Estimation of SO₂ emissions using OMI retrievals

[1] 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.