Sandstorm. How do dust storms occur? Causes and effects of dust storms

Dust storm is a kind of dry wind, characterized by strong winds, carrying huge masses of soil and sand particles over long distances. dusty or sandstorms fall asleep agricultural land, buildings, structures, roads, etc. with a layer of dust and sand, reaching several tens of centimeters. At the same time, the area on which dust or sand falls can reach hundreds of thousands, and sometimes millions of square kilometers.

At the height of a dust storm, the air is so saturated with dust that visibility is limited to three to four meters. After such a storm, often where the shoots were green, the desert spreads. Sandstorms are not uncommon in the vast expanses of the Sahara, the world's greatest desert. Vast desert areas, where sandstorms also occur, are in Arabia, Iran, Central Asia, Australia, South America and in other parts of the world. Sandy dust, raised high into the air, makes it difficult for aircraft to fly, covers the decks of ships, houses and fields, roads, airfields with a thin layer. Falling on the water of the ocean, the dust sinks into its depths and is deposited on the ocean floor.

Dust storms not only raise huge masses of sand and dust into the troposphere - the most "restless" part of the atmosphere, where strong winds constantly blow at different heights (the upper limit of the troposphere in equatorial zone is located at altitudes of about 15–18 km, and in middle latitudes – 8–11 km). They move colossal masses of sand around the Earth, which can flow like water under the influence of the wind. Encountering small obstacles in its path, the sand forms majestic hills called dunes and dunes. They have a wide variety of shapes and heights. Dunes are known in the Sahara desert, the height of which reaches 200–300 m. These giant waves of sand actually move several hundred meters a year, slowly but steadily advancing on oases, filling up palm groves, wells, and settlements.

In Russia, the northern border of the distribution of dust storms passes through Saratov, Ufa, Orenburg and the foothills of Altai.

whirling storms are complex eddy formations caused by cyclonic activity and extending to large areas.

stream storms These are local phenomena of small distribution. They are peculiar, sharply isolated and inferior in their significance to eddy storms. whirling storms subdivided into dusty, dustless, snowy and squall (or squalls). Dust storms are characterized by the fact that the air flow of such storms is saturated with dust and sand (usually at a height of up to several hundred meters, sometimes up to 2 km in large dust storms). In dustless storms, due to the absence of dust, the air remains clean. Depending on the path of their movement, dustless storms can turn into dusty ones (when moving air flow, for example, over desert areas). In winter, whirlwinds often turn into snowstorms. In Russia, such storms are called blizzard, snowstorm, snowstorm.

The features of squall storms are rapid, almost sudden, formation, extremely short activity (several minutes), a quick end, and often a significant destructive force. For example, within 10 minutes the wind speed may increase from 3 m/s to 31 m/s.

stream storms divided into stock and jet. During katabatic storms, the air flow moves down the slope from top to bottom. Jet storms are characterized by the fact that the air flow moves horizontally or even up the slope. stock storms formed by the flow of air from the peaks and ridges of mountains down into the valley or to the seashore. Often in a given locality characteristic of them, they have their own local names (for example, Novorossiysk Bora, Balkhashskaya Bora, Sarma, Garmsil). jet storms characteristic of natural corridors, passages between chains of mountains connecting different valleys. They also often have their own local names (for example, Nord, Ulan, Santash, Ibe, Ursatievsky wind).

The transparency of the atmosphere largely depends on the percentage of aerosols in it (the concept of "aerosol" in this case includes dust, smoke, fog). An increase in the content of aerosols in the atmosphere reduces the amount coming to the Earth's surface solar energy. As a result, the Earth's surface may cool. And this will cause a decrease in the average planetary temperature and the possibility, ultimately, of the beginning of a new ice age.

The deterioration of the transparency of the atmosphere contributes to the interference with the movement of aviation, shipping and other modes of transport and is often the cause of major transport emergencies. Air pollution with dust harmful effect on living organisms and vegetable world, accelerates the destruction of metal structures, buildings, structures and has a number of other negative consequences.

Dust contains solid aerosols, which are formed during the weathering of the earth's rock, forest fires, volcanic eruptions and others natural phenomena; solid aerosols from industrial emissions and cosmic dust, as well as particles in the atmosphere formed during the crushing process during explosions.

By origin, dust is divided into space, marine, volcanic, ash and industrial. The constant amount of cosmic dust is less than 1% of the total dust content in the atmosphere. In the formation of dust of marine origin, the seas can participate only through the deposition of salts. In a noticeable form, this manifests itself occasionally and at a small distance from the coast. Dust of volcanic origin is one of the most significant air pollutants. fly ash It is formed due to the weathering of the earth's rock, as well as during dust storms.

industrial dust is one of the main constituents of air. Its content in the air is determined by the development of industry and transport and has a pronounced upward trend. Already now, in many cities of the world, a dangerous situation has been created due to the dustiness of the atmosphere due to industrial emissions.

Kurumy

Kurumy Outwardly, they are placers of coarse clastic material in the form of stone mantles and streams on mountain slopes with a steepness less than the angle of repose of coarse clastic material (from 3 to 35–40°). There are a lot of morphological varieties of kurums, which is connected with the nature of their formation. Their common feature is the nature of the packing of coarse clastic material - a fairly uniform size of the clasts. In addition, in most cases, from the surface, the debris is either covered with moss or lichen, or simply has a black “tan crust”. This indicates that the surface layer of debris is not prone to movement in the form of rolling. Hence, apparently, their name is “kurums”, which from the ancient Turkic means either “sheep herd”, or a cluster of stones similar in appearance to a flock of sheep. There are many synonyms for this term in the literature: stone stream, stone river, stone sea, etc.

The most important feature of the kurums is that their coarse clastic cover experiences slow movements down the slope. Signs indicating the mobility of the kurums are: the swell-like nature of the frontal part with the steepness of the ledge close to or equal to the angle of repose of the coarse clastic material; the presence of swells oriented both along the dip and along the strike of the slope; the sintering nature of the kurum body as a whole.

The activity of kurums is evidenced by:

– discontinuity of lichen and moss covers;

– a large number of boulders oriented vertically and the presence of linear zones with long axes oriented along the slope dip;

– large openness of the section, the presence of buried sod and remains of trees in the section;

– deformity of trees located in the zone of contact with kurums;

- plumes of fine earth at the base of the slopes, carried out from the kurum cover by subsurface runoff, etc.

In Russia, Kurums occupy very large areas in the Urals, in Eastern Siberia, in Transbaikalia, on Far East. Kurum formation is determined by climate, lithological features of rocks and the nature of the weathering crust, dissection of the relief and tectonic features of the territory.

The formation of kurums occurs in severe climatic conditions, the main of which is the amplitude of fluctuations in air temperatures, which contributes to the weathering of rocks. The second condition is the presence on the slopes of rocks that are resistant to disintegration, but
fissured, giving large pieces during weathering (lumps, crushed stone). The third condition is abundance precipitation, which form a powerful surface runoff that washes the coarse clastic cover.

The most active kurum formation occurs in the presence of permafrost. Their appearance is sometimes noted in conditions of deep seasonal freezing. The thickness of kurums depends on the depth of the seasonally thawed layer. On the Wrangel Islands, Novaya Zemlya, Severnaya Zemlya and in some other regions of the Arctic, kurums have a “filmlike” character of a coarse clastic cover (30–40 cm). In the North-East of Russia and the north of the Central Siberian Plateau, their thickness increases to 1 m or more, tending to increase to the south to 2–2.5 m in South Yakutia and Transbaikalia. In the same geological structures, the age of kurums depends on their latitudinal position. So, in the Northern and Polar Urals, modern kurum formation occurs, and in Southern Urals most of the kurums are classified as "dead", relic.

In continental regions, the most favorable conditions for kurum formation are found in areas with high humidity. AT temperate climate Intensive kurum formation occurs within the bald belt of mountains and the belt of forests. Each climatic zone has its own altitude ranges in which kurum formation is observed. AT Arctic zone Kurums are developed in the altitude range from 50–160 m on Franz Josef Land, to 400–450 m on Novaya Zemlya, and up to 700–1500 m in the north of the Central Siberian Plateau. In the Subarctic, the altitude range is 1000–1200 m in the Polar and Northern Urals, in the Khibiny. In the continental area temperate zone kurums are found at an altitude of 400–500 m in the southern part of the Central Siberian Plateau, 1100–1200 m in the west and 1200–1300 m in the east of the Aldan Highlands, 1800–2000 m in southwestern Transbaikalia. In the continental sector of the subboreal zone, kurums are found at altitudes of 600–2000 m in Kuznetsk Alatau and 1600–3500 m in Tuva. As a result of studying the kurums of Northern Transbaikalia, it was found that only in this region there are about 20 of their morphogenetic varieties (Table 2.49). The kurums differ from each other in terms of the shape in plan, the structure of the kurum body in the section, and the structure of the coarse clastic cover, which is associated with different conditions for the formation of kurums.

According to the sources of education, two large classes of kurums are distinguished. The first class includes tumuli, into which coarse clastic material enters from their bed due to its destruction by weathering, removal of fine earth, buckling of debris, and other processes. These are kurums with the so-called internal nutrition. The second class includes kurums, the clastic material of which comes from outside due to the action of gravitational processes (landslides, scree, etc.). Kurums of the second type are spatially localized in the lower parts or at the foot of actively developing slopes and are small in size.

Kurums with internal feeding are divided into two subgroups: those developing on loose deposits and on rocks. Kurums on slopes composed of loose deposits are formed as a result of cryogenic buckling of coarse clastic material and suffusion removal of fine earth from it. They are confined to moraines, deluvial-solifluction accumulations, sediments of ancient alluvial fans and other genetic varieties consisting of blocks, crushed stone with fine-grained aggregate. Often such kurums are laid along shallow erosional hollows and other superimposed exogenous forms.

The most widespread, especially in the goltsovy belt of mountains, are kurums with internal nutrition, developing on rocks of various origins and compositions, resistant to weathering and giving large pieces (blocks, crushed stone) when destroyed. The structure of all types of kurums is significantly influenced by the geological and geomorphological conditions in which they are formed (Table 2.50). On a relatively homogeneous in composition and structure of the primary substrate and slopes with the same slope, the kurum-forming processes manifest themselves relatively evenly over the area. In this case, a single-type section appears along its strike on the kurum slope. The structure and cryogenic features of the kurum cover change mainly down the slope. If the root substrate is heterogeneous in composition and structure, then the formation of the cover occurs unevenly over its entire area as a result of the selective manifestation of exogenous processes. In this case, kurums are formed various shapes(linear, mesh, isometric), belonging to the group of selective weathering of rocks.

The most important feature kurums, which predetermines their danger, is their structure in the context. It is the structure that determines their geodynamic and engineering-geological features, i.e., the danger of kurums when interacting with various engineering objects. The structure of kurums in sections is diverse. If we take into account the size of the fragments, the nature of their processing and sorting in a vertical section, the presence of bald ice or fine earth, its relationship with the part of the section that is in a permafrost state, and other dangers, then there are no similarly built kurums. However, when summarizing the details of the structure, 13 main types of sections were identified, which correspond to certain conditions of kurum formation and reflect the specifics of the processes occurring in one or another part of the coarse clastic material.

First group unites sections, in the structure of which there is a layer with bald ice. The part of the kurum body, which has such a structure, is named just that - a subfacies with bald ice. This subfacies is an indicator that the kurum is in the mature stage of its development, since the formation of the ice-ground layer occurs due to a decrease in the depth of seasonal thawing as a result of the destruction of rocks and an increase in their moisture content (ice content). The movement of the coarse clastic material of the subfacies is carried out due to thermogenic and cryogenic desertification, plastic deformations of the ice-ground base, as well as the sliding of fragments along it.

Dust (sand) storm - in the form of the transfer of large amounts of dust (soil particles, grains of sand) by wind from earth's surface in a layer with a height of several meters with a noticeable deterioration (usually at the level of 2 m it is from 1 to 9 km, but in some cases it can decrease to several hundred and even several tens of meters). At the same time, 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 hue. It usually occurs when the soil surface is dry and the wind speed is 10 m/s or more.

Often occurs in the warm season in and regions. When a certain threshold of wind speed is exceeded (depending on the mechanical composition of the soil and its moisture content), particles and are detached from the surface and are transported through and, causing soil erosion.

Dusty (sandy) drifting snow - the transfer of dust (soil particles, grains of sand) by wind from the earth's surface in a layer 0.5-2 m high, which does not lead to a noticeable deterioration in visibility (if there are no other atmospheric phenomena, horizontal visibility at a level of 2 m is 10 km or more ). It usually occurs when the soil surface is dry and the wind speed is 6-9 m/s or more.

Geography

The main distribution area of dust storms is and temperate and tropical climatic zones of both hemispheres of the Earth.

Desert and deserts are the main sources of airborne dust in the area , make a smaller contribution, and . Dust storms in China carry dust to . Ecologists believe that the irresponsible management of the arid regions of the Earth, such as ignoring the system, lead to and climate change at the local and global levels.

Term "sandstorm", usually used in the sense sandstorms, especially in the Sahara, when in addition to small particles that reduce visibility, the wind also carries millions of tons of larger sand particles above the surface. Term dust storm refers more to the phenomenon of the transport of small particles over distances of up to several thousand km, especially when storms "cover" urban areas.

A high frequency of dust storms is observed in and (south), on the coasts, in , in Karakalpakstan and Turkmenistan. In Russia, dust storms are most often observed in, in the east and in .

During long periods of dry weather, dust storms can develop (not annually) in the steppe and forest-steppe zones: in Russia - in, , Tove, , , , , regions, Bashkiria,, , , regions, and edge; on - in , , , , areas, in ; in northern, central and eastern .

At (before a thunderstorm and heavy rain) short-term (from several minutes to an hour) local dust storms can be observed in summer period even in points located in the forest vegetation zone - incl. in and (1-3 days per summer).

Causes

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

A recent study suggests that the initial grains of sand with the help of friction induces . Jumping particles acquire negative charge, which releases even more particles. Such a process captures twice as many particles as previous theories predict.Particles are released mainly due to and wind. Fronts of gusts of wind can appear due to cooling of the air after a strong with rain or may be dry . After the passage of a dry cold front instability can create a dust storm. In desert areas, dust and sandstorms are most often caused by thunderstorm outputs and increased wind speeds. The vertical dimensions of the storm are determined by the stability of the atmosphere and the weight of the particles. In some cases, dust and sandstorms can be limited to a relatively thin layer due to the effect of temperature inversion. In other cases, dust can rise to a height of 6100 m.

Ways to fight

To prevent and reduce the effects of dust storms, forest shelter belts, snow and water retention complexes are created, and agrotechnical methods are used, such as grass sowing, and contour plowing.

Environmental consequences

Sandstorms can move entire and transport huge volumes of dust, so that the storm front can look like a dense wall 1.6 km high. Dust and sand storms coming from the desert also known as, (in Egypt and ) and (in ).

Most dust storms originate in the Sahara, especially in the and in the area of convergence of boundaries, and . Over the past half century (since the 1950s), dust storms in the Sahara have increased by about 10 times, causing a decrease in the thickness of the topsoil in, Chad, northern and . In the 1960s, only two dust storms occurred in Mauritania, currently there are 80 storms per year. The amount of dust blown out of the Sahara towards the Atlantic Ocean in June five times more than a year ago, which could cool the waters of the Atlantic and reduce activity slightly .

Economic implications

The main damage caused by dust storms is the destruction of the fertile soil layer, which reduces its . In addition, the abrasive effect damages young plants. Other possible negative effects include: reduced affecting air and motor transport; a decrease in the amount of sunlight reaching the Earth's surface; the effect of a thermal "spread"; adverse effect on respiratory system living organisms.

Dust can also be of benefit in places of deposition - and receives most of its mineral fertilizers from the Sahara, replenishes the lack of iron in the ocean, dust on helps grow cultures. In northern China and the western United States, soils with deposits of ancient storms, called , are very fertile, but are also a source of modern dust storms when soil-binding vegetation is disrupted.

extraterrestrial dust storms

The strong difference in temperature between the ice sheet and the warm air at the edge of the south polar cap of Mars leads to emergence strong winds, which raise huge clouds of red-brown dust. Experts believe that dust on Mars can play the same function as clouds on Earth - it absorbs sunlight and heats the atmosphere due to this.

Dust (sand) storm - atmospheric phenomenon when 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 hue. It usually occurs when the soil surface is dry and the wind speed is 10 m/s or more.

Often occurs in the warm season in desert and semi-desert regions. In addition to the "proper" dust storm, in some cases, dust from deserts and semi-deserts can long time stay in the atmosphere and reach almost anywhere in the world in the form of a dusty haze.

Khartoum, Sudan, 2007

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

Khartoum, Sudan, 2007

The term dust storm is commonly used when a storm occurs over clay and loamy soil. 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 above the surface, the term sandstorm is used.

Al Assad, Iraq, 2005.

Al Assad, Iraq, 2007

Australia, 2010

Sandstorms can move entire dunes and carry huge amounts of dust, so that the front of the storm can appear as a dense wall of dust up to 1 mile high. Dust and sand storms coming from the Sahara desert are also known as samum, khamsin (in Egypt and Israel) and habub (in Sudan).

Phoenix, Arizona, USA, 2011

Phoenix, Arizona, USA, 2012

How do dust storms occur?

Dust storms are a phenomenon, although meteorological, but associated with the state of the soil cover and with the terrain. They are akin to blizzards: for the occurrence of both of them, a strong wind and sufficiently dry material on the surface of the earth are needed, capable of rising into the air and staying there in suspension for a long time. But if for the appearance of snowstorms you need dry, not caked, without crust, snow lying on the surface and a wind speed of 7-10 m / s or more, then for the occurrence of dust storms, it is necessary that the soil be loose, dry, devoid of grass or any significant snow cover and wind speed was not less than 15 m/s. Dust storms are observed most often in early spring, in March or April, after a dry autumn and a winter with little snow. They happen, although less often, in winter - in January or February, and very rarely - in other months of the year. The most typical synoptic setting for dust storms is the southern or southwestern periphery of a stable low-moving anticyclone, which causes dry weather with strong easterly or southeasterly winds.

Depending on the structure and color of the soils blown out by the wind, black storms (on chernozems) are distinguished, which are characteristic of the southern and southeastern regions of the European part of Russia, Bashkiria, and the 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 the deserts and semi-deserts of Central Asia (and also, outside our country, the desert areas of Iran and Afghanistan); white storms (on salt marshes), characteristic of some regions of Turkmenistan, the Volga region, Kalmykia.

Windblown dust can settle and accumulate in areas where the wind is weaker. In the south-west of Ukraine, in the middle reaches of the Don, between the rivers Khoprom and Medveditsa, there are places with dust deposits several meters or more thick. In snowless winters southeastern regions countries that are characterized by loose and dry soils, easily amenable to deflation (that is, wind erosion), with very strong and stable winds, winter black storms occur, blowing the soil along with winter crops that are not covered with snow. Such "black winters" were in 1892, 1949, 1951, 1960 and 1968.

TITLE: amazing world around us. Questions about the weather. Natural disasters related to the weather

HEADER: Why are dust storms dangerous?

SHEADER: Why are dust storms dangerous?

ANONCE: In terms of its scale and consequences, this phenomenon can be equated to major natural disasters

DESCRIPTION: This phenomenon, in its scale and consequences, can be equated to major natural disasters

KEYWORDS: weather, meteorology, question, advice, recommendation, history, fact, element, disaster, whim, winter, spring, summer, autumn, region, continent, forecast, dusty, storm, natural, disaster, cloud, fog, dust

AUTHORS: P. D. Astapenko

Why are dust storms dangerous?

This phenomenon in its scope and consequences can be equated to major natural disasters. V.V. Dokuchaev describes one of the cases of a dust storm in Ukraine in 1892 in the following way: “Not only was a thin snow cover completely torn off and carried away from the fields, but also loose soil, bare from snow and dry as ash, was thrown up in whirlwinds at 18 degrees of frost. Clouds of dark earthen dust filled the frosty air, covering the roads, bringing gardens - in some places the trees were brought to a height of 1.5 meters - laid down in shafts and mounds on the streets of the villages and made it very difficult to move along railways: I even had to tear off the railway stations from the 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 more than 15 million tons of black soil from an area of 1 million km2. Chernozem dust was transported to the west and settled on an area of 6 million km in the Carpathian region, in Romania and in Poland. The height of dust clouds over Ukraine 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 force of the wind and its extraordinary impetuousness. 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 on impact with the ground; in addition, the visibility range in a dust storm can be reduced to tens of meters. There were cases when during the day with this phenomenon it became dark as at night, and even electric lighting did not help. If we add that dust storms on earth can lead to the destruction of buildings, windbreaks, not to mention the all-penetrating dust that fills houses, soaks people’s clothes, covers their eyes, makes it difficult to breathe, then it becomes clear how dangerous this phenomenon is and why it is called natural disaster...

Dust storms usually last for several hours, but in some cases - 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 dust clouds to us.

Dust (sand) storm- an atmospheric phenomenon in the form of the transfer of large amounts of dust (soil particles, grains of sand) by wind from the earth's surface in a layer several meters high with a noticeable deterioration in horizontal visibility (usually at a level of 2 m it ranges from 1 to 9 km, but in some cases it can drop to several hundred and even up to several tens of meters). At the same time, 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 hue. It usually occurs when the soil surface is dry and the wind speed is 10 m/s or more.

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

dust haze- an atmospheric phenomenon, a continuous more or less uniform clouding of the atmosphere with a horizontal visibility range of 2 m from 1 to 9 km (sometimes visibility is reduced to several hundred or even several tens of meters) due to dust and soil particles suspended in the air.
It can be observed before or after a dust storm (when the wind weakens), as well as during a distant dust storm, when dust particles raised into the air are carried by the wind over a long distance. At the same time, in the visible vicinity there are no signs of dust being lifted by the wind from the surface of the earth. Depending on the color of the soil in a given region, distant objects take on a grayish, yellowish, or reddish hue.
Dusty haze should not be confused with a dust storm.

Less often, dust storms occur in the steppe regions, very rarely - in the forest-steppe and even forest regions (in the last two zones, a dust storm usually occurs in summer with severe drought). AT temperate zone usually dust storms occur in early spring, after a winter with little snow and a dry autumn, but sometimes they occur even in winter, in combination with snowstorms.

The main distribution area of dust storms is deserts and semi-deserts of the temperate and tropical climatic zones of both hemispheres of the Earth.
The term dust storm is commonly used when a storm occurs over clay and loamy soil. When storms occur in sandy deserts (especially in the Sahara, as well as in the Karakum, Kyzyl Kum, etc.), when, in addition to small particles that reduce visibility, the wind also carries millions of tons of larger sand particles above the surface, the term sandstorm is used.
In Russia, dust storms are most often observed in Astrakhan region, in the east Volgograd region and in Kalmykia.
During a squall (before a thunderstorm and heavy rain), short-term (from several minutes to an hour) local dust storms can be observed in the summer even at points located in the forest vegetation zone - including Moscow and St. summer).
The Sahara desert and the deserts of the Arabian Peninsula are the main sources of dust haze in the Arabian Sea region, Iran, Pakistan and India make a smaller contribution. Dust storms in China carry dust to Pacific Ocean.

Causes

A recent study 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. Such a process captures twice as many particles as previous theories predict.
Particles are released mainly due to the dryness of the soil and increased wind. Fronts of gusts of wind can appear due to cooling of the air in the zone of a thunderstorm with rain or a dry cold front. After the passage of a dry cold front, the convective instability of the troposphere can contribute to the development of a dust storm. In desert regions, dust and sandstorms are most often caused by thunderstorm downdrafts and the associated increase in wind speed. The vertical dimensions of the storm are determined by the stability of the atmosphere and the weight of the particles. In some cases, dust and sandstorms can be limited to a relatively thin layer due to the effect of temperature inversion.

Known dust and sandstorms

Dust storm in Australia (September 2009)
- According to Herodotus, in 525 BC. e. during a sandstorm in the Sahara, the fifty-thousandth army of the Persian king Cambyses perished.
- In April 1928, in the steppe and forest-steppe regions of Ukraine, the wind lifted more than 15 million tons of black soil from an area of 1 million km². Chernozem dust was transported to the west and settled on an area of 6 million km² in the Carpathian region, in Romania and in Poland. The height of dust clouds reached 750 m, the thickness of the black earth layer in the affected regions of Ukraine decreased by 10-15 cm.
- A series of dust storms across the United States and Canada during the Dust Bowl Period (1930-1936) forced hundreds of thousands of farmers to move.
- In the afternoon of February 8, 1983, a severe dust storm that appeared in the north of the Australian state of Victoria covered the city of Melbourne.
- During the periods of multi-year droughts in the years 1954-56, 1976-78 and 1987-91 in the territory North America intense dust storms.
- A strong dust storm on February 24, 2007, which appeared on the territory of western Texas near the city of Amarillo, covered the entire northern part of the state. Strong wind caused numerous damage to fences, roofs and even some buildings. The international airport of the Dallas-Fort Worth metropolis was also badly damaged, people with breathing problems went to the hospital.
- In June 2007, a large dust storm occurred in Karachi and in the provinces of Sindh and Balochistan that followed heavy rains led to the death of almost 200 people.
- On May 26, 2008, a sandstorm in Mongolia resulted in the death of 46 people.
- On 23 September 2009, a dust storm in Sydney disrupted traffic and forced hundreds of people to stay at home. Over 200 people sought medical attention due to breathing problems.
- July 5, 2011 a huge sandstorm covered the city of Phoenix, the capital of Arizona in the United States. The elements led to breaks in power lines, a fire in the city center, and air traffic was paralyzed.

In particular, I would like to note a historical event called dusty cauldron.
Dust Bowl, Dust Bowl - a series of catastrophic dust storms that occurred in the prairies of the United States and Canada between 1930 and 1936 (in some regions until 1940). Caused by a combination of anthropogenic (extensive management Agriculture, soil degradation) and natural (drought) factors. Dusty Cauldron - one of the most nightmarish episodes American history XX century. In the thirties, a severe economic crisis. And suddenly another misfortune was added to it: terrible dust storms attacked the country, because of which it was very bad.

The term "Dust Bowl" was first used on April 15, 1935 by Associated Press reporter Robert Geiger. It is assumed that it comes from the image of the Great Plains, created by William Gilpin: "fertile bowl, rimmed by mountains" (a fertile bowl (cauldron) surrounded by mountains). The term is used to refer not only to the time of the dust storms of the 1930s, but also to the region that became their center: the western third of Kansas, southern Colorado, the protruding parts of Texas and Oklahoma, and northern New Mexico.
In 1932, 14 dust storms were recorded, in 1933 - 38. The strongest storms took place in May 1934 and April 1935. Huge masses of soil were blown away by winds that met no obstacles in the devoid of natural vegetation and plowed prairies, and were transported in the form of black clouds over long distances - up to the Atlantic Ocean. April 14, 1935, due to the fact that clouds of dust obscured the sunlight, was called Black Sunday. In the winter of 1934-1935, snow fell in New England, red with dust. Among the population of the prairies, especially in Kansas and Oklahoma, dusty pneumonia has become widespread.
By 1934, about 40 million hectares of soils had partially or completely lost their upper humus horizon as a result of wind erosion. By 1935, up to 80% of the area of the High Plains was eroded to one degree or another. By 1938, in Llano Estacado, about 10% of the soils had lost more than 12 cm of the upper horizon, another 13.5% - from 6 to 12 cm.

For many decades, scientists have tried to understand the cause of this phenomenon. In general, the views of experts converge, but there have always been many incomprehensible details.

Causes of the Dusty Kettle

The development of the Great Plains began only in the second half of the 19th century, after the adoption of the Homestead Act and the development of the railway network. The main occupation of the settlers was originally animal husbandry, but by 1890, due to overgrazing, there was a transition to agriculture. New wave resettlement and a sharp increase in the area of arable land occurs after the First World War, when grain prices rose.
Agriculture of that time developed extensively. Crop rotations were not used, and no anti-erosion measures were taken. Moreover, farmers typically burned the stubble and left the field empty for the winter (the period of the most intense winds). As a result, the soils dried up, their structure was destroyed, dehumidified, and their erosion resistance decreased. The 1930s turned out to be relatively dry, which played a significant role in the development of dust storms.