Distinct Effects of Winter Monsoon and Westerly Circulation on Dust Aerosol Transport over East Asia

The transport of dust aerosols in East Asia is affected by the East Asian winter monsoon (EAWM) and westerly circulation, which is one of the important reasons for the formation of the Loess Plateau in China. There are obvious seasonal changes in the intensity and impact range of EAWM and westerly jet , but their impact and relative contribution to East Asian dust transmission are still unclear. In this study, we use regional climate model to simulate the changes in the East Asian dust circulation for 20 years, and to assess the effects of EAWM and westerly jets on East Asian dust transport. The results show that the dust is transported at the upper level mainly by the west wind, while the lower layer is mainly transported by the EAWM. There is a clear seasonal interaction between the westerly circulation and the EAWM. In March, the westerly jet is located on the south side of the Tibet Plateau and has a large wind speed, so that the high-level dust aerosols is transmitted eastward to the north Pacific and beyond, with the shape of a strip. Low-level dust is transmitted to the southeast of China under the influence of EAWM. The control of dust by the westerly and EAWM is limited to the upper and lower layers respectively; in May, with the northward shift of the westerly jet, the control range of the westerly wind increases, the high-level transmission belt becomes wider, and the influence of the westerly jet on the high-level dust is weakened. The impact of the lower layers is enhanced. At the same time, due to the strengthening of the interaction between the westerly wind and the EAWM, both have effect on the middle-level dust transmission. The westerly wind and EAWM have different effects on different particle sizes dust. In the lower layer, fine-grained dust is transmitted far under the action of EAWM, and coarse-grained dust is limited to the vicinity of the source area. However, the influence of westerly wind on the transmission of different particle sizes dust is not much different.