Estimation of SO2 emissions using OMI retrievals

Satellite sulfur dioxide (SO2) measurements from the Ozone Monitoring Instrument (OMI) satellite sensor, averaged over a period of several years, were compared with emissions inventories for major US sources. Low‐ and high‐ spatial frequency filtration was applied to OMI data to reduce the noise and bias to enhance and reveal weak SO2 signals that are otherwise not readily apparent. Averaging a large number of individual observations enables the study of SO2 spatial distributions near larger SO2 emissions sources with an effective resolution superior to that of an individual OMI observation and even to obtain rough estimates of the emissions level from those sources. It is demonstrated that individual sources (or multiple sources within 50 km) with annual SO2 emissions greater than about 70 kT y−1 produce a statistically significant signal in 3‐year averaged OMI data. A correlation of 0.93 was found between OMI SO2 integrated around the source and the annual SO2 emission rate for the sources greater than 70 kT y−1. OMI SO2 data also indicate a 40% decline in SO2 values over the largest US coal power plants between 2005–2007 and 2008–2010, a value that is consistent with the reported 46% reduction in annual emissions due to the implementation of new SO2 pollution control measures over this period. Key Points Satellite instruments (OMI) can see individual SO2 emission sources in the US There is a high correlation between SO2 emissions and OMI data OMI confirms a decline in SO2 emissions as a result of pollution control measure