Dust storms. Sandstorm

Dust (sand) storm- atmospheric phenomenon in the form of transport large quantities dust (soil particles, grains of sand) by the wind earth's surface in a layer several meters high with a significant deterioration in horizontal visibility. In this case, dust (sand) rises into the air and, at the same time, dust settles over a large area. Depending on the color of the soil in a given region, distant objects take on a grayish, yellowish or reddish tint. It usually occurs when the soil surface is dry and the wind speed is 10 m/s or more.

Often occurs during the warm season in desert and semi-desert regions. In addition to the “actual” dust storm, in some cases dust from deserts and semi-deserts can remain in the atmosphere for a long time and reach almost anywhere in the world in the form of dust haze.

Dust storms occur less frequently in steppe regions, very rarely in forest-steppe and even forest regions (in the last two zones, a dust storm occurs more often in the summer during severe drought). In steppe and (less often) forest-steppe regions, dust storms usually occur in early spring, after a winter with little snow and a dry autumn, but sometimes even in winter, in combination with blizzards.

When a certain threshold of wind speed is exceeded (depending on the mechanical composition of the soil and its moisture), particles of dust and sand come off the surface and are transported by saltation and suspension, causing soil erosion.

Criteria

In general (non-aviation) meteorology, it is believed that horizontal visibility during a dust storm (at a standard level of 2 m above the ground) is usually from 1 to 4 km (in some cases it can decrease to several hundred or even several tens of meters).

Geography

The main habitat of dust storms is deserts and semi-deserts of the temperate and tropical climatic zones of both hemispheres of the Earth.

Term dust storm Typically used when storms occur over clay and loamy soils. When storms occur in sandy deserts(especially in the Sahara, as well as in the Karakum, Kyzylkum, etc.), when in addition to small particles that reduce visibility, the wind also carries millions of tons of larger sand particles over the surface, the term is used sandstorm.

A high frequency of dust storms is observed in the Aral and Balkhash regions (southern Kazakhstan), on the coasts of the Caspian Sea, in the West Kazakhstan region, in Karakalpakstan and Turkmenistan. In Russia, dust storms are most often observed in the Astrakhan region, in the east of the Volgograd region, in Kalmykia, in Tyva, in the Altai region and in the Trans-Baikal region.

During long periods of dry weather, dust storms can develop (not annually) in the steppe and forest-steppe zones: in Russia - in the Chita region, Buryatia, Tuva, Novosibirsk, Omsk, Kurgan, Chelyabinsk, Orenburg regions, Bashkiria, Samara, Saratov, Voronezh, Rostov regions, Krasnodar, Stavropol Territories, Crimea; on the territory of Ukraine - in Lugansk, Donetsk, Nikolaev, Odessa and Kherson regions; in northern, central and eastern Kazakhstan.

Causes

With an increase in the strength of the wind flow passing over loose particles, the latter begin to vibrate and then “jump”. When these particles repeatedly strike the ground, they create fine dust that rises in suspension.

Recent research suggests that the initial saltation of sand grains by friction induces an electrostatic field. The bouncing particles acquire a negative charge, which releases even more particles. This process captures twice as many particles as previous theories predict.

Particles are released mainly due to dry soil and increased wind. Gust fronts can occur due to cooling air in the area of ​​a rainstorm or dry cold front. After the passage of a dry cold front, convective instability in the troposphere can contribute to the development of a dust storm. In desert regions, dust and sand storms most often occur as a result of thunderstorm downdrafts and the associated increase in wind speed. The vertical dimensions of a storm are determined by the stability of the atmosphere and the weight of the particles. In some cases, dust and sand storms may be confined to a relatively thin layer due to the temperature inversion effect.

Ways to fight

To prevent and reduce the effects of dust storms, it is necessary to analyze the terrain features - topography, microclimate, direction of prevailing winds, and carry out measures that help reduce wind speed at the surface and increase the adhesion of soil particles. To reduce wind speed, systems of forest belts and windbreaks are created. A significant effect for increasing the cohesion of soil particles is provided by leaving stubble, no-moldboard plowing, soil-protective crop rotations with crops of perennial grasses, strip alternation of perennial grasses and crops of annual crops.

Environmental consequences

Sandstorms can move entire dunes and carry enormous volumes of dust, so that the front of the storm can appear as a dense wall of dust up to 1.6 km high. Dust and sand storms coming from the Sahara Desert are also known as shamum, khamsin (in Egypt and Israel) and habub (in Sudan).

A large number of dust storms originate in the Sahara, especially in the Bodélé Depression and in the area where the borders of Mauritania, Mali and Algeria converge. Over the past half century (since the 1950s), Saharan dust storms have increased approximately 10-fold, causing a decrease in the thickness of topsoil in Niger, Chad, northern Nigeria and Burkina Faso. In the 1960s, there were only two dust storms in Mauritania, but currently there are 80 storms a year.

Dust from the Sahara is carried through Atlantic Ocean to the west. The intense daytime heating of the desert creates an unstable layer in the lower troposphere in which dust particles spread. As the air mass moves (advects) westward over the Sahara, it continues to heat up, and then, reaching the oceanic expanses, passes over a colder and wetter atmospheric layer. Such a temperature

Dust storm- a strong wind capable of transporting millions of tons of dust over a distance of several thousand kilometers.

This phenomenon, although meteorological, is associated with the state of the soil cover and the terrain. They akin to blizzards: for both to occur, a strong wind and sufficiently dry material on the surface of the earth is needed that can rise into the air and remain suspended there for a long time. But if for the appearance of blizzards you need dry, non-packed, snow-free snow lying on the surface and a wind speed of 7-10 m/s or more, then for the occurrence of dust storms the soil must be loose, dry, devoid of grass or any significant snow cover and wind speed was at least 15 m/s.

Depending on the structure and color of the soils blown by the wind, there are black storms(on chernozems), characteristic of Bashkiria, Orenburg region; brown or yellow storms(on loams and sandy loams), characteristic of Central Asia; red storms(on red-colored soils stained with iron oxides), characteristic of deserts and semi-deserts of our country, desert areas of Iran and Afghanistan); white storms(on salt marshes), characteristic of some regions of Turkmenistan, the Volga region, and Kalmykia.

A dust storm in its scale and consequences can be equated to a major natural disasters. V.V. Dokuchaev describes one of the cases of a dust storm in Ukraine in 1892: “Not only was the thin snow cover completely torn off and carried away from the fields, but also the loose soil, bare of snow and dry as ash, was thrown up by whirlwinds at 18 degrees below zero. Clouds of dark earthen dust filled the frosty air, covering roads, covering gardens in places the trees were carried to a height of 1.5 meters, lay down in shafts and mounds on the streets of villages and greatly impeded movement along railways: we even had to tear railway stops away from snowdrifts of black dust mixed with snow.”

During a dust storm in April 1928 in the steppe and forest-steppe regions of Ukraine, the wind lifted from the area 1 million km2 more than 15 million tons black soil Black earth dust was transported to the west and settled over an area of ​​6 million km2 in the Carpathian region, Romania and Poland. The height of dust clouds over Ukraine has reached 750 m. The thickness of the chernozem layer in the steppe regions of Ukraine after this storm decreased by 10-15 cm.

The danger of this phenomenon also lies in the terrible strength of the wind and its extraordinary impetuosity. During dust storms over Central Asia The air is sometimes saturated with dust up to a height of several kilometers. Aircraft caught in a dust storm are in danger of being destroyed in the air or upon impact with the ground; In addition, the visibility range in a dust storm can be reduced to tens of meters. There have been cases when during the day this phenomenon became as dark as night, and even electric lighting did not help. If we add that on earth, dust storms can lead to the destruction of buildings. windbreaks, not to mention the pervasive dust that fills houses, saturates people’s clothes, clouds their eyes, and makes breathing difficult, then it will become clear. how dangerous is this phenomenon and why is it called a natural disaster...

Dust storms usually last for several hours, but in some cases they last for several days. Some dust storms originate far beyond the borders of our country - in North Africa, on the Arabian Peninsula, from where air currents bring clouds of dust to us.

And here Hurricanes and dust storms are not on their way. Dust and sand storms in the Sahara can put an end to the activity of tropical hurricanes in the Atlantic. One of the places where these dangerous eddies originate is the ocean area adjacent to west coast Black continent. But as the results of a study conducted by a group of scientists from the University of Wisconsin-Madison show, it is precisely here that the eastern winds blowing from the depths of the continent carry clouds of Saharan sand dust.

Experts analyzed satellite images, made in 1982-2005. and compared them with tropical storm activity. As a result, scientists have established an inversely proportional relationship between these phenomena: in those years when strong sand whirlwinds were observed in Africa, tropical storms rarely occurred, and vice versa - when there were almost no storms, storms developed actively.

The anti-hurricane effect mechanism is simple. Firstly, the dusty-sandy substance is heavier than air, and falling down, it creates downward air currents that inhibit the development of a hurricane. Secondly, a powerful air flow blowing from the continent creates wind shear in the middle troposphere, which also contradicts the conditions for the formation of tropical vortices. And thirdly, particles of sand and dust suspended in the air absorb part of the latent thermal energy released during condensation of water vapor. Scientists believe that they are only at the beginning of a long research journey in this area.

Dust storm in Texas in 1935

Dust storm, South Dakota, 1937

Dust storm, Colorado, 1937