ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-8-6627-2008 An investigation into seasonal and regional aerosol characteristics in East Asia using model-predicted and remotely-sensed aerosol properties Song C. H. 1 6 Park M. E. 1 Lee K. H. 1 3 Ahn H. J. 1 Lee Y. 1 Kim J. Y. 2 Han K. M. 1 Kim J. 4 Ghim Y. S. 5 Kim Y. J. 1 Dept. of Environmental Science and Engineering, Gwangju Institute of Science and Technology (GIST), Gwangju, Korea Hazardous Substance Research Center, Korea Institute of Science and Technology (KIST), Seoul, Korea Earth System Science Interdisciplinary Center (ESSIC), University of Maryland, MD 20742, USA Department of Atmospheric Science, Yonsei University, Seoul, Korea Department of Environmental Science, Hankuk University of Foreign Studies, Yongin-si, Gyeonggi-do, Korea also at: Advanced Environmental Monitoring Research Center (ADEMRC), Gwangju Institute of Science and Technology (GIST), Gwangju, Korea 17 11 2008 8 22 6627 6654 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/8/6627/2008/acp-8-6627-2008.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/8/6627/2008/acp-8-6627-2008.pdf

In this study, the spatio-temporal and seasonal distributions of EOS/Terra Moderate Resolution Imaging Spectroradiometer (MODIS)-derived aerosol optical depth (AOD) over East Asia were analyzed in conjunction with US EPA Models-3/CMAQ v4.3 modeling. In this study, two MODIS AOD products (&tau;<sub>MODIS</sub>: &tau;<sub>M-BAER</sub> and &tau;<sub>NASA</sub>) retrieved through a modified Bremen Aerosol Retrieval (M-BAER) algorithm and NASA collection 5 (C005) algorithm were compared with the AOD (&tau;<sub>CMAQ</sub>) that was calculated from the US EPA Models-3/CMAQ model simulations. In general, the CMAQ-predicted AOD values captured the spatial and temporal variations of the two MODIS AOD products over East Asia reasonably well. Since &tau;<sub>MODIS</sub> cannot provide information on the aerosol chemical composition in the atmosphere, different aerosol formation characteristics in different regions and different seasons in East Asia cannot be described or identified by &tau;<sub>MODIS</sub> itself. Therefore, the seasonally and regionally varying aerosol formation and distribution characteristics were investigated by the US EPA Models-3/CMAQ v4.3 model simulations. The contribution of each particulate chemical species to &tau;<sub>MODIS</sub> and &tau;<sub>CMAQ</sub> showed strong spatial, temporal and seasonal variations. For example, during the summer episode, &tau;<sub>MODIS</sub> and &tau;<sub>CMAQ</sub> were mainly raised due to high concentrations of (NH<sub>4</sub>)<sub>2</sub>SO<sub>4</sub> over Chinese urban and industrial centers and secondary organic aerosols (SOAs) over the southern parts of China, whereas during the late fall and winter episodes, &tau;<sub>MODIS</sub> and &tau;<sub>CMAQ</sub> were higher due largely to high levels of NH<sub>4</sub>NO<sub>3</sub> formed over the urban and industrial centers, as well as in areas with high NH<sub>3</sub> emissions. &tau;<sub>CMAQ</sub> was in general larger than &tau;<sub>MODIS</sub> during the year, except for spring. The high biases (&tau;<sub>CMAQ</sub>&gt;&tau;<sub>MODIS</sub>) may be due to the excessive formation of both (NH<sub>4</sub>)<sub>2</sub>SO<sub>4</sub> (summer episode) and NH<sub>4</sub>NO<sub>3</sub> (fall and winter episodes) over China, possibly from the use of overestimated values for NH<sub>3</sub> emissions in the CMAQ modeling. According to CMAQ modeling, particulate NH<sub>4</sub>NO<sub>3</sub> made a 14% (summer) to 54% (winter) contribution to &sigma;<sub>ext</sub> and &tau;<sub>CMAQ</sub>. Therefore, the importance of NH<sub>4</sub>NO<sub>3</sub> in estimating τ should not be ignored, particularly in studies of the East Asian air quality. In addition, the accuracy of &tau;<sub>M-BAER</sub> and &tau;<sub>NASA</sub> was evaluated by a comparison with the AOD (&tau;<sub>AERONET</sub>) from the AERONET sites in East Asia. Both &tau;<sub>M-BAER</sub> and &tau;<sub>NASA</sub> showed a strong correlation with &tau;<sub>AERONET</sub> around the 1:1 line (<I>R</I>=0.79), indicating promising potential for the application of both the M-BAER and NASA aerosol retrieval algorithms to satellite-based air quality monitoring studies in East Asia.

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