Using the FY-3E satellite hyperspectral infrared atmospheric sounder to quantitatively monitor volcanic SO₂

Abstract. The Hyperspectral Infrared Atmospheric Sounder Type II (HIRAS-II) aboard the Fengyun 3E (FY-3E) satellite provides valuable data on the vertical distribution of atmospheric states. However, effectively extracting quantitative atmospheric information from the observations is challenging due to the large number of hyperspectral sensor channels, inter-channel correlations, associated observational errors, and susceptibility of the results to influence by trace gases. This study explores the potential of FY-3E/HIRAS-II to atmospheric loadings of SO₂ from volcanic eruption. A methodology for selecting SO₂ sensitive channels from the large number of hyperspectral channels recorded by FY-3E/HIRAS-II is presented. The methodology allows for the selection of SO₂-sensitive channels that contain similar information on variations in atmospheric temperature and water vapor for minimizing the influence of atmospheric water vapor and temperature to SO₂. A sensitivity study shows that the difference in brightness temperature between the experimentally selected SO₂ sensitive channels and the background channels effectively removes interference signals from surface temperature, atmospheric temperature, and water vapor during SO₂ detection and inversion. A positive difference between near-surface atmospheric temperature and surface temperature enables the infrared band to capture more SO₂ information in the lower and middle layers. The efficacy of FY-3E/HIRAS-II SO₂ sensitive channels in quantitively monitor volcanic SO₂ is demonstrated using data from the 29 April 2024 eruption of Mount Ruang in Indonesia. Using FY-3E/HIRAS-II measurements, the spatial distribution and quantitatively information of volcanic SO₂ are easily observed. The channel selection can significantly enhance the computation efficiency while maintain the accuracy of SO₂ detection and retrieval, despite the large volume of data.