When there is dusty weather in Beijing in spring, what wind direction is dominant? A very specific one. Fifty words. Thank you. Start (a disease)

There are three main sand sources affecting Beijing: Mu Us and Kubuqi Desert, Wulanbuhe Sandy Land and Hunshandake Sandy Land. The first path is Shandake Sandy Land in Inner Mongolia-Heihe River Basin in Hebei-Beijing area; The second path is Zhu Rihe in Inner Mongolia-Yanghe River Basin in Hebei-Yongding River Basin in Beijing; The third path is the Sanggan River Basin in Hebei Province-Yongding River Basin in Beijing. Beijing is located in the northeast of North China, at the southern foot of Yanshan Mountain and east of Taihang Mountain. Mainly composed of loess and sandy land, there is no large area of desert. The desert in northwest China is dominated by sand, which is not the source of dust. Moreover, there is a "Yanshan Taihang" mountain range as a barrier in North China, and the desert is not a concern. What's more, the dust structure in Beijing is very different from the sandy structure in the northwest desert. So the first route seems to have little effect on this. [