Spatial and seasonal variations of MODIS aerosol optical depth in East China during 2000-2012

This study compares the aerosol optical depth (AOD) at 0.55 um derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the National Aeronautics and Space Administration (NASA) Terra satellite with the Level 2.0 AOD (Quality Assured) from the Aerosol Robotic Network (AERONET) at four different locations over East China, including Hefei, Shouxian, Taihu, and Hangzhou-ZFU. The evaluation results indicate that most MODIS data from all sites fall into the expected error ranges (± 0.05 ± 0.15), with over a 66% probability that the NASA design requirements have been met. The Taihu station is an exception, accounting for only 41% of expected errors due to its lake area location and tendency to underestimate surface reflectance, thereby increasing the AOD values. Overall, the MODIS data show a good consistency and thus, are applicable for this analysis over the study area. The MODIS/Terra derived AOD at 0.55 um from 2000 to 2012 are used to analyze the spatio-temporal variation of AOD in East China. Results indicate that AODs are significantly affected by the topographic distribution. The AODs are relativity low over mountainous areas and high over plains and basins. Human activities also have a certain impact on the distribution of AOD. In addition, AODs exhibit clear seasonal variations; generally high in spring and summer, but low in autumn and winter. Combined with Ångström exponent, aerosol particles are mainly coarse in spring and winter, but fine during summer and autumn.