A study of dust radiative feedback on dust cycle and meteorology over East Asia by a coupled regional climate-chemistry-aerosol model

摘要

An online coupled regional climate-chemistry-aerosol model was utilized to investigate the dust direct radiative feedbacks on dust deflation, transport and meteorological elements in March 2010, when a severe dust storm originated from the Gobi desert near the China-Mongolia border swept across most areas of East Asia during the period of 19-22 March. The predicted meteorology and aerosol concentration agree generally well with observations, and it clearly shows that the predictions of both dust concentration and meteorological elements with dust radiative feedback are closer to observation than that without feedback, suggesting the superiority of on-line coupled model in chemical and climate predictions. The direct radiative forcing by dust aerosol caused significant reductions in ground temperature and wind speed in dust deflation region, with maximums up to -7 ℃ and -4.0 m s~(-1), respectively. The reduced wind speed and increased atmospheric stability resulted in smaller dust emission and weakened vertical diffusion, and consequently less dust aerosol in upper levels transported further downwind. While the shortwave radiative forcing dominated over longwave forcing in the daytime, leading to decreases of surface air temperature and wind speed, in the nighttime, the warming effect of longwave forcing dominated, causing increases of air temperature and wind speed up to 1 ℃ and 1 m s~(-1), respectively, in the dust deflation region. The variation of meteorology during the dust storm period at a rural site (Yuzhong) downwind of the Gobi desert exhibited an evident decrease in surface air temperature due to the dust radiative forcing. In terms of monthly mean, the dust radiative forcing caused a surface cooling of -0.6 to -1.0 ℃ over wide areas from west China to northern parts of east China and the Korean peninsula, with maximums in the middle reaches of the Yellow River and portions of northeast China. Concurrently, precipitation decreased by 0.1-0.6 mm day~(-1) in the middle reaches of the Yangtze River and large areas of north China, and alternating bands of increasing and decreasing precipitation (~1 mm day~(-1)) occurred in south China.