Atmospheric composition measurements with the IASI hyperspectral sounder: local to global

International audienceMeasuring the atmospheric composition from space is essential for monitoring pollutants in the atmosphere and, using the synergy with models, for quantifying anthropogenic emissions and understanding the impacts of these emissions on the environment. With the advent of sophisticated optical sounders, the use of satellite data for various applications has recently emerged. In this talk we will review the principal achievements of the advanced infrared hyperspectral sounder IASI since its launch in 2006 onboard Metop-A, the first of a series of European meteorological satellites in low-earth orbit. IASI is a Michelson interferometer covering the infrared spectral domain from 645 to 2760 cm−1 (3.8-15.5 μm), at a medium spectral resolution of 0.5 cm−1. The mission is dedicated to high-resolution atmospheric sounding, with a mission accuracy requirement of 1K for tropospheric temperature and 10% for humidity, for a vertical resolution of 1 km, and to the retrieval of trace gas amounts. It is the latter aspect that we will focus on in this talk. The different steps of the processing, from the measurements of the calibrated spectral radiances to the retrieval of trace gas vertical profiles will be described. Local-to-global distributions of several important atmospheric species (O3, CO, NH3) will be shown and put in the perspective of environmental monitoring. In particular, we will give some of the IASI highlights in relation to our undestanding of tropospheric processes (emission, transport and chemistry of pollutants) and to the stratospheric ozone hole. We will also show that owing to its fairly high spatial resolution and unprecedented sampling, with global coverage twice daily, IASI is an excellent tracker of concentrated plumes, released sporadically by volcanoes, fires or mega-cities. With up to 24 species measured, including reactive organic, nitrogen and sulfur compounds, IASI sets the standard for future operational hyperspectral infrared sounders in the global Earth observing system