SO2 Over China Detected With EOS Aura Ozone Monitoring Instrument

The Ozone Monitoring Instrument (OMI) on EOS/Aura offers unprecedented spatial and spectral resolution, coupled with global coverage, for space-based UV measurements of sulfur dioxide (SO2). Publicly released SO2 pollution data are processed with the Band Residual Difference (BRD) algorithm that uses calibrated residuals at SO2 absorption band centers produced by the NASA operational ozone algorithm (OMTO3). By using optimum wavelengths for retrieval of SO2, the retrieval sensitivity is improved over NASA predecessor Total Ozone Mapping Spectrometer (TOMS) by factors of 10 to 20, depending on location. The ground footprint of OMI is 8 times smaller than TOMS. These factors produce a two orders of magnitude improvement in the minimum detectable mass of SO2. The improved sensitivity now permits daily global measurement of heavy anthropogenic SO2 pollution. Anthropogenic SO2 emissions have been measured by OMI over known sources of air pollution, such as eastern China, Eastern Europe, and from individual copper smelters in South America and elsewhere. Here we present data from a case study conducted over Shenyang in NE China as part of EAST-AIRE in April 2005. SO2 observations from instrumented aircraft flights are compared with OMI SO2 maps. The OMI SO2 algorithm was improved to account for the known altitude profile of SO2, and the comparison demonstrates that this algorithm can distinguish between background SO2 conditions and heavy pollution on a daily basis. Between 5 and 7 April 2005 a cold front traveled from continental China, over Korea and on to the Sea of Japan. The satellite-derived measurements of SO2 confirm the in situ aircraft observations of high concentrations of SO2 (ca 4 DU) ahead of the front and lower concentrations behind it and provide evidence for a large-scale impact of pollutant emissions. The BRD algorithm sensitivity does not represent the maximum sensitivity theoretically achievable with OMI, and hence future improvements in instrument calibration and the algorithm should allow even weaker SO2 sources to be monitored routinely. Such measurements are essential given the growing concern over the effects of anthropogenically-forced climate change and intercontinental transport of air pollution.

http://www.knmi.nl/omi/research/product/so2/introduction.html