Contribution of Geostationary Satellites to the Observation of Atmospheric NH3

Le résumé fourni par la source

Ammonia (NH3) is an atmospheric pollutant mainly emitted by the agricultural sector, which has an effect on public health since it is a precursor of fine particles (PM2.5). The diurnal variability of NH3 in the atmosphere and its transformation into particles are poorly constrained and strongly depend on meteorological parameters, in particular temperature. Polar orbit satellite observations, such as the Infrared Atmospheric Sounder Instrument (IASI), are keys to assess spatio-temporal variabilities of NH3 with observations twice a day. Geostationary instruments offer a comprehensive assessment of NH3 diurnal variability and its dependence on atmospheric temperature. This study analyses the contribution of geostationary instruments to observe ammonia variabilities and their link to atmospheric temperature. We use IASI observations, as well as the Geostationary Interferometric Infrared Sounder (GIIRS) on board China’s FengYun-4B satellite launched in June 2021 that measure atmospheric ammonia over East Asia and parts of South Asia and Southeast Asia every 2 hours at 12 km at nadir. We also evaluate the InfraRed Sounder (IRS) instrument that will be launched onboard the Meteosat Third Generation (MTG) satellite into geostationary orbit over Europe and Africa in late 2025. IRS will offer the ability to assess NH3 diurnal variabilities with frequent measurements (every 30-45 minutes) and better spatially resolved observations than IASI (4 km x 4 km at the Equator and Greenwich meridian). In this work, GIIRS NH3 total columns are validated with IASI observations between July 2022 and June 2024. Then, the link between NH3 variabilities and atmospheric temperature are analyzed over Asia using GIIRS observations. Finally, a NH3 sensitivity analysis considering measurement noises is made for the future IRS-MTG mission and is discussed with respect to IASI.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.