A Numerical Simulation Study on the Impacts of Dust Aerosol Direct Climatic Effects on the East Asian Winter Monsoon

Data of complex refractive index of East Asian dust and the latest vegetation distribution were used to update the default optical properties of dust aerosols and desert area in the regional climate-dust coupling model RegCM4-Dust. Then, the direct effect of dust aerosols on the East Asian winter monsoon (EAWM) was studied. The simulation results showed that the dust effects caused an enhancement of EAWM circulation in the lower troposphere in most of the EAWM area. In addition, the zonal wind was increased over mid-high latitudes and decreased over mid-low latitudes in the middle and upper troposphere. This can strengthen the meridional shear of zonal wind and favor the southward invasion of cold air, resulting in a strengthening EAWM. The dust effects also induced an obvious reduction of winter precipitation, which was in response to a strengthening EAWM, especially in the winter monsoon prevailing areas such as the southwestern part of northeastern China, North China, the Loess Plateau, and the middle and lower reaches of the Yangtze River, where the precipitation can decrease 10% or more. The increase in the temperature gradient between the East Asian subcontinent and the northwestern Pacific, which can enlarge the gradient of moist static energy (MSE), was the main reason for an enhancement of monsoon circulation when the dust effects were accounted for.