An investigation into seasonal and regional aerosol characteristics in East Asia using model- predicted and satellite-/sunphotometer-derived aerosol properties

In this study, the spatial and seasonal distributions of EOS/Terra Moderate Resolution Imaging Spectroradiometer (MODIS)-derived aerosol optical depth (AOD) over East Asia are analyzed in conjunction with US EPA Models-3/CMAQ v4.3 modeling. First, AOD (τM-BAERMODIS) retrieved through a modified Bremen Aerosol Retrieval Algorithm (M-BAER algorithm) is compared with AOD (τCMAQ) calculated from the US EPA Models-3/CMAQ model simulations. For the four season episodes selected in this study, both τM-BAERMODIS and τCMAQ show high values around Chinese urban and industrial centers, such as Sichuan Basins, Bohai Bay area, and Yangtze Delta areas, as well as excessively high NH3 emission regions. The levels of τCMAQ are also comparable to those of τM-BAERMODIS throughout the domain. Since τM-BAERMODIS 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 τM-BAERMODIS itself. Therefore, the seasonally and regionally varying aerosol formation characteristics are investigated by the US EPA Models- 3/CMAQ v4.3 model simulations. The contribution of each particulate chemical species to τM- BAERMODIS and τCMAQ shows strong seasonal variations. For example, during the summer episode, τM-BAERMODIS and τCMAQ are both raised due to high concentrations of (NH4)2SO4 over the Chinese urban and industrial centers, whereas during the winter episode, τM- BAERMODIS and τCMAQ are raised largely due to active NH4NO3 formation over urban and industrial centers, as well as over Chinese agricultural and livestock farming areas. On the other hand, τM- BAERMODIS is strongly correlated with the AOD (τAERONET) from the AERONET sites in East Asia, with an average correlation coefficient of R=0.77, thereby indicating the promising potential in the application of the M-BAER algorithm to air quality studies and satellite-based monitoring studies in East Asia.