Atmospheric circulation. Air currents in the atmosphere

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 various places 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. Top speeds winds 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.

Highly strong winds, to stormy ones, are 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 its consequences 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 Earth satellites, 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 relationship. 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 atmospheric circulation 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 largest number solar heat constantly receives the equatorial region. 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 powerful stable areas of high pressure arising over the continent in winter and low pressure in summer.

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 everything 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 regions 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 to 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 american coast 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 "specialists upper class" - 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 water plant 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 dangerous.

© Vladimir Kalanov,
"Knowledge is power"

The movement of air masses should lead, first of all, to the smoothing of baric and temperature gradients. However, on our rotating planet with different heat capacity properties of the earth's surface, different heat reserves of land, seas and oceans, the presence of warm and cold ocean currents, polar and continental ice the processes are very complex and often the contrasts of the heat content of various air masses not only do not smooth out, but, on the contrary, increase.[ ...]

The movement of air masses above the Earth's surface is determined by many reasons, including the rotation of the planet, the uneven heating of its surface by the Sun, the formation of zones of low (cyclones) and high (anticyclones) pressure, flat or mountainous terrain, and much more. In addition, at different heights, the speed, stability and direction of air flows are very different. Therefore, the transfer of pollutants entering different layers of the atmosphere proceeds at different rates and sometimes in other directions than in the surface layer. With very strong emissions associated with high energies, pollution falling into high, up to 10-20 km, layers of the atmosphere, can move thousands of kilometers within a few days or even hours. Thus, the volcanic ash thrown out by the explosion of the Krakatau volcano in Indonesia in 1883 was observed in the form of peculiar clouds over Europe. Fallout different intensity after testing especially powerful hydrogen bombs fell out almost on the entire surface of the Earth.[ ...]

The movement of air masses - the wind resulting from the difference in temperature and pressure in different regions of the planet affects not only the physical and chemical properties of the air itself, but also the intensity of heat transfer, changes in humidity, pressure, chemical composition of air, reducing or increasing the amount pollution.[ ...]

The movement of air masses can be in the form of their passive movement of a convective nature or in the form of wind - due to the cyclonic activity of the Earth's atmosphere. In the first case, the settlement of spores, pollen, seeds, microorganisms and small animals is ensured, which have special adaptations for this - anemochores: very small sizes, parachute-like appendages, etc. (Fig. 2.8). All this mass of organisms is called aeroplankton. In the second case, the wind also carries aeroplankton, but over much longer distances, while it can also carry pollutants to new zones, etc.[ ...]

The movement of air masses (wind). As is known, the reason for the formation of wind flows and the movement of air masses is the uneven heating of different parts of the earth's surface, associated with pressure drops. The wind flow is directed towards lower pressure, but the rotation of the Earth also affects the circulation of air masses on a global scale. In the surface layer of air, the movement of air masses affects all meteorological factors of the environment, i.e., the climate, including temperature, humidity, evaporation from the land and sea, as well as plant transpiration.[ ...]

ANOMALOUS CYCLONE MOVEMENT. The movement of the cyclone in a direction sharply diverging from the usual, i.e. from eastern half horizon to the west or along the meridian. A.P.C. is associated with the anomalous direction of the leading flow, which in turn is due to the unusual distribution of warm and cold air masses in the troposphere.[ ...]

AIR MASS TRANSFORMATION. 1. A gradual change in the properties of the air mass during its movement due to changes in the conditions of the underlying surface (relative transformation).[ ...]

The third reason for the movement of air masses is dynamic, which contributes to the formation of high pressure areas. Due to the fact that the most heat comes to the equatorial zone, air masses rise up to 18 km here. Therefore, intensive condensation and precipitation in the form of tropical showers are observed. In the so-called "horse" latitudes (about 30° N and 30° S), cold dry air masses, descending and heating adiabatically, intensively absorb moisture. Therefore, in these latitudes, the main deserts of the planet naturally form. They mainly formed in the western parts of the continents. The westerly winds coming from the ocean do not contain enough moisture to transfer to the descending dry air. Therefore, there is very little rainfall.[ ...]

The formation and movement of air masses, the location and trajectories of cyclones and anticyclones have great importance for making weather forecasts. A synoptic map provides a visual representation of the state of the weather at the moment over a vast territory.[ ...]

WEATHER TRANSFER. The movement of certain weather conditions along with their "carriers" - air masses, fronts, cyclones and anticyclones.[ ...]

In a narrow border strip separating air masses, frontal zones (fronts) arise, characterized by an unstable state of meteorological elements: temperature, pressure, humidity, wind direction and speed. Here, with exceptional clarity, the most important physical geography the principle of media contrast, which is expressed in a sharp activation of the exchange of matter and energy in the zone of contact (contact) of different properties natural complexes and their components (F. N. Milkov, 1968). The active exchange of matter and energy between air masses in the frontal zones is manifested in the fact that it is here that the origin, movement with a simultaneous increase in power and, finally, the extinction of cyclones take place.[ ...]

Solar energy causes planetary movements of air masses as a result of their uneven heating. Grandiose processes of atmospheric circulation arise, which are of a rhythmic nature.[ ...]

If in a free atmosphere with turbulent movements of air masses this phenomenon does not play a noticeable role, then in a stationary or low-moving indoor air, this difference should be taken into account. In close proximity to the surface various bodies we will have a layer with some excess of negative air ions, while the surrounding air will be enriched with positive air ions.[ ...]

Non-periodic weather changes are caused by the movement of air masses from one geographical area to another in common system atmospheric circulation.[ ...]

Due to the fact that at high altitudes the speed of movement of air masses reaches 100 m/s, ions moving in a magnetic field can be displaced, although these displacements are insignificant compared to the transfer in a stream. It is important for us that in the polar zones, where the lines of force magnetic field The earth closes on its surface, the distortion of the ionosphere is very significant. The number of ions, including ionized oxygen, in the upper layers of the atmosphere of the polar zones is reduced. But the main reason for the low ozone content in the region of the poles is the low intensity of solar radiation, which falls even during the polar day at small angles to the horizon, and is completely absent during the polar night. In itself, the screening role of the ozone layer in the polar regions is not so important precisely because of the low position of the Sun above the horizon, which excludes the high intensity of UV radiation of the surface. However, the area of ​​polar "holes" in ozone layer is a reliable indicator of changes in total atmospheric ozone.[ ...]

The translational horizontal movements of water masses associated with the movement of significant volumes of water over long distances are called currents. Currents arise under the influence of various factors, such as wind (i.e. friction and pressure of moving air masses on the water surface), changes in the distribution of atmospheric pressure, uneven distribution of density sea ​​water(i.e., the horizontal pressure gradient of waters of different densities at the same depths), the tidal forces of the Moon and the Sun. The nature of the movement of masses of water is also significantly influenced by secondary forces, which themselves do not cause it, but manifest themselves only in the presence of movement. These forces include the force that arises due to the rotation of the Earth - the Coriolis force, centrifugal forces, friction of the waters on the bottom and coasts of the continents, internal friction. The distribution of land and sea, the topography of the bottom and the outlines of the coasts have a great influence on sea currents. Currents are classified mainly by origin. Depending on the forces that excite them, the currents are combined into four groups: 1) frictional (wind and drift), 2) gradient-gravitational, 3) tidal, 4) inertial.[ ...]

wind turbines and sailing ships the silon of the movement of air masses moves due to its heating by the sun and the creation of air currents or winds. one.[ ...]

MOTION CONTROL. The formulation of the fact that the movement of air masses and tropospheric disturbances mainly occurs in the direction of the isobars (isohypses) and, consequently, the air currents of the upper troposphere and lower stratosphere.[ ...]

This, in turn, may lead to a violation of the movement of air masses near industrial areas located next to such a park and increased air pollution.[ ...]

Most weather phenomena depend on whether air masses are stable or unstable. With stable air, vertical movements in it are difficult, with unstable air, on the contrary, they develop easily. The stability criterion is the observed temperature gradient.[ ...]

Hydrodynamic, closed type with adjustable air cushion pressure, with pulsation dampener. Structurally, it consists of a body with a lower lip, a collector with a tilting mechanism, a turbulator, an upper lip with a mechanism for vertical and horizontal movement, mechanisms for fine adjustment of the outlet slot profile with the ability to automatically control the transverse profile of the paper web. The surfaces of the parts of the box that come into contact with the mass are carefully polished and electropolished.[ ...]

The potential temperature, in contrast to the molecular temperature T, remains constant during dry adiabatic movements of the same air particle. If in the process of moving the air mass its potential temperature has changed, then there is an inflow or outflow of heat. The dry adiabat is a line of equal potential temperature.[ ...]

The most typical case of dispersion is the movement of a gas jet in a moving medium, i.e., during the horizontal movement of air masses of the atmosphere.[ ...]

The main reason for short-period OS oscillations, according to the concept put forward in 1964 by the author of the work, is the horizontal movement of the ST axis, which is directly related to the movement of long waves in the atmosphere. Moreover, the direction of the wind in the stratosphere over the place of observation does not play a significant role. In other words, short-term OS fluctuations are caused by a change in air masses in the stratosphere above the observation site, since these masses separate ST.[ ...]

On the state of the free surface of reservoirs due to the large area of ​​their surface strong influence exerts the wind. The kinetic energy of the air flow is transferred to the masses of water through friction forces at the interface between two media. One part of the transferred energy is spent on the formation of waves, and the other part is used to create a drift current, i.e. progressive movement of the surface layers of water in the direction of the wind. In reservoirs of limited size, the movement of water masses by a drift current leads to a distortion of the free surface. At the windward coast, the water level drops - a wind surge occurs, at the leeward coast the level rises - a wind surge occurs. At the Tsimlyansk and Rybinsk reservoirs, level differences of 1 m or more were recorded near the leeward and windward shores. With a long wind, the skew becomes stable. Masses of water that are brought to the leeward coast by a drift current are diverted in the opposite direction by a near-bottom gradient current.[ ...]

The results obtained are based on solving the problem for stationary conditions. However, the considered scales of the terrain are relatively small and the time of movement of the air mass ¿ = l:/u is small, which allows us to limit ourselves to the parametric consideration of the characteristics of the oncoming air flow.[ ...]

But the icy Arctic creates difficulties in agriculture not only because of cold and long winters. Cold, and therefore dehydrated arctic: air masses do not warm up during spring-summer movement. The higher the temperature, the more! moisture is needed to saturate it. I. P. Gerasimov and K. K. Mkov noted that “at present, a simple increase in the ice cover of the Arctic Basin causes. . . zas; in Ukraine and the Volga region” 2.[ ...]

In 1889, a giant cloud of locusts flew from the coast of North Africa across the Red Sea to Arabia. The movement of insects lasted a whole day, and their mass was 44 million tons. V.I. Vernadsky regarded this fact as evidence of the enormous power of living matter, an expression of the pressure of life, striving to capture the entire Earth. At the same time, he saw in this a biogeochemical process - the migration of elements included in the biomass of the locust, a completely special migration - through the air, over long distances, not consistent with the usual mode of movement of air masses in the atmosphere.[ ...]

Thus, the main factor determining the speed of katabatic winds is the temperature difference between the ice cover and the atmosphere 0 and the angle of inclination of the ice surface. The movement of the cooled air mass down the slope of the ice dome of Antarctica is enhanced by the effects of the fall of the air mass from the height of the ice dome and the influence of baric gradients in the Antarctic High. Horizontal baric gradients, being an element of the formation of katabatic winds in Antarctica, contribute to an increase in the outflow of air to the periphery of the continent, primarily due to its supercooling near the surface of the ice sheet and the slope of the ice dome towards the sea.[ ...]

The analysis of synoptic maps is as follows. According to the information plotted on the map, the actual state of the atmosphere at the time of observation is established: the distribution and nature of air masses and fronts, the location and properties of atmospheric disturbances, the location and nature of clouds and precipitation, temperature distribution, etc. for given conditions of atmospheric circulation. By compiling maps for different periods, you can follow them for changes in the state of the atmosphere, in particular, for the movement and evolution of atmospheric disturbances, the movement, transformation and interaction of air masses, etc. The presentation of atmospheric conditions on synoptic maps provides a convenient opportunity for information about the state of the weather.[ . ..]

Atmospheric macroscale processes studied with the help of synoptic maps and which are the cause of the weather regime over large geographic areas. This is the emergence, movement and change in the properties of air masses and atmospheric fronts; the emergence, development and movement of atmospheric disturbances - cyclones and anticyclones, the evolution of condensation systems, intramass and frontal, in connection with the above processes, etc.[ ...]

Until aerial chemical treatment is completely excluded, it is necessary to make improvements in its application through the most careful selection of objects, reducing the likelihood of "demolitions" - movements of sawing air masses, controlled dosage, etc. For primary care in clearings through the use of herbicides, it is advisable to use typological diagnostics to a greater extent clearings. Chemistry is a powerful means of forest care. But it is important that chemical care does not turn into poisoning of the forest, its inhabitants and visitors.[ ...]

In the nature around us, water is in constant motion - and this is just one of the many natural cycles of substances in nature. When we say “movement”, we mean not only the movement of water as a physical body (flow), not only its movement in space, but, above all, the transition of water from one physical state to another. In Figure 1 you can see how the water cycle works. On the surface of lakes, rivers and seas, water under the influence of the energy of sunlight turns into water vapor - this process is called evaporation. In the same way, water evaporates from the surface of the snow and ice cover, from the leaves of plants and from the bodies of animals and humans. Water vapor with warmer air flows rises to the upper atmosphere, where it gradually cools and again turns into a liquid or turns into a solid state - this process is called condensation. At the same time, water moves with the movement of air masses in the atmosphere (winds). From the resulting water droplets and ice crystals, clouds are formed, from which, in the end, rain or snow falls on the ground. Water returned to earth in the form of precipitation flows down the slopes and collects in streams and rivers that flow into lakes, seas and oceans. Part of the water seeps through the soil and rocks, reaches groundwater and groundwater, which also, as a rule, have a runoff into rivers and other water bodies. Thus, the circle closes and can be repeated in nature indefinitely.[ ...]

SYNOPTIC METEOROLOGY. Meteorological discipline, which took shape in the second half of the XIX century. and especially in the 20th century; the doctrine of atmospheric macroscale processes and weather forecasting based on their study. Such processes are the emergence, evolution and movement of cyclones and anticyclones, which are closely related to the emergence, movement and evolution of air masses and fronts between them. The study of these synoptic processes is carried out with the help of a systematic analysis of synoptic maps, vertical sections of the atmosphere, aerological diagrams and other auxiliary means. The transition from a synoptic analysis of circulation conditions over large areas of the earth's surface to their forecast and to the forecast of weather conditions associated with them is still largely reduced to extrapolation and qualitative conclusions from the provisions of dynamic meteorology. However, in the last 25 years, the numerical (hydrodynamic) forecast of meteorological fields has been increasingly used by numerically solving the equations of atmospheric thermodynamics on electronic computers. See also the weather service, weather forecast and a number of other terms. Common synonym: weather forecast.[ ...]

The case of jet propagation analyzed by us is not typical, since there are very few calm periods in almost any area. Therefore, the most typical case of scattering is the movement of a gas jet in a moving medium, i.e., in the presence of a horizontal movement of atmospheric air masses.[ ...]

It is obvious that simply the air temperature T is not a conservative characteristic of the heat content of the air. So, with a constant heat content of an individual volume of air (turbulent mole), its temperature can vary depending on the pressure (1.1). Atmospheric pressure, as we know, decreases with height. As a result, vertical movement of air leads to changes in its specific volume. In this case, the work of expansion is realized, which leads to changes in the temperature of air particles even in the case when the processes are isentropic (adiabatic), i.e. there is no heat exchange of an individual mass element with the surrounding space. Changes in the temperature of the air moving vertically will correspond to dry diabatic or wet diabatic gradients, depending on the nature of the thermodynamic process.

Ever since I was a child, I have been fascinated by the invisible movements around us: a gentle breeze whirling autumn leaves in a cramped courtyard or a powerful winter cyclone. It turns out that these processes have quite understandable physical laws.

What forces cause air masses to move

Warm air is lighter than cold air - this simple principle can explain the movement of air on the planet. It all starts at the equator. Here, the sun's rays fall on the Earth's surface at a right angle, and a small particle of equatorial air gets a little more heat than neighboring ones. This warm particle becomes lighter than the neighboring ones, which means it starts to float up until it loses all the heat and starts to sink again. But downward movement is already taking place in the thirtieth latitudes of the Northern or Southern Hemisphere.

If there were no additional forces, the air would move from the equator to the poles. But there is not one, but several forces at once that make air masses move:

• The power of buoyancy. When warm air rises and cold air stays down.
• Coriolis force. I'll tell you about it a little lower.
• The relief of the planet. Combinations of seas and oceans, mountains and plains.

The deflecting force of the Earth's rotation

It would be easier for meteorologists if our planet did not rotate. But she's spinning! This generates the deflecting force of the Earth's rotation or the Coriolis force. Due to the motion of the planet, that very “light” particle of air is not only displaced, say, to the north, but also shifts to the right. Or it is forced out to the south and deviates to the left.

This is how constant winds of western or eastern directions are born. Perhaps you have heard of the current of the West Winds or the Roaring Forties? These constant movements of air arose precisely because of the Coriolis force.

Seas and oceans, mountains and plains

The relief brings the final confusion. The distribution of land and ocean changes the classical circulation. So, in the Southern Hemisphere, there is much less land than in the Northern, and nothing prevents the air from moving over the water surface in the direction it needs, there are no mountains or large cities, while the Himalayas radically change the air circulation in their area.

The atmosphere is not uniform. In its composition, especially near the earth's surface, air masses can be distinguished.

Air masses are separate large volumes of air that have certain common properties(temperature, humidity, transparency, etc.) and moving as a whole. However, within this volume, the winds can be different. The properties of the air mass are determined by the region of its formation. It acquires them in the process of contact with the underlying surface, over which it forms or lingers. Air masses have different properties. For example, the air of the Arctic has low temperatures, while the air of the tropics has high temperatures in all seasons of the year, the air of the North Atlantic differs significantly from the air of the Eurasian continent. The horizontal dimensions of the air masses are enormous, they are commensurate with the continents and oceans or their large parts. There are main (zonal) types of air masses that form in belts with different atmospheric pressure: arctic (antarctic), temperate (polar), tropical and equatorial. Zonal air masses are divided into maritime and continental - depending on the nature of the underlying surface in the area of ​​their formation.

Arctic air is formed over the Arctic Ocean, and in winter also over the north of Eurasia and North America. The air is characterized by low temperature, low moisture content, good visibility and stability. Its intrusions into temperate latitudes cause significant and sharp cooling and determine predominantly clear and slightly cloudy weather. Arctic air is divided into the following varieties.

Maritime Arctic air (mAv) - formed in the warmer, ice-free European Arctic with higher temperature and higher moisture content. Its incursions into the mainland in winter cause warming.

Continental arctic air (cAv) - formed over the Central and Eastern icy Arctic and the northern coast of the continents (in winter). The air is very low temperatures, low moisture content. The invasion of the KAV on the mainland causes a strong cooling in clear weather and good visibility.

An analogue of the Arctic air in the Southern Hemisphere is the Antarctic air, but its influence extends mainly to the adjacent sea surfaces, less often to the southern tip of South America.

Moderate (polar) air. This is the air of temperate latitudes. It also has two subtypes. Continental temperate air (CW), which is formed over the vast surfaces of the continents. In winter it is very chilled and stable, the weather is usually clear with hard frosts. In summer, it gets very warm, ascending currents arise in it, clouds form, it often rains, thunderstorms are observed. Marine temperate air (MOA) is formed in the middle latitudes over the oceans, and is transported to the continents by westerly winds and cyclones. It is characterized by high humidity and moderate temperatures. In winter, MUW brings cloudy weather, heavy rainfall and higher temperatures (thaws). In summer it also brings a lot of cloudiness, rains; the temperature drops as it enters.

Temperate air penetrates into the polar, as well as subtropical and tropical latitudes.

Tropical air is formed in tropical and subtropical latitudes, and in summer - in continental regions in the south of temperate latitudes. There are two subtypes of tropical air. Continental tropical air (cTw) is formed over land, characterized by high temperatures, dryness and dustiness. Marine tropical air (mTw) is formed over tropical areas (tropical ocean zones), characterized by high temperature and humidity.

Tropical air penetrates into temperate and equatorial latitudes.

Equatorial air is formed in the equatorial zone from tropical air brought by the trade winds. It is characterized by high temperatures and high humidity throughout the year. In addition, these qualities are preserved both over land and over the sea, therefore, equatorial air is not divided into marine and continental subtypes.

Air masses are in constant motion. Moreover, if the air masses move to higher latitudes or to a colder surface, they are called warm, since they bring warming. Air masses moving to lower latitudes or to a warmer surface are called cold air masses. They bring coldness.

Moving to other geographical areas, air masses gradually change their properties, primarily temperature and humidity, i.e. move into other types of air masses. The process of transformation of air masses from one type to another under the influence of local conditions is called transformation. For example, tropical air, penetrating towards the equator and into temperate latitudes, is transformed into equatorial and temperate air, respectively. Marine temperate air, once in the depths of the continents, cools in winter, and heats up in summer and always dries up, turning into temperate continental air.

All air masses are interconnected in the process of their constant movement, in the process of the general circulation of the troposphere.

Atmospheric circulation scheme

Air in the atmosphere is in constant motion. It moves both horizontally and vertically.

The root cause of the movement of air in the atmosphere is the uneven distribution solar radiation and heterogeneity of the underlying surface. They cause uneven air temperature and, accordingly, atmospheric pressure above the earth's surface.

The pressure difference creates a movement of air that moves from areas of high to areas of low pressure. In the process of moving, air masses are deflected by the force of the rotation of the Earth.

(Remember how bodies move in the northern and southern hemispheres deviate.)

Of course, you have noticed how a light haze forms over the asphalt on a hot summer day. It's heated light air rises up. A similar but much larger picture can be seen at the equator. Very hot air constantly rises, forming updrafts.

Therefore, a constant low-pressure belt is formed near the surface here.
The air that has risen above the equator in the upper layers of the troposphere (10-12 km) spreads to the poles. Gradually, it cools and begins to descend approximately above 30 t ° north and south latitude.

Thus, an excess of air is formed, which contributes to the formation of a tropical high-pressure belt in the surface layer of the atmosphere.

In the circumpolar regions, the air is cold, heavy and descends, causing downward movements. As a result, high pressure is formed in the near-surface layers of the polar belt.

Active atmospheric fronts form between the tropical and polar high-pressure belts in temperate latitudes. Massively colder air displaces warmer air upwards, causing updrafts.

As a result, a surface low-pressure belt is formed in temperate latitudes.

Map of the Earth's climate zones

If the earth's surface were uniform, atmospheric pressure belts would spread in continuous bands. However, the surface of the planet is an alternation of water and land, which have different properties. The land quickly heats up and cools down.

The ocean, on the contrary, heats up and releases its heat slowly. That is why atmospheric pressure belts are torn into separate sections - areas of high and low pressure. Some of them exist throughout the year, others - in a certain season.

On Earth, high and low pressure belts naturally alternate. High pressure - at the poles and near the tropics, low - at the equator and in temperate latitudes.

Types of atmospheric circulation

There are several powerful links in the circulation of air masses in the Earth's atmosphere. All of them are active and inherent in certain latitudinal zones. Therefore, they are called zonal types of atmospheric circulation.

Near the Earth's surface, air currents move from the tropical high-pressure belt to the equator. Under the influence of the force arising from the rotation of the Earth, they deviate to the right in the Northern Hemisphere and to the left in the Southern.

This is how constant powerful winds are formed - trade winds. In the Northern Hemisphere, the trade winds blow in the direction from the northeast, and in the Southern Hemisphere - from the southeast. So, the first zonal type of atmospheric circulation - trade wind.

Air moves from the tropics to temperate latitudes. Deviating under the influence of the force of the rotation of the Earth, they begin to gradually move from west to east. It is this flow from the Atlantic that covers the temperate latitudes of all of Europe, including Ukraine. Western air transport in temperate latitudes is the second zonal type of planetary atmospheric circulation.

The movement of air from the subpolar belts of high pressure to temperate latitudes, where the pressure is low, is also regular.

Under the influence of the deflecting force of the Earth's rotation, this air moves from the northeast in the Northern Hemisphere and from the southeast - in the Southern Hemisphere. The eastern subpolar flow of air masses forms the third zonal type of atmospheric circulation.

On the atlas map, find the latitudinal zones where various types of zonal air circulation dominate.

Due to the uneven heating of the land and ocean, the zonal pattern of movement of air masses is violated. For example, in the east of Eurasia in temperate latitudes, the western air transfer operates only for half a year - in winter. In summer, when the mainland heats up, the air masses move to land with the coolness of the ocean.

This is how the monsoon air transport occurs. The change in the direction of air movement twice a year is a characteristic feature of the monsoon circulation. The winter monsoon is a flow of relatively cold and dry air from the mainland to the ocean.

summer monsoon- the movement of moist and warm air in the opposite direction.

Zonal types of atmospheric circulation

There are three main zonal type of atmospheric circulation: trade wind, western air transport and eastern circumpolar air mass flow. Monsoonal air transport disrupts the general scheme of atmospheric circulation and is an azonal type of circulation.

General circulation of the atmosphere (page 1 of 2)

Ministry of Science and Education of the Republic of Kazakhstan

Academy of Economics and Law named after U.A. Dzholdasbekova

Faculty of Humanities and Economics Academy

By discipline: Ecology

On the topic: "General circulation of the atmosphere"

Completed by: Tsarskaya Margarita

Group 102 A

Checked by: Omarov B.B.

Taldykorgan 2011

Introduction

1. General information about atmospheric circulation

2. Factors that determine the general circulation of the atmosphere

3. Cyclones and anticyclones.

4. Winds affecting the general circulation of the atmosphere

5. Hair dryer effect

6. Scheme of the general circulation "Planet Machine"

Conclusion

List of used literature

Introduction

On the pages of scientific literature recently, the concept of general circulation of the atmosphere is often encountered, the meaning of which each specialist understands in his own way. This term is systematically used by specialists involved in geography, ecology, and the upper part of the atmosphere.

Increasing interest in the general circulation of the atmosphere is shown by meteorologists and climatologists, biologists and physicians, hydrologists and oceanologists, botanists and zoologists, and of course ecologists.

Not consensus whether the indicated scientific direction has emerged recently or research has been going on here for centuries.

Below are the definitions of the general circulation of the atmosphere, as a set of sciences, and the factors influencing it are listed.

A certain list of achievements is given: hypotheses, developments and discoveries that mark certain milestones in the history of this set of sciences and give a certain idea of ​​the range of problems and tasks considered by it.

The distinctive features of the general circulation of the atmosphere are described, as well as the simplest scheme of the general circulation called the "planetary machine" is presented.

1. General information about atmospheric circulation

The general circulation of the atmosphere (lat. Circulatio - rotation, Greek atmos - steam and sphaira - ball) is a set of large-scale air currents in the tropo- and stratospheres. As a result, there is an exchange of air masses in space, which contributes to the redistribution of heat and moisture.

The general circulation of the atmosphere is called the circulation of air on the globe, leading to its transfer from low latitudes to high latitudes and vice versa.

The general circulation of the atmosphere is determined by zones of high atmospheric pressure in the subpolar regions and tropical latitudes and zones of low pressure in temperate and equatorial latitudes.

The movement of air masses occurs both in latitudinal and meridional directions. In the troposphere, the circulation of the atmosphere includes trade winds, westerly air currents of temperate latitudes, monsoons, cyclones and anticyclones.

The reason for the movement of air masses is the unequal distribution of atmospheric pressure and the heating by the Sun of the surface of land, oceans, ice at different latitudes, as well as the deflecting effect on air flows of the Earth's rotation.

The main patterns of atmospheric circulation are constant.

In the lower stratosphere, jet streams of air in temperate and subtropical latitudes are predominantly western, and in tropical latitudes - eastern, and they go at a speed of up to 150 m / s (540 km / h) relative to the earth's surface.

In the lower troposphere, the prevailing directions of air transport differ in geographical zones.

In polar latitudes, easterly winds; in temperate - western with frequent disturbance by cyclones and anticyclones, trade winds and monsoons are most stable in tropical latitudes.

Due to the diversity of the underlying surface, regional deviations - local winds - appear on the form of the general circulation of the atmosphere.

2. Factors that determine the general circulation of the atmosphere

– uneven distribution solar energy over the earth's surface and, as a result, an uneven distribution of temperature and atmospheric pressure.

- Coriolis forces and friction, under the influence of which air flows acquire a latitudinal direction.

– The influence of the underlying surface: the presence of continents and oceans, the heterogeneity of the relief, etc.

The distribution of air currents in the earth's surface has a zonal character. In the equatorial latitudes - calm or weak variable winds are observed. The trade winds dominate the tropical zone.

The trade winds are constant winds blowing from 30 latitudes to the equator, having a northeasterly direction in the northern hemisphere, and a southeasterly direction in the southern hemisphere. At 30-35? With. and y.sh. - calm zone, so-called. "horse latitudes".

dominated in temperate latitudes westerly winds(southwest in the northern hemisphere, northwest in the south). In the polar latitudes, easterly (in the northern hemisphere northeast, in the southern hemisphere - southeast) winds blow.

In reality, the system of winds over the earth's surface is much more complicated. In the subtropical belt, the trade winds are disrupted in many areas by the summer monsoons.

In temperate and subpolar latitudes, cyclones and anticyclones have a great influence on the nature of air currents, and on the eastern and northern coasts - monsoons.

In addition, local winds are formed in many areas, due to the characteristics of the territory.

3. Cyclones and anticyclones.

The atmosphere is characterized by eddy movements, the largest of which are cyclones and anticyclones.

A cyclone is an ascending atmospheric vortex with low pressure in the center and a system of winds from the periphery to the center, directed against in the northern hemisphere, and clockwise in the southern hemisphere. Cyclones are divided into tropical and extratropical. Consider extratropical cyclones.

The diameter of extratropical cyclones is on average about 1000 km, but there are more than 3000 km. Depth (pressure in the center) - 1000-970 hPa or less. Strong winds blow in the cyclone, usually up to 10-15 m/s, but can reach 30 m/s and more.

The average speed of the cyclone is 30-50 km/h. Most often, cyclones move from west to east, but sometimes they move from the north, south, and even east. The zone of the greatest frequency of cyclones is the 80th latitude of the northern hemisphere.

Cyclones bring cloudy, rainy, windy weather, in summer - cooling, in winter - warming.

Tropical cyclones (hurricanes, typhoons) form in tropical latitudes; this is one of the most formidable and dangerous natural phenomena. Their diameter is several hundred kilometers (300-800 km, rarely more than 1000 km), but a large difference in pressure between the center and the periphery is characteristic, which causes strong hurricane-force winds, tropical showers, and severe thunderstorms.

An anticyclone is a descending atmospheric vortex with increased pressure in the center and a system of winds from the center to the periphery, directed clockwise in the northern hemisphere and counterclockwise in the southern hemisphere. The dimensions of anticyclones are the same as those of cyclones, but in the late stage of development they can reach up to 4000 km in diameter.

Atmospheric pressure in the center of anticyclones is usually 1020-1030 hPa, but can reach more than 1070 hPa. The highest frequency of anticyclones is over the subtropical zones of the oceans. Anticyclones are characterized by cloudy, rainless weather, with weak winds in the center, severe frosts in winter, and heat in summer.

4. Winds affecting the general circulation of the atmosphere

Monsoons. Monsoons are seasonal winds that change direction twice a year. In summer they blow from the ocean to the land, in winter - from the land to the ocean. The reason for the formation is the uneven heating of land and water in seasons. Depending on the zone of formation, monsoons are divided into tropical and extratropical.

Extratropical monsoons are especially pronounced on the eastern margin of Eurasia. The summer monsoon brings moisture and coolness from the ocean, while the winter monsoon blows from the mainland, lowering the temperature and humidity.

Tropical monsoons are most pronounced in the Indian Ocean basin. The summer monsoon blows from the equator, it is opposite to the trade wind and brings cloudiness, precipitation, softens the summer heat, winter - coincides with the trade wind, strengthens it, bringing dryness.

local winds. Local winds have a local distribution, their formation is associated with the characteristics of a given territory - the proximity of water bodies, the nature of the relief. The most common are breezes, bora, foehn, mountain-valley and katabatic winds.

Breezes (light wind-FR) - winds along the shores of the seas, large lakes and rivers, twice a day changing direction to the opposite: the daytime breeze blows from the reservoir to the shore, the night breeze - from the coast to the reservoir. Breezes are caused by the diurnal variation of temperature and, accordingly, pressure over land and water. They capture a layer of air 1-2 km.

Their speed is low - 3-5 m / s. A very strong daytime sea breeze is observed on the western desert coasts of the continents in tropical latitudes, washed by cold currents and cold water rising near the coast in the upwelling zone.

There it invades inland for tens of kilometers and produces a strong climatic effect: it lowers the temperature, especially in summer by 5-70 C, and in West Africa up to 100 C, increases relative humidity air up to 85%, contributes to the formation of fogs and dew.

Phenomena similar to daytime sea breezes can be observed along the outskirts big cities, where there is a circulation of colder air from the suburbs to the center, because over the cities there are "heat spots" throughout the year.

Mountain-valley winds have a daily periodicity: during the day the wind blows up the valley and along the mountain slopes, at night, on the contrary, the cooled air descends. The daytime air rise leads to the formation of cumulus clouds over the slopes of the mountains, at night, when the air descends and the air is adiabatically heated, the cloudiness disappears.

Glacial winds are cold winds that constantly blow from mountain glaciers down slopes and valleys. They are caused by the cooling of the air above the ice. Their speed is 5-7 m/s, their thickness is several tens of meters. They are more intense at night, as they are amplified by the slope winds.

General circulation of the atmosphere

1) Due to the tilt of the Earth's axis and the sphericity of the Earth, the equatorial regions receive more solar energy than the polar regions.

2) At the equator, the air heats up → expands → rises up → a low pressure area is formed. 3) At the poles, the air cools down → condenses → sinks down → a high pressure area forms.

4) Due to the difference in atmospheric pressure, air masses begin to move from the poles to the equator.

Wind direction and speed are also affected by:

• properties of air masses (humidity, temperature…)
• underlying surface (oceans, mountain ranges, etc.)
• rotation of the globe around its axis (Coriolis force) 1) a general (global) system of air currents above the earth's surface, the horizontal dimensions of which are commensurate with the continents and oceans, and the thickness is from several kilometers to tens of kilometers.

trade winds - These are constant winds blowing from the tropics to the equator.

The reason: the equator is always low pressure (updrafts) and the tropics are always high pressure (downdrafts).

Due to the action of the Coriolis force: the trade winds of the Northern Hemisphere have a northeasterly direction (deviate to the right)

Southern Hemisphere trade winds - southeast (deviate to the left)

Northeast winds(in the Northern Hemisphere) and southeast winds(in the southern hemisphere).
Reason: air flows move from the poles to temperate latitudes and, under the influence of the Coriolis force, deviate to the west. Western winds are winds that blow from the tropics to temperate latitudes, predominantly from west to east.

Reason: in the tropics there is high pressure, and in temperate latitudes it is low, so part of the air from the E.D. region moves into area H,D,. When moving under the influence of the Coriolis force, air currents deviate to the east.

Westerly winds bring warm and humid air to Estonia. air masses are formed over the waters of the warm North Atlantic Current.

The air in the cyclone moves from the periphery to the center;

In the central part of the cyclone, the air rises and

It cools, so clouds and precipitation form;

During cyclones, cloudy weather with strong winds prevails:

summer- rainy and cold
winter- with thaws and snowfalls.

Anticyclone is an area of ​​high atmospheric pressure with a maximum in the center.
air in an anticyclone moves from the center to the periphery; in the central part of the anticyclone, the air descends and heats up, its humidity drops, the clouds dissipate; with anticyclones, clear calm weather is established:

summer is hot

in winter it is frosty.

Atmospheric circulation

Definition 1

Circulation It is a system for the movement of air masses.

Circulation can be general on a planetary scale and local circulation that occurs over separate territories and water areas. Local circulation includes day and night breezes that occur on the coasts of the seas, mountain-valley winds, glacial winds, etc.

Local circulation at certain times and in certain places can be superimposed on the currents of the general circulation. With the general circulation of the atmosphere, huge waves and whirlwinds arise in it, which develop and move in different ways.

Such atmospheric disturbances are cyclones and anticyclones, which are characteristic features of the general circulation of the atmosphere.

As a result of the movement of air masses, which occurs under the action of centers of atmospheric pressure, the territories are provided with moisture. As a result of the fact that air movements of different scales simultaneously exist in the atmosphere, overlapping each other, atmospheric circulation is a very complex process.

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The movement of air masses on a planetary scale is formed under the influence of 3 main factors:

These factors complicate the general circulation of the atmosphere.

If the earth were uniform and not rotating around its axis - then the temperature and pressure at the earth's surface would correspond to thermal conditions and be of a latitudinal nature. This means that the decrease in temperature would occur from the equator to the poles.

With this distribution, warm air rises at the equator, while cold air sinks at the poles. As a result, it would accumulate at the equator in the upper part of the troposphere, and the pressure would be high, and at the poles it would be reduced.

At altitude, the air would flow in the same direction and lead to a decrease in pressure over the equator and its increase over the poles. The outflow of air near the earth's surface would occur from the poles, where the pressure is high towards the equator in the meridional direction.

It turns out that the thermal cause is the first cause of atmospheric circulation - different temperature leads to different pressure at different latitudes. In reality, pressure is low at the equator, and high at the poles.

On a uniform rotating Earth in the upper troposphere and lower stratosphere, the winds during their outflow to the poles in the northern hemisphere should deviate to the right, in the southern hemisphere - to the left and at the same time become westerly.

In the lower troposphere, winds flowing from the poles towards the equator and deviating would become easterly in the northern hemisphere, and southeasterly in the southern hemisphere. The second reason for the circulation of the atmosphere is clearly visible - dynamic. The zonal component of the general circulation of the atmosphere is due to the rotation of the Earth.

The underlying surface with an uneven distribution of land and water has a significant impact on the general circulation of the atmosphere.

Cyclones

The lower layer of the troposphere is characterized by eddies that appear, develop and disappear. Some vortices are very small and go unnoticed, while others have big influence on the planet's climate. First of all, this applies to cyclones and anticyclones.

Definition 2

Cyclone is a huge atmospheric vortex with low pressure in the center.

In the Northern Hemisphere, the air in the cyclone moves counterclockwise, in the Southern Hemisphere - clockwise. Cyclonic activity in middle latitudes is a feature of atmospheric circulation.

Cyclones arise due to the rotation of the Earth and the deflecting force of Coriolis, and in their development they go through stages from inception to filling. As a rule, the occurrence of cyclones occurs on atmospheric fronts.

Two air masses of opposite temperature, separated by a front, are drawn into a cyclone. Warm air at the interface intrudes into the cold air region and is deflected to high latitudes.

The balance is disturbed, and the cold air in the rear is forced to penetrate into low latitudes. There is a cyclonic bend of the front, which is a huge wave moving from west to east.

The wave stage is first stage cyclone development.

Warm air rises and slides over the frontal surface at the front of the wave. The resulting waves with a length of $1000$ km and more are unstable in space and continue to develop.

At the same time, the cyclone moves to the east at a speed of $100$ km per day, the pressure continues to fall, and the wind becomes stronger, the wave amplitude increases. it second stage– stage young cyclone.

On special maps, a young cyclone is outlined by several isobars.

With the advancement of warm air to high latitudes, a warm front forms, and the advancement of cold air to tropical latitudes forms cold front. Both fronts are part of a single whole. A warm front moves more slowly than a cold front.

If a cold front catches up with a warm front and merges with it, a occlusion front. Warm air rises and twists in a spiral. it third stage cyclone development - the stage of occlusion.

Fourth stage– its completion is final. There is a final pushing of warm air upwards and its cooling, temperature contrasts disappear, the cyclone becomes cold over its entire area, slows down its movement and finally fills up. From inception to filling, the life of a cyclone lasts from $5$ to $7$ days.

Remark 1

Cyclones bring cloudy, cool and rainy weather in summer and thaws in winter. Summer cyclones move at a speed of $400-$800 km per day, winter - up to $1000 km per day.

Anticyclones

Cyclonic activity is associated with the emergence and development of frontal anticyclones.

Definition 3

Anticyclone- This is a huge atmospheric vortex with high pressure in the center.

Anticyclones are formed in the rear of the cold front of a young cyclone in cold air and have their own stages of development.

There are only three stages in the development of an anticyclone:

General circulation of the atmosphere

The objects of study of the general circulation of the atmosphere are moving cyclones and anticyclones of temperate latitudes with their rapidly changing meteorological conditions: trade winds, monsoons, tropical cyclones, etc. Typical features of the general circulation of the atmosphere, stable in time or recurring more often than others, are revealed by averaging meteorological elements over long periods of time. long-term observation periods,

On fig. 8, 9 shows the average long-term wind distribution near the earth's surface in January and July. In January, i.e.

in winter, in the Northern Hemisphere, giant anticyclonic eddies are clearly visible over North America and a particularly intense eddy over Central Asia.

In summer, anticyclonic eddies over the land are destroyed due to the heating of the continent, and over the oceans, such eddies are significantly enhanced and propagate to the north.

Surface pressure in millibars and prevailing air currents

Due to the fact that in the troposphere the air in the equatorial and tropical latitudes is warmed up much more intensively than in the polar regions, the air temperature and pressure gradually decrease in the direction from the equator to the poles. As meteorologists say, the planetary gradient of temperature and pressure is directed in the middle troposphere from the equator to the poles.

(In meteorology, the gradient of temperature and pressure is taken in the opposite direction, compared to physics.) Air is a highly mobile medium. If the Earth did not rotate around its axis, then in the lower layers of the atmosphere the air would flow from the equator to the poles, and in the upper layers it would return back to the equator.

But the Earth rotates at an angular velocity of 2p/86400 radians per second. Air particles, moving from low latitudes to high latitudes, retain large linear velocities relative to the earth's surface, acquired at low latitudes, and therefore deviate as they move to the east. A west-east air transport is formed in the troposphere, which is reflected in Fig. ten.

However, such a correct regime of currents is observed only on maps of average values. "Snapshots" of air currents give very diverse, each time new, non-repeating positions of cyclones, anticyclones, air currents, zones of meetings of warm and cold air, i.e., atmospheric fronts.

Atmospheric fronts play big role in the general circulation of the atmosphere, since significant transformations of the energy of air masses from one type to another take place in them.

On fig. 10 schematically shows the position of the main frontal sections in the middle troposphere and near the earth's surface. FROM atmospheric fronts and frontal zones are associated with numerous weather phenomena.

Here, cyclonic and anticyclonic eddies are born, powerful clouds and precipitation zones are formed, and wind intensifies.

When an atmospheric front passes through a given point, a noticeable cooling or warming is usually clearly observed, and the whole character of the weather changes sharply. Interesting features are found in the structure of the stratosphere.

Planetary frontal zone in the middle troposphere

If heat is located in the troposphere near the equator; air masses, and at the poles - cold, then in the stratosphere, especially in the warm half of the year, the situation is just the opposite, at the poles the air is relatively warmer here, and at the equator it is cold.

The temperature and pressure gradients are directed in the opposite direction with respect to the troposphere.

The influence of the deflecting force of the Earth's rotation, which led to the formation of west-east transport in the troposphere, creates a zone of east-west winds in the stratosphere.

Average location of jet stream axes in the Northern Hemisphere in winter

The highest wind speeds and, consequently, the highest kinetic energy of air are observed in jet streams.

Figuratively speaking, jet streams are air rivers in the atmosphere, rivers flowing near the upper boundary of the troposphere, in the layers separating the troposphere from the stratosphere, i.e., in layers close to the tropopause (Fig. 11 and 12).

Wind speed in jet streams reaches 250 - 300 km/h - in winter; and 100 - 140 km / h - in summer. Thus, a low-speed aircraft, falling into such a jet stream, can fly "backward".

Average location of jet stream axes in the Northern Hemisphere in summer

The length of the jet streams reaches several thousand kilometers. Below the jet streams in the troposphere, there are wider and slower air "rivers" - planetary high-altitude frontal zones, which also play an important role in the general circulation of the atmosphere.

The occurrence of high wind speeds in jet streams and in planetary high-altitude frontal zones occurs due to the presence here big difference air temperature between neighboring air masses.

The presence of a difference in air temperature, or, as they say, "temperature contrast", leads to an increase in wind with height. The theory shows that this increase is proportional to the horizontal temperature gradient of the considered air layer.

In the stratosphere, due to the reversal of the meridional air temperature gradient, the intensity of jet streams decreases and they disappear.

Despite the great extent of planetary high-altitude frontal zones and jet streams, they, as a rule, do not encircle the entire globe, but end where horizontal temperature contrasts between air masses weaken. Most often and sharply, temperature contrasts are manifested in the polar front, which separates air from temperate latitudes from tropical air.

The position of the axis of the high-altitude frontal zone with a slight meridional exchange of air masses

Planetary high-altitude frontal zones and jet streams often occur in the polar front system. Although, on average, planetary high-altitude frontal zones have a direction from west to east, in specific cases, the direction of their axes is very diverse. Most often in temperate latitudes, they have a wave-like character. On fig.

13, 14 show the positions of the axes of the high-altitude frontal zones in cases of stable west-east transport and in cases of developed meridional exchange of air masses.

An essential feature of air currents in the stratosphere and mesosphere over the equatorial and tropical regions is the existence there of several layers of air with almost opposite directions of strong winds.

The emergence and development of this multilayer structure of the wind field changes here at certain, but not quite exactly coinciding, intervals of time, which can also serve as some prognostic sign.

If we add to this that the phenomenon of sharp warming in the polar stratosphere, which regularly occurs in winter, is in some way connected with the processes in the stratosphere occurring in tropical latitudes, and with the tropospheric processes of temperate and high latitudes, then it becomes clear how complex and whimsical the development of those atmospheric processes that directly affect the weather regime in temperate latitudes.

The position of the axis of the high-altitude frontal zone with a significant meridional exchange of air masses

Of great importance for the formation of large-scale atmospheric processes is the state of the underlying surface, especially the state of the upper active water layer of the World Ocean. The surface of the World Ocean is almost 3/4 of the entire surface of the Earth (Fig. 15).

sea ​​currents

Due to the high heat capacity and the ability to mix easily, ocean waters store heat for a long time during encounters with warm air in temperate latitudes and throughout the year in southern latitudes. The stored heat with sea currents is carried far to the north and warms nearby areas.

The heat capacity of water is several times greater than that of soil and rocks that make up the land. The heated water mass serves as a heat accumulator with which it supplies the atmosphere. At the same time, it should be noted that the land reflects the sun's rays much better than the surface of the ocean.

The surface of snow and ice reflects the sun's rays especially well; 80-85% of all solar radiation falling on the snow is reflected from it. The surface of the sea, on the contrary, absorbs almost all the radiation that falls on it (55-97%). As a result of all these processes, the atmosphere receives only 1/3 of all incoming energy directly from the Sun.

The remaining 2/3 of the energy it receives from the underlying surface heated by the Sun, primarily from the water surface. Heat transfer from the underlying surface to the atmosphere occurs in several ways. First, a large amount of solar heat is spent on the evaporation of moisture from the surface of the ocean into the atmosphere.

When this moisture condenses, heat is released, which heats the surrounding layers of air. Secondly, the underlying surface gives off heat to the atmosphere through turbulent (i.e., vortex, disordered) heat transfer. Thirdly, heat is transferred by thermal electromagnetic radiation. As a result of the interaction of the ocean with the atmosphere, important changes occur in the latter.

The layer of the atmosphere into which the heat and moisture of the ocean penetrates, in cases where cold air invades the warm ocean surface, reaches 5 km or more. In those cases when warm air invades the cold water surface of the ocean, the height to which the influence of the ocean extends does not exceed 0.5 km.

In cases of cold air intrusion, the thickness of its layer, which is affected by the ocean, depends primarily on the magnitude of the water-air temperature difference. If the water is warmer than the air, then powerful convection develops, i.e., disordered ascending air movements, which lead to the penetration of heat and moisture into the high layers of the atmosphere.

On the contrary, if the air is warmer than water, then convection does not occur and the air changes its properties only in the lowest layers. Over the warm Gulf Stream in the Atlantic Ocean, with the intrusion of very cold air, the heat transfer of the ocean can reach up to 2000 cal/cm2 per day and extends to the entire troposphere.

Warm air can lose 20-100 cal/cm2 per day over the cold ocean surface. The change in the properties of the air that hits a warm or cold oceanic surface occurs quite quickly - such changes can be noticed at a level of 3 or 5 km already a day after the start of the invasion.

What increments of air temperature can be as a result of its transformation (change) above the underlying water surface? It turns out that in the cold half-year the atmosphere over the Atlantic warms up by 6° on average, and sometimes it can warm up by 20° per day. The atmosphere can cool by 2-10° per day. It is estimated that in the north of the Atlantic Ocean, i.e.

where the most intense transfer of heat from the ocean to the atmosphere occurs, the ocean gives off 10-30 times more heat than it receives from the atmosphere. Naturally, the heat reserves in the ocean are replenished by the influx of warm oceanic waters from tropical latitudes. Air currents distribute the heat received from the ocean for thousands of kilometers. The warming effect of the oceans in winter leads to the fact that the difference in air temperature between the northeastern parts of the oceans and continents is 15-20° at latitudes of 45-60 ° near the earth's surface, and 4-5 ° in the middle troposphere. For example, the warming effect of the ocean on the climate of northern Europe has been well studied.

The northwestern part of the Pacific Ocean in winter is under the influence of the cold air of the Asian continent, the so-called winter monsoon, which propagates 1-2 thousand km deep into the ocean in the water layer and 3-4 thousand km in the middle troposphere (Fig. 16) .

Annual amounts of heat carried by sea currents

In summer, it is colder over the ocean than over the continents, so the air coming from the Atlantic Ocean cools Europe, and the air of the Asian continent warms Pacific Ocean. However, the picture described above is typical for average circulation conditions.

Day-to-day changes in the magnitude and in the direction of heat fluxes from the underlying surface to the atmosphere and back are very diverse and have a great influence on the change in the atmospheric processes themselves.

There are hypotheses according to which the features of the development of heat exchange between different parts of the underlying surface and the atmosphere determine the stable nature of atmospheric processes over long periods of time.

If the air warms up over the anomalously (above normal) water surface of one or another part of the World Ocean in the temperate latitudes of the Northern Hemisphere, then an area of ​​high pressure (baric ridge) is formed in the middle troposphere, along the eastern periphery of which the transfer of cold air masses from the Arctic begins, and in its western part - the transfer of warm air from tropical latitudes to the north. Such a situation can lead to the preservation of a long-term weather anomaly near the earth's surface in certain areas - dry and hot or rainy and cool in summer, frosty and dry or warm and snowy in winter. Cloudiness plays a very significant role in the formation of atmospheric processes by regulating the flow of solar heat to the earth's surface. Cloud cover significantly increases the proportion of reflected radiation and thereby reduces the heating of the earth's surface, which, in turn, affects the nature of synoptic processes. It turns out some kind of feedback: the nature of the circulation of the atmosphere affects the creation of cloud systems, and cloud systems, in turn, affect the change in circulation. We have listed only the most important of the studied "terrestrial" factors influencing the formation of weather and air circulation. The activity of the Sun plays a special role in the study of the causes of changes in the general circulation of the atmosphere. Here one should distinguish between changes in the circulation of air on the Earth in connection with changes in the total heat flux coming from the Sun to the Earth as a result of fluctuations in the value of the so-called solar constant. However, as recent studies show, in reality it is not a strictly constant value. The energy of the circulation of the atmosphere is continuously replenished due to the energy sent by the Sun. Therefore, if the total energy sent by the Sun fluctuates significantly, then this can affect the change in circulation and weather on Earth. This issue has not yet been sufficiently studied. As for the change in solar activity, it is well known that various disturbances arise on the surface of the Sun, sunspots, torches, floccules, prominences, etc. These disturbances cause temporary changes in the composition of solar radiation, the ultraviolet component and the corpuscular (i.e., consisting of charged particles, mainly protons) radiation from the Sun. Some meteorologists believe that the change in solar activity is associated with tropospheric processes in the Earth's atmosphere, that is, with the weather.

The latter statement needs more research, mainly due to the fact that the well-manifested 11-year cycle of solar activity is not clearly visible in the weather conditions on Earth.

It is known that there are whole schools of meteorologists-forecasters who quite successfully predict the weather in connection with changes in solar activity.

Wind and General Atmospheric Circulation

Wind is the movement of air from areas of higher air pressure to areas of lower pressure. The wind speed is determined by the difference in atmospheric pressure.

The influence of wind in navigation must be constantly taken into account, since it causes the ship to drift, storm waves, etc.
Due to uneven heating various parts Earth, there is a system of atmospheric currents on a planetary scale (the general circulation of the atmosphere).

The air flow consists of separate vortices randomly moving in space. Therefore, the wind speed, measured at any point, continuously changes with time. The greatest fluctuations in wind speed are observed in the surface layer. In order to be able to compare wind speeds, a height of 10 meters above sea level was taken as a standard height.

Wind speed is expressed in meters per second, wind strength - in points. The ratio between them is determined by the Beaufort scale.

Beaufort scale

Wind speed fluctuations are characterized by the gust coefficient, which is understood as the ratio of the maximum speed of gusts of wind to its average speed obtained over 5-10 minutes.
As the average wind speed increases, the gust factor decreases. At high wind speeds, the gust factor is approximately 1.2 - 1.4.

The trade winds are winds that blow all year in one direction in the zone from the equator to 35 ° N. sh. and up to 30 ° S sh. Stable in direction: in the northern hemisphere - northeast, in the south - southeast. Speed ​​- up to 6 m / s.

Monsoons are winds of temperate latitudes that blow from the ocean to the mainland in summer and from the mainland to the ocean in winter. Reach speeds of 20 m/s. Monsoons bring dry, clear and cold weather to the coast in winter, cloudy in summer, with rain and fog.

Breezes are caused by uneven heating of water and land during the day. In the daytime, there is a wind from the sea to the land (sea breeze). At night from the chilled coast - to the sea (coastal breeze). Wind speed 5 - 10 m/s.

Local winds arise in certain areas due to the features of the relief and differ sharply from the general air flow: they arise as a result of uneven heating (cooling) of the underlying surface. Detailed information about local winds is given in sailing directions and hydrometeorological descriptions.

Bora is a strong and gusty wind that blows down a mountainside. Brings a significant chill.

It is observed in areas where a low mountain range borders the sea, during periods when atmospheric pressure increases over land and the temperature drops compared to pressure and temperature over the sea.

In the area of ​​Novorossiysk Bay, bora acts in November - March with average wind speeds of about 20 m/s (individual gusts can be 50 - 60 m/s). The duration of action is from one to three days.

Similar winds are observed on Novaya Zemlya, on the Mediterranean coast of France (mistral) and off the northern shores of the Adriatic Sea.

Sirocco - hot and humid wind of the central part mediterranean sea accompanied by cloudiness and precipitation.

Tornadoes are whirlwinds over the sea with a diameter of up to several tens of meters, consisting of water spray. They exist up to a quarter of a day and move at a speed of up to 30 knots. The wind speed inside the tornado can reach up to 100 m/s.

Storm winds occur mainly in areas with low atmospheric pressure. Especially great strength reach tropical cyclones, in which the wind speed often exceeds 60 m/s.

Strong storms are also observed in temperate latitudes. When moving, warm and cold air masses inevitably come into contact with each other.

The transition zone between these masses is called an atmospheric front. The passage of the front is accompanied by a sharp change in the weather.

The atmospheric front can be in a stationary state or in motion. Distinguish warm, cold fronts, as well as fronts of occlusion. The main atmospheric fronts are: arctic, polar and tropical. On synoptic maps, fronts are depicted as lines (front line).

A warm front is formed when warm air masses push against cold air masses. On weather maps, a warm front is marked with a solid line with semicircles along the front, indicating in the direction of colder air and the direction of movement.

As the warm front approaches, pressure begins to drop, clouds thicken, and heavy precipitation falls. In winter, when the front passes, low stratus clouds usually appear. The temperature and humidity of the air are slowly rising.

When a front passes, temperature and humidity usually increase rapidly, and the wind increases. After the passage of the front, the direction of the wind changes (the wind turns clockwise), the pressure drop stops and its weak growth begins, the clouds dissipate, and precipitation stops.

A cold front is formed when cold air masses advance on warmer ones (Fig. 18.2). On weather maps, a cold front is shown as a solid line with triangles along the front pointing toward more warm temperatures and direction of movement. The pressure in front of the front falls strongly and unevenly, the ship enters the zone of showers, thunderstorms, squalls and strong waves.

An occluded front is a front formed by the confluence of warm and cold fronts. Represented by a solid line with alternating triangles and semicircles.

Warm front section

cold front section

A cyclone is an atmospheric vortex of huge (hundreds to several thousand kilometers) diameter with reduced air pressure in the center. Air in a cyclone circulates counterclockwise in the northern hemisphere and clockwise in the southern.

There are two main types of cyclones - extratropical and tropical.

The first are formed in temperate or polar latitudes and have a diameter of thousands of kilometers at the beginning of development, and up to several thousand in the case of the so-called central cyclone.

A tropical cyclone is a cyclone formed in tropical latitudes; it is an atmospheric vortex with reduced atmospheric pressure in the center with storm wind speeds. Formed tropical cyclones move along with air masses from east to west, while gradually deviating to high latitudes.

Such cyclones are also characterized by the so-called. "eye of the storm" - the central area with a diameter of 20 - 30 km with relatively clear and calm weather. About 80 tropical cyclones are observed annually in the world.

View of the cyclone from space

Tropical cyclone paths

In the Far East and Southeast Asia, tropical cyclones are called typhoons (from the Chinese tai feng - big wind), and in North and South America- hurricanes (Spanish huracán named after the Indian god of the wind).
It is generally accepted that a storm turns into a hurricane at a wind speed of more than 120 km / h, at a speed of 180 km / h a hurricane is called a strong hurricane.

7. Wind. General circulation of the atmosphere

Lecture 7. Wind. General circulation of the atmosphere

Wind – this is the movement of air relative to the earth's surface, in which the horizontal component predominates. When an upward or downward wind movement is considered, the vertical component is also taken into account. The wind is characterized direction, speed and gust.

The reason for the occurrence of wind is the difference in atmospheric pressure at different points, determined by the horizontal baric gradient. The pressure is not the same, primarily due to the different degrees of heating and cooling of the air, and decreases with height.

To represent the distribution of pressure on the surface of the globe, pressure is applied to geographical maps, measured at the same time at different points and reduced to the same height (for example, to sea level). Points with the same pressure are connected by lines - isobars.

In this way, areas of increased (anticyclones) and low (cyclones) pressure are identified, as well as the direction of their movement for weather forecasting. Isobars can be used to determine how much pressure changes with distance.

In meteorology, the concept horizontal baric gradient is the change in pressure per 100 km along a horizontal line perpendicular to the isobars from high pressure to low pressure. This change is usually 1-2 hPa/100 km.

The movement of air occurs in the direction of the gradient, but not in a straight line, but more complicated, due to the interaction of forces that deflect the air due to the rotation of the earth and friction. Under the influence of the Earth's rotation, the air movement deviates from the baric gradient to the right in the northern hemisphere, to the left in the southern hemisphere.

The largest deviation is observed at the poles, and at the equator it is close to zero. The friction force reduces both the wind speed and the deviation from the gradient as a result of contact with the surface, as well as inside the air mass due to different speeds in the layers of the atmosphere. The combined influence of these forces deviates the wind from the gradient over land by 45-55o, over the sea - by 70-80o.

With an increase in altitude, the wind speed and its deviation increase up to 90 ° at a level of about 1 km.

Wind speed is usually measured in m / s, less often - in km / h and points. The direction is taken from where the wind blows, determined in rhumbs (there are 16 of them) or angular degrees.

Used for wind observations vane, which is installed at a height of 10-12 m. A hand-held anemometer is used for short-term observations of the speed in field experiments.

Anemorumbometer allows you to remotely measure the direction and speed of the wind , anemorumbograph continuously records these indicators.

The diurnal variation of wind speed over the oceans is almost not observed and is well pronounced over land: at the end of the night - a minimum, in the afternoon - a maximum. The annual course is determined by the laws of the general circulation of the atmosphere and differs in regions of the globe. For example, in Europe in summer - the minimum wind speed, in winter - the maximum. In Eastern Siberia, the opposite is true.

Wind direction in specific location changes often, but if we take into account the frequency of winds of different points, we can determine that some are more frequent. For such a study of directions, a graph called the wind rose is used. On each straight line of all points, the observed number of wind events for the desired period is plotted and the obtained values ​​\u200b\u200bare connected on the points with lines.

The wind contributes to maintaining the constancy of the gas composition of the atmosphere, mixing the air masses, transports moist sea air deep into the continents, providing them with moisture.

The adverse effect of wind for agriculture can be manifested in increased evaporation from the soil surface, causing drought, and wind erosion of soils is possible at high wind speeds.

The speed and direction of the wind must be taken into account when pollinating fields with pesticides, when irrigating with sprinklers. The direction of the prevailing winds must be known when laying forest belts, snow retention.

local winds.

The local winds are called winds that are characteristic only for certain geographical areas. They are of particular importance in their influence on weather conditions, their origin is different.

breezes – winds near the coastline of the seas and large lakes, which have a sharp diurnal change in direction. Happy sea ​​breeze blows ashore from the sea, and at night - coastal breeze blows from land to sea (Fig. 2).

They are pronounced in clear weather during the warm season, when the overall air transport is weak. In other cases, for example, during the passage of cyclones, breezes can be masked by stronger currents.

Wind movement during breezes is observed at a distance of several hundred meters (up to 1-2 km), with average speed 3 - 5 m / s, and in the tropics - and more, penetrating tens of kilometers deep into land or sea.

The development of breezes is associated with the diurnal variation of land surface temperature. During the day, the land heats up more than the surface of the water, the pressure above it becomes lower and air is transferred from the sea to the land. At night, the land cools faster and stronger, air is transferred from land to sea.

The daytime breeze lowers the temperature and increases the relative humidity, which is especially pronounced in the tropics. For example, in West Africa, when sea air moves to land, the temperature can decrease by 10 ° C or more, and relative humidity can increase by 40%.

Breezes are also observed on the shores of large lakes: Ladoga, Onega, Baikal, Sevan, etc., as well as on large rivers. However, in these areas the breezes are smaller in their horizontal and vertical development.

Mountain valley winds are observed in mountain systems mainly in summer and are similar to breezes in their daily periodicity. During the day, they blow up the valley and along the slopes of the mountains as a result of heating by the sun, and at night, when cooled, the air flows down the slopes. Nighttime air movement can cause frost, which is especially dangerous in the spring when gardens are in bloom.

Föhn –warm and dry wind blowing from the mountains to the valleys. At the same time, the temperature of the air rises significantly and its humidity drops, sometimes very quickly. They are observed in the Alps, in the Western Caucasus, on the southern coast of Crimea, in the mountains of Central Asia, Yakutia, on the eastern slopes of the Rocky Mountains and in other mountain systems.

Foehn is formed when an air current crosses a ridge. Since a vacuum is created on the leeward side, the air is sucked down in the form of a downward wind. The descending air heats up according to the dry adiabatic law: by 1°C for every 100 m of descent.

For example, if at an altitude of 3000 m the air had a temperature of -8o and a relative humidity of 100%, then, having descended into the valley, it would heat up to 22o, and the humidity would decrease to 17%. If the air rises up the windward slope, then water vapor condenses and clouds form, precipitation falls, and the descending air will be even drier.

The duration of hair dryers is from several hours to several days. A hair dryer can cause intense snowmelt and floods, dries up soils and vegetation until they die.

Bora–it is a strong, cold, gusty wind that blows from low mountain ranges towards warmer seas.

Bora is best known in the Novorossiysk Bay of the Black Sea and on the Adriatic coast near the city of Trieste. Similar to boron in origin and manifestation north in the region of

Baku, mistral on the Mediterranean coast of France, northser in the Gulf of Mexico.

Bora occurs when cold air masses pass through the coastal ridge. The air flows down under the force of gravity, developing a speed of more than 20 m / s, while the temperature is greatly reduced, sometimes by more than 25 ° C. Bora fades a few kilometers from the coast, but sometimes it can capture a significant part of the sea.

In Novorossiysk, bora is observed about 45 days a year, more often from November to March, with a duration of up to 3 days, rarely up to a week.

General circulation of the atmosphere

General circulation of the atmosphere– it is a complex system of large air currents that carry very large masses of air over the globe.

In the atmosphere near the earth's surface in polar and tropical latitudes, eastward transport is observed, in temperate latitudes - westward.

The movement of air masses is complicated by the rotation of the Earth, as well as by the relief and the influence of areas of high and low pressure. The deviation of the winds from the prevailing directions is up to 70o.

In the process of heating and cooling of huge masses of air over the globe, areas of high and low pressure are formed, which determine the direction of planetary air currents. Based on long-term average values ​​of pressure at sea level, the following regularities were revealed.

On both sides of the equator there is a low pressure zone (in January - between 15o north latitude and 25o south latitude, in July - from 35o north latitude to 5o south latitude). This area, called equatorial depression, extends more to the hemisphere where it is summer in a given month.

In the direction to the north and south of it, the pressure increases and maximum values reaches in subtropical zones high blood pressure(in January - at 30 - 32o north and south latitude, in July - at 33-37o N and 26-30o S). From the subtropics to temperate zones pressure drops, especially significantly in the southern hemisphere.

The minimum pressure is in two subpolar low pressure zones(75-65o N and 60-65o S). Further towards the poles, the pressure increases again.

In accordance with pressure changes, the meridional baric gradient is also located. It is directed from the subtropics on the one hand - to the equator, on the other - to subpolar latitudes, from the poles to subpolar latitudes. This is consistent with the zonal direction of the winds.

Over the Atlantic, Pacific and Indian Oceans very often northeast and southeast winds blow - trade winds. Western winds in the southern hemisphere, at latitudes of 40-60o, go around the entire ocean.

In the northern hemisphere, at temperate latitudes, westerly winds are constantly expressed only over the oceans, and over the continents, the directions are more complicated, although westerlies also predominate.

East winds of the polar latitudes are clearly observed only along the outskirts of Antarctica.

In the south, east and north of Asia, there is a sharp change in the direction of the winds from January to July - these are areas monsoons. The causes of monsoons are similar to those of breezes. In summer, the mainland of Asia heats up strongly and an area of ​​low pressure spreads over it, where air masses rush from the ocean.

The resulting summer monsoon causes large amounts of precipitation, often showers. In winter, high pressure sets in over Asia due to the more intense cooling of the land, compared to the ocean, and cold air moves to the ocean, forming a winter monsoon with clear, dry weather. Monsoons penetrate more than 1000 km in a layer above land up to 3-5 km.

Air masses and their classification.

air mass- this is a very large amount of air, which covers an area of ​​​​millions of square kilometers.

In the process of general circulation of the atmosphere, the air is divided into separate air masses, which remain for a long time over a vast territory, acquire certain properties and cause various types of weather.

Moving to other regions of the Earth, these masses bring with them their own weather regime. The predominance of air masses of a certain type (types) in a particular area creates a characteristic climatic regime of the area.

The main differences between air masses are: temperature, humidity, cloudiness, dustiness. For example, in summer the air over the oceans is more humid, colder, cleaner than over land at the same latitude.

The longer the air is over one area, the more it undergoes changes, so air masses are classified according to geographical areas where they formed.

There are main types: 1) arctic (antarctic), which move from the poles, from high pressure zones; 2) temperate latitudes“polar” – in the northern and southern hemispheres; 3) tropical- move from the subtropics and tropics to temperate latitudes; four) equatorial- formed over the equator. In each type, marine and continental subtypes are distinguished, differing primarily in temperature and humidity within the type. The air, being in constant motion, passes from the area of ​​formation to the neighboring ones and gradually changes its properties under the influence of the underlying surface, gradually turning into a mass of another type. This process is called transformation.

cold air masses are called those that move to a warmer surface. They cause a chill in the areas where they come.

When they move, they themselves warm up from the earth's surface, so large vertical temperature gradients arise inside the masses and convection develops with the formation of cumulus and cumulonimbus clouds and heavy rainfall.

Air masses moving to a colder surface are called warm masses. They bring warmth, but they themselves are cooled from below. Convection does not develop in them and stratus clouds predominate.

Neighboring air masses are separated from each other by transition zones, which are strongly inclined to the Earth's surface. These zones are called fronts.