The movement of air masses in the atmosphere. Seas and oceans, mountains and plains

The atmosphere is not uniform. In its composition, especially near 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 move 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 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). Air has very low temperatures, low moisture content. The intrusion of KAV on the mainland causes a strong cooling at 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. It's air 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 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 (cT) is formed over land, characterized by high temperatures, dryness and dustiness. Marine tropical air (mTw) is formed over tropical waters ( tropical zones ocean), 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.

The air masses are in continuous movement. 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.

The movement of air masses

All of Earth's air circulates continuously between the equator and the poles. The air heated at the equator rises, is divided into two parts, one part begins to move towards the north pole, the other part - towards the south pole. As it reaches the poles, the air cools. At the poles, it twists and falls down.

Figure 1. The principle of swirling air

It turns out two huge vortices, each of which covers the whole hemisphere, the centers of these vortices are located at the poles.
Having descended at the poles, the air begins to move back towards the equator; at the equator, the heated air rises. Then again moves to the poles.
In the lower layers of the atmosphere, the movement is somewhat more complicated. In the lower layers of the atmosphere, air from the equator, as usual, begins to move towards the poles, but at the 30th parallel it falls down. One part of it returns to the equator, where it rises again, the other part, having dropped down at the 30th parallel, continues to move towards the poles.

Figure 2. Northern hemisphere air movement

Wind concept

Wind - the movement of air relative to the earth's surface (the horizontal component of this movement), sometimes they speak of an ascending or descending wind, taking into account its vertical component.

Wind speed

Estimation of wind speed in points, the so-called Beaufort scale, according to which the entire range of possible wind speeds is divided into 12 gradations. This scale relates the strength of the wind to its various effects, such as the degree of sea roughness, the swaying of branches and trees, the spread of smoke from chimneys, and so on. Each gradation on the Beaufort scale has a specific name. So, zero of the Beaufort scale corresponds to calm, i.e. complete lack of wind. A wind of 4 points, according to Beaufort, is called moderate and corresponds to a speed of 5–7 m / s; at 7 points - strong, at a speed of 12-15 m / s; at 9 points - by a storm, at a speed of 18-21 m / s; finally, a wind of 12 Beaufort points is already a hurricane, at a speed of over 29 m / s . Near the earth's surface, you most often have to deal with winds whose speeds are of the order of 4–8 m/s and rarely exceed 12–15 m/s. But nevertheless, in storms and hurricanes of temperate latitudes, speeds can exceed 30 m/s, and in some gusts reach 60 m / s. In tropical hurricanes, wind speeds reach up to 65 m / s, and individual gusts - up to 100 m / s. In small-scale eddies (tornadoes, blood clots), speeds of more than 100 m / s are possible. currents in the upper troposphere and lower stratosphere average speed wind for a long time and over a large area can reach up to 70-100 m / s . The wind speed near the earth's surface is measured by anemometers of various designs. Instruments for measuring wind at ground stations are installed at a height of 10–15 m above the earth's surface.

Table 1. WIND POWER.
Beaufort scale for determining wind strength
Points	Visual signs on land	Wind speed, km/h	Terms that define the strength of the wind
	Calmly; smoke rises vertically	Less than 1.6	Calm
	The direction of the wind is noticeable by the deviation of the smoke, but not by the weather vane	1,6–4,8	Quiet
	The wind is felt by the skin of the face; leaves rustle; turning ordinary weathervanes	6,4–11,2	Easy
	Leaves and small twigs are in constant motion; waving light flags	12,8–19,2	Weak
	The wind raises dust and papers; thin branches sway	20,8–28,8	Moderate
	The leafy trees sway; ripples appear on land	30,4–38,4	Fresh
	Thick branches sway; the whistle of the wind is heard in the electric wires; hard to hold an umbrella	40,0–49,6	Strong
	Tree trunks sway; hard to go against the wind	51,2–60,8	Strong
	Tree branches break; almost impossible to go against the wind	62,4–73,6	Very strong
	Minor damage; the wind rips smoke hoods and tiles off the roofs	75,2–86,4	Storm
	Rarely on dry land. Trees are uprooted. Significant damage to buildings	88,0–100,8	Heavy storm
	It is very rare on dry land. Accompanied by destruction over a large area	102,4–115,2	Violent storm
	Severe destruction (Scores 13-17 were added by the US Weather Bureau in 1955 and are used in the US and UK scales)	116,8–131,2	Hurricane
	132,8–147,2
	148,8–164,8
	166,4–182,4
	184,0–200,0
	201,6–217,6

Direction of the wind

Wind direction refers to the direction from which it blows. You can indicate this direction by naming either the point on the horizon from where the wind blows, or the angle formed by the direction of the wind with the meridian of the place, i.e. its azimuth. In the first case, eight main points of the horizon are distinguished: north, northeast, east, southeast, south, southwest, west, northwest. And eight intermediate points between them: north-northeast, east-northeast, east-southeast, south-southeast, south-southwest, west-southwest, west-northwest, north -northwest. The sixteen points indicating the direction from which the wind is blowing have abbreviations:

Table 2. ABBREVIATED ROOMS
FROM	N	IN	E	YU	S		W
CCB	NNE	SEW	ESE	SSW	SSW	ZSZ	WNW
CB	NE	SE	SE	SW	SW	NW	NW
BCB	ENE	SSE	SSE	SW	WSW	CVD	NNW
N - north, E - east, S - south, W - west

Atmospheric circulation

Atmospheric circulation - meteorological observations of the state of the air shell the globe- atmospheres - show that it is not at rest at all: with the help of weather vanes and anemometers, we constantly observe in the form of wind the transfer of air masses from one place to another. The study of winds in different parts of the globe has shown that the movements of the atmosphere in those lower layers that are accessible to our observation are of a very different nature. There are places where the phenomena of the wind, as well as other features of the weather, have a very pronounced character of stability, a known desire for constancy. In other regions, however, the winds change their character so quickly and often, their direction and strength change so sharply and suddenly, as if there were no law in their rapid changes. With the introduction of the synoptic method for studying non-periodic weather changes, however, it became possible to notice some connection between the distribution of pressure and the movements of air masses; further theoretical studies by Ferrel, Guldberg and Mohn, Helmholtz, Bezold, Oberbeck, Sprung, Werner Siemens and other meteorologists explained where and how air flows arise and how they are distributed over the earth's surface and in the mass of the atmosphere. A careful study of meteorological maps depicting the state of the lower layer of the atmosphere - the weather at the very surface of the earth, showed that the pressure of the atmosphere is distributed over the earth's surface rather unevenly, usually in the form of areas with lower or higher pressure than in the surrounding area; according to the system of winds that arise in them, these areas are real atmospheric vortices. Areas of low pressure are commonly referred to as barometric lows, barometric depressions, or cyclones; areas high blood pressure are called barometric maxima or anticyclones. All the weather in the area they occupy is closely related to these regions, which differs sharply for regions of low pressure from the weather in regions of relatively high pressure. Moving along the earth's surface, the mentioned regions also carry with them their characteristic weather, and by their movements cause its non-periodic changes. Further study of these and other areas led to the conclusion that these types of distribution atmospheric pressure can still have a different character in terms of the ability to maintain their existence and change their position on the earth's surface, differ in very different stability: there are barometric minima and maxima, temporary and permanent. While the first ones - vortices - are temporary and do not show sufficient stability and more or less quickly change their place on the earth's surface, either intensifying or weakening and, finally, completely disintegrating in relatively short periods of time, areas of constant maxima and minima have extremely high stability and for a very long time kept, without significant changes, in the same place. Of course, the stability of the weather and the nature of the air currents in the area they occupy are closely related to the different stability of these regions: constant highs and lows will correspond to both constant, stable weather and a definite, unchanging system of winds that stay in their place for months; temporary whirlwinds, with their rapid, constant movements and changes, cause extremely changeable weather and a very unstable wind system for a given area. Thus, in the lower layer of the atmosphere, near the earth's surface, the movements of the atmosphere are distinguished by great diversity and complexity, and, moreover, they do not always and everywhere possess sufficient stability, especially in those regions where vortices of a temporary nature predominate. What will be the movements of the masses of air in somewhat higher layers of the atmosphere, ordinary observations do not say anything; only observations of the movements of clouds allow us to think that there - at a certain height above the surface of the earth, all movements of air masses in general are somewhat simplified, are more definite and more uniform. And yet there is no shortage of facts pointing to the enormous influence high strata atmosphere on the weather in the lower layers: it is sufficient, for example, to point out that the direction of movement of time vortices is, apparently, in direct proportion to the movement of high layers of the atmosphere. Therefore, even before science began to have a sufficient number of facts to solve the problem of the movements of the high layers of the atmosphere, there were already some theories that tried to combine all the individual observations on movements lower layers air and create a general scheme for the C. atmosphere; such, for example, was Maury's theory of the atmospheric atmosphere. But, until a sufficient number of facts were collected, until the relationship between the air pressure at given points and its movements was completely clarified, until then such theories, based more on hypotheses than on actual data, could not give a real idea of \u200b\u200bthat what actually can and does happen in the atmosphere. Only towards the end of the last XIX century. enough facts were accumulated for this, and the dynamics of the atmosphere was developed to such an extent that it became possible to give a real, and not a guessing, picture of the central atmosphere. The honor of solving the problem of the general circulation of air masses in the atmosphere belongs to the American meteorologist William Ferrel- a solution so general, complete and true that all later researchers in this field only developed details or made further additions to Ferrel's main ideas. The main cause of all movements in the atmosphere is the uneven heating of various points on the earth's surface by the sun's rays. The unevenness of heating entails the appearance of a pressure difference over differently heated points; and the result of the difference in pressure will always and invariably be the movement of masses of air from places of higher to places of more low pressure. Therefore, due to the strong heating of the equatorial latitudes and the very low temperature of the polar countries in both hemispheres, the air adjacent to the earth's surface must begin to move. If, according to available observations, we calculate the average temperatures of different latitudes, then the equator will turn out to be on average 45 ° warmer than the poles. To determine the direction of motion, it is necessary to trace the distribution of pressure on the earth's surface and in the mass of the atmosphere. In order to exclude the uneven distribution of land and water over the earth's surface, which greatly complicates all calculations, Ferrel made the assumption that both land and water are evenly distributed along parallels, and calculated the average temperatures of various parallels, the decrease in temperature as it rises to a certain height above the earth's surface and pressure at the bottom; and then, from these data, he already calculated the pressure at some other heights. The next small table presents the result of Ferrel's calculations and gives the distribution of pressure on average over latitudes on the surface of the earth and at altitudes of 2000 and 4000 m.

Table 3. PRESSURE DISTRIBUTION BY LATITUDE ON THE EARTH'S SURFACE AND AT 2000 AND 4000 M
	Average pressure in the Northern Hemisphere
At latitude:	80 ○	70 ○	60 ○	50 ○	40 ○	30 ○	20 ○	10 ○
At sea level	760,5	758,7	758,7	760,07	762,0	761,7	759,2	757,9
At an altitude of 2000 m	582,0	583,6	587,6	593,0	598,0	600,9	600,9	600,9
At an altitude of 4000 m	445,2	446,6	451,9	457,0	463,6	468,3	469,9	470,7
	Average pressure in the southern hemisphere
At latitude:	(equator)	10 ○	20 ○	30 ○	40 ○	50 ○	60 ○	70 ○
At sea level	758,0	759,1	761,7	763,5	760,5	753,2	743,4	738,0
At an altitude of 2000 m	601,1	601,6	602,7	602,2	597,1	588,0	577,0	569,9
At an altitude of 4000 m	471,0	471,1	471,1	469,3	463,1	453,7	443,9	437,2

If we leave aside for the time being the lowest layer of the atmosphere, where the distribution of temperature, pressure, and also currents is very uneven, then at a certain height, as can be seen from the tablet, due to the ascending current of heated air near the equator, we find over this last increased pressure, uniformly decreasing towards the poles and here reaching its smallest value. With such a distribution of pressure at these heights above the earth's surface, a grandiose flow should form, covering the whole hemisphere and relating the masses of warm, heated air rising near the equator to centers of low pressure, to the poles. If we also take into account the deflecting action of the centrifugal force resulting from the daily rotation of the earth around its axis, which should deviate any moving body to the right from its original direction in the northern hemispheres, to the left in the southern hemispheres, then at the heights in question in each hemisphere, the resulting flow will turn, obviously , into a huge whirlwind, carrying air masses in the direction from the southwest to the northeast in the northern hemisphere, from the northwest to the southeast - in the southern hemisphere.

Observations on the movement of cirrus clouds and others confirm these theoretical conclusions. As the circles of latitudes narrow, approaching the poles, the speed of movement of air masses in these whirlwinds will increase, but up to a certain limit; then it becomes more permanent. Near the pole, the inflowing air masses should sink down, giving way to the newly inflowing air, forming a downward flow, and then should flow downwards back to the equator. Between the two streams there must be at some height a neutral layer of air at rest. Below, however, correct transfer masses of air from the poles to the equator are not observed: the preceding plate shows that in the lower layer of air the pressure of the atmosphere will be the highest at the bottom, not at the poles, as it should be with the correct distribution corresponding to the upper one. highest pressure in the lower layer it falls to a latitude of about 30°-35° in both hemispheres; therefore, from these centers of high pressure lower reaches will be directed both to the poles and to the equator, forming two separate systems of winds. The reason for this phenomenon, also theoretically explained by Ferrel, is as follows. It turns out that at a certain height above the earth's surface, depending on the change in the latitude of the place, the magnitude of the gradient and the coefficient of friction, the meridional component of the velocity of air masses can drop to 0. This is precisely what happens at latitudes of approx. 30°-35°: here, at a certain height, not only for this reason there is no movement of air towards the poles, but even due to its continuous inflow from the equator and from the poles, its accumulation, which leads to an increase in pressure below in these latitudes . Thus, at the very surface of the earth in each hemisphere, as already mentioned, two systems of currents arise: from 30 ° to the poles, winds blow, directed on average from southwest to northeast in the northern, from northwest to southeast in the southern hemisphere; from 30° to the equator, winds blow from NE to SW in the northern hemisphere, from SE to NW in the southern hemisphere. These last two systems of winds blowing in both hemispheres between the equator and a latitude of 31° form, as it were, a wide ring separating both grandiose vortices in the lower and middle layers of the atmosphere, carrying air from the equator to the poles (see also Atmospheric Pressure). Where ascending and descending air currents are formed, lulls are observed; such is precisely the origin of the equatorial and tropical zones of silence; a similar belt of silence must, according to Ferrel, also exist at the poles.

Where, however, does the reverse flow of air, spreading from the poles to the equator along the bottom, go? But it must be taken into account that, as one moves away from the poles, the dimensions of the circles of latitudes, and, consequently, the areas of belts of equal width occupied by the spreading air masses, increase rapidly; that the speed of the streams must rapidly decrease in inverse proportion to the increase in these areas; that at the poles, finally, the air, which is very rarefied in the upper layers, finally descends from above, the volume of which decreases very quickly as the pressure increases downwards. All these reasons fully explain why it is difficult, and even directly impossible, to keep track of these reverse lower currents at some distance from the poles. This is, in general terms, the scheme of the general circulating atmosphere, assuming a uniform distribution of land and water along the parallels, given by Ferrel. Observations fully confirm it. Only in the lower layer of the atmosphere will air currents, as Ferrel himself points out, be much more complicated than this scheme precisely because of the uneven distribution of land and water, and the unevenness of their heating by the rays of the sun and their cooling in the absence or decrease in insolation; mountains and hills also have a significant effect on the movement of the lowest layers of the atmosphere.

A careful study of the displacements of the atmosphere near the earth's surface shows in general that vortex systems represent the main form of such displacements. Starting with grandiose whirlwinds, embracing, according to Ferrel, each whole hemisphere, whirlwinds, how can they be called first order, near the earth's surface one has to observe successively decreasing in size vortex systems, up to and including elementary small and simple vortices. As a result of the interaction of flows different in their velocities and directions in the region of first-order vortices, near the earth's surface, second order vortices- the constant and temporary barometric maxima and minima mentioned at the beginning of this article, representing in their origin, as it were, a derivative of the previous vortices. The study of the formation of thunderstorms led A. V. Klossovsky and other researchers to the conclusion that these phenomena are nothing more than similar in structure, but incomparably smaller in size compared to the previous ones, vortices of the third order. These eddies seem to arise on the outskirts of barometric minima (second-order eddies) in exactly the same way as around a large depression formed on the water by an oar, which we row when sailing a boat, small, very quickly spinning and disappearing whirlpools are formed. In exactly the same way, second-order barometric minima, which are powerful air circulations, during their movement form smaller air circulations, which, in comparison with the minimum that forms them, have very small dimensions.

If these whirlwinds are accompanied by electrical phenomena, which can often be caused by the corresponding conditions of temperature and humidity in the air flowing to the center of the barometric minimum from below, then they appear in the form of thunderstorm whirlwinds, accompanied by the usual phenomena of electrical discharge, thunder and lightning. If the conditions are not favorable for the development of thunderstorm phenomena, we observe these third-order vortices in the form of rapidly passing storms, squalls, showers, etc. There is, however, every reason to think that these three categories, so different in scale of the phenomenon, vortex atmospheres are not exhausted. The structure of tornadoes, blood clots, and other phenomena shows that in these phenomena we are also dealing with real whirlwinds; but the size of these vortices of the fourth order even less, even more insignificant than the storm whirlwinds. The study of the movements of the atmosphere leads us, therefore, to the conclusion that the movements of air masses take place predominantly, if not exclusively, by the generation of vortices. Arising under the influence of purely thermal conditions, vortices of the first order, covering each entire hemisphere, give rise to vortices of smaller sizes near the earth's surface; these, in turn, are the cause of even smaller eddies. There is a kind of gradual differentiation of larger vortices into smaller ones; but the basic character of all these vortex systems remains exactly the same, from the largest to the smallest in size, even in tornadoes and blood clots.

Concerning second-order vortices - permanent and temporary barometric maxima and minima - it remains to say the following. The investigations of Hofmeyer, Teisserand de Bohr, and Hildebrandson pointed to a close relationship between the emergence and especially the movement of temporal highs and lows with the changes undergone by permanent highs and lows. The mere fact that these latter, with all possible changes in the weather in the regions surrounding them, change their boundaries or contours very little, indicates that here we are dealing with some permanent causes that lie above the influence of ordinary weather factors. According to Teisserand de Bor, pressure differences due to uneven heating or cooling of various parts of the earth's surface, summed up under the influence of a continuous increase in the primary factor over a more or less long period of time, give rise to large barometric maxima and minima. If the primary cause acts continuously or long enough, the result of its action will be permanent, stable vortex systems. Having reached a certain size and sufficient intensity, such constant maxima and minima are already determinants or regulators of the weather in vast areas in their circumference. Such large, constant highs and lows have been obtained in Lately, when their role in the weather phenomena of the countries surrounding them became clear, the name centers of action of the atmosphere. Owing to the invariance in the configuration of the earth's surface, and the consequent continuity of the action of the primary cause which brings them into being, the position of such maxima and minima on the globe is quite definite and invariable to a certain extent. But, depending on various conditions, their boundaries and their intensity can vary within certain limits. And these changes in their intensity and their outlines, in turn, should be reflected in the weather not only of neighboring, but sometimes even rather distant countries. Thus, the studies of Teisserand de Bora fully established the dependence of the weather in Europe on one of the following centers of action: anomalies of a negative nature, accompanied by a decrease in temperature compared to normal, are caused by the strengthening and expansion of the Siberian maximum or by the strengthening and thrusting of the Azores maximum; anomalies of a positive nature - with an increase in temperature against normal - are directly dependent on the movement and intensity of the Icelandic low. Hildebrandson went even further in this direction and quite successfully tried to connect changes in the intensity and movement of the two named Atlantic centers with changes not only in the Siberian High, but also in the centers of pressure in the Indian Ocean.

air masses

Weather observations became quite widespread in the second half of the 19th century. They were necessary for compiling synoptic maps showing the distribution of air pressure and temperature, wind and precipitation. As a result of the analysis of these observations, an idea of air masses has developed. This concept made it possible to combine individual elements, identify various weather conditions and give weather forecasts.

air mass a large volume of air is called, having horizontal dimensions of several hundred or thousands of kilometers and vertical dimensions of the order of 5 km, characterized by an approximate uniformity of temperature and humidity and moving as one system in one of the currents of the general circulation of the atmosphere (GCA)

The homogeneity of the properties of the air mass is achieved by its formation over a homogeneous underlying surface and under similar radiation conditions. In addition, such circulation conditions are necessary under which the air mass would linger for a long time in the area of formation.

The values of meteorological elements within the air mass change insignificantly - their continuity is preserved, the horizontal gradients are small. In the analysis of meteorological fields, as long as we remain in a given air mass, it is possible to apply linear graphical interpolation with sufficient approximation when drawing, for example, isotherms.

A sharp increase in the horizontal gradients of meteorological values, approaching an abrupt transition from one value to another, or at least a change in the magnitude and direction of the gradients occurs in the transitional (frontal zone) between two air masses. The pseudopotential air temperature, which reflects both the actual air temperature and its humidity, is taken as the most characteristic feature of an air mass.

Pseudopotential air temperature - the temperature that the air would take during the adiabatic process, if at first all the water vapor contained in it condensed at an unlimitedly falling pressure and fell out of the air and the released latent heat would go to heat the air, and then the air would be brought under standard pressure.

Since a warmer air mass is usually also more humid, the difference in the pseudopotential temperatures of two neighboring air masses is much greater than the difference in their actual temperatures. However, the pseudopotential temperature changes slowly with altitude within a given air mass. This property helps to determine the stratification of air masses one above the other in the troposphere.

The scale of air masses

Air masses are of the same order as the main currents of the general circulation of the atmosphere. The linear extent of air masses in the horizontal direction is measured in thousands of kilometers. Vertically, air masses extend up several kilometers of the troposphere, sometimes to its upper boundary.

During local circulations, such as, for example, breezes, mountain-valley winds, foehns, the air in the circulation flow is also more or less isolated in properties and movement from the surrounding atmosphere. However, in this case it is impossible to speak of air masses, since the scale of phenomena here will be different.

For example, a strip covered by a breeze may have a width of only 1-2 tens of kilometers, and therefore will not receive sufficient reflection on a synoptic map. The vertical power of the breeze current is also equal to several hundred meters. Thus, with local circulations, we are not dealing with independent air masses, but only with a perturbed state within the air masses over a short distance.

Objects resulting from the interaction of air masses - transitional zones (frontal surfaces), frontal cloud systems of cloudiness and precipitation, cyclonic disturbances, have the same order of magnitude as the air masses themselves - are comparable in area with large parts of the continents or oceans and their time existence - more than 2 days ( tab. 4):

The air mass has clear boundaries separating it from other air masses.

transition zones between air masses various properties, are called front surfaces.

Within the same air mass, graphical interpolation can be used with sufficient approximation, for example, when drawing isotherms. But when passing through the frontal zone from one air mass to another, linear interpolation will no longer give a correct idea of the actual distribution of meteorological elements.

The centers of formation of air masses

The air mass acquires clear characteristics in the center of formation.

The source of the formation of air masses must meet certain requirements:

Homogeneity of the underlying surface of water or land, so that the air in the source is subjected to sufficiently similar influences.

Homogeneity of radiation conditions.

Circulation conditions that contribute to the stationing of air in the area.

The centers of formation are usually areas where the air descends and then spreads in a horizontal direction - anticyclonic systems meet this requirement. Anticyclones more often than cyclones are sedentary, so the formation of air masses usually occurs in extensive sedentary (quasi-stationary) anticyclones.

In addition, sedentary and diffuse thermal depressions that occur over heated land areas meet the requirements of the source.

Finally, the formation of polar air occurs partly in the upper atmosphere in low-moving, extensive and deep central cyclones at high latitudes. In these baric systems, the transformation (transformation) of tropical air drawn into high latitudes in the upper troposphere into polar air takes place. All of the listed baric systems can also be called centers of air masses, not from a geographical, but from a synoptic point of view.

Geographic classification of air masses

Air masses are classified, first of all, according to the centers of their formation, depending on their location in one of the latitudinal zones - arctic, or antarctic, polar, or temperate latitudes, tropical and equatorial.

According to the geographical classification, air masses can be divided into main geographical types according to the latitudinal zones in which their centers are located:

Arctic or Antarctic air (AB),

Polar, or temperate, air (PV or SW),

Tropical Air (TV). These air masses, in addition, are divided into sea (m) and continental (c) air masses: mAV and cAV, mUV and kUV (or mPV and kPV), mTV and kTV.

Equatorial Air Masses (EW)

As for the equatorial latitudes, convergence (convergence of flows) and air rise occur here, therefore, air masses located above the equator are usually brought from subtropical zone. But sometimes separate equatorial air masses are distinguished.

Sometimes, in addition to the centers in the exact sense of the word, there are areas where in winter the air masses are transformed from one type to another when they move. These are areas in the Atlantic south of Greenland and in the Pacific Ocean above the Bering and Seas of Okhotsk, where the MW turns into MW, areas over Southeast North America and south of Japan in the Pacific Ocean where MW turns into MW during the winter monsoon, and an area in southern Asia where Asian MW turns into tropical air (also in monsoon flow)

Transformation of air masses

When the circulation conditions change, the air mass as a whole moves from the center of its formation to neighboring areas, interacting with other air masses.

When moving, the air mass begins to change its properties - they will already depend not only on the properties of the source of formation, but also on the properties of neighboring air masses, on the properties of the underlying surface over which the air mass passes, and also on the length of time elapsed since the formation of the air mass. masses.

These influences can cause changes in the moisture content of the air, as well as a change in air temperature as a result of the release of latent heat or heat exchange with the underlying surface.

The process of changing the properties of the air mass is called transformation or evolution.

The transformation associated with the movement of the air mass is called dynamic. The speed of movement of the air mass at different heights will be different, the presence of a speed shift causes turbulent mixing. If the lower layers of air are heated, then instability occurs and convective mixing develops.

air masses- these are the moving parts of the troposphere, differing from each other in their properties - temperature, transparency. These properties of air masses depend on the territory over which they are formed under the condition of a long stay. Depending on the formation, 4 main types of air masses are distinguished: (), tropical and. Each of these four types is formed over the expanse of land and sea. Since land and sea heat up to different degrees, subtypes can also form in each of these types - continental and sea air masses.

Arctic (Antarctic) air is formed over the ice surface of polar latitudes; characterized low temperatures, low moisture content, while the maritime Arctic air is more humid than the continental one. Invading low latitudes, Arctic air significantly lowers the temperature. flat relief contributes to its penetration far into the interior of the mainland. A similar phenomenon can be observed. As you move south, the Arctic air heats up and contributes to the formation of dry winds, which cause frequent in this area.

Moderate air masses form in temperate latitudes. Continental temperate air masses are strongly cooled in winter. They have a low moisture content. With the invasion of continental air masses, a clear frost is established. In summer, the continental air is dry and very hot. Marine air masses of temperate latitudes are humid, temperate; in winter they bring thaws, in summer - cloudy weather and cooling.

tropical air masses all year round formed in the tropics. Typically, their marine variety is characterized by high humidity and temperature, and the continental variety is dusty, dry and even higher temperature.

Equatorial air masses are formed in the equatorial zone. around its axis contributes to the movement of air masses to the Northern Hemisphere, then to the Southern. These air masses are characterized by high temperature and high humidity, and for them there is no clear division into maritime air masses and continental air masses.

The resulting air masses inevitably begin to move. The reason for this is the uneven heating of the earth's surface and, as a result, the difference. If there was no movement of air masses, then at the equator mean annual temperature would be 13° higher, and at latitudes of 70°, 23° lower than at present.

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

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 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. Radioactive fallout of varying intensity after tests of particularly 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 physiochemical properties the air itself, but also on the intensity of heat transfer, changes in humidity, pressure, chemical composition air, reducing or increasing the amount of 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 currents 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 land and sea surfaces, as well as plant transpiration.[ ...]

ANOMALOUS CYCLONE MOVEMENT. The movement of a cyclone in a direction sharply diverging from the usual, i.e., from the eastern half of the horizon to the western 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 visual representation of the state of the weather in this moment a synoptic map 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 principle in physical geography of the contrast of environments is manifested, which is expressed in a sharp activation of the exchange of matter and energy in the zone of contact (contact) of natural complexes of different properties 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. Great processes are taking place. atmospheric circulation, which are rhythmic in 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 of various bodies, we will have a layer with a certain excess of negative air ions, while ambient 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 the general atmospheric circulation system.[ ...]

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. For us, it is important that in the polar zones, where the lines of force of the Earth's magnetic field are closed on its surface, the distortions of the ionosphere are 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 polar day at small angles to the horizon, and during the polar night it is completely absent. 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 the polar "holes" in the ozone layer is a reliable indicator of changes in the total ozone content in the atmosphere.[ ...]

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 are propelled by the movement of air masses due to heating it by the sun and creating 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.[ ...]

The state of the free surface of reservoirs, due to the large area of their surface, is strongly influenced by 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 from the shores North Africa A huge cloud of locusts flew across the Red Sea to Arabia. The movement of insects lasted the whole day, and their mass amounted to 44 million tons. V.I. Vernadsky regarded this fact as evidence great strength living matter, an expression of the pressure of life, striving to capture the entire Earth. At the same time, he saw this as a biogeochemical process - the migration of elements that make up the locust biomass, a completely special migration - through the air, over long distances, which is 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 anticyclone. 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. 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 use by 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's important that chemical care did not turn into poisoning 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 condition into 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. returned to earth as precipitation water flows down 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.

Along with geographic latitude, an important climate-forming factor is atmospheric circulation, i.e., the movement of air masses.

air masses- significant volumes of air in the troposphere, which has certain properties (temperature, moisture content), depending on the characteristics of the region of its formation and moving as a whole.

The length of the air mass can be thousands of kilometers, and upwards it can extend to the upper limit of the troposphere.

Air masses are divided into two groups according to the speed of movement: moving and local. moving air masses, depending on the temperature of the underlying surface, are divided into warm and cold. Warm air mass - moving on a cold underlying surface, cold mass - moving on a warmer surface. Local air masses are air masses that do not change their geographical position. They can be stable and unstable depending on the season, as well as dry and wet.

There are four main types of air masses: equatorial, tropical, temperate, arctic (antarctic). In addition, each of the types is divided into subtypes: marine and continental, differing in humidity. For example, the maritime arctic mass is formed over the northern seas - the Barents and White Seas, is characterized, like the continental air mass, but with slightly increased humidity. (see fig. 1).

Rice. 1. Area of formation of Arctic air masses

The climate of Russia forms, to one degree or another, all air masses, with the exception of the equatorial one.

Consider the properties of various masses circulating on the territory of our country. arctic the air mass is formed mainly over the Arctic in the polar latitudes, characterized by low temperatures in winter and summer. It has low absolute humidity and high relative humidity. This air mass dominates all year round in arctic belt, and in winter it moves to the subarctic. Moderate the air mass is formed in temperate latitudes, where, depending on the time of year, the temperature changes: relatively high in summer, relatively low in winter. According to the seasons of the year, humidity also depends on the place of formation. This air mass dominates temperate zone. Partly, on the territory of Russia is dominated by tropical air masses. They form in tropical latitudes and have a high temperature. Absolute humidity depends on the place of formation, and relative humidity usually low (see Fig. 2).

Rice. 2. Characteristics of air masses

The passage of various air masses on the territory of Russia causes a difference in weather. For example, all the “cold waves” in our country coming from the north are Arctic air masses, and tropical air masses from Asia Minor or, sometimes, from northern Africa come to the south of the European part (they bring hot, dry weather).

Consider how air masses circulate through the territory of our country.

Atmospheric circulation is a system of motion of air masses. Distinguish between the general circulation of the atmosphere on the scale of the entire globe and the local circulation of the atmosphere over separate territories and water areas.

The process of circulation of air masses provides the territory with moisture, and also affects the temperature. Air masses move under the influence of atmospheric pressure centers, and the centers change depending on the season. That is why the direction of the prevailing winds, which bring air masses to the territory of our country, changes. For example, European Russia and the western regions of Siberia are under the influence of constant westerly winds. With them come moderate sea air masses of temperate latitudes. They form over the Atlantic (See Fig. 3).

Rice. 3. Movement of marine moderate air masses

When the westerly transport weakens, the Arctic air mass comes with the northerly winds. It brings a sharp cold snap, early autumn and late spring frosts. (see Fig. 4).

Rice. 4. Movement of the Arctic air mass

Continental tropical air to the territory of the Asian part of our country comes from Central Asia or from Northern China, and in European part countries comes from the peninsula of Asia Minor or even from North Africa, but more often such air is formed on the territory of North Asia, Kazakhstan, Caspian lowland. These areas lie in the temperate climate zone. However, the air above them warms up very strongly in summer and acquires the properties of a tropical air mass. Continental moderate air mass prevails all year round in the western regions of Siberia, so winters are clear and frosty, and summers are quite warm. Even over the Arctic Ocean, Greenland has warmer winters.

Due to strong cooling over the Asian part of our country, an area of strong cooling is formed in Eastern Siberia (an area of high pressure - ). Its center is located in the regions of Transbaikalia, the Republic of Tuva and Northern Mongolia. Very cold continental air spreads from it in different directions. It extends its influence over vast territories. One of its directions is the northeast up to the Chukchi coast, the second - to the west through Northern Kazakhstan and the south of the Russian (East European) plain to about 50ºN. Clear and frosty weather sets in with a small amount of snow. In summer, due to warming, the Asian maximum (Siberian anticyclone) disappears and low pressure sets in. (See Fig. 5).

Rice. 5. Siberian anticyclone

The seasonal alternation of high and low pressure areas forms on Far East monsoon circulation of the atmosphere. It is important to realize that, passing through certain territories, air masses can change depending on the properties of the underlying surface. This process is called transformation of air masses. For example, the Arctic air mass, being dry and cold, while passing through the territory of the East European (Russian) Plain, heats up and becomes very dry and hot in the region of the Caspian Lowland, which causes dry winds.

Asian High, or, as it is called, the Siberian anticyclone is an area of high pressure that forms over Central Asia and Eastern Siberia. It manifests itself in winter and is formed as a result of cooling of the territory in conditions of enormous size and hollow relief. In the central part of the maximum over Mongolia and South Siberia, the pressure in January sometimes reaches 800 mm Hg. Art. This is the highest pressure recorded on earth. In winter, the great Siberian anticyclone extends here, especially stable from November to March. The winter here is so windless that with little snowfall, the branches of the trees turn white for a long time from the “unshaken” snow. Frosts already from October reach -20 ... -30ºС, and in January it often reaches -60ºC. average temperature in a month it drops to -43º, it is especially cold in the lowlands, where cold heavy air stagnates. When there is no wind, severe frosts are not so hard to bear, but at -50º it is already difficult to breathe, low fogs are observed. Such frosts make it difficult for planes to land.

Bibliography

Geography of Russia. Nature. Population. 1 hour Grade 8 / V.P. Dronov, I.I. Barinova, V.Ya Rom, A.A. Lobzhanidze.
V.B. Pyatunin, E.A. Customs. Geography of Russia. Nature. Population. 8th grade.
Atlas. Geography of Russia. population and economy. - M.: Bustard, 2012.
V.P. Dronov, L.E. Savelyeva. UMK (educational-methodical set) "SPHERES". Textbook “Russia: nature, population, economy. 8th grade". Atlas.

Climate-forming factors and atmospheric circulation ().
Properties of air masses that form the climate of Russia ().
Western transfer of air masses ().
Air masses ().
Atmospheric circulation ().

Homework

What kind of air mass transfer dominates in our country?
What properties do air masses have, and what does it depend on?