How is a small sandstorm formed?

The weather situation favorable to strong winds or strong winds, favorable distribution of dust sources and favorable air instability conditions are the main reasons for the formation of sandstorms or strong sandstorms. Strong wind is the driving force of sandstorm, and the source of sandstorm is the material basis of sandstorm. Unstable thermal conditions are conducive to the increase of wind power and the development of strong convection, thus carrying more dust and winding it higher. In addition, drought and lack of rain in the early stage, warming weather and rising temperature are the special weather and climate background for the formation of sandstorms; The convective cells before the ground cold front develop into clouds or squall lines, which is a small and medium-sized system conducive to the development and strengthening of sandstorms. The topographic condition conducive to the increase of wind speed, that is, the narrow tube effect, is one of the favorable conditions for the formation of sandstorms. Under the favorable conditions of large-scale environment, high-altitude dry and cold jet, strong vertical wind speed, wind direction shear and thermal instability stratification, the generation and development of small and medium-scale systems near the front area intensified the pressure and temperature gradient before and after the front area, forming a huge pressure and temperature gradient before and after the front area. Under the joint action of momentum downward transfer and gradient deviation wind, the wind speed in the near-surface layer rises sharply, causing dust on the surface and forming sandstorm or strong sandstorm weather.

Man-made causes of sandstorm:

The ecological environment in arid and semi-arid areas is also very fragile, and its vegetation is easily destroyed and difficult to restore. In addition, there are human activities, such as deforestation and overgrazing, which cause the continuous expansion of land desertification and provide the main soil and sandy materials for dusty weather.

Dust weather is divided into four categories: floating dust, sand blowing, sandstorm and strong sandstorm. The specific criteria are:

(1) The standard of floating dust is the weather phenomenon that dust and fine sand float evenly in the air, so that the horizontal visibility is less than 10 km;

(2) The standard of sand blowing is the weather phenomenon that the wind blows up the dust on the ground, making the air quite turbid and the horizontal visibility is within 1 km to1km; The definitions of floating dust weather process and sand blowing weather process are as follows: in the same weather process, floating dust weather occurs in more than five countries in China's weather forecast area at the same observation time;

(3) The standard of sandstorm is the weather phenomenon that strong wind blows up a lot of dust on the ground, which makes the air very turbid and the horizontal visibility is less than 1 km;

(4) Strong sandstorm refers to the weather when strong winds blow up dust on the ground, making the air very turbid and the horizontal visibility is less than 500 meters.