What are the causes of sandstorm?

The formation of sandstorms must meet four conditions: first, the dust on the ground is the material basis for the formation of sandstorms; Second, strong wind is the dynamic basis for the formation of sandstorms and the dynamic guarantee for the long-distance transportation of sandstorms; Third, the unstable air state is an important local thermal condition, and sandstorms mostly occur in the afternoon and evening, which shows the importance of local thermal conditions; The fourth is the arid climate environment. Sandstorms mostly occur in spring in the north, and it is a good proof that sandstorms will not occur for a period of time after rainfall. In the edge area of desert in spring, due to long-term drought and little vegetation cover on the surface, when there is strong wind, the dust on the surface is easily blown up and transported. However, due to the large particle size of sand, it is not easy to form suspended movement (suspended movement is a necessary condition for small particles to ensure long-distance transportation), so it cannot be transported over a long distance, which is the main reason why there is only dust falling and little sand blowing in areas far away from dust. If the wind lasts for a long time, the suspended floating dust can be transported to a long distance, 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 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 in the process of desertification destroyed by human factors, the land cultivated at the end of spring in the north and the infrastructure under construction (such as highways) provide sufficient material sources for the occurrence of sandstorms; However, the drought in northern China in spring increases the possibility of sandstorms, which shows that sandstorms are the result of many complex factors. The destruction of nature by human activities has intensified land desertification and played an extremely important role in sandstorms. In recent years, abnormal weather phenomena such as global drought have also played an inestimable role in sandstorms.