Why is there always a sandstorm in Xilinhot?

It is pointed out that the formation of sandstorm must meet four conditions: first, the dust material on the ground is the material basis for the formation of sandstorm; The second is strong wind, which is the dynamic basis of sandstorm formation and the dynamic guarantee of sandstorm long-distance transportation; Thirdly, the unstable air state is an important local thermal condition, and sandstorms often occur in the afternoon and evening, which shows the importance of local thermal conditions; Fourthly, in the arid climate, sandstorms mostly occur in northern spring, which is a good evidence that sandstorms will not occur for a period of time after rainfall. In the desert fringe in spring, due to long-term drought, there is little vegetation coverage on the surface, and when there is strong wind, the dust on the surface is easily blown up and transported away. However, due to the large particle size of sand, it is not easy to form suspension movement (suspension movement is a necessary condition for small particles to ensure long-distance transportation), so it can not be transported over a long distance, which is also the main reason why there is only dust and little sand blowing in areas far away from dust. If the gale lasts for a long time, the suspended floating dust can be transported far away, and sandstorms will appear in the passing areas; When the wind speed decreases to a certain extent, the floating dust will fall, and there will be dust-falling weather in the local area. If it rains at this time, the so-called "mud rain" will form. According to the four conditions required for the formation of sandstorms, the loess plateau, the vast desert and the land destroyed by human factors in the process of desertification, the land reclaimed in late spring in the north and the infrastructure under construction (such as expressway) provide sufficient material sources for the occurrence of sandstorms; In spring, the drought in the northern region increases the possibility of sandstorms.