How are sandstorms formed?

Strong wind, strong thermal instability and sand source are the dynamic factors and material basis of sandstorm formation respectively.

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.

Extended data:

I. Morphological characteristics

1, the sand wall stands.

Most of the strong sandstorms on the mainland come from the northwest or west, and a few from the east. When almost all sandstorms come, we can see a black sand wall moving rapidly and getting closer and closer in the direction of the wind. Seen from a distance, the sandstorm wall is towering like a mountain, much like a city wall, and it is the sandstorm Depth Charge.

2. It is already dark.

When a strong sandstorm occurs, due to the strong wind of magnitude 8 or above, the wind is very strong and can roll up stones and sand. As more and more dust flies into the air, the thick dust is overwhelming, blocking the sun and making people see nothing for a period of time, just like at night.

3. Rolling and rushing

Black wind blows, the air near the ground is unstable, the heated air below rises, and the surrounding air flows to supplement, causing the air to roll up and down with a lot of dust, forming countless dust clouds of different sizes to meet and surge in the air.

Second, the main hazards

1, environmental pollution

When sandstorms occur, dust and floating dust carried by strong winds are everywhere, and the number of people passing through areas with air turbidity, choking nose and eyes, respiratory tract and other diseases increases. For example,1A serious sandstorm occurred in Jinchang on May 5, 993. The dust content in outdoor air is 10 16 mm/cm3, and the dust content in indoor air is 80 mm/cm3, which is 40 times higher than the national standard for dust content in living quarters.

2. Production and life are affected.

A lot of dust carried by sandstorm weather blocked the sun, and the weather was gloomy, which led to the decrease of solar radiation. A few hours to ten hours of poor visibility can easily make people feel depressed and reduce the efficiency of work and study. In light cases, a large number of livestock can be infected with respiratory and gastrointestinal diseases, and in severe cases, a large number of "spring-deficient" livestock will die, and fertile soil, seeds and seedlings in farmland will be scraped away.

Sandstorm will also aggravate the wind erosion and desertification of the surface soil, cover thick dust on the leaves of plants, affect normal photosynthesis and cause crop yield reduction. Sandstorms also caused the temperature to drop sharply. The sky is like a parasol, and the ground becomes dark and cold in the shadow.

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