Characteristics and preventive measures of whistling sandstorm?

Sandstorm weather mainly occurs in late spring and early summer. This is because there is little precipitation in winter and spring in arid areas, the surface is unusually dry and loose, and the wind erosion resistance is very weak. When there is a strong wind blowing, a lot of dust will be involved in the air, forming sandstorm weather.

Terrible sandstorm weather

Globally, sandstorms mostly occur in inland desert areas, mainly the Sahara desert in Africa, and the midwest of North America and Australia are also one of the sources of sandstorms. From 1933 to 1937, the famous bowl-shaped sandstorm occurred in the midwest of North America due to severe drought. Asian sandstorm activity centers are mainly located in the Jordanian desert, Lower Mesopotamia between Baghdad and the northern coast of the Gulf, the southern Iranian coast near Abbas and the northern Afghan plain. Kazakhstan, Uzbekistan and Turkmenistan in Central Asia are all affected areas with frequent sandstorms (≥ 15/ year), but their centers are on the sandy plain between Caspian Sea and Aral Sea and Amu Darya River.

Due to its unique geographical environment, the northwest of China is also a region where sandstorms frequently occur. The main source areas are Gurbantunggut Desert, Taklimakan Desert, Badain Jaran Desert, Tengger Desert, Wulanbuhe Desert and Mu Us Desert.

From 1999 to the spring of 2002, there were 53 sandstorms in China (1999, 2000 14, 2006 18 and 2002 12). The analysis shows that: 2/3 of the dusty weather originated in southern Mongolia, and it was strengthened by the supplement of dusty materials when passing through northern China; The sand source in China is only about 1/3. The dusty weather in Central Asia (Kazakhstan) is unlikely to affect the eastern part of Northwest China or even North China. The Taklimakan Desert in southern Xinjiang is a high incidence area of sandstorm weather in China, but it generally does not affect the eastern part of northwest China and North China.

The dust weather path in China can be divided into northwest path, west path and north path:

Along the northwest route, dusty weather generally originates from the plateau in central and western Mongolia or Alashan Plateau in western Inner Mongolia, which mainly affects northwest and north China. The second route in the northwest, dust weather originated in southern Mongolia or central and western Inner Mongolia, mainly affecting the eastern part of the northwest, northern North China and most of the northeast; To the west, dusty weather originated in Gobi area in southwest or south Mongolia and desert area in western Inner Mongolia, mainly affecting northwest and north China. In the northerly route, dusty weather generally originates in the vast area south of Ulaanbaatar, Mongolia, and mainly affects the eastern part of northwest China, most of north China and southeast China.

Sandstorm weather causes (1) soil wind erosion.

Experts found through experiments that soil wind erosion is the primary link in the occurrence and development of sandstorms. Wind is the most direct driving force of soil, among which the nature of airflow, the magnitude of wind speed and the related conditions of wind action in soil wind erosion are the most important factors. In addition, soil water content is also one of the important reasons that affect soil wind erosion. Plant measures are one of the effective methods to prevent and control sandstorms. Experts believe that plants usually affect wind erosion in three forms: dispersing certain wind momentum on the ground, reducing the transmission between airflow and dust, and preventing the movement of soil and dust.

In addition, the occurrence of sandstorms is not only the product of specific natural environmental conditions, but also has a corresponding relationship with human activities. Man-made overgrazing, deforestation, industrial and mining traffic construction, especially man-made over-reclamation, destroyed the ground vegetation, disturbed the ground structure, formed a large area of sandy land, and directly accelerated the formation and development of sandstorms.

(2) Atmospheric circulation.

The brief scene of spring sandstorm in Beijing is just a weather process that has been experienced every year for two or three million years in the Loess Plateau in northern China, which stretches for about 300,000 square kilometers. The difference is that the wind of the latter is stronger and the wind lasts longer (it can last for several days). The source of sandstorm is not the crossroads 50 meters away, but the desert and Gobi hundreds of kilometers away.

It's like God is playing an incredible game: he grabs the dust on the surface of deserts and Gobi in northwest China and Central Asia and throws it to the southeast, leaving a highland where the dust falls. This game started about 2.4 million years ago, and God is still enjoying it (in 2002, Nature published the latest research results of China scholars, pushing the start time to 22 million years ago).

In fact, the wind is God's hand that throws sand.

After the Indian plate moved northward and collided with the Eurasian plate, the crust of the Indian continent was inserted under the crust of the Asian continent and propped up the latter, which made the shallow sea of the Himalayas disappear, the Himalayas began to form and gradually rise, and the Qinghai-Tibet Plateau also rose due to the extrusion of the Indian plate. After this process lasted more than 60 million years, by about 2.4 million years ago, the height of the Qinghai-Tibet Plateau had exceeded 2,000 meters.

The great change of surface morphology directly changed the pattern of atmospheric circulation. Before that, the Pacific Ocean was in the east of Chinese mainland, Siberia in the north and Himalaya in the south were occupied by shallow seas respectively, and the Mediterranean Sea in the west also extended to far places in Central Asia at that time, so most flat Chinese mainland could get enough moist air from the ocean, and the climate was warm and humid. Northwest China and Central Asia are mostly subtropical areas, and there are no large areas of deserts and Gobi.

However, the east-west Himalayan mountains stopped the warm and humid air mass in the Indian Ocean from moving northward. With the passage of time, the northwest of China has become more and more arid, gradually forming a large area of desert and Gobi. This is the birthplace of dust accumulated on the Loess Plateau. The huge Qinghai-Tibet Plateau just stands in the westerly belt of the northern hemisphere, and its height has been increasing for 2.4 million years. The width of the Qinghai-Tibet Plateau accounts for about 1/3 of the westerly belt, which divides the surface of the westerly belt into south and north branches. The south branch flows eastward along the south side of the Himalayas, and the north branch flows eastward from the northeast edge of the Qinghai-Tibet Plateau. This kind of high-altitude airflow exists at an altitude of 3500~7000 meters all the year round and becomes the main driving force to carry dust. At the same time, due to the uplift of the Qinghai-Tibet Plateau, the East Asian monsoon has also been strengthened. The winter wind blowing from northwest to southeast, together with westerly jet, formed the Loess Plateau in the north of China.

In the desert and Gobi in the northwest of China and the inland of Central Asia, the rocks here disintegrate into pieces faster than other places because of the drastic change of temperature. Geologists divide it into gravel (more than 2 mm), sand (2~0.05 mm), silt (0.05~0.005 mm) and clay (less than 0.005 mm) according to its diameter. Clay and sediment particles can be carried to an altitude of more than 3,500m, enter the westerly belt, be transported to the southeast by westerly jet, and gradually fall until the middle and lower reaches of the Yellow River.

For two or three million years, the process of transporting sand from northwest to southeast in this part of Asia has never stopped. A lot of sand falls in the area where the Loess Plateau is located, and even many mountains in North China, such as Wutai Mountain and Taihang Mountain, have loess accumulation at the top. Of course, the scouring effect of several large rivers and countless valleys in northern China, including the Yellow River, is just the opposite of the accumulation of loess. Otherwise, the loess plateau will not be like this, and the thickness will not exceed 409.93 meters. The North China Plain east of Taihang Mountain is also a subsidence area of sand, but it is a subsidence area, and at the same time many rivers have developed, so the falling sand is either washed away by the rivers or buried by the sediment brought by the rivers.

There are hundreds of records about rain soil, rain loess, rain yellow sand and rain haze in China ancient books. The earliest record of "rainy soil" can be traced back to 1 150 BC: the sky is yellow and foggy, and sand falls from the sky like rain. What is recorded here is actually a sandstorm.

The location of rainy soil is mainly in the Loess Plateau and its vicinity. The ancients regarded this kind of thing as a strange catastrophe phenomenon and thought it was a sign of "harmony between man and nature" It is recorded in the Natural History compiled by Zhang Hua in the Jin Dynasty: "When Xia Jie was in the deep valley, the night palace was mixed with men and women, and he did not go out to listen to politics for ten days. It was a windy day and filled the empty valley overnight. "

Hazards of sandstorm weather

The hazards of sandstorms are strong winds and dust. Its influence is mainly manifested in the following aspects:

Hazards of sandstorm weather (1) Soil wind erosion, vegetation destruction and farmland burial.

(2) air pollution. According to the monitoring network of the State Environmental Protection Administration, on March 20th, 2002, the amount of dustfall per square meter in Beijing reached 20g, and the total suspended particles reached 1 1000 μ g/m3, which was more than ten times the national standard and 100 times the normal value.

(3) Affect traffic. The impact of sandstorms on traffic is mainly manifested in the following aspects: First, the visibility is reduced, which affects driving and aircraft take-off and landing. For example, on March 22, 2002, seven airports in South Korea were forced to close, and on March 2 1 day, about 70 flights were forced to cancel. Second, sand and dust bury the roadbed and hinder traffic. According to China Business Daily, the train from Urumqi to Xi was blocked because the sandstorm buried part of the railway.

(4) affect the use and production of precision instruments.

(5) Harm to human health. Sandstorms do harm to health in many ways. Skin, eyes, nose and lungs are the first places to contact sandstorms and suffer the most. The damage of skin, eyes, nose, throat and other direct contact parts are mainly irritation symptoms and allergic reactions, while the lung manifestations are more serious and extensive. American health scientists have suggested that there is a link between fine pollution particles and lung disease and heart disease death. Australia's "Time" said that sandstorms caused by soil wind erosion are the chief culprit of asthma in 2 million people in the country.

(6) causing weather and climate changes. The impact of sandstorms not only affects some provinces in China, but also affects Korean and Japanese. 65438+1September 1998, a sandstorm originated in Kazakhstan, passed through a vast area in northern China, and transported a lot of dust to North America through high altitude; In April of 20001year, a strong sandstorm originated in Mongolia swept across the Pacific Ocean and the continental United States, and finally dissipated over the Atlantic Ocean. Such a large range of dust forms suspended particles in the sky, which is enough to affect the weather and climate. Because suspended particles can reflect solar radiation, thus reducing the atmospheric temperature. Because suspended particles greatly weaken the solar radiation (about 10%), the speed of the earth's water circulation may slow down and the precipitation will decrease; Suspended particles can also inhibit the formation of clouds, reduce the precipitation rate of clouds and reduce the water resources of the earth. It can be seen that dust may aggravate the drought.

(7) deterioration of ecological environment. 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.

Look at the following statistics, let us realize the urgency of preventing and controlling sandstorms:

China has 1500 km of railways, 30,000 km of highways and 50,000 km of irrigation canals damaged to varying degrees by sandstorms.

In recent years, the annual direct economic loss caused by sandstorms in China has reached 54 billion yuan, which is equivalent to three times the fiscal revenue of the five northwest provinces 1996.

Scientists have calculated that it will take more than 2,000 years to scrape off 18 cm thick topsoil on a grassland. For example, it takes 49 years to scrape off the same amount of topsoil on corn farmland; On bare ground, it only takes 18 years.

April to May is the high incidence period of sandstorms in northern China. Please pay close attention to the weather forecast and prepare for sandstorm prevention in advance.

Dust storm disaster prevention and emergency (1) Close the doors and windows in time, and seal the doors and windows with tape if necessary.

(2) Wear a mask when going out and wrap your head with a scarf to avoid dust invading your eyes and respiratory tract. Special attention should be paid to traffic safety.

(3) Motor vehicles and non-motor vehicles should slow down, pay close attention to road conditions and drive carefully.

(4) Properly arrange outdoor items that are easily damaged by sandstorms.

(5) It is not suitable to go out in strong sandstorm weather, especially for the elderly, children and patients with respiratory allergic diseases.

(6) Prepare for wind and sand prevention at ordinary times.