Global ammonia distributions derived from infrared space observations
Résumé
Recently, satellite sounders have demonstrated the possibility to probe atmospheric ammonia which opens new and unexpected perspectives to monitor that species (Beer et al., 2008; Clarisse et al., 2009; Coheur et al., 2009). We use the 3 years of IASI data to identify a multitude of hotspots, notably over biomass burning regions and agricultural areas and study correlations with agriculture intensity. We analyse NH3 temporal variations of intensive agricultural areas and provide first comparisons with ground based and/or airborne measurements. Satellite remote sensing is essential for monitoring atmospheric composition and changes. It completes ground-based and airborne measurements (which are limited in spatial and temporal coverage) to improve understanding and monitoring of the evolution of our global atmosphere. The Infrared Atmospheric Sounding Interferometer (IASI) is a passive remote-sensing instrument operating in nadir mode that measures infrared radiation emitted by the Earth surface and the atmosphere in the 645-2760 cm-1 spectral range (Clerbaux et al., 2009). The instrument was launched in 2006 on-board the MetOp-A meteorological platform, which circles in a polar sun-synchronous orbit around the Earth and will provide 15 years of global coverage of atmosphere two times per day. From the high-spectral data we can retrieve concentrations of up to 24 species and of aerosols in the atmosphere. Ammonia concentrations are retrieved from calibrated radiance spectra in near-real-time using sophisticated radiative transfer model and inverse method. Only the day-time orbits (with an overpass at 9.30am) are used in this work, as they show better surface sensitivity. Results