What is the cause of sandstorm?

A study by meteorologists shows that land desertification is not the chief culprit of sandstorm, so what is the main reason for the annual variation of sandstorm activity in northern China?

Dust weather is mainly the result of cold front and low pressure mass, and the decisive factor of its increase and decrease is the change of atmospheric circulation.

There seems to be a tendency to emphasize the impact of desertification on the environment in previous years, but since the 1980s, the frequency of strong and extra-strong sandstorms in northern China has obviously decreased. This phenomenon has been puzzling desert experts and meteorologists.

A few days ago, Zheng Qian An, a researcher at the Institute of Environment and Engineering in Cold and Arid Regions of Chinese Academy of Sciences, and a scholar from Taiwan Province conducted a cooperative study. The results show that the change of lower atmospheric circulation is the main factor for the formation and change of sandstorm weather, and the change trend of sandstorm activity in northern China is not completely consistent.

First of all, let me talk about the concept of atmospheric circulation. The atmosphere is what we call air every day, and human beings live at the bottom of this atmospheric "ocean". The atmosphere and seawater are both fluids, so there are many similarities between atmosphere and ocean phenomena. Just as there are two kinds of water masses in the ocean, namely, cold and warm water masses and their interfaces (i.e., cold and warm fronts) exist in the atmosphere, and the air flow also forms high and low pressure vortices (referred to as high and low pressure for short), high pressure ridges and low pressure troughs with different sizes and rotating directions.

Usually, high and low pressure systems appear together, and cold air is often brought behind the low pressure. A low pressure only affects a small range of weather, and the airflow system composed of several different high-low pressure and frontal systems will affect a wider range of weather changes. Atmospheric circulation is a large-scale airflow system consisting of several high-low pressure and frontal systems in a large area of the earth. Dust weather is mainly the result of cold front and low pressure mass.

The modern weather forecasting method is to collect the information of these high and low pressure vortices and fronts in time, and then estimate their development and changes according to the theory of atmospheric dynamics, so as to forecast the weather.

Since 1970s, global warming has weakened the sandstorm activities in western China and Mongolia, and the severe sandstorm weather in Beijing in 200 1 year was caused by the low pressure in Japanese sea area.

As far as sandstorm activities in China and Mongolia are concerned, due to their vast territory, they can be divided into at least three different flora: western flora, eastern flora and southwest flora.

Sandstorms in western China and Mongolia are mainly caused by the development of Mongolia low pressure and the southeast invasion of cold air on northwest road or north road. It mainly affects the central and western Inner Mongolia, Hexi Corridor and northern Xinjiang, and is the main system that affects sandstorm activities in China and Mongolia.

Sandstorms in eastern China and Mongolia are mainly caused by the development of low pressure near the Sea of Japan and the southward invasion of cold air from East Road or Northeast Road. It mainly affects eastern Mongolia, northern North China and South Korea.

Sandstorms in southwest China and Mongolia are often caused by the eastward invasion of cold air on the west road due to the development of low pressure in the southern Xinjiang basin. It mainly affects southern Xinjiang basin and Qaidam basin, but has little influence on eastern China.

Since 1950s and 1970s, the low pressure in Mongolia has been active and is still strengthening. Therefore, there are strong cold air activities, strong winds and sandstorms in western China and Mongolia. However, since the late 1970s, due to global warming, Mongolia is still the center of strong warming in winter and spring, and Mongolia's low pressure gradually weakens and turns to be controlled by high-pressure ridges. As a result, the cold air activity is weak in winter and spring. There are almost 16 warm winters in the north of China, and the sandstorm activity in the west has been weakening as a whole.

Statistics show that from 2000 to 2003, the number of large-scale sandstorms in China was 8, 10, 5 and 3 respectively. Especially in the spring of 2000 and 200 1 year, although Mongolia was still controlled by the ridge of high pressure, the Japanese sea turned into a low-pressure activity, so in recent years, it turned into a sandstorm activity in eastern China and Mongolia, which made Beijing suffer greatly. However, with the obvious weakening of the low pressure in the Sea of Japan in 2002, especially in the spring of 2003, the sandstorms in eastern China and Mongolia also weakened.