The Earth's atmosphere is the gaseous envelope of our planet. Its lower boundary is at the level crust and hydrosphere, and the upper one goes into the near-earth region outer space... The atmosphere contains about 78% nitrogen, 20% oxygen, up to 1% argon, carbon dioxide, hydrogen, helium, neon and some other gases.
This earth's shell is characterized by pronounced layering. The layers of the atmosphere are determined by the vertical distribution of temperature and different densities of gases at different levels. There are such layers of the Earth's atmosphere: troposphere, stratosphere, mesosphere, thermosphere, exosphere. The ionosphere is distinguished separately.
Up to 80% of the entire mass of the atmosphere is the troposphere - the lower surface layer of the atmosphere. Troposphere in polar belts located at a level up to 8-10 km above the earth's surface, in tropical belt- maximum up to 16-18 km. Between the troposphere and the overlying stratosphere layer, there is a tropopause - a transitional layer. In the troposphere, the temperature decreases with increasing altitude, similarly, atmospheric pressure decreases with altitude. The average temperature gradient in the troposphere is 0.6 ° С per 100 m. The temperature at different levels this shell is determined by the features of absorption of solar radiation and the efficiency of convection. Almost all human activity takes place in the troposphere. Most high mountains do not go beyond the troposphere, only air transport can cross the upper boundary of this shell to a small height and be in the stratosphere. A large proportion of water vapor is contained in the troposphere, which determines the formation of almost all clouds. Also, almost all aerosols (dust, smoke, etc.) are concentrated in the troposphere. the earth's surface... In the lower boundary layer of the troposphere, daily fluctuations in temperature and air humidity are expressed, the wind speed is usually reduced (it increases with increasing altitude). In the troposphere, there is a changeable division of the air mass into air masses in the horizontal direction, which differ in a number of characteristics depending on the belt and the terrain of their formation. On atmospheric fronts- boundaries between air masses - cyclones and anticyclones are formed, which determine the weather in a certain area during a specific period of time.
The stratosphere is the layer of the atmosphere between the troposphere and the mesosphere. The limits of this layer range from 8-16 km to 50-55 km above the Earth's surface. In the stratosphere, the gas composition of the air is approximately the same as in the troposphere. A distinctive feature is a decrease in the concentration of water vapor and an increase in the ozone content. The ozone layer of the atmosphere, which protects the biosphere from the aggressive effects of ultraviolet light, is at a level of 20 to 30 km. In the stratosphere, the temperature rises with height, and the temperature values are determined solar radiation, and not by convection (movements air masses), as in the troposphere. Heating of the air in the stratosphere is due to the absorption of ultraviolet radiation by ozone.
The mesosphere extends over the stratosphere up to the level of 80 km. This layer of the atmosphere is characterized by the fact that the temperature decreases with increasing altitude from 0 ° C to -90 ° C. This is the coldest region of the atmosphere.
Above the mesosphere there is a thermosphere up to a level of 500 km. From the border with the mesosphere to the exosphere, the temperature changes from about 200 K to 2000 K. To the level of 500 km, the air density decreases several hundred thousand times. The relative composition of the atmospheric components of the thermosphere is similar to the surface layer of the troposphere, but with an increase in height large quantity oxygen goes into an atomic state. A certain fraction of molecules and atoms of the thermosphere are in an ionized state and are distributed in several layers, they are united by the concept of the ionosphere. The characteristics of the thermosphere vary over a wide range depending on the geographical latitude, magnitude solar radiation, time of year and day.
The upper atmosphere is the exosphere. This is the thinnest layer of the atmosphere. In the exosphere, the mean free paths of particles are so huge that particles can freely move out into interplanetary space. The mass of the exosphere is one ten millionth of the total mass of the atmosphere. The lower boundary of the exosphere is at the level of 450-800 km, and the upper boundary is considered to be the area where the concentration of particles is the same as in outer space - several thousand kilometers from the Earth's surface. The exosphere is made up of plasma, an ionized gas. Also in the exosphere are the radiation belts of our planet.
Video presentation - layers of the Earth's atmosphere:
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The atmosphere extends upwards for many hundreds of kilometers. Its upper border, at an altitude of about 2000-3000 km, to a certain extent, it is conditional, since the gases, its constituents, gradually thinning out, pass into the world space. Chemical changes with height composition of the atmosphere, pressure, density, temperature and its other physical properties. As mentioned earlier, the chemical composition of air up to a height of 100 km does not change significantly. A little 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 split into atoms and atomic oxygen appears. Above 110-120 km almost all oxygen becomes atomic. It is assumed that above 400-500 km the gases that make up the atmosphere are also in an atomic state.
Air pressure and density rapidly decrease with height. Although the atmosphere extends upwards for hundreds of kilometers, its bulk 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 heights of 5-6 km half the mass of the atmosphere is concentrated, in the 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 the weight is 1 m 3 air at the surface of the earth is 1033 g, then at an altitude of 20 km it is equal to 43 g, and at a height of 40 km only 4 g
At an altitude of 300-400 km and above, the air is so rarefied that its density changes many times during the day. Research has 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 explained in part 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 also occurs unequally. By the nature of the change in temperature with height, the atmosphere is divided into several spheres, between which there are transition layers, the so-called pauses, where the temperature changes little with height.
Here are the names and main characteristics of the spheres and transition layers.
Here are 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 tropospheric height is observed in the equatorial and tropical zones. Here she reaches 16-18 km and relatively little is exposed 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 middle latitudes, it ranges from 6-8 to 14-16 km.
The vertical thickness of the troposphere depends significantly on the nature of atmospheric processes. Often, during the day, the upper border 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 surface of the earth to the upper boundary of the troposphere, the temperature decreases by an average of 0.6 ° for every 100 m, or 6 ° per 1 km uplifting . This is due to the fact that the air in the troposphere is heated and cooled mainly from the earth's surface.
According to the inflow solar energy the temperature goes down from the equator to the poles. So, the average air temperature near the earth's surface at the equator reaches + 26 °, over the polar regions in winter -34 °, -36 °, and in summer about 0 °. 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 the cooling of the air over the icy 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 equal to -45 °, -50 °.
From the height, the temperature difference between the equator and the pole decreases. For example, at a height of 5 km at the equator, the temperature reaches - 2 °, -4 °, and at the same altitude 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 magnitude of temperature contrasts is greater in winter, atmospheric processes are more intense than in summer. This also explains the fact that the prevailing westerly winds in winter in the troposphere they have higher velocities 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. As a result of the rise and fall of large volumes of air, clouds are formed and dispersed, precipitation appears and stops. The transition layer between the troposphere and the overlying sphere is tropopause. Above it lies the stratosphere.
Stratosphere stretches from heights 8-17 to 50-55 km. It was discovered at the beginning of our century. In terms of physical properties, the stratosphere sharply differs from the troposphere already in that the air temperature here, as a rule, rises by an average of 1 - 2 ° per kilometer of rise and at the upper boundary, at an altitude of 50-55 km, even becomes positive. The rise 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 occupies almost the entire stratosphere. The stratosphere is very poor in water vapor. There are no violent cloud formation processes and no precipitation.
More recently, it was assumed that the stratosphere is a relatively calm environment, where there is no mixing of air, as in the troposphere. Therefore, it was believed that the gases in the stratosphere are divided into layers, in accordance with their specific weights... Hence the name of the stratosphere ("stratus" - layered). It was also assumed that the temperature in the stratosphere is formed under the influence of radiative equilibrium, that is, when the absorbed and reflected solar radiation is equal.
New data obtained with the help of radiosondes and meteorological rockets showed that in the stratosphere, as in the upper troposphere, there is intense air circulation with large changes in temperature and wind. Here, as in the troposphere, the air experiences significant vertical displacements, turbulent movements with strong horizontal air currents. All this is the result of a non-uniform temperature distribution.
The transitional layer between the stratosphere and the overlying sphere is stratopause. However, before proceeding to characterize the higher layers of the atmosphere, let us familiarize ourselves 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 a regime of temperature 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 are not talking about this ozone formed after a thunderstorm, but about the ozone contained in the 10-60 km with a maximum at a height of 22-25 km. Ozone is generated by the sun's ultraviolet rays and, although total amount its insignificantly, plays important role in the atmosphere. Ozone has the ability to absorb ultraviolet radiation from the Sun and thus protects the animal and vegetable world from its destructive action. Even that tiny fraction of ultraviolet rays that reaches the surface of the earth burns the body severely when a person is overly addicted to sunbathing.
The amount of ozone is not the same over various parts Earth. There is more ozone in high latitudes, less in middle and low latitudes and this number changes depending on the change of seasons of the year. More ozone in spring, less ozone 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, under polar night conditions, at high latitudes in the ozone layer, air is emitted and cooled. As a result, in the stratosphere of high latitudes (in the Arctic and Antarctic) in winter, a cold region forms, a stratospheric cyclonic vortex with large horizontal temperature and pressure gradients, causing westerly winds over mid-latitudes the globe.
In summer, during a polar day, at high latitudes, the ozone layer absorbs solar heat and warms up the air. As a result of an increase in temperature in the stratosphere of high latitudes, a heat region and a stratospheric anticyclonic vortex are formed. Therefore, above the middle latitudes of the globe above 20 km in summer, easterly winds prevail in the stratosphere.
Mesosphere. Observations using meteorological rockets and other methods have established that the general increase in temperature observed in the stratosphere ends at heights of 50-55 km. Above this layer, the temperature again decreases and at 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 altitude, 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 0.23 ° - 0.31 ° per 100, respectively. m or 2.3 ° -3.1 ° per 1 km. In summer, it is much larger than in winter. As shown latest research at high latitudes, the temperature at the upper boundary of the mesosphere in summer is several tens of degrees lower than in winter. V upper mesosphere at an altitude of about 80 km in the mesopause layer, the decrease in temperature with height stops and begins to rise. Here, under the inversion layer at dusk or before sunrise at clear weather shining 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 still not well understood. For a long time, they were believed to be composed of volcanic dust. However, the absence of optical phenomena inherent in real volcanic clouds led to the rejection of this hypothesis. It was then 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 location of noctilucent clouds is determined by the retarding layer due to temperature inversion during the transition from the mesosphere to the thermosphere at an altitude of about 80 km. Since in the sub-inversion layer the temperature reaches -80 ° and below, the most favorable conditions are created for 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 during 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 heights. A visual representation of the nature of the temperature distribution with height, between the earth's surface and heights of 90-100 km, in winter and summer in the northern hemisphere, is given in Figure 5. The surfaces separating the spheres are shown 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 generally rises with altitude and at heights of 50-55 km reaches + 10 °, -10 °. Pay attention to 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 increases again to -15 °. In summer, starting from the tropopause, the temperature rises with altitude and by 50 km reaches + 10 °. Above the stratopause, the temperature again begins to decrease with altitude, and at a level of 80 km it does not exceed -70 °, -90 °.
Figure 5 shows that in layer 10-40 km the air temperature in winter and summer in high latitudes is sharply different. In winter, under polar night conditions, 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 warming up of the air in the ozone layer in the conditions of a polar day. It also follows from the figure that even in the same season and at the same level, the temperature is not the same. Their difference between different latitudes exceeds 20-30 °. At the same time, the heterogeneity is especially significant in the layer of low temperatures (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 average temperatures shown in Figure 5 were obtained from observations in the northern hemispheres, however, judging by the available information, they can be attributed to southern hemisphere... Some differences are found 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.
High winds. The seasonal temperature distribution is responsible for 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 in winter and summer over the northern hemisphere. 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 / sec at a height of 60-65 km. In summer, westerly winds prevail only up to heights of 18-20 km. Above they become eastern, with maximum speeds of up to 70 m / sec at a height of 55-60km.
In summer, above the mesosphere, the winds become westerly, and in winter - easterly.
Thermosphere. The thermosphere is located above the mesosphere, 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 already at the level of 150 km air temperature reaches 220-240 °, and at 200 km more than 500 °. Above, the temperature continues to rise and at the level of 500-600 km exceeds 1500 °. Based on data obtained during launches artificial satellites It was 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 speed of movement of molecules. In the lower, densest part of the atmosphere, the molecules of the gases that make up the air, when moving, often collide with each other and instantly transfer kinetic energy to each other. That's why kinetic energy in a dense environment, on average, the same. In high layers, where the air density is very low, collisions between molecules located at large distances are less frequent. When energy is absorbed, the velocity of the molecules in the interval between collisions changes greatly; in addition, molecules of lighter gases move at a higher speed than 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 with 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 hundreds of millions of billions. Therefore, excessively high temperatures in high layers of the atmosphere, showing the speed of movement of molecules in this very loose environment, cannot cause even a slight heating of the body located here. Just as a person does not feel the high temperature under the dazzling illumination of electric lamps, although the filaments in a rarefied environment instantly heat up to several thousand degrees.
In the lower thermosphere and mesosphere, the main part of the meteor showers burns up before reaching the surface of the earth.
Available information on 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 conversion of molecular oxygen (O 2) into atomic (O), which occurs under the action of ultraviolet solar radiation. In the thermosphere at the temperature mode big influence renders corpuscular, x-ray and. ultraviolet radiation from the sun. Here, even during the day, there are sharp changes in temperature and wind.
Ionization of the atmosphere. Most interesting feature atmosphere above 60-80 km is her ionization, i.e. the process of education huge amount electrically charged particles - ions. Since the ionization of gases is characteristic of the lower thermosphere, it is also called the ionosphere.
Gases in the ionosphere are mostly in the atomic state. Under the influence of ultraviolet and corpuscular radiation of the Sun, which have high energy, the process of splitting off electrons from neutral atoms and molecules of air takes place. Such atoms and molecules that have lost one or more electrons become positively charged, and a free electron can attach again to a neutral atom or molecule and endow them with its negative charge. Such positively and negatively charged atoms and molecules are called ions, and gases - ionized i.e. those who received electric charge... With a higher concentration of ions, the 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 distinctive feature 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 return to the earth's surface again, but already at a considerable distance from the place of radio transmission. Obviously, short radio waves make this path several times, and thus long-distance radio communication is provided. If it were not for the ionosphere, expensive radio relay lines would have to be built to transmit signals from radio stations over long distances.
However, it is known that sometimes radio communications at short wavelengths are disrupted. This occurs as a result of chromospheric flares on the Sun, due to which the ultraviolet radiation of the Sun is sharply increased, 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 is less likely to reflect radio waves or transmit 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 radio communication at short wavelengths.
According to new studies, there are zones in a powerful ionized layer where the concentration of free electrons reaches a slightly higher concentration than in neighboring layers. There are four known such zones, which are located at heights of about 60-80, 100-120, 180-200 and 300-400 km and denoted by letters D, E, F 1 and F 2 ... With the increasing radiation of the Sun, charged particles (corpuscles) are deflected towards high latitudes under the influence of the Earth's magnetic field. Entering the atmosphere, the corpuscles intensify the ionization of gases so much that they begin to glow. This is how polar lights- in the form of beautiful multicolored 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, auroras become visible at mid-latitudes, and at rare cases even in the tropical zone. For example, the intense aurora observed on January 21-22, 1957, was visible in almost all southern regions of our country.
By photographing auroras from two points located at a distance of several tens of kilometers, the height of the aurora is determined with great accuracy. Usually auroras are located at an altitude of about 100 km, they are often found at an altitude of several hundred kilometers, and sometimes at a level of about 1000 km. Although the nature of the auroras has been clarified, there are still many unresolved issues related to this phenomenon. The reasons for the variety of forms of auroras are still unknown.
According to the third Soviet satellite, between altitudes 200 and 1000 km during the day, positive ions of split molecular oxygen, i.e., atomic oxygen (O), prevail. Soviet scientists are exploring the ionosphere using artificial satellites of the Kosmos series. American scientists are also studying the ionosphere using satellites.
The surface separating the thermosphere from the exosphere undergoes fluctuations depending on changes in solar activity and other factors. Vertically, these fluctuations reach 100-200 km and more.
Exosphere (sphere of dispersion) - the uppermost part of the atmosphere, located above 800 km. It has been little studied. According to observational data and theoretical calculations, the temperature in the exosphere with height increases presumably up to 2000 °. Unlike the lower ionosphere, gases in the exosphere are so rarefied that their particles, moving at tremendous speeds, hardly meet each other.
More recently, it was assumed that the conditional boundary of the atmosphere is at an altitude of about 1000 km. However, based on the deceleration of artificial earth satellites, it was found that at altitudes of 700-800 km in 1 cm 3 contains up to 160 thousand positive ions of atomic oxygen and nitrogen. This suggests that the charged layers of the atmosphere extend into space for a much greater distance.
At high temperatures at the conventional boundary of the atmosphere, the velocities of gas particles reach approximately 12 km / sec. At these velocities, gases gradually leave the area of gravity into interplanetary space. This has been happening 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 "Cosmos" and "Electron" series, and from 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 confirmed by the data received by the crew. spaceship"Sunrise". Apparently, there is a close connection 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 per 1 cm 3, did not come true. 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 noticeably increased content of charged particles, i.e. radiation belts- internal and external. The 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 the radiation zones change depending on solar activity. When it intensifies, that is, when spots and jets of gas appear on the Sun, ejected for 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 in spaceships. Therefore, before the flight into space, the state and position of the radiation zones are determined, and the orbit of the spacecraft is chosen so that it passes outside the areas of increased radiation. However, the high layers of the atmosphere, as well as the outer space close to the Earth, are still poorly explored.
In the study of the high layers of the atmosphere and near-earth space, use is made of rich data obtained from the "Cosmos" series satellites and space stations.
The high layers of the atmosphere are the least studied. However, modern methods of its study 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 vertical heights are plotted in kilometers and air pressure in millimeters, and horizontally - temperature. The solid curve shows the change in air temperature with height. The most important phenomena observed in the atmosphere, as well as maximum heights reached by radiosondes and other means of sounding the atmosphere.
Deals with meteorology, and long-term variations - climatology.
The thickness of the atmosphere is 1500 km from the Earth's surface. The total mass of air, that is, the mixture of gases that make up the atmosphere, is 5.1-5.3 * 10 ^ 15 tons. The molecular weight of clean dry air is 29. The pressure at 0 ° C at sea level is 101 325 Pa, or 760 mm. rt. Art .; critical temperature - 140.7 ° С; critical pressure 3.7 MPa. Solubility of air in water at 0 ° С - 0.036%, at 25 ° С - 0.22%.
The physical state of the atmosphere is determined. The main parameters of the atmosphere: air density, pressure, temperature and composition. With an increase in altitude, air density and decrease. The temperature also changes with changes in altitude. Vertical is characterized by different temperature and electrical properties, different air conditions. Depending on the temperature in the atmosphere, the following main layers are distinguished: troposphere, stratosphere, mesosphere, thermosphere, exosphere (scattering sphere). The transitional regions of the atmosphere between adjacent shells are called tropopause, stratopause, etc., respectively.
Troposphere- the lower, main, most studied, with a height in the polar regions of 8-10 km, in temperate latitudes up to 10-12 km, at the equator - 16-18 km. The troposphere contains about 80-90% of the entire mass of the atmosphere and almost all water vapor. With a rise every 100 m, the temperature in the troposphere decreases by an average of 0.65 ° С and reaches -53 ° С in the upper part. This upper troposphere is called the tropopause. Turbulence and convection are highly developed in the troposphere, the predominant part is concentrated, clouds appear, develop.
Stratosphere- the layer of the atmosphere located at an altitude of 11-50 km. A slight change in temperature in the layer 11-25 km ( bottom layer stratosphere) and its rise in the 25-40 km layer from -56.5 to 0.8 ° C (the upper layer of the stratosphere or the inversion region). Having reached a value of 273 K (0 ° C) at an altitude of about 40 km, the temperature remains constant up to an altitude of 55 km. This region of constant temperature is called the stratopause and is the boundary between the stratosphere and the mesosphere.
It is in the stratosphere that the layer is located ozonosphere("Ozone layer", at an altitude of 15-20 to 55-60 km), which defines the upper limit of life in. An important component of the stratosphere and mesosphere is ozone, which is formed as a result of photochemical reactions most intensively at an altitude of 30 km. The total mass of ozone would be at normal pressure a layer with a thickness of 1.7-4 mm, but this is also enough to absorb ultraviolet, which is harmful to life. The destruction of ozone occurs when it interacts with free radicals, nitrogen oxide, halogen-containing compounds (including "freons"). Ozone - allotropy of oxygen, is formed as a result of the following chemical reaction, usually after rain, when the resulting compound rises to the upper troposphere; ozone has a specific smell.
In the stratosphere, most of the short-wave part of ultraviolet radiation (180-200 nm) is retained and the transformation of short-wave energy occurs. Under the influence of these rays change magnetic fields, molecules disintegrate, ionization occurs, new formation of gases and other chemical compounds. These processes can be observed in the form of northern lights, lightning, and other glow. There is almost no water vapor in the stratosphere.
Mesosphere starts at an altitude of 50 km and extends up to 80-90 km. to an altitude of 75-85 km, it decreases to -88 ° С. The upper boundary of the mesosphere is the mesopause.
Thermosphere(another name - the ionosphere) - the layer of the atmosphere following the mesosphere - begins at an altitude of 80-90 km and extends up to 800 km. The air temperature in the thermosphere rises rapidly and steadily and reaches several hundred and even thousands of degrees.
Exosphere- the scattering zone, the outer part of the thermosphere, located above 800 km. Gas in the exosphere is very rarefied, and from here comes the leakage of its particles into interplanetary space (dissipation).
Up to an altitude of 100 km, the atmosphere is a homogeneous (single-phase), well-mixed mixture of gases. In higher layers, the distribution of gases along the height depends on their molecular weights, the concentration of heavier gases decreases faster with distance from the Earth's surface. Due to a decrease in the density of gases, the temperature decreases from 0 ° С in the stratosphere to -110 ° С in the mesosphere. However, the kinetic energy of individual particles at altitudes of 200-250 km corresponds to a temperature of approximately 1500 ° C. Above 200 km, significant fluctuations in the temperature and density of gases are observed in time and space.
At an altitude of about 2000-3000 km, the exosphere gradually passes into the so-called near-space vacuum, which is filled with highly rarefied particles of interplanetary gas, mainly hydrogen atoms. But this gas is only a fraction of the interplanetary matter. The other part is made up of dust-like particles of cometary and meteoric origin. In addition to these extremely rarefied particles, electromagnetic and corpuscular radiation of solar and galactic origin penetrates into this space.
The troposphere accounts for about 80% of the mass of the atmosphere, the stratosphere - about 20%; the mass of the mesosphere is no more than 0.3%, the thermosphere is less than 0.05% of the total mass of the atmosphere. On the basis of electrical properties in the atmosphere, the neutrosphere and ionosphere are distinguished. At present, it is believed that the atmosphere extends to an altitude of 2000-3000 km.
Homosphere and heterosphere are distinguished depending on the composition of the gas in the atmosphere. Heterosphere- this is the area where gravity affects the separation of gases, because their mixing at this height is negligible. Hence the variable composition of the heterosphere. Below it lies a well-mixed, homogeneous part of the atmosphere called the homosphere. The boundary between these layers is called the turbopause; it lies at an altitude of about 120 km.
Atmospheric pressure - pressure atmospheric air on the objects in it and the earth's surface. Normal atmospheric pressure is an indicator of 760 mm Hg. Art. (101 325 Pa). As the altitude rises, the pressure drops by 100 mm for every kilometer.
Atmosphere composition
The air shell of the Earth, consisting mainly of gases and various impurities (dust, water droplets, ice crystals, sea salts, combustion products), the amount of which is variable. The main gases are nitrogen (78%), oxygen (21%) and argon (0.93%). The concentration of gases that make up the atmosphere is practically constant, with the exception of carbon dioxide CO2 (0.03%).
The atmosphere also contains SO2, CH4, NH3, CO, hydrocarbons, HC1, HF, Hg, I2 vapors, as well as NO and many other gases in small quantities. A large amount of suspended solid and liquid particles (aerosol) is constantly found in the troposphere.
The atmosphere is one of the most important components of our planet. It is she who "shelters" people from the harsh conditions of outer space, such as solar radiation and space debris. At the same time, many facts about the atmosphere are unknown to most people.
1. True color of the sky
While it's hard to believe, the sky is actually purple. When light enters the atmosphere, air and water particles absorb the light, scattering it. At the same time, most of all dissipates purple that's why people see the blue sky.
2. An exclusive element in the Earth's atmosphere
As many remember from school, the Earth's atmosphere is composed of approximately 78% nitrogen, 21% oxygen and small impurities of argon, carbon dioxide and other gases. But few people know that our atmosphere is the only one on this moment discovered by scientists (in addition to comet 67P), which has free oxygen. Because oxygen is a highly reactive gas, it often reacts with other chemicals in space. Its pure form on Earth makes the planet habitable.
3. White stripe in the sky
Surely, some sometimes wondered why the jet plane in the sky remains white stripe... These white traces, known as contrails, are formed when hot and humid exhaust fumes from an aircraft engine mix with colder outside air. The water vapor from the exhaust gas freezes and becomes visible.
4. The main layers of the atmosphere
The Earth's atmosphere consists of five main layers that make life possible on the planet. The first of these, the troposphere, extends from sea level to an altitude of about 17 km to the equator. Most of weather phenomena happens in it.
5. Ozone layer
The next layer of the atmosphere, the stratosphere, reaches an altitude of about 50 km at the equator. It contains an ozone layer that protects people from dangerous ultraviolet rays. Even though this layer is above the troposphere, it may actually be warmer due to the absorbed energy from the sun's rays. Most jets and weather balloons fly in the stratosphere. Airplanes can fly faster in it because they are less affected by gravity and friction. Weather balloons, on the other hand, can get a better idea of storms, most of which occur lower in the troposphere.6. Mesosphere
The mesosphere is the middle layer extending up to 85 km above the planet's surface. The temperature in it fluctuates around -120 ° C. Most of the meteors that enter the Earth's atmosphere burn up in the mesosphere. The last two layers passing into space are the thermosphere and exosphere.
7. Disappearance of the atmosphere
The earth has most likely lost its atmosphere several times. When the planet was covered in oceans of magma, massive interstellar objects crashed into it. These influences, which also formed the moon, may have formed the planet's atmosphere for the first time.
8. If there were no atmospheric gases ...
Without various gases in the atmosphere, the Earth would be too cold for human existence. Water vapor, carbon dioxide and other atmospheric gases absorb heat from the sun and "distribute" it across the planet's surface, helping to create a climate suitable for habitation.
9. Formation of the ozone layer
The notorious (and essential) ozone layer was created when oxygen atoms reacted with the sun's ultraviolet light to form ozone. It is ozone that absorbs most of the harmful radiation from the sun. Despite its importance, the ozone layer was formed relatively recently after enough life arose in the oceans to release the amount of oxygen necessary to create a minimum concentration of ozone into the atmosphere.
10. Ionosphere
The ionosphere is so named because high-energy particles from space and from the Sun help form ions, creating an "electrical layer" around the planet. When satellites did not exist, this layer helped to reflect radio waves.
11. Acid rain
Acid rain, which destroys entire forests and devastates aquatic ecosystems, is formed in the atmosphere when sulfur dioxide or nitric oxide particles mix with water vapor and fall to the ground as rain. These chemical compounds are also found in nature: sulfur dioxide is produced when volcanic eruptions, and nitric oxide - during lightning strikes.
12. Lightning power
Lightning is so powerful that just one discharge can heat ambient air up to 30,000 ° C. Rapid heating causes an explosive expansion of nearby air, which is audible in the form sound wave called thunder.
Aurora Borealis and Aurora Australis (northern and southern auroras) are caused by ionic reactions occurring in the fourth level of the atmosphere, the thermosphere. When highly charged particles solar wind collide with air molecules above the planet's magnetic poles, they glow and create magnificent light shows.
14. Sunsets
Sunsets often look like burning skies, as small atmospheric particles scatter light, reflecting it in shades of orange and yellow. The same principle underlies the formation of rainbows.
In 2013, scientists discovered that tiny microbes can survive miles above the Earth's surface. At an altitude of 8-15 km above the planet, microbes were discovered that destroy organic chemical substances that float in the atmosphere, "feeding" on them.
Adherents of the theory of the apocalypse and various other horror stories will be interested to learn about.
Atmosphere(from the Greek atmos - steam and spharia - ball) - the air shell of the Earth, rotating with it. The development of the atmosphere was closely associated with the geological and geochemical processes taking place on our planet, as well as with the activities of living organisms.
The lower boundary of the atmosphere coincides with the surface of the Earth, since air penetrates into the smallest pores in the soil and is dissolved even in water.
The upper boundary at an altitude of 2000-3000 km gradually passes into outer space.
Thanks to the atmosphere, which contains oxygen, life on Earth is possible. Atmospheric oxygen is used in the process of respiration by humans, animals, and plants.
If there was no atmosphere, the earth would be as quiet as the moon. After all, sound is the vibration of air particles. The blue color of the sky is due to the fact that Sun rays passing through the atmosphere, as through a lens, they decompose into their constituent colors. At the same time, the rays of blue and blue colors are scattered most of all.
The atmosphere is delaying most ultraviolet radiation from the Sun, which has a detrimental effect on living organisms. It also keeps heat at the surface of the Earth, preventing our planet from cooling.
The structure of the atmosphere
Several layers can be distinguished in the atmosphere, differing in density and density (Fig. 1).
Troposphere
Troposphere- the lowest layer of the atmosphere, the thickness of which is 8-10 km above the poles, 10-12 km in temperate latitudes, and 16-18 km above the equator.
Rice. 1. The structure of the Earth's atmosphere
The air in the troposphere is heated from the earth's surface, that is, from land and water. Therefore, the air temperature in this layer decreases with height by an average of 0.6 ° C for every 100 m. At the upper border of the troposphere, it reaches -55 ° C. At the same time, in the equatorial area at the upper border of the troposphere, the air temperature is -70 ° С, and in the North Pole area -65 ° С.
In the troposphere, about 80% of the mass of the atmosphere is concentrated, almost all water vapor is located, thunderstorms, storms, clouds and precipitation occur, and vertical (convection) and horizontal (wind) air movement also occurs.
We can say that the weather is mainly formed in the troposphere.
Stratosphere
Stratosphere- the layer of the atmosphere located above the troposphere at an altitude of 8 to 50 km. The color of the sky in this layer appears purple, which is due to the rarefaction of the air, due to which the sun's rays are almost not scattered.
The stratosphere contains 20% of the mass of the atmosphere. The air in this layer is rarefied, there is practically no water vapor, and therefore almost no clouds and precipitation are formed. However, stable air currents are observed in the stratosphere, the speed of which reaches 300 km / h.
This layer is concentrated ozone(ozone screen, ozonosphere), a layer that absorbs ultraviolet rays, preventing them from reaching the Earth and thereby protecting living organisms on our planet. Thanks to ozone, the air temperature at the upper boundary of the stratosphere is in the range from -50 to 4-55 ° C.
Between the mesosphere and stratosphere is located transition zone- stratopause.
Mesosphere
Mesosphere- the layer of the atmosphere located at an altitude of 50-80 km. The density of air here is 200 times less than at the surface of the Earth. The color of the sky in the mesosphere appears to be black, and stars are visible during the day. The air temperature drops to -75 (-90) ° С.
At an altitude of 80 km begins thermosphere. The air temperature in this layer rises sharply to a height of 250 m, and then becomes constant: at an altitude of 150 km, it reaches 220-240 ° C; at an altitude of 500-600 km, it exceeds 1500 ° C.
In the mesosphere and thermosphere under the action cosmic rays gas molecules decay into charged (ionized) particles of atoms, therefore this part of the atmosphere is called ionosphere- a layer of very rarefied air located at an altitude of 50 to 1000 km, consisting mainly of ionized oxygen atoms, nitrogen oxide molecules and free electrons. This layer is characterized by a high electrification, and long and medium radio waves are reflected from it, as from a mirror.
In the ionosphere, auroras arise - the glow of rarefied gases under the influence of electrically charged particles flying from the Sun - and sharp fluctuations of the magnetic field are observed.
Exosphere
Exosphere- the outer layer of the atmosphere, located above 1000 km. This layer is also called the scattering sphere, since gas particles move here with high speed and can be scattered into outer space.
Atmosphere composition
The atmosphere is a mixture of gases, consisting of nitrogen (78.08%), oxygen (20.95%), carbon dioxide (0.03%), argon (0.93%), a small amount of helium, neon, xenon, krypton (0.01%), ozone and other gases, but their content is negligible (Table 1). Modern composition air of the Earth was established more than a hundred million years ago, but the sharply increased production activity of man still led to its change. Currently, there is an increase in the content of CO 2 by about 10-12%.
The gases in the atmosphere have different functional roles. However, the main significance of these gases is determined primarily by the fact that they very strongly absorb radiant energy and thus have a significant effect on temperature regime surface of the Earth and atmosphere.
Table 1. Chemical composition dry atmospheric air near the earth's surface
|
Volume concentration. % |
Molecular weight, units |
|
|
Oxygen |
||
|
Carbon dioxide |
||
|
Nitrous oxide |
||
|
from 0 to 0.00001 |
||
|
Sulfur dioxide |
from 0 to 0.000007 in summer; from 0 to 0.000002 in winter |
|
|
From 0 to 0.000002 |
46,0055/17,03061 |
|
|
Azog dioxide |
||
|
Carbon monoxide |
Nitrogen, the most widespread gas in the atmosphere, it is not chemically active.
Oxygen, unlike nitrogen, it is a very active chemical element. The specific function of oxygen is oxidation organic matter heterotrophic organisms, rocks and under-oxidized gases emitted into the atmosphere by volcanoes. Without oxygen, there would be no decomposition of dead organic matter.
The role of carbon dioxide in the atmosphere is exceptionally great. It enters the atmosphere as a result of combustion processes, respiration of living organisms, decay and is, first of all, the main construction material to create organic matter in photosynthesis. Besides, great value has the property of carbon dioxide to transmit short-wave solar radiation and absorb part of the thermal long-wave radiation, which will create the so-called Greenhouse effect, which will be discussed below.
The influence on atmospheric processes, especially on the thermal regime of the stratosphere, is also exerted by ozone. This gas serves as a natural absorber of ultraviolet radiation from the sun, and absorption of solar radiation leads to heating of the air. Average monthly values general content ozone in the atmosphere varies depending on the latitude of the area and the time of year within 0.23-0.52 cm (this is the thickness of the ozone layer at ground pressure and temperature). There is an increase in ozone content from the equator to the poles and annual course with a minimum in autumn and a maximum in spring.
A characteristic property of the atmosphere is that the content of the main gases (nitrogen, oxygen, argon) changes insignificantly with altitude: at an altitude of 65 km in the atmosphere, the content of nitrogen is 86%, oxygen is 19, argon is 0.91, and at an altitude of 95 km - nitrogen 77, oxygen - 21.3, argon - 0.82%. The constancy of the composition of atmospheric air vertically and horizontally is maintained by mixing it.
In addition to gases, the air contains water vapor and solid particles. The latter can be of both natural and artificial (anthropogenic) origin. These are pollen, tiny salt crystals, road dust, aerosol impurities. When the sun's rays enter the window, they can be seen with the naked eye.
Particles are especially abundant in the air of cities and large industrial centers, where emissions of harmful gases and their impurities formed during fuel combustion are added to aerosols.
The concentration of aerosols in the atmosphere determines the transparency of the air, which affects the solar radiation reaching the Earth's surface. The largest aerosols are condensation nuclei (from lat. condensatio- compaction, thickening) - contribute to the transformation of water vapor into water droplets.
The value of water vapor is determined primarily by the fact that it delays the long-wave thermal radiation of the earth's surface; represents the main link of large and small moisture cycles; increases the air temperature during condensation of water beds.
The amount of water vapor in the atmosphere changes over time and space. Thus, the concentration of water vapor at the earth's surface ranges from 3% in the tropics to 2-10 (15)% in Antarctica.
The average content of water vapor in the vertical column of the atmosphere in temperate latitudes is about 1.6-1.7 cm (this is the thickness of a layer of condensed water vapor). Information on water vapor in different layers of the atmosphere is contradictory. It was assumed, for example, that in the altitude range from 20 to 30 km, the specific humidity increases strongly with height. However, subsequent measurements indicate a greater dryness of the stratosphere. Apparently, the specific humidity in the stratosphere depends little on the height and amounts to 2-4 mg / kg.
The variability of the water vapor content in the troposphere is determined by the interaction of the processes of evaporation, condensation and horizontal transport. As a result of condensation of water vapor, clouds are formed and precipitation falls in the form of rain, hail and snow.
Processes phase transitions waters flow mainly in the troposphere, which is why clouds in the stratosphere (at altitudes of 20-30 km) and the mesosphere (near the mesopause), called nacreous and silvery, are relatively rare, while tropospheric clouds often cover about 50% of the entire earth's surface.
The amount of water vapor that can be contained in the air depends on the air temperature.
1 m 3 of air at a temperature of -20 ° C can contain no more than 1 g of water; at 0 ° С - no more than 5 g; at +10 ° С - no more than 9 g; at +30 ° С - no more than 30 g of water.
Output: the higher the air temperature, the more water vapor it can contain.
The air can be saturated and not saturated water vapor. So, if at a temperature of +30 ° C 1 m 3 of air contains 15 g of water vapor, the air is not saturated with water vapor; if 30 g is saturated.
Absolute humidity Is the amount of water vapor contained in 1 m 3 of air. It is expressed in grams. For example, if they say "the absolute humidity is 15", then this means that 1 m L contains 15 g of water vapor.
Relative humidity Is the ratio (in percent) of the actual water vapor content in 1 m 3 of air to the amount of water vapor that can be contained in 1 ml L at a given temperature. For example, if the radio during the broadcast of the weather report says that the relative humidity is 70%, this means that the air contains 70% of the water vapor that it can accommodate at a given temperature.
The higher the relative humidity of the air, i.e. the closer the air is to saturation, the more likely precipitation is.
Always high (up to 90%) relative humidity is observed in equatorial zone, since it is kept there throughout the year heat air and there is a lot of evaporation from the surface of the oceans. The same high relative humidity and in the polar regions, but only because at low temperatures, even a small amount of water vapor makes the air saturated or close to saturation. In temperate latitudes, the relative humidity changes with the seasons - in winter it is higher, in summer it is lower.
Especially low relative humidity of air in deserts: 1 m 1 of air there contains two to three times less than the amount of water vapor possible at a given temperature.
For measuring relative humidity use a hygrometer (from the Greek hygros - wet and metreco - I measure).
When cooling saturated air cannot hold in itself the same amount of water vapor, it thickens (condenses), turning into droplets of fog. Fog can be observed in the summer on a clear cool night.
Clouds- this is the same fog, only it is formed not near the earth's surface, but at a certain height. Rising up, the air is cooled, and the water vapor in it condenses. The resulting tiny droplets of water make up the clouds.
In the formation of clouds are involved and solid particles suspended in the troposphere.
The clouds can have different shape, which depends on the conditions of their formation (Table 14).
The lowest and heaviest clouds are stratus. They are located at an altitude of 2 km from the earth's surface. At an altitude of 2 to 8 km, more picturesque cumulus clouds can be observed. The highest and lightest are cirrus clouds. They are located at an altitude of 8 to 18 km above the earth's surface.
|
Families |
Clouds birth |
External appearance |
|
A. Clouds of the upper layer - above 6 km |
I. Cirrus |
Filiform, fibrous, white |
|
II. Cirrocumulus |
Layers and ridges of fine flakes and curls, white |
|
|
III. Cirrostratus |
Transparent whitish veil |
|
|
B. Middle clouds - above 2 km |
IV. Altocumulus |
Seams and ridges of white and gray color |
|
V. Highly layered |
Smooth shroud of milky gray |
|
|
B. Low-tier clouds - up to 2 km |
Vi. Stratus rain |
Solid shapeless gray layer |
|
Vii. Stratocumulus |
Non-translucent gray layers and ridges |
|
|
VIII. Layered |
An opaque shroud of gray |
|
|
D. Clouds of vertical development - from the lower to the upper tier |
IX. Cumulus |
Clubs and domes are bright white, with ripped edges in wind |
|
X. Cumulonimbus |
Powerful cumulus masses, dark leaden |
Protection of the atmosphere
The main source is industrial plants and automobiles. V big cities the problem of gas contamination of the main transport routes is very acute. That is why in many large cities the world, including in our country, introduced environmental control of the toxicity of vehicle exhaust gases. According to experts, smoke and dustiness of the air can halve the supply of solar energy to the earth's surface, which will lead to a change in natural conditions.
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