The circulation of air masses. Atmospheric circulation. air currents in the atmosphere The direction and speed of winds are also affected by

Due to the following factors:

Force of baric gradient (pressure gradient);

Coriolis force;

geostrophic wind;

gradient wind;

Friction force.

baric gradient leads to the fact that the wind that occurs due to the movement of air in the direction of the baric gradient from an area of ​​​​higher pressure to an area of ​​\u200b\u200blower pressure. Atmospheric pressure is 1.033 kg/cm², measured in mm Hg, mB and hPa.

A change in pressure occurs when air moves due to its heating and cooling. The main reason for the transfer of air masses is convective currents - the rise of warm air and its replacement from below by cold air (vertical convection flow). Encountering a layer of high-density air, they spread, forming horizontal convection currents.

Coriolis force- repulsive force. Occurs when the Earth rotates. Under its action, the wind deviates in the Northern Hemisphere - to the right, in the Southern - to the left, i.e. in the North deviates to the east. Closer to the poles, the deflecting force increases.

geostrophic wind.

In temperate latitudes, the force of the pressure gradient and the Coriolis force are balanced, while the air does not move from the area of ​​high pressure to the area of ​​low pressure, but flows between them parallel to the isobars.

gradient wind- this is a circular movement of air parallel to the isobars under the influence of centrifugal and centripetal forces.

The effect of friction force.

The friction of air on the earth's surface upsets the balance between the force of the horizontal baric gradient and the Coriolis force, slows down the movement of air masses, changes their direction so that the air flow does not move along isobars, but crosses them at an angle.

With height, the effect of friction is weakened, the deviation of the wind from the gradient increases. The change in wind speed and direction with height is called Ekman spiral.

The average long-term wind spiral near the Earth is 9.4 m/s, it is maximum near Antarctica (up to 22 m/s), sometimes gusts reach 100 m/s.

With height, the wind speed increases and reaches hundreds of m/s. The direction of the wind depends on the pressure distribution and the deflecting effect of the Earth's rotation. In winter, the winds are directed from the mainland to the ocean, in summer - from the ocean to the mainland. Local winds are called breeze, foehn, bora.

Condensation is the change in the state of a substance from gaseous to liquid or solid. But what is condensation in the mastaba of the planet?

At any given time, the atmosphere of the planet Earth contains over 13 billion tons of moisture. This figure is almost constant, as losses due to precipitation are eventually continuously replaced by evaporation.

Moisture cycle rate in the atmosphere

The rate of circulation of moisture in the atmosphere is estimated at a colossal figure - about 16 million tons per second or 505 billion tons per year. If suddenly all the water vapor in the atmosphere condensed and fell out as precipitation, then this water could cover the entire surface of the globe with a layer of about 2.5 centimeters, in other words, the atmosphere contains an amount of moisture equivalent to only 2.5 centimeters of rain.

How long does a vapor molecule stay in the atmosphere?

Since on Earth an average of 92 centimeters falls per year, therefore, moisture in the atmosphere is renewed 36 times, that is, 36 times the atmosphere is saturated with moisture and freed from it. This means that a water vapor molecule stays in the atmosphere for an average of 10 days.

Water molecule path

Once evaporated, a water vapor molecule usually drifts hundreds and thousands of kilometers until it condenses and falls with precipitation to the Earth. Water, snow or hail in the highlands of Western Europe, overcomes about 3000 km from the North Atlantic. Between the transformation of liquid water into steam and the precipitation on Earth, several physical processes take place.

From the warm surface of the Atlantic, water molecules enter warm, moist air, which then rises above the surrounding colder (more dense) and drier air.

If in this case a strong turbulent mixing of air masses is observed, then a layer of mixing and clouds will appear in the atmosphere at the border of two air masses. About 5% of their volume is moisture. Steam-saturated air is always lighter, firstly, because it is heated and comes from a warm surface, and secondly, because 1 cubic meter of pure steam is about 2/5 lighter than 1 cubic meter of clean dry air at the same temperature and pressure. It follows that moist air is lighter than dry air, and warm and humid air is even more so. As we shall see later, this is a very important fact for weather change processes.

Movement of air masses

Air can rise for two reasons: either because it becomes lighter as a result of heating and moisture, or because forces act on it, causing it to rise above some obstacles, such as masses of colder and denser air, or over hills and mountains.

Cooling

Rising air, having fallen into layers with lower atmospheric pressure, is forced to expand and at the same time cool. Expansion requires the expenditure of kinetic energy, which is taken from the thermal and potential energy of atmospheric air, and this process inevitably leads to a decrease in temperature. The cooling rate of a rising portion of air often changes if this portion is mixed with the surrounding air.

Dry adiabatic gradient

Dry air, in which there is no condensation or evaporation, as well as mixing, which does not receive energy in another form, cools or heats up by a constant amount (by 1 ° C every 100 meters) as it rises or falls. This value is called the dry adiabatic gradient. But if the rising air mass is moist and condensation occurs in it, then the latent heat of condensation is released and the temperature of the air saturated with steam falls much more slowly.

Wet adiabatic gradient

This amount of temperature change is called the wet-adiabatic gradient. It is not constant, but changes with the amount of latent heat released, in other words, it depends on the amount of condensed steam. The amount of steam depends on how much the air temperature drops. In the lower layers of the atmosphere, where the air is warm and humidity is high, the wet-adiabatic gradient is slightly more than half of the dry-adiabatic gradient. But the wet-adiabatic gradient gradually increases with height and at a very high altitude in the troposphere is almost equal to the dry-adiabatic gradient.

The buoyancy of moving air is determined by the ratio between its temperature and the temperature of the surrounding air. As a rule, in the real atmosphere, the temperature of the air falls unevenly with height (this change is simply called a gradient).

If the mass of air is warmer and therefore less dense than the surrounding air (and the moisture content is constant), then it rises in the same way as a child's ball immersed in a tank. Conversely, when the moving air is colder than the surrounding air, its density is higher and it sinks. If the air has the same temperature as the neighboring masses, then their density is equal and the mass remains stationary or moves only together with the surrounding air.

Thus, there are two processes in the atmosphere, one of which promotes the development of vertical air movement, and the other slows it down.

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Interaction between the ocean and the atmosphere.

27. Circulation of air masses.

© Vladimir Kalanov,
"Knowledge is power".

The movement of air masses in the atmosphere is determined by the thermal regime and changes in air pressure. The totality of the main air currents over the planet is called general atmospheric circulation. The main large-scale atmospheric movements that make up the general circulation of the atmosphere: air currents, jet streams, air currents in cyclones and anticyclones, trade winds and monsoons.

The movement of air relative to the earth's surface wind- appears because the atmospheric pressure in different places of the air mass is not the same. It is generally accepted that wind is the horizontal movement of air. In fact, the air usually does not move parallel to the Earth's surface, but at a slight angle, because. atmospheric pressure varies both horizontally and vertically. Wind direction (North, South, etc.) indicates which direction the wind is blowing from. Wind strength refers to its speed. The higher it is, the stronger the wind. Wind speed is measured at meteorological stations at a height of 10 meters above the Earth, in meters per second. In practice, the force of the wind is estimated in points. Each point corresponds to two or three meters per second. With a wind strength of 9 points, it is already considered a storm, and with 12 points - a hurricane. The common term "storm" means any very strong wind, regardless of the number of points. The speed of a strong wind, for example, during a tropical hurricane, reaches enormous values ​​- up to 115 m/s or more. The wind increases on average with height. At the surface of the Earth, its speed is reduced by friction. In winter, the wind speed is generally higher than in summer. The highest wind speeds are observed in temperate and polar latitudes in the troposphere and lower stratosphere.

It is not entirely clear how the wind speed changes over the continents at low altitudes (100–200 m). here the wind speeds reach their highest values ​​in the afternoon, and the lowest ones at night. It is best seen in summer.

Very strong winds, up to stormy ones, occur during the day in the deserts of Central Asia, and at night there is complete calm. But already at an altitude of 150–200 m, a completely opposite picture is observed: a maximum speed at night and a minimum during the day. The same picture is observed both in summer and winter in temperate latitudes.

Gusty winds can bring a lot of trouble to pilots of airplanes and helicopters. Jets of air moving in different directions, in jolts, gusts, either weakening or intensifying, create a large obstacle to the movement of aircraft - a chatter appears - a dangerous violation of normal flight.

Winds blowing from the mountain ranges of the dry mainland in the direction of the warm sea are called bora. It is a strong, cold, gusty wind that usually blows during the cold season.

Bora is known to many in the region of Novorossiysk, on the Black Sea. Such natural conditions are created here that the speed of the bora can reach 40 and even 60 m/s, and the air temperature drops to minus 20°C. Bora occurs most often between September and March, on average 45 days a year. Sometimes the consequences of it were as follows: the harbor froze, ships, buildings, the embankment were covered with ice, roofs were torn off houses, wagons overturned, ships were thrown ashore. Bora is also observed in other regions of Russia - on Baikal, on Novaya Zemlya. Bora is known on the Mediterranean coast of France (where it is called mistral) and in the Gulf of Mexico.

Sometimes vertical vortices appear in the atmosphere with fast spiraling air movement. These whirlwinds are called tornadoes (in America they are called tornadoes). Tornadoes are several tens of meters in diameter, sometimes up to 100–150 m. It is extremely difficult to measure the air velocity inside a tornado. According to the nature of the damage produced by the tornado, the estimated velocities may well be 50–100 m/s, and in especially strong eddies, up to 200–250 m/s with a large vertical velocity component. The pressure in the center of the ascending tornado column drops by several tens of millibars. Millibars for determining pressure are usually used in synoptic practice (along with millimeters of mercury). To convert bars (millibars) to mm. mercury column, there are special tables. In the SI system, atmospheric pressure is measured in hectopascals. 1hPa=10 2 Pa=1mb=10 -3 bar.

Tornadoes exist for a short time - from several minutes to several hours. But even in this short time they manage to do a lot of trouble. When a tornado approaches (over land, tornadoes are sometimes called blood clots) to buildings, the difference between the pressure inside the building and in the center of the blood clot leads to the fact that the buildings seem to explode from the inside - walls are destroyed, windows and frames fly out, roofs are torn off, sometimes it cannot do without human victims. There are times when a tornado lifts people, animals, and various objects into the air and transports them to tens or even hundreds of meters. In their movement, tornadoes move several tens of kilometers above the sea and even more - over land. The destructive power of tornadoes over the sea is less than over land. In Europe, blood clots are rare, more often they occur in the Asian part of Russia. But tornadoes are especially frequent and destructive in the United States. Read more about tornadoes and tornadoes on our website in the section.

Atmospheric pressure is very variable. It depends on the height of the air column, its density and the acceleration of gravity, which varies depending on the geographical latitude and height above sea level. The density of air is the mass per unit of its volume. The density of moist and dry air differs markedly only at high temperature and high humidity. As the temperature decreases, the density increases; with height, the air density decreases more slowly than the pressure. Air density is usually not directly measured, but calculated from equations based on the measured values ​​of temperature and pressure. Indirectly, air density is measured by the deceleration of artificial satellites of the Earth, as well as from observations of the spreading of artificial clouds of sodium vapor created by meteorological rockets.

In Europe, the air density at the Earth's surface is 1.258 kg/m3, at an altitude of 5 km - 0.735, at an altitude of 20 km - 0.087, and at an altitude of 40 km - 0.004 kg/m3.

The shorter the air column, i.e. the higher the place, the less pressure. But the decrease in air density with height complicates this dependence. The equation expressing the law of change in pressure with height in an atmosphere at rest is called the basic equation of statics. It follows from it that with increasing altitude, the change in pressure is negative, and when ascending to the same height, the pressure drop is the greater, the greater the air density and the acceleration of gravity. The main role here belongs to changes in air density. From the basic equation of statics, one can calculate the value of the vertical pressure gradient, which shows the change in pressure when moving per unit height, i.e. decrease in pressure per unit vertical distance (mb/100 m). The pressure gradient is the force that moves the air. In addition to the force of the pressure gradient in the atmosphere, there are inertial forces (Coriolis force and centrifugal force), as well as the friction force. All air currents are considered relative to the Earth, which rotates around its axis.

The spatial distribution of atmospheric pressure is called the baric field. This is a system of surfaces of equal pressure, or isobaric surfaces.

Vertical section of isobaric surfaces above the cyclone (H) and anticyclone (B).
The surfaces are drawn through equal intervals of pressure p.

Isobaric surfaces cannot be parallel to each other and the earth's surface, because temperature and pressure are constantly changing in the horizontal direction. Therefore, isobaric surfaces have a diverse appearance - from shallow "hollows" bent downwards to stretched "hills" curved upwards.

When a horizontal plane intersects isobaric surfaces, curves are obtained - isobars, i.e. lines connecting points with the same pressure values.

Isobar maps, which are built based on the results of observations at a certain point in time, are called synoptic maps. Isobar maps, compiled from long-term average data for a month, season, year, are called climatological.

Long-term average maps of the absolute topography of the isobaric surface 500 mb for December - February.
Heights in geopotential decameters.

On synoptic maps, an interval of 5 hectopascals (hPa) is taken between isobars.

On maps of a limited area, the isobars may break off, but on a map of the entire globe, each isobar is, of course, closed.

But even on a limited map, there are often closed isobars that limit areas of low or high pressure. Areas of low pressure in the center are cyclones, and areas with relatively high pressure are anticyclones.

By cyclone is meant a huge whirlwind in the lower layer of the atmosphere, having a reduced atmospheric pressure in the center and an upward movement of air masses. In a cyclone, pressure increases from the center to the periphery, and the air moves counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. The upward movement of air leads to the formation of clouds and precipitation. From space, cyclones look like swirling cloud spirals in temperate latitudes.

Anticyclone is an area of ​​high pressure. It occurs simultaneously with the development of a cyclone and is a vortex with closed isobars and the highest pressure in the center. Winds in an anticyclone blow clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere. In an anticyclone, there is always a downward movement of air, which prevents the appearance of powerful clouds and prolonged precipitation.

Thus, large-scale circulation of the atmosphere in temperate latitudes is constantly reduced to the formation, development, movement, and then to the attenuation and disappearance of cyclones and anticyclones. Cyclones that arise at the front separating warm and cold air masses move towards the poles, i.e. carry warm air to the polar latitudes. On the contrary, anticyclones that arise in the rear of cyclones in a cold air mass move to subtropical latitudes, transferring cold air there.

Over the European territory of Russia, an average of 75 cyclones occur annually. The diameter of the cyclone reaches 1000 km or more. In Europe, there are an average of 36 anticyclones per year, some of which have a pressure in the center of more than 1050 hPa. The average pressure in the Northern Hemisphere at sea level is 1013.7 hPa, and in the Southern Hemisphere it is 1011.7 hPa.

In January, low pressure areas are observed in the northern parts of the Atlantic and Pacific Ocean, called Icelandic And Aleutian depressions. depression, or pressure minima, are characterized by minimum pressure values ​​- on average, about 995 hPa.

In the same period of the year, high pressure areas appear over Canada and Asia, called the Canadian and Siberian anticyclones. The highest pressure (1075–1085 hPa) is recorded in Yakutia and the Krasnoyarsk Territory, and the minimum pressure is recorded in typhoons over the Pacific Ocean (880–875 hPa).

Depressions are observed in areas where cyclones often occur, which, as they move east and northeast, gradually fill up and give way to anticyclones. The Asian and Canadian anticyclones arise due to the presence at these latitudes of the vast continents of Eurasia and North America. In these areas, anticyclones prevail over cyclones in winter.

In summer, over these continents, the scheme of the baric field and circulation changes radically, and the zone of cyclone formation in the Northern Hemisphere shifts to higher latitudes.

In the temperate latitudes of the Southern Hemisphere, cyclones that arise above the uniform surface of the oceans, moving southeast, meet the ice of Antarctica and stagnate here, having low air pressure at their centers. In winter and summer, Antarctica is surrounded by a low pressure belt (985–990 hPa).

In subtropical latitudes, the circulation of the atmosphere is different over the oceans and in the areas where the continents and oceans meet. Above the Atlantic and Pacific oceans in the subtropics of both hemispheres there are areas of high pressure: these are the Azores and South Atlantic subtropical anticyclones (or baric lows) in the Atlantic and the Hawaiian and South Pacific subtropical anticyclones in the Pacific Ocean.

The equatorial region constantly receives the greatest amount of solar heat. Therefore, in equatorial latitudes (up to 10 ° north and south latitude along the equator), a reduced atmospheric pressure is maintained throughout the year, and in tropical latitudes, in the band 30–40 ° N. and y.sh. - increased, as a result of which constant air flows are formed, directed from the tropics to the equator. These air currents are called trade winds. Trade winds blow throughout the year, changing their intensity only within insignificant limits. These are the most stable winds on Earth. The force of the horizontal baric gradient directs air flows from areas of high pressure to areas of low pressure in the meridional direction, i.e. south and north. Note: The horizontal baric gradient is the pressure difference per unit distance along the normal to the isobar.

But the meridional direction of the trade winds changes under the action of two forces of inertia - the deflecting force of the Earth's rotation (Coriolis force) and centrifugal force, as well as under the action of the air friction force on the earth's surface. The Coriolis force acts on every body moving along the meridian. Let 1 kg of air in the Northern Hemisphere be located at latitude µ and starts moving at a speed V along the meridian to the north. This kilogram of air, like any body on Earth, has a linear speed of rotation U=ωr, where ω is the angular velocity of the Earth's rotation, and r is the distance to the axis of rotation. According to the law of inertia, this kilogram of air will maintain linear velocity U, which he had at latitude µ . Moving north, it will find itself at higher latitudes, where the radius of rotation is smaller and the linear velocity of the Earth's rotation is lower. Thus, this body will outstrip the motionless bodies located on the same meridian, but at higher latitudes.

For an observer, this will look like a deflection of this body to the right under the action of some force. This force is the Coriolis force. By the same logic, a kilogram of air in the Southern Hemisphere will deviate to the left of the direction of motion. The horizontal component of the Coriolis force acting on 1 kg of air is SC=2wVsinY. It deflects the air, acting at right angles to the velocity vector V. In the Northern Hemisphere, it deflects this vector to the right, and in the Southern Hemisphere - to the left. It follows from the formula that the Coriolis force does not arise if the body is at rest, i.e. it only works when the air is moving. In the Earth's atmosphere, the values ​​of the horizontal baric gradient and the Coriolis force are of the same order, so sometimes they almost balance each other. In such cases, the movement of air is almost rectilinear, and it does not move along the pressure gradient, but along or close to the isobar.

Air currents in the atmosphere usually have a vortex character, therefore, in such a movement, centrifugal force acts on each unit of air mass P=V/R, where V is the wind speed, and R is the radius of curvature of the motion trajectory. In the atmosphere, this force is always less than the force of the baric gradient and therefore remains, so to speak, a "local" force.

As for the friction force that occurs between the moving air and the Earth's surface, it slows down the wind speed to a certain extent. It happens like this: the lower volumes of air, which have reduced their horizontal velocity due to the unevenness of the earth's surface, are transferred from the lower levels upwards. Thus, friction on the earth's surface is transmitted upward, gradually weakening. The slowdown in wind speed is noticeable in the so-called planetary boundary layer, which is 1.0 - 1.5 km. above 1.5 km, the effect of friction is insignificant, so higher layers of air are called free atmosphere.

In the equatorial zone, the linear velocity of the Earth's rotation is the highest, respectively, here the Coriolis force is the highest. Therefore, in the tropical zone of the Northern Hemisphere, the trade winds almost always blow from the northeast, and in the Southern Hemisphere - from the southeast.

Low pressure in the equatorial zone is observed constantly, in winter and summer. The band of low pressure that surrounds the entire globe at the equator is called equatorial trough.

Gaining strength over the oceans of both hemispheres, two trade winds, moving towards each other, rush to the center of the equatorial trough. On the low pressure line, they collide, forming the so-called intratropical convergence zone(convergence means "convergence"). As a result of this "convergence" there is an upward movement of air and its outflow above the trade winds to the subtropics. This process creates the conditions for the existence of the convergence zone constantly, throughout the year. Otherwise, the converging air currents of the trade winds would quickly fill the hollow.

Ascending movements of humid tropical air lead to the formation of a powerful layer of cumulonimbus clouds 100–200 km long, from which tropical showers fall. Thus it turns out that the intratropical convergence zone becomes the place where the rains pour out from the steam collected by the trade winds over the oceans.

So simplified, schematically looks like a picture of the circulation of the atmosphere in the equatorial zone of the Earth.

Winds that change direction with the seasons are called monsoons. The Arabic word "mawsin", meaning "season", gave the name to these steady air currents.

Monsoons, unlike jet streams, occur in certain areas of the Earth where twice a year the prevailing winds move in opposite directions, forming the summer and winter monsoons. The summer monsoon is the flow of air from the ocean to the mainland, while the winter monsoon is from the mainland to the ocean. Tropical and extratropical monsoons are known. In Northeast India and Africa, the winter tropical monsoons combine with the trade winds, while the summer southwest monsoons completely destroy the trade winds. The most powerful tropical monsoons are observed in the northern part of the Indian Ocean and in South Asia. Extratropical monsoons originate in strong stable areas of high pressure in winter and low pressure in summer over the continent.

Typical in this regard are the regions of the Russian Far East, China, and Japan. For example, Vladivostok, which lies at the latitude of Sochi due to the action of the extratropical monsoon, is colder than Arkhangelsk in winter, and in summer there are often fogs, precipitation, moist and cool air comes from the sea.

Many tropical countries in South Asia receive moisture brought in the form of heavy rains by the summer tropical monsoon.

Any winds are the result of the interaction of various physical factors that occur in the atmosphere over certain geographical areas. The local winds are breezes. They appear near the coastline of the seas and oceans and have a daily change of direction: during the day they blow from the sea to land, and at night from land to sea. This phenomenon is explained by the difference in temperatures over the sea and land at different times of the day. The heat capacity of land and sea is different. During the day in warm weather, the sun's rays heat the land faster than the sea, and the pressure over the land decreases. Air begins to move in the direction of lower pressure - blowing sea ​​breeze. In the evening, everything happens the other way around. The land and the air above it radiate heat faster than the sea, the pressure becomes higher than over the sea, and the air masses rush towards the sea - blowing coastal breeze. The breezes are especially distinct in calm sunny weather, when nothing interferes with them, i.e. other air currents are not superimposed, which easily drown out the breezes. The speed of the breeze is rarely higher than 5 m/s, but in the tropics, where the temperature difference between the sea and land surfaces is significant, breezes sometimes blow at a speed of 10 m/s. In temperate latitudes, breezes penetrate 25–30 km deep into the territory.

Breezes, in fact, are the same monsoons, only on a smaller scale - they have a daily cycle and change direction depends on the change of night and day, while monsoons have an annual cycle and change direction depending on the time of year.

Ocean currents, meeting the coasts of the continents on their way, are divided into two branches, directed along the coasts of the continents to the north and south. In the Atlantic Ocean, the southern branch forms the Brazil Current, washing the shores of South America, and the northern branch forms the warm Gulf Stream, passing into the North Atlantic Current, and under the name of the North Cape Current, reaching the Kola Peninsula.

In the Pacific Ocean, the northern branch of the equatorial current passes into Kuro-Sivo.

We have previously mentioned the seasonal warm current off the coast of Ecuador, Peru and Northern Chile. It usually occurs in December (not every year) and causes a sharp decrease in fish catch off the coast of these countries due to the fact that there is very little plankton in warm water - the main food resource for fish. A sharp increase in the temperature of coastal waters causes the development of cumulonimbus clouds, from which heavy rains are shed.

The fishermen ironically called this warm current El Nino, which means "Christmas present" (from the Spanish el ninjo - baby, boy). But we want to emphasize not the emotional perception of the Chilean and Peruvian fishermen of this phenomenon, but its physical cause. The fact is that the increase in water temperature off the coast of South America is caused not only by a warm current. Changes in the general situation in the "ocean-atmosphere" system in the vast expanses of the Pacific Ocean are also introduced by the atmospheric process, called " Southern Oscillation". This process, interacting with currents, determines all physical phenomena occurring in the tropics. All this confirms that the circulation of air masses in the atmosphere, especially over the surface of the World Ocean, is a complex, multidimensional process. But with all the complexity, mobility and variability of air currents, there are still certain patterns, due to which in certain areas of the Earth, the main large-scale, as well as local processes of atmospheric circulation are repeated from year to year.

In conclusion of the chapter, we give some examples of the use of wind energy. People have been using wind energy since time immemorial, ever since they learned how to sail the sea. Then there were windmills, and later - wind engines - sources of electricity. Wind is an eternal source of energy, the reserves of which are incalculable. Unfortunately, the use of wind as a source of electricity is very difficult due to the variability of its speed and direction. However, with the help of wind turbines, it has become possible to use wind energy quite efficiently. The blades of a windmill make it almost always "keep its nose" in the wind. When the wind has sufficient strength, the current goes directly to consumers: for lighting, for refrigeration units, for various devices and for charging batteries. When the wind subsides, the batteries transfer the accumulated electricity to the grid.

At scientific stations in the Arctic and Antarctic, the electricity from wind turbines provides light and heat, ensures the operation of radio stations and other consumers of electricity. Of course, at each scientific station there are diesel generators, for which you need to have a constant supply of fuel.

The very first navigators used the power of the wind spontaneously, without taking into account the system of winds and ocean currents. They simply did not know anything about the existence of such a system. Knowledge about winds and currents has been accumulated over centuries and even millennia.

One of the contemporaries was the Chinese navigator Zheng He during 1405-1433. led several expeditions that passed the so-called Great Monsoon Route from the mouth of the Yangtze River to India and the eastern shores of Africa. Information about the scale of the first of these expeditions has been preserved. It consisted of 62 ships with 27,800 participants. For sailing expeditions, the Chinese used their knowledge of the patterns of monsoon winds. From China, they went to sea in late November - early December, when the northeast winter monsoon blows. A fair wind helped them reach India and East Africa. They returned to China in May - June, when the summer southwest monsoon was established, which became south in the South China Sea.

Let's take an example from a time closer to us. It will be about the travels of the famous Norwegian scientist Thor Heyerdahl. With the help of the wind, or rather, with the help of the trade winds, Heyerdahl was able to prove the scientific value of his two hypotheses. The first hypothesis was that the islands of Polynesia in the Pacific Ocean could, according to Heyerdahl, be inhabited at some time in the past by immigrants from South America who crossed a significant part of the Pacific Ocean on their primitive watercraft. These boats were rafts made of balsa wood, which is notable for the fact that after a long stay in the water, it does not change its density, and therefore does not sink.

Peruvians have been using these rafts for thousands of years, even before the Inca Empire. Thor Heyerdahl in 1947 tied a raft of large balsa logs and named it "Kon-Tiki", which means the Sun-Tiki - the deity of the ancestors of the Polynesians. Taking five adventurers on board his raft, he set sail from Callao (Peru) to Polynesia. At the beginning of the voyage, the raft carried the Peruvian current and the southeast trade wind, and then the east trade wind of the Pacific Ocean set to work, which for almost three months without interruption blew regularly to the west, and after 101 days, Kon-Tiki safely arrived on one of the islands of the Tuamotu archipelago ( now French Polynesia).

Heyerdahl's second hypothesis was that he considered it quite possible that the culture of the Olmecs, Aztecs, Maya and other tribes of Central America was transferred from Ancient Egypt. This was possible, according to the scientist, because once in ancient times people sailed across the Atlantic Ocean on papyrus boats. The trade winds also helped Heyerdahl to prove the validity of this hypothesis.

Together with a group of like-minded satellites, he made two voyages on papyrus boats "Ra-1" and "Ra-2". The first boat ("Ra-1") fell apart before reaching the American coast for several tens of kilometers. The crew was in serious danger, but everything turned out well. The boat for the second voyage ("Ra-2") was knitted by "high-class specialists" - Indians from the Central Andes. Leaving the port of Safi (Morocco), the papyrus boat "Ra-2" after 56 days crossed the Atlantic Ocean and reached the island of Barbados (about 300-350 km from the coast of Venezuela), having overcome 6100 km of the way. At first, the northeast trade wind drove the boat, and starting from the middle of the ocean, the east trade wind.

The scientific nature of Heyerdahl's second hypothesis has been proven. But something else was also proven: despite the successful outcome of the voyage, a boat tied from bundles of papyrus, reeds, reeds or other aquatic plants is not suitable for swimming in the ocean. Such "shipbuilding material" should not be used, as it quickly gets wet and sinks into the water. Well, if there are still amateurs who are obsessed with the desire to swim across the ocean on some exotic watercraft, then let them keep in mind that a balsa wood raft is more reliable than a papyrus boat, and also that such a journey is always and in any case dangerously.

© Vladimir Kalanov,
"Knowledge is power"

air masses- large volumes of air in the lower part of the earth's atmosphere - the troposphere, having horizontal dimensions of many hundreds or several thousand kilometers and vertical dimensions of several kilometers, characterized by an approximate horizontal uniformity of temperature and moisture content.

Kinds:Arctic or Antarctic air(AB), temperate air(UV), tropical air(TV) equatorial air(EV).

The air in the ventilation layers can move in the form laminar or turbulent flow. concept "laminar" means that the individual air flows are parallel to each other and move in the ventilation space without turbulence. When turbulent flow its particles move not only in parallel, but also make transverse motion. This leads to vortex formation over the entire cross section of the ventilation duct.

The state of the air flow in the ventilation space depends on: Air flow velocity, Air temperature, Cross-sectional area of ​​the ventilation duct, Forms and surfaces of building elements at the border of the ventilation duct.

In the earth's atmosphere, air movements of various scales are observed - from tens and hundreds of meters (local winds) to hundreds and thousands of kilometers (cyclones, anticyclones, monsoons, trade winds, planetary frontal zones).
The air is constantly moving: it rises - an upward movement, it falls - a downward movement. The movement of air in a horizontal direction is called wind. The reason for the occurrence of wind is the uneven distribution of air pressure on the surface of the Earth, which is caused by an uneven distribution of temperature. In this case, the air flow moves from places with high pressure to the side where the pressure is less.
With the wind, the air does not move evenly, but in shocks, gusts, especially near the surface of the Earth. There are many reasons that affect the movement of air: the friction of the air flow on the surface of the Earth, encountering obstacles, etc. In addition, air flows under the influence of the rotation of the Earth deviate to the right in the northern hemisphere, and to the left in the southern hemisphere.

Invading areas with different thermal properties of the surface, the air masses are gradually transformed. For example, temperate marine air, entering the land and moving deep into the mainland, gradually heats up and dries up, turning into continental air. The transformation of air masses is especially characteristic of temperate latitudes, which are occasionally invaded by warm and dry air from tropical latitudes and cold and dry air from subpolar latitudes.

is an important factor in climate formation. It is expressed by the movement of various types of air masses.

air masses- These are the moving parts of the troposphere, differing from each other in temperature and humidity. Air masses are maritime And continental.

Maritime air masses form over the oceans. They are wetter than continental ones that form over land.

In various climatic zones of the Earth, their own air masses are formed: equatorial, tropical, temperate, arctic And Antarctic.

Moving, air masses retain their properties for a long time and therefore determine the weather of the places where they arrive.

Arctic air masses formed over the Arctic Ocean (in winter - and over the north of the continents of Eurasia and North America). They are characterized by low temperature, low humidity and high air transparency. Intrusions of arctic air masses into temperate latitudes cause a sharp cooling. At the same time, the weather is mostly clear and partly cloudy. When moving deep into the mainland to the south, the arctic air masses are transformed into dry continental air of temperate latitudes.

Continental arctic air masses form over the icy Arctic (in its central and eastern parts) and over the northern coast of the continents (in winter). Their features are very low air temperatures and low moisture content. The invasion of continental arctic air masses on the mainland leads to severe cooling in clear weather.

Marine arctic air masses are formed in warmer conditions: above the ice-free water area with higher air temperature and high moisture content - this is the European Arctic. Intrusions of such air masses on the mainland in winter even cause warming.

An analogue of the Arctic air of the Northern Hemisphere in the Southern Hemisphere are Antarctic air masses. Their influence extends to a greater extent to the adjacent sea surfaces and rarely to the southern margin of the mainland of South America.

Moderate(polar) air is the air of temperate latitudes. Moderate air masses penetrate the polar, as well as subtropical and tropical latitudes.

Continental temperate air masses in winter usually bring clear weather with severe frosts, and in summer - quite warm, but cloudy, often rainy, with thunderstorms.

marine temperate air masses are carried to the mainland by westerly winds. They are distinguished by high humidity and moderate temperatures. In winter, temperate maritime air masses bring cloudy weather, heavy rainfall and thaws, and in summer - great cloudiness, rains and temperature drops.

tropical air masses are formed in tropical and subtropical latitudes, and in summer - in continental regions in the south of temperate latitudes. Tropical air penetrates into temperate and equatorial latitudes. Heat is a common feature of tropical air.

Continental tropical air masses are dry and dusty, and maritime tropical air masses- high humidity.

equatorial air, originating in the region of the Equatorial Depression, very warm and humid. In the summer in the Northern Hemisphere, the equatorial air, moving northward, is drawn into the circulation system of the tropical monsoons.

Equatorial air masses formed in the equatorial zone. They are distinguished by high temperatures and humidity throughout the year, and this applies to air masses that form both over land and over the ocean. Therefore, equatorial air is not divided into marine and continental subtypes.

The entire system of air currents in the atmosphere is called general circulation of the atmosphere.

atmospheric front

Air masses are constantly moving, changing their properties (transforming), but rather sharp boundaries remain between them - transition zones several tens of kilometers wide. These border areas are called atmospheric fronts and are characterized by an unstable state of temperature, air humidity, .

The intersection of such a front with the earth's surface is called atmospheric front line.

When an atmospheric front passes through any area, the air masses change over it and, as a result, the weather changes.

Frontal precipitation is typical for temperate latitudes. In the zone of atmospheric fronts, extensive cloud formations with a length of thousands of kilometers arise and precipitation occurs. How do they arise? The atmospheric front can be considered as the boundary of two air masses, which is inclined to the earth's surface at a very small angle. Cold air is next to warm air and above it in the form of a gentle wedge. In this case, warm air rises up the cold air wedge and cools, approaching saturation. Clouds form from which precipitation falls.

If the front moves towards the retreating cold air, warming occurs; such a front is called warm. cold front, on the contrary, it moves towards the territory occupied by warm air (Fig. 1).

Rice. 1. Types of atmospheric fronts: a - warm front; b - cold front