STRUCTURE OF THE ATMOSPHERE

Atmosphere(from other Greek ἀτμός - steam and σφαῖρα - ball) - a gaseous shell (geosphere) surrounding the planet Earth. Its inner surface covers the hydrosphere and partially the earth's crust, while its outer surface borders on the near-Earth part of outer space.

Physical properties

The thickness of the atmosphere is about 120 km from the Earth's surface. The total mass of air in the atmosphere is (5.1-5.3) 10 18 kg. Of these, the mass of dry air is (5.1352 ± 0.0003) 10 18 kg, the total mass of water vapor is on average 1.27 10 16 kg.

The molar mass of clean dry air is 28.966 g/mol, the air density at the sea surface is approximately 1.2 kg/m 3 . The pressure at 0 °C at sea level is 101.325 kPa; critical temperature - -140.7 ° C; critical pressure - 3.7 MPa; C p at 0 °C - 1.0048 10 3 J/(kg K), C v - 0.7159 10 3 J/(kg K) (at 0 °C). The solubility of air in water (by mass) at 0 ° C - 0.0036%, at 25 ° C - 0.0023%.

For "normal conditions" at the Earth's surface are taken: density 1.2 kg / m 3, barometric pressure 101.35 kPa, temperature plus 20 ° C and relative humidity 50%. These conditional indicators have a purely engineering value.

The structure of the atmosphere

The atmosphere has a layered structure. The layers of the atmosphere differ from each other in air temperature, its density, the amount of water vapor in the air and other properties.

Troposphere(ancient Greek τρόπος - "turn", "change" and σφαῖρα - "ball") - the lower, most studied layer of the atmosphere, 8-10 km high in the polar regions, up to 10-12 km in temperate latitudes, at the equator - 16-18 km.

When rising in the troposphere, the temperature drops by an average of 0.65 K every 100 m and reaches 180-220 K in the upper part. This upper layer of the troposphere, in which the decrease in temperature with height stops, is called the tropopause. The next layer of the atmosphere above the troposphere is called the stratosphere.

More than 80% of the total mass of atmospheric air is concentrated in the troposphere, turbulence and convection are highly developed, the predominant part of water vapor is concentrated, clouds arise, atmospheric fronts also form, cyclones and anticyclones develop, as well as other processes that determine weather and climate. The processes occurring in the troposphere are primarily due to convection.

The part of the troposphere within which glaciers can form on the earth's surface is called the chionosphere.

tropopause(from the Greek τροπος - turn, change and παῦσις - stop, cessation) - the layer of the atmosphere in which the decrease in temperature with height stops; transition layer from troposphere to stratosphere. In the earth's atmosphere, the tropopause is located at altitudes from 8-12 km (above sea level) in the polar regions and up to 16-18 km above the equator. The height of the tropopause also depends on the time of year (the tropopause is higher in summer than in winter) and cyclonic activity (it is lower in cyclones and higher in anticyclones)

The thickness of the tropopause ranges from several hundred meters to 2-3 kilometers. In the subtropics, tropopause ruptures are observed due to powerful jet streams. The tropopause over individual areas is often destroyed and re-formed.

Stratosphere(from Latin stratum - flooring, layer) - a layer of the atmosphere, located at an altitude of 11 to 50 km. A slight change in temperature in the 11-25 km layer (the lower layer of the stratosphere) and its increase in the 25-40 km layer from −56.5 to 0.8 °C (upper stratosphere layer or inversion region) are typical. Having reached a value of about 273 K (almost 0 °C) at an altitude of about 40 km, the temperature remains constant up to an altitude of about 55 km. This region of constant temperature is called the stratopause and is the boundary between the stratosphere and the mesosphere. The density of air in the stratosphere is tens and hundreds of times less than at sea level.

It is in the stratosphere that the ozonosphere layer (“ozone layer”) is located (at an altitude of 15-20 to 55-60 km), which determines the upper limit of life in the biosphere. Ozone (O 3 ) is formed as a result of photochemical reactions most intensively at an altitude of ~30 km. The total mass of O 3 at normal pressure would be a layer 1.7-4.0 mm thick, but even this is enough to absorb the solar ultraviolet radiation that is harmful to life. The destruction of O 3 occurs when it interacts with free radicals, NO, halogen-containing compounds (including "freons").

Most of the short-wavelength part of ultraviolet radiation (180-200 nm) is retained in the stratosphere and the energy of short waves is transformed. Under the influence of these rays, magnetic fields change, molecules break up, ionization, new formation of gases and other chemical compounds occur. These processes can be observed in the form of northern lights, lightning and other glows.

In the stratosphere and higher layers, under the influence of solar radiation, gas molecules dissociate - into atoms (above 80 km, CO 2 and H 2 dissociate, above 150 km - O 2, above 300 km - N 2). At an altitude of 200-500 km, ionization of gases also occurs in the ionosphere; at an altitude of 320 km, the concentration of charged particles (O + 2, O - 2, N + 2) is ~ 1/300 of the concentration of neutral particles. In the upper layers of the atmosphere there are free radicals - OH, HO 2, etc.

There is almost no water vapor in the stratosphere.

Flights into the stratosphere began in the 1930s. The flight on the first stratospheric balloon (FNRS-1), which Auguste Picard and Paul Kipfer made on May 27, 1931 to a height of 16.2 km, is widely known. Modern combat and supersonic commercial aircraft fly in the stratosphere at altitudes generally up to 20 km (although the dynamic ceiling can be much higher). High-altitude weather balloons rise up to 40 km; the record for an unmanned balloon is 51.8 km.

Recently, in the military circles of the United States, much attention has been paid to the development of layers of the stratosphere above 20 km, often called the "prespace" (Eng. « near space» ). It is assumed that unmanned airships and solar-powered aircraft (like NASA Pathfinder) will be able to stay at an altitude of about 30 km for a long time and provide observation and communication for very large areas, while remaining vulnerable to air defense systems; such devices will be many times cheaper than satellites.

Stratopause- the layer of the atmosphere, which is the boundary between two layers, the stratosphere and the mesosphere. In the stratosphere, temperature rises with altitude, and the stratopause is the layer where the temperature reaches its maximum. The temperature of the stratopause is about 0 °C.

This phenomenon is observed not only on Earth, but also on other planets with an atmosphere.

On Earth, the stratopause is located at an altitude of 50 - 55 km above sea level. Atmospheric pressure is about 1/1000 of the pressure at sea level.

Mesosphere(from the Greek μεσο- - “middle” and σφαῖρα - “ball”, “sphere”) - the layer of the atmosphere at altitudes from 40-50 to 80-90 km. It is characterized by an increase in temperature with height; the maximum (about +50°C) temperature is located at an altitude of about 60 km, after which the temperature begins to decrease to −70° or −80°C. Such a decrease in temperature is associated with the energetic absorption of solar radiation (radiation) by ozone. The term was adopted by the Geographical and Geophysical Union in 1951.

The gas composition of the mesosphere, as well as those of the lower atmospheric layers, is constant and contains about 80% nitrogen and 20% oxygen.

The mesosphere is separated from the underlying stratosphere by the stratopause, and from the overlying thermosphere by the mesopause. The mesopause basically coincides with the turbopause.

Meteors begin to glow and, as a rule, burn up completely in the mesosphere.

Noctilucent clouds may appear in the mesosphere.

For flights, the mesosphere is a kind of "dead zone" - the air here is too rarefied to support airplanes or balloons (at an altitude of 50 km, the air density is 1000 times less than at sea level), and at the same time too dense for artificial flights. satellites in such a low orbit. Direct studies of the mesosphere are carried out mainly with the help of suborbital meteorological rockets; in general, the mesosphere has been studied worse than other layers of the atmosphere, in connection with which scientists called it the “ignorosphere”.

mesopause

mesopause The layer of the atmosphere that separates the mesosphere and thermosphere. On Earth, it is located at an altitude of 80-90 km above sea level. In the mesopause, there is a temperature minimum, which is about −100 °C. Below (starting from a height of about 50 km) the temperature drops with height, above (up to a height of about 400 km) it rises again. The mesopause coincides with the lower boundary of the region of active absorption of the X-ray and the shortest wavelength ultraviolet radiation of the Sun. Silvery clouds are observed at this altitude.

The mesopause exists not only on Earth, but also on other planets with an atmosphere.

Karman Line- height above sea level, which is conventionally accepted as the boundary between the Earth's atmosphere and space.

As defined by the Fédération Aéronautique Internationale (FAI), the Karman Line is at an altitude of 100 km above sea level.

The height was named after Theodor von Karman, an American scientist of Hungarian origin. He was the first to determine that at about this altitude the atmosphere becomes so rarefied that aeronautics becomes impossible, since the speed of the aircraft, necessary to create sufficient lift, becomes greater than the first cosmic speed, and therefore, to achieve higher altitudes, it is necessary to use the means of astronautics.

The Earth's atmosphere continues beyond the Karman line. The outer part of the earth's atmosphere, the exosphere, extends to an altitude of 10,000 km or more, at such an altitude the atmosphere consists mainly of hydrogen atoms that can leave the atmosphere.

Reaching the Karman Line was the first condition for the Ansari X Prize, as this is the basis for recognizing the flight as a space flight.

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, because 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 envelope. 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.

The atmosphere is a mixture of various gases. It extends from the surface of the Earth to a height of up to 900 km, protecting the planet from the harmful spectrum of solar radiation, and contains gases necessary for all life on the planet. The atmosphere traps the heat of the sun, warming near the earth's surface and creating a favorable climate.

Composition of the atmosphere

The Earth's atmosphere consists mainly of two gases - nitrogen (78%) and oxygen (21%). In addition, it contains impurities of carbon dioxide and other gases. in the atmosphere exists in the form of vapor, drops of moisture in clouds and ice crystals.

Layers of the atmosphere

The atmosphere consists of many layers, between which there are no clear boundaries. The temperatures of different layers differ markedly from each other.

• airless magnetosphere. Most of the Earth's satellites fly here outside the Earth's atmosphere.
• Exosphere (450-500 km from the surface). Almost does not contain gases. Some weather satellites fly in the exosphere. The thermosphere (80-450 km) is characterized by high temperatures reaching 1700°C in the upper layer.
• Mesosphere (50-80 km). In this sphere, the temperature drops as the altitude increases. It is here that most of the meteorites (fragments of space rocks) that enter the atmosphere burn down.
• Stratosphere (15-50 km). Contains an ozone layer, i.e. a layer of ozone that absorbs ultraviolet radiation from the sun. This leads to an increase in temperature near the Earth's surface. Jet planes usually fly here, as visibility in this layer is very good and there is almost no interference caused by weather conditions.
• Troposphere. The height varies from 8 to 15 km from the earth's surface. It is here that the weather of the planet is formed, since in this layer contains the most water vapor, dust and winds. The temperature decreases with distance from the earth's surface.

Atmosphere pressure

Although we do not feel it, the layers of the atmosphere exert pressure on the surface of the Earth. The highest is near the surface, and as you move away from it, it gradually decreases. It depends on the temperature difference between land and ocean, and therefore in areas located at the same height above sea level, there is often a different pressure. Low pressure brings wet weather, while high pressure usually sets clear weather.

The movement of air masses in the atmosphere

And the pressures cause the lower atmosphere to mix. This creates winds that blow from areas of high pressure to areas of low pressure. In many regions, local winds also occur, caused by differences in land and sea temperatures. Mountains also have a significant influence on the direction of the winds.

Greenhouse effect

Carbon dioxide and other gases in the earth's atmosphere trap the sun's heat. This process is commonly called the greenhouse effect, as it is in many ways similar to the circulation of heat in greenhouses. The greenhouse effect causes global warming on the planet. In areas of high pressure - anticyclones - a clear solar one is established. In areas of low pressure - cyclones - the weather is usually unstable. Heat and light entering the atmosphere. The gases trap the heat reflected from the earth's surface, thereby causing the temperature on the earth to rise.

There is a special ozone layer in the stratosphere. Ozone blocks most of the ultraviolet radiation from the Sun, protecting the Earth and all life on it from it. Scientists have found that the cause of the destruction of the ozone layer are special chlorofluorocarbon dioxide gases contained in some aerosols and refrigeration equipment. Over the Arctic and Antarctica, huge holes have been found in the ozone layer, contributing to an increase in the amount of ultraviolet radiation affecting the Earth's surface.

Ozone is formed in the lower atmosphere as a result between solar radiation and various exhaust fumes and gases. Usually it disperses through the atmosphere, but if a closed layer of cold air forms under a layer of warm air, ozone concentrates and smog occurs. Unfortunately, this cannot make up for the loss of ozone in the ozone holes.

The satellite image clearly shows a hole in the ozone layer over Antarctica. The size of the hole varies, but scientists believe that it is constantly increasing. Attempts are being made to reduce the level of exhaust gases in the atmosphere. Reduce air pollution and use smokeless fuels in cities. Smog causes eye irritation and choking in many people.

The emergence and evolution of the Earth's atmosphere

The modern atmosphere of the Earth is the result of a long evolutionary development. It arose as a result of the joint action of geological factors and the vital activity of organisms. Throughout geological history, the earth's atmosphere has gone through several profound rearrangements. On the basis of geological data and theoretical (prerequisites), the primordial atmosphere of the young Earth, which existed about 4 billion years ago, could consist of a mixture of inert and noble gases with a small addition of passive nitrogen (N. A. Yasamanov, 1985; A. S. Monin, 1987; O. G. Sorokhtin, S. A. Ushakov, 1991, 1993. At present, the view on the composition and structure of the early atmosphere has somewhat changed. The primary atmosphere (protoatmosphere) is at the earliest protoplanetary stage. 4.2 billion years, could consist of a mixture of methane, ammonia and carbon dioxide.As a result of the degassing of the mantle and active weathering processes occurring on the earth's surface, water vapor, carbon compounds in the form of CO 2 and CO, sulfur and its compounds began to enter the atmosphere , as well as strong halogen acids - HCI, HF, HI and boric acid, which were supplemented by methane, ammonia, hydrogen, argon and some other noble gases in the atmosphere.This primary atmosphere was through extremely thin. Therefore, the temperature near the earth's surface was close to the temperature of radiative equilibrium (AS Monin, 1977).

Over time, the gas composition of the primary atmosphere began to transform under the influence of the weathering of rocks that protruded on the earth's surface, the vital activity of cyanobacteria and blue-green algae, volcanic processes and the action of sunlight. This led to the decomposition of methane into and carbon dioxide, ammonia - into nitrogen and hydrogen; carbon dioxide began to accumulate in the secondary atmosphere, which slowly descended to the earth's surface, and nitrogen. Thanks to the vital activity of blue-green algae, oxygen began to be produced in the process of photosynthesis, which, however, at the beginning was mainly spent on “oxidizing atmospheric gases, and then rocks. At the same time, ammonia, oxidized to molecular nitrogen, began to intensively accumulate in the atmosphere. It is assumed that a significant part of the nitrogen in the modern atmosphere is relict. Methane and carbon monoxide were oxidized to carbon dioxide. Sulfur and hydrogen sulfide were oxidized to SO 2 and SO 3, which, due to their high mobility and lightness, were quickly removed from the atmosphere. Thus, the atmosphere from a reducing one, as it was in the Archean and early Proterozoic, gradually turned into an oxidizing one.

Carbon dioxide entered the atmosphere both as a result of methane oxidation and as a result of degassing of the mantle and weathering of rocks. In the event that all the carbon dioxide released over the entire history of the Earth remained in the atmosphere, its partial pressure could now become the same as on Venus (O. Sorokhtin, S. A. Ushakov, 1991). But on Earth, the process was reversed. A significant part of carbon dioxide from the atmosphere was dissolved in the hydrosphere, in which it was used by aquatic organisms to build their shells and biogenically converted into carbonates. Subsequently, the most powerful strata of chemogenic and organogenic carbonates were formed from them.

Oxygen was supplied to the atmosphere from three sources. For a long time, starting from the moment of the formation of the Earth, it was released during the degassing of the mantle and was mainly spent on oxidative processes. Another source of oxygen was the photodissociation of water vapor by hard ultraviolet solar radiation. appearances; free oxygen in the atmosphere led to the death of most of the prokaryotes that lived in reducing conditions. Prokaryotic organisms have changed their habitats. They left the surface of the Earth to its depths and regions where reducing conditions were still preserved. They were replaced by eukaryotes, which began to vigorously process carbon dioxide into oxygen.

During the Archean and a significant part of the Proterozoic, almost all oxygen, arising both abiogenically and biogenically, was mainly spent on the oxidation of iron and sulfur. By the end of the Proterozoic, all metallic divalent iron that was on the earth's surface either oxidized or moved into the earth's core. This led to the fact that the partial pressure of oxygen in the early Proterozoic atmosphere changed.

In the middle of the Proterozoic, the concentration of oxygen in the atmosphere reached the Urey point and amounted to 0.01% of the current level. Starting from that time, oxygen began to accumulate in the atmosphere and, probably, already at the end of the Riphean, its content reached the Pasteur point (0.1% of the current level). It is possible that the ozone layer arose in the Vendian period and that time it never disappeared.

The appearance of free oxygen in the earth's atmosphere stimulated the evolution of life and led to the emergence of new forms with a more perfect metabolism. If earlier eukaryotic unicellular algae and cyanides, which appeared at the beginning of the Proterozoic, required an oxygen content in water of only 10 -3 of its modern concentration, then with the emergence of non-skeletal Metazoa at the end of the Early Vendian, i.e., about 650 million years ago, the oxygen concentration in the atmosphere should have been much higher. After all, Metazoa used oxygen respiration and this required that the partial pressure of oxygen reach a critical level - the Pasteur point. In this case, the anaerobic fermentation process was replaced by an energetically more promising and progressive oxygen metabolism.

After that, the further accumulation of oxygen in the earth's atmosphere occurred rather rapidly. The progressive increase in the volume of blue-green algae contributed to the achievement in the atmosphere of the oxygen level necessary for the life support of the animal world. A certain stabilization of the oxygen content in the atmosphere has occurred since the moment when the plants came to land - about 450 million years ago. The emergence of plants on land, which occurred in the Silurian period, led to the final stabilization of the level of oxygen in the atmosphere. Since that time, its concentration began to fluctuate within rather narrow limits, never going beyond the existence of life. The concentration of oxygen in the atmosphere has completely stabilized since the appearance of flowering plants. This event took place in the middle of the Cretaceous period, i.e. about 100 million years ago.

The bulk of nitrogen was formed in the early stages of the Earth's development, mainly due to the decomposition of ammonia. With the advent of organisms, the process of binding atmospheric nitrogen into organic matter and burying it in marine sediments began. After the release of organisms on land, nitrogen began to be buried in continental sediments. The processes of processing free nitrogen were especially intensified with the advent of terrestrial plants.

At the turn of the Cryptozoic and Phanerozoic, i.e., about 650 million years ago, the carbon dioxide content in the atmosphere decreased to tenths of a percent, and it reached a content close to the current level only quite recently, about 10-20 million years ago.

Thus, the gas composition of the atmosphere not only provided living space for organisms, but also determined the characteristics of their vital activity, promoted settlement and evolution. The resulting failures in the distribution of the gas composition of the atmosphere favorable for organisms, both due to cosmic and planetary causes, led to mass extinctions of the organic world, which repeatedly occurred during the Cryptozoic and at certain milestones of the Phanerozoic history.

Ethnospheric functions of the atmosphere

The Earth's atmosphere provides the necessary substance, energy and determines the direction and speed of metabolic processes. The gas composition of the modern atmosphere is optimal for the existence and development of life. As an area of ​​weather and climate formation, the atmosphere must create comfortable conditions for the life of people, animals and vegetation. Deviations in one direction or another in the quality of atmospheric air and weather conditions create extreme conditions for the life of the animal and plant world, including humans.

The atmosphere of the Earth not only provides the conditions for the existence of mankind, being the main factor in the evolution of the ethnosphere. At the same time, it turns out to be an energy and raw material resource for production. In general, the atmosphere is a factor that preserves human health, and some areas, due to physical and geographical conditions and atmospheric air quality, serve as recreational areas and are areas intended for sanatorium treatment and recreation for people. Thus, the atmosphere is a factor of aesthetic and emotional impact.

The ethnospheric and technospheric functions of the atmosphere, determined quite recently (E. D. Nikitin, N. A. Yasamanov, 2001), need an independent and in-depth study. Thus, the study of atmospheric energy functions is very relevant both from the point of view of the occurrence and operation of processes that damage the environment, and from the point of view of the impact on human health and well-being. In this case, we are talking about the energy of cyclones and anticyclones, atmospheric vortices, atmospheric pressure and other extreme atmospheric phenomena, the effective use of which will contribute to the successful solution of the problem of obtaining alternative energy sources that do not pollute the environment. After all, the air environment, especially that part of it that is located above the World Ocean, is an area for the release of a colossal amount of free energy.

For example, it has been established that tropical cyclones of average strength release energy equivalent to the energy of 500,000 atomic bombs dropped on Hiroshima and Nagasaki in just a day. For 10 days of the existence of such a cyclone, enough energy is released to meet all the energy needs of a country like the United States for 600 years.

In recent years, a large number of works by natural scientists have been published, to some extent related to various aspects of activity and the influence of the atmosphere on earth processes, which indicates the intensification of interdisciplinary interactions in modern natural science. At the same time, the integrating role of certain of its directions is manifested, among which it is necessary to note the functional-ecological direction in geoecology.

This direction stimulates the analysis and theoretical generalization of the ecological functions and the planetary role of various geospheres, and this, in turn, is an important prerequisite for the development of methodology and scientific foundations for a holistic study of our planet, the rational use and protection of its natural resources.

The Earth's atmosphere consists of several layers: troposphere, stratosphere, mesosphere, thermosphere, ionosphere and exosphere. In the upper part of the troposphere and the lower part of the stratosphere there is a layer enriched with ozone, called the ozone layer. Certain (daily, seasonal, annual, etc.) regularities in the distribution of ozone have been established. Since its inception, the atmosphere has influenced the course of planetary processes. The primary composition of the atmosphere was completely different than at present, but over time the proportion and role of molecular nitrogen steadily increased, about 650 million years ago free oxygen appeared, the amount of which continuously increased, but the concentration of carbon dioxide decreased accordingly. The high mobility of the atmosphere, its gas composition and the presence of aerosols determine its outstanding role and active participation in various geological and biospheric processes. The role of the atmosphere in the redistribution of solar energy and the development of catastrophic natural phenomena and disasters is great. Atmospheric whirlwinds - tornadoes (tornadoes), hurricanes, typhoons, cyclones and other phenomena have a negative impact on the organic world and natural systems. The main sources of pollution, along with natural factors, are various forms of human economic activity. Anthropogenic impacts on the atmosphere are expressed not only in the appearance of various aerosols and greenhouse gases, but also in an increase in the amount of water vapor, and manifest themselves in the form of smog and acid rain. Greenhouse gases change the temperature regime of the earth's surface, emissions of certain gases reduce the volume of the ozone screen and contribute to the formation of ozone holes. The ethnospheric role of the Earth's atmosphere is great.

The role of the atmosphere in natural processes

The surface atmosphere in its intermediate state between the lithosphere and outer space and its gas composition creates conditions for the life of organisms. At the same time, the weathering and intensity of destruction of rocks, the transfer and accumulation of detrital material depend on the amount, nature and frequency of precipitation, on the frequency and strength of winds, and especially on air temperature. The atmosphere is the central component of the climate system. Air temperature and humidity, cloudiness and precipitation, wind - all this characterizes the weather, that is, the continuously changing state of the atmosphere. At the same time, these same components also characterize the climate, i.e., the average long-term weather regime.

The composition of gases, the presence of clouds and various impurities, which are called aerosol particles (ash, dust, particles of water vapor), determine the characteristics of the passage of solar radiation through the atmosphere and prevent the escape of the Earth's thermal radiation into outer space.

The Earth's atmosphere is very mobile. The processes arising in it and changes in its gas composition, thickness, cloudiness, transparency and the presence of various aerosol particles in it affect both the weather and the climate.

The action and direction of natural processes, as well as life and activity on Earth, are determined by solar radiation. It gives 99.98% of the heat coming to the earth's surface. Annually it makes 134*10 19 kcal. This amount of heat can be obtained by burning 200 billion tons of coal. The reserves of hydrogen, which creates this flow of thermonuclear energy in the mass of the Sun, will be enough for at least another 10 billion years, i.e., for a period twice as long as our planet itself exists.

About 1/3 of the total amount of solar energy entering the upper boundary of the atmosphere is reflected back into the world space, 13% is absorbed by the ozone layer (including almost all ultraviolet radiation). 7% - the rest of the atmosphere and only 44% reaches the earth's surface. The total solar radiation reaching the Earth in a day is equal to the energy that humanity has received as a result of burning all types of fuel over the past millennium.

The amount and nature of the distribution of solar radiation on the earth's surface are closely dependent on the cloudiness and transparency of the atmosphere. The amount of scattered radiation is affected by the height of the Sun above the horizon, the transparency of the atmosphere, the content of water vapor, dust, the total amount of carbon dioxide, etc.

The maximum amount of scattered radiation falls into the polar regions. The lower the Sun is above the horizon, the less heat enters a given area.

Atmospheric transparency and cloudiness are of great importance. On a cloudy summer day, it is usually colder than on a clear one, since daytime clouds prevent the earth's surface from heating.

The dust content of the atmosphere plays an important role in the distribution of heat. The finely dispersed solid particles of dust and ash in it, which affect its transparency, adversely affect the distribution of solar radiation, most of which is reflected. Fine particles enter the atmosphere in two ways: either ashes thrown out during volcanic eruptions, or desert dust carried by winds from arid tropical and subtropical regions. Especially a lot of such dust is formed during droughts, when it is carried into the upper layers of the atmosphere by streams of warm air and can stay there for a long time. After the eruption of the Krakatoa volcano in 1883, dust thrown tens of kilometers into the atmosphere remained in the stratosphere for about 3 years. As a result of the 1985 eruption of the El Chichon volcano (Mexico), dust reached Europe, and therefore there was a slight decrease in surface temperatures.

The Earth's atmosphere contains a variable amount of water vapor. In absolute terms, by weight or volume, its amount ranges from 2 to 5%.

Water vapor, like carbon dioxide, enhances the greenhouse effect. In the clouds and fogs that arise in the atmosphere, peculiar physicochemical processes take place.

The primary source of water vapor in the atmosphere is the surface of the oceans. A layer of water 95 to 110 cm thick annually evaporates from it. Part of the moisture returns to the ocean after condensation, and the other is directed towards the continents by air currents. In regions with a variable-humid climate, precipitation moistens the soil, and in humid regions it creates groundwater reserves. Thus, the atmosphere is an accumulator of humidity and a reservoir of precipitation. and fogs that form in the atmosphere provide moisture to the soil cover and thus play a decisive role in the development of the animal and plant world.

Atmospheric moisture is distributed over the earth's surface due to the mobility of the atmosphere. It has a very complex system of winds and pressure distribution. Due to the fact that the atmosphere is in continuous motion, the nature and extent of the distribution of wind flows and pressure are constantly changing. The scales of circulation vary from micrometeorological, with a size of only a few hundred meters, to a global one, with a size of several tens of thousands of kilometers. Huge atmospheric vortices are involved in the creation of systems of large-scale air currents and determine the general circulation of the atmosphere. In addition, they are sources of catastrophic atmospheric phenomena.

The distribution of weather and climatic conditions and the functioning of living matter depend on atmospheric pressure. In the event that atmospheric pressure fluctuates within small limits, it does not play a decisive role in the well-being of people and the behavior of animals and does not affect the physiological functions of plants. As a rule, frontal phenomena and weather changes are associated with pressure changes.

Atmospheric pressure is of fundamental importance for the formation of wind, which, being a relief-forming factor, has the strongest effect on flora and fauna.

The wind is able to suppress the growth of plants and at the same time promotes the transfer of seeds. The role of the wind in the formation of weather and climatic conditions is great. He also acts as a regulator of sea currents. Wind as one of the exogenous factors contributes to the erosion and deflation of weathered material over long distances.

Ecological and geological role of atmospheric processes

The decrease in the transparency of the atmosphere due to the appearance of aerosol particles and solid dust in it affects the distribution of solar radiation, increasing the albedo or reflectivity. Various chemical reactions lead to the same result, causing the decomposition of ozone and the generation of "pearl" clouds, consisting of water vapor. Global change in reflectivity, as well as changes in the gas composition of the atmosphere, mainly greenhouse gases, are the cause of climate change.

Uneven heating, which causes differences in atmospheric pressure over different parts of the earth's surface, leads to atmospheric circulation, which is the hallmark of the troposphere. When there is a difference in pressure, air rushes from areas of high pressure to areas of low pressure. These movements of air masses, together with humidity and temperature, determine the main ecological and geological features of atmospheric processes.

Depending on the speed, the wind produces various geological work on the earth's surface. At a speed of 10 m/s, it shakes thick branches of trees, picks up and carries dust and fine sand; breaks tree branches at a speed of 20 m/s, carries sand and gravel; at a speed of 30 m/s (storm) rips off the roofs of houses, uproots trees, breaks poles, moves pebbles and carries small gravel, and a hurricane at a speed of 40 m/s destroys houses, breaks and demolishes poles of power lines, uproots large trees.

Squall storms and tornadoes (tornadoes) have a great negative environmental impact with catastrophic consequences - atmospheric vortices that occur in the warm season on powerful atmospheric fronts with a speed of up to 100 m/s. Squalls are horizontal whirlwinds with hurricane wind speeds (up to 60-80 m/s). They are often accompanied by heavy showers and thunderstorms lasting from a few minutes to half an hour. The squalls cover areas up to 50 km wide and travel a distance of 200-250 km. A heavy storm in Moscow and the Moscow region in 1998 damaged the roofs of many houses and knocked down trees.

Tornadoes, called tornadoes in North America, are powerful funnel-shaped atmospheric eddies often associated with thunderclouds. These are columns of air narrowing in the middle with a diameter of several tens to hundreds of meters. The tornado has the appearance of a funnel, very similar to an elephant's trunk, descending from the clouds or rising from the surface of the earth. Possessing a strong rarefaction and high rotation speed, the tornado travels up to several hundred kilometers, drawing in dust, water from reservoirs and various objects. Powerful tornadoes are accompanied by thunderstorms, rain and have great destructive power.

Tornadoes rarely occur in subpolar or equatorial regions, where it is constantly cold or hot. Few tornadoes in the open ocean. Tornadoes occur in Europe, Japan, Australia, the USA, and in Russia they are especially frequent in the Central Black Earth region, in the Moscow, Yaroslavl, Nizhny Novgorod and Ivanovo regions.

Tornadoes lift and move cars, houses, wagons, bridges. Particularly destructive tornadoes (tornadoes) are observed in the United States. From 450 to 1500 tornadoes are recorded annually, with an average of about 100 victims. Tornadoes are fast-acting catastrophic atmospheric processes. They are formed in just 20-30 minutes, and their existence time is 30 minutes. Therefore, it is almost impossible to predict the time and place of occurrence of tornadoes.

Other destructive, but long-term atmospheric vortices are cyclones. They are formed due to a pressure drop, which, under certain conditions, contributes to the occurrence of a circular movement of air currents. Atmospheric vortices originate around powerful ascending currents of humid warm air and rotate at high speed clockwise in the southern hemisphere and counterclockwise in the northern hemisphere. Cyclones, unlike tornadoes, originate over the oceans and produce their destructive actions over the continents. The main destructive factors are strong winds, intense precipitation in the form of snowfall, downpours, hail and surge floods. Winds with speeds of 19 - 30 m / s form a storm, 30 - 35 m / s - a storm, and more than 35 m / s - a hurricane.

Tropical cyclones - hurricanes and typhoons - have an average width of several hundred kilometers. The wind speed inside the cyclone reaches hurricane force. Tropical cyclones last from several days to several weeks, moving at a speed of 50 to 200 km/h. Mid-latitude cyclones have a larger diameter. Their transverse dimensions range from a thousand to several thousand kilometers, the wind speed is stormy. They move in the northern hemisphere from the west and are accompanied by hail and snowfall, which are catastrophic. Cyclones and their associated hurricanes and typhoons are the largest natural disasters after floods in terms of the number of victims and damage caused. In densely populated areas of Asia, the number of victims during hurricanes is measured in the thousands. In 1991, in Bangladesh, during a hurricane that caused the formation of sea waves 6 m high, 125 thousand people died. Typhoons cause great damage to the United States. As a result, dozens and hundreds of people die. In Western Europe, hurricanes cause less damage.

Thunderstorms are considered a catastrophic atmospheric phenomenon. They occur when warm, moist air rises very quickly. On the border of the tropical and subtropical zones, thunderstorms occur for 90-100 days a year, in the temperate zone for 10-30 days. In our country, the largest number of thunderstorms occurs in the North Caucasus.

Thunderstorms usually last less than an hour. Intense downpours, hailstorms, lightning strikes, gusts of wind, and vertical air currents pose a particular danger. The hail hazard is determined by the size of the hailstones. In the North Caucasus, the mass of hailstones once reached 0.5 kg, and in India, hailstones weighing 7 kg were noted. The most hazardous areas in our country are located in the North Caucasus. In July 1992, hail damaged 18 aircraft at the Mineralnye Vody airport.

Lightning is a hazardous weather phenomenon. They kill people, livestock, cause fires, damage the power grid. About 10,000 people die every year from thunderstorms and their consequences worldwide. Moreover, in some parts of Africa, in France and the United States, the number of victims from lightning is greater than from other natural phenomena. The annual economic damage from thunderstorms in the United States is at least $700 million.

Droughts are typical for desert, steppe and forest-steppe regions. The lack of precipitation causes drying up of the soil, lowering the level of groundwater and in reservoirs until they dry up completely. Moisture deficiency leads to the death of vegetation and crops. Droughts are especially severe in Africa, the Near and Middle East, Central Asia and southern North America.

Droughts change the conditions of human life, have an adverse impact on the natural environment through processes such as salinization of the soil, dry winds, dust storms, soil erosion and forest fires. Fires are especially strong during drought in taiga regions, tropical and subtropical forests and savannahs.

Droughts are short-term processes that last for one season. When droughts last more than two seasons, there is a threat of starvation and mass mortality. Typically, the effect of drought extends to the territory of one or more countries. Especially often prolonged droughts with tragic consequences occur in the Sahel region of Africa.

Atmospheric phenomena such as snowfalls, intermittent heavy rains and prolonged prolonged rains cause great damage. Snowfalls cause massive avalanches in the mountains, and the rapid melting of the fallen snow and prolonged heavy rains lead to floods. A huge mass of water falling on the earth's surface, especially in treeless areas, causes severe erosion of the soil cover. There is an intensive growth of ravine-beam systems. Floods occur as a result of large floods during a period of heavy precipitation or floods after a sudden warming or spring snowmelt and, therefore, are atmospheric phenomena in origin (they are discussed in the chapter on the ecological role of the hydrosphere).

Anthropogenic changes in the atmosphere

Currently, there are many different sources of anthropogenic nature that cause atmospheric pollution and lead to serious violations of the ecological balance. In terms of scale, two sources have the greatest impact on the atmosphere: transport and industry. On average, transport accounts for about 60% of the total amount of atmospheric pollution, industry - 15%, thermal energy - 15%, technologies for the destruction of household and industrial waste - 10%.

Transport, depending on the fuel used and the types of oxidizing agents, emits into the atmosphere nitrogen oxides, sulfur, oxides and dioxides of carbon, lead and its compounds, soot, benzopyrene (a substance from the group of polycyclic aromatic hydrocarbons, which is a strong carcinogen that causes skin cancer).

Industry emits sulfur dioxide, carbon oxides and dioxides, hydrocarbons, ammonia, hydrogen sulfide, sulfuric acid, phenol, chlorine, fluorine and other compounds and chemicals into the atmosphere. But the dominant position among emissions (up to 85%) is occupied by dust.

As a result of pollution, the transparency of the atmosphere changes, aerosols, smog and acid rains appear in it.

Aerosols are dispersed systems consisting of solid particles or liquid droplets suspended in a gaseous medium. The particle size of the dispersed phase is usually 10 -3 -10 -7 cm Depending on the composition of the dispersed phase, aerosols are divided into two groups. One includes aerosols consisting of solid particles dispersed in a gaseous medium, the second - aerosols, which are a mixture of gaseous and liquid phases. The first are called smokes, and the second - fogs. Condensation centers play an important role in the process of their formation. Volcanic ash, cosmic dust, products of industrial emissions, various bacteria, etc. act as condensation nuclei. The number of possible sources of concentration nuclei is constantly growing. So, for example, when dry grass is destroyed by fire on an area of ​​4000 m 2, an average of 11 * 10 22 aerosol nuclei is formed.

Aerosols began to form from the moment of the emergence of our planet and influenced natural conditions. However, their number and actions, balanced with the general circulation of substances in nature, did not cause deep ecological changes. Anthropogenic factors of their formation shifted this balance towards significant biospheric overloads. This feature has been especially pronounced since mankind began to use specially created aerosols both in the form of toxic substances and for plant protection.

The most dangerous for vegetation cover are aerosols of sulfur dioxide, hydrogen fluoride and nitrogen. When in contact with a wet leaf surface, they form acids that have a detrimental effect on living things. Acid mists, together with the inhaled air, enter the respiratory organs of animals and humans, and aggressively affect the mucous membranes. Some of them decompose living tissue, and radioactive aerosols cause cancer. Among radioactive isotopes, SG 90 is of particular danger not only because of its carcinogenicity, but also as an analogue of calcium, replacing it in the bones of organisms, causing their decomposition.

During nuclear explosions, radioactive aerosol clouds form in the atmosphere. Small particles with a radius of 1 - 10 microns fall not only into the upper layers of the troposphere, but also into the stratosphere, in which they are able to stay for a long time. Aerosol clouds are also formed during the operation of reactors of industrial plants that produce nuclear fuel, as well as as a result of accidents at nuclear power plants.

Smog is a mixture of aerosols with liquid and solid dispersed phases that form a foggy curtain over industrial areas and large cities.

There are three types of smog: ice, wet and dry. Ice smog is called Alaskan. This is a combination of gaseous pollutants with the addition of dusty particles and ice crystals that occur when fog droplets and steam from heating systems freeze.

Wet smog, or London-type smog, is sometimes called winter smog. It is a mixture of gaseous pollutants (mainly sulfur dioxide), dust particles and fog droplets. The meteorological prerequisite for the appearance of winter smog is calm weather, in which a layer of warm air is located above the surface layer of cold air (below 700 m). At the same time, not only horizontal, but also vertical exchange is absent. Pollutants, which are usually dispersed in high layers, in this case accumulate in the surface layer.

Dry smog occurs during the summer and is often referred to as LA-type smog. It is a mixture of ozone, carbon monoxide, nitrogen oxides and acid vapors. Such smog is formed as a result of the decomposition of pollutants by solar radiation, especially its ultraviolet part. The meteorological prerequisite is atmospheric inversion, which is expressed in the appearance of a layer of cold air above the warm one. Gases and solid particles usually lifted by warm air currents are then dispersed in the upper cold layers, but in this case they accumulate in the inversion layer. In the process of photolysis, nitrogen dioxides formed during the combustion of fuel in car engines decompose:

NO 2 → NO + O

Then ozone synthesis occurs:

O + O 2 + M → O 3 + M

NO + O → NO 2

Photodissociation processes are accompanied by a yellow-green glow.

In addition, reactions occur according to the type: SO 3 + H 2 0 -> H 2 SO 4, i.e. strong sulfuric acid is formed.

With a change in meteorological conditions (the appearance of wind or a change in humidity), the cold air dissipates and the smog disappears.

The presence of carcinogens in smog leads to respiratory failure, irritation of the mucous membranes, circulatory disorders, asthmatic suffocation, and often death. Smog is especially dangerous for young children.

Acid rain is atmospheric precipitation acidified by industrial emissions of sulfur oxides, nitrogen oxides and vapors of perchloric acid and chlorine dissolved in them. In the process of burning coal and gas, most of the sulfur in it, both in the form of oxide and in compounds with iron, in particular in pyrite, pyrrhotite, chalcopyrite, etc., turns into sulfur oxide, which, together with carbon dioxide, is released into atmosphere. When atmospheric nitrogen and technical emissions are combined with oxygen, various nitrogen oxides are formed, and the volume of nitrogen oxides formed depends on the combustion temperature. The bulk of nitrogen oxides occurs during the operation of vehicles and diesel locomotives, and a smaller part occurs in the energy sector and industrial enterprises. Sulfur and nitrogen oxides are the main acid formers. When reacting with atmospheric oxygen and the water vapor in it, sulfuric and nitric acids are formed.

It is known that the alkaline-acid balance of the medium is determined by the pH value. A neutral environment has a pH value of 7, an acidic environment has a pH value of 0, and an alkaline environment has a pH value of 14. In the modern era, the pH value of rainwater is 5.6, although in the recent past it was neutral. A decrease in pH value by one corresponds to a tenfold increase in acidity and, therefore, at present, rains with increased acidity fall almost everywhere. The maximum acidity of rains recorded in Western Europe was 4-3.5 pH. It should be taken into account that the pH value equal to 4-4.5 is fatal for most fish.

Acid rains have an aggressive effect on the Earth's vegetation cover, on industrial and residential buildings and contribute to a significant acceleration of the weathering of exposed rocks. An increase in acidity prevents the self-regulation of neutralization of soils in which nutrients are dissolved. In turn, this leads to a sharp decrease in yields and causes degradation of the vegetation cover. The acidity of the soil contributes to the release of heavy, which are in a bound state, which are gradually absorbed by plants, causing serious tissue damage in them and penetrating into the human food chain.

A change in the alkaline-acid potential of sea waters, especially in shallow waters, leads to the cessation of the reproduction of many invertebrates, causes the death of fish and disrupts the ecological balance in the oceans.

As a result of acid rain, the forests of Western Europe, the Baltic States, Karelia, the Urals, Siberia and Canada are under the threat of death.

The role of the atmosphere in the life of the Earth

The atmosphere is the source of oxygen that people breathe. However, as you ascend to altitude, the total atmospheric pressure drops, resulting in a decrease in partial oxygen pressure.

The human lungs contain approximately three liters of alveolar air. If the atmospheric pressure is normal, then the partial oxygen pressure in the alveolar air will be 11 mm Hg. Art., pressure of carbon dioxide - 40 mm Hg. Art., and water vapor - 47 mm Hg. Art. With an increase in altitude, oxygen pressure decreases, and the pressure of water vapor and carbon dioxide in the lungs in total will remain constant - approximately 87 mm Hg. Art. When the air pressure equals this value, oxygen will stop flowing into the lungs.

Due to the decrease in atmospheric pressure at an altitude of 20 km, water and interstitial body fluid in the human body will boil here. If you do not use a pressurized cabin, at such a height a person will die almost instantly. Therefore, from the point of view of the physiological characteristics of the human body, "space" originates from a height of 20 km above sea level.

The role of the atmosphere in the life of the Earth is very great. So, for example, thanks to dense air layers - the troposphere and stratosphere, people are protected from radiation exposure. In space, in rarefied air, at an altitude of over 36 km, ionizing radiation acts. At an altitude of over 40 km - ultraviolet.

When rising above the Earth's surface to a height of over 90-100 km, there will be a gradual weakening, and then the complete disappearance of phenomena familiar to humans, observed in the lower atmospheric layer:

Sound does not propagate.

There is no aerodynamic force and drag.

Heat is not transferred by convection, etc.

The atmospheric layer protects the Earth and all living organisms from cosmic radiation, from meteorites, is responsible for regulating seasonal temperature fluctuations, balancing and equalizing daily ones. In the absence of an atmosphere on Earth, the daily temperature would fluctuate within +/-200С˚. The atmospheric layer is a life-giving "buffer" between the earth's surface and outer space, a carrier of moisture and heat; processes of photosynthesis and energy exchange take place in the atmosphere - the most important biospheric processes.

Layers of the atmosphere in order from the Earth's surface

The atmosphere is a layered structure, which is the following layers of the atmosphere in order from the surface of the Earth:

Troposphere.

Stratosphere.

Mesosphere.

Thermosphere.

Exosphere

Each layer does not have sharp boundaries between them, and their height is affected by latitude and seasons. This layered structure was formed as a result of temperature changes at different heights. It is thanks to the atmosphere that we see twinkling stars.

The structure of the Earth's atmosphere by layers:

What is the earth's atmosphere made of?

Each atmospheric layer differs in temperature, density and composition. The total thickness of the atmosphere is 1.5-2.0 thousand km. What is the earth's atmosphere made of? At present, it is a mixture of gases with various impurities.

Troposphere

The structure of the Earth's atmosphere begins with the troposphere, which is the lower part of the atmosphere about 10-15 km high. This is where most of the atmospheric air is concentrated. A characteristic feature of the troposphere is a drop in temperature of 0.6 ˚C as you rise up for every 100 meters. The troposphere has concentrated in itself almost all atmospheric water vapor, and clouds are also formed here.

The height of the troposphere changes daily. In addition, its average value varies depending on the latitude and the season of the year. The average height of the troposphere above the poles is 9 km, above the equator - about 17 km. The average annual air temperature over the equator is close to +26 ˚C, and over the North Pole -23 ˚C. The upper line of the boundary of the troposphere above the equator is the average annual temperature of about -70 ˚C, and over the north pole in summer -45 ˚C and in winter -65 ˚C. Thus, the higher the altitude, the lower the temperature. The rays of the sun pass freely through the troposphere, heating the surface of the Earth. The heat radiated by the sun is retained by carbon dioxide, methane and water vapor.

Stratosphere

Above the layer of the troposphere is the stratosphere, which is 50-55 km in height. The peculiarity of this layer is the increase in temperature with height. Between the troposphere and stratosphere lies a transitional layer called the tropopause.

Approximately from a height of 25 kilometers, the temperature of the stratospheric layer begins to increase and, upon reaching a maximum height of 50 km, it acquires values ​​from +10 to +30 ˚C.

There is very little water vapor in the stratosphere. Sometimes at an altitude of about 25 km you can find quite thin clouds, which are called "mother-of-pearl". In the daytime, they are not noticeable, but at night they glow due to the illumination of the sun, which is below the horizon. The composition of mother-of-pearl clouds is supercooled water droplets. The stratosphere is made up mostly of ozone.

Mesosphere

The height of the mesosphere layer is approximately 80 km. Here, as it rises upwards, the temperature decreases and at the uppermost boundary it reaches values ​​several tens of C˚ below zero. In the mesosphere, clouds can also be observed, which are presumably formed from ice crystals. These clouds are called "silvery". The mesosphere is characterized by the coldest temperature in the atmosphere: from -2 to -138 ˚C.

Thermosphere

This atmospheric layer got its name due to high temperatures. The thermosphere is made up of:

Ionosphere.

exospheres.

The ionosphere is characterized by rarefied air, each centimeter of which at an altitude of 300 km consists of 1 billion atoms and molecules, and at an altitude of 600 km - more than 100 million.

The ionosphere is also characterized by high air ionization. These ions are composed of charged oxygen atoms, charged molecules of nitrogen atoms and free electrons.

Exosphere

From a height of 800-1000 km, the exospheric layer begins. Gas particles, especially light ones, move here at great speed, overcoming the force of gravity. Such particles, due to their rapid movement, fly out of the atmosphere into outer space and disperse. Therefore, the exosphere is called the sphere of scattering. It is predominantly hydrogen atoms that fly into space, which make up the highest layers of the exosphere. Thanks to particles in the upper atmosphere and particles of the solar wind, we can observe the northern lights.

Satellites and geophysical rockets made it possible to establish the presence in the upper atmosphere of the planet's radiation belt, which consists of electrically charged particles - electrons and protons.

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 connected 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 limit at an altitude of 2000-3000 km gradually passes into outer space.

Oxygen-rich atmosphere makes life possible on Earth. Atmospheric oxygen is used in the process of breathing by humans, animals, and plants.

If there were 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 explained by the fact that the sun's rays, passing through the atmosphere, as if through a lens, are decomposed into their component colors. In this case, the rays of blue and blue colors are scattered most of all.

The atmosphere retains most of the 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, whose thickness above the poles is 8-10 km, in temperate latitudes - 10-12 km, and above the equator - 16-18 km.

Rice. 1. The structure of the Earth's atmosphere

The air in the troposphere is heated from the earth's surface, i.e. 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 boundary of the troposphere, it reaches -55 °C. At the same time, in the region of the equator at the upper boundary of the troposphere, the air temperature is -70 °С, and in the region of the North Pole -65 °С.

About 80% of the mass of the atmosphere is concentrated in the troposphere, almost all water vapor is located, thunderstorms, storms, clouds and precipitation occur, and vertical (convection) and horizontal (wind) air movement 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 explained by the rarefaction of the air, due to which the sun's rays almost do not scatter.

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 clouds and precipitation are almost not 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 passing to the Earth and thereby protecting living organisms on our planet. Due 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 the stratosphere there is a transitional zone - the stratopause.

Mesosphere

Mesosphere- a layer of the atmosphere located at an altitude of 50-80 km. The air density here is 200 times less than at the surface of the Earth. The color of the sky in the mesosphere appears black, 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 a height 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 of cosmic rays, gas molecules break up into charged (ionized) particles of atoms, so 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, nitric oxide molecules and free electrons. This layer is characterized by 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 in 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 at high speed and can be scattered into outer space.

Composition of the atmosphere

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). The modern composition of the Earth's air was established more than a hundred million years ago, but the sharply increased human production activity nevertheless led to its change. Currently, there is an increase in the content of CO 2 by about 10-12%.

The gases that make up the atmosphere perform various 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 the temperature regime of the Earth's surface and atmosphere.

Table 1. Chemical composition of dry atmospheric air near the earth's surface

	Volume concentration. %	Molecular weight, units
Oxygen
Carbon dioxide
Nitrous oxide
	0 to 0.00001
Sulfur dioxide	from 0 to 0.000007 in summer; 0 to 0.000002 in winter
	From 0 to 0.000002	46,0055/17,03061
Azog dioxide
Carbon monoxide

Nitrogen, the most common gas in the atmosphere, chemically little active.

Oxygen, unlike nitrogen, is a chemically very active element. The specific function of oxygen is the oxidation of organic matter of heterotrophic organisms, rocks, and incompletely 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 the processes of combustion, respiration of living organisms, decay and is, first of all, the main building material for the creation of organic matter during photosynthesis. In addition, the property of carbon dioxide to transmit short-wave solar radiation and absorb part of thermal long-wave radiation is of great importance, 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 solar ultraviolet radiation, and the absorption of solar radiation leads to air heating. The average monthly values ​​of the total ozone content in the atmosphere vary depending on the latitude of the area and the season within 0.23-0.52 cm (this is the thickness of the ozone layer at ground pressure and temperature). There is an increase in the ozone content from the equator to the poles and an annual variation with a minimum in autumn and a maximum in spring.

A characteristic property of the atmosphere can be called the fact that the content of the main gases (nitrogen, oxygen, argon) changes slightly with height: at an altitude of 65 km in the atmosphere, the content of nitrogen is 86%, oxygen - 19, argon - 0.91, 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 its mixing.

In addition to gases, air contains water vapor and solid particles. The latter can have both natural and artificial (anthropogenic) origin. These are flower pollen, tiny salt crystals, road dust, aerosol impurities. When the sun's rays penetrate the window, they can be seen with the naked eye.

There are especially many particulate matter 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; raises the temperature of the air when the water beds condense.

The amount of water vapor in the atmosphere varies over time and space. Thus, the concentration of water vapor near 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 (the layer of condensed water vapor will have such a thickness). Information about 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 strongly increases with height. However, subsequent measurements indicate a greater dryness of the stratosphere. Apparently, the specific humidity in the stratosphere depends little on height and amounts to 2–4 mg/kg.

The variability of water vapor content in the troposphere is determined by the interaction of evaporation, condensation, and horizontal transport. As a result of the condensation of water vapor, clouds form and precipitation occurs in the form of rain, hail and snow.

The processes of phase transitions of water proceed mainly in the troposphere, which is why clouds in the stratosphere (at altitudes of 20-30 km) and mesosphere (near the mesopause), called mother-of-pearl and silver, are observed relatively rarely, while tropospheric clouds often cover about 50% of the entire earth surfaces.

The amount of water vapor that can be contained in the air depends on the temperature of the air.

1 m 3 of air at a temperature of -20 ° C can contain no more than 1 g of water; at 0 °C - no more than 5 g; at +10 °С - no more than 9 g; at +30 °С - no more than 30 g of water.

Conclusion: The higher the air temperature, the more water vapor it can contain.

Air can be rich and not saturated steam. 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 - saturated.

Absolute humidity- this is the amount of water vapor contained in 1 m 3 of air. It is expressed in grams. For example, if they say "absolute humidity is 15", then this means that 1 mL contains 15 g of water vapor.

Relative humidity- this is the ratio (in percent) of the actual content of water vapor in 1 m 3 of air to the amount of water vapor that can be contained in 1 m L at a given temperature. For example, if the radio during the transmission of the weather report reported that the relative humidity is 70%, this means that the air contains 70% of the water vapor that it can hold at a given temperature.

The greater the relative humidity of the air, t. the closer the air is to saturation, the more likely it is to fall.

Always high (up to 90%) relative humidity is observed in the equatorial zone, since there is a high air temperature throughout the year and there is a large evaporation from the surface of the oceans. The same high relative humidity is 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, relative humidity varies seasonally - it is higher in winter and lower in summer.

The relative humidity of the air is especially low 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.

To measure relative humidity, a hygrometer is used (from the Greek hygros - wet and metreco - I measure).

When cooled, saturated air cannot retain the same amount of water vapor in itself, 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 at the earth's surface, but at a certain height. As the air rises, it cools and the water vapor in it condenses. The resulting tiny droplets of water make up the clouds.

involved in the formation of clouds particulate matter suspended in the troposphere.

Clouds can have a 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	Kinds of clouds	Appearance
A. Upper clouds - above 6 km	I. Pinnate	Threadlike, fibrous, white
	II. cirrocumulus	Layers and ridges of small flakes and curls, white
	III. Cirrostratus	Transparent whitish veil
B. Clouds of the middle layer - above 2 km	IV. Altocumulus	Layers and ridges of white and gray
	V. Altostratus	Smooth veil of milky gray color
B. Lower clouds - up to 2 km	VI. Nimbostratus	Solid shapeless gray layer
	VII. Stratocumulus	Opaque layers and ridges of gray
	VIII. layered	Illuminated gray veil
D. Clouds of vertical development - from the lower to the upper tier	IX. Cumulus	Clubs and domes bright white, with torn edges in the wind
	X. Cumulonimbus	Powerful cumulus-shaped masses of dark lead color

Atmospheric protection

The main sources are industrial enterprises and automobiles. In large cities, the problem of gas contamination of the main transport routes is very acute. That is why in many large cities of the world, including our country, environmental control of the toxicity of car exhaust gases has been introduced. According to experts, smoke and dust in the air can halve the flow of solar energy to the earth's surface, which will lead to a change in natural conditions.