for the retrieved products are discussed. In order to evaluate the quality and the performance of each product, comparisons with the vertical ozone concentration profiles measured by balloon sondes are performed and lead to estimates of the systematic and random errors in the IASI ozone products (profiles and partial columns). A first comparison is performed on the given profiles; a second comparison takes into account the altitude dependent sensitivity of the retrievals. Tropospheric columnar amounts are compared to the sonde for a lower tropospheric column (surface to about 6 km) and a total tropospheric column (surface to about 11 km). On average both tropospheric columns have small biases for the scientific products, less than 2 Dobson Units (DU) for the lower troposphere and less than 1 DU for the total troposphere. The comparison of the still pre-operational EUMETSAT columns shows higher mean differences of about 5 DU.
BibTeX:
@article{Keim2009,
  author = {Keim, C. and Eremenko, M. and Orphal, J. and Dufour, G. and Flaud, J.-M. and Höpfner, M. and Boynard, A. and Clerbaux, C. and Payan, S. and Coheur, P.-F. and Hurtmans, D. and Claude, H. and Dier, H. and Johnson, B. and Kelder, H. and Kivi, R. and Koide, T. and Bartolomé, M.L. and Lambkin, K. and Moore, D. and Schmidlin, F.J. and Stübi, R.},
  title = {Tropospheric ozone from IASI: Comparison of different inversion algorithms and validation with ozone sondes in the northern middle latitudes},
  journal = {Atmospheric Chemistry and Physics},
  year = {2009},
  volume = {9},
  pages = {9329-9347}
}
Abstract: Scientific findings from the last decades have clearly highlighted the need for a more comprehensive approach to atmospheric change processes. In fact, observation of atmospheric composition variables has been an important activity of atmospheric research that has developed instrumental tools (advanced analytical techniques) and platforms (instrumented passenger aircrafts, ground-based in situ and remote sensing stations, earth observation satellite instruments) providing essential information on the composition of the atmosphere. The variability of the atmospheric system and the extreme complexity of the atmospheric cycles for short-lived gaseous and aerosol species have led to the development of complex models to interpret observations, test our theoretical understanding of atmospheric chemistry and predict future atmospheric composition. The validation of numerical models requires accurate information concerning the variability of atmospheric composition for targeted species via comparison with observations and measurements. In this paper, we provide an overview of recent advances in instrumentation and methodologies for measuring atmospheric composition changes from space, aircraft and the surface as well as recent improvements in laboratory techniques that permitted scientific advance in the field of atmospheric chemistry. Emphasis is given to the most promising and innovative technologies that will become operational in the near future to improve knowledge of atmospheric composition. Our current observation capacity, however, is not satisfactory to understand and predict future atmospheric composition changes, in relation to predicted climate warming. Based on the limitation of the current European observing system, we address the major gaps in a second part of the paper to explain why further developments in current observation strategies are still needed to strengthen and optimise an observing system not only capable of responding to the requirements of atmospheric services but also to newly open scientific questions. © 2009 Elsevier Ltd. All rights reserved.
BibTeX:
@article{Laj2009,
  author = {Laj, P. and Klausen, J. and Bilde, M. and Plaß-Duelmer, C. and Pappalardo, G. and Clerbaux, C. and Baltensperger, U. and Hjorth, J. and Simpson, D. and Reimann, S. and Coheur, P.-F. and Richter, A. and De Mazière, M. and Rudich, Y. and McFiggans, G. and Torseth, K. and Wiedensohler, A. and Morin, S. and Schulz, M. and Allan, J.D. and Attié, J.-L. and Barnes, I. and Birmili, W. and Cammas, J.P. and Dommen, J. and Dorn, H.-P. and Fowler, D. and Fuzzi, S. and Glasius, M. and Granier, C. and Hermann, M. and Isaksen, I.S.A. and Kinne, S. and Koren, I. and Madonna, F. and Maione, M. and Massling, A. and Moehler, O. and Mona, L. and Monks, P.S. and Müller, D. and Müller, T. and Orphal, J. and Peuch, V.-H. and Stratmann, F. and Tanré, D. and Tyndall, G. and Abo Riziq, A. and Van Roozendael, M. and Villani, P. and Wehner, B. and Wex, H. and Zardini, A.A.},
  title = {Measuring atmospheric composition change},
  journal = {Atmospheric Environment},
  year = {2009},
  volume = {43},
  pages = {5351-5414},
  doi = {10.1016/j.atmosenv.2009.08.020}
}
Abstract: With the use of data assimilation, we study the quality of the Infrared Atmospheric Sounding Interferometer (IASI) total ozone column measurements. The IASI data are provided by the inversion of IASI radiances performed at the Laboratoire ATmosphères, Milieux, Observations Spatiales (LATMOS). This data set is initially compared on a five-month period to a three-dimensional time varying ozone field that we take as a reference. This reference field results from the combined assimilation of ozone profiles from the Microwave Limb Sounder (MLS) instrument and of total ozone columns from the SCanning Imaging Absorption spectrometer for Atmospheric CHartographY (SCIAMACHY) instrument. It has low systematic and random errors when compared to ozonesondes and Ozone Monitoring Instrument (OMI) data. The comparison shows that on average, the LATMOS-IASI data tends to overestimate the total ozone columns by 2% to 8%. The random observation error of the LATMOS-IASI data is estimated to about 7%, except over polar regions and deserts where it is higher. The daytime data have generally lower biases but higher random error than the nighttime data. Using this information, the LATMOS-IASI data are then assimilated, combined with the MLS data. This first LATMOS-IASI data assimilation experiment shows that the resulting analysis is quite similar to the one obtained from the combined MLS and SCIAMACHY data assimilation. The differences are mainly due to the lack of SCIAMACHY measurements during polar night, and to the higher LATMOS-IASI random errors especially over the southern polar region. © 2009 Author(s).
BibTeX:
@article{Massart2009,
  author = {Massart, S. and Clerbaux, C. and Cariolle, D. and Piacentini, A. and Turquety, S. and Hadji-Lazaro, J.},
  title = {First steps towards the assimilation of IASI ozone data into the MOCAGE-PALM system},
  journal = {Atmospheric Chemistry and Physics},
  year = {2009},
  volume = {9},
  pages = {5073-5091}
}
Abstract: We present a line shape analysis of the P(2) and P(7) transitions of CO broadened by Xe in the fundamental band. The spectra were recorded at 349 K using a difference frequency laser spectrometer. To obtain information on the influence of Dicke narrowing, relaxation speed dependence, and line mixing effects, several models for implementation of Dicke narrowing and (or) speed-dependent effects are discussed. From experimental data analysis, we conclude that line shape models taking into account the Dicke effect only fail in the high pressure regime and lead to optical diffusion parameters that are much larger than the kinetic diffusion ones. On the contrary, a fair interpretation of data is obtained from speed-dependent models, so that it is possible to derive a quantitative estimate of optical diffusion effects that appear much smaller than the kinetic diffusion ones. Xe-broadening coefficients of CO lines in the fundamental band at 297 and 349 K are calculated from a semiclassical formalism involving successively two intermolecular potentials, the atom-atom Lennard-Jones model, and a three-term expansion of Legendre polynomials with four adjustable parameters.
BibTeX:
@article{Predoi-Cross2009,
  author = {Predoi-Cross, A. and Rohart, F. and Bouanich, J.-P. and Hurtmans, D.R.},
  title = {Xenon-broadened CO line shapes in the fundamental band at 349 K},
  journal = {Canadian Journal of Physics},
  year = {2009},
  volume = {87},
  pages = {485-498},
  doi = {10.1139/P08-123}
}
Abstract: Although the global methane (CH4) concentration has more than doubled since pre-industrial times, local emission sources are still poorly identified and quantified. Instruments onboard satellites can improve our knowledge about the methane global distribution owing to their very good spatial coverage. The IASI (Infrared Atmospheric Sounding Interferometer) instrument launched on the European MetOp-A platform is a Fourier transform spectrometer which measures the thermal infrared radiation emitted by the Earth and its atmosphere. In this paper, we present the first global distribution of methane total columns (mostly sensitive to the middle troposphere) from the IASI spectra using the methane &amp;nu;4 absorption band. The retrieval spectral range was set in order to minimize possible spectroscopic issues. Results are discussed in terms of error budget and vertical sensitivity. In addition, we study the gain of information on surface methane concentrations provided by using the &amp;nu;3 band, which is partly covered by IASI on the short-wave end of the spectra (extending to 2760 cm&amp;minus;1), where solar reflection contributes significantly.
BibTeX:
@article{Razavi2009,
  author = {Razavi, A. and Clerbaux, C. and Wespes, C. and Clarisse, L. and Hurtmans, D. and Payan, S. and Camy-Peyret, C. and Coheur, P.F.},
  title = {Characterization of methane retrievals from the IASI space-borne sounder},
  journal = {Atmospheric Chemistry and Physics},
  year = {2009},
  volume = {9},
  pages = {7889-7899}
}
Abstract: Satellite-based remote sensing measurements of volcanic sulfur dioxide (SO2) provide critical information for reducing volcanic hazards. This paper describes the use of SO2 measurements from the thermal infrared sounder IASI and the UV-VIS instrument GOME-2 in services related to aviation hazard and early warning of volcanic unrest. The high sensitivity of both instruments to SO2 allows the detection and global tracking of volcanic eruption plumes and makes them a valuable tool for volcanic aviation hazard mitigation. The GOME-2 and IASI SO2 data are produced in near-real time and distributed to the Volcanic Ash Advisory Centers (VAACS) to assist them in issuing alerts to airlines and air traffic control organizations. Examples of recent eruptions affecting air traffic are presented including Jebel al Tair (Yemen, September 2007), Mount Okmok (Alaska, July 2008), and Mount Kasatochi (Alaska, August 2008). In addition, GOME-2 can detect changes in the SO2 emissions from passively degassing volcanoes and, therefore, provide critical information for hazard assessment. The monitoring of pre-emptive degassing by GOME-2 is used in early warning of volcanic activity by a mobile volcano fast response system in combination with numerous other parameters, such as seismicity, deformation, and thermal anomalies. © 2009, The Institute of Electrical and Electronics Engineers, Inc.
BibTeX:
@article{Rix2009,
  author = {Rix, M. and Valks, P. and Hao, N. and Loyola, D.G.R. and Zimmer, W. and Emmadi, S. and Rix, M. and van Geffen, J. and Clerbaux, C. and Clerbaux, C. and Clarisse, L. and Coheur, P.-F. and Erbertseder, T.},
  title = {Satellite Monitoring of Volcanic Sulfur Dioxide Emissions for Early Warning of Volcanic Hazards},
  journal = {IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing},
  year = {2009},
  volume = {2},
  pages = {196-206},
  doi = {10.1109/JSTARS.2009.2031120}
}
Abstract: In this paper, we analyze the performance of the Infrared Atmospheric Sounding Interferometer (IASI), launched in October 2006 on board METOP-A, for the monitoring of carbon monoxide (CO) during extreme fire events, focusing on the record-breaking fires which devastated thousands of square kilometers of forest in Greece during the last week (23-30) of August 2007. After an assessment of the quality of the profiles retrieved using the Fast Optimal Retrievals on Layers for IASI (FORLI) algorithm, the information provided on fire emissions and subsequent pollution outflow is discussed. Large CO plumes were observed above the Mediterranean Basin and North Africa, with total CO columns exceeding 24×1018 molecules/cm2 and absolute volume mixing ratios up to 4 ppmv on the 25 August. Up to 30×1018 molecules/cm2 and 22 ppmv in the lower troposphere are retrieved close to the fires above the Peloponnese, but with larger uncertainty. The average root-mean-square (RMS) difference between simulated and observed spectrais close to the estimated radiometric noise level, slightly increasing (by ∼14%) in the fresh fire plumes. CO profiles are retrieved with a vertical resolution of about 8 km, with ∼1.7 pieces of independent information on the vertical in the region considered and a maximum sensitivity in the free troposphere (∼4-5 km). Using the integrated total amount, the increase in CO burden due to these fires is estimated to 0.321 Tg, ∼40% of the total annual anthropogenic emissions in Greece. The patterns of these CO enhance- ments are in good agreement with the aerosol optical depth (AOD) retrieved from the MODIS measurements, highlighting a rapid transport of trace gases and aerosols across the Mediterranean Basin (less than one day). While the coarse vertical resolution will not allow the location of the exact plume height, the large CO enhancements observed in the lower troposphere are consistent with the maximum aerosol backscatter coefficient at ∼2 km detected by the CALIPSO lidar in space (CALIOP). © Author(s) 2009.
BibTeX:
@article{Turquety2009,
  author = {Turquety, S. and Hurtmans, D. and Hadji-Lazaro, J. and Coheur, P.-F. and Clerbaux, C. and Josset, D. and Tsamalis, C.},
  title = {Tracking the emission and transport of pollution from wildfires using the IASI CO retrievals: Analysis of the summer 2007 Greek fires},
  journal = {Atmospheric Chemistry and Physics},
  year = {2009},
  volume = {9},
  pages = {4897-4913}
}
Abstract: This paper presents the first global distributions of HNO3 total columns acquired by the Infrared Atmospheric Sounding Interferometer (IASI) instrument, launched onboard the MetOp platform in October 2006. IASI is an infrared nadir-looking Fourier transform spectrometer providing atmospheric radiance spectra at 0.5 cm?1 spectral resolution, from which temperature and infrared absorbing gas concentration profiles are retrieved with global Earth coverage twice a day. A first analysis of the IASI measurements in terms of information content demonstrates the possibility of retrieving a total column for HNO3 at all latitudes with a maximal sensitivity in the middle stratosphere. The retrievals are performed from IASI spectra in the atmospheric window using a fast radiative transfer model and inversion software (FORLI) relying on the Optimal Estimation Method. The operational processing of HNO3 total columns is achieved since March 2008. We show that FORLI-HNO3 performs well at all latitudes (RMS of the spectral residuals around 2.3×10?6 W/m2 srm?1) and provides HNO3 total columns with on average statistical errors of about 12%, reaching the threshold value of 32% at the equatorial belt. The global distributions of the retrieved total columns for one year (from March 2008 to February 2009) are presented and discussed with emphasis given to seasonal and interhemispheric variations. Local seasonal variations at 6 specific locations are also described and discussed in comparison with MLS volume mixing ratios at 46.5 hPa. The seasonal cycle observedin Polar regions is highlighted, with maxima observed in fallwinter and minima during spring-summer. The denitrification inside the Antarctic polar vortex during winter is clearly revealed with unprecedented horizontal resolution: HNO 3 columns decreasing down to about 1×cm?2 are observed, which is consistent with the lower values of temperature observed between 50 and 15 hPa (∼20-25 km) and the resulting formation and sedimentation of polar stratospheric clouds. During the same period, the collar region of high quantities of HNO3 at the vortex edge is also observed around 65-60° S latitude. Preliminary correlations between IASI derived HNO3 and O3 columns inside the polar vortex are presented and discussed. © 2009 Author(s).
BibTeX:
@article{Wespes2009,
  author = {Wespes, C. and Hurtmans, D. and Clerbaux, C. and Santee, M.L. and Martin, R.V. and Coheur, P.F.},
  title = {Global distributions of nitric acid from IASI/MetOP measurements},
  journal = {Atmospheric Chemistry and Physics},
  year = {2009},
  volume = {9},
  pages = {7949-7962}
}
Abstract: In this paper we demonstrate the potential of the infrared Fourier transform spectrometer IASI in analysing volcanic eruptions, using the September 2007 eruption at Jebel at Tair as an illustrative example. Detailed radiative transfer calculations are presented, simulating IASI-like transmittance spectra for a variety of volcanic plumes. We analyse the sensitivity of IASI to SO 2 at different altitudes and demonstrate that IASI is in principle capable of sensing SO2 down to the surface. Using the brightness temperature difference of well chosen SO2 channels as a filter, we are able to track the plume of the Jebel at Tair eruption for 12 days, on a par with state of the art UV sounders. A method is presented for quickly estimating the altitude of a volcanic plume based on the relative intensities of the SO2 absorption lines. Despite recent advances, it is still very challenging to retrieve vertical profiles of SO2 from nadir viewing satellites. Currently the most accurate profiles in nadir are retrieved using backtracking of the plume with atmospheric transport models. Via full inverse retrievals using the optimal estimation method, we show the possibility of extracting medium coarse vertical profiles from IASI data. The retrieval allows us to present an evolution of the total mass of SO2 in the plume for the Jebel at Tair eruption. An analytical relation is derived between brightness temperature differences and concentrations, which fits the experimental data very well. The spectral range of IASI also allows retrieval of volcanic aerosols. In the initial plume of the Jebel at Tair eruption, volcanic aerosols were found in the form of ice particles, for which we derived particle sizes. © Author(s) 2008.
BibTeX:
@article{Clarisse2008,
  author = {Clarisse, L. and Coheur, P.F. and Prata, A.J. and Hurtmans, D. and Razavi, A. and Phulpin, T. and Hadji-Lazaro, J. and Clerbaux, C.},
  title = {Tracking and quantifying volcanic SO2 with IASI, the September 2007 eruption at Jebel at Tair},
  journal = {Atmospheric Chemistry and Physics},
  year = {2008},
  volume = {8},
  pages = {7723-7734}
}
Abstract: Satellite measurements are now recognized as a key element for the early detection and characterization of volcanic eruptions, in particular in the context of aircraft routing. A common tracer of volcanic plumes is sulfur dioxide (SO2), which so far has been measured by ultraviolet-visible (UV-vis) instruments and multispectral infrared (IR) sounders. Here we report the first SO2 vertical profile retrieved from high spectral resolution thermal infrared nadir radiance spectra and we provide information on both the quantity of gas emitted and its altitude. From the radiance spectra provided by the Tropospheric Emission Spectrometer (TES) aboard the NASA AURA satellite, and owing to the ∼0.1 cm-1 (apodized) spectral resolution, elevated levels of SO2 were measured following volcanic eruptions occurring in 2005 (Manam, Sierra Negra) and 2006 (Rabaul, Nyamuragira). Column values are found to be in good agreement with the data provided by Ozone Mapping Instrument (OMI), a UV-vis instrument also onboard the AURA satellite. Copyright 2008 by the American Geophysical Union.
BibTeX:
@article{Clerbaux2008a,
  author = {Clerbaux, C. and Coheur, P.-F. and Clarisse, L. and Hadji-Lazaro, J. and Hurtmans, D. and Turquety, S. and Bowman, K. and Worden, H. and Carn, S.A.},
  title = {Measurements of so2 profiles in volcanic plumes from the NASA Tropospheric Emission Spectrometer (TES)},
  journal = {Geophysical Research Letters},
  year = {2008},
  volume = {35},
  article number = {L22807},
  doi = {10.1029/2008GL035566}
}
Abstract: Carbon monoxide (CO) is a key species for tracking pollution plumes. The Measurement Of Pollution in The Troposphere (MOPITT) mission onboard the Terra satellite has already provided 7.5 years of CO atmospheric concentration measurements around the globe. Limited sensitivity to the boundary layer is well known to be a weakness of nadir looking thermal infrared sounders. This paper investigates the possibility of using the MOPITT surface measurements to detect CO emitted by cities and urban centers. By selecting the data and averaging them over long time periods, we demonstrate that the CO pollution arising from the large cities and urban areas can be distinguished from the background transported pollution. The more favorable observations are obtained during daytime and at locations where the thermal contrast (temperature gradient) between the surface and lower atmosphere is significant. Copyright 2008 by the American Geophysical Union.
BibTeX:
@article{Clerbaux2008,
  author = {Clerbaux, C. and Edwards, D.P. and Deeter, M. and Emmons, L. and Lamarque, J.-F. and Tie, X.X. and Massie, S.T. and Gille, J.},
  title = {Carbon monoxide pollution from cities and urban areas observed by the Terra/MOPITT mission},
  journal = {Geophysical Research Letters},
  year = {2008},
  volume = {35},
  article number = {L03817},
  doi = {10.1029/2007GL032300}
}
Abstract: The Atmospheric Chemistry Experiment (ACE) mission was launched in August 2003 to sound the atmosphere by solar occultation. Carbon monoxide (CO), a good tracer of pollution plumes and atmospheric dynamics, is one of the key species provided by the primary instrument, the ACE-Fourier Transform Spectrometer (ACE-FTS). This instrument performs measurements in both the CO 1-0 and 2-0 ro-vibrational bands, from which vertically resolved CO concentration profiles are retrieved, from the mid-troposphere to the thermosphere. This paper presents an updated description of the ACE-FTS version 2.2 CO data product, along with a comprehensive validation of these profiles using available observations (February 2004 to December 2006). We have compared the CO partial columns with ground-based measurements using Fourier transform infrared spectroscopy and millimeter wave radiometry, and the volume mixing ratio profiles with airborne (both high-altitude balloon flight and airplane) observations. CO satellite observations provided by nadir-looking instruments (MOPITT and TES) as well as limb-viewing remote sensors (MIPAS, SMR and MLS) were also compared with the ACE-FTS CO products. We show that the ACE-FTS measurements provide CO profiles with small retrieval errors (better than 5% from the upper troposphere to 40 km, and better than 10% above). These observations agree well with the correlative measurements, considering the rather loose coincidence criteria in some cases. Based on the validation exercise we assess the following uncertainties to the ACE-FTS measurement data: better than 15% in the upper troposphere (8-12 km), than 30% in the lower stratosphere (12-30 km), and than 25% from 30 to 100 km. © Author(s) 2008.
BibTeX:
@article{Clerbaux2008b,
  author = {Clerbaux, C. and George, M. and Turquety, S. and Walker, K.A. and Barret, B. and Bernath, P. and Boone, C. and Borsdorff, T. and Cammas, J.P. and Catoire, V. and Coffey, M. and Coheur, P.-F. and Deeter, M. and De Mazière, M. and Drummond, J. and Duchatelet, P. and Dupuy, E. and De Zafra, R. and Eddounia, F. and Edwards, D.P. and Emmons, L. and Funke, B. and Gille, J. and Griffith, D.W.T. and Hannigan, J. and Hase, F. and Höpfner, M. and Jones, N. and Kagawa, A. and Kasai, Y. and Kramer, I. and Le Flochmoën, E. and Livesey, N.J. and López-Puertas, M. and Luo, M. and Mahieu, E. and Murtagh, D. and Nédélec, P. and Pazmino, A. and Pumphrey, H. and Ricaud, P. and Rinsland, C.P. and Robert, C. and Schneider, M. and Senten, C. and Stiller, G. and Strandberg, A. and Strong, K. and Sussmann, R. and Thouret, V. and Urban, J. and Wiacek, A.},
  title = {CO measurements from the ACE-FTS satellite instrument: Data analysis and validation using ground-based, airborne and spaceborne observations},
  journal = {Atmospheric Chemistry and Physics},
  year = {2008},
  volume = {8},
  pages = {2569-2594}
}
Abstract: The development of Gestion et Etude des Informations Spectroscopiques Atmosphériques (GEISA: Management and Study of Spectroscopic Information) was started over three decades at Laboratoire de Météorologie Dynamique (LMD) in France. GEISA is a computer accessible spectroscopic database, designed to facilitate accurate forward radiative transfer calculations using a line-by-line and layer-by-layer approach. More than 350 users have been registered for on-line use of the GEISA facilities. The current 2003 edition of GEISA (GEISA-03) is a system comprising three independent sub-databases devoted respectively to: line transition parameters, infrared and ultraviolet/visible absorption cross-sections, microphysical and optical properties of atmospheric aerosols. Currently, GEISA is involved in activities related to the assessment of the capabilities of IASI (Infrared Atmospheric Sounding Interferometer on board of the METOP European satellite) through the GEISA/IASI database derived from GEISA. The GEISA-03 content is presented, placing emphasis on molecular species of interest for Earth and planetary atmosphere studies, with details on the updated 2008 archive underway. A critical assessment on the needs, in terms of molecular parameters archive, related with recent satellite astrophysical missions is made. Detailed information on free on-line GEISA and GEISA/IASI access is given at http://ara.lmd.polytechnique.fr and http://ether.ipsl.jussieu.fr. © 2008 Elsevier Ltd. All rights reserved.
BibTeX:
@article{Jacquinet-Husson2008,
  author = {Jacquinet-Husson, N. and Scott, N.A. and Chédin, A. and Crépeau, L. and Armante, R. and Capelle, V. and Orphal, J. and Coustenis, A. and Boonne, C. and Poulet-Crovisier, N. and Barbe, A. and Birk, M. and Brown, L.R. and Camy-Peyret, C. and Claveau, C. and Chance, K. and Christidis, N. and Clerbaux, C. and Coheur, P.F. and Dana, V. and Daumont, L. and De Backer-Barilly, M.R. and Di Lonardo, G. and Flaud, J.M. and Goldman, A. and Hamdouni, A. and Hess, M. and Hurley, M.D. and Jacquemart, D. and Kleiner, I. and Köpke, P. and Mandin, J.Y. and Massie, S. and Mikhailenko, S. and Nemtchinov, V. and Nikitin, A. and Newnham, D. and Perrin, A. and Perevalov, V.I. and Pinnock, S. and Régalia-Jarlot, L. and Rinsland, C.P. and Rublev, A. and Schreier, F. and Schult, L. and Smith, K.M. and Tashkun, S.A. and Teffo, J.L. and Toth, R.A. and Tyuterev, Vl.G. and Vander Auwera, J. and Varanasi, P. and Wagner, G.},
  title = {The GEISA spectroscopic database: Current and future archive for Earth and planetary atmosphere studies},
  journal = {Journal of Quantitative Spectroscopy and Radiative Transfer},
  year = {2008},
  volume = {109},
  pages = {1043-1059},
  doi = {10.1016/j.jqsrt.2007.12.015}
}
Abstract: Identification of phytoplankton groups from space is essential to map and monitor algal blooms in coastal waters, but remains a challenge due to the presence of suspended sediments and dissolved organic matter which interfere with phytoplankton signal. On the basis of field measurements of remote sensing reflectance (Rrs(λ)), bio-optical parameters, and phytoplankton cells enumerations, we assess the feasibility of using multispectral and hyperspectral approaches for detecting spring blooms of Phaeocystis globosa (P. globosa). The two reflectance ratios (Rrs(490) /Rrs(510) and Rrs(442.5) /Rrs(490)), used in the multispectral inversion, suggest that detection of P. globosa blooms are possible from current ocean color sensors. The effects of chlorophyll concentration, colored dissolved organic matter (CDOM), and particulate matter composition on the performance of this multispectral approach are investigated via sensitivity analysis. This analysis indicates that the development of a remote sensing algorithm, based on the values of these two ratios, should include information about CDOM concentration. The hyperspectral inversion is based on the analysis of the second derivative of Rrs(λ) (dλ2 Rrs). Two criteria, based on the position of the maxima and minima of dλ2Rrs, are established to discriminate the P. globosa blooms from diatoms blooms. We show that the position of these extremes is related to the specific absorption spectrum of P. globosa and is significantly correlated with the relative biomass of P. globosa. This result confirms the advantage of a hyperspectral over multispectral inversion for species identification and enumeration from satellite observations of ocean color. Copyright 2008 by the American Geophysical Union.
BibTeX:
@article{Lubac2008,
  author = {Lubac, B. and Loisel, H. and Guiselin, N. and Astoreca, R. and Artigas, L.F. and Mériaux, X.},
  title = {Hyperspectral and multispectral ocean color inversions to detect Phaeocystis globosa blooms in coastal waters},
  journal = {Journal of Geophysical Research: Oceans},
  year = {2008},
  volume = {113},
  article number = {C06026},
  doi = {10.1029/2007JC004451}
}
Abstract: This paper reports accurate line positions, intensities, self-broadening, -shift and -line mixing coefficients for 56 rotational transitions from multispectrum fits of low noise, high-resolution Fourier-transform spectra. The measured line intensities are within the statistical spread of the previous measurements available in the literature-thus contributing to the efforts to measure the oxygen A-band intensities with an accuracy better than 1%. We determined the integrated band strength and Einstein A coefficient. Using our spectrum calibration method we could clearly show for the first time that there is a meaningful statistical discrepancy in the frequency standards used in spectroscopic studies for the oxygen A-band. We were able to explain how this discrepancy leads to two different sets of shifts reported in the literature and demonstrate the need for precise frequency-type transition wavenumber measurements of the oxygen A-band transitions. We observed deviations from the conventional Voigt profile due to speed-dependent broadening and line mixing effects. Dicke narrowing was observed on a selected group of spectra recorded at pressures between 98 and 337 Torr. The Dicke narrowed lineshapes were best modeled using a Galatry profile implemented using a fixed value for the velocity-changing collision rate. The weak line mixing coefficients were determined from fits using the speed-dependent models. Exponential Power Gap (EPG) and Energy Corrected Sudden (ECS) scaling laws were used to calculate the self-broadening and self-line mixing coefficients. © 2007 Elsevier Inc. All rights reserved.
BibTeX:
@article{Predoi-Cross2008c,
  author = {Predoi-Cross, A. and Hambrook, K. and Keller, R. and Povey, C. and Schofield, I. and Hurtmans, D. and Over, H. and Mellau, G.Ch.},
  title = {Spectroscopic lineshape study of the self-perturbed oxygen A-band},
  journal = {Journal of Molecular Spectroscopy},
  year = {2008},
  volume = {248},
  pages = {85-110},
  doi = {10.1016/j.jms.2007.11.007}
}
Abstract: We report measurements for N2-broadening, pressure-shift and line mixing coefficients for 55 oxygen transitions in the A-band retrieved using a multispectrum fitting technique. Nineteen laboratory absorption spectra were recorded at 0.02 cm-1 resolution using a multi-pass absorption cell with path length of 1636.9 cm and the IFS 120 Fourier transform spectrometer located at Justus-Liebig-University in Giessen, Germany. The total sample pressures ranged from 8.8 to 3004.5 Torr with oxygen volume mixing ratios in nitrogen ranging between 0.057 and 0.62. An Exponential Power Gap (EPG) scaling law was used to calculate the N2-broadening and N2-line mixing coefficients. The line broadening and shift coefficients for the A-band of oxygen self-perturbed and perturbed by N2 are modeled using semiclassical calculations based on the Robert-Bonamy formalism and two intermolecular potentials. These potentials involve electrostatic contributions including the hexadecapole moment of the molecules and (a) a simple dispersion contribution with one adjustable parameter to fit the broadening coefficients or (b) the atom-atom Lennard-Jones model without such adjustable parameters. The first potential leads to very weak broadening coefficients for high J transitions whereas the second potential gives much more improved results at medium and large J values, in reasonable agreement with the experimental data. For the line shifts which mainly arise in our calculation from the electronic state dependence of the isotropic potential, their general trends with increasing J values can be well predicted, especially from the first potential. From the theoretical results, we have derived air-broadening and air-induced shift coefficients with an agreement comparable to that obtained for O2-O2 and O2-N2. © 2008 Elsevier Inc. All rights reserved.
BibTeX:
@article{Predoi-Cross2008,
  author = {Predoi-Cross, A. and Holladay, C. and Heung, H. and Bouanich, J.-P. and Mellau, G.Ch. and Keller, R. and Hurtmans, D.R.},
  title = {Nitrogen-broadened lineshapes in the oxygen A-band: Experimental results and theoretical calculations},
  journal = {Journal of Molecular Spectroscopy},
  year = {2008},
  volume = {251},
  pages = {159-175},
  doi = {10.1016/j.jms.2008.02.010}
}
Abstract: This work is a room temperature study of the 30012 ← 00001 and 30013 ← 00001 vibrational bands in self- and air-broadened carbon dioxide. The spectra were recorded at a resolution of 0.008 cm-1 or 0.009 cm -1 using a Fourier transform spectrometer and a temperature stabilized long path absorption cell. The analysis is performed using a multispectrum nonlinear least squares fitting technique where the spectra are fitted simultaneously in spectral intervals of about 3 cm-1. Voigt and Speed Dependent Voigt line shape models are used. Intensities, self- and air-broadening, shifts, and weak line mixing coefficients are determined and compared with other studies. Comparisons are also made to demonstrate the importance of considering the line shape effects for measurements in Earth's atmosphere using satellite remote sensing. Examples of multispectrum fits with and without the inclusion of line mixing are also given. Exponential Power Gap (EPG) and Energy Corrected Sudden (ECS) scaling laws are used to calculate the relaxation matrix elements and model the broadening and line mixing coefficients. © 2008 American Institute of Physics.
BibTeX:
@conference{Predoi-Cross2008d,
  author = {Predoi-Cross, A. and McKellar, A.R.W. and Hurtmans, D.R.},
  title = {High accuracy line profile study of transitions in the 30012 ← 00001 and 30013 ← 00001 bands of carbon dioxide},
  journal = {AIP Conference Proceedings},
  year = {2008},
  volume = {1058},
  pages = {265-272},
  doi = {10.1063/1.3026459}
}
Abstract: We present a line shape analysis on the P(2) and P(7) transitions of CO broadened by Xe in the fundamental band. The spectra were recorded at 349 K using a difference frequency laser spectrometer. For line shape analysis, line mixing effects were included and several models describing the Dicke effect were considered. It is shown that retrieved diffusion parameters are pressure dependent and larger than kinetic diffusion parameters. Finally, all these Dicke line shape models fail in the high pressure regime, that rules out the appropriateness of the Dicke effect for the CO-Xe system. © 2008 American Institute of Physics.
BibTeX:
@conference{Predoi-Cross2008e,
  author = {Predoi-Cross, A. and Rohart, F. and Bouanich, J.-P. and Hurtmans, D.R.},
  title = {Xe-broadened CO line shapes in the fundamental band at 349 K},
  journal = {AIP Conference Proceedings},
  year = {2008},
  volume = {1058},
  pages = {178-180},
  doi = {10.1063/1.3026438}
}
BibTeX:
@article{Predoi-Cross2008a,
  author = {Predoi-Cross, A. and Unni, A.V. and Liu, W. and Schofield, I. and Holladay, C. and McKellar, A.R.W. and Hurtmans, D.},
  title = {Corrigendum to "Line profile study of transitions in the 30012 ← 00001 and 30013 ← 00001 bands of carbon dioxide perturbed by air" [J. Mol. Spectrosc. 246 (2007) 98-112] (DOI:10.1016/j.jms.2007.08.008)},
  journal = {Journal of Molecular Spectroscopy},
  year = {2008},
  volume = {249},
  pages = {121},
  doi = {10.1016/j.jms.2008.03.001}
}
BibTeX:
@article{Predoi-Cross2008b,
  author = {Predoi-Cross, A. and Unni, A.V. and Liu, W. and Schofield, I. and Holladay, C. and McKellar, A.R.W. and Hurtmans, D.},
  title = {Corrigendum to "Line shape parameters measurement and computations for self-broadened carbon dioxide transitions in the 30012 ← 00001 and 30013 ← 00001 bands, line mixing and speed dependence" [J. Mol. Spectrosc. 245 (2007) 34-51] (DOI:10.1016/j.jms.2007.07.004)},
  journal = {Journal of Molecular Spectroscopy},
  year = {2008},
  volume = {249},
  pages = {72},
  doi = {10.1016/j.jms.2008.02.011}
}
Abstract: High spectral resolution Fourier transform spectrometer (FTS) measurements of tropospheric carbon monoxide (CO) distributions show mixing ratios over Indonesia during October 2006 of ∼200 ppbv (10-9 per unit volume) in the middle troposphere. The elevated emissions were caused by intense and widespread Indonesian peat and forest fire emissions elevated compared to other years by the impact of a moderate El Niño/Soutern Oscillation (ENSO) event, which delayed that year's monsoon season and produced very dry conditions. Moderate resolution imaging spectrometer (MODIS) fire counts, atmospheric chemistry experiment (ACE) measurements of elevated mixing ratios of fire emission products and near infrared extinction, and back trajectory calculations for a sample measurement location near the time of maximum emissions provide additional evidence that the elevated 2006 emissions resulted primarily from the Indonesia fires. Lower CO mixing ratios measured by ACE and fewer MODIS fire counts in Indonesia during October 2005 indicate lower emissions than during 2006. Coincident profiles from the ACE agree within the uncertainties with those from the tropospheric emission spectrometer (TES) for pressure ranges and time periods with good TES sensitivity after accounting for its lower vertical sensitivity compared with the ACE FTS. © 2007 Elsevier Ltd. All rights reserved.
BibTeX:
@article{Rinsland2008,
  author = {Rinsland, C.P. and Luo, M. and Shephard, M.W. and Clerbaux, C. and Boone, C.D. and Bernath, P.F. and Chiou, L. and Coheur, P.F.},
  title = {Tropospheric emission spectrometer (TES) and atmospheric chemistry experiment (ACE) measurements of tropospheric chemistry in tropical southeast Asia during a moderate El Niño in 2006},
  journal = {Journal of Quantitative Spectroscopy and Radiative Transfer},
  year = {2008},
  volume = {109},
  pages = {1931-1942},
  doi = {10.1016/j.jqsrt.2007.12.020}
}
Abstract: Following validation activities and corresponding improvements in processing algorithms over the first few years of the MERIS mission, the algal1 and algal2 products are now considered as sufficiently mature for use in applications in Belgian waters. The utility of this product has been enhanced by the development of a number of multitemporal products including single point time series, multitemporal composites (monthly/3-monthly means) and annual products such as the mean and 90 percentile concentrations and the timing of the spring bloom. Marine management applications include: support for the assessment of eutrophication status in the context of the Oslo and Paris Convention for the Prevention of Marine Pollution (OSPAR), optimisation of seaborne monitoring, detection of harmful algal blooms and support for aquaculture. More generally, the MERIS data is used in support of marine science including the validation of ecosystem models and may be used in the future for the estimation of air-sea carbon fluxes. The current status of these applications is described together with an assessment of the remaining scientific challenges as well as the future possibilities.
BibTeX:
@conference{Ruddick2008,
  author = {Ruddick, K. and Park, Y. and Astoreca, R. and Borges, A. and Lacroix, G. and Lancelot, C. and Rousseau, V.},
  title = {Applications of the MERIS algal pigment products in Belgian waters},
  journal = {European Space Agency, (Special Publication) ESA SP},
  year = {2008}
}
Abstract: This paper describes the validation of MERIS water products for the Southern North Sea for the period July 2002 to September 2008. During this period, 39 matchups were obtained for the parameters water-leaving reflectance spectra, chlorophyll a concentration and total suspended matter concentration, of which 12 are in optimal conditions. Previous validation results reported for 2002-5 are updated to 2008. Conclusions are largely reinforced since the MERIS processor has not changed. In particular it is recommended to improve estimation of the spectral slope of aerosol reflectance in turbid waters. Some image artifacts are noted including noisy low chlorophyll data. Inherent optical property data is analysed and compared to the assumptions used for derivation of the MERIS products. Turbidity has been added to the in situ parameter set, strengthening quality control of water sample analysis.
BibTeX:
@conference{Ruddick2008a,
  author = {Ruddick, K. and Park, Y. and Astoreca, R. and Neukermans, G. and Van Mol, B.},
  title = {Validation of MERIS water products in the southern North Sea: 2002-2008},
  journal = {European Space Agency, (Special Publication) ESA SP},
  year = {2008}
}
Abstract: Ground-based high spectral resolution Fourier-transform infrared (FTIR) solar absorption spectroscopy is a powerful remote sensing technique to obtain information on the total column abundances and on the vertical distribution of various constituents in the atmosphere. This work presents results from two FTIR measurement campaigns in 2002 and 2004, held at Ile de La Réunion (21° S, 55° E). These campaigns represent the first FTIR observations carried out at a southern (sub)tropical site. They serve the initiation of regular, long-term FTIR monitoring at this site in the near future. To demonstrate the capabilities of the FTIR measurements at this location for tropospheric and stratospheric monitoring, a detailed report is given on the retrieval strategy, information content and corresponding full error budget evaluation for ozone (O3), methane (CH4), nitrous oxide (N2O), carbon monoxide (CO), ethane (C 2H6), hydrogen chloride (HCl), hydrogen fluoride (HF) and nitric acid (HNO3) total and partial column retrievals. Moreover, we have made a thorough comparison of the capabilities at sea level altitude (St.-Denis) and at 2200 m a.s.l. (Maïdo). It is proved that the performances of the technique are such that the atmospheric variability can be observed, at both locations and in distinct altitude layers. Comparisons with literature and with correlative data from ozone sonde and satellite (i.e., ACE-FTS, HALOE and MOPITT) measurements are given to confirm the results. Despite the short time series available at present, we have been able to detect the seasonal variation of CO in the biomass burning season, as well as the impact of particular biomass burning events in Africa and Madagascar on the atmospheric composition above Ile de La Réunion. We also show that differential measurements between St.-Denis and Maïdo provide useful information about the concentrations in the boundary layer.
BibTeX:
@article{Senten2008,
  author = {Senten, C. and De Mazière, M. and Dils, B. and Hermans, C. and Kruglanski, M. and Neefs, E. and Scolas, F. and Vandaele, A.C. and Vanhaelewyn, G. and Vigouroux, C. and Carleer, M. and Coheur, P.F. and Fally, S. and Barret, B. and Baray, J.L. and Delmas, R. and Leveau, J. and Metzger, J.M. and Mahieu, E. and Boone, C. and Walker, K.A. and Bernath, P.F. and Strong, K.},
  title = {Technical note: New ground-based FTIR measurements at Ile de la Réunion: Observations, error analysis, and comparisons with independent data},
  journal = {Atmospheric Chemistry and Physics},
  year = {2008},
  volume = {8},
  pages = {3483-3508}
}
Abstract: The results of nitrogen broadening measurements in the ν3 band of 12CH4 using the 5.37 m long absorption path length all-copper Herriott cell were presented. The experimental pressure shift data for 90 and for 140 K temperatures were plotted, where the pressure shift for each component was plotted versus pressure expressed in units of atmospheres. The comparison of values with the values given by HITRAN04 at 296 K show differences of -2.77×10-3cm-1atm-1 in absolute value compared to the database which is largely in the error bar. Absolute differences from 1.9 to 15.3×10-4cm-1atm-1 are observed for the room temperature pressure shift coefficient.
BibTeX:
@article{Tumuhimbise2008,
  author = {Tumuhimbise, A.T. and Hurtmans, D. and Mondelain, D. and Mantz, A.W.},
  title = {Nitrogen-pressure shifts in the ν3 band of methane measured at several temperatures between 300 and 90 K},
  journal = {Journal of Molecular Spectroscopy},
  year = {2008},
  volume = {252},
  pages = {239-241},
  doi = {10.1016/j.jms.2008.09.001}
}
Abstract: This study presents the complementary picture of the pollution outflow provided by several satellite observations of carbon monoxide (CO), based on different observation techniques. This is illustrated by an analysis of the Asian outflow during the spring of 2005, through comparisons with simulations by the LMDz-INCA global chemistry transport model. The CO observations from the MOPITT and SCIAMACHY nadir sounders, which provide vertically integrated information with excellent horizontal sampling, and from the ACE-FTS solar occultation instrument, which has limited spatial coverage but allows the retrieval of vertical profiles, are used. Combining observations from MOPITT (mainly sensitive to the free troposphere) and SCIAMACHY (sensitive to the full column) allows a qualitative evaluation of the boundary layer CO. The model tends to underestimate this residual compared to the observations, suggesting underestimated emissions, especially in eastern Asia. However, a better understanding of the consistency and possible biases between the MOPITT and SCIAMACHY CO is necessary for a quantitative evaluation. Underestimated emissions, and possibly too low lofting and underestimated chemical production in the model, lead to an underestimate of the export to the free troposphere, as highlighted by comparisons with MOPITT and ACE-FTS. Both instruments observe large trans-Pacific transport extending from ∼20° N to ∼60° N, with high upper tropospheric CO observed by ACE-FTS above the eastern Pacific (with values of up to 300 ppbv around 50° N at 500 hPa and up to ∼200 ppbv around 30° N at 300 hPa). The low vertical and horizontal resolutions of the global model do not allow the simulation of the strong enhancements in the observed plumes. However, the transport patterns are well captured, and are mainly attributed to export from eastern Asia, with increasing contributions from South Asia and Indonesia towards the tropics. Additional measurements of C2H2, C2H 6 and HCN by ACE-FTS provide further information on the plume history. C2H2 and C2H6 enhancements are well correlated with the CO plumes, indicating common sources and rapid trans-Pacific transport. HCN observations show that the biomass burning contributes mainly at latitudes lower than ∼40° N. This study provides a first step towards a full combination of complementary observations, but also highlights the need for a better evaluation of consistency between the datasets in order to allow precise quantitative analyses.
BibTeX:
@article{Turquety2008,
  author = {Turquety, S. and Clerbaux, C. and Law, K. and Coheur, P.-F. and Cozic, A. and Szopa, S. and Hauglustaine, D.A. and Hadji-Lazaro, J. and Gloudemans, A.M.S. and Schrijver, H. and Boone, C.D. and Bernath, P.F. and Edwards, D.P.},
  title = {CO emission and export from Asia: An analysis combining complementary satellite measurements (MOPITT, SCIAMACHY and ACE-FTS) with global modeling},
  journal = {Atmospheric Chemistry and Physics},
  year = {2008},
  volume = {8},
  pages = {5187-5204}
}
Abstract: The high resolution laboratory spectrum of hot water vapour has been recorded in the 500-13 000 cm-1 wavenumber range and we report on the analysis of the 4750-13 000 cm-1 (0.769-2.1 μm) portion. The emission spectrum was recorded using an oxy-acetylene welding torch and a Fourier transform spectrometer. Line assignments in the laboratory spectrum as well as in an absorption spectrum of a sunspot umbra were made with the help of the BT2 line-list. Our torch spectrum is the first laboratory observation of the 9300 Å 'steam bands' seen in M-stars and brown dwarfs. © 2008 The Authors.
BibTeX:
@article{Zobov2008,
  author = {Zobov, N.F. and Shirin, S.V. and Ovsyannikov, R.I. and Polyansky, O.L. and Barber, R.J. and Tennyson, J. and Bernath, P.F. and Carleer, M. and Colin, R. and Coheur, P.-F.},
  title = {Spectrum of hot water in the 4750-13 000 cm-1 wavenumber range (0.769-2.1 μm)},
  journal = {Monthly Notices of the Royal Astronomical Society},
  year = {2008},
  volume = {387},
  pages = {1093-1098},
  doi = {10.1111/j.1365-2966.2008.13234.x}
}
Abstract: We define the disentangling power of a unitary operator in a similar way as the entangling power defined by Zanardi et al. [P. Zanardi, C. Zalka, L. Faoro, Phys. Rev. A 62 (2000) 030301(R), quant-ph/0005031]. A general formula is derived and it is shown that both quantities are directly proportional. All results concerning the entangling power can simply be translated into similar statements for the disentangling power. In particular, the disentangling power is maximal for certain permutations derived from orthogonal Latin squares. These permutations can therefore be interpreted as those that distort entanglement in a maximal way. © 2007 Elsevier B.V. All rights reserved.
BibTeX:
@article{Clarisse2007,
  author = {Clarisse, L. and Ghosh, S. and Severini, S. and Sudbery, A.},
  title = {The disentangling power of unitaries},
  journal = {Physics Letters, Section A: General, Atomic and Solid State Physics},
  year = {2007},
  volume = {365},
  pages = {400-402},
  doi = {10.1016/j.physleta.2007.02.001}
}
BibTeX:
@article{Clerbaux2007,
  author = {Clerbaux, C. and Hadji-Lazaro, J. and Turquety, S. and George, M. and Coheur, P.-F. and Hurtmans, D. and Wespes, C. and Herbin, H. and Blumstein, D. and Tourniers, B. and Phulpin, T.},
  title = {The IASI/MetOp1Mission: First observations and highlights of its potential contribution to GMES2},
  journal = {Space Research Today},
  year = {2007},
  volume = {168},
  pages = {19-24},
  doi = {10.1016/S0045-8732(07)80046-5}
}
Abstract: In the course of our study of the upper tropospheric composition with the infrared Atmospheric Chemistry Experiment - Fourier Transform Spectrometer (ACEFTS), we found an occultation sequence that on 8 October 2005, sampled a remarkable plume near the east coast of Tanzania. Model simulations of the CO distribution in the Southern hemisphere are performed for this period and they suggest that the emissions for this event likely originated from a nearby forest fire, after which the plume was transported from the source region to the upper troposphere. Taking advantage of the very high signal-to-noise ratio of the ACE-FTS spectra over a wide wavenumber range (750-4400 cm-1), we present in-depth analyses of the chemical composition of this plume in the middle and upper troposphere, focusing on the measurements of weakly absorbing pollutants. For this specific biomass burning event, we report simultaneous observations of an unprecedented number of organic species. Measurements of C2H4 (ethene), C3H4 (propyne), H2CO (formaldehyde), C3H6O (acetone) and CH3COO2NO2 (peroxyacetylnitrate, abbreviated as PAN) are the first reported detections using infrared occultation spectroscopy from satellites. Based on the lifetime of the emitted species, we discuss the photochemical age of the plume and also report, whenever possible, the enhancement ratios relative to CO.
BibTeX:
@article{Coheur2007,
  author = {Coheur, P.-F. and Herbin, H. and Clerbaux, C. and Hurtmans, D. and Wespes, C. and Carleer, M. and Turquety, S. and Rinsland, C.P. and Remedios, J. and Hauglustaine, D. and Boone, C.D. and Bernath, P.F.},
  title = {ACE-FTS observation of a young biomass burning plume: First reported measurements of C2H4, C3H6O, H 2CO and PAN by infrared occultation from space},
  journal = {Atmospheric Chemistry and Physics},
  year = {2007},
  volume = {7},
  pages = {5437-5446}
}
Abstract: The isotopologic composition of water vapour in the atmosphere provides valuable information on many climate, chemical and dynamical processes. The accurate measurements of the water isotopologues by remote-sensing techniques remains a challenge, due to the large spatial and temporal variations. Simultaneous profile retrievals of the main water isotopologues (i.e. H 216O, H218O and HDO) and their ratios are presented here for the first time, along their retrieved global distributions. The results are obtained by exploiting the high resolution infrared spectra recorded by the Interferometric Monitor for Greenhouse gases (IMG) instrument, which has operated in the nadir geometry onboard the ADEOS satellite between 1996 and 1997. The retrievals are performed on cloud-free radiances, measured during ten days of April 1997, considering two atmospheric windows (1205-1228 cm-1; 2004-2032 cm-1) and using a line-by-line radiative transfer model and an inversion procedure based on the Optimal Estimation Method (OEM). Characterizations in terms of vertical sensitivity and error budget are provided. We show that a relatively high vertical resolution is achieved for H216O (∼4-5 km), and that the retrieved profiles are in fair agreement with local sonde measurements, at different latitudes. The retrieved global distributions of H216O, H218O, HDO and their ratios are presented and found to be consistent with previous experimental studies and models. The Ocean-Continent difference, the latitudinal and vertical dependence of the water vapour amount and the isotopologic depletion are notably well reproduced. Others trends, possibly related to small-scale variations in the vertical profiles are also discussed. Despite the difficulties encountered for computing accurately the isotopologic ratios, our results demonstrate the ability of infrared nadir sounding for monitoring atmospheric isotopologic water vapour distributions on a global scale.
BibTeX:
@article{Herbin2007,
  author = {Herbin, H. and Hartmans, D. and Turquety, S. and Wespes, C. and Barret, B. and Hadji-Lazaro, J. and Clerbaux, C. and Coheur, P.-F.},
  title = {Global distributions of water vapour isotopologues retrieved from IMG/ADEOS data},
  journal = {Atmospheric Chemistry and Physics},
  year = {2007},
  volume = {7},
  pages = {3957-3968}
}
Abstract: The design of a new apparatus, named FANTASIO, for studying jet-cooled molecules is described. It includes, around the same supersonic expansion cell, a high resolution Fourier transform spectrometer with single or multipass optics, a tunable diode laser spectrometer with optional cavity ring-down facilities, and a quadrupole mass spectrometer. Performance and operational procedures are illustrated.
BibTeX:
@article{Herman2007,
  author = {Herman, M. and Didriche, K. and Hurtmans, D. and Kizil, B. and MacKo, P. and Rizopoulos, A. and Van Poucke, P.},
  title = {FANTASIO: A versatile experimental set-up to investigate jet-cooled molecules},
  journal = {Molecular Physics},
  year = {2007},
  volume = {105},
  pages = {815-823},
  doi = {10.1080/00268970601063820}
}
Abstract: We measured the temperature dependence of the nitrogen broadening, narrowing and line-mixing coefficients of four lines of the P9 manifold in the ν3 band of 12CH4 for atmospheric purposes. The data were collected using our tunable diode laser (TDL) spectrometer with active wavenumber control coupled to a newly developed cold Herriott cell with a path length of 5.37 m and a temperature uniformity of better than 0.01 K along the cell. We recorded and analyzed spectra recorded at sample temperatures between 90 K and room temperature. We have investigated the influence of our new results in the inversion model used to retrieve methane profiles from atmospheric spectra; our new results make it possible to retrieve significantly more precise methane profiles. The atmospheric spectra we utilized were obtained by several of us with a balloon-born Fourier Transform infrared experiment in a limb configuration. Differences up to 7% on the retrieved volume mixing ratio were found compared to an inversion model using only HITRAN04 spectroscopic parameters. © 2007 Elsevier Inc. All rights reserved.
BibTeX:
@article{Mondelain2007,
  author = {Mondelain, D. and Payan, S. and Deng, W. and Camy-Peyret, C. and Hurtmans, D. and Mantz, A.W.},
  title = {Measurement of the temperature dependence of line mixing and pressure broadening parameters between 296 and 90 K in the ν3 band of 12CH4 and their influence on atmospheric methane retrievals},
  journal = {Journal of Molecular Spectroscopy},
  year = {2007},
  volume = {244},
  pages = {130-137},
  doi = {10.1016/j.jms.2007.05.005}
}
Abstract: In this work we present a line profile study for air-broadened carbon dioxide transitions in the 30012 ← 00001 and 30013 ← 00001 vibrational bands. The room temperature spectra were recorded at a resolution of 0.008 cm-1 using a Fourier Transform spectrometer. The air-broadening, air-shift, and air-line mixing coefficients were derived from a simultaneous fitting of spectra using the Voigt model and a Speed-Dependent Voigt lineshape model. The results obtained are consistent with other studies in addition to the theoretically calculated values. Exponential Power Gap (EPG) and Energy Corrected Sudden (ECS) scaling laws were used to calculate the relaxation matrix elements. © 2007 Elsevier Inc. All rights reserved.
BibTeX:
@article{Predoi-Cross2007,
  author = {Predoi-Cross, A. and Liu, W. and Holladay, C. and Unni, A.V. and Schofield, I. and McKellar, A.R.W. and Hurtmans, D.},
  title = {Line profile study of transitions in the 30012 ← 00001 and 30013 ← 00001 bands of carbon dioxide perturbed by air},
  journal = {Journal of Molecular Spectroscopy},
  year = {2007},
  volume = {246},
  pages = {98-112},
  doi = {10.1016/j.jms.2007.08.008}
}
Abstract: Transitions of pure carbon dioxide have been measured using a Fourier transform spectrometer in the 30012 ← 00001 and 30013 ← 00001 vibrational bands. The room temperature spectra, recorded at a resolution of 0.008 cm-1, were analyzed using the Voigt model and a Speed Dependent Voigt line shape model that includes a pressure dependent narrowing parameter. Intensities, self-induced pressure broadening, shifts, and weak line mixing coefficients are determined. The results obtained are consistent with other studies in addition to the theoretically calculated values. Exponential Power Gap (EPG) and Energy Corrected Sudden (ECS) scaling laws were used to calculate the relaxation matrix elements. © 2007 Elsevier Inc. All rights reserved.
BibTeX:
@article{Predoi-Cross2007a,
  author = {Predoi-Cross, A. and Unni, A.V. and Liu, W. and Schofield, I. and Holladay, C. and McKellar, A.R.W. and Hurtmans, D.},
  title = {Line shape parameters measurement and computations for self-broadened carbon dioxide transitions in the 30012 ← 00001 and 30013 ← 00001 bands, line mixing, and speed dependence},
  journal = {Journal of Molecular Spectroscopy},
  year = {2007},
  volume = {245},
  pages = {34-51},
  doi = {10.1016/j.jms.2007.07.004}
}
Abstract: The Microwave Limb Sounder on Aura has produced an extensive set of measurement of CO in the middle atmosphere. The measurements are usable for scientific studies from the upper troposphere up to 90 km altitude. We describe these measurements and validate them by demonstrating their internal consistency and by comparing them to other remotely sounded measurements and to 2-D model simulations. Comparisons with other measurements suggest that MLS has a positive bias of 25-50% in the mesosphere and a negative bias of up to 70% in the (almost CO-free) lower stratosphere. The geophysical features observed in the MLS CO field show excellent qualitative agreement with other measurements. Copyright 2007 by the American Geophysical Union.
BibTeX:
@article{Pumphrey2007,
  author = {Pumphrey, H.C. and Filipiak, M.J. and Livesey, N.J. and Schwartz, M.J. and Boone, C. and Walker, K.A. and Bernath, P. and Ricaud, P. and Barret, B. and Clerbaux, C. and Jarnot, R.F. and Manney, G.L. and Waters, J.W.},
  title = {Validation of middle-atmosphere carbon monoxide retrievals from the Microwave Limb Sounder on Aura},
  journal = {Journal of Geophysical Research Atmospheres},
  year = {2007},
  volume = {112},
  article number = {D24S38},
  doi = {10.1029/2007JD008723}
}
Abstract: We highlight chemistry and trend measurements from the Atmospheric Chemistry Experiment (ACE) which is providing precise middle troposphere to the lower thermosphere measurements of the Earth's upper troposphere to lower mesosphere with the solar occultation technique. The primary instrument is a 0.02 cm -1 resolution Fourier transform spectrometer covering 750-4400 cm -1 simultaneously. ACE also known as SCISAT 1 is a Canadian lead mission launched into a 74° inclined orbit at 650 km altitude on August 12, 2003 by a U.S.-supplied Pegasus vehicle. Additional measurements are obtained with a UV-visible spectrometer and two imagers providing measurements at 0.525 and 1.02 microns.
BibTeX:
@conference{Rinsland2007,
  author = {Rinsland, C.P. and Bernath, P. and Boone, C. and Nassar, R. and Dufour, G. and Clerbaux, C.},
  title = {Atmospheric Chemistry Experiment (ACE) measurements of the upper troposphere and stratosphere},
  journal = {European Space Agency, (Special Publication) ESA SP},
  year = {2007}
}
Abstract: We report measurements of hydrogen peroxide (H2O2) profiles from infrared solar occultation spectra recorded at 0.02 cm-1 resolution by the atmospheric chemistry experiment (ACE) during 2004 and 2005. Mixing ratios as high as 1.7 ppbv (1 ppbv=1×10-9 per unit volume) were measured in the subtropical troposphere. Back trajectories, fire count statistics, and simultaneous measurements of other species from the same occultation provide evidence that the elevated H2O2 mixing ratios originated from a young biomass-burning plume. The ACE time series show only a few cases with elevated H2O2 mixing ratios likely because of the short lifetime of H2O2 and the limited sampling during biomass-burning time periods. © 2007 Elsevier Ltd. All rights reserved.
BibTeX:
@article{Rinsland2007a,
  author = {Rinsland, C.P. and Coheur, P.F. and Herbin, H. and Clerbaux, C. and Boone, C. and Bernath, P. and Chiou, L.S.},
  title = {Detection of elevated tropospheric hydrogen peroxide (H2O2) mixing ratios in atmospheric chemistry experiment (ACE) subtropical infrared solar occultation spectra},
  journal = {Journal of Quantitative Spectroscopy and Radiative Transfer},
  year = {2007},
  volume = {107},
  pages = {340-348},
  doi = {10.1016/j.jqsrt.2007.02.009}
}
Abstract: Simultaneous ACE (Atmospheric Chemistry Experiment) upper tropospheric CO, C2H6, HCN, CH3Cl, CH4, C2H2, CH3OH, HCOOH, and OCS measurements show plumes up to 185 ppbv (10-9 per unit volume) for CO, 1.36 ppbv for C2H6, 755 pptv (10-12 per unit volume) for HCN, 1.12 ppbv for CH3Cl, 1.82 ppmv (10-6 per unit volume) for CH4, 0.178 ppbv for C2H2, 3.89 ppbv for CH3OH, 0.843 ppbv for HCOOH, and 0.48 ppbv for OCS in western Canada and Alaska at 50°N-68°N latitude between 29 June and 23 July 2004. Enhancement ratios and emission factors for HCOOH, CH3OH, HCN, C2H6, and OCS relative to CO at 250-350 hPa are inferred from measurements of young plumes compared with lower mixing ratios assumed to represent background conditions based on a CO emission factor derived from boreal measurements. Results are generally consistent with the limited data reported for various vegetative types and emission phases measured in extratropical forests including boreal forests. The low correlation between fire product emission mixing ratios and the SF6 mixing ratio is consistent with no significant SF6 emissions from the biomass fires. Copyright 2007 by the American Geophysical Union.
BibTeX:
@article{Rinsland2007b,
  author = {Rinsland, C.P. and Dufour, G. and Boone, C.D. and Bernath, P.F. and Chiou, L. and Coheur, P.-F. and Turquety, S. and Clerbaux, C.},
  title = {Satellite boreal measurements over Alaska and Canada during June-July 2004: Simultaneous measurements of upper tropospheric CO, C2H6, HCN, CH3Cl, CH4, C2H2, CH3OH, HCOOH, OCS, and SF6 mixing ratios},
  journal = {Global Biogeochemical Cycles},
  year = {2007},
  volume = {21},
  article number = {GB3008},
  doi = {10.1029/2006GB002795}
}
Abstract: We present measurements of He-broadening parameters for the R(0) and P(2) lines in the fundamental band of 13CO at different temperatures between 12 K and room temperature. The broadening parameters are determined, taking into account confinement narrowing, by simultaneous least-squares fitting of spectra recorded using a frequency stabilized diode laser spectrometer. The pressure broadening cross sections are deduced and compared to close-coupling calculations and earlier results obtained for rotational transitions of 12CO. © 2007 Elsevier Inc. All rights reserved.
BibTeX:
@article{Thibault2007,
  author = {Thibault, F. and Mantz, A.W. and Claveau, C. and Henry, A. and Valentin, A. and Hurtmans, D.},
  title = {Broadening of the R(0) and P(2) lines in the 13CO fundamental by helium atoms from 300 K down to 12 K: Measurements and comparison with close-coupling calculations},
  journal = {Journal of Molecular Spectroscopy},
  year = {2007},
  volume = {246},
  pages = {118-125},
  doi = {10.1016/j.jms.2007.09.001}
}
Abstract: Assignment of an HDO line list extracted from a recently measured H2O/HDO/D2O Fourier transform absorption spectrum recorded in the 11 600-23 000 cm-1 region by Bach et al. (M. Bach, S. Fally, P.-F. Coheur, M. Carleer, A. Jenouvrier, A.C. Vandaele, J. Mol. Spectrosc. 232 (2005) 341-350.) is presented. More than 94% of the 3256 lines are given quantum number assignments and ascribed to line absorption by HDO; most of the remaining lines are actually due to D2O. High accuracy variational predictions of line positions and intensities are used for the spectral assignment process. Assignments to the ν1 + 5ν3, 2ν2 + 5ν3, ν1 + ν2 + 3ν3 and ν1 + 6ν3 bands are presented for the first time. Comparisons are made with published ICLAS spectra covering the same spectral region and suggestions made for its recalibration. The results are used to illustrate the dynamical behaviour of highly excited vibrational states of HDO and to discuss previous vibrational assignments to high lying rotation-vibration states of this system. © 2007 Elsevier Inc. All rights reserved.
BibTeX:
@article{Voronin2007,
  author = {Voronin, B.A. and Naumenko, O.V. and Carleer, M. and Coheur, P.-F. and Fally, S. and Jenouvrier, A. and Tolchenov, R.N. and Vandaele, A.C. and Tennyson, J.},
  title = {HDO absorption spectrum above 11 500 cm-1: Assignment and dynamics},
  journal = {Journal of Molecular Spectroscopy},
  year = {2007},
  volume = {244},
  pages = {87-101},
  doi = {10.1016/j.jms.2007.03.008}
}
Abstract: Global distributions of nitric acid (HNO3) partial columns in the troposphere and the stratosphere are shown for the first time. HNO3 vertical profiles are retrieved from a set of high-resolution infrared spectra, measured by the nadir-viewing Interferometric Monitor for Greenhouse Gases (IMG) instrument onboard the ADEOS satellite. Ten successive days of IMG operation in April 1997 are analyzed, yielding quasi-global distributions. We show that the IMG measurements contain between 0.7 and 1.8 independent pieces of information on the HNO3 vertical distribution; the extent of which depends on the observed scene. In the tropics and the midlatitudes, tropospheric and stratospheric columns can be separated, whereas, in the colder polar regions, the total column is the most relevant quantity. A detailed error budget reveals that the accuracy on the profile measurements ranges from 5-15% in the stratosphere to about 20-30% in the middle troposphere, and as much as 60% in the lowermost troposphere where the measurements are less sensitive. The global distributions of tropospheric and stratospheric partial columns are presented and discussed. In the stratosphere we measure higher columns at both poles than in the intertropical belt, as expected for the period in April analyzed here. In the troposphere, the zonal distributions show elevated values nearby NOx source regions, such as central Europe, the Eastern coast of the United States, and the North-West of India. Typical profiles with mixing ratios up to 2 ppbv in the boundary layer and 1 ppbv in the free troposphere are identified. These novel results indicate a possible role of HNO3 in the long-range transport of active nitrogen and open promising perspectives for future space missions dedicated to atmospheric chemistry. Copyright 2007 by the American Geophysical Union.
BibTeX:
@article{Wespes2007,
  author = {Wespes, C. and Hurtmans, D. and Herbin, H. and Barret, B. and Turquety, S. and Hadji-Lazaro, J. and Clerbaux, C. and Coheur, P.-F.},
  title = {First global distributions of nitric acid in the troposphere and the stratosphere derived from infrared satellite measurements},
  journal = {Journal of Geophysical Research Atmospheres},
  year = {2007},
  volume = {112},
  article number = {D13311},
  doi = {10.1029/2006JD008202}
}
Abstract: Chlorophyll a retrieval from satellite is based on algorithms that convert the phytoplankton absorption into chlorophyll a by means of the specificphytoplankton absorption. This factor has been found to be highly variable, spatially and seasonally. The variability of the chlorophyll a-specific phytoplankton absorption in Belgian waters (Southern North Sea) was investigated to determine how it is affecting the chlorophyll a retrieval from satellite information. The Southern Bight of the North Sea is a very dynamic area influenced by river discharges and characterised by highly variable chlorophyll, suspended matter and coloured dissolved organic matter absorption. The impact of using a mean value of specificphytoplankton absorption as usually done instead of the real one in chlorophyll a retrieval was estimated and found to be significant (underestimation up to 70% at 665 nm).
BibTeX:
@conference{Astoreca2006,
  author = {Astoreca, R. and Rousseau, V. and Lancelot, C.},
  title = {Specific phytoplankton absorption variability and implication for chlorophyll a retrieval in Belgian waters (Southern North Sea)},
  journal = {European Space Agency, (Special Publication) ESA SP},
  year = {2006}
}
Abstract: Relating to a conjecture on the decomposability of positive maps in 3 ⊗ 3, we solve the open problem of the existence of (5, 5) and (6, 6) PPT edge states. © 2006 Elsevier B.V. All rights reserved.
BibTeX:
@article{Clarisse2006,
  author = {Clarisse, L.},
  title = {Construction of bound entangled edge states with special ranks},
  journal = {Physics Letters, Section A: General, Atomic and Solid State Physics},
  year = {2006},
  volume = {359},
  pages = {603-607},
  doi = {10.1016/j.physleta.2006.07.045}
}
Abstract: Robustness measures as introduced by Vidal and Tarrach (1999 Robustness of entanglement Phys. Rev. A 59 141-55) quantify the extent to which entangled states remain entangled under mixing. Analogously, we introduce here the Schmidt robustness and the random Schmidt robustness. The latter notion is closely related to the construction of Schmidt balls around the identity. We analyse the situation for pure states and provide nontrivial upper and lower bounds. Upper bounds to the random Schmidt-2 robustness allow us to construct a particularly simple distillability criterion. We present two conjectures, the first one is related to the radius of inner balls around the identity in the convex set of Schmidt number n-states. We also conjecture a class of optimal Schmidt witnesses for pure states. © 2006 IOP Publishing Ltd.
BibTeX:
@article{Clarisse2006c,
  author = {Clarisse, L.},
  title = {On the Schmidt robustness of pure states},
  journal = {Journal of Physics A: Mathematical and General},
  year = {2006},
  volume = {39},
  pages = {4239-4249},
  doi = {10.1088/0305-4470/39/16/010}
}
Abstract: An important open problem in quantum information theory is the question of the existence of NPT bound entanglement. In the past years, little progress has been made, mainly because of the lack of mathematical tools to address the problem, (i) In an attempt to overcome this, we show how the distillability problem can be reformulated as a special instance of the separability problem, for which a large number of tools and techniques are available. (ii) Building up to this we also show how the problem can be formulated as a Schmidt number problem. (iii) A numerical method for detecting distillability is presented and strong evidence is given that all 1-copy undistillable Werner states are also 4-copy undistillable. (iv) The same method is used to estimate the volume of distillable states, and the results suggest that bound entanglement is primarily a phenomenon found in low dimensional quantum systems. (v) Finally, a set of one parameter states is presented which we conjecture to exhibit all forms of distillability. © Rinton Press.
BibTeX:
@article{Clarisse2006a,
  author = {Clarisse, L.},
  title = {The distillability problem revisited},
  journal = {Quantum Information and Computation},
  year = {2006},
  volume = {6},
  pages = {539-560}
}
Abstract: Recently, P. Wocjan and M. Horodecki [Open Syst. Inf. Dyn. 12, 331 (2005)] gave a characterization of combinatorially independent permutation separability criteria. Combinatorial independence is a necessary condition for permutations to yield truly independent criteria meaning that no criterion is strictly stronger that any other. In this paper we observe that some of these criteria are still dependent and analyze why these dependencies occur. To remove them we introduce an improved necessary condition and give a complete classification of the remaining permutations. We conjecture that the remaining class of criteria only contains truly independent permutation separability criteria. Our conjecture is based on the proof that for two, three and four parties all these criteria are truly independent and on numerical verification of their independence for up to 8 parties. It was commonly believed that for three parties there were 9 independent criteria, here we prove that there are exactly 6 independent criteria for three parties and 22 for four parties. © Rinton Press.
BibTeX:
@article{Clarisse2006b,
  author = {Clarisse, L. and Wocjan, P.},
  title = {On independent permutation separability criteria},
  journal = {Quantum Information and Computation},
  year = {2006},
  volume = {6},
  pages = {277-288}
}
Abstract: We propose to combine the tropospheric measurements provided by the IASI and GOME2 instruments aboard METOP, together with data from ground-based stations, airborne and spaceborne remote sensors, along with atmospheric chemistry models (CTMs) in order to improve our knowledge of processes constraining the chemical composition of the troposphere and to study the regional and global scale air quality. The measurements of ozone (O 3), carbon monoxide (CO), nitrogen dioxide (NO2), formaldehyde (CH2O), and methane (CH4) will be used in conjunction with the 3D tropospheric LMDz-INCA, MOZART, IMAGES and CHIMERE CTM models, using data assimilation and inversion modeling techniques, to study the global distribution of these species and to derive improved emissions estimates. Before the METOP launch, all the tools developed in the framework of this project will be used to analyse the AURA TES and OMI tropospheric products. After the launch of METOP, the data provided by both satellites will then be analyzed with the CTMs. The resulting global distributions will be used to perform detailed studies of the role of biomass burning in the budget of tropospheric species, the emissions of ozone precursors, the role of convective transport of pollutants, and its consequences in terms of air quality.
BibTeX:
@conference{Clerbaux2006,
  author = {Clerbaux, C. and Turquety, S. and Hadji-Lazaro, J. and Granier, C. and Hauglustaine, D. and Laval, S.S. and Beekmann, M. and Orphal, J. and Bergametti, G. and Camy-Peyret, C. and Payan, S. and Coheur, P. and De Mazière, M. and Müller, J.-F. and Prunet, P. and Klonecki, A.},
  title = {French/belgian scientific contribution to tropospheric studies using the metop sensors},
  journal = {European Space Agency, (Special Publication) ESA SP},
  year = {2006}
}
Abstract: A non-empirical algorithm is presented to retrieve the optical depth in the 750-1250 cm -1 spectral range, of aerosol located in the boundary layer over the ocean, from nadir high-resolution radiance spectra in the thermal infrared. The algorithm is based on a line-by-line radiative transfer forward model and used the Optimal Estimation Method for the retrieval. Its performance strongly depends on the quality of the a priori temperature and H 2O atmospheric profiles. To demonstrate the relevance of the algorithm, distributions of maritime aerosol parameters have been retrieved from IMG/ADEOS data for December 1996, using the algorithm with the LBLRTM radiative transfer code, and ERA40 (ECMWF) a priori atmospheric profiles and surface conditions. © 2005 COSPAR.
BibTeX:
@article{Kruglanski2006,
  author = {Kruglanski, M. and De Mazière, M. and Vandaele, A.C. and Hurtmans, D.},
  title = {Boundary layer aerosol retrieval from thermal infrared nadir sounding - Preliminary results},
  journal = {Advances in Space Research},
  year = {2006},
  volume = {37},
  pages = {2160-2165},
  doi = {10.1016/j.asr.2005.08.032}
}
Abstract: Total chlorine (CITOT) in the stratosphere has been determined using the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) measurements of HCl, ClONO2, CH3Cl, CCl4, CCl3F (CFC-11), CCl2F2 (CFC-12), CHClF2 (HCFC-22), CCl2FCClF2 (CFC-113), CH3CClF2 (HCFC-142b), COClF, and ClO supplemented by data from several other sources, including both measurements and models. Separate chlorine inventories were carried out in five latitude zones (60°-82°N, 30°-60°N, 30°S-30°N, 30°-60°S, and 60°-82°S), averaging the period of February 2004 to January 2005 inclusive, when possible, to deal with seasonal variations. The effect of diurnal variation was avoided by only using measurements taken at local sunset. Mean stratospheric ClTOT values of 3.65 ppbv were determined for both the northern and southern midlatitudes (with an estimated 1σ, accuracy of ±0.13 ppbv and a precision of ±.09 ppbv), accompanied by a slightly lower value in the tropics and slightly higher values at high latitudes. Stratospheric ClTOT profiles in all five latitude zones are nearly linear with a slight positive slope in ppbv /km. Both the observed slopes and pattern of latitudinal variation can be interpreted as evidence of the beginning of a decline in global stratospheric chlorine, which is qualitatively consistent with the mean stratospheric circulation pattern and time lag necessary for transport. Copyright 2006 by the American Geophysical Union.
BibTeX:
@article{Nassar2006,
  author = {Nassar, R. and Bernath, P.F. and Boone, C.D. and Clerbaux, C. and Coheur, P.F. and Dufour, G. and Froidevaux, L. and Mahieu, E. and McConnell, J.C. and McLeod, S.D. and Murtagh, D.P. and Rinsland, C.P. and Semeniuk, K. and Skelton, R. and Walker, K.A. and Zander, R.},
  title = {A global inventory of stratospheric chlorine in 2004},
  journal = {Journal of Geophysical Research Atmospheres},
  year = {2006},
  volume = {111},
  article number = {D22312},
  doi = {10.1029/2006JD007073}
}
BibTeX:
@conference{Rinsland2006,
  author = {Rinsland, C. and Bernath, P. and Boone, C. and Clerbaux, C. and Turquety, S.},
  title = {Upper tropospheric measurements of biomass burning emissions with the Atmospheric Chemistry Experiment (ACE) Fourier transform spectrometer},
  journal = {European Space Agency, (Special Publication) ESA SP},
  year = {2006}
}
Abstract: The first space-based measurements of upper tropospheric (110-300 hPa) formic acid (HCOOH) are reported from 0.02 cm-1 resolution Atmospheric Chemistry Experiment (ACE) Fourier transform spectrometer solar occultation measurements at 16°S-43°S latitude during late September to early October in 2004 and 2005. A maximum upper tropospheric HCOOH mixing ratio of 3.13 ± 0.02 ppbv (1 ppbv = 10-9 per unit volume), 1 sigma, at 10.5 km altitude was measured during 2004 at 29.97°S latitude and a lower maximum HCOOH mixing ratio of 2.03 ± 0.28 ppbv, at 9.5 km altitude was measured during 2005. Fire counts, back trajectories, and correlations of HCOOH mixing ratios with ACE simultaneous measurements of other fire products confirm the elevated HCOOH mixing ratios originated primarily from tropical fire emissions. A HCOOH emission factor relative to CO of 1.99 ± 1.34 g kg-1 during 2004 in upper tropospheric plumes is inferred from a comparison with lower mixing ratios measured during the same time period assuming HITRAN 2004 spectroscopic parameters. Copyright 2006 by the American Geophysical Union.
BibTeX:
@article{Rinsland2006a,
  author = {Rinsland, C.P. and Boone, C.D. and Bernath, P.F. and Mahieu, E. and Zander, R. and Dufour, G. and Clerbaux, C. and Turquety, S. and Chiou, L. and McConnell, J.C. and Neary, L. and Kaminski, J.W.},
  title = {First space-based observations of formic acid (HCOOH): Atmospheric Chemistry Experiment austral spring 2004 and 2005 Southern Hemisphere tropical-mid-latitude upper tropospheric measurements},
  journal = {Geophysical Research Letters},
  year = {2006},
  volume = {33},
  article number = {L23804},
  doi = {10.1029/2006GL027128}
}
Abstract: An emission spectrum recorded in an oxyacetylene torch [P.-F. Coheur, P.F. Bernath, M. Carleer, R. Colin, O.L. Polyansky, N.F. Zobov, S.V. Shirin, R.J. Barber, J. Tennyson, J. Chem. Phys. 122 (2005) 074307] is analyzed for the region covering stretching fundamentals and associated hot bands of water. Many lines could be assigned on the basis of previously determined energy levels. New assignments made with a new variational linelist allow a further 800 energy levels covering 15 vibrational states and rotations up to J = 32 to be assigned. A simultaneous re-analysis of previously reported sunspot absorption spectra leads to the assignment of 581 further lines in the L-band spectrum and 67 in the N-band spectrum. © 2006 Elsevier Inc. All rights reserved.
BibTeX:
@article{Zobov2006,
  author = {Zobov, N.F. and Shirin, S.V. and Polyansky, O.L. and Barber, R.J. and Tennyson, J. and Coheur, P.-F. and Bernath, P.F. and Carleer, M. and Colin, R.},
  title = {Spectrum of hot water in the 2000-4750 cm-1 frequency range},
  journal = {Journal of Molecular Spectroscopy},
  year = {2006},
  volume = {237},
  pages = {115-122},
  doi = {10.1016/j.jms.2006.03.001}
}
Abstract: The Southern Bight of the North Sea is characterised by a large influence of river inputs, which results in eutrophication of the area. High concentrations of plankton biomass and suspended matter have been reported for this area, in relation with blooms of different species and resuspension of bottom sediments. In spring the haptophyte Phaeocystis globosa blooms throughout the area reaching up to 30 mg Chlorophyll m-3 or more nearshore. This event is followed in June by red tides of the dinoflagellate Noctiluca scintillans. These blooms are concurrent with different species of diatoms. The strong optical signature of these blooms is clear to human observers making them potentially detectable in satellite imagery. As a first step in this direction, sampling has been carried out in the area, during Phaeocystis and Noctiluca blooms in 2003 and 2004. Phytoplankton pigments and inherent optical properties (particle, detrital and phytoplankton absorption) have been measured spectrophotometrically, and in situ using an ac-9 for total absorption and particle scattering. Field data were compared with optical properties of pure species obtained in laboratory. In parallel, water-leaving reflectance has been also measured. In this paper we characterise the optical signatures of diatoms, Phaeocystis and Noctiluca and their contribution to total absorption. The impact on water-leaving reflectance spectra is evaluated; in order to assess the conditions in which remote sensing can provide information for monitoring the timing, extent and magnitude of blooms in this coastal area.
BibTeX:
@conference{Astoreca2005,
  author = {Astoreca, R. and Rousseau, V. and Ruddick, K. and Van Mol, B. and Parent, J.-Y. and Lancelot, C.},
  title = {Optical properties of algal blooms in an eutrophicated coastal area and its relevance to remote sensing},
  journal = {Proceedings of SPIE - The International Society for Optical Engineering},
  year = {2005},
  volume = {5885},
  article number = {58850V},
  pages = {1-11},
  doi = {10.1117/12.615160}
}
Abstract: This work presents new measurements of HDO line parameters in the near-infrared and visible regions (11 500-23 000 cm-1). The measurements consist in high-resolution Fourier transform absorption spectra of H2O/HDO/D2O vapor mixtures, obtained using a long absorption path. Spectra with and without nitrogen as the buffer gas were recorded. Due to the simultaneous presence of the three isotopologues H 2O, D2O, and HDO, the H2O lines removal and the D2O lines identification were two necessary preliminary steps to derive the HDO line parameters. The D2O contribution was small and confined to the well-known 4ν1 + ν3 band. An extensive listing of HDO spectroscopic parameters was obtained, for the first time, by fitting some 3256 observed lines to Voigt line profiles. The list contains calibrated line positions, absorption cross-sections and, for many of the lines, N2-broadening coefficients, as well as N 2-induced frequency shifts. As a result of the low HDO vapor pressures, it was not possible to retrieve the self-broadening parameters. The list is available on the http://www.ulb.ac.be/cpm website. © 2005 Elsevier Inc. All rights reserved.
BibTeX:
@article{Bach2005,
  author = {Bach, M. and Fally, S. and Coheur, P.-F. and Carleer, M. and Jenouvrier, A. and Vandaele, A.C.},
  title = {Line parameters of HDO from high-resolution Fourier transform spectroscopy in the 11 500-23 000 cm-1 spectral region},
  journal = {Journal of Molecular Spectroscopy},
  year = {2005},
  volume = {232},
  pages = {341-350},
  doi = {10.1016/j.jms.2005.04.018}
}
Abstract: Collision-induced line narrowing, which has been discovered in the 1950s and investigated thoroughly in the laboratory since then, has yet never been taken into account in the spectroscopic remote sensing of the atmosphere. This work investigates the effect of collision-induced line narrowing onto the retrieval of HCl and HF vertical profiles from ground-based solar absorption FTIR measurements made at the NDSC station of the Jungfraujoch (46.5°N, 8°E and 3580 m above see level). The retrievals are performed with the Atmosphit software, recently developed at the Université Libre de Bruxelles. It is presented in this paper for the first time and is validated against the widely used SFIT2 software. The impact of the line narrowing onto the retrieval of HCl and HF vertical profiles is examined relying on careful information content and error budget analyses. We report that the effect is relatively weak for HCl but significant for HF. Confirmation of the need to take the line narrowing into account for the retrieval of vertical profiles from ground-based FTIR spectra is given by comparison with data from the HALOE space borne instrument, rather insensitive to this spectroscopic effect. © 2005 Elsevier Ltd. All rights reserved.
BibTeX:
@article{Barret2005a,
  author = {Barret, B. and Hurtmans, D. and Carleer, M.R. and De Mazière, M. and Mahieu, E. and Coheur, P.-F.},
  title = {Line narrowing effect on the retrieval of HF and HCl vertical profiles from ground-based FTIR measurements},
  journal = {Journal of Quantitative Spectroscopy and Radiative Transfer},
  year = {2005},
  volume = {95},
  pages = {499-519},
  doi = {10.1016/j.jqsrt.2004.12.005}
}
Abstract: This paper presents the first global distributions of CO vertical profiles retrieved from a thermal infrared FTS working in the nadir geometry. It is based on the exploitation of the high resolution and high quality spectra measured by the Interferometric Monitor of Greenhouse gases (IMG) which flew onboard the Japanese ADEOS platform in 1996-1997. The retrievals are performed with an algorithm based on the Optimal Estimation Method (OEM) and are characterized in terms of vertical sensitivity and error budget. It is found that most of the IMG measurements contain between 1.5 and 2.2 independent pieces of information about the vertical distribution of CO from the lower troposphere to the upper troposphere-lower stratosphere (UTLS). The retrievals are validated against coincident NOAA/CMDL in situ surface measurements and NDSC/FTIR total columns measurements. The retrieved global distributions of CO are also found to be in good agreement with the distributions modeled by the GEOS-CHEM 3D CTM, highlighting the ability of IMG to capture the horizontal as well as the vertical structure of the CO distribution. © 2005 Author(s). This work is licensed under a Creative Commons License.
BibTeX:
@article{Barret2005,
  author = {Barret, B. and Turquety, S. and Hurtmans, D. and Clerbaux, C. and Hadji-Lazaro, J. and Bey, I. and Auvray, M. and Coheur, P.-F.},
  title = {Global carbon monoxide vertical distributions from spaceborne high-resolution FTIR nadir measurements},
  journal = {Atmospheric Chemistry and Physics},
  year = {2005},
  volume = {5},
  pages = {2901-2914}
}
Abstract: SCISAT-1, also known as the Atmospheric Chemistry Experiment (ACE), is a Canadian satellite mission for remote sensing of the Earth's atmosphere. It was launched into low Earth circular orbit (altitude 650 km, inclination 74°) on 12 Aug. 2003. The primary ACE instrument is a high spectral resolution (0.02 cm-1) Fourier Transform Spectrometer (FTS) operating from 2.2 to 13.3 μm (750-4400 cm-1). The satellite also features a dual spectrophotometer known as MAESTRO with wavelength coverage of 285-1030 nm and spectral resolution of 1-2 nm. A pair of filtered CMOS detector arrays records images of the Sun at 0.525 and 1.02 μm. Working primarily in solar occultation, the satellite provides altitude profile information (typically 10-100 km) for temperature, pressure, and the volume mixing ratios for several dozen molecules of atmospheric interest, as well as atmospheric extinction profiles over the latitudes 85°N to 85°S. This paper presents a mission overview and some of the first scientific results. Copyright 2005 by the American Geophysical Union.
BibTeX:
@article{Bernath2005,
  author = {Bernath, P.F. and McElroy, C.T. and Abrams, M.C. and Boone, C.D. and Butler, M. and Camy-Peyret, C. and Carleer, M. and Clerbaux, C. and Coheur, P.-F. and Colin, R. and DeCola, P. and DeMazière, M. and Drummond, J.R. and Dufour, D. and Evans, W.F.J. and Fast, H. and Fussen, D. and Gilbert, K. and Jennings, D.E. and Llewellyn, E.J. and Lowe, R.P. and Mahieu, E. and McConnell, J.C. and McHugh, M. and McLeod, S.D. and Michaud, R. and Midwinter, C. and Nassar, R. and Nichitiu, F. and Nowlan, C. and Rinsland, C.P. and Rochon, Y.J. and Rowlands, N. and Semeniuk, K. and Simon, P. and Skelton, R. and Sloan, J.J. and Soucy, M.-A. and Strong, K. and Tremblay, P. and Turnbull, D. and Walker, K.A. and Walkty, I. and Wardle, D.A. and Wehrle, V. and Zander, R. and Zou, J.},
  title = {Atmospheric chemistry experiment (ACE): Mission overview},
  journal = {Geophysical Research Letters},
  year = {2005},
  volume = {32},
  article number = {L15S01},
  doi = {10.1029/2005GL022386}
}
Abstract: A necessary and sufficient condition for one-distillability is formulated in terms of decomposable positive maps. As an application we provide insight into why all states violating the reduction criterion map are distillable and demonstrate how to construct such maps in a systematic way. We establish a connection between a number of existing results, which leads to an elementary proof for the characterization of distillability in terms of two-positive maps. ©2005 The American Physical Society.
BibTeX:
@article{Clarisse2005,
  author = {Clarisse, L.},
  title = {Characterization of distillability of entanglement in terms of positive maps},
  journal = {Physical Review A - Atomic, Molecular, and Optical Physics},
  year = {2005},
  volume = {71},
  article number = {032332},
  doi = {10.1103/PhysRevA.71.032332}
}
Abstract: The notion of entangling power of unitary matrices was introduced by Zanardi, [Phys. Rev. A 62, 030301 (2000)]. We study the entangling power of permutations, given in terms of a combinatorial formula. We show that the permutation matrices with zero entangling power are, up to local unitaries, the identity and the swap. We construct the permutations with the minimum nonzero entangling power for every dimension. With the use of orthogonal latin squares, we construct the permutations with the maximum entangling power for every dimension. Moreover, we show that the value obtained is maximum over all unitaries of the same dimension, with a possible exception for 36. Our result enables us to construct generic examples of 4-qudit maximally entangled states for all dimensions except for 2 and 6. We numerically classify, according to their entangling power, the permutation matrices of dimensions 4 and 9, and we give some estimates for higher dimensions. © 2005 The American Physical Society.
BibTeX:
@article{Clarisse2005a,
  author = {Clarisse, L. and Ghosh, S. and Severini, S. and Sudbery, A.},
  title = {Entangling power of permutations},
  journal = {Physical Review A - Atomic, Molecular, and Optical Physics},
  year = {2005},
  volume = {72},
  article number = {012314},
  doi = {10.1103/PhysRevA.72.012314}
}
Abstract: This paper presents a comprehensive analysis of the CO observations acquired during the first eight months (January to September 2004) of the ACE mission. We show that the ACE high-resolution Fourier transform spectrometer (ACE-FTS), which operates in the solar occultation geometry and covers a wide spectral interval in the infrared, provides useful measurements in both the CO 1-0 and 2-0 vibrational bands. Vertically-resolved CO concentration profiles are retrieved, extending from the mid-troposphere to the thermosphere (from about 5 to 110 km). We have analyzed the latitudinal variability of the measurements, from which various physical and chemical atmospheric processes are highlighted for further study. Copyright 2005 by the American Geophysical Union.
BibTeX:
@article{Clerbaux2005,
  author = {Clerbaux, C. and Coheur, P.-F. and Hurtmans, D. and Barret, B. and Carleer, M. and Colin, R. and Semeniuk, K. and McConnell, J.C. and Boone, C. and Bernath, P.},
  title = {Carbon monoxide distribution from the ACE-FTS solar occultation measurements},
  journal = {Geophysical Research Letters},
  year = {2005},
  volume = {32},
  article number = {L16S01},
  pages = {1-4},
  doi = {10.1029/2005GL022394}
}
Abstract: This paper presents the first retrievals and validations of ozone vertical distributions from a set of high-resolution nadir thermal infrared measurements. These were obtained by the Interferometric Monitor for Greenhouse gases (IMG) instrument, which has operated on board the Japanese ADEOS platform between 1996 and 1997. The Optimal Estimation Method is used for the retrievals, along with a priori profile and covariance matrix built from model climatologies. We compare the retrieved IMG profiles with high-vertical-resolution ozone sonde measurements. Therefore we selected a set of IMG spectra collocated to within 3° of longitude and latitude with a representative distribution of ground-based stations. We demonstrate that thanks to the two to four independent pieces of vertical information contained in the spectroscopic measurements with a maximum sensitivity in the upper troposphere-middle stratosphere, the thermal infrared nadir sounders are able to capture most of the ozone spatial and temporal variations. In particular, the latitudinal variations of the stratospheric ozone maximum are well represented in the retrievals, as are the high ozone concentrations observed in the upper troposphere- lower stratosphere at northern midlatitudes during springtime. Ozone depletion events in the Arctic vortex are also well reproduced. The measurements provide an accurate view of the tropospheric ozone content, except when the latter is very low. A detailed error budget reveals that the major part of the error in the IMG retrieved ozone profile is due to the smoothing of the true profile by the averaging kernel matrix, with additional contributions associated with the measurement noise and the inaccurate knowledge of the temperature profile and of the Instrument Line Shape (ILS). Copyright 2005 by the American Geophysical Union.
BibTeX:
@article{Coheur2005a,
  author = {Coheur, P.-F. and Barret, B. and Turquety, S. and Hurtmans, D. and Hadji-Lazaro, J. and Clerbaux, C.},
  title = {Retrieval and characterization of ozone vertical profiles from a thermal infrared nadir sounder},
  journal = {Journal of Geophysical Research Atmospheres},
  year = {2005},
  volume = {110},
  article number = {D24303},
  pages = {1-12},
  doi = {10.1029/2005JD005845}
}
Abstract: An emission spectrum of hot water with a temperature of about 3000 K is obtained using an oxy-acetylene torch. This spectrum contains a very large number of transitions. The spectrum, along with previous cooler laboratory emission spectra and an absorption spectrum recorded from a sunspot, is analyzed in the 500-2000 cm -1 region. Use of a calculated variational linelist for water allows significant progress to be made on assigning transitions involving highly excited vibrational and rotational states. In particular emission from rotationally excited states up to J=42 and vibrational levels with up to eight quanta of bending motion are assigned.
BibTeX:
@article{Coheur2005,
  author = {Coheur, P.-F. and Bernath, P.F. and Carleer, M. and Colin, R. and Polyansky, O.L. and Zobov, N.F. and Shirin, S.V. and Barber, R.J. and Tennyson, J.},
  title = {A 3000K laboratory emission spectrum of water},
  journal = {Journal of Chemical Physics},
  year = {2005},
  volume = {122},
  article number = {074307},
  doi = {10.1063/1.1847571}
}
Abstract: Fourier-transform intracavity laser absorption spectroscopy allowed five 12C13CH2Σ+- Σ+ bands, all from the ground state, to be identified in the 0.83 μm range. Their rotational analysis was performed and rotational constants are provided. Three of these bands, with origins at 11616.9684(18), 11737.2356(14), and 11761.0322(23) cm-1, have never been reported before. Their upper states are assigned to V1V2V 3v4 l4v5 l5 = 1302 020, 130113-1, and 22011 1-1, respectively. © 2004 Elsevier Inc. All rights reserved.
BibTeX:
@article{Depiesse2005,
  author = {Depiesse, C. and Di Lonardo, G. and Fayt, A. and Fusina, L. and Hurtmans, D. and Robert, S. and Tamassia, F. and Vander Auwera, J. and Baldan, A. and Herman, M.},
  title = {New combination bands in12C13CH2 around 0.83 μm recorded using FT-ICLAS},
  journal = {Journal of Molecular Spectroscopy},
  year = {2005},
  volume = {229},
  pages = {137-139},
  doi = {10.1016/j.jms.2004.08.006}
}
Abstract: HFC-134a (CF3CH2F) is the most rapidly growing hydrofluorocarbon in terms of atmospheric abundance. It is currently used in a large number of household refrigerators and air-conditioning systems and its concentration in the atmosphere is forecast to increase substantially over the next 50-100 years. Previous estimates of its radiative forcing per unit concentration have differed significantly ∼25%. This paper uses a two-step approach to resolve this discrepancy. In the first step six independent absorption cross section datasets are analysed. We find that, for the integrated cross section in the spectral bands that contribute most to the radiative forcing, the differences between the various datasets are typically smaller than 5% and that the dependence on pressure and temperature is not significant. A "recommended" HFC-134a infrared absorption spectrum was obtained based on the average band intensities of the strongest bands. In the second step, the "recommended" HFC-134a spectrum was used in six different radiative transfer models to calculate the HFC-134a radiative forcing efficiency. The clear-sky instantaneous radiative forcing, using a single global and annual mean profile, differed by 8%, between the 6 models, and the latitudinally-resolved adjusted cloudy sky radiative forcing estimates differed by a similar amount. We calculate that the radiative forcing efficiency of HFC-134a is 0.16 ± 0.02 Wm-2 ppbv-1. © 2004 Elsevier Ltd. All rights reserved.
BibTeX:
@article{Forster2005,
  author = {Forster, P.M.De.F. and Burkholder, J.B. and Clerbaux, C. and Coheur, P.F. and Dutta, M. and Gohar, L.K. and Hurley, M.D. and Myhre, G. and Portmann, R.W. and Shine, K.P. and Wallington, T.J. and Wuebbles, D.},
  title = {Resolution of the uncertainties in the radiative forcing of HFC-134a},
  journal = {Journal of Quantitative Spectroscopy and Radiative Transfer},
  year = {2005},
  volume = {93},
  pages = {447-460},
  doi = {10.1016/j.jqsrt.2004.08.038}
}
Abstract: A set-up combining a high resolution Fourier transform interferometer and a quadrupole mass spectrometer with a supersonic jet expansion produced thanks to a large turbomolecular pumping unit is described. A rotational temperature close to 3 K is demonstrated. Vibration-vibration energy transfer in the expansion affecting the v2 = 1 state in N2O is monitored in the presence of various collision partners. The transfer from the v 2 = 1 state of N2O towards the quasi resonant, lower energy v2 = 1 state of OCS is demonstrated, in particular. © 2005 Elsevier B.V. All rights reserved.
BibTeX:
@article{Herman2005,
  author = {Herman, M. and Didriche, K. and Rizopoulos, A. and Hurtmans, D.},
  title = {FT-jet spectroscopy: Vibrational energy transfer in N2O},
  journal = {Chemical Physics Letters},
  year = {2005},
  volume = {414},
  pages = {282-286},
  doi = {10.1016/j.cplett.2005.08.087}
}
Abstract: The content of the current (2003) version, GEISA/IASI-03, of the computer-accessible spectroscopic database, GEISA/IASI, is described. This "system" or database is comprised of three independent spectroscopic archives, which are (a) a database of individual spectral line parameters on 14 molecules, H2O, CO2, O3, N2O, CO, CH4, O2, NO, SO2, NO2, HNO3, OCS, C2H2, N2, and the related 51 isotopomers and isotopologues, representing 702,550 entries, in the spectral range 599-3001 cm-1, (b) a database of spectral absorption cross-sections (6,572,329 entries related to six molecules, CFC-11, CFC-12, CFC-14, HCFC-22, N2O5, CCl4), and a catalogue of microphysical and optical properties (mainly, the refractive indices) of atmospheric aerosols. The modifications and improvements, which have been implemented since the earlier editions of this database, in terms of content and management, have been explained in detail. GEISA/IASI has been created with the specific purpose of assessing the capability of measurement by the IASI instrument within the designated goals of ISSWG in the frame of the CNES/EUMETSAT European Polar System preparation. All the archived data can be handled through a user-friendly associated management software, which is posted on the ARA/LMD group web site at http://ara.lmd.polyechnique.fr. © 2005 Elsevier Ltd. All rights reserved.
BibTeX:
@article{Jacquinet-Husson2005,
  author = {Jacquinet-Husson, N. and Scott, N.A. and Chédin, A. and Garceran, K. and Armante, R. and Chursin, A.A. and Barbe, A. and Birk, M. and Brown, L.R. and Camy-Peyret, C. and Claveau, C. and Clerbaux, C. and Coheur, P.F. and Dana, V. and Daumont, L. and Debacker-Barilly, M.R. and Flaud, J.M. and Goldman, A. and Hamdouni, A. and Hess, M. and Jacquemart, D. and Köpke, P. and Mandin, J.Y. and Massie, S. and Mikhailenko, S. and Nemtchinov, V. and Nikitin, A. and Newnham, D. and Perrin, A. and Perevalov, V.I. and Régalia-Jarlot, L. and Rublev, A. and Schreier, F. and Schult, I. and Smith, K.M. and Tashkun, S.A. and Teffo, J.L. and Toth, R.A. and Tyuterev, Vl.G. and Vander Auwera, J. and Varanasi, P. and Wagner, G.},
  title = {The 2003 edition of the GEISA/IASI spectroscopic database},
  journal = {Journal of Quantitative Spectroscopy and Radiative Transfer},
  year = {2005},
  volume = {95},
  pages = {429-467},
  doi = {10.1016/j.jqsrt.2004.12.004}
}
Abstract: We present a complete study on four methane lines for two atmospheric micro-windows (in the ν2 + ν4 absorption band) used for the determination of atmospheric methane concentrations with ground-based Fourier transform spectrometers. Thanks to our tunable diode laser (TDL) spectrometer with active wavenumber control and step-by-step recording mode we have improved the accuracy on intensity, broadening, narrowing, and pressure shift parameters. To make our results directly useable in atmospheric models which usually assume a Voigt line shape, we have parameterised an effective-broadening parameter γVoigt (P) for each line and each gas mixture (CH4-N2 and CH4-O 2). When this parameterisation is used to fit a "true" line profile, the same concentration as with more sophisticated models is retrieved using a consistent set of spectroscopic parameters in both approaches. © 2005 Elsevier Inc. All rights reserved.
BibTeX:
@article{Mondelain2005,
  author = {Mondelain, D. and Chelin, P. and Valentin, A. and Hurtmans, D. and Camy-Peyret, C.},
  title = {Line profile study by diode laser spectroscopy in the 12CH 4 ν2 + ν4 band},
  journal = {Journal of Molecular Spectroscopy},
  year = {2005},
  volume = {233},
  pages = {23-31},
  doi = {10.1016/j.jms.2005.05.012}
}
BibTeX:
@article{Montecino2005,
  author = {Montecino, V. and Astoreca, R. and Alarcón, G. and Retamal, L. and Pizarro, G.},
  title = {Erratum: Bio-optical characteristics and primary productivity during upwelling and non-upwelling conditions in a highly productive coastal ecosystem off central Chile (∼361S) (Deep-Sea Research II (2004) 51 (2413-2426) DOI: 10.1016/j.dsr2.2004.08.012)},
  journal = {Deep-Sea Research Part II: Topical Studies in Oceanography},
  year = {2005},
  volume = {52},
  pages = {373-374},
  doi = {10.1016/j.dsr2.2005.02.001}
}
Abstract: Line parameters for water vapour in natural abundance have recently been determined for the 9250-13 000 cm-1 region [M.-F. Mérienne, A. Jenouvrier, C. Hermans, A.C. Vandaele, M. Carleer, C. Clerbaux, P.-F. Coheur, R. Colin, S. Fally, M. Bach, J. Quant. Spectrosc. Radiat. Transfer 82 (2003) 99] and the 13 000-26 000 cm-1 region [P.-F. Coheur, S. Fally, M. Carleer, C. Clerbaux, R. Colin, A. Jenouvrier, M.-F. Mérienne, C. Hermans, A.C. Vandaele, J. Quant. Spectrosc. Radiat. Transfer 74 (2002) 493] using a high-resolution Fourier-transform spectrometer with a long-path absorption cell. These spectra are analysed using several techniques including variational line lists and assignments made. In total, over 15 000 lines were assigned to transitions involving more than 150 exited vibrational states of H2 16O. Twelve new vibrational band origins are determined and estimates for a further 16 are presented. © 2005 Elsevier Inc. All rights reserved.
BibTeX:
@article{Tolchenov2005,
  author = {Tolchenov, R.N. and Naumenko, O. and Zobov, N.F. and Shirin, S.V. and Polyansky, O.L. and Tennyson, J. and Carleer, M. and Coheur, P.-F. and Fally, S. and Jenouvrier, A. and Vandaele, A.C.},
  title = {Water vapour line assignments in the 9250-26 000 cm-1 frequency range},
  journal = {Journal of Molecular Spectroscopy},
  year = {2005},
  volume = {233},
  pages = {68-76},
  doi = {10.1016/j.jms.2005.05.015}
}
Abstract: The change in the energy level structure of a bent molecule as it starts to sample linear geometries has been discussed in terms of monodromy found in simple two-dimensional model problems. Infrared spectra of hot (T ∼ 3000 K) water are analysed for transitions involving states with high bending excitation which can sample linear HOH geometries. One hundred and thirty four new experimental energy levels are determined for bending states with 5 ≤ v 2≤9 including band origins for 7ν2, 8ν2 and 9ν2. Plots of those levels with J = K a show the characteristic rearrangement of energy levels predicted for a system displaying quantum monodromy. Quantum monodromy for water occurs about the ν2 = 7, J = 0 level. The barrier to linearity in H 2 16O is estimated to lie at 11 114 ± 5 cm -1. © 2005 Elsevier B.V. All rights reserved.
BibTeX:
@article{Zobov2005,
  author = {Zobov, N.F. and Shirin, S.V. and Polyansky, O.L. and Tennyson, J. and Coheur, P.-F. and Bernath, P.F. and Carleer, M. and Colin, R.},
  title = {Monodromy in the water molecule},
  journal = {Chemical Physics Letters},
  year = {2005},
  volume = {414},
  pages = {193-197},
  doi = {10.1016/j.cplett.2005.08.028}
}
BibTeX:
@article{Clerbaux2004,
  author = {Clerbaux, C. and Gille, J. and Edwards, D.},
  title = {New Directions: Infrared measurements of atmospheric pollution from space},
  journal = {Atmospheric Environment},
  year = {2004},
  volume = {38},
  pages = {4599-4601},
  doi = {10.1016/j.atmosenv.2004.05.005}
}
Abstract: Simultaneous ultraviolet (UV) and infrared (IR) measurements of ozone concentration in air in the 1200-300 ppbv range have been performed using the ultraviolet absorption in the Hartley band at 0.2537 μm and the infrared absorption of a doublet at 9.507 μm in the ν3 vibration-rotation band. Infrared concentration measurements were achieved using the tunable diode laser spectrometer of LPMA in Paris with interferometric control of the emitted wavelength while the UV concentration measurements were performed with the 49PS Megatec ozone generator of the Bureau National de Métrologie (BNM). The simultaneous recording of spectra of a reference cell filled with pure distilled ozone and of a low concentration mixture inside a long absorbing path Herriott cell allows to carry out infrared concentration measurements with an accuracy of the same order as the ultraviolet ones and provides the instrumental parameters of the spectrometer corresponding to each concentration measurement, which reduces systematic errors. Within the respective absolute uncertainties proper to the two techniques, no systematic discrepancy was evidenced between the IR and the UV measurements. The ozone ultraviolet absorption coefficient value determined by Hearn (308.3±4 cm-1 atm-1) and used by the BNM and the National Institute of Standards and Technology (NIST) is confirmed by the present work. © 2004 Elsevier B.V. All rights reserved.
BibTeX:
@article{Dufour2004,
  author = {Dufour, G. and Valentin, A. and Henry, A. and Hurtmans, D. and Camy-Peyret, C.},
  title = {Concentration measurements of ozone in the 1200-300 ppbv range: An intercomparison between the BNM ultraviolet standard and infrared methods},
  journal = {Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy},
  year = {2004},
  volume = {60},
  pages = {3345-3352},
  doi = {10.1016/j.saa.2003.12.056}
}
Abstract: Room temperature absorption spectra of the gaseous (C2h) dimer of formic acid were recorded from the lowest energy fundamental, ν16, with origin at 69.2 cm-1, up to the CH overtone bands with Δv=4, with origin at 11,103 cm-1, using a high resolution Fourier transform interferometer. These spectra are complemented with liquid phase data in the NIR region. In addition, jet-cooled spectra were recorded over the range 1850-3750 cm-1. The origin of the many observed bands is listed, together with relative intensities for those recorded under jet-cooled conditions. Systematic problems encountered with vibrational assignments for bands other than fundamentals are highlighted and, as a rule, left unsolved except for the bands at 167.26 and 2586.34 cm-1 tentatively assigned to ν15+ν16-ν16 and ν5+ν22 or ν6+ν21, respectively. For the first, FIR band the assignment is supported by partly unravelling the hot band pattern around ν15 at 168.47 cm -1. The jet-cooled rotational contour of the second, MIR band was simulated, allowing the rotational temperature in the jet to be estimated to 35 K. © 2004 Elsevier B.V. All rights reserved.
BibTeX:
@article{Georges2004,
  author = {Georges, R. and Freytes, M. and Hurtmans, D. and Kleiner, I. and Vander Auwera, J. and Herman, M.},
  title = {Jet-cooled and room temperature FTIR spectra of the dimer of formic acid in the gas phase},
  journal = {Chemical Physics},
  year = {2004},
  volume = {305},
  pages = {187-196},
  doi = {10.1016/j.chemphys.2004.06.027}
}
Abstract: Two new bands, 2ν1+ν2+ν 3+2ν5 and 5ν3 with origin at 12220.692 and 12496.158cm-1, respectively, were identified on new FT-ICLAS spectra of 12C2HD and rotationally analyzed. The rotational analysis of two known bands, with origin at 12038.538 and 12234.872cm-1 was extended. Another band, 2ν 1+2ν5 with origin at 7843.6622cm-1, was identified for the first time and rotationally analyzed, from a high pressure conventional FT spectrum. Some 115 known vibrational state energies in the molecule, extending up to the visible range, were used to produce updated vibrational constants. Both a straightforward Dunham model and a global model accounting for a single anharmonic resonance, K1/255, were used. The results are discussed. © 2004 Elsevier Inc. All rights reserved.
BibTeX:
@article{Herman2004,
  author = {Herman, M. and Depiesse, C. and Di Lonardo, G. and Fayt, A. and Fusina, L. and Hurtmans, D. and Kassi, S. and Mollabashi, M. and Vander Auwera, J.},
  title = {The vibration-rotation spectrum of 12C2HD: New overtone bands and global vibrational analysis},
  journal = {Journal of Molecular Spectroscopy},
  year = {2004},
  volume = {228},
  pages = {499-510},
  doi = {10.1016/j.jms.2004.05.005}
}
Abstract: Variability of several bio-optical and photosynthetic properties of phytoplankton in the highly productive coast off Concepción, central Chile (∼36°S) was quantified during contrasting seasons at offshore, shelf, and nearshore sites. During October 1998 (upwelling) and July 1999 (non-upwelling), 21 stations were sampled for chlorophyll-a, pigment spectral light absorption, primary production, and attenuation coefficients (kλ) of downwelling irradiance (E d(λ)); kλ was used to estimate the depth of the euphotic zone (Z eu). Primary production was measured through 14C-fixation experiments using simulated in situ and in situ incubations with water from six depths within the Z eu. The photosynthetic parameters (α B, P B max) were obtained through photosynthesis-irradiance experiments with samples from two Z eu depths. Bio-optical properties showed large spatial variability during both seasons, including spectral in vivo phytoplankton absorption (a ph(λ)), pigment specific phytoplankton absorption (a*(λ)) within the upper 25 m, and water-column transmittance (T(λ)), calculated for the upper 10 m using E d(λ) at four wavelengths. Under non-upwelling conditions, a*(λ), T(λ), and α B presented higher values whereas a ph(λ) values decreased accordingly. Under upwelling conditions, primary productivity ranged from 0.7 to 7.5 g C m -2 d -1 at the coastal stations and was &lt;0.6 g C m -2 d -1 at the oceanic stations; in the non-upwelling season, values over the entire area ranged from 0.2 to 1.9 g C m -2 d -1. The significant correlations found among bio-optical properties and physiological parameters highlight both the short- and long-term changes in the area's environmental conditions. The combination of three independent biological parameters - α B, P B max, and a ph(442) - accounted for most of the horizontal and vertical variability among and within stations for each cruise. These results support a distinction of different functional zones for the two contrasting upwelling conditions. © 2004 Elsevier Ltd. All rights reserved.
BibTeX:
@article{Montecino2004,
  author = {Montecino, V. and Astoreca, R. and Alarcón, G. and Retamal, L. and Pizarro, G.},
  title = {Bio-optical characteristics and primary productivity during upwelling and non-upwelling conditions in a highly productive coastal ecosystem off central Chile (∼36°S)},
  journal = {Deep-Sea Research Part II: Topical Studies in Oceanography},
  year = {2004},
  volume = {51},
  pages = {2413-2426},
  doi = {10.1016/j.dsr2.2004.08.012}
}
Abstract: The Infrared Atmospheric Sounding Interferometer (IASI) is a nadir-viewing remote sensor due for launch on board the European Metop satellites (to be launched in 2005, 2010, and 2015). It is dedicated to the study of the troposphere and the lower stratosphere to support operational meteorology as well as atmospheric chemistry and climate studies. For this purpose, it will record high resolution atmospheric spectra in the thermal infrared, allowing the measurement of several infrared absorbing species. This paper describes the clear-sky retrieval scheme developed in the framework of the preparation of the IASI mission for the operational, near real time, retrieval Of O3, CH 4, and CO concentrations. It includes the inversion module, based on a neural network approach, as well as an error analysis module. The studies undertaken on test simulations have shown that a performance of the order of 1.5%, 2%, and 5% for the retrieval of total columns Of O3, CH4, and CO, respectively, can be achieved, and of the order of 28%, 15%, and 9% for the retrieval of partial columns Of O3 between the surface and 6, 12, and 16 km high, respectively. The efficiency of the algorithm is demonstrated on the atmospheric measurements provided by the Interferometric Monitor for Greenhouse Gases (IMG)/ADEOS, allowing to obtain the first remote-sensing simultaneous distributions of ozone and its two precursors, CO and CH4. Copyright 2004 by the American Geophysical Union.
BibTeX:
@article{Turquety2004,
  author = {Turquety, S. and Hadji-Lazaro, J. and Clerbaux, C. and Hauglustaine, D.A. and Clough, S.A. and Cassé, V. and Schlüssel, P. and Mégie, G.},
  title = {Operational trace gas retrieval algorithm for the Infrared Atmospheric Sounding Interferometer},
  journal = {Journal of Geophysical Research D: Atmospheres},
  year = {2004},
  volume = {109},
  pages = {D21301 1-19},
  doi = {10.1029/2004JD004821}
}
Abstract: We have constructed a stabilized low temperature infrared absorption cell cooled by an open cycle refrigerator, which can run with liquid nitrogen from 250 to 80 K or with liquid helium from 80 K to a few kelvin. Several CO infrared spectra were recorded at low temperature using a tunable diode laser spectrometer. These spectra were analyzed taking into account the detailed effects of collisions on the line profile when the pressure increases. We also recorded spectra at very low pressure to accurately model the diode laser emission. Spectra of the R(2) line in the fundamental band of 13CO cooled by collisions with helium buffer gas at 10.5 K and at pressures near 1 Torr have been recorded. The He-pressure broadening parameter (γ0 = 0.3 cm-1 atm-1) has been derived from the simultaneous analysis of four spectra at different pressures. © 2004 Elsevier B.V. All rights reserved.
BibTeX:
@article{Valentin2004,
  author = {Valentin, A. and Henry, A. and Claveau, C. and Camy-Peyret, C. and Hurtmans, D. and Mantz, A.W.},
  title = {Development of a stabilized low temperature infrared absorption cell for use in low temperature and collisional cooling experiments},
  journal = {Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy},
  year = {2004},
  volume = {60},
  pages = {3477-3482},
  doi = {10.1016/j.saa.2003.12.058}
}
Abstract: We present a line profile study at 150, 110 and 80 K for the R(7) line in the fundamental band of 13CO perturbed by Ar in a new stabilized low-temperature cell cooled by liquid nitrogen. The broadening, shifting and narrowing parameters are determined taking into account the absorber speed dependence by simultaneous least-squares fitting of spectra over a 4-300 Torr pressure range recorded using a frequency-stabilized diode laser spectrometer. When the cell is cooled by liquid helium the (1-0) R(2) line of 13CO in collision with helium is observed at a temperature of 6.9 K.
BibTeX:
@article{Valentin2004a,
  author = {Valentin, A. and Henry, A. and Claveau, C. and Hurtmans, D. and Mantz, A.W.},
  title = {Line profile study down to 80 K of R(7) in the13CO (1-0) band perturbed by Ar and13CO collisional cooling with he at 6.9 K},
  journal = {Molecular Physics},
  year = {2004},
  volume = {102},
  pages = {1793-1802},
  doi = {10.1080/00268970412331287007}
}
Abstract: Satellite instruments specifically designed to monitor atmospheric carbon dioxide concentrations have not been flown to date but, high-resolution infrared sounders, being launched in the next few years, may offer the possibility of at least a basic carbon dioxide monitoring capability. This paper explores the sensitivity of this new generation of advanced infrared sounders to changing carbon dioxide concentrations and also compares this with uncertainties due to the atmospheric temperature, water vapor, and minor constituent concentrations using the current background errors in numerical weather prediction models as a baseline. The sensitivity results shown are computed for the Infrared Atmospheric Sounding Interferometer (IASI), which is due to fly on the European METOP platform from 2005. We show that although the carbon dioxide signal is below or at the instrument noise for IASI and that uncertainties in temperature and water vapor errors can dominate, a careful averaging of the retrieved carbon dioxide fields over areas of 500 × 500 km2 and 2 weeks should be able to extract changes at the level of 1% or less in the total column carbon dioxide amount. We also show results of an information content study for the Atmospheric InfraRed Sounder, AIRS, data, which suggests 50 channels are adequate for inferring the tropospheric carbon dioxide amounts but that they are not sensitive to CO2 changes in the boundary layer.
BibTeX:
@article{Chedin2003,
  author = {Chédin, A. and Saunders, R. and Hollingsworth, A. and Scott, N. and Matricardi, M. and Etcheto, J. and Clerbaux, C. and Armante, R. and Crevoisier, C.},
  title = {The feasibility of monitoring CO2 from high-resoluion infrared sounders},
  journal = {Journal of Geophysical Research D: Atmospheres},
  year = {2003},
  volume = {108},
  pages = {ACH 6-1 ACH 6-19}
}
Abstract: Space-borne thermal infrared instruments working in the nadir geometry are providing spectroscopic measurements of species that impact on the chemical composition of the atmosphere and on the climate forcing: H2O, CO2, N2O, CH4, CFCs, O3, and CO. The atmospheric abundances obtained from the analysis of IMG/ADEOS measurements are discussed in order to demonstrate the potential scientific return to be expected from future missions using advanced infrared nadir sounders. Some strengths and limitations of passive infrared remote sensing from space are illustrated. © 2003 European Geosciences Union.
BibTeX:
@article{Clerbaux2003,
  author = {Clerbaux, C. and Hadji-Lazaro, J. and Turquety, S. and Mégie, G. and Coheur, P.-F.},
  title = {Trace gas measurements from infrared satellite for chemistry and climate applications},
  journal = {Atmospheric Chemistry and Physics},
  year = {2003},
  volume = {3},
  pages = {1495-1508}
}
Abstract: Infrared spectra recorded by the Atmospheric Trace Molecule Spectroscopy Experiment (ATMOS) and the Interferometric Monitor for Greenhouse Gases (IMG) remote sensors have been analyzed by means of line-by-line radiative transfer calculations in order to evaluate the possibilities offered by solar occultation and by nadir instruments to monitor the cholorofluorocarbons (CFCs) and their substitutes. The reliability of the existing spectroscopic parameters has been examined, and it was found that only laboratory parameters measured at high resolution reproduce the satellite observations well. It is shown that solar occultation spectra can give information regarding the atmospheric abundance of CFC-113, in addition to the usual retrievals of CFC-11, CFC-12 and HCFC-22. Also, relying on existing emission scenarios, it is foreseen that future solar occultation experiments, such as the Atmospheric Chemistry Experiment (ACE), will be able to detect HCFC-142b and HFC-134a, from the year 2005 onward and at low tangent heights. As for the nadir-looking missions, it is found that CFC-11, CFC-12 and HCFC-22 can be retrieved from IMG spectra, provided that numerous measurements are averaged over space or time, thereby mitigating the usefulness of such measurements for determining surface sources. The improved geometrical scanning performances of the future nadir-looking Infrared Atmospheric Sounding Interferometer (IASI) and the Tropospheric Emission Spectrometer (TES), however, are shown to be more promising in this respect.
BibTeX:
@article{Coheur2003a,
  author = {Coheur, P.F. and Clerbaux, C. and Colin, R.},
  title = {Spectroscopic measurements of halocarbons and hydrohalocarbons by satellite-borne remote sensors},
  journal = {Journal of Geophysical Research D: Atmospheres},
  year = {2003},
  volume = {108},
  pages = {1-1}
}
Abstract: The geometry, ground-state, and optical properties of three isomers of C60Cl24, displaying Th or D2h symmetries were analyzed by means of semiempirical quantum-chemical calculations. Among these, the Th isomer was found to be the preferred thermodynamic product. The results bring some new information on the structure of halogenated fullerenes, which in turn were essential to determine the mechanism of halogen addition onto the carbon cages. Furthermore, the present analysis reinforces the usefulness of the semiempirical calculations of absorption spectra for the determination of the structural and the optical properties of fullerene derivatives.
BibTeX:
@article{Coheur2003b,
  author = {Coheur, P.F. and Liévin, J. and Colin, R. and Razbirin, B.},
  title = {Electronic and photophysical properties of C60Cl24},
  journal = {Journal of Chemical Physics},
  year = {2003},
  volume = {118},
  pages = {550-556},
  doi = {10.1063/1.1525807}
}
Abstract: The absorption of solar light by atmospheric water vapor in the visible spectral region is analyzed by means of ground-based absorption Fourier transform spectroscopy, performed at high resolution in Brussels during summer 2001. Several microwindows between 14,000 and 18,000 cm-1, in which water vapor lines are well isolated from solar lines and other atmospheric trace gases absorptions, are examined. They are demonstrated to be adequate for the retrieval of the total water vapor column. Based on the retrievals, a detailed analysis of the water vapor line parameters published in the HITRAN database and recently reinvestigated by different groups is performed. The analysis focuses on the one hand on the comparison of the retrieved water vapor columns with in situ measurements, performed at the same time as the spectroscopic measurements and at the same location, and on the other hand on the quality of the spectral fits. It is shown that the discrepancies between the line lists affect significantly the results. In particular it is shown that the weaker lines, not measured in earlier laboratory experiments, do contribute at large zenith angles and need to be taken into account in order to better simulate the atmospheric spectra. The importance of the pressure broadening parameters is also highlighted. © 2003 Elsevier Ltd. All rights reserved.
BibTeX:
@article{Coheur2003,
  author = {Coheur, P.-F. and Clerbaux, C. and Carleer, M. and Fally, S. and Hurtmans, D. and Colin, R. and Hermans, C. and Vandaele, A.C. and Barret, B. and De Mazière, M. and De Backer, H.},
  title = {Retrieval of atmospheric water vapor columns from FT visible solar absorption spectra and evaluation of spectroscopic databases},
  journal = {Journal of Quantitative Spectroscopy and Radiative Transfer},
  year = {2003},
  volume = {82},
  pages = {133-150}
}
Abstract: We present a line profile study for two lines in the 2v3 band of CH4 recorded with a frequency stabilized tunable diode laser spectrometer. The broadening and narrowing (Dicke effect) parameters of the R(0) line perturbed by N2, O2, and He are derived from a simultaneous fitting of spectra at pressures from 20 to 300 Torr by using the soft and hard collision models. These parameters are determined for the A and F components of the unresolved R(3) manifold perturbed by N2, Ar, and He from the line profile analysis of spectra at pressures between 50 and 500 Torr. The line mixing effect between the two F components is also taken into account and the absorber speed dependent effect on broadening is estimated for N2 and Ar.
BibTeX:
@article{Dufour2003,
  author = {Dufour, G. and Hurtmans, D. and Henry, A. and Valentin, A. and Lepère, M.},
  title = {Line profile study from diode laser spectroscopy in the 12CH4 2v3 band perturbed by N2, O2, Ar, and He},
  journal = {Journal of Molecular Spectroscopy},
  year = {2003},
  volume = {221},
  pages = {80-92},
  doi = {10.1016/S0022-2852(03)00178-4}
}
Abstract: Considering the unique role that water in its vapor phase plays in atmospheric physical and chemical processes, there is a need for accurate spectroscopic parameters for this molecule. Long-pathlength Fourier transform spectra of water vapor with synthetic air as the perturbing gas were recorded and analyzed in the 26,000-13,000 cm-1 spectral region. New measurements of air-broadening and air-shifting parameters, with associated uncertainties are presented for about 5000 lines. These data complement our existing database, providing a homogeneous and extensive dataset extending from 26,000 to 9250 cm-1. Comparisons with the two most frequently used HITRAN and ESA databases as well as with other literature data available are made. Agreements and discrepancies are underlined and briefly discussed. © 2003 Elsevier Ltd. All rights reserved.
BibTeX:
@article{Fally2003,
  author = {Fally, S. and Coheur, P.-F. and Carleer, M. and Clerbaux, C. and Colin, R. and Jenouvrier, A. and Mérienne, M.-F. and Hermans, C. and Vandaele, A.C.},
  title = {Water vapor line broadening and shifting by air in the 26,000-13,000 cm-1 region},
  journal = {Journal of Quantitative Spectroscopy and Radiative Transfer},
  year = {2003},
  volume = {82},
  pages = {119-131}
}
Abstract: A newly home-built Ti:sapphire laser resonator was used to record portions of the FT-ICLAS overtone absorption spectrum of 12C2HD between 12 800 and 14 200 cm-1. The experimental set-up is presented and the recording procedure is detailed. The spectral data are illustrated with the help of five selected bands, four of them previously not reported and none previously rotationally analysed in the literature. These bands, with ṽ0 = 13 360.003(3), 13 246.266(9), 13 234.135(7), 12 938.982(5) and 13 215.45 cm-1, are assigned to 3v1 + 2v2, 2v1 + 2v2 + v4 + 4v5, 4v1 + v4, 3v2 + 3v3 and, tentatively, 4v1 + 2v4 - v4, respectively. The results of the rotational analysis of the first four mentioned bands is presented.
BibTeX:
@article{Kassi2003,
  author = {Kassi, S. and Depiesse, C. and Herman, M. and Hurtmans, D.},
  title = {Fourier transform-intracavity laser absorption spectroscopy: Sampling the overtone spectrum of 12C2HD},
  journal = {Molecular Physics},
  year = {2003},
  volume = {101},
  pages = {1155-1163},
  doi = {10.1080/0026897031000114765}
}
Abstract: We present measurements of Ar-broadening parameters for the R(0) and R(7) lines in the fundamental band of 13CO at eight temperatures from 80 to 297 K. The broadening parameters are determined by simultaneous least-squares fitting of spectra recorded using a frequency stabilized diode laser spectrometer. The comparison of the broadening parameter values for R(7) derived at room temperature and different pressures from different line profiles shows that an empirical line profile, which takes into account narrowing effects (Dicke narrowing and absorber speed dependence) but neglects any correlation between collisions, is able to describe the observed lines with constant values of the narrowing and broadening parameters over a 10-500 Torr pressure range. Starting from a recent ab initio potential energy surface, theoretical thermally averaged close coupling values of the Ar broadening parameter are calculated for the same temperatures. The comparison between experimental and calculated values shows an overall agreement of 1.5%. © 2003 Elsevier Inc. All rights reserved.
BibTeX:
@article{Mantz2003,
  author = {Mantz, A.W. and Thibault, F. and Cacheiro, J.L. and Fernandez, B. and Pedersen, T.B. and Koch, H. and Valentin, A. and Claveau, C. and Henry, A. and Hurtmans, D.},
  title = {Argon broadening of the 13CO R(0) and R(7) transitions in the fundamental band at temperatures between 80 and 297 K: Comparison between experiment and theory},
  journal = {Journal of Molecular Spectroscopy},
  year = {2003},
  volume = {222},
  pages = {131-141},
  doi = {10.1016/S0022-2852(03)00200-5}
}
Abstract: Line parameters of water vapor have been obtained in the 13 000-9250 cm-1 spectral region. The measurements were performed with a high resolution Fourier transform spectrometer coupled to long-path multiple reflection cells. Emphasis was put on the determination of accurate parameters for the weak lines, most of which have not been previously reported in the literature. A total of 7061 lines have been studied. Their positions and intensities have been determined, and for many of analyzed lines, self- and air-broadening coefficients, as well as pressure-induced shifts were obtained. A preliminary analysis of the dependence of the broadenings and shifts, with vibrational and rotational quantum numbers is given. The discussion is focused on the comparison between our measured parameters and those listed in the HITRAN database. A very good agreement is reported for the positions and intensities. It is suggested that the construction of a comprehensive and complete dataset for water vapor in this spectral region requires the merging of independent measurements, and of calculated values of broadenings and shifts for weak and blended lines. © 2003 Elsevier Ltd. All rights reserved.
BibTeX:
@article{Merienne2003,
  author = {Mérienne, M.-F. and Jenouvrier, A. and Hermans, C. and Vandaele, A.C. and Carleer, M. and Clerbaux, C. and Coheur, P.-F. and Colin, R. and Fally, S. and Bach, M.},
  title = {Water vapor line parameters in the 13 000 9250 cm-1 region},
  journal = {Journal of Quantitative Spectroscopy and Radiative Transfer},
  year = {2003},
  volume = {82},
  pages = {99-117}
}
Abstract: This paper describes the status circa 2001, of the HITRAN compilation that comprises the public edition available through 2001. The HITRAN compilation consists of several components useful for radiative transfer calculation codes: high-resolution spectroscopic parameters of molecules in the gas phase, absorption cross-sections for molecules with very dense spectral features, aerosol refractive indices, ultraviolet line-by-line parameters and absorption cross-sections, and associated database management software. The line-by-line portion of the database contains spectroscopic parameters for 38 molecules and their isotopologues and isotopomers suitable for calculating atmospheric transmission and radiance properties. Many more molecular species are presented in the infrared cross-section data than in the previous edition, especially the chlorofluorocarbons and their replacement gases. There is now sufficient representation so that quasi-quantitative simulations can be obtained with the standard radiance codes. In addition to the description and justification of new or modified data that have been incorporated since the last edition of HITRAN (1996), future modifications are indicated for cases considered to have a significant impact on remote-sensing experiments. © 2003 Elsevier Ltd. All rights reserved.
BibTeX:
@article{Rothman2003,
  author = {Rothman, L.S. and Barbe, A. and Benner, D.C. and Brown, L.R. and Camy-Peyret, C. and Carleer, M.R. and Chance, K. and Clerbaux, C. and Dana, V. and Devi, V.M. and Fayt, A. and Flaud, J.-M. and Gamache, R.R. and Goldman, A. and Jacquemart, D. and Jucks, K.W. and Lafferty, W.J. and Mandin, J.-Y. and Massie, S.T. and Nemtchinov, V. and Newnham, D.A. and Perrin, A. and Rinsland, C.P. and Schroeder, J. and Smith, K.M. and Smith, M.A.H. and Tang, K. and Toth, R.A. and Vander Auwera, J. and Varanasi, P. and Yoshino, K.},
  title = {The HITRAN molecular spectroscopic database: Edition of 2000 including updates through 2001},
  journal = {Journal of Quantitative Spectroscopy and Radiative Transfer},
  year = {2003},
  volume = {82},
  pages = {5-44}
}
Abstract: To document the performance of current line-by-line radiative transfer models, a study was performed to compare the model simulations with real observations and also inter-compare the simulations themselves. Two broadband mid-IR observed spectra with high spectral resolution were analyzed. The observations were done in nadir mode, and at the same time the atmospheric state was carefully monitored. The first dataset consisted of radiance observations using the HIS interferometer during the CAMEX-I campaign off the east coast of the USA. The second dataset consisted of observations from the ARIES interferometer collected during the Ascension Island campaign over the tropical Atlantic. These two cases are very different with the Ascension Island case being much warmer and more humid than the CAMEX case. In total 13 different research groups participated with seven different line-by-line models. The results of this study indicated that in many spectral regions the models are capable of reproducing the observations to within the observed noise. In some spectral regions relatively large differences between the simulations and observations exist. Crown Copyright © 2002 Published by Elsevier Science Ltd. All rights reserved.
BibTeX:
@article{Tjemkes2003,
  author = {Tjemkes, S.A. and Patterson, T. and Rizzi, R. and Shephard, M.W. and Clough, S.A. and Matricardi, M. and Haigh, J.D. and Höpfner, M. and Payan, S. and Trotsenko, A. and Scott, N. and Rayer, P. and Taylor, J.P. and Clerbaux, C. and Strow, L.L. and DeSouza-Machado, S. and Tobin, D. and Knuteson, R.},
  title = {The ISSWG line-by-line inter-comparison experiment},
  journal = {Journal of Quantitative Spectroscopy and Radiative Transfer},
  year = {2003},
  volume = {77},
  pages = {433-453},
  doi = {10.1016/S0022-4073(02)00174-7}
}
Abstract: Collision effects on water vapor line profiles perturbed by nitrogen at room temperature have been studied by Fourier transform and tunable diode laser spectroscopy. Narrowing effect due to molecular confinement (Dicke effect) has been observed for P and Q branch lines of the v2 band of H2O with Fourier transform spectrometer. Narrowing and broadening parameters have been determined using the soft and hard collision models. A more precise study on three R-branch lines with a frequency stabilized diode laser spectrometer allows to perform the comparison between the two collision models at low pressure and to analyze the different narrowing effects when the pressure increases taking into account the molecular confinement and the absorber speed dependent effects. © 2002 Elsevier Science (USA).
BibTeX:
@article{Claveau2002,
  author = {Claveau, C. and Henry, A. and Lepère, M. and Valentin, A. and Hurtmans, D.},
  title = {Narrowing and broadening parameters for H2O lines in the v2 band perturbed by nitrogen from fourier transform and tunable diode laser spectroscopy},
  journal = {Journal of Molecular Spectroscopy},
  year = {2002},
  volume = {212},
  article number = {98539},
  pages = {171-185},
  doi = {10.1006/jmsp.2002.8539}
}
Abstract: In order to study absorption line profiles using the stabilized diode laser spectrometer of Laboratoire de Physique Moléculaire et Applications (LPMA), a reliable determination of the emission line shape of different diodes laser is needed. In the near infrared region (1.39 and 1.66 μm) we used Distributed Feed Back diode lasers which operate around room temperature and in the middle infrared (5 and 8 μm) we used lead salt diode lasers cooled in a helium closed cycle cryostat or in a liquid nitrogen dewar. Some results obtained in H2O line profile studies in the 1.39 and 5 μm regions are presented as examples demonstrating how absorption line profile measurements can lead to erroneous values of the spectroscopic parameters when the contribution of the diode laser emission line width is neglected. © 2002 Elsevier Science B.V. All rights reserved.
BibTeX:
@article{Claveau2002a,
  author = {Claveau, C. and Lepère, M. and Dufour, G. and Valentin, A. and Henry, A. and Camy-Peyret, C. and Hurtmans, D.},
  title = {Diode laser emission linewidth determination: Application to H2O line profile studies in the 5 and 1.4 μm regions},
  journal = {Spectrochimica Acta - Part A Molecular and Biomolecular Spectroscopy},
  year = {2002},
  volume = {58},
  article number = {3454},
  pages = {2313-2321},
  doi = {10.1016/S1386-1425(02)00046-X}
}
Abstract: Four inversion schemes based on various retrieval approaches (digital gas correlation, nonlinear least squares, global fit adjustment, and neural networks) developed to retrieve CO from nadir radiances measured by such downward-looking satelliteborne instruments as the Measurement of Pollution in the Troposphere (MOPITT), the Tropospheric Emission Spectrometer (TES), and the Infrared Atmospheric Sounding Interferometer (IASI) instruments were compared both for simulated cases and for atmospheric spectra recorded by the Interferometric Monitor for Greenhouse Gases (IMG). The sensitivity of the retrieved CO total column amount to properties that may affect the inversion accuracy (noise, ancillary temperature profile, and water-vapor content) was investigated. The CO column amounts for the simulated radiance spectra agreed within 4%, whereas larger discrepancies were obtained when atmospheric spectra recorded by the IMG instrument were analyzed. The assumed vertical temperature profile is shown to be a critical parameter for accurate CO retrieval. The instrument’s line shape was also identified as a possible cause of disagreement among the results provided by the groups of scientists who are participating in this study. © 2002 Optical Society of America.
BibTeX:
@article{Clerbaux2002,
  author = {Clerbaux, C. and Hadji-Lazaro, J. and Payan, S. and Camy-Peyret, C. and Wang, J. and Edwards, D.P. and Luo, M.},
  title = {Retrieval of CO from nadir remote-sensing measurements in the infrared by use of four different inversion algorithms},
  journal = {Applied Optics},
  year = {2002},
  volume = {41},
  pages = {7068-7078},
  doi = {10.1364/AO.41.007068}
}
Abstract: The radiative properties of water vapor play an important role in the physical and chemical processes occurring in the atmosphere. Accurate knowledge of the line parameters for this species is therefore needed. This work presents new measurements of water vapor line parameters in the 26000-13000 cm-1 spectral region. The measurements were obtained by combining a high-resolution Fourier transform spectrometer with a long-path absorption cell, thus allowing the observation of very weak, previously unobserved, lines. A total of more than 9000 lines have been identified and their position, integrated cross section and self-broadening parameter have been determined. The dependence of the line parameters on nitrogen buffer gas pressure (0-800 hPa) has also been studied. The complete line list presented here is primarily compared to the HITRAN spectroscopic database, most frequently used in atmospheric calculations. © 2002 Elsevier Science Ltd. All rights reserved.
BibTeX:
@article{Coheur2002,
  author = {Coheur, P.-F. and Fally, S. and Carleer, M. and Clerbaux, C. and Colin, R. and Jenouvrier, A. and Mérienne, M.-F. and Hermans, C. and Vandaele, A.C.},
  title = {New water vapor line parameters in the 26000-13000 cm-1 region},
  journal = {Journal of Quantitative Spectroscopy and Radiative Transfer},
  year = {2002},
  volume = {74},
  pages = {493-510},
  doi = {10.1016/S0022-4073(01)00269-2}
}
BibTeX:
@article{Colin2002,
  author = {Colin, R. and Coheur, P.-F. and Kiseleva, M. and Vandaele, A.C. and Bernath, P.F.},
  title = {Spectroscopic constants and term values for the X2πi state of OH (v = 0-10)},
  journal = {Journal of Molecular Spectroscopy},
  year = {2002},
  volume = {214},
  pages = {225-226},
  doi = {10.1006/jmsp.2002.8591}
}
Abstract: Vibrational assignments of fundamental, combination and overtone bands in the main isotopomer of gaseous transformic acid are reported from spectra either newly or previously [J. Chem. Phys. 113 (2000) 1535] recorded using high-resolution Fourier transform and intracavity laser absorption spectroscopies. A total of 62 bands, with 32 newly reported ones, are observed from the lowest energy band, v7 at 626.16 cm-1 up to 4v1 at 13284.1 cm-1. Among these bands, 43 are firmly assigned, and 16 tentatively. Effective vibrational constants are obtained. The normal modes of vibrations are further characterised using ab initio calculations providing fundamental band intensities and picturing normal mode nuclear displacements. The effective investigation of the rotational structure in the first CH stretch overtone band (2v2) and in the second OH stretch overtone band (3v1) is detailed. Rotational information is also presented for 3v2 and two close-lying bands, that could be extracted from the strong overlapping formic acid dimer bands using artificial filtering procedures. © 2002 Elsevier Science B.V. All rights reserved.
BibTeX:
@article{Freytes2002,
  author = {Freytes, M. and Hurtmans, D. and Kassi, S. and Liévin, J. and Vander Auwera, J. and Campargue, A. and Herman, M.},
  title = {Overtone spectroscopy of formic acid},
  journal = {Chemical Physics},
  year = {2002},
  volume = {283},
  pages = {47-61},
  doi = {10.1016/S0301-0104(02)00507-4}
}
Abstract: To prepare the mission of the Infrared Atmospheric Sounding Interferometer (IASI), which will be launched in 2005 aboard the European METOP satellite, the measurement capability to retrieve trace gases concentrations from nadir radiances was investigated. This included sensitivity studies, development of an innovating inversion algorithm, cloud-filtering, and use of data assimilation techniques for validation purposes. The availability of nadir radiances measured by the IMG instrument allowed us to test the tools under development on real data. This paper summarizes the current status of the work.
BibTeX:
@article{Hadji-Lazaro2002,
  author = {Hadji-Lazaro, J. and Clerbaux, C. and Turquety, S. and Hauglustaine, D. and Khattatov, B.},
  title = {Trace gases concentrations retrieval from measurements provided by a nadir-looking Fourier transform spectrometer},
  journal = {Proceedings of SPIE - The International Society for Optical Engineering},
  year = {2002},
  volume = {4485},
  pages = {1-8},
  doi = {10.1117/12.454245}
}
Abstract: The R(0) line profile of the 13CO fundamental band is studied at low concentration in helium from room temperature (296.7 K) to 40 K. A narrowing effect due to molecular confinement (Dicke effect) is observed and analyzed using the Galatry soft collision model. The narrowing parameter is found to be in good agreement with the dynamic friction coefficient deduced from the diffusion coefficient over the entire temperature range. © 2002 Elsevier Science (USA).
BibTeX:
@article{Henry2002,
  author = {Henry, A. and Claveau, C. and Valentin, A. and Hurtmans, D. and Mantz, A.W.},
  title = {Confinement narrowing of the R(0) line in the 13CO fundamental band broadened by helium from room temperature down to 40 K},
  journal = {Journal of Molecular Spectroscopy},
  year = {2002},
  volume = {214},
  article number = {98576},
  pages = {28-34},
  doi = {10.1006/jmsp.2002.8576}
}
Abstract: We have determined the spectroscopic parameters that are necessary to describe accurately the R(0) line profile of the CH4 2ν3 band from about 1 Torr to a few hundred Torr of pure CH4. The intensities determined at each pressure are in overall agreement to better than 0.7%. The R(3) manifold of the same band has also been investigated. Relative positions and absolute intensities of the three transitions composing the triplet have been determined. The intensity distribution inside the triplet is in fair agreement with recent theoretical predictions. © 2002 Elsevier Science (USA).
BibTeX:
@article{Hurtmans2002a,
  author = {Hurtmans, D. and Dufour, G. and Bell, W. and Henry, A. and Valentin, A. and Camy-Peyret, C.},
  title = {Line intensity of R(0) and R(3) of the 12CH4 2ν3 band from diode laser spectroscopy},
  journal = {Journal of Molecular Spectroscopy},
  year = {2002},
  volume = {215},
  pages = {128-133},
  doi = {10.1006/jmsp.2002.8620}
}
Abstract: The vibrational state perturbing the J = 17 and 18 rotational states of the zero-order v1 + 3v3 state of 12C2H2 is assigned to the state with vibrational energy predicted at Gv = 12 685.1 cm-1 using the cluster model (EL IDRISSI, M.I., LIÉVIN, J., CAMPARGUE, A. and HERMAN, M., 1999, J. chem. Phys., 110, 2074). The assignment is discussed also in terms of the very special pressure shift behaviour demonstrated previously for absorption lines reaching these levels (HERREGODTS, F., HEPP, M., HURTMANS, D., VANDER AUWERA, J. and HERMAN, M., 1999, J. chem. Phys., 111, 7961). The experimental information arising from a set-up newly running at ULB, called FT-ICLAS brings decisive information in the assignment process. This set-up is described briefly.
BibTeX:
@article{Hurtmans2002,
  author = {Hurtmans, D. and Kassi, S. and Depiesse, C. and Herman, M.},
  title = {Assignment of a perturbation in the FT-ICLAS spectrum of 12C2H2 around 12 709.5 cm-1},
  journal = {Molecular Physics},
  year = {2002},
  volume = {100},
  pages = {3507-3511},
  doi = {10.1080/00268970210138904}
}
Abstract: Optical spectra of the C60Cl24 halofullerene in the crystalline state, as well as of C60Cl24 matrixisolated molecules, were studied. In both cases, a rich line structure was revealed in absorption spectra in the energy region 1.5-3.0 eV. An energy diagram of the electronic levels of the molecule which are responsible for the observed optical transitions is proposed. The parameters of the geometrical structure of the C60Cl24 molecule were calculated under the assumption of its having Th symmetry. These data were used in a theoretical study of the embedment of the C60Cl24 molecule in a toluene crystal matrix, which leads to the formation of a fine spectral structure (an analog of the Shpol'skii effect) observed experimentally in this study. © 2002 MAIK "Nauka/Interperiodica".
BibTeX:
@article{Razbirin2002,
  author = {Razbirin, B.S. and Starukhin, A.N. and Chugreev, A.V. and Zgoda, A.S. and Smirnov, V.P. and Grushko, Yu.S. and Kolesnik, S.G. and Coheur, P.-F. and Liévin, J. and Colin, R.},
  title = {Absorption line spectrum of the C60Cl24 halofullerene},
  journal = {Physics of the Solid State},
  year = {2002},
  volume = {44},
  pages = {2204-2209},
  doi = {10.1134/1.1521480}
}
Abstract: The Interferometric Monitor for Greenhouse Gases (IMG) on board the Japanese ADEOS platform provided the first high resolution atmospheric spectra allowing the simultaneous measurement of several IR absorbing species, including ozone. The paper describes the retrieval of total column ozone fields from nadir radiances, using an inversion algorithm developed for the Infrared Atmospheric Sounding Interferometer (IASI). The accuracy and sensitivity of the retrieved concentrations are assessed. The global distributions obtained from the available IMG/ADEOS Level IC data are shown to be in good agreement with the TOMS/ADEOS (Total Ozone Mapping Spectrometer) Level 2 measurements.
BibTeX:
@article{Turquety2002,
  author = {Turquety, S. and Hadji-Lazaro, J. and Clerbaux, C.},
  title = {First satellite ozone distributions retrieved from nadir high-resolution infrared spectra},
  journal = {Geophysical Research Letters},
  year = {2002},
  volume = {29},
  pages = {51-1}
}
Abstract: The Infrared Atmospheric Sounding Interferometer (IASI), which is due for launch in 2005 aboard the European METOP satellite, will record the infrared radiation of the Earth/atmosphere system in a nadir-viewing geometry. The sensitivity studies carried out on simulated IASI spectra allowed us to highlight its capability to retrieve both total and tropospheric column amounts of ozone. Two algorithms based on neural network techniques have been developed to retrieve these quantities. The averaging kernels characterizing the results show that the information corresponding to the different atmospheric layers can be isolated. However, for the tropospheric ozone retrieval, the lower stratosphere is not totally decoupled, which induces larger uncertainties for the tropospheric columns than for the total columns. Nevertheless, very satisfactory performance has been achieved for both algorithms, with inversion errors smaller than 5 % for the total column retrieval and smaller than 20 % for the tropospheric column retrieval. The Interferometer Monitor for Greenhouse Gases (IMG), which flew aboard the Japanese ADEOS platform was based on the same observation technique as IASI, which enabled us to test our algorithms on real data. Both algorithms have been applied to these data for June 1997. The distributions obtained are in good agreement with the Total Ozone Mapping Spectrometer (TOMS) measurements.
BibTeX:
@conference{Turquety2002a,
  author = {Turquety, S. and Hadji-Lazaro, J. and Clerbaux, C.},
  title = {Retrieval of ozone from infrared IASI measurements},
  journal = {Proceedings of SPIE - The International Society for Optical Engineering},
  year = {2002},
  volume = {4539},
  pages = {106-115},
  doi = {10.1117/12.454426}
}
Abstract: Collision effects on water vapor at low concentration in mixture with noble gases and nitrogen have been studied by Fourier transform spectroscopy in a pressure range where line narrowing by dynamic confinement (Dicke effect) and collision broadening are observable, i.e. when the Voigt function cannot reproduce the observed profiles. Precise values of the broadening parameter have been obtained for R branch lines of the ν2 band of H2O and narrowing parameter values were derived using the soft and hard collision models. Furthermore, it is shown that, when neglecting the confinement effect, systematic errors on the broadening parameters may be introduced and reach several percents for the narrowest lines corresponding to the highest J values. © 2000 Elsevier Science Ltd. All rights reserved.
BibTeX:
@article{Claveau2001,
  author = {Claveau, C. and Henry, A. and Hurtmans, D. and Valentin, A.},
  title = {Narrowing and broadening parameters of H2O lines perturbed by He, Ne, Ar, Kr and nitrogen in the spectral range 1850-2140 cm-1},
  journal = {Journal of Quantitative Spectroscopy and Radiative Transfer},
  year = {2001},
  volume = {68},
  pages = {273-298}
}
Abstract: Carbon monoxide measurements are obtained from the analysis of the spectra provided by the Interferometric Monitor for Greenhouse Gases (IMG) instrument, which flew on board the Japanese ADEOS satellite. The averaging kernel function of the instrument, which provides the sensitivity of retrieved CO to the vertical atmospheric layers, is calculated. A sequential assimilation approach is used to incorporate this CO data set, along with a detailed associated error budget, into a global three-dimensional chemistry-transport model (MOZART version 2). We show how data assimilation allows one to highlight the differences between modeled and observed CO global distribution. Surface CO mixing ratios computed after assimilation of total columns provided by the IMG instrument are compared with the National Oceanic and Atmospheric Administration (NOAA) - Climate Monitoring and Diagnostics Laboratory (CMDL) in situ measurements, and a good agreement is found between the two data sets. Copyright 2001 by the American Geophysical Union.
BibTeX:
@article{Clerbaux2001,
  author = {Clerbaux, C. and Hadji-Lazaro, J. and Hauglustaine, D. and Mégie, G. and Khattatov, B. and Lamarque, J.-F.},
  title = {Assimilation of carbon monoxide measured from satellite in a three-dimensional chemistry-transport model},
  journal = {Journal of Geophysical Research Atmospheres},
  year = {2001},
  volume = {106},
  article number = {2000JD900682},
  pages = {15385-15394}
}
Abstract: This work reports on the analysis of the near-UV and visible absorption spectrum of water vapor, obtained by combining a high-resolution FT spectrometer and a long path White multiple-reflection cell (total path length of 602 m). A large number of water vapor lines belonging to highly excited vibrational levels (polyads up to 8 v) are identified. Most of these lines have not been observed previously and do not appear in the spectroscopic databases HITRAN and GEISA, widely used for atmospheric calculations. All identified lines are fitted with a Voigt profile using the WSPECTRA program and their cross section and self-broadening parameters at 291 K are determined. A particular attention is given to the integrated cross section over the total spectral range investigated (25000-20000 cm-1), in order to estimate the contribution of the weak UV-visible water vapor absorption lines to the earth's radiation balance. Preliminary measurements of cross section in the 20000-16000 cm-1 spectral range are also presented.
BibTeX:
@conference{Coheur2001,
  author = {Coheur, P.-F. and Fally, S. and Vandaele, A.C. and Hermans, C. and Jenouvrier, A. and Carleer, M. and Mérienne, M.-F. and Clerbaux, C. and Colin, R.},
  title = {Absolute intensities of water vapor lines in the near ultraviolet and visible regions},
  journal = {Proceedings of SPIE - The International Society for Optical Engineering},
  year = {2001},
  volume = {4168},
  pages = {97-105},
  doi = {10.1117/12.413853}
}
Abstract: Infrared atmospheric measurements provided by space nadir looking remote sensors are affected by the presence of clouds. To obtain cloud-free CO global distributions from the radiance spectra measured by the IMG instrument, we have developed a simple method of spectra selection using skin temperatures provided by the ECMWF model. Information on the cloud cover was provided by the cloud data of the POLDER instrument which flew aboard the same platform as IMG. We show that a filter based on skin temperature, with thresholds of 8 K over sea and 15.3 K over land, allows to remove most of the cloudy cases.
BibTeX:
@article{Hadji-Lazaro2001,
  author = {Hadji-Lazaro, J. and Clerbaux, C. and Couvert, P. and Chazette, P. and Boonne, C.},
  title = {Cloud filter for CO retrieval from IMG infrared spectra using ECMWF temperatures and POLDER cloud data},
  journal = {Geophysical Research Letters},
  year = {2001},
  volume = {28},
  pages = {2397-2400},
  doi = {10.1029/2000GL012342}
}
Abstract: A Fourier transform interferometer was used to record the slit-jet cooled absorption spectrum of 12C2H4 between 700 and 2400 cm-1, at a spectral resolution of 0.005cm-1. Three bands, v12 at 1442.44270(1) cm-1, v7 + v8 at 1888.978 23(3)cm-1 and v6 + v10 at 2047.775832(2) cm-1, were rotationally analysed. In the case of 7181, a known Coriolis perturbation mechanism involving the nearby 4181 (1958.264 cm-1) and 81101 (1766.391 cm-1) states was accounted for in the analysis. The latter fitting procedure included 12 levels from the 4181 state which are observed because lines from v4 + v8 borrow intensity from v7 + v8. Compared to the literature, significantly improved vibration-rotation constants were obtained for all upper states reported in the present study.
BibTeX:
@article{Hurtmans2001,
  author = {Hurtmans, D. and Rizopoulos, A. and Herman, M. and Hassan, L.M.S. and Perrin, A.},
  title = {Vibration-rotation analysis of the jet-cooled v12, v7 + v8 and v6 + v10 absorption bands of 12C2H4},
  journal = {Molecular Physics},
  year = {2001},
  volume = {99},
  pages = {455-461},
  doi = {10.1080/00268970010017018}
}
Abstract: The photophysical properties of hexa-functionalized C60 derivatives (C60Cl6, C60Ph5Cl, C60Ph5H, and two C60Ph5OH isomers) have been investigated by means of UV-visible absorption and fluorescence spectroscopy in cyclohexane solution and quantum-chemical calculations derived from semiempirical Hartree-Fock approaches. A very good agreement is obtained between the measured absorption and fluorescence spectra and the calculated excitation energies, thus allowing for a detailed assignment of the optical features. The effects of symmetry and chemical nature of the functional groups on the ground-state and spectroscopic properties of the C60 derivatives are discussed. © 2000 American Institute of Physics.
BibTeX:
@article{Coheur2000,
  author = {Coheur, P.-F. and Cornil, J. and Dos Santos, D.A. and Birkett, P.R. and Liévin, J. and Brédas, J.L. and Walton, D.R.M. and Taylor, R. and Kroto, H.W. and Colin, R.},
  title = {Photophysical properties of hexa-functionalized C60 derivatives: Spectroscopic and quantum-chemical investigations},
  journal = {Journal of Chemical Physics},
  year = {2000},
  volume = {112},
  pages = {8555-8566}
}
Abstract: The photophysics of six multiply phenylated C70 derivatives [C70Ph2, C70Ph4, C70Ph6 (two regioisomers), C70Ph8 and C70Ph10] have been investigated by means of steady state spectroscopy in cyclohexane solution and quantum-chemical calculations derived from semiempirical Hartree-Fock approaches. There is good agreement between the measured absorption spectra and the INDO/SCI calculated excitation energies for each derivative. The foregoing results and some additional ground state properties calculated at the AMI level have been used to predict that the perturbation of the π electronic system of the cage results in significant changes in the photophysics of the fullerene derivatives. The effects of conjugation and spatial localization of the HOMO and LUMO orbitals on the energy of the first electronic transition are discussed in greater detail. © 2000 American Institute of Physics.
BibTeX:
@article{Coheur2000a,
  author = {Coheur, P.-F. and Cornil, J. and Dos Santos, D.A. and Birkett, P.R. and Liévin, J. and Brédas, J.L. and Walton, D.R.M. and Taylor, R. and Kroto, H.W. and Colin, R.},
  title = {Photophysical properties of multiply phenylated C70 derivatives: Spectroscopic and quantum-chemical investigations},
  journal = {Journal of Chemical Physics},
  year = {2000},
  volume = {112},
  pages = {6371-6381}
}
Abstract: The spectroscopic literature reporting on the coupling between Fourier transform spectrometers and supersonic jet expansions is reviewed. Particular attention is devoted to high resolution infrared absorption experiments. Short and much longer introductions are provided on Fourier transform spectrometers and jets, respectively, with emphasis on the problems raised by coupling the two techniques. Details of the optical designs reported in the literature are considered. The literature on all the molecules studied is tabulated. Some of the spectroscopic results are highlighted, in particular those obtained at Universite Libre de Bruxelles.
BibTeX:
@article{Herman2000,
  author = {Herman, M. and Georges, R. and Hepp, M. and Hurtmans, D.},
  title = {High resolution Fourier transform spectroscopy of jet-cooled molecules},
  journal = {International Reviews in Physical Chemistry},
  year = {2000},
  volume = {19},
  pages = {277-325},
  doi = {10.1080/01442350050020905}
}
Abstract: We have used a Ti:sapphire autoscan laser spectrometer to measure Ar-induced pressure-broadening, narrowing and shift effects for 24 individual vibration-rotation lines in the ν1+3ν3 band of 12C2H2. The acetylene and total pressures ranged between 10 and 20 Torr, and between 30 and 310 Torr, respectively. The Voigt profile accounted for the higher pressure measurements while the soft and hard collision profiles were required to fit the lower pressure measurements. Lineshift parameters that are significantly different from the overall behaviour in the band were observed for the R(17) and P(19) lines and are qualitatively attributed to the influence of an intramolecular Coriolis-type coupling on the interparticle interaction potential. Those results confirm all trends of self-collisional measurements recently reported for this band.
BibTeX:
@article{Herregodts2000,
  author = {Herregodts, F. and Hurtmans, D. and Auwera, J.V. and Herman, M.},
  title = {Ar-induced pressure effects in the ν1+3ν3 absorption band in 12C2 H2},
  journal = {Chemical Physics Letters},
  year = {2000},
  volume = {316},
  pages = {460-464}
}
Abstract: In this study, three different inputs dedicated to the OH bond excitation in trans-formic acid were merged. First, experiments were carried out using FTS. Following this, ICLAS was used to record the 4vOH band at high spectral region. Finally, ab initio calculations were performed. Overall, the results indicate the occurrence of a chemical mechanism different from those usually probed with overtone spectroscopy.
BibTeX:
@article{Hurtmans2000,
  author = {Hurtmans, D. and Herregodts, F. and Herman, M. and Liévin, J. and Campargue, A. and Garnache, A. and Kachanov, A.A.},
  title = {Spectroscopic and ab initio investigation of the vOH overtone excitation in trans-formic acid},
  journal = {Journal of Chemical Physics},
  year = {2000},
  volume = {113},
  pages = {1535-1545},
  doi = {10.1063/1.481939}
}
Abstract: We have measured absolute line intensities in the ν2 fundamental band at 1238 cm-1 of both isotopomers of hypochlorous acid, HOCl. To obtain the partial pressure of the species in the sample mixture, unavailable through direct measurement since HOCl exists only in equilibrium with H2O and Cl2O and may decay by secondary reactions, we relied on known absolute line intensities in the pure rotational far-infrared (FIR) spectrum determined from Stark effect measurements. We have thus recorded simultaneously the FIR pure rotation spectrum of HOCl using a Bruker IFS120HR interferometer and the spectrum of a few vibration-rotation lines in the infrared (IR) ν2 band using a tunable diode laser spectrometer. The absolute intensities of these IR lines thus determined allowed us to `calibrate' the intensities of vibration-rotation lines in the whole ν2 band, measured previously using Fourier transform spectroscopy. The treatment of the data took into account the blackbody emission contribution in the FIR and the evolution of the HOCl amount during the recording of the spectra. The latter was found to be almost constant over hours after conditioning of the cell. The square of the ν2 band vibrational transition dipole moment was determined to be 0.013947(23) D2 and 0.013870(51) D2 for HO35Cl and HO37Cl, respectively, that is, 29 to 73% lower than previous measurements. A linear Herman-Wallis factor was also determined for both isotopomers. Finally, the line intensities were least-squares fitted using a model that takes into account a weak resonance between the (010) and (002) levels.
BibTeX:
@article{VanderAuwera2000,
  author = {Vander Auwera, J. and Kleffmann, J. and Flaud, J.-M. and Pawelke, G. and Bürger, H. and Hurtmans, D. and Pétrisse, R.},
  title = {Absolute ν2 line intensities of HOCl by simultaneous measurements in the infrared with a tunable diode laser and far-infrared region using a Fourier transform spectrometer},
  journal = {Journal of molecular spectroscopy},
  year = {2000},
  volume = {204},
  pages = {36-47},
  doi = {10.1006/jmsp.2000.8197}
}
Abstract: Infrared spectra of a carbon dioxide sample enriched with oxygen-17 have been recorded with a resolution of about 0.0025 cm-1 in the region of the laser bands near 10 and 9 μm, using the long path difference Fourier Transform Spectrometer of the LPMA in Paris. The two laser bands of the 16O12C17O and 17O12C18O species have been analyzed for the first time. Line intensities for several isotopic species have been measured in this region and the rotationless transition dipole moments and Herman-Wallis coefficients of the corresponding bands have been reported. In particular intensities, alternation in the spectra of 17O12C17O has been analyzed. © 1999 Academic Press.
BibTeX:
@article{Claveau1999,
  author = {Claveau, C. and Teffo, J.-L. and Hurtmans, D. and Valentin, A. and Gamache, R.R.},
  title = {Line positions and absolute intensities in the laser bands of carbon-12 oxygen-17 isotopic species of carbon dioxide},
  journal = {Journal of Molecular Spectroscopy},
  year = {1999},
  volume = {193},
  pages = {15-32},
  doi = {10.1006/jmsp.1998.7704}
}
Abstract: The high-resolution atmospheric spectra recorded by the Interferometric Monitor for Greenhouse gases instrument on the ADvanced Earth Observing System (IMG/ADEOS) in June, 1997, were analyzed by two different and complementary inversion algorithms to retrieve CO total columns. Spectral fits of high quality were obtained using a global fit algorithm on selected cloud-free measurements. Global distribution maps of CO obtained using a fast neural network retrieval algorithm are compared to the results provided by current chemistry-transport models. These studies highlight the need for complementary information (temperature, emissivity, instrumental function, and cloud content) to retrieve accurate CO vertical columns.
BibTeX:
@article{Clerbaux1999a,
  author = {Clerbaux, Cathy and Hadji-Lazaro, Juliette and Payan, Sebastien and Camy-Peyret, Claude and Megie, Gerard},
  title = {Retrieval of CO columns from IMG/ADEOS spectra},
  journal = {IEEE Transactions on Geoscience and Remote Sensing},
  year = {1999},
  volume = {37},
  pages = {1657-1661},
  doi = {10.1109/36.763283}
}
Abstract: The high-resolution atmospheric spectra recorded by the Interferometric Monitor for Greenhouse gases instrument on the ADvanced Earth Observing System (IMG/ADEOS) in June, 1997, were analyzed by two different and complementary inversion algorithms to retrieve CO total columns. Spectral fits of high quality were obtained using a global fit algorithm on selected cloud-free measurements. Global distribution maps of CO obtained using a fast neural network retrieval algorithm are compared to the results provided by current chemistry-transport models. These studies highlight the need for complementary information (temperature, emissivity, instrumental function, and cloud content) to retrieve accurate CO vertical columns. Index Terms - Atmospheric measurements, infrared spectroscopy, least square method, neural networks. © 1999 IEEE.
BibTeX:
@article{Clerbaux1999,
  author = {Clerbaux, C. and Hadji-Lazaro, J. and Payan, S. and Camy-Peyret, C. and Mégie, G.},
  title = {Retrieval of CO Columns from IMG/ADEOS Spectra},
  journal = {IEEE Transactions on Geoscience and Remote Sensing},
  year = {1999},
  volume = {37},
  pages = {1645-1656},
  doi = {10.1109/36.763281}
}
Abstract: The geometry and electronic structure of three C60 derivatives (C60Cl6, C60Ph5Cl and C60Ph5H) are studied by means of spectroscopic measurements in cyclohexane solution and semi-empirical Hartree-Fock quantum-chemical calculations. A good agreement between observed and simulated spectra is reported. Based on the latter, the importance of symmetry and nature of the functional groups on the properties of the C60 cages is discussed.
BibTeX:
@article{Coheur1999,
  author = {Coheur, P.-F. and Cornil, J. and Dos Santos, D.A. and Birkett, P.R. and Liévin, J. and Brédas, J.L. and Janot, J.-M. and Seta, P. and Leach, S. and Walton, D.R.M. and Taylor, R. and Kroto, H.W. and Colin, R.},
  title = {Photophysical properties of C60Cl6, C60Ph5Cl and C60Ph5H},
  journal = {Synthetic Metals},
  year = {1999},
  volume = {103},
  pages = {2407-2410},
  doi = {10.1016/S0379-6779(98)00250-1}
}
Abstract: Up to the first years of the next millennium, several observation programs of the troposphere are scheduled, including the Infrared Atmospheric Sounding Interferometer, which uses Fourier transform spectroscopy to record the radiance of the Earth-atmosphere system with a nadir-viewing geometry. The Interferometric Monitor for Greenhouse Gases (IMG), launched aboard the Advanced Earth Observing System in August 1996, was a precursor of these forthcoming missions. A new inversion algorithm based on neural network techniques is in development to retrieve trace gases from high-resolution nadir radiances. Neural networks offer a technical alternative to classical methods and allow efficient inversion calculations as required to treat the huge volume of data which will be provided by continuous observation of the atmosphere from space. To develop a network to retrieve the carbon monoxide total column, realistic simulations of the IMG measurements were obtained by coupling a three-dimensional chemical-transport model with a high-resolution line-by-line radiative transfer code adjusted to the instrumental features. The application of the algorithm on simulated data allowed the checking of its performance: for about 99% of the cases, the relative inversion error was less than 10%. This algorithm has been applied to the spectra recorded by the IMG instrument between June 16 and 19, 1997. Global-scale distributions of CO total columns were obtained for the first time by using a neural network, and this technique proved its ability to achieve real-time inversion of atmospheric CO. Copyright 1999 by the American Geophysical Union.
BibTeX:
@article{Hadji-Lazaro1999,
  author = {Hadji-Lazaro, J. and Clerbaux, C. and Thiria, S.},
  title = {An inversion algorithm using neural networks to retrieve atmospheric CO total columns from high-resolution nadir radiances},
  journal = {Journal of Geophysical Research Atmospheres},
  year = {1999},
  volume = {104},
  article number = {1999JD900431},
  pages = {23841-23854}
}
Abstract: Different tunable diode lasers (TDL), tightly controlled by a Michelson interferometer, have been used to study precisely the evolution of absorption line profiles when the pressure increases. For this purpose the spectral intensity distribution within each given TDL mode has been determined by comparing the observed spectrum of a narrow absorption line at very low pressure (Doppler line) with a calculated spectrum, convolution product of the TDL intensity distribution with the exact absorption line shape precisely described by a Gauss profile. Examples of confinement narrowing and absorber speed dependent effect are given with CO or HCl in different buffer gases (N2, He, Ne, Ar and Xe) and the line parameters have been deduced taking into account the intensity distribution of the TDL emission.
BibTeX:
@article{Henry1999,
  author = {Henry, A. and Hurtmans, D.},
  title = {Collision narrowing and speed dependent effect on broadening in vibration rotation line profiles perturbed by different buffer gases up to one atmosphere - difficulties in these analyses coming from the quality of the tunable diode laser emission},
  journal = {Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy},
  year = {1999},
  volume = {55},
  pages = {1967-1986},
  doi = {10.1016/S1386-1425(99)00069-4}
}
Abstract: We have recorded the spectrum of the v1+3v3 band in 12C2H2, around 12676 cm-1, using an autoscan Ti:Sa spectrometer. Pressure-dependent line positions were determined from an absorption spectrum recorded using a long White-type multiple-pass cell. An optoacoustic cell with a constant, low acetylene pressure allowed reference line position wavenumbers to be measured simultaneously. In different experiments, the multiple-pass cell was filled with increasing acetylene pressures. Self-collisional lineshifts were determined for more than 30 P and R lines in the band. Line wavenumbers for the stronger lines were separately measured from an optoacoustic spectrum calibrated using the results of a previous investigation in the literature [X. Zhan and L. Halonen, J. Mol. Spectrosc. 160, 464 (1993)] and corrected for their pressure dependence using the presently determined self-collisional lineshifts. Lineshift parameters that are significantly different from the overall behavior in the band are unexpectedly observed for the R(17) and P(19) lines. This result is explained in terms of a different intermolecular behavior of the molecule in the upper J=18 rotation level, attributed to an intramolecular Coriolis-type coupling with a nearby state tentatively assigned as containing important excitation in v5, the cis-bend mode. © 1999 American Institute of Physics.
BibTeX:
@article{Herregodts1999a,
  author = {Herregodts, F. and Hepp, M. and Hurtmans, D. and Vander Auwera, J. and Herman, M.},
  title = {Laser spectroscopy of the v1+3v3 absorption band in 12C2H2. II. Self-collisional lineshift measurements},
  journal = {Journal of Chemical Physics},
  year = {1999},
  volume = {111},
  pages = {7961-7965}
}
Abstract: We have developed a Ti:Sa autoscan laser spectrometer and used it to perform a detailed investigation of individual line profiles in the v1 + 3v3 band of 12C2H2. Pressure self-broadening effects were measured for most lines with J″ values ranging from 0 to 22, and for pressures between 10 and 600 Torr. The high-pressure data points (p&gt;250Torr) are fitted satisfactorily by a Voigt profile. Line narrowing, characterized by an underestimation of the Lorentz contribution to the Voigt profile, was observed for the low pressures range (p&lt;150Torr), indicating the influence of molecular confinement. The two usual limit models (soft and hard collisions) were fitted to the observed line shapes in order to extract more precise information concerning the pressure broadening. The present results confirm the absence of strong vibrational dependence in the self-broadening coefficients. Absolute line intensities are also determined in the fitting procedure. No significant differences were found for the two pressure domains if the appropriate model in each range is used. © 1999 American Institute of Physics. 00141-5].
BibTeX:
@article{Herregodts1999,
  author = {Herregodts, F. and Hurtmans, D. and Vander Auwera, J. and Herman, M.},
  title = {Laser spectroscopy of the v1+3v3 absorption band in 12C2H2. I. Pressure broadening and absolute line intensity measurements},
  journal = {Journal of Chemical Physics},
  year = {1999},
  volume = {111},
  pages = {7954-7960}
}
Abstract: The current version GEISA-97 of the computer-accessible database system GEISA (Gestion et Etude des Informations Spectroscopiques Atmosphériques: Management and Study of Atmospheric Spectroscopic Information) is described. This catalogue contains 1,346,266 entries. These are spectroscopic parameters required to describe adequately the individual spectral lines belonging to 42 molecules (96 isotopic species) and located between 0 and 22,656 cm-1. The featured molecules are of interest in studies of the terrestrial as well as the other planetary atmospheres, especially those of the Giant Planets. GEISA-97 contains also a catalog of absorption cross-sections of molecules such as chlorofluorocarbons which exhibit unresolvable spectra. The modifications and improvements made to the earlier edition (GEISA-92) and the data management software are described. GEISA-97 and the associated management software are accessible from the ARA/LMD (Laboratoire de Météorologie Dynamique du CNRS, France) web site: http://ara01.polytechnique.fr/registration. © 1999 Elsevier Science Ltd. All rights reserved.
BibTeX:
@article{Jacquinet-Husson1999,
  author = {Jacquinet-Husson, N. and Arié, E. and Ballard, J. and Barbe, A. and Bjoraker, G. and Bonnet, B. and Brown, L.R. and Camy-Peyret, C. and Champion, J.P. and Chédin, A. and Chursin, A. and Clerbaux, C. and Duxbury, G. and Flaud, J.-M. and Fourrié, N. and Fayt, A. and Graner, G. and Gamache, R. and Goldman, A. and Golovko, Vl. and Guelachvili, G. and Hartmann, J.M. and Hilico, J.C. and Hillman, J. and Lefèvre, G. and Lellouch, E. and Mikhaïlenko, S.N. and Naumenko, O.V. and Nemtchinov, V. and Newnham, D.A. and Nikitin, A. and Orphal, J. and Perrin, A. and Reuter, D.C. and Rinsland, C.P. and Rosenmann, L. and Rothman, L.S. and Scott, N.A. and Selby, J. and Sinitsa, L.N. and Sirota, J.M. and Smith, A.M. and Smith, K.M. and Tyuterev, Vl.G. and Tipping, R.H. and Urban, S. and Varanasi, P. and Weber, M.},
  title = {The 1997 spectroscopic GEISA databank},
  journal = {Journal of Quantitative Spectroscopy and Radiative Transfer},
  year = {1999},
  volume = {62},
  pages = {205-254}
}
Abstract: Direct determination of the radiative forcing of trace gases will be made possible by use of the next generation of nadir-looking spaceborne instruments that provide measurements of atmospheric radiances in the infrared spectral range with improved spectral and spatial resolution. An inversion statistical method has thus been developed and applied to the direct determination of the radiative forcing of methane, based on such instruments as the Fourier-transform Interferometric Monitor for Greenhouse Gases launched onboard the Japanese Advanced Earth Observing Satellite in 1996 and the Infrared Atmospheric Sounding Interferometer planned for the European polar platform Meteorological Operational Satellite in 2000. The method is based on simple statistical laws that directly relate the measured radiances to the radiative forcing by use of an a priori selection of appropriate spectral intervals and global modeling of methane spatial variations. This procedure avoids the use of an indirect determination based on an inversion process that requires precise knowledge of the methane vertical profiles throughout the troposphere. The overall accuracy and precision of this new algorithm are studied, and interfering gases and instrumental characteristics are taken into account. It is shown that radiative forcing can be determined at high horizontal spatial resolution with a precision better than 7% in cloud-free conditions and with well-known surface properties. © 1998 Optical Society of America.
BibTeX:
@article{Chazette1998,
  author = {Chazette, P. and Clerbaux, C. and Mégie, G.},
  title = {Direct estimate of methane radiative forcing by use of nadir spectral radiances},
  journal = {Applied Optics},
  year = {1998},
  volume = {37},
  pages = {3113-3120},
  doi = {10.1364/AO.37.003113}
}
Abstract: Infrared spectra of 16O12C17O, 17O12C17O, and 17O12C18O in a carbon dioxide sample enriched with oxygen-17 have been recorded with a resolution of about 0.0025 cm-1 in the regions of the fundamental bands, v2 (600-800 cm-1) and v3 (2200-2400 cm-1), and in the region of the "forbidden" band, v1 (1200-1400 cm-1), using the long path difference Fourier transform spectrometer of the LPMA in Paris. For each species, the first hot band in the 4.5-μm region and two hot bands at least in the 15-μm region have been studied for the first time, and a simultaneous reduction of wavenumbers measured in different spectral regions has been carried out yielding new or improved spectroscopic constants. Line intensities have been measured in the region of the v2 and v3 bands of 16O12C17O, and the corresponding rotationless transition dipole moments and Herman-Wallis coefficients have been reported. © 1998 Academic Press.
BibTeX:
@article{Claveau1998,
  author = {Claveau, C. and Teffo, J.-L. and Hurtmans, D. and Valentin, A.},
  title = {Infrared fundamental and first hot bands of O12C17O isotopic variants of carbon dioxide},
  journal = {Journal of Molecular Spectroscopy},
  year = {1998},
  volume = {189},
  pages = {153-195},
  doi = {10.1006/jmsp.1998.7546}
}
Abstract: Within the next 5 years, several instruments launched on polar orbiting satellites will provide high-resolution infrared remote-sensing measurements of CO, CH4, and O3 on a global scale. The upwelling spectral radiances to be recorded by a nadir-looking remote sensor have been simulated using a high-resolution radiative code (line-by-line radiative transfer model (LBLRTM)) coupled to a three-dimensional chemical transport model (intermediate model of the annual and global evolution of species (IMAGES)). The instrumental specifications of the Fourier transform interferometric monitor for greenhouse gases/Advanced Earth Observing System (IMG/ADEOS) and infrared atmospheric sounding interferometer ( IASI/METOP) were used to generate realistic data. Calculations have been performed to assess the sensitivity of the nadir spectral radiances to changes in the gas concentration, temperature profile and to instrumental characteristics. We provide spectral intervals for an efficient retrieval of these species, together with a set of climatological tropospheric standard mixing ratio profiles. Copyright 1998 by the American Geophysical Union.
BibTeX:
@article{Clerbaux1998,
  author = {Clerbaux, C. and Chazette, P. and Hadji-Lazaro, J. and Mégie, G. and Müller, J.-F. and Clough, S.A.},
  title = {Remote sensing of CO, CH4, and O3 using a spaceborne nadir-viewing interferometer},
  journal = {Journal of Geophysical Research Atmospheres},
  year = {1998},
  volume = {103},
  article number = {98JD01422},
  pages = {18999-19013}
}
Abstract: Careful measurements of the pressure effect on spectral line profiles is a powerful technique to probe intermolecular forces at work during close molecular encounters. But parameters derived from laboratory line profile studies (intensity, broadening coefficients, detailed line shape ) are also of major practical importance for many atmospheric applications based on high resolution quantitative spectroscopy in the infrared region. The final precision on the determination of spectroscopic line parameters using infrared tunable diode laser (TDL) spectrometers is limited by the exact knowledge of the emission intensity distribution of the diode. An illustration of the problem and an appropriate technique to take this TDL emission function into account are presented for two different lead salt diodes With this technique and with proper consideration of the zero transmission offset, the precise determination of line intensities, line broadening coefficients and non Voigt line shape parameters will be discussed. An interesting application of our technique to the measurement of the N2O concentration in stratospheric air samples (brought back to the laboratory) will be presented.
BibTeX:
@article{Henry1998,
  author = {Henry, A. and Hurtmans, D. and Valentin, A. and Camy-Peyret, C.},
  title = {Analysis of line profiles taking into account the intensity distribution within a TDL emission mode and precise concentration measurements of atmospheric air samples},
  journal = {VDI Berichte},
  year = {1998},
  pages = {223-232}
}
Abstract: The rate constant for the reaction of the hydroxyl radical with 1,1,1,3,3-pentafluorobutane (HFC-365mfc) has been determined over the temperature range 278-323 K using a relative rate technique. The results provide a value of k(OH + CF3CH2CF2CH3) = 2.0 × 10-12 exp(- 1750 ± 400/T) cm3 molecule-1 s-1 based on k(OH + CH3CCl3) = 1.8 × 10-12 exp (- 1550 ± 150/T) cm3 molecule-1 s-1 for the rate constant of the reference reaction. Assuming the major atmospheric removal process is via reaction with OH in the troposphere, the rate constant data from this work gives an estimate of 10.8 years for the tropospheric lifetime of HFC-365mfc. The overall atmospheric lifetime obtained by taking into account a minor contribution from degradation in the stratosphere, is estimated to be 10.2 years. The rate constant for the reaction of Cl atoms with 1,1,1,3,3-pentafluorobutane was also determined at 298 ± 2 K using the relative rate method, k(Cl + CF3CH2CF2CH3) = (1.1 ± 0.3) × 10-15 cm3 molecule-1 s-1. The chlorine initiated photooxidation of CF3CH2CF2CH3 was investigated from 273-330 K and as a function of O2 pressure at 1 atmosphere total pressure using Fourier transform infrared spectroscopy. Under all conditions the major carbon-containing products were CF2O and CO2, with smaller amounts of CF3O3CF3. In order to ascertain the relative importance of hydrogen abstraction from the - CH2 - and - CH3 groups in CF3CH2CF2CH3, rate constants for the reaction of OH radicals and Cl atoms with the structurally similar compounds CF3CH2CCl2F and CF3CH2CF3 were also determined at 298 K k(OH + CF3CH2CCl2F) = (8 ± 3) × 10-16 cm3 molecule-1 s-1; k(OH + CF3CH2CF3) = (3.5 ± 1.5) × 10-16 cm3 molecule-1 s-1; k(Cl + CF3CH2CCl2F) = (3.5 ± 1.5) × 10-17 cm3 molecule-1 s-1; k(C; + CF3CH2F3) &lt; 1 × 10-17 cm3 molecule-1 s-1. The results indicate that the most probable site for H-atom abstraction from CF3CH2CF2CH3 is the methyl group and that the formation of carbonyl compounds containing more than a single carbon atom will be negligible under atmospheric conditions, carbonyl difluoride and carbon dioxide being the main degradation products. Finally, accurate infrared absorption cross-sections have been measured for CF3CH2CF2CH3, and jointly used with the calculated overall atmospheric lifetime of 10.2 years, in the NCAR chemical-radiative model, to determine the radiative forcing of climate by this CFC alternative. The steady-state Halocarbon Global Warming Potential, relative to CFC-11, is 0.17. The Global Warming Potentials relative to CO2 are found to be 2210, 790, and 250, for integration time-horizons of 20, 100, and 500 years, respectively. © 1997 John Wiley &amp; Sons, Inc.
BibTeX:
@article{Barry1997,
  author = {Barry, J. and Locke, G. and Scollard, D. and Sidebottom, H. and Treacy, J. and Clerbaux, C. and Colin, R. and Franklin, J.},
  title = {1,1,1,3,3,-pentafluorobutane (HFC-365mfc): Atmospheric degradation and contribution to radiative forcing},
  journal = {International Journal of Chemical Kinetics},
  year = {1997},
  volume = {29},
  pages = {607-617}
}
Abstract: We have recorded the dispersed laser-induced fluorescence spectrum of gas-phase C60 ablated from a rotating copper cylinder by 308 nm radiation from a XeCl excimer laser. At vibrational energies below 7000 cm-1 the spectrum consists of three progressions of transitions to the electronic ground state ending on the odd vibrational levels of the lowest frequency t2u mode, with the lowest hu and gu modes as additional origins or on the vibrational levels of the third hg mode with two quanta of the lowest gu mode and the combination hu(1)+gu(1) as the additional origins. At higher vibrational energies, the observed bands become more complex and have yet to be analysed.
BibTeX:
@article{Firth1997,
  author = {Firth, S. and Coheur, P.F. and Mitzner, R. and Carleer, M. and Campbell, E.E.B. and Colin, R. and Kroto, H.W.},
  title = {The dispersed laser-induced fluorescence spectrum of gas-phase C60 at 308 nm},
  journal = {Journal of Physics B: Atomic, Molecular and Optical Physics},
  year = {1997},
  volume = {30},
  pages = {L393-L400},
  doi = {10.1088/0953-4075/30/11/003}
}
BibTeX:
@article{Georges1997,
  author = {Georges, R. and Van Der Vorst, D. and Herman, M. and Hurtmans, D.},
  title = {Ar and Self-Pressure Broadening Coefficient of the R(11), 5v3 Line of 12C2H2},
  journal = {Journal of Molecular Spectroscopy},
  year = {1997},
  volume = {185},
  pages = {187-188}
}
Abstract: The 13CD3OH methanol isotopomer is known to be an efficient FIR lasing molecule when optically pumped by a CO2 laser. One hundred and eighty-nine (189) FIR laser lines have been detected in laboratories to date and the frequencies of 80 of these have been accurately measured by heterodyne techniques. They include the third most efficient FIR laser line at 127 μm (the first and second most efficient FIR laser lines are at 123.5 μm and 118.8 μm for CH3OH) and a very long wavelength line at 2615 μm. The present work extends the identification of IR-pump/FIR-laser line systems with assistance from high-resolution FT-spectra. New assignments with full quantum numbers have been made for 44 FIR laser lines and partial J-assignments for 7 additional lines. This brings to 100 the total of FIR laser lines spectroscopically assigned to date for 13CD3OH. In the course of this work, we have compiled and updated all known information on the IR-pump/FIR-laser observations and spectroscopic assignments for CD3OH, and have made some substantial corrections to the existing literature on assignments. Very close FIR laser doublets reported for one system are associated with asymmetry splitting for K= 8 A levels in the excited 13CO-stretching state, representing the highest K state for which asymmetry doubling has been resolved for methanol and suggesting the presence of interesting vibrational perturbation and mode coupling. © 1997 Elsevier Science B.V.
BibTeX:
@article{Xu1997,
  author = {Xu, L.-H. and Hurtmans, D.},
  title = {Review of optically pumped FIR laser observations and FT-spectra-assisted FIR laser assignments for 13CD3OH},
  journal = {Infrared Physics and Technology},
  year = {1997},
  volume = {38},
  pages = {357-372}
}
Abstract: The spectrum of scandium was recorded in the infrared region using a high resolution Fourier transform spectrometer and a hollow-cathode discharge. Hyperfine structures of the lines connecting the 3d24s and 3d4s4p level systems of Sc45I were observed between 4000 and 5000cm-1. The structures were not completely resolved but the individual line contributions to the complex profiles were simulated using the 3d24s 4FJ hyperfine structure constants previously measured with a high precision by laser techniques. We investigate the possibility of extracting the hyperfine constants of the 3d4s4p levels from a least-squares fit of the line profiles, assuming a Doppler lineshape and theoretical relative intensities. New results are presented for 12 levels.
BibTeX:
@article{Aboussaid1996,
  author = {Aboussaïd, A. and Carleer, M. and Hurtmans, D. and Biémont, E. and Godefroid, M.R.},
  title = {Hyperfine structure of Sc I by infrared fourier transform spectroscopy},
  journal = {Physica Scripta},
  year = {1996},
  volume = {53},
  pages = {28-32}
}
Abstract: The results of an intercomparison campaign of eight different long path UV-visible DOAS instruments measuring NO2, O3 and SO2 concentrations in a moderately polluted urban site are presented. For effective optical path lengths of 230 and 780 m the overall spread of these measurements (± 1 σ) are 5 x 1010, 6 x 1010 and 1 x 1010 molec·cm-3 (2.0, 2.4, and 0.4 ppb) for these molecules respectively when all instruments used a common set of absorption cross sections. The remaining differences are not completely random and the systematic differences are attributed to the different retrieval methods used for each instrument.
BibTeX:
@article{Camy-Peyret1996,
  author = {Camy-Peyret, C. and Bergqvist, B. and Galle, B. and Carleer, M. and Clerbaux, C. and Colin, R. and Fayt, C. and Goutail, F. and Nunes-Pinharanda, M. and Pommereau, J.P. and Hausmann, M. and Platt, U. and Pundt, I. and Rudolph, T. and Hermans, C. and Simon, P.C. and Vandaele, A.C. and Plane, J.M.C. and Smith, N.},
  title = {Intercomparison of instruments for tropospheric measurements using differential optical absorption spectroscopy},
  journal = {Journal of Atmospheric Chemistry},
  year = {1996},
  volume = {23},
  pages = {51-80},
  doi = {10.1007/BF00058704}
}
Abstract: Absorption cross sections of gas phase C60 and C70 in the 40 000 to 16 000 cm-1 region have been determined. The results are based on the combination of absorbance measurements of fullerene vapour, produced by the sublimation of samples in quartz double cells, and the vapour pressure measurements of the literature for solvent-free solid fullerenes. The gas phase cross sections are compared to those derived from molar extinction coefficients of C60 and C70 in hexane solutions and highlight the problems associated with the evaporation of solvent-containing fullerenes.
BibTeX:
@article{Coheur1996,
  author = {Coheur, P.F. and Carleer, M. and Colin, R.},
  title = {The absorption cross sections of C60 and C70 in the visible-UV region},
  journal = {Journal of Physics B: Atomic, Molecular and Optical Physics},
  year = {1996},
  volume = {29},
  pages = {4987-4995},
  doi = {10.1088/0953-4075/29/21/013}
}
Abstract: Lines of the CO fundamental band are studied at low concentration in He, Ne, Ar, Xe or N2 as buffer gas from 10 to 600 torr. The coefficient β0 associated with the Dicke narrowing effect is determined for each of the five mixtures. To obtain the proper value of this coefficient, when the pressure increases, the absorber speed dependence of the pressure broadening γ0 must be taken into account. Pressure shifts are also measured, and a faint asymmetry is observed for the CO-Xe mixture. The line scanning is done with a TDL tightly controlled by a Michelson interferometer. A precision better than one-thousandth for absorbed intensity and a wavenumber precision of a few 10-5 is reached. These precisions were found necessary for the needed parameter measurements. Copyright © 1996 Elsevier Science Ltd.
BibTeX:
@article{Henry1996,
  author = {Henry, A. and Hurtmans, D. and Margottin-Maclou, M. and Valentin, A.},
  title = {Confinement narrowing and absorber speed dependent broadening effects on CO lines in the fundamental band perturbed by Xe, Ar, Ne, He and N2},
  journal = {Journal of Quantitative Spectroscopy and Radiative Transfer},
  year = {1996},
  volume = {56},
  pages = {647-671},
  doi = {10.1016/S0022-4073(96)00118-5}
}
Abstract: High resolution Fourier transform absorption spectra of the 14N16O2 molecule recorded in the 3000-3400 cm-1 and 1520-1600 cm-1 spectral regions have been analyzed. In this way lines of the 2ν3, 4ν2, 2ν2 + ν3, and 2ν3 - ν3 bands of 14N16O2 have been assigned with Ka values ranging from O to 8 and N values up to 60. The spin-rotation energy levels were very satisfactorily reproduced using a theoretical model which takes explicitly into account both the Coriolis interaction between the spin-rotation levels of the (021) vibrational state and those of (040) and of (002), and the spin-rotation resonances within (021), (040), and (002). As a consequence, precise vibrational band centers and rotational, spin-rotation, and coupling constants were obtained for the triad (040), (002), (021) of interacting states of 14N16O2. In addition, using a large set of individual 2ν3, 4ν2, and 2ν2 + ν3 experimental line intensities at 3.2 μm, we have determined precisely the 2ν2 + ν3 and 2ν3 transition moment constants of 14N16O2. On the other hand, the transition moment constants of the 2ν3 - ν3 and 2ν2 + ν3 - 2ν2 bands were derived from those of the corresponding ν3 cold band. Finally, a comprehensive list of line positions and intensities of the interacting 4ν2, 2ν3, 2ν2 + ν3, and 2ν3 - ν3 bands of 14N16O2 has been generated at 3.2 μm and 6.2 μm, respectively, © 1996 Academic Press, Inc.
BibTeX:
@article{Perrin1996,
  author = {Perrin, A. and Flaud, J.-M. and Camy-Peyret, C. and Hurtmans, D. and Herman, M.},
  title = {The {2ν3, 4ν2, 2ν2 + ν3} and 2ν3 - ν3 bands of 14N16O2: Line positions and intensities},
  journal = {Journal of Molecular Spectroscopy},
  year = {1996},
  volume = {177},
  pages = {58-65},
  doi = {10.1006/jmsp.1996.0117}
}
Abstract: Atmospheric spectra to be recorded in the infrared spectral range by a spaceborne Fourier transform spectrometer using a nadir view have been simulated. Relevant spectral domains have been selected for the retrieval of carbon monoxide, methane, ozone and nitrous oxide. A new inversion algorithm using neural networks techniques is proposed to retrieve integrated contents and low resolution vertical profiles.
BibTeX:
@conference{Clerbaux1995,
  author = {Clerbaux, Cathy and Chazette, Patrick and Megie, Gerard J.},
  title = {Tropospheric concentrations of infrared absorbing molecules using a nadir-looking Fourier transform spectrometer},
  journal = {Proceedings of SPIE - The International Society for Optical Engineering},
  year = {1995},
  volume = {2578},
  pages = {148-153}
}
Abstract: The B3Σ--X3Σ- transition of the SO radical has been reinvestigated at high resolution for two isotopomers (32SO16O) and 32SO18O rotational analysis of several bands has led to a reassignment of the branches and to a new set of molecular constants for the v′ = 0 and v′ = 1 levels of the B state. A limiting curve of predissociation of the B3Σ- state by a shallow C3Π state has been obtained, which yields a precise value of the dissociation energy of the X3Σ- state: D″e = 43 680 ± 5 cm-1. Many new rotational perturbations were observed in the B3Σ- state, but a complete understanding of these was not possible. © 1994 Academic Press, Inc.
BibTeX:
@article{Clerbaux1994a,
  author = {Clerbaux, C. and Colin, R.},
  title = {A reinvestigation of the b3Σ--x3Σ- transition of the so radical},
  journal = {Journal of Molecular Spectroscopy},
  year = {1994},
  volume = {165},
  pages = {334-348},
  doi = {10.1006/jmsp.1994.1137}
}
Abstract: The Global Warming Potentials (GWPs) of CH2F‐CHF2 (HFC‐143) have been estimated for different time horizons. Radiative forcings associated with this CFC alternative have been derived relative to CFC‐11 and CO2 by introducing laboratory measured absorption cross sections into a coupled chemical‐radiative model. Copyright 1994 by the American Geophysical Union.
BibTeX:
@article{Clerbaux1994,
  author = {Clerbaux, C. and Colin, R.},
  title = {Determination of the infrared cross sections and global warming potentials of 1,1,2‐trifluoroethane (HFC‐143)},
  journal = {Geophysical Research Letters},
  year = {1994},
  volume = {21},
  pages = {2377-2380},
  doi = {10.1029/94GL02365}
}
Abstract: A line-removal method is used to artificially retrieve some information on weak overlapped bands in dense high-resolution spectra. This method consists of dividing the data - recorded with a Fourier transform spectrometer - by the computed spectrum of the main overlapping band. It is first demonstrated on N2O. It is then applied to the ν1 + ν3 - ν3 band of BrNO, in the region of the strong ν1 fundamental, leading to the following results: A′=2.82506(3) cm-1, B′=0.12596(2) cm-1 and ν0=1798.622(1) cm-1. © 1994.
BibTeX:
@article{Hurtmans1994,
  author = {Hurtmans, D. and Auwera, J.V. and Herman, M.},
  title = {The ν1 + ν3 - ν3 hot band of BrNO},
  journal = {Chemical Physics Letters},
  year = {1994},
  volume = {227},
  pages = {588-592},
  doi = {10.1016/0009-2614(94)00869-8}
}
Abstract: High-resolution Fourier transform spectra recorded in the 2270-2400 cm-1 and 1520-1600 cm-1 spectral regions have been used to measure, up to very high N values, the positions of lines with Ka = 0-9 of the ν2 + ν3 and ν2 + ν3 - ν2 bands of 14N16O2 as well as their absolute intensities and a self broadening coefficient γ0 = 0.095 ± 0.032 cm-1 atm-1 (at 292 K). The spin-rotation energy levels were very satisfactorily reproduced using a theoretical model which explicitly takes into account both the Coriolis interaction between the spin-rotation levels of the (011) vibrational state and those of (030), and the spin-rotation resonances within (011) and (030). As a consequence, precise vibrational band centers and rotational, spin-rotation, and coupling constants were obtained for the diad (030), (011) of interacting states for 14N16O2. In addition, using a large set of individual ν2 + ν3 line intensities, we have determined precisely the ν2 + ν3 transition moments of 14N16O2. On the other hand, the transition moments of the ν2 + ν3 - ν2 and 3ν2 - ν2 bands were derived from those of the corresponding ν3 and 2ν2 cold bands. Finally, a comprehensive list of line positions and intensities of the interacting ν2 + ν3, 3ν2 and ν2 + ν3 - ν2, 3ν2 - ν2 bands of 14N16O2 has been generated at 4.2 and 6.2 μm, respectively. © 1994 Academic Press, Inc.
BibTeX:
@article{Perrin1994,
  author = {Perrin, A. and Flaud, J.M. and Camy-Peyret, C. and Hurtmans, D. and Herman, M. and Guelachvili, G.},
  title = {The ν2 + ν3 and ν2 + ν3 - ν2 bands of 14n16o2: Line positions and intensities},
  journal = {Journal of Molecular Spectroscopy},
  year = {1994},
  volume = {168},
  pages = {54-66},
  doi = {10.1006/jmsp.1994.1259}
}
Abstract: Absorption cross sections have been obtained in the infrared atmospheric window, between 600 and 1500 cm-1, for 10 alternative hydrohalocarbons: HCFC22, HCFC123, HCFC124, HCFC141b, HCFC142b, HCFC225ca, HCFC225cb, HFC125, HFC134a and HFC152a. The measurements were made at three temperatures (287 K, 270 K and 253 K) with a Fourier transform spectrometer operating at 0.03 cm-1 apodized resolution. Integrated cross sections have been introduced into a two-dimensional radiative-chemical-dynamical model in order to calculate the global warming potential (GWP) of each gas. -Authors
BibTeX:
@article{Clerbaux1993,
  author = {Clerbaux, C. and Colin, R. and Simon, P.C. and Granier, C.},
  title = {Infrared cross sections and global warming potentials of 10 alternative hydrohalocarbons},
  journal = {Journal of Geophysical Research},
  year = {1993},
  volume = {98},
  pages = {10,491-10,497}
}
Abstract: We have measured the integrated band intensities of the ν9 and ν11 bands of N2O4 which are observed around 1757 and 1261 cm-1, respectively. By varying temperature and pressure, we have obtained: Sband(ν9) = 9.60(130), 9.10(24), 8.80(66) and Sband(ν11)= 5.93(64), 5.70(21) and 5.33(46) (in 10-17 cm/molecule) at 293.15 (60), 277.25 (60) and 261.65 (60) K, respectively. © 1993.
BibTeX:
@article{Hurtmans1993,
  author = {Hurtmans, D. and Herman, M. and Vander Auwera, J.},
  title = {Integrated band intensities in N2O4 in the infrared range},
  journal = {Journal of Quantitative Spectroscopy and Radiative Transfer},
  year = {1993},
  volume = {50},
  pages = {595-602},
  doi = {10.1016/0022-4073(93)90027-F}
}
Abstract: Absolute line positions and intensities are provided for the ν3 fundamental in C2H2 with an accuracy estimated to respectively 6 × 10-4 cm-1 and 0.05 cm-2 atm-1. Unperturbed values are derived for the energy and intensity parameters by treating the Fermi-type resonance and k-doubling effects involved through the interaction with the ν2 + ν4 + ν5 level. The complete set of k-components is included in the procedure. Fitting procedures are carried our on the line energies, the line intensities, and both sets of information simultaneously. The main results are, for the deperturbed values: E(ν3) = 3288.58075(13) cm-1, E(ν2 + ν4 + ν5) = 3296.79650(9)cm-1, k2345 = 25.86749(13) cm-1, and the transition moments Rv(ν3) = ±0.08907(3) D and Rv(ν2 + ν4 + ν5) = ∓2.63(3) × 10-3 D. with the errors (1σ) quoted on the last digits. The mixing between the various levels is quantitatively discussed. © 1993 Academic Press, Inc.
BibTeX:
@article{Vanderauwera1993,
  author = {Vanderauwera, J. and Hurtmans, D. and Carleer, M. and Herman, M.},
  title = {The ν3 Fundamental in C2H2},
  journal = {Journal of molecular spectroscopy},
  year = {1993},
  volume = {157},
  pages = {337-357},
  doi = {10.1006/jmsp.1993.1027}
}
Abstract: The absorption and the emission spectra of the BeH and BeD molecules in the region of 1850 Å are rotationally analysed. The features observed are shown to correspond to a transition between thèZ+ ground state and a 3d molecular complex that is strongly predissociated by thè C2Z+ state. Rotational constants for the v = 0 and v = 1 levels of the 3d state are derived by matrix X2Σ+diagonalization techniques, assuming interaction with the F(4pσ)2Σ+state. A tentative assignaient of previously observed absorption bands to transitions involving the v = 2 level of the 3d state is given. The 2-0 band of the B2∏-X2Σ++ transition of BeH and BeD is also identified in this region. The predissociation by the C2Σ+state is discussed. © 1991 Taylor &amp; Francis Ltd.
BibTeX:
@article{Clerbaux1991,
  author = {Clerbaux, C. and Colin, R.},
  title = {The 3d rydberg state of the beh molecule},
  journal = {Molecular Physics},
  year = {1991},
  volume = {72},
  pages = {471-486},
  doi = {10.1080/00268979100100361}
}
BibTeX:
@article{Herman1991,
  author = {Herman, M. and Hurtmans, D. and Vander Auwera, J. and Vervloet, M.},
  title = {Lack of intensity alternation in C2H2},
  journal = {Journal of Molecular Spectroscopy},
  year = {1991},
  volume = {150},
  pages = {293-295},
  doi = {10.1016/0022-2852(91)90215-V}
}

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Université Libre de Bruxelles – Faculté des Sciences