Abstract
The presence of volcanic clouds in the atmosphere affects air quality, the environment, climate, human health and aviation safety. The importance of the detection and retrieval of volcanic SO2 lies with risk mitigation as well as with the possibility of providing insights into the mechanisms that cause eruptions. Due to their intrinsic characteristics, satellite measurements have become an essential tool for volcanic monitoring. In recent years, several sensors, with different spectral, spatial and temporal resolutions, have been launched into orbit, significantly increasing the effectiveness of the estimation of the various parameters related to the state of volcanic activity. In this work, the SO2 total masses and fluxes were obtained from several satellite sounders—the geostationary (GEO) MSG-SEVIRI and the polar (LEO) Aqua/Terra-MODIS, NPP/NOAA20-VIIRS, Sentinel5p-TROPOMI, MetopA/MetopB-IASI and Aqua-AIRS—and compared to one another. As a test case, the Christmas 2018 Etna eruption was considered. The characteristics of the eruption (tropospheric with low ash content), the large amount of (simultaneously) available data and the different instrument types and SO2 columnar abundance retrieval strategies make this cross-comparison particularly relevant. Results show the higher sensitivity of TROPOMI and IASI and a general good agreement between the SO2 total masses and fluxes obtained from all the satellite instruments. The differences found are either related to inherent instrumental sensitivity or the assumed and/or calculated SO2 cloud height considered as input for the satellite retrievals. Results indicate also that, despite their low revisit time, the LEO sensors are able to provide information on SO2 flux over large time intervals. Finally, a complete error assessment on SO2 flux retrievals using SEVIRI data was realized by considering uncertainties in wind speed and SO2 abundance.
Highlights
During their degassing and eruptive activities, volcanoes emit large quantities of gases and particles into the atmosphere
The temporal variation of SO2 flux can be used as a precursor of volcanic eruptions [21,26,27,28]
The total masses tected from the multispectral sensors Spinning Enhanced Visible and InfraRed Imager (SEVIRI), Moderate Resolution Imaging Spectroradiometer (MODIS) and Visible Infrared Imaging Radiometer Suite (VIIRS)
Summary
During their degassing and eruptive activities, volcanoes emit large quantities of gases and particles into the atmosphere. The SO2 flux yields insights into the magmatic processes that control volcanic activity during both quiescent and eruptive phases [20,21] and gives information on magma-gas separation depths, conduit structure and magma pressure [2,22]. The temporal variation of SO2 flux can be used as a precursor of volcanic eruptions [21,26,27,28]. For all these reasons, there is great interest in improving the quality and frequency of volcanic SO2 mass and flux measurements in real time
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