Atmospheric Composition Applications with IASI and next-generation hyperspectral infrared sounders (IASI-NG and IRS)

Atmospheric sounding in the infrared has, for a long time, mainly been dedicated to meteorology. The operation of hyperspectral sounders has remarkably served this application area in the last two decades, up to the level that these instruments have become the dominant contributors to numerical weather forecast. Even more remarkable is, however, how the hyperspectral infrared sounders have fostered the fields of atmospheric chemistry and climate, thanks to the measurements of a large series of trace gases in the troposphere and stratosphere (see infographics in Figure 1 and e.g. [1]). In Europe, major advances have been made by exploiting radiance record of the Infrared Atmospheric Sounding Interferometer (IASI) onboard the Metop platform series, which started in 2006 and is expected to continue until 2024 at least. The long time series of available IASI measurements and its remarkable stability over time has in particular allowed characterizing the inter-annual variability of several reactive species (ozone -O 3 -, carbon monoxide -CO-, ammonia -NH 3 -), to isolate significant trends in the troposphere and the stratosphere (for 03), and to trace these to emission reductions or to changes in our environment and climate (e.g. [2], [3]). Another key achievement made with IASI lies in the detection and characterization of local point sources from agriculture and industry in averaged distributions [4].