Atmos. Chem. Phys. Discuss., 11, 21971-21993, 2011
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Up/Down trend in the MODIS Aerosol Optical Depth and its relationship to the Sulfur Dioxide Emission Changes in China during 2000 and 2010
S. Itahashi1, I. Uno2, K. Yumimoto3, H. Irie4, K. Osada5, K. Ogata6, H. Fukushima6, Z. Wang7, and T. Ohara8
1Department of Earth System Science and Technology, Kyushu University, Fukuoka, Japan
2Research Institute for Applied Mechanics, Kyushu University, Fukuoka, Japan
3Meteorological Research Institute, Tsukuba, Ibaraki, Japan
4Research Institute for Global Change, JAMSTEC, Yokohama, Japan
5Graduate School of Environmental Sciences, Nagoya University, Nagoya, Japan
6School of High-Technology for Human Welfare, Tokai University, Numazu, Japan
7Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
8National Institute for Environmental Studies, Tsukuba, Ibaraki, Japan

Abstract. Anthropogenic SO2 emissions increased alongside economic development in China at a rate of 12.7 % yr−1 from 2000 to 2005. However, under new Chinese government policy, SO2 emissions declined by 3.9 % yr−1 between 2005 and 2009. Between 2000 and 2010, we found that the variability in the fine-mode (submicron) aerosol optical depth (AOD) over the oceans adjacent to East Asia increased by 4–8 % yr−1 to a peak around 2005–2006 and subsequently decreased by 4–7 % yr−1, based on observations by the Moderate Resolution Imaging Spectroradiometer (MODIS) on board NASA's Terra satellite and simulations by a chemical transport model. This trend is consistent with ground-based observations of the number-size distribution of aerosol particles at a mountainous background observation site in central Japan. These fluctuations in SO2 emission intensity and AOD are thought to reflect the widespread installation of fuel-gas desulfurization (FGD) devices in power plants in China because aerosol sulfate is a major determinant of the AOD in East Asia. Using a chemical transport model, we confirmed that the above-mentioned fluctuation in AOD is mainly caused by changes in SO2 emission rather than by varying meteorological conditions in East Asia. High correlation was also found between satellite-retrieved SO2 vertical column density and bottom-up SO2 emissions, both of which were also consistent with observed AOD trends. We proposed a simplified approach for evaluating changes in SO2 emissions in China, combining the use of modeled sensitivity coefficients that describe the variation of AOD with changes in SO2 emissions and satellite retrieval. Satellite measurements of the AOD above Sea of Japan marked the 4.1 % yr−1 declining between 2007 and 2010, and this correspond to the SO2 emissions from China decreased by ~9 % yr−1 between the same period.

Citation: Itahashi, S., Uno, I., Yumimoto, K., Irie, H., Osada, K., Ogata, K., Fukushima, H., Wang, Z., and Ohara, T.: Up/Down trend in the MODIS Aerosol Optical Depth and its relationship to the Sulfur Dioxide Emission Changes in China during 2000 and 2010, Atmos. Chem. Phys. Discuss., 11, 21971-21993, doi:10.5194/acpd-11-21971-2011, 2011.
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