Volcanic sulfur dioxide monitored from a constellation of FengYun hyperspectral infrared sounders in dawn-dusk, mid-morning, and afternoon sun-synchronous orbits

Satellite observations offer a unique way of monitoring the spatial distribution, vertical structure and temporal variation of volcanic sulfur dioxide (SO₂) plumes. In this study, we use observations from the Hyperspectral Infrared Atmospheric Sounder (HIRAS) constellation on board China's FengYun-3 (FY-3) meteorological satellites flying in three different sun-synchronous orbits, including dawn-dusk, mid-morning, and afternoon orbits. The constellation provides six global coverages (roughly every 4-h) each day, with equatorial overpass times at 5:30 am/pm for FY-3E, 10:00 am/pm for FY-3F, and 2:00 am/pm for FY-3D. We retrieve SO₂ total column and layer height from the Ruang volcanic eruptions in April 2024. The retrievals show consistency among the different HIRAS and are highly correlated with IASI and TROPOMI observations. The e-folding time of the volcanic SO₂ mass is estimated to be 9.0 ± 2.8 days, which is representative of a plume in the Upper Troposphere-Lower Stratosphere (UTLS). Lastly, we apply the methods to the eruptions of the Russia's Sheveluch volcano in November 2024 at high latitudes and show the effectiveness and high consistency among the HIRAS sensors in detecting the SO₂ signal. This study demonstrates the capability of a global constellation of FengYun hyperspectral infrared sounders to monitor SO₂ emissions from volcanic eruptions.