The wind and floating dust in Lanzhou cover the sky.

There will be some different weather in spring. It is understood that there were strong winds and floating dust in Lanzhou a few days ago, so what is the situation of strong winds and floating dust in Lanzhou? How are sandstorms formed? Next, let's take a look at this issue of urban culture!

The wind and floating dust in Lanzhou cover the sky.

Near the Zhongshan Railway Bridge in Lanzhou City, the wind covered the sky and was full of floating dust. The dusty weather swept through Lanzhou and its surrounding areas, and the whole city seemed to be covered with a gray cover. The whole sky is covered with a thick layer of dust, and the visibility is particularly low. It's also very scary.

Lanzhou Meteorological Observatory issued a blue gale warning signal on April 8 17: 07: It is estimated that within 24 hours, affected by strong winds, the average wind force in most parts of Lanzhou will reach 4-5, with gusts above 6 and gusts above 7 in the north; There may be a thunderstorm locally.

Reasons for the increase of sandstorms in Lanzhou

1. In recent years, the ecological environment in Gansu Province has deteriorated year by year, and the interaction between nature and human activities has intensified the harm of sandstorms.

2. The geographical location of Gansu Province is the main reason for the bad climate. The main source areas are Gurbantunggut Desert, Taklimakan Desert, Badain Jaran Desert, Tengger Desert, Wulanbuhe Desert and Mu Us Desert.

3. The sandstorm source areas in China mainly include the Su Nite Basin in eastern Inner Mongolia or the central and western parts of Hunshandake Sandy Land, the border area between China and Mongolia in Alashan League (Badain Jaran Desert), the Taklimakan Desert in southern Xinjiang and the Tonggut Desert in Kuban Banner in northern Xinjiang. This bad weather may last until the second day of May. Every March-May is a period of high incidence, and there is no way to stop it.

Causes of sandstorm formation

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

natural conditions

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.

The main component of soil and yellow sand is silicate. When there is less rain and the air temperature becomes warmer, the silicic acid on the silicate surface loses moisture, and H2SO4 = Si2O3+H2O (gas) = 1

In this way, the surface of silicate soil micelles and sand particles will be negatively charged and repel each other, becoming aerosols that cannot be aggregated together, thus forming sand blowing, that is, sandstorms. Sandstorms are essentially silicate aerosols with negative charges.

In short, the formation of sandstorms requires these three conditions:

One is the dust on the ground. It is the material basis for the formation of sandstorms.

The second is the strong wind. This is the dynamic basis for the formation of sandstorms and the dynamic guarantee for the long-distance transportation of sandstorms.

Third, the air state is unstable. This is an important local thermal condition. Sandstorms often occur in the afternoon and evening, which shows the importance of local thermal conditions.

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.