Abstract
Abstract. In this study we describe a methodology to create high-vertical-resolution SO2 profiles from volcanic emissions. We demonstrate the method's performance for the volcanic clouds following the eruption of Sarychev in June 2009. The resulting profiles are based on a combination of satellite SO2 and aerosol retrievals together with trajectory modelling. We use satellite-based measurements, namely lidar backscattering profiles from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) satellite instrument, to create vertical profiles for SO2 swaths from the Atmospheric Infrared Sounder (AIRS) aboard the Aqua satellite. Vertical profiles are created by transporting the air containing volcanic aerosol seen in CALIOP observations using the FLEXible PARTicle dispersion model (FLEXPART) while preserving the high vertical resolution using the potential temperatures from the MERRA-2 (Modern-Era Retrospective analysis for Research and Application) meteorological data for the original CALIOP swaths. For the Sarychev eruption, air tracers from 75 CALIOP swaths within 9 d after the eruption are transported forwards and backwards and then combined at a point in time when AIRS swaths cover the complete volcanic SO2 cloud. Our method creates vertical distributions for column density observations of SO2 for individual AIRS swaths, using height information from multiple CALIOP swaths. The resulting dataset gives insight into the height distribution in the different sub-clouds of SO2 within the stratosphere. We have compiled a gridded high-vertical-resolution SO2 inventory that can be used in Earth system models, with a vertical resolution of 1 K in potential temperature, 61 ± 56 m, or 1.8 ± 2.9 mbar.
Highlights
Volcanism can affect the climate by increasing aerosol levels in the stratosphere (Robock, 2000)
We investigated the vertical distribution of the depolarization ratio and colour ratio in relation to the scattering ratio for the 75 Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) swaths
Using the supporting meteorological dataset for the CALIOP swaths, our final vertical profiles have a resolution of 1 K in potential temperature
Summary
Volcanism can affect the climate by increasing aerosol levels in the stratosphere (Robock, 2000). CALIOP and AIRS are part of the large family of satellite instruments measuring aerosol and SO2 (Thies and Bendix, 2011) Another instrument is the Infrared Atmospheric Sounding Interferometer (IASI), aboard the METOP satellite, which has been used to infer a plume altitude and SO2 levels simultaneously from high-spectral-resolution measurements (Carboni et al, 2016). The FLEXible PARTicle dispersion model (FLEXPART) (Pisso et al, 2019) is used to transport the horizontally thin CALIOP observations to the time and location of the SO2 swaths This approach enables us to use height information from multiple CALIOP swaths for each AIRS swath, giving a more complete view of the SO2 clouds vertical profiles; see Fig. 1. Using this collection of AIRS swaths, the complete SO2 emissions are studied in this paper
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