The composition of the earth's atmosphere in percent. Layers of the atmosphere - troposphere, stratosphere, mesosphere, thermosphere and exosphere

The atmosphere extends upward for many hundreds of kilometers. Its upper boundary, at an altitude of about 2000-3000 km, to a certain extent conditional, since the gases that make up it, gradually rarefied, pass into the world space. The chemical composition of the atmosphere, pressure, density, temperature and its other physical properties change with height. As mentioned earlier, the chemical composition of air up to a height of 100 km does not change significantly. Somewhat higher, the atmosphere also consists mainly of nitrogen and oxygen. But at altitudes 100-110 km, Under the influence of ultraviolet radiation from the sun, oxygen molecules are split into atoms and atomic oxygen appears. Above 110-120 km almost all of the oxygen becomes atomic. It is assumed that above 400-500 km the gases that make up the atmosphere are also in the atomic state.

Air pressure and density decrease rapidly with height. Although the atmosphere extends upwards for hundreds of kilometers, most of it is located in a rather thin layer adjacent to the earth's surface in its lowest parts. So, in the layer between sea level and altitudes 5-6 km half of the mass of the atmosphere is concentrated in layer 0-16 km-90%, and in the layer 0-30 km- 99%. The same rapid decrease in air mass occurs above 30 km. If weight 1 m 3 air at the earth's surface is 1033 g, then at a height of 20 km it is equal to 43 g, and at a height of 40 km only 4 years

At an altitude of 300-400 km and above, the air is so rarefied that during the day its density changes many times. Studies have shown that this change in density is related to the position of the Sun. The highest air density is around noon, the lowest at night. This is partly explained by the fact that the upper layers of the atmosphere react to changes in the electromagnetic radiation of the Sun.

The change in air temperature with height is also uneven. According to the nature of the change in temperature with height, the atmosphere is divided into several spheres, between which there are transitional layers, the so-called pauses, where the temperature changes little with height.

Here are the names and main characteristics of spheres and transition layers.

Let us present the basic data on the physical properties of these spheres.

Troposphere. The physical properties of the troposphere are largely determined by the influence of the earth's surface, which is its lower boundary. The highest height of the troposphere is observed in the equatorial and tropical zones. Here it reaches 16-18 km and relatively little subject to daily and seasonal changes. Above the polar and adjacent regions, the upper boundary of the troposphere lies on average at a level of 8-10 km. In mid-latitudes, it ranges from 6-8 to 14-16 km.

The vertical power of the troposphere depends significantly on the nature of atmospheric processes. Often during the day, the upper boundary of the troposphere over a given point or area drops or rises by several kilometers. This is mainly due to changes in air temperature.

More than 4/5 of the mass of the earth's atmosphere and almost all of the water vapor contained in it are concentrated in the troposphere. In addition, from the earth's surface to the upper limit of the troposphere, the temperature drops by an average of 0.6° for every 100 m, or 6° for 1 km uplift . This is due to the fact that the air in the troposphere is heated and cooled mainly from the surface of the earth.

In accordance with the influx of solar energy, the temperature decreases from the equator to the poles. Thus, the average air temperature near the earth's surface at the equator reaches +26°, over the polar regions -34°, -36° in winter, and about 0° in summer. Thus, the temperature difference between the equator and the pole is 60° in winter and only 26° in summer. True, such low temperatures in the Arctic in winter are observed only near the surface of the earth due to cooling of the air over the ice expanses.

In winter, in Central Antarctica, the air temperature on the surface of the ice sheet is even lower. At Vostok station in August 1960, the lowest temperature on the globe was recorded -88.3°, and most often in Central Antarctica it is -45°, -50°.

From a height, the temperature difference between the equator and the pole decreases. For example, at height 5 km at the equator the temperature reaches -2°, -4°, and at the same height in the Central Arctic -37°, -39° in winter and -19°, -20° in summer; therefore, the temperature difference in winter is 35-36°, and in summer 16-17°. In the southern hemisphere, these differences are somewhat larger.

The energy of atmospheric circulation can be determined by equator-pole temperature contracts. Since the temperature contrasts are greater in winter, atmospheric processes are more intense than in summer. This also explains the fact that the prevailing westerly winds in the troposphere in winter have higher speeds than in summer. In this case, the wind speed, as a rule, increases with height, reaching a maximum at the upper boundary of the troposphere. Horizontal transport is accompanied by vertical air movements and turbulent (disordered) movement. Due to the rise and fall of large volumes of air, clouds form and disperse, precipitation occurs and stops. The transition layer between the troposphere and the overlying sphere is tropopause. Above it lies the stratosphere.

Stratosphere extends from heights 8-17 to 50-55 km. It was opened at the beginning of our century. In terms of physical properties, the stratosphere differs sharply from the troposphere in that the air temperature here, as a rule, rises by an average of 1–2 ° per kilometer of elevation and at the upper boundary, at a height of 50–55 km, even becomes positive. The increase in temperature in this area is caused by the presence of ozone (O 3) here, which is formed under the influence of ultraviolet radiation from the Sun. The ozone layer covers almost the entire stratosphere. The stratosphere is very poor in water vapor. There are no violent processes of cloud formation and no precipitation.

More recently, it was assumed that the stratosphere is a relatively calm environment, where air mixing does not occur, as in the troposphere. Therefore, it was believed that the gases in the stratosphere are divided into layers, in accordance with their specific gravity. Hence the name of the stratosphere ("stratus" - layered). It was also believed that the temperature in the stratosphere is formed under the influence of radiative equilibrium, i.e., when the absorbed and reflected solar radiation are equal.

New data obtained by radiosondes and meteorological rockets have shown that in the stratosphere, as in the upper troposphere, there is an intense circulation of air with large changes in temperature and wind. Here, as in the troposphere, the air experiences significant vertical movements, turbulent movements with strong horizontal air currents. All this is the result of a non-uniform temperature distribution.

The transition layer between the stratosphere and the overlying sphere is stratopause. However, before proceeding to the characteristics of the higher layers of the atmosphere, let's get acquainted with the so-called ozonosphere, the boundaries of which approximately correspond to the boundaries of the stratosphere.

Ozone in the atmosphere. Ozone plays an important role in creating the temperature regime and air currents in the stratosphere. Ozone (O 3) is felt by us after a thunderstorm when we inhale clean air with a pleasant aftertaste. However, here we will not talk about this ozone formed after a thunderstorm, but about the ozone contained in the layer 10-60 km with a maximum at a height of 22-25 km. Ozone is produced by the action of the ultraviolet rays of the sun and, although its total amount is insignificant, plays an important role in the atmosphere. Ozone has the ability to absorb the ultraviolet radiation of the sun and thereby protects the animal and plant world from its harmful effects. Even that tiny fraction of ultraviolet rays that reaches the surface of the earth burns the body badly when a person is excessively fond of sunbathing.

The amount of ozone is not the same over different parts of the Earth. There is more ozone in high latitudes, less in middle and low latitudes, and this amount changes depending on the change of seasons of the year. More ozone in spring, less in autumn. In addition, its non-periodic fluctuations occur depending on the horizontal and vertical circulation of the atmosphere. Many atmospheric processes are closely related to the ozone content, since it has a direct effect on the temperature field.

In winter, during the polar night, at high latitudes, the ozone layer emits and cools the air. As a result, in the stratosphere of high latitudes (in the Arctic and Antarctic), a cold region forms in winter, a stratospheric cyclonic eddy with large horizontal temperature and pressure gradients, which causes westerly winds over the middle latitudes of the globe.

In summer, under conditions of a polar day, at high latitudes, the ozone layer absorbs solar heat and warms the air. As a result of the temperature increase in the stratosphere of high latitudes, a heat region and a stratospheric anticyclonic vortex are formed. Therefore, over the average latitudes of the globe above 20 km in summer, easterly winds prevail in the stratosphere.

Mesosphere. Observations with meteorological rockets and other methods have established that the overall temperature increase observed in the stratosphere ends at altitudes of 50-55 km. Above this layer, the temperature drops again and near the upper boundary of the mesosphere (about 80 km) reaches -75°, -90°. Further, the temperature rises again with height.

It is interesting to note that the decrease in temperature with height, characteristic of the mesosphere, occurs differently at different latitudes and throughout the year. At low latitudes, the temperature drop occurs more slowly than at high latitudes: the average vertical temperature gradient for the mesosphere is, respectively, 0.23° - 0.31° per 100 m or 2.3°-3.1° per 1 km. In summer it is much larger than in winter. As shown by the latest research in high latitudes, the temperature at the upper boundary of the mesosphere in summer is several tens of degrees lower than in winter. In the upper mesosphere at a height of about 80 km in the mesopause layer, the decrease in temperature with height stops and its increase begins. Here, under the inversion layer at twilight or before sunrise in clear weather, brilliant thin clouds are observed, illuminated by the sun below the horizon. Against the dark background of the sky, they glow with a silvery-blue light. Therefore, these clouds are called silvery.

The nature of noctilucent clouds is not yet well understood. For a long time it was believed that they were composed of volcanic dust. However, the absence of optical phenomena characteristic of real volcanic clouds led to the rejection of this hypothesis. Then it was suggested that noctilucent clouds are composed of cosmic dust. In recent years, a hypothesis has been proposed that these clouds are composed of ice crystals, like ordinary cirrus clouds. The level of location of noctilucent clouds is determined by the delay layer due to temperature inversion during the transition from the mesosphere to the thermosphere at a height of about 80 km. Since the temperature in the subinversion layer reaches -80°C and lower, the most favorable conditions are created here for the condensation of water vapor, which enters here from the stratosphere as a result of vertical movement or by turbulent diffusion. Noctilucent clouds are usually observed in the summer, sometimes in very large numbers and for several months.

Observations of noctilucent clouds have established that in summer at their level the winds are highly variable. Wind speeds vary widely: from 50-100 to several hundred kilometers per hour.

Temperature at altitude. A visual representation of the nature of the temperature distribution with height, between the earth's surface and altitudes of 90-100 km, in winter and summer in the northern hemisphere, is given in Figure 5. The surfaces separating the spheres are depicted here by bold dashed lines. At the very bottom, the troposphere stands out well, with a characteristic decrease in temperature with height. Above the tropopause, in the stratosphere, on the contrary, the temperature increases with height in general and at heights of 50-55 km reaches + 10°, -10°. Let's pay attention to an important detail. In winter, in the stratosphere of high latitudes, the temperature above the tropopause drops from -60 to -75 ° and only above 30 km rises again to -15°. In summer, starting from the tropopause, the temperature increases with height and by 50 km reaches + 10°. Above the stratopause, the temperature again begins to decrease with height, and at a level of 80 km it does not exceed -70°, -90°.

From figure 5 it follows that in layer 10-40 km the air temperature in winter and summer in high latitudes is sharply different. In winter, during the polar night, the temperature here reaches -60°, -75°, and in summer a minimum of -45° is near the tropopause. Above the tropopause, the temperature increases and at altitudes of 30-35 km is only -30°, -20°, which is caused by the heating of the air in the ozone layer during the polar day. It also follows from the figure that even in one season and at the same level, the temperature is not the same. Their difference between different latitudes exceeds 20-30°. In this case, the inhomogeneity is especially significant in the low-temperature layer (18-30 km) and in the layer of maximum temperatures (50-60 km) in the stratosphere, as well as in the layer of low temperatures in the upper mesosphere (75-85km).

The mean temperatures shown in Figure 5 are based on observations in the northern hemisphere, but according to the available information, they can also be attributed to the southern hemisphere. Some differences exist mainly at high latitudes. Over Antarctica in winter, the air temperature in the troposphere and lower stratosphere is noticeably lower than over the Central Arctic.

Winds on high. The seasonal distribution of temperature determines a rather complex system of air currents in the stratosphere and mesosphere.

Figure 6 shows a vertical section of the wind field in the atmosphere between the earth's surface and a height of 90 km winter and summer over the northern hemisphere. The isolines show the average speeds of the prevailing wind (in m/s). It follows from the figure that the wind regime in winter and summer in the stratosphere is sharply different. In winter, both in the troposphere and in the stratosphere, westerly winds prevail with maximum speeds equal to about

100 m/s at a height of 60-65 km. In summer, westerly winds prevail only up to heights of 18-20 km. Higher they become eastern, with maximum speeds up to 70 m/s at a height of 55-60km.

In summer, above the mesosphere, the winds become westerly, and in winter, they become easterly.

Thermosphere. Above the mesosphere is the thermosphere, which is characterized by an increase in temperature with height. According to the data obtained, mainly with the help of rockets, it was found that in the thermosphere it is already at the level of 150 km the air temperature reaches 220-240°, and at the level of 200 km over 500°. Above, the temperature continues to rise and at the level of 500-600 km exceeds 1500°. On the basis of data obtained during launches of artificial earth satellites, it has been found that in the upper thermosphere the temperature reaches about 2000° and fluctuates significantly during the day. The question arises how to explain such a high temperature in the high layers of the atmosphere. Recall that the temperature of a gas is a measure of the average velocity of molecules. In the lower, densest part of the atmosphere, the gas molecules that make up the air often collide with each other when moving and instantly transfer kinetic energy to each other. Therefore, the kinetic energy in a dense medium is on average the same. In high layers, where the air density is very low, collisions between molecules located at large distances occur less frequently. When energy is absorbed, the speed of molecules in the interval between collisions changes greatly; in addition, the molecules of lighter gases move at a higher speed than the molecules of heavy gases. As a result, the temperature of the gases can be different.

In rarefied gases, there are relatively few molecules of very small sizes (light gases). If they move at high speeds, then the temperature in a given volume of air will be high. In the thermosphere, each cubic centimeter of air contains tens and hundreds of thousands of molecules of various gases, while at the surface of the earth there are about a hundred million billion of them. Therefore, excessively high temperatures in the high layers of the atmosphere, showing the speed of movement of molecules in this very thin medium, cannot cause even a slight heating of the body located here. Just as a person does not feel heat when dazzling electric lamps, although the filaments in a rarefied medium instantly heat up to several thousand degrees.

In the lower thermosphere and mesosphere, the main part of meteor showers burns out before reaching the earth's surface.

Available information about atmospheric layers above 60-80 km are still insufficient for final conclusions about the structure, regime and processes developing in them. However, it is known that in the upper mesosphere and lower thermosphere, the temperature regime is created as a result of the transformation of molecular oxygen (O 2) into atomic oxygen (O), which occurs under the action of ultraviolet solar radiation. In the thermosphere, the temperature regime is greatly influenced by corpuscular, X-ray, and radiation. ultraviolet radiation from the sun. Here, even during the day, there are sharp changes in temperature and wind.

Atmospheric ionization. The most interesting feature of the atmosphere above 60-80 km is her ionization, i.e., the process of formation of a huge number of electrically charged particles - ions. Since the ionization of gases is characteristic of the lower thermosphere, it is also called the ionosphere.

The gases in the ionosphere are mostly in the atomic state. Under the action of ultraviolet and corpuscular radiation of the Sun, which have high energy, the process of splitting off electrons from neutral atoms and air molecules occurs. Such atoms and molecules, having lost one or more electrons, become positively charged, and a free electron can reattach to a neutral atom or molecule and endow them with its negative charge. These positively and negatively charged atoms and molecules are called ions, and the gases ionized, i.e., having received an electric charge. At a higher concentration of ions, gases become electrically conductive.

The ionization process occurs most intensively in thick layers limited by heights of 60-80 and 220-400 km. In these layers, there are optimal conditions for ionization. Here, the air density is noticeably higher than in the upper atmosphere, and the influx of ultraviolet and corpuscular radiation from the Sun is sufficient for the ionization process.

The discovery of the ionosphere is one of the most important and brilliant achievements of science. After all, a distinctive feature of the ionosphere is its influence on the propagation of radio waves. In the ionized layers, radio waves are reflected, and therefore long-range radio communication becomes possible. Charged atoms-ions reflect short radio waves, and they again return to the earth's surface, but already at a considerable distance from the place of radio transmission. Obviously, short radio waves make this path several times, and thus long-range radio communication is ensured. If not for the ionosphere, then for the transmission of radio station signals over long distances it would be necessary to build expensive radio relay lines.

However, it is known that sometimes shortwave radio communications are disrupted. This occurs as a result of chromospheric flares on the Sun, due to which the ultraviolet radiation of the Sun sharply increases, leading to strong disturbances of the ionosphere and the Earth's magnetic field - magnetic storms. During magnetic storms, radio communication is disrupted, since the movement of charged particles depends on the magnetic field. During magnetic storms, the ionosphere reflects radio waves worse or passes them into space. Mainly with a change in solar activity, accompanied by an increase in ultraviolet radiation, the electron density of the ionosphere and the absorption of radio waves in the daytime increase, leading to disruption of short-wave radio communications.

According to new research, in a powerful ionized layer there are zones where the concentration of free electrons reaches a slightly higher concentration than in neighboring layers. Four such zones are known, which are located at altitudes of about 60-80, 100-120, 180-200 and 300-400 km and are marked with letters D, E, F 1 and F 2 . With increasing radiation from the Sun, charged particles (corpuscles) under the influence of the Earth's magnetic field are deflected towards high latitudes. Upon entering the atmosphere, corpuscles intensify the ionization of gases to such an extent that their glow begins. This is how auroras- in the form of beautiful multi-colored arcs that light up in the night sky, mainly in the high latitudes of the Earth. Auroras are accompanied by strong magnetic storms. In such cases, the auroras become visible in the middle latitudes, and in rare cases even in the tropical zone. Thus, for example, the intense aurora observed on January 21-22, 1957, was visible in almost all the southern regions of our country.

By photographing the auroras from two points located at a distance of several tens of kilometers, the height of the aurora is determined with great accuracy. Auroras are usually located at an altitude of about 100 km, often they are found at an altitude of several hundred kilometers, and sometimes at a level of about 1000 km. Although the nature of auroras has been elucidated, there are still many unresolved issues related to this phenomenon. The reasons for the diversity of forms of auroras are still unknown.

According to the third Soviet satellite, between heights 200 and 1000 km during the day, positive ions of split molecular oxygen, i.e., atomic oxygen (O), predominate. Soviet scientists are studying the ionosphere with the help of artificial satellites of the Kosmos series. American scientists are also studying the ionosphere with the help of satellites.

The surface separating the thermosphere from the exosphere fluctuates depending on changes in solar activity and other factors. Vertically, these fluctuations reach 100-200 km and more.

Exosphere (scattering sphere) - the uppermost part of the atmosphere, located above 800 km. She is little studied. According to the data of observations and theoretical calculations, the temperature in the exosphere increases with height presumably up to 2000°. In contrast to the lower ionosphere, in the exosphere the gases are so rarefied that their particles, moving at tremendous speeds, almost never meet each other.

Until relatively recently, it was assumed that the conditional boundary of the atmosphere is located at an altitude of about 1000 km. However, based on the deceleration of artificial Earth satellites, it has been established that at altitudes of 700-800 km in 1 cm 3 contains up to 160 thousand positive ions of atomic oxygen and nitrogen. This gives grounds to assume that the charged layers of the atmosphere extend into space for a much greater distance.

At high temperatures, at the conditional boundary of the atmosphere, the velocities of gas particles reach approximately 12 km/s At these velocities, the gases gradually leave the region of the earth's gravity into interplanetary space. This has been going on for a long time. For example, particles of hydrogen and helium are removed into interplanetary space over several years.

In the study of the high layers of the atmosphere, rich data were obtained both from satellites of the Kosmos and Elektron series, and geophysical rockets and space stations Mars-1, Luna-4, etc. Direct observations of astronauts were also valuable. So, according to photographs taken in space by V. Nikolaeva-Tereshkova, it was found that at an altitude of 19 km there is a dust layer from the Earth. This was also confirmed by the data obtained by the crew of the Voskhod spacecraft. Apparently, there is a close relationship between the dust layer and the so-called mother-of-pearl clouds, sometimes observed at altitudes of about 20-30km.

From the atmosphere to outer space. Previous assumptions that outside the Earth's atmosphere, in the interplanetary

space, gases are very rarefied and the concentration of particles does not exceed several units in 1 cm 3, were not justified. Studies have shown that near-Earth space is filled with charged particles. On this basis, a hypothesis was put forward about the existence of zones around the Earth with a markedly increased content of charged particles, i.e. radiation belts- internal and external. New data helped to clarify. It turned out that there are also charged particles between the inner and outer radiation belts. Their number varies depending on geomagnetic and solar activity. Thus, according to the new assumption, instead of radiation belts, there are radiation zones without clearly defined boundaries. The boundaries of radiation zones change depending on solar activity. With its intensification, i.e., when spots and jets of gas appear on the Sun, ejected over hundreds of thousands of kilometers, the flow of cosmic particles increases, which feed the radiation zones of the Earth.

Radiation zones are dangerous for people flying on spacecraft. Therefore, before the flight into space, the state and position of the radiation zones are determined, and the spacecraft orbit is chosen in such a way that it passes outside the regions of increased radiation. However, the high layers of the atmosphere, as well as outer space close to the Earth, have not yet been studied enough.

In the study of the high layers of the atmosphere and near-Earth space, rich data obtained from satellites of the Kosmos series and space stations are used.

The high layers of the atmosphere are the least studied. However, modern methods of studying it allow us to hope that in the coming years a person will know many details of the structure of the atmosphere at the bottom of which he lives.

In conclusion, we present a schematic vertical section of the atmosphere (Fig. 7). Here, the altitudes in kilometers and air pressure in millimeters are plotted vertically, and the temperature is plotted horizontally. The solid curve shows the change in air temperature with height. At the corresponding heights, the most important phenomena observed in the atmosphere, as well as the maximum heights reached by radiosondes and other means of atmospheric sounding, were noted.

The Earth's atmosphere is heterogeneous: different air densities and pressures are observed at different heights, temperature and gas composition change. Based on the behavior of the ambient temperature (i.e., the temperature rises with height or decreases), the following layers are distinguished in it: troposphere, stratosphere, mesosphere, thermosphere and exosphere. The boundaries between the layers are called pauses: there are 4 of them, because. the upper boundary of the exosphere is very blurred and often refers to the near space. The general structure of the atmosphere can be found in the attached diagram.

Fig.1 The structure of the Earth's atmosphere. Credit: website

The lowest atmospheric layer is the troposphere, the upper boundary of which, called the tropopause, varies depending on the geographical latitude and ranges from 8 km. in polar up to 20 km. in tropical latitudes. In middle or temperate latitudes, its upper boundary lies at altitudes of 10-12 km. During the year, the upper boundary of the troposphere experiences fluctuations depending on the influx of solar radiation. So, as a result of sounding at the South Pole of the Earth by the US meteorological service, it was revealed that from March to August or September there is a steady cooling of the troposphere, as a result of which, for a short period in August or September, its border rises to 11.5 km. Then, between September and December, it drops rapidly and reaches its lowest position - 7.5 km, after which its height remains practically unchanged until March. Those. The troposphere is at its thickest in summer and at its thinnest in winter.

It should be noted that in addition to seasonal variations, there are also daily fluctuations in the height of the tropopause. Also, its position is influenced by cyclones and anticyclones: in the first, it descends, because. the pressure in them is lower than in the surrounding air, and secondly, it rises accordingly.

The troposphere contains up to 90% of the total mass of the earth's air and 9/10 of all water vapor. Turbulence is highly developed here, especially in the near-surface and highest layers, clouds of all tiers develop, cyclones and anticyclones form. And due to the accumulation of greenhouse gases (carbon dioxide, methane, water vapor) of the sun's rays reflected from the Earth's surface, the greenhouse effect develops.

The greenhouse effect is associated with a decrease in air temperature in the troposphere with height (because the heated Earth gives off more heat to the surface layers). The average vertical gradient is 0.65°/100 m (i.e. the air temperature drops by 0.65° C for every 100 meters you rise). So if at the Earth's surface near the equator the average annual air temperature is + 26 °, then at the upper limit -70 °. The temperature in the tropopause region above the North Pole varies throughout the year from -45° in summer to -65° in winter.

As the altitude increases, the air pressure also decreases, amounting to only 12-20% of the near-surface level near the upper troposphere.

On the border of the troposphere and the overlying layer of the stratosphere lies the tropopause layer, 1-2 km thick. The air layer in which the vertical gradient decreases to 0.2°/100 m versus 0.65°/100 m in the underlying regions of the troposphere is usually taken as the lower boundaries of the tropopause.

Within the tropopause, air flows of a strictly defined direction are observed, called high-altitude jet streams or "jet streams", formed under the influence of the Earth's rotation around its axis and heating of the atmosphere with the participation of solar radiation. Currents are observed at the boundaries of zones with significant temperature differences. There are several centers of localization of these currents, for example, arctic, subtropical, subpolar and others. Knowing the localization of jet streams is very important for meteorology and aviation: the first uses streams for more accurate weather forecasting, the second for building aircraft flight routes, because At the flow boundaries there are strong turbulent eddies, similar to small whirlpools, called "clear sky turbulence" due to the absence of clouds at these heights.

Under the influence of high-altitude jet currents, ruptures often form in the tropopause, and at times it disappears altogether, though then it forms again. This is especially often observed in subtropical latitudes over which a powerful subtropical high-altitude current dominates. In addition, the difference in the layers of the tropopause in terms of ambient air temperature leads to the formation of breaks. For example, a wide gap exists between the warm and low polar tropopause and the high and cold tropopause of tropical latitudes. Recently, a layer of the tropopause of temperate latitudes has also been distinguished, which has breaks with the previous two layers: polar and tropical.

The second layer of the earth's atmosphere is the stratosphere. The stratosphere can be conditionally divided into 2 regions. The first of them, lying up to heights of 25 km, is characterized by almost constant temperatures, which are equal to the temperatures of the upper layers of the troposphere over a specific area. The second region, or inversion region, is characterized by an increase in air temperature to altitudes of about 40 km. This is due to the absorption of solar ultraviolet radiation by oxygen and ozone. In the upper part of the stratosphere, due to this heating, the temperature is often positive or even comparable to the surface air temperature.

Above the inversion region is a layer of constant temperatures, which is called the stratopause and is the boundary between the stratosphere and the mesosphere. Its thickness reaches 15 km.

Unlike the troposphere, turbulent disturbances are rare in the stratosphere, but strong horizontal winds or jet streams blowing in narrow zones along the borders of temperate latitudes facing the poles are noted. The position of these zones is not constant: they can shift, expand, or even disappear altogether. Often, jet streams penetrate into the upper layers of the troposphere, or vice versa, air masses from the troposphere penetrate into the lower layers of the stratosphere. Such mixing of air masses in areas of atmospheric fronts is especially characteristic.

Little in the stratosphere and water vapor. The air here is very dry, and therefore there are few clouds. Only at altitudes of 20-25 km, being in high latitudes, one can notice very thin mother-of-pearl clouds, consisting of supercooled water droplets. During the day, these clouds are not visible, but with the onset of darkness, they seem to glow due to their illumination by the Sun that has already set below the horizon.

At the same heights (20-25 km.) in the lower stratosphere there is the so-called ozone layer - the area with the highest ozone content, which is formed under the influence of ultraviolet solar radiation (you can learn more about this process on the page). The ozone layer or ozonosphere is essential to sustain life for all organisms living on land by absorbing deadly ultraviolet rays up to 290 nm. It is for this reason that living organisms do not live above the ozone layer, it is the upper limit of the spread of life on Earth.

Under the influence of ozone, magnetic fields also change, atoms break up molecules, ionization occurs, new formation of gases and other chemical compounds.

The layer of the atmosphere above the stratosphere is called the mesosphere. It is characterized by a decrease in air temperature with height with an average vertical gradient of 0.25-0.3°/100 m, which leads to strong turbulence. At the upper boundaries of the mesosphere in the area called the mesopause, temperatures up to -138 ° C were noted, which is the absolute minimum for the entire atmosphere of the Earth as a whole.

Here, within the mesopause, the lower boundary of the region of active absorption of X-ray and short-wavelength ultraviolet radiation of the Sun passes. This energy process is called radiant heat transfer. As a result, the gas is heated and ionized, which causes the glow of the atmosphere.

At altitudes of 75-90 km near the upper boundaries of the mesosphere, special clouds were noted, occupying vast areas in the polar regions of the planet. These clouds are called silver because of their glow at dusk, which is due to the reflection of sunlight from the ice crystals of which these clouds are composed.

Air pressure within the mesopause is 200 times less than at the earth's surface. This suggests that almost all the air in the atmosphere is concentrated in its 3 lower layers: the troposphere, stratosphere and mesosphere. The overlying layers of the thermosphere and exosphere account for only 0.05% of the mass of the entire atmosphere.

The thermosphere lies at altitudes from 90 to 800 km above the Earth's surface.

The thermosphere is characterized by a continuous increase in air temperature up to altitudes of 200-300 km, where it can reach 2500°C. The increase in temperature occurs due to the absorption by gas molecules of the X-ray and short-wave part of the ultraviolet radiation of the Sun. Above 300 km above sea level, the temperature rise stops.

At the same time as the temperature rises, the pressure decreases, and, consequently, the density of the surrounding air. So if at the lower boundaries of the thermosphere the density is 1.8 × 10 -8 g / cm 3, then at the upper it is already 1.8 × 10 -15 g / cm 3, which approximately corresponds to 10 million - 1 billion particles in 1 cm 3 .

All characteristics of the thermosphere, such as the composition of air, its temperature, density, are subject to strong fluctuations: depending on the geographical location, season of the year and time of day. Even the location of the upper boundary of the thermosphere is changing.

The uppermost layer of the atmosphere is called the exosphere or scattering layer. Its lower limit is constantly changing within very wide limits; the height of 690-800 km was taken as the average value. It is set where the probability of intermolecular or interatomic collisions can be neglected, i.e. the average distance that a randomly moving molecule will cover before colliding with another similar molecule (the so-called free path) will be so large that, in fact, the molecules will not collide with a probability close to zero. The layer where the described phenomenon takes place is called the thermopause.

The upper boundary of the exosphere lies at altitudes of 2-3 thousand km. It is strongly blurred and gradually passes into the near space vacuum. Sometimes, for this reason, the exosphere is considered a part of outer space, and its upper boundary is taken to be a height of 190 thousand km, at which the effect of solar radiation pressure on the speed of hydrogen atoms exceeds the gravitational attraction of the Earth. This is the so-called. the earth's corona, which is made up of hydrogen atoms. The density of the earth's corona is very low: only 1000 particles per cubic centimeter, but even this number is more than 10 times higher than the concentration of particles in interplanetary space.

Due to the extremely rarefied air of the exosphere, particles move around the Earth in elliptical orbits without colliding with each other. Some of them, moving along open or hyperbolic trajectories with cosmic velocities (hydrogen and helium atoms), leave the atmosphere and go into outer space, which is why the exosphere is called the scattering sphere.

The atmosphere is the gaseous shell of our planet that rotates with the Earth. The gas in the atmosphere is called air. The atmosphere is in contact with the hydrosphere and partially covers the lithosphere. But it is difficult to determine the upper bounds. Conventionally, it is assumed that the atmosphere extends upwards for about three thousand kilometers. There it flows smoothly into the airless space.

The chemical composition of the Earth's atmosphere

The formation of the chemical composition of the atmosphere began about four billion years ago. Initially, the atmosphere consisted only of light gases - helium and hydrogen. According to scientists, the initial prerequisites for the creation of a gas shell around the Earth were volcanic eruptions, which, together with lava, emitted a huge amount of gases. Subsequently, gas exchange began with water spaces, with living organisms, with the products of their activity. The composition of the air gradually changed and in its present form was fixed several million years ago.

The main components of the atmosphere are nitrogen (about 79%) and oxygen (20%). The remaining percentage (1%) is accounted for by the following gases: argon, neon, helium, methane, carbon dioxide, hydrogen, krypton, xenon, ozone, ammonia, sulfur dioxide and nitrogen, nitrous oxide and carbon monoxide included in this one percent.

In addition, the air contains water vapor and particulate matter (plant pollen, dust, salt crystals, aerosol impurities).

Recently, scientists have noted not a qualitative, but a quantitative change in some air ingredients. And the reason for this is the person and his activity. Only in the last 100 years, the content of carbon dioxide has increased significantly! This is fraught with many problems, the most global of which is climate change.

Formation of weather and climate

The atmosphere plays a vital role in shaping the climate and weather on Earth. A lot depends on the amount of sunlight, on the nature of the underlying surface and atmospheric circulation.

Let's look at the factors in order.

1. The atmosphere transmits the heat of the sun's rays and absorbs harmful radiation. The ancient Greeks knew that the rays of the Sun fall on different parts of the Earth at different angles. The very word "climate" in translation from ancient Greek means "slope". So, at the equator, the sun's rays fall almost vertically, because it is very hot here. The closer to the poles, the greater the angle of inclination. And the temperature is dropping.

2. Due to the uneven heating of the Earth, air currents are formed in the atmosphere. They are classified according to their size. The smallest (tens and hundreds of meters) are local winds. This is followed by monsoons and trade winds, cyclones and anticyclones, planetary frontal zones.

All these air masses are constantly moving. Some of them are quite static. For example, the trade winds that blow from the subtropics towards the equator. The movement of others is largely dependent on atmospheric pressure.

3. Atmospheric pressure is another factor influencing climate formation. This is the air pressure on the earth's surface. As you know, air masses move from an area with high atmospheric pressure towards an area where this pressure is lower.

There are 7 zones in total. The equator is a low pressure zone. Further, on both sides of the equator up to the thirtieth latitudes - an area of ​​high pressure. From 30° to 60° - again low pressure. And from 60° to the poles - a zone of high pressure. Air masses circulate between these zones. Those that go from the sea to land bring rain and bad weather, and those that blow from the continents bring clear and dry weather. In places where air currents collide, atmospheric front zones are formed, which are characterized by precipitation and inclement, windy weather.

Scientists have proven that even a person's well-being depends on atmospheric pressure. According to international standards, normal atmospheric pressure is 760 mm Hg. column at 0°C. This figure is calculated for those areas of land that are almost flush with sea level. The pressure decreases with altitude. Therefore, for example, for St. Petersburg 760 mm Hg. - is the norm. But for Moscow, which is located higher, the normal pressure is 748 mm Hg.

The pressure changes not only vertically, but also horizontally. This is especially felt during the passage of cyclones.

The structure of the atmosphere

The atmosphere is like a layer cake. And each layer has its own characteristics.

. Troposphere is the layer closest to the Earth. The "thickness" of this layer changes as you move away from the equator. Above the equator, the layer extends upwards for 16-18 km, in temperate zones - for 10-12 km, at the poles - for 8-10 km.

It is here that 80% of the total mass of air and 90% of water vapor are contained. Clouds form here, cyclones and anticyclones arise. The air temperature depends on the altitude of the area. On average, it drops by 0.65°C for every 100 meters.

. tropopause- transitional layer of the atmosphere. Its height is from several hundred meters to 1-2 km. The air temperature in summer is higher than in winter. So, for example, over the poles in winter -65 ° C. And over the equator at any time of the year it is -70 ° C.

. Stratosphere- this is a layer, the upper boundary of which runs at an altitude of 50-55 kilometers. Turbulence is low here, water vapor content in the air is negligible. But a lot of ozone. Its maximum concentration is at an altitude of 20-25 km. In the stratosphere, the air temperature begins to rise and reaches +0.8 ° C. This is due to the fact that the ozone layer interacts with ultraviolet radiation.

. Stratopause- a low intermediate layer between the stratosphere and the mesosphere following it.

. Mesosphere- the upper boundary of this layer is 80-85 kilometers. Here complex photochemical processes involving free radicals take place. It is they who provide that gentle blue glow of our planet, which is seen from space.

Most comets and meteorites burn up in the mesosphere.

. mesopause- the next intermediate layer, the air temperature in which is at least -90 °.

. Thermosphere- the lower boundary begins at an altitude of 80 - 90 km, and the upper boundary of the layer passes approximately at the mark of 800 km. The air temperature is rising. It can vary from +500° C to +1000° C. During the day, temperature fluctuations amount to hundreds of degrees! But the air here is so rarefied that the understanding of the term "temperature" as we imagine it is not appropriate here.

. Ionosphere- unites mesosphere, mesopause and thermosphere. The air here consists mainly of oxygen and nitrogen molecules, as well as quasi-neutral plasma. The sun's rays, falling into the ionosphere, strongly ionize air molecules. In the lower layer (up to 90 km), the degree of ionization is low. The higher, the more ionization. So, at an altitude of 100-110 km, electrons are concentrated. This contributes to the reflection of short and medium radio waves.

The most important layer of the ionosphere is the upper one, which is located at an altitude of 150-400 km. Its peculiarity is that it reflects radio waves, and this contributes to the transmission of radio signals over long distances.

It is in the ionosphere that such a phenomenon as aurora occurs.

. Exosphere- consists of oxygen, helium and hydrogen atoms. The gas in this layer is very rarefied, and often hydrogen atoms escape into outer space. Therefore, this layer is called the "scattering zone".

The first scientist who suggested that our atmosphere has weight was the Italian E. Torricelli. Ostap Bender, for example, in the novel "The Golden Calf" lamented that each person was pressed by an air column weighing 14 kg! But the great strategist was a little mistaken. An adult person experiences pressure of 13-15 tons! But we do not feel this heaviness, because atmospheric pressure is balanced by the internal pressure of a person. The weight of our atmosphere is 5,300,000,000,000,000 tons. The figure is colossal, although it is only a millionth of the weight of our planet.

The composition of the atmosphere. The air shell of our planet - atmosphere protects the earth's surface from the harmful effects on living organisms of ultraviolet radiation from the Sun. It also protects the Earth from cosmic particles - dust and meteorites.

The atmosphere consists of a mechanical mixture of gases: 78% of its volume is nitrogen, 21% is oxygen, and less than 1% is helium, argon, krypton and other inert gases. The amount of oxygen and nitrogen in the air is practically unchanged, because nitrogen almost does not enter into compounds with other substances, and oxygen, which, although very active and is spent on respiration, oxidation and combustion, is constantly replenished by plants.

Up to a height of about 100 km, the percentage of these gases remains practically unchanged. This is due to the fact that the air is constantly mixed.

In addition to these gases, the atmosphere contains about 0.03% carbon dioxide, which is usually concentrated near the earth's surface and is distributed unevenly: in cities, industrial centers and areas of volcanic activity, its amount increases.

There is always a certain amount of impurities in the atmosphere - water vapor and dust. The content of water vapor depends on the temperature of the air: the higher the temperature, the more vapor the air holds. Due to the presence of vaporous water in the air, atmospheric phenomena such as rainbows, refraction of sunlight, etc. are possible.

Dust enters the atmosphere during volcanic eruptions, sand and dust storms, with incomplete combustion of fuel at thermal power plants, etc.

The structure of the atmosphere. The density of the atmosphere changes with height: it is highest at the Earth's surface, and decreases as it rises. So, at an altitude of 5.5 km, the density of the atmosphere is 2 times, and at an altitude of 11 km - 4 times less than in the surface layer.

Depending on the density, composition and properties of gases, the atmosphere is divided into five concentric layers (Fig. 34).

Rice. 34. Vertical section of the atmosphere (atmospheric stratification)

1. The bottom layer is called troposphere. Its upper boundary runs at an altitude of 8-10 km at the poles and 16-18 km at the equator. The troposphere contains up to 80% of the total mass of the atmosphere and almost all of the water vapor.

The air temperature in the troposphere decreases with height by 0.6 °C every 100 m and at its upper boundary it is -45-55 °C.

The air in the troposphere is constantly mixed, moving in different directions. Only here fogs, rains, snowfalls, thunderstorms, storms and other weather phenomena are observed.

2. Above is located stratosphere, which extends to a height of 50-55 km. Air density and pressure in the stratosphere are negligible. The rarefied air consists of the same gases as in the troposphere, but it contains more ozone. The highest concentration of ozone is observed at an altitude of 15-30 km. The temperature in the stratosphere rises with height and reaches 0 °C or more at its upper boundary. This is due to the fact that ozone absorbs the short-wavelength part of solar energy, as a result of which the air heats up.

3. Above the stratosphere lies mesosphere, extending to a height of 80 km. In it, the temperature drops again and reaches -90 ° C. The air density there is 200 times less than at the surface of the Earth.

4. Above the mesosphere is thermosphere(from 80 to 800 km). The temperature in this layer rises: at an altitude of 150 km to 220 °C; at an altitude of 600 km to 1500 °C. The atmospheric gases (nitrogen and oxygen) are in an ionized state. Under the action of short-wave solar radiation, individual electrons are detached from the shells of atoms. As a result, in this layer - ionosphere layers of charged particles appear. Their densest layer is at an altitude of 300-400 km. Due to the low density, the sun's rays do not scatter there, so the sky is black, stars and planets shine brightly on it.

In the ionosphere there are polar lights, powerful electric currents are generated that cause disturbances in the Earth's magnetic field.

5. Above 800 km, the outer shell is located - exosphere. The speed of movement of individual particles in the exosphere approaches the critical one - 11.2 mm/s, so individual particles can overcome the Earth's gravity and escape into the world space.

The value of the atmosphere. The role of the atmosphere in the life of our planet is exceptionally great. Without it, the Earth would be dead. The atmosphere protects the Earth's surface from intense heating and cooling. Its influence can be likened to the role of glass in greenhouses: to let in the sun's rays and prevent heat from escaping.

The atmosphere protects living organisms from the shortwave and corpuscular radiation of the Sun. The atmosphere is the environment where weather phenomena occur, with which all human activity is associated. The study of this shell is carried out at meteorological stations. Day and night, in any weather, meteorologists monitor the state of the lower atmosphere. Four times a day, and at many stations every hour they measure temperature, pressure, air humidity, note cloudiness, wind direction and speed, precipitation, electrical and sound phenomena in the atmosphere. Meteorological stations are located everywhere: in Antarctica and in tropical rainforests, on high mountains and in the vast expanses of the tundra. Observations are also being made on the oceans from specially built ships.

From the 30s. 20th century observations began in the free atmosphere. They began to launch radiosondes, which rise to a height of 25-35 km, and with the help of radio equipment transmit to Earth information about temperature, pressure, air humidity and wind speed. Nowadays, meteorological rockets and satellites are also widely used. The latter have television installations that transmit images of the earth's surface and clouds.

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5. Air shell of the earth§ 31. Heating of the atmosphere

The gaseous envelope that surrounds our planet Earth, known as the atmosphere, consists of five main layers. These layers originate on the surface of the planet, from sea level (sometimes below) and rise to outer space in the following sequence:

• Troposphere;
• Stratosphere;
• Mesosphere;
• Thermosphere;
• Exosphere.

Diagram of the main layers of the Earth's atmosphere

In between each of these main five layers are transitional zones called "pauses" where changes in air temperature, composition and density occur. Together with pauses, the Earth's atmosphere includes a total of 9 layers.

Troposphere: where the weather happens

Of all the layers of the atmosphere, the troposphere is the one with which we are most familiar (whether you realize it or not), since we live at its bottom - the surface of the planet. It envelops the surface of the Earth and extends upwards for several kilometers. The word troposphere means "change of the ball". A very fitting name, as this layer is where our day to day weather happens.

Starting from the surface of the planet, the troposphere rises to a height of 6 to 20 km. The lower third of the layer closest to us contains 50% of all atmospheric gases. It is the only part of the entire composition of the atmosphere that breathes. Due to the fact that the air is heated from below by the earth's surface, which absorbs the thermal energy of the Sun, the temperature and pressure of the troposphere decrease with increasing altitude.

At the top is a thin layer called the tropopause, which is just a buffer between the troposphere and stratosphere.

Stratosphere: home of ozone

The stratosphere is the next layer of the atmosphere. It extends from 6-20 km to 50 km above the earth's surface. This is the layer in which most commercial airliners fly and balloons travel.

Here, the air does not flow up and down, but moves parallel to the surface in very fast air currents. Temperatures increase as you ascend, thanks to an abundance of naturally occurring ozone (O3), a by-product of solar radiation, and oxygen, which has the ability to absorb the sun's harmful ultraviolet rays (any rise in temperature with altitude is known in meteorology as an "inversion") .

Because the stratosphere has warmer temperatures at the bottom and cooler temperatures at the top, convection (vertical movements of air masses) is rare in this part of the atmosphere. In fact, you can view a storm raging in the troposphere from the stratosphere, since the layer acts as a "cap" for convection, through which storm clouds do not penetrate.

The stratosphere is again followed by a buffer layer, this time called the stratopause.

Mesosphere: middle atmosphere

The mesosphere is located approximately 50-80 km from the Earth's surface. The upper mesosphere is the coldest natural place on Earth, where temperatures can drop below -143°C.

Thermosphere: upper atmosphere

The mesosphere and mesopause are followed by the thermosphere, located between 80 and 700 km above the surface of the planet, and containing less than 0.01% of the total air in the atmospheric shell. Temperatures here reach up to +2000° C, but due to the strong rarefaction of the air and the lack of gas molecules to transfer heat, these high temperatures are perceived as very cold.

Exosphere: the boundary of the atmosphere and space

At an altitude of about 700-10,000 km above the earth's surface is the exosphere - the outer edge of the atmosphere, bordering space. Here meteorological satellites revolve around the Earth.

How about the ionosphere?

The ionosphere is not a separate layer, and in fact this term is used to refer to the atmosphere at an altitude of 60 to 1000 km. It includes the uppermost parts of the mesosphere, the entire thermosphere and part of the exosphere. The ionosphere gets its name because in this part of the atmosphere, the Sun's radiation is ionized when it passes the Earth's magnetic fields at and . This phenomenon is observed from the earth as the northern lights.