Aerosol Optical Depth（AOD） is a key factor that reflects the impact of atmospheric aerosol on the climate. The accurate simulation of AOD is the basis for a climatic model in modeling the aerosol climate effects. In this study

an online-coupled three-dimensional regional climate–atmospheric chemistry–aerosol model was used to investigate the AOD over eastern China in 2010 to understand the spatial and seasonal behavior of AOD and the role aerosol plays over this region.The Regional Integrated Environmental Modeling System online-coupled with atmospheric chemistry and aerosol processes（RIEMS-Chem） was used in this study.This model contains sophisticated atmospheric dynamic

atmospheric chemical

and aerosol chemical processes. The onlinecoupled system facilitates the model to simulate the impact of aerosol on climatic factors and the feedback of climate on aerosol distribution.Simulated AOD was verified by satellite retrieval of the Moderate-Resolution Imaging Spectroradiometer（MODIS） and insitu measurements from the Aerosol Robotic Network（AERONET） in four seasons.The comparison of the AOD simulation result with the corresponding MODIS retrieval indicated the capability of the model to reproduce the seasonal variation and spatial distribution of AOD over eastern China

although the model somewhat underestimated the magnitude in summer.The comparison of AOD measurements from the six AERONET sites also showed that the model was able to simulate the spatial and seasonal variation of AOD

but underestimated the magnitude over north China

with an overall correlation coefficient of 0.6 compared with all AERONET measurements. The MODIS retrieval and corresponding simulation result showed that

over eastern China

the AOD was generally higher in summer

followed by spring

and lower in autumn and winter. However

the daytime seasonal mean AOD showed different seasonal distribution patterns:For areas around the North China Plain

the daytime seasonal mean AOD reached its highest level in summer with values ranging from 1.1 to 1.5

but lowest in other seasons. By contrast

over areas of the middle and lower reaches of the Yangtze River

the daytime seasonal mean AOD was reached its highest level in spring with values ranging from 1.1 to 1.7

followed by autumn and winter

but lowest in summer. For the region of eastern China

the daytime seasonal mean AOD reach edits highest level over areas north of the Yangtze River in summer

over areas south of the Yangtze River in winter

and over areas along the middle and lower reaches of the Yangtze River in spring and autumn.Model verification indicated that RIEMS-Chem was able to reflect the characteristics of AOD distribution and its seasonal variation

but under predicted the observation by approximately 20% in terms of the annual mean. According to the model result

the daytime AOD distribution exhibited distinct subregional and seasonal characteristics over eastern China

implying that

over this region

aerosol optical and climatic effects could be subregional and seasonal dependent.