Abstract
Abstract. Reported sulfur dioxide (SO2) emissions from US and Canadian sources have declined dramatically since the 1990s as a result of emission control measures. Observations from the Ozone Monitoring Instrument (OMI) on NASA's Aura satellite and ground-based in situ measurements are examined to verify whether the observed changes from SO2 abundance measurements are quantitatively consistent with the reported changes in emissions. To make this connection, a new method to link SO2 emissions and satellite SO2 measurements was developed. The method is based on fitting satellite SO2 vertical column densities (VCDs) to a set of functions of OMI pixel coordinates and wind speeds, where each function represents a statistical model of a plume from a single point source. The concept is first demonstrated using sources in North America and then applied to Europe. The correlation coefficient between OMI-measured VCDs (with a local bias removed) and SO2 VCDs derived here using reported emissions for 1° by 1° gridded data is 0.91 and the best-fit line has a slope near unity, confirming a very good agreement between observed SO2 VCDs and reported emissions. Having demonstrated their consistency, seasonal and annual mean SO2 VCD distributions are calculated, based on reported point-source emissions for the period 1980–2015, as would have been seen by OMI. This consistency is further substantiated as the emission-derived VCDs also show a high correlation with annual mean SO2 surface concentrations at 50 regional monitoring stations.
Highlights
Sulfur dioxide (SO2) is a designated criteria air pollutant that enters the atmosphere through anthropogenic and natural processes
We demonstrate how European SO2 emissions can be estimated from Ozone Monitoring Instrument (OMI) vertical column densities (VCDs) data
Fitting OMI SO2 VCD data by a linear combination of functions, where each function represents the plume from an individual source, makes it possible to estimate emission from these sources or groups of sources
Summary
Sulfur dioxide (SO2) is a designated criteria air pollutant that enters the atmosphere through anthropogenic (e.g., combustion of sulfur-containing fuels, oil refining processes, metal ore smelting operations) and natural processes (e.g., volcanic eruptions and degassing). This study is focused on the eastern US and southeastern Canada, where the majority of large North American SO2 emission sources (mainly coal-burning power plants) are located, where the changes in both reported emissions and measured VCDs are large, and where emissions are measured directly at the stack for most sources. In this region, there is a network with long-term records of uniform SO2 surface concentration measurements. We demonstrate how European SO2 emissions can be estimated from OMI VCD data
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