A regional climate model （RegCM3）, coupled with an online dust module, is used to simulate the spatio-temporal distribution and emission flux of dust aerosol （smaller than 20 Wn in diameter） over East Asia in the period from 2000 to 2009. The model perfor- mance is firstly evaluated against available observations. Simulation results show that the model can capture the characteristics of spa- tio-temporal distribution of dust aerosol very well over East Asia. There always exist two extremes of dust aerosol optical depth （AOD） and column burden （CB）, one is in the Taklimakan Desert of Xinjiang Uygur Autonomous Region, China, and the other is in the Ba- dain Jaran Desert of Inner Mongolian Autonomous Region, China. The maximum value of CB appears in spring, secondary maxi- mum in winter and minimum in autumn. To the east of 110°E, dust is transported eastward from a maximum center at a height of 700 hPa over the East Asian continent. Dust emission sources are mainly located in the Taklimakan Desert, Badain Jaran Desert, North Qinghai-Tibetan Plateau and Southwest Mongolia. There is also an obvious seasonal variation of dust emission flux （EF）. Annual mean dust EF is 1,015.34 mg/（m2.d）, of which 62.4% and 2.3% are re-deposited onto the East Asian continent through a dry and wet deposition process, respectively, and the remaining 35.3% is injected into the atmosphere or subject to long-range transport.
The radiative forcing(RF) of Asian desert dust and its regional feedbacks to the East Asian summer monsoon(EASM) system are investigated with a coupled regional climate-desert dust model.The statistical significance of desert dust effects are analyzed through 20 summer seasons(1990-2009).In order to estimate the dust effects reasonably,some improvement has been achieved for the coupled model,including the updates of optical properties and desert source area distribution.We find that the desert dust can result in a roughly weakened monsoon in eastern China,Korean Peninsula,Japan and Indian Peninsula and a strengthened monsoon in Indochina Peninsula in the lower troposphere.Moreover,the precipitation comparisons between observational data and simulated patterns are also suggestive of the desert dust effect on the EASM.In the upper troposphere,the southward shift of the westerly jet(WJ) by the dust effect can be seen as an indicator of the weakened monsoon in great part of the monsoon areas.The change of the moist static energy(MSE) contrast between land and ocean is the main reason for the EASM variations.
