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Why is sandstorm called the natural enemy of spring?

Sandstorm is a natural phenomenon with great destructive power. Sandstorm, also known as sandstorm or dust storm, 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 1 km. When sandstorms appear, the yellow sand is rolling and the sky is dark, which is common in desert areas in winter and afternoon in dry and loose soil with long-term lack of rain. Meteorology refers to floating dust, sand blowing and sandstorm as dusty weather, and the difference between them is mainly based on visibility and wind power. Floating dust refers to sand or dust suspended in the atmosphere evenly, and its horizontal visibility is less than10 km; Sand blowing refers to blowing sand on the ground to make the air quite turbid, and the horizontal visibility is 1 ~ 10 km; When strong winds blow up dust on the ground and make the sky turbid, the horizontal visibility is less than 1 km, which is called sandstorm; When the horizontal visibility is less than 500m, it is defined as a strong sandstorm.

Modern scientific and technological research shows that the occurrence of sandstorms has a certain relationship with human activities, but the fundamental reason is natural factors. There are three main reasons: first, there are vast deserts in the north and northwest of China, and the northern region is rainy and dry, and the land is bare, which provides inexhaustible dust. Second, there is a Mongolian cyclone, which drags a lot of dust into the sky. Third, there is a cold air flow that carries the dust involved in the high altitude to a distance. These three conditions are indispensable, and it is difficult to form a large-scale sandstorm. In recent years, sandstorms frequently hit Beijing, seriously affecting people's lives. It is a manifestation of environmental deterioration, and it has also become a hot issue of public concern. In the rainy season of 2002, the precipitation in northern China was more than that in the previous year, and the vegetation coverage was better. In 2003, the sandstorm weather decreased obviously. 2002 was a year of frequent sandstorms in northern China, even affecting southern China and South Korea. Especially in 200 1 year, the drought became more serious, and Hebei, Tianjin, Inner Mongolia, Liaoning and other places suffered from severe drought, resulting in frequent sandstorms. When there is dusty weather, you should go out as much as possible to avoid inhaling too much polluted air in the case of serious pollution. If you go out, you should put on more clothes to avoid catching cold.

As early as in China's ancient history books, there were records about sand and dust phenomena, such as "Yellow wind came from the northwest, uprooted trees to build houses", "flying sand like rain", Song Zhenzong Tianxi four years (1020), "The sea was anchored in April, and the northwest wind blew, and the flying sand broke trees, and the sky fainted for several hours." People usually call it "sandstorm", "yellow wind" or "black storm". Dust weather not only exists in China, but also occurs in many countries in the world.

There are four high-risk areas of sandstorm in the world: Central Asia, North America, Central Africa and Australia. Northwest China is a part of the high incidence area of sandstorm in Central Asia, and the number of sandstorm days in many areas is more than 30 days every year. In 1930s, the "Black Storm" in the United States and Canada was a typical example. 1may, 934 12, the sandstorm is 2400 kilometers long from east to west and 400 kilometers wide from north to south, which almost swept two-thirds of the country. About 300 million tons of topsoil blew from the west coast to the northeast coast, resulting in a serious reduction in winter wheat production in the United States, which was 5.2 billion kilograms lower than that in the past 10. At that time, the "black storm" hit American agriculture hard, brought endless troubles to American society and people's lives, and the ecological environment suffered unprecedented serious damage.

Sandstorms are not without their merits. It carries a lot of dust that can inhibit acid rain in northern China, and also has a significant inhibitory effect on acid rain in South Korea and Japan.

At present, the preliminary project of Beijing sandstorm monitoring and early warning service system has been successfully implemented. Among them, solar photometers, aerosol monitors and other equipment will continuously record basic data such as particle size, mineral composition, chemical composition and occurrence intensity of dust. It can effectively monitor and accurately warn the harm and influence caused by sandstorm.