Mineral dust impacts on regional precipitation and summer circulation in East Asia using a regional coupled climate system model

摘要

The climatic impacts of dust on East Asian precipitation, summer monsoon, and sea surface temperature (SST) were investigated by a regional coupled atmosphere-ocean-land model. The regional and annual mean dust clear-sky (all-sky) direct radiative forcings were predicted to be -6.65Wm~(-2) (-1.78Wm~(-2)) at the surface and 3.79Wm~(-2) (8.65Wm~(-2)) at the top of atmosphere. The climatic effects of dust include a cooling effect below 700 hPa and a warming effect above, leading to more stabilized lower troposphere and anomalously cyclonic wind over Japan and surrounding oceans. Sensitivity tests showthat the "surface cooling" effect by dust could reduce evaporation over land and enhance stability of the lower atmosphere, leading to reduced vapor content and precipitation in China in the spring. However, the upward movements by the "elevated heat pump" effect of dust over northern China or by the atmospheric convergence over southern China, and the downward movement by the secondary circulation over central China, along with the enhanced evaporation and the weakened lapse rate over Chinese continent, lead to increased precipitation in downwind areas of dust source regions and southern China and to decreased precipitation in central China in summer. Results from this simulation also show that dust aerosol tends to weaken the East Asia summer monsoon by reducing the land-sea-temperature contrast. In addition, dust could also perturb SST by the local net heat flux rebalance as well as the northward heat transport from surrounding oceans. The anomalous northward surface wind contributes even larger on SST in June, July, and August.