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New discoveries enabled by OMI SO2 measurements

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Monday, December 7, 2009, 4 pm

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This is a past event.

Nickolay A. Krotkov
Baltimore, MD

The Ozone Monitoring Instrument (OMI) on NASA Aura satellite makes global daily measurements of the total column of sulfur dioxide (SO2), a short-lived trace gas produced by fossil fuel combustion, smelting, and volcanoes. This talk highlights most recent science results enabled by using OMI SO2 data. OMI daily contiguous volcanic SO2 data continue 25+ climatic record by its predecessors (Total Ozone mapping Spectrometers 1978-2005), but higher SO2 sensitivity allows measuring volcanic plumes for a longer time as well as measuring passive volcanic degassing from space. New algorithm development first allows direct estimating of SO2 plume heights to refine SO2 tonnages in largest volcanic plumes important for climate applications. Interplay between volcanic and anthropogenic SO2 emissions resulted in highly variable SO2 pollution levels in Peru and Mexico City. OMI first enabled daily detection of SO2 burdens from individual smelters as well as observed SO2 pollution lofting from boundary layer and long-range transport in free troposphere. We have updated our copper smelter analysis, which showed interesting new trends. Combining OMI data with trajectory models and aerosol/cloud measurements by A-train sensors (MODIS, CALIPSO) allowed tracking long-range transport of volcanic and anthropogenic aerosol/SO2 plumes. These studies placed new constraints on conversion rates of SO2 to sulfate at different heights from free troposphere to the lower stratosphere. New results on inverse trajectory modeling of the OMI SO2 data allow deriving information on the altitude distribution of SO2 and the emission time-series. Quantitatively, anthropogenic SO2 is more difficult to measure from space, since ozone absorption and Rayleigh scattering reduce sensitivity to pollutants in the lower troposphere. We describe new techniques for spatial and time averaging that have been used to determine the global distribution of anthropogenic SO2 burdens, and the efficacy of abatement strategies. OMI seasonal to multi-year average images clearly show the world-highest consistent SO2 pollution in eastern China. China is the world’s largest SO2 emitter, mostly due to the burning of high-sulfur coal in its many coal-fired power plants, which lack the technology used in many other countries to remove sulfur from smoke stack emissions. Recently, China’s government has instituted nationwide measures to control SO2 emissions through the adoption of flue-gas desulfurization technology on new power plants; and even greater measures were adopted in the Beijing area in anticipation of the Olympic Games. To study the environmental effects of the emission controls we compared OMI SO2 time series over eastern China for 2005 through 2009. By mid-March 2008 OMI first observed substantial periods of lower SO2 values compared to 2007, and by mid June the 2008 values were consistently lower than 2007 and prior years. The decline is widespread with highest SO2 typically located to the south and southwest of Beijing in regions with large clusters of power plants and also around Shanghai. The decline also lasted beyond the Olympic season through summer 2009. Combining model provided SO2 and aerosol vertical profile shapes allows refining satellite columns as well as estimating surface SO2 concentrations for air-quality applications. Finally we present our plans to use the OMI SO2 columns to provide a top-down constraint on SO2 regional emissions.

Host Simon Carn (


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