divination 

Samoom is a sandstorm. Dust storm Where do dust storms occur?

Sandstorm- view from the plane

Dust (sand) storm- an atmospheric phenomenon in the form of the transfer of large amounts of dust (soil particles, grains of sand) by the 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.

Less often, dust storms occur in steppe regions, very rarely - in forest-steppe and even forest regions (in the last two zones, a dust storm occurs more often in summer with 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.

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

Dusty (sandy) drifting snow - the transfer of dust (soil particles, grains of sand) by the 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 and more ). It usually occurs when the soil surface is dry and the wind speed is 6-9 m / s or more.

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 saltation of sand grains by friction induces electrostatic field . Jumping 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 the 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, convective instability in the troposphere can contribute to the development of a dust storm. In desert regions, dust and sandstorms are most commonly caused by thunderstorm downdrafts and the associated increase in 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.


Sandstorm in Australia

Ways to fight

To prevent and reduce the effects of dust storms, field-protective forest belts, snow and water retention complexes are created, and agrotechnical practices such as grass seeding , crop rotation and contour plowing .


Environmental consequences

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 1.6 km high. Dust and sand storms coming from the Sahara Desert are also known as samum, khamsin (in Egypt and Israel) and habub (in Sudan).

A large number of dust storms originate in the Sahara, especially in the Bodele depression and in the area where the borders of Mauritania, Mali and Algeria converge. 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 Niger, Chad, northern Nigeria and Burkina Faso. In the 1960s, only two dust storms occurred in Mauritania, currently there are 80 storms per year.

Dust from the Sahara is transported across the Atlantic Ocean to the west. Strong daytime heating of the desert creates an unstable layer in the lower part of the troposphere, in which spread dust particles. As the air mass transfers (advection) to the west over the Sahara, it continues to heat up, and then, having entered the ocean, passes over a colder and wetter atmospheric layer. This temperature inversion keeps the layers from mixing and allows the dusty layer of air to cross the ocean. The volume of dust blown out of the Sahara towards the Atlantic Ocean in June 2007 is five times greater than a year earlier, which could cool the waters of the Atlantic and slightly reduce hurricane activity.


Economic consequences

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

Dust can also be beneficial in places of deposition - the rainforest of Central and South America receives most of the mineral fertilizers from the Sahara, the lack of iron in the ocean is replenished, the dust in Hawaii helps banana crops grow. In northern China and the western United States, ancient storm sediment soils, called loess, are very fertile, but are also the source of modern dust storms when the 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 Mars' south polar cap results in strong winds that kick up huge clouds of red-brown dust. Experts believe that dust on Mars can play the same role as clouds on Earth - it absorbs sunlight and heats the atmosphere due to this.

Known dust and sandstorms

Dust storm in Australia (September 2009)

  • According to Herodotus, in 525 BC e . killed in a sandstorm in the Sahara fifty-thousandth army of the Persian king Cambyses.
  • In April 1928, in the steppe and forest-steppe regions of Ukraine, the wind raised 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 chernozem layer in the affected regions of Ukraine decreased by 10-15 cm.
  • A series of dust storms in the United States and Canada during the Dust Bowl period (1930-1936) forced the hundreds thousand farmers.
  • In second half days 8 February 1983 of the year the strongest dusty storm, emerging on the north Australian state Victoria, covered city Melbourne.
  • AT periods multi-year droughts years 1954 —56 , 1976 —78 and 1987 —91 on the territory Northern America arose intense dusty storms.
  • strong dusty storm 24 February 2007 of the year, emerging on the territory western Texas in area cities Amarillo, covered all northern part state. Strong wind caused numerous damage fences, roofs and even some buildings. Also strongly Suffered international the airport metropolis Dallas-Fort—Worth, in hospital applied people with problems at breathing.
  • AT June 2007 of the year big dusty storm happened in Karachi and on the territory provinces Sindh and Balochistan, subsequent behind her strong rains led to of death almost 200 Human .
  • 26 May 2008 of the year sandy storm in Mongolia led to of death 46 Human.
  • 23 September 2009 of the year dusty storm in Sydney led to interruptions in movement transport and forced hundreds Human stay Houses. Over 200 Human turned behind medical help from—behind problems with breath.
  • 5 July 2011 of the year huge sandy storm covered

Huge, swirling reddish clouds of sand and dust, raised from the surface of the earth by dry, hot and fast air currents, carry death. So, in 1805, a dust storm completely covered a caravan of two thousand people and the same number of camels with sand. The same story befell the Sahara in 525 BC. legendary army Persian ruler Cambyses II: a terrible sandstorm stopped the military expedition halfway, killing about fifty thousand soldiers.

A sure sign that a sandstorm is approaching is a sudden silence when the wind stops blowing, and with it all sounds and rustles disappear. Instead, stuffiness intensifies, and along with it, anxiety emerges at a subconscious level. And after a while, a fast-growing black-purple cloud appears on the horizon. The wind appears again and, picking up speed, raises dust and sand.

A sandstorm, or as it is also called, a dust storm is a atmospheric phenomenon when a strong wind moves a huge amount of grains of sand, soil particles or dust over long distances. The height of such a cloud can exceed a kilometer, while the visibility inside it decreases to several tens of meters.

As these particles settle, the ground becomes reddish, yellowish or greyish (depending on the composition of the airborne particles). Despite the fact that dust storms appear mainly in summer, in the absence of precipitation and rapid drying of the soil, they also occur in winter.

Dust storms form mainly in desert or semi-desert regions (the Sahara desert is especially famous for them), but sometimes due to drought it can also occur in the forest-steppe and forest regions of the planet. So, in April 2015, Khmelnytsky, a city located in western Ukraine, was hit by a sandstorm. The hurricane lasted about five minutes, visibility did not exceed ten meters, and the wind was so strong that it almost carried people and vehicles off the bridges.

How a storm is formed

In order for a dust storm to arise, a dry ground surface and a wind speed exceeding 10 m / s are required (for example, in the Sahara, its rates often reach 50 m / s). Dust storms appear due to the turbulence (heterogeneity) of air flows, which, when moving over an uneven surface, collide with obstacles, form air turbulences. The faster the wind moves, the more dangerous eddies it creates.

After the movement increases air masses above loose soil particles, the adhesion between which is weakened due to the dryness of the soil (which is why storms of this type appear mainly in deserts), the grains of sand begin to vibrate, then jump, and as a result of repeated impacts turn into fine dust.

Air swirls easily lift sand or dust particles from the ground, while the temperature of the lower layers of air masses rises greatly: over the steppes - up to 1.5 km, over deserts - up to 2.5 km. After that, air is mixed with dust particles, which tend to be distributed over the entire area of ​​the heated air.

Whereas smaller particles earth's surface fly extremely high, large ones rise to a lower distance and fall quickly (if the wind is extremely strong, the dust can be transported thousands of kilometers). The strength of the wind during sandstorms is such that it is quite capable of moving the dunes, and the sand raised by it will be like a huge cloud one and a half kilometers high.

In order for a dust storm to form, the soil must be dry: in the event of a prolonged drought, under the influence of strong winds, even particles of the upper layers of chernozem soil can rise into the air (in this case, a “black storm” is formed), and move long distances.

So, at the end of the twenties of the last century in the forest-steppe and steppe forests of Ukraine, a dust storm suddenly appeared, lifted up more than 15 million tons of black soil (the height of the cloud was 750 m) and moved them thousands of kilometers to the side. Some of the dust settled in the Carpathians, Poland and Romania, as a result of which the fertile soil layer in the affected regions (about 1 million km2) decreased by 10-15 cm.

How long does the event last

Sandstorms typically last between thirty minutes and four hours. At the same time, short-term dust storms are characterized by a slight deterioration in visibility: the terrain is visible up to four, and sometimes up to 10 kilometers.

Among short-term dust storms, there are also such dust storms during which visibility is limited to two tens of meters.

A dust storm always appears almost unexpectedly: in good weather, a heavy wind will rise, as a result of which the speed of air flows increases, picking up and lifting dust particles into the air.

True, poor visibility does not last long, even though the wind speed is increasing at this time. You can tell that a dust storm is approaching by the gray foggy veil that appears under cumulonimbus clouds when they are close to the horizon.

There are also long sandstorms:

  • Some dust storms are characterized by only a partial deterioration in visibility, up to four kilometers (however, these dust storms are the longest in time, since they can last several days).
  • Others are characterized by limited visibility to a few meters on initial stage development, after which it clears up to one kilometer. But these sandstorms last no more than four hours.


Storms of the Sahara

Many sandstorms originate in the world's largest desert, the Sahara, where Mauritania, Mali and Algeria border each other. Over the past half century, the number of sandstorms in the Sahara has increased tenfold (about eighty storms sweep through Mauritania alone in a year).

The uplifted sand of the Sahara is so abundant that a huge amount of sand particles are transported through Atlantic Ocean. This situation is possible due to the fact that when dust and sand move over the desert, they continue to heat up along with the air, after which, once above the ocean, they pass under a colder and more humid air flow. The difference in temperature between the layers of air causes them to not mix with each other, allowing dusty warm air to cross the ocean.

Although sandstorms cause many negative consequences(destroy the fertile soil layer, adversely affect respiratory system living organisms), the dust raised into the air also brings benefits. For example, dust storms in the Sahara supply humid equatorial forests Central and South America huge amount mineral fertilizers, and the ocean receives the missing part of the iron. At the same time, the dust raised in Hawaii makes it possible for banana trees to grow.

What to do if caught in a storm

Having noticed the first signs of an approaching storm, you must immediately stop: it is useless to continue moving and extra waste forces, especially since a sandstorm rarely lasts more than four hours. Even if the wind does not subside for about two or three days, it is better to wait in one place and not go anywhere. Therefore, all supplies of water and food must be kept near you (especially water, otherwise complete dehydration of the body is ensured, and this always leads to death).

Stopping, you need to immediately start looking for shelter. It can be a large stone, a boulder, a tree near which you need to lie down on the leeward side and completely, with your head, wrap yourself in matter. If it is possible to hide in a car, it must be placed in such a way that the wind does not blow through the door.

In the worst case, if there is no shelter nearby, you need to lie on the ground and cover your head with clothes (the Bedouins in such cases dig something like a trench). It should be borne in mind that when a sandstorm passes, the air temperature at that moment will be about fifty degrees, which can lead to loss of consciousness. Breathe while tons of sand are sweeping over your head, you only need to use a handkerchief, otherwise the smallest particles will enter the respiratory tract.

How do dust storms occur?

Dust storms are a phenomenon, although meteorological, but associated with the state soil cover and with the terrain. They are akin to snowstorms: for the occurrence of both of them, a strong wind is needed and enough dry material on the surface of the earth that can rise into the air and long time be there in balance. 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 most common 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, inactive anticyclone, which causes dry weather with strong easterly or southeast winds weather.

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 in the southeastern regions of the country, which are characterized by loose and dry soils, easily amenable to deflation (that is, wind erosion), with very strong and steady winds winter black storms arise, blowing out 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: 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 railway stations 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 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.

A 500 km long dust cloud has already reached Sydney, causing flight delays. Poor visibility is also observed in other parts of New South Wales.

It will be noted that the state has been experiencing a drought since August - strong winds raise dry soil, which caused the formation of a dust storm.

Local residents are urged to stay in enclosed spaces, "especially children, the elderly, and those with breathing problems." According to doctors, dozens of people have already asked for help with complaints of breathing problems. The number of victims due to the elements is still unknown.

Residents of Sydney were warned about the danger a few hours ago, when a dust storm with a front of about 500 km began to approach the city. Many other areas in NSW are also reporting poor visibility due to dust in the air.

Sandstorms and their features

A dust storm is a rather dangerous and unpleasant phenomenon in which large masses of dust (sand, soil) are lifted by the wind from the surface of the earth and move at a height of several meters, but in some cases the height can reach a kilometer or even more. From the outside, it looks like a wall of dust and sand is moving towards you.

Other names for this phenomenon are "sandstorm" and " dust storm". It is sometimes also referred to as a sandstorm. This happens because a strong wind is called a storm. A sandstorm is a type of storm. This should be understood.

Usually, after a dust storm (or even before it), particles of sand and dust are suspended in the air. They do not move anywhere, but simply fluctuate in almost one place, greatly worsening the view at the same time. This phenomenon is called dusty haze (or sandy haze).

Causes of the phenomenon

Only two factors are sufficient for a storm to occur: dry soil and strong wind(usually from 10 m/s and stronger). It's simple: the wind lifts loose particles of sand, dust, soil from the ground, which form a dust storm. This happens most often in deserts and semi-deserts, and it is understandable, because these are the most arid regions of the Earth.

Consequences of dust storms

- Reduced visibility, which greatly affects the movement, whether it be flights or vehicles;

- Difficulty breathing living beings;

— Damage to plants (up to their destruction);

— Destruction of the fertile soil layer;

— Reducing the number sunlight reaching the surface of the planet.

Most a large number of dust storms observed in the Sahara desert. It is interesting that earlier they were not too frequent in that area, but since the middle of the last century their number has increased tenfold! If earlier there were ten of them a year, now hundreds of storms a year no longer surprise anyone.
However, such a number is certainly not normal, as evidenced by the greatly reduced thickness of the upper soil layer (the most fertile) of those regions.

Not only are sandstorms common, but they are also dangerous. Sometimes their strength reaches such an extent that the phenomenon can change the relief of the planet, for example, moving dunes in deserts. Although, in fairness, the relief is changed not only by them, but also by some other phenomena. For example, a sand whirlwind, they are also called dust devils.

But it is worth noting that dust storms can also be beneficial. After all, the same fertile soil, which this phenomenon destroys in one region, settles in another. For example, in Hawaii they are welcome, because dust storms contribute to the growth of banana crops. Also, storms replenish the iron content in the oceans, otherwise there would be a serious lack of it, which would affect the plant and animal world oceans (which would affect people's lives).