Observing volcanic SO2 from a constellation of FengYun hyperspectral infrared sounders

Sulfur dioxide (SO2) from volcanic eruptions can have a significant impact on atmospheric chemistry and climate, and pose a threat to aviation. Satellite observations provide a unique opportunity to track the spatial distribution, vertical structure and temporal evolution of volcanic SO2 plumes. In this study, we use observations from the FengYun-3 (FY-3) series of meteorological satellites, which have formed a Hyperspectral Infrared Atmospheric Sounder (HIRAS) constellation in dawn-dusk, mid-morning and afternoon sun-synchronous orbits. The constellation provides six global observations in one day in the thermal infrared with equatorial overpass times of 5:30 am/pm (FY-3E), 10:00 am/pm (FY-3F) and 2:00 am/pm (FY-3D). SO2 layer height and total column are obtained from HIRAS spectra observations for two volcanic eruptions in 2024 in the tropics and high latitudes, respectively. The retrieval results from the three sounders are generally consistent. Intercomparisons with existing data from IASI satellites, model simulations and Microwave Limb Sounder are performed to assess the robustness of the retrieved data products. Our results show that the global FengYun-3 HIRAS constellation captures well the spatial and vertical evolution of lofted volcanic SO2 plumes after eruptions. This study represents an important application of a global constellation of FengYun hyperspectral infrared sounders for monitoring global variations in atmospheric composition.