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Multi-Satellite Air Quality Sulfur Dioxide (SO2) Database Long-Term L4 Global V1 (MSAQSO2L4) at GES DISC

These data are a part of Multi-Decadal Sulfur Dioxide Climatology from Satellite Instruments (MEaSUREs-12-0022 project). The catalogue MSAQSO2L4 file contains the site coordinates, source type, country, source name, annual SO2 emissions and uncertainties, and the number of EOS Aura/OMI satellite SO2 measurements used for emissions estimates near each source. The 2018 data have been recently added to the catalogue and the minor version in the file name is now upgraded to v01-04. There are no systematic differences between the old and new minor versions. The fitting areas are a slightly different for some sites, but the resulting differences in the data are within the known uncertainties ranges. A major update to the catalogue is aniticipated in the summer of 2019. The emissions estimates are based on the fitting of the operational Aura/OMI planetary boundary layer (PBL) SO2 data produced with the Principal Component Analysis (PCA) algorithm (10.5067/Aura/OMI/DATA2022) and a site-specific AMF adjustment for each site (Fioletov et al., 2016). The emission estimate method for linking OMI level 2 SO2 vertical column densities (VCDs) to emissions is based on a fit of OMI VCDs to an empirical plume model developed to describe the SO2 spatial distribution (as seen by OMI) near emissions point sources. The plume model assumes that the SO2 concentrations emitted from a point source decline exponentially along wind direction and are affected by turbulent diffusion that can be described by a 2D Gaussian function. The average SO2 mass is derived from the fit and the emission rate is calculated as the ratio between the total mass and the prescribed SO2 lifetime.

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