Monitoring air pollution at global scale using the IASI thermal infrared instrument
Résumé
Air quality is a major health concern in most megacities and important industrial regions. It is therefore important to properly quantify the emissions of the main air pollutants and to understand their transport pathways and their reactivity in the atmosphere. In recent years, there have been important progresses to monitor near-surface atmospheric composition from satellites, which offer the possibility to draw spatial distributions from local to global scale as well as time evolutions for a series of regulated air quality species. Among the sounders currently in orbit, those operating in the thermal infrared have usually their maximum sensitivity in the mid-troposphere but have been shown to be able to monitor air surface pollution when the temperature contrast between the ground and the air above it is sufficiently large.
In this work, we will present a series of results demonstrating the capability of infrared sounders to measure surface air composition. We will focus the presentation on the measurements of sulfur dioxide (SO2) and carbon monoxide (CO) from the IASI instrument. More specifically, the development of a new product allowing the retrieval of SO2 from IASI observations at global scale will be briefly presented. Global distributions of anthropogenic SO2 surface pollution will be shown, focusing on the identification of the principal hotspots and of exceptional pollution events. In addition, we will provide results of CO pollution from IASI and show how in favorable conditions, the surface CO concentration can be de-correlated from the free tropospheric abundance. We will put the results in the perspective of current and future missions, which, by combining infrared and UV sounding missions, offer improved possibilities for the global surveillance of air quality.