Point sources are indicated with circles on top of IASI ten-year oversampled average (in molecules per square centimetre). The size of the circles quantifies the satellite-based emission fluxes (in kilograms per second).
Reference: Van Damme, M., Clarisse, L., Whitburn, S., Hadji-Lazaro, J., Hurtmans, D., Clerbaux, C., Coheur, P.-F. Industrial and agricultural ammonia point sources exposed. Nature 564, 99-103, doi: 10.1038/s41586-018-0747-1, 2018. Open access: SharedIt