A paper on sandstorms.

Sandstorm is directly related to the unreasonable development in arid and desertification areas.

Based on the investigation of the current situation of ecological environment in the birthplace of sandstorm, the causes and harm of sandstorm are explored, which lays the foundation for exploring more scientific and reasonable measures to prevent sandstorm.

Scientists went deep into deserts, Gobi and oases, and made on-the-spot investigations in areas where desertification has intensified in recent years, the ecology has deteriorated sharply, and sandstorms have occurred frequently, and in the source areas of sandstorms. The whole journey is more than 7,000 kilometers, and a lot of first-hand information has been collected, which provides valuable information for controlling sandstorms in northern China.

The investigation shows that the frequent occurrence of sandstorms in the 1990s is directly related to the unreasonable development and utilization of human beings in arid and desertification areas, and the excessive "demand" of human beings for the environment is one of the main reasons for the frequent occurrence of sandstorms.

1. What is a sandstorm?

Sandstorm is a general term for sandstorm and sandstorm, which refers to the weather phenomenon that strong winds drag a large amount of dust on the ground into the air, making the air particularly turbid and the horizontal visibility lower than 1 km, in which sandstorm refers to a sand-laden storm formed by strong winds blowing a large amount of dust near the ground; Sandstorm is a storm formed by strong winds, which brings a lot of dust and other particles into the sky. Generally, wind speed and visibility are used to classify the intensity grade of sandstorm. At present, the intensity of sandstorm is divided into four levels: level 4 ≤ wind.

Speed ≤ 6,500 m ≤ visibility ≤ 1000m, which is called weak sandstorm; Grade 6 ≤ wind speed ≤ 8,200 meters ≤ visibility ≤500 meters, which is called medium-intensity sandstorm; The wind speed is ≥9 and the visibility is ≤200 meters, which is called a strong sandstorm. When it reaches its maximum intensity (instantaneous maximum wind speed ≥ 25m/s, visibility ≤ 50m, or even reduced to 0m), it is called extremely strong sandstorm (or black storm, commonly known as? Black Wind). ?

The second is the temporal and spatial distribution of sandstorms.

There are four sandstorm-prone areas in the world, which are located in Central Asia, North America, Central Africa and Australia. The sandstorm area in China is a part of the sandstorm in Central Asia, which mainly occurs in the northern region. The general characteristics are that the northwest is more than the northeast, the plains or basins are more than the mountains, and the deserts and edges are more than other areas. Mainly concentrated in two major areas: First, the Taklimakan Desert in Tarim Basin. The other is from the eastern part of Badain Jaran Desert to the Hexi Corridor in Gansu Province in the south, passing through Wulanbuhe in Tengger Desert to Kubuqi Sandy Land and Mu Us Sandy Land. In addition, there are three local sandstorm areas in Karamay area of northern Xinjiang, Hotan area of southern Xinjiang and northwest Qinghai. According to research, as early as the end of Cretaceous (70 million years ago), there was dust. According to local records, there was a strong sandstorm in Wuwei, Gansu Province in 35 1 year, which caused houses to collapse and human and animal casualties. In the long geological history, sandstorms show periodic changes, which are related to the climate change in geological period and the amount of ground dust. When the climate is warm and humid, the ground vegetation grows densely, the ecological environment conditions are good, and the frequency of sandstorms is low. On the contrary, in the cold and dry climate period, the frequency of sandstorms is higher. The change characteristics of sandstorms in northwest China in the past half century are as follows: (1) the sandstorms occurred most frequently in the 1950 s; In the early 1960s, it dropped slightly, and in the late 1960s, it dropped to the lowest level. After that, it increased slightly in the 1970s, gradually decreased in the 1980s and increased significantly in the 1990s. The seasonal and monthly variation characteristics of sandstorms in China are as follows: spring is the most, accounting for about half of the total annual amount, followed by summer and autumn (winter in Xinjiang) is the least; By month, the frequency is the highest in April, followed by March and May, and the lowest in September (65438+February or 65438+ 10 in Xinjiang). In addition, sandstorms also have obvious diurnal variation characteristics, mainly in the afternoon and evening.

Third, how is the sandstorm formed?

Relevant research points out that the formation of sandstorms must meet four conditions: first, the dust on the ground is the material basis for the formation of sandstorms; The second is strong wind, which is the dynamic basis of sandstorm formation and the dynamic guarantee of sandstorm long-distance transportation; Thirdly, the unstable air state is an important local thermal condition, and sandstorms often occur in the afternoon and evening, which shows the importance of local thermal conditions; Fourthly, in the arid climate, sandstorms mostly occur in northern spring, which is a good evidence that sandstorms will not occur for a period of time after rainfall. In the desert fringe in spring, due to long-term drought, there is little vegetation coverage on the surface, and when there is strong wind, the dust on the surface is easily blown up and transported away. However, due to the large particle size of sand, it is not easy to form suspension movement (suspension movement is a necessary condition for small particles to ensure long-distance transportation), so it can not be transported over a long distance, which is also the main reason why there is only dust and little sand blowing in areas far away from dust. If the gale lasts for a long time, the suspended floating dust can be transported far away, and sandstorms will appear in the passing areas; When the wind speed decreases to a certain extent, the floating dust will fall, and there will be dust-falling weather in the local area. If it rains at this time, the so-called "mud rain" will form.

According to the four conditions required for the formation of sandstorms, the loess plateau, the vast desert and the land destroyed by human factors in the process of desertification, the land reclaimed in late spring in the north and the infrastructure under construction (such as roads) provide sufficient material sources for the occurrence of sandstorms; In spring, the drought in the northern region increases the possibility of sandstorms; The generation of gale is a complex atmospheric phenomenon, which is mainly the result of cold front activity or the adjustment of latitude and longitude circulation. It can be seen that the occurrence of sandstorm is the result of the joint action of many complex factors. The destruction of nature by human activities leads to the intensification of land desertification, which plays an extremely important role in the occurrence of sandstorms. In recent years, global drought and other abnormal weather phenomena have also played an inestimable role in the occurrence of sandstorms. Therefore, human activities only play a certain role in the production of sandstorms, and it cannot be said that sandstorms are caused by human factors.

Fourth, the harm of sandstorms.

Sandstorm, especially extremely strong sandstorm, is a kind of disastrous weather with great harm. When it is formed, it will roll forward in the form of an avalanche. Where the strong airflow carrying gravel passes, after sand burial, strong wind attack, cooling frost and air pollution, a large area of farmland will be buried by sand or blown away by living fertile soil, or crops will be harmed by frost; As a result, some crops failed to harvest, while others greatly reduced production; It can aggravate land desertification, cause serious pollution to the atmospheric environment, cause great damage to the ecological environment, have an important impact on infrastructure such as transportation and power supply lines, and cause serious losses to people's lives and property. China is seriously endangered by sandstorms, especially the facilities such as mining, transportation and emerging towns in the northwest, such as water conservancy, electric power, coal fields and oil and gas wells, are all endangered or threatened by sandstorms. Once there is a sandstorm or black storm, the harm is particularly serious. On May 5, 1993, a particularly strong sandstorm caused direct economic losses of 5.6 billion yuan. The total area affected by this extremely strong sandstorm is about 165438+ 10,000 square kilometers, involving 72 counties and banners in four northwest provinces 18 city, and more than 20,000 people18 city. According to statistics, in this catastrophe, 85 people were killed, 3/kloc-0 people were missing and 264 people were injured. Hundreds of thousands of livestock were killed and lost, and hundreds of thousands of hectares of farmland, fruit forests and young forests were affected. Hundreds of plastic greenhouses were destroyed, and the infrastructure, power supply lines, roads and railways of grasslands, pastures and salt fields were seriously damaged. In addition, the damage of sandstorm to the ecological environment in northwest China has greatly accelerated the process of land desertification in this area, and its indirect losses are immeasurable. In addition, dustfall will pollute the city's atmosphere and directly affect people's health.

Verb (abbreviation for verb) How should we deal with sandstorms?

1. Establish a sandstorm forecasting system.

The task of controlling sandstorms is arduous and arduous, and many problems have not been fully understood (such as the exact location of the material source of each sandstorm), and human ability to control nature is extremely limited, so it is impossible to control sandstorms overnight. Moreover, sandstorms, especially when the black storm comes, are fierce, the wind is howling, the dust is all over the sky, and the sense of terror is great, which can easily cause casualties and loss of life and property. Therefore, it is particularly important for us to establish an accurate sandstorm forecasting system. Accurate forecast before the sandstorm, do disaster prevention work in advance, such as strengthening the protection of children, avoiding dangerous houses to prevent wall collapse and hurting people, protecting livestock, and cutting off power supply in time to prevent fires. , can reduce the loss to a minimum.

2. Strengthen environmental governance and protection.

The destruction of the environment has played a great role in the occurrence of sandstorms, so it is particularly important to strengthen environmental governance to alleviate or reduce sandstorms. Combined with the strategy of developing the western region, from 2000, the state will build "Ten Major Projects" in the western region, among which returning farmland to forests (grasslands) and ecological construction in the central and western regions are one. This will play a very important role in curbing sandstorms. It is particularly important to find a more accurate material source through scientific research and focus on controlling the source of sandstorms.