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Geological Survey of Japan, Institute of Advanced Science and Technology,
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- PublicationRestrictedMeasuring volcanic degassing of SO2 in the lower troposphere with ASTER band ratios(2010)
; ; ; ; ; ; ; ; ; ; ;Campion, R.; Université Libre de Bruxelles, Département des Sciences de la Terre et de l'Environnement. ;Salerno, G. G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Coheur, P. F.; Université Libre de Bruxelles, Chimie Quantique et Photophysique, ;Hurtmans, D.; Université Libre de Bruxelles, Chimie Quantique et Photophysique ;Clarisse, L.; Université Libre de Bruxelles, Chimie Quantique et Photophysique ;Kazahaya, K.; Geological Survey of Japan, Institute of Advanced Science and Technology, ;Burton, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Caltabiano, T.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Clerbaux, C.; Université Libre de Bruxelles, Chimie Quantique et Photophysique, ;Bernard, A.; Université Libre de Bruxelles, Département des Sciences de la Terre et de l'Environnement.; ; ; ; ; ; ; ; ; We present a new method for measuring SO2 with the data from the ASTER (Advanced Spaceborne Thermal Emission and Reflectance radiometer) orbital sensor. The method consists of adjusting the SO2 column amount until the ratios of radiance simulated on several ASTER bands match the observations. We present a sensitivity analysis for this method, and two case studies. The sensitivity analysis shows that the selected band ratios depend much less on atmospheric humidity, sulfate aerosols, surface altitude and emissivity than the raw radiances. Measurements with b25% relative precision are achieved, but only when the thermal contrast between the plume and the underlying surface is higher than 10 K. For the case studies we focused on Miyakejima and Etna, two volcanoes where SO2 is measured regularly by COSPEC or scanning DOAS. The SO2 fluxes computed from a series of ten images of Miyakejima over the period 2000–2002 is in agreement with the long term trend of measurement for this volcano. On Etna, we compared SO2 column amounts measured by ASTER with those acquired simultaneously by ground-based automated scanning DOAS. The column amounts compare quite well, providing a more rigorous validation of the method. The SO2 maps retrieved with ASTER can provide quantitative insights into the 2D structure of non-eruptive volcanic plumes, their dispersion and their progressive depletion in SO2.185 28