When did the sandstorm in Beijing start?

Every spring, usually in March, April and May.

definition

Sandstorm refers to the weather phenomenon that strong winds blow up dust on the ground, making the air very turbid and the horizontal visibility less than 1km. [2] Sandstorm is a weather phenomenon in wind erosion and desertification, and its formation is influenced by both natural factors and human activities. Natural factors include strong wind, decreased precipitation and its sand source. Human activity factor refers to the increase of sandstorm frequency after vegetation destruction in the process of economic development.

Sandstorm weather mainly occurs in winter and spring. This is because there is little precipitation in winter and spring in semi-arid and arid areas, the surface is extremely dry and loose, and the wind erosion resistance is very weak. When the wind blows, a lot of dust will be entrained in the air, forming sandstorm weather.

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 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.

Physical factors

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.

Preventive and control measures

1. Strengthen environmental protection and raise it to the height of legal system.

2. Restore vegetation, strengthen biological protection system and prevent sandstorms. Protect and restore forest and grass vegetation according to law, prevent further expansion of land desertification, and minimize dust sources.

3. According to the local conditions in different regions, formulate disaster prevention, disaster prevention and relief plans, actively promote various disaster reduction technologies, and build model projects, gradually promote them from point to area, and further improve the regional comprehensive defense system.

4. Control population growth, reduce the pressure of human factors on land and protect the environment.

5. Strengthen the popular science propaganda on the relationship between the occurrence and harm of sandstorms and human activities, and let people realize that once the living environment is destroyed, it will be difficult to recover, which will not only aggravate natural disasters such as sandstorms, but also form a vicious circle, and people should consciously protect their living environment.

6. Plant plants suitable for growing in desert arid areas, such as Hippophae rhamnoides, to form a ground cover plant layer, thus improving the ground cover environment, fixing the soil, reducing the wind speed, increasing the air humidity and improving the microclimate environment.

7. Planting native low shrubs and small trees on the edge of desert to improve vegetation distribution.

Personal protection point:

1. Close the doors and windows in time and seal them with tape when necessary.

2. Wear a mask when going out and cover your head with a scarf to avoid dust invading your eyes and respiratory tract. Special attention should be paid to traffic safety.

3. Motor vehicles and non-motor vehicles should slow down, pay close attention to road conditions and drive carefully.

4. Properly place outdoor items that are easily affected by sandstorms.