Atmospheric composition from the Geostationary Interferometric Infrared Sounder (GIIRS) on board FengYun satellite: First two years of observations

The Geostationary Interferometric Infrared Sounder (GIIRS) on board China’s FengYun-4 satellite series provides a unique opportunity to monitor the tropospheric composition over Asia using hyperspectral infrared observations from a geostationary orbit. In this study, we retrieve atmospheric carbon monoxide (CO), ammonia (NH₃), formic acid (HCOOH) and ozone (O3) for the first two years from July 2022 to June 2024 using the FengYun Geostationary satellite Atmospheric Infrared Retrieval (FY-GeoAIR) algorithm. GIIRS measures these atmospheric compounds both day and night with a temporal resolution of 2 hours and a spatial resolution of 12km at nadir. The spatial patterns, seasonal and diurnal variations of these atmospheric compounds over Asia are analyzed using the FY-4B/GIIRS retrievals. In particular, we focus on a case study of the strong emissions from forest fires over the Indochina Peninsula (ICP) in spring due to the agricultural practice of slash-and-burn. The results show that the spatial and temporal variations of wildfire enhancements of CO, NH₃ and HCOOH from Southeast Asia are well captured by the FY-4B/GIIRS. In addition, the FY-4B/GIIRS retrievals are validated with ground-based observations of CO and NH3 and compared with model simulations. Our study demonstrates the potential of GIIRS data to improve our understanding of the spatial and temporal variations of important trace gas pollutants over Asia.