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

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

The lowest atmospheric layer is the troposphere, the upper boundary of which is called the tropopause, depending on geographical latitude varies and ranges from 8 km. in the polar up to 20 km. in tropical latitudes. In middle or temperate latitudes, its upper limit lies at altitudes of 10-12 km. Throughout the year, the upper limit of the troposphere experiences fluctuations depending on the flow of solar radiation. So, as a result of probing South Pole Earth, the US Meteorological Service has revealed that from March to August or September there is a steady cooling of the troposphere, as a result of which for a short period in August or September its boundary rises to 11.5 km. Then, in the period from September to December, it quickly decreases and reaches its lowest position - 7.5 km, after which its height remains virtually unchanged until March. Those. The troposphere reaches its greatest thickness in summer and its thinnest in winter.

It is worth noting that, in addition to seasonal ones, there are also daily fluctuations in the height of the tropopause. Also, its position is influenced by cyclones and anticyclones: in the first, it falls, because The pressure in them is lower than in the surrounding air, and secondly, it rises accordingly.

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

The greenhouse effect is associated with a decrease in air temperature in the troposphere with height (since the warmed Earth more heat releases to ground layers). The average vertical gradient is 0.65°/100 m (i.e., the air temperature decreases by 0.65° C for every 100 meters of rise). So, if the average annual air temperature at the surface of the Earth near the equator is +26°, then at the upper boundary it is -70°. The temperature in the tropopause region above the North Pole varies throughout the year from -45° in summer to -65° in winter.

With increasing altitude, air pressure also decreases, amounting to only 12-20% of the near-surface level at the upper boundary of the troposphere.

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

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

Under the influence of high-altitude jet currents, breaks often form in the tropopause, and at times it disappears altogether, although it then forms anew. This is especially often observed in subtropical latitudes, which are dominated by a powerful subtropical high-altitude current. In addition, the difference in tropopause layers in ambient temperature leads to the formation of gaps. For example, a large gap exists between the warm and low polar tropopause and the high and cold tropopause of tropical latitudes. Recently, a layer of the tropopause of temperate latitudes has also emerged, which has discontinuities with the previous two layers: polar and tropical.

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

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

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

There is little water vapor in the stratosphere. The air here is very dry, and therefore few clouds form. Only at altitudes of 20-25 km and in high latitudes can you notice very thin pearlescent clouds consisting of supercooled water droplets. During the day, these clouds are not visible, but with the onset of darkness they seem to glow due to the illumination of them by the Sun, which has already set below the horizon.

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

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

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

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

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

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

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

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

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

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

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

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

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

STRUCTURE OF THE ATMOSPHERE

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

Physical properties

The thickness of the atmosphere is approximately 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, and the density of air at the sea surface is approximately 1.2 kg/m3. 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). Solubility of air in water (by mass) at 0 °C - 0.0036%, at 25 °C - 0.0023%.

The following are accepted as “normal conditions” at the Earth’s surface: density 1.2 kg/m3, barometric pressure 101.35 kPa, temperature plus 20 °C and relative humidity 50%. These conditional indicators have purely engineering significance.

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 decreases 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, located 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 form, cyclones and anticyclones develop, as well as other processes that determine weather and climate. The processes occurring in the troposphere are caused primarily by convection.

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

Tropopause(from the Greek τροπος - turn, change and παῦσις - stop, termination) - a layer of the atmosphere in which the decrease in temperature with height stops; transition layer from the troposphere to the 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 (in summer the tropopause is located higher than in winter) and cyclonic activity (in cyclones it is lower, and in anticyclones it is higher)

The thickness of the tropopause ranges from several hundred meters to 2-3 kilometers. In the subtropics, tropopause breaks are observed due to powerful jet currents. The tropopause over certain 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. Characterized by a slight change in temperature in the 11-25 km layer (lower layer of the stratosphere) and an increase in temperature in the 25-40 km layer from −56.5 to 0.8 ° C (upper layer of the stratosphere or inversion region). 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 mesosphere. The air density in the stratosphere is tens and hundreds of times less than at sea level.

It is in the stratosphere that the ozone 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 would amount to a layer 1.7-4.0 mm thick at normal pressure, but this is enough to absorb life-destructive ultraviolet radiation from the Sun. The destruction of O 3 occurs when it interacts with free radicals, NO, and halogen-containing compounds (including “freons”).

In the stratosphere, most of the short-wave part of ultraviolet radiation (180-200 nm) is retained and the energy of short waves is transformed. Under the influence of these rays, magnetic fields change, molecules disintegrate, ionization occurs, and new formation of gases and other chemical compounds occurs. 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 upper layers 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 was made by Auguste Picard and Paul Kipfer on May 27, 1931 to an altitude 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 US military circles, much attention has been paid to the development of layers of the stratosphere above 20 km, often called “pre-space”. « near space» ). It is assumed that unmanned airships and solar-powered aircraft (like NASA Pathfinder) will be able to remain at an altitude of about 30 km for a long time and provide surveillance and communications to very large areas, while remaining low-vulnerable to air defense systems; Such devices will be many times cheaper than satellites.

Stratopause- a layer of the atmosphere that is the boundary between two layers, the stratosphere and the mesosphere. In the stratosphere, temperature increases with increasing 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 that have an atmosphere.

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

Mesosphere(from the Greek μεσο- - “middle” and σφαῖρα - “ball”, “sphere”) - a layer of the atmosphere at altitudes from 40-50 to 80-90 km. Characterized by an increase in temperature with altitude; 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. This decrease in temperature is associated with the vigorous 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, like that of the underlying 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. Mesopause basically coincides with turbopause.

Meteors begin to glow and, as a rule, completely burn up 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 low orbit. Direct studies of the mesosphere are carried out mainly using suborbital weather rockets; In general, the mesosphere has been studied less well than other layers of the atmosphere, which is why scientists have nicknamed it the “ignorosphere.”

Mesopause

Mesopause- a 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. At the mesopause there is a temperature minimum, which is about −100 °C. Below (starting from an altitude of about 50 km) the temperature drops with height, higher (up to an altitude of about 400 km) it rises again. The mesopause coincides with the lower boundary of the region of active absorption of X-ray and short-wave ultraviolet radiation from the Sun. At this altitude noctilucent clouds are observed.

Mesopause occurs not only on Earth, but also on other planets that have an atmosphere.

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

According to the Fédération Aéronautique Internationale (FAI) definition, the Karman line is located at an altitude of 100 km above sea level.

The height was named after Theodore von Karman, an American scientist of Hungarian origin. He was the first to determine that at approximately this altitude the atmosphere becomes so rarefied that aeronautics becomes impossible, since the speed of the aircraft required to create sufficient lift becomes greater than the first cosmic speed, and therefore, to achieve greater altitudes it is necessary to use 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 thousand km or more; at this altitude, the atmosphere consists mainly of hydrogen atoms that are capable of leaving the atmosphere.

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

Space is filled with energy. Energy fills space unevenly. There are places of its concentration and discharge. This way you can estimate the density. The planet is an ordered system, with a maximum density of matter in the center and a gradual decrease in concentration towards the periphery. Interaction forces determine the state of matter, the form in which it exists. Physics describes the state of aggregation of substances: solid, liquid, gas and so on.

The atmosphere is the gaseous environment surrounding the planet. The Earth's atmosphere allows for free movement and allows light to pass through, creating space in which life thrives.

The area from the surface of the earth to an altitude of approximately 16 kilometers (from the equator to the poles the value is smaller, also depends on the season) is called the troposphere. The troposphere is a layer in which about 80% of all atmospheric air and almost all water vapor are concentrated. This is where the processes that shape the weather take place. Pressure and temperature fall with altitude. The reason for the decrease in air temperature is an adiabatic process; during expansion, the gas cools. At the upper boundary of the troposphere, values can reach -50, -60 degrees Celsius.

Next comes the Stratosphere. It extends up to 50 kilometers. In this layer of the atmosphere, the temperature increases with height, acquiring a value at the top point of about 0 C. The increase in temperature is caused by the process of absorption of ultraviolet rays by the ozone layer. Radiation causes a chemical reaction. Oxygen molecules break down into single atoms, which can combine with normal oxygen molecules to form ozone.

Radiation from the sun with wavelengths between 10 and 400 nanometers is classified as ultraviolet. The shorter the wavelength of UV radiation, the greater the danger it poses to living organisms. Only a small fraction of radiation reaches the Earth's surface, and the less active part of its spectrum. This feature of nature allows a person to get a healthy sun tan.

The next layer of the atmosphere is called the Mesosphere. Limits from approximately 50 km to 85 km. In the mesosphere, the concentration of ozone, which could trap UV energy, is low, so the temperature again begins to fall with height. At the peak point, the temperature drops to -90 C, some sources indicate a value of -130 C. Most meteoroids burn up in this layer of the atmosphere.

The layer of the atmosphere, stretching from a height of 85 km to a distance of 600 km from the Earth, is called the Thermosphere. The thermosphere is the first to meet solar radiation, including the so-called vacuum ultraviolet.

Vacuum UV is retained by the air, thereby heating this layer of the atmosphere to enormous temperatures. However, since the pressure here is extremely low, this seemingly hot gas does not have the same effect on objects as under conditions on the surface of the earth. On the contrary, objects placed in such an environment will cool down.

At an altitude of 100 km there passes the conventional line “Karman line”, which is considered to be the beginning of space.

Auroras occur in the thermosphere. In this layer of the atmosphere, the solar wind interacts with the planet's magnetic field.

The last layer The atmosphere is the Exosphere, the outer shell extending for thousands of kilometers. The exosphere is practically empty place However, the number of atoms wandering here is an order of magnitude greater than in interplanetary space.

A man breathes air. Normal pressure is 760 millimeters of mercury. At an altitude of 10,000 m the pressure is about 200 mm. Hg Art. At such a height a person can probably breathe, at least for a short time, but this requires preparation. The state will clearly be inoperable.

Gas composition of the atmosphere: 78% nitrogen, 21% oxygen, about a percent argon; the rest is a mixture of gases representing the smallest fraction of the total.

10.045×10 3 J/(kg*K) (in the temperature range from 0-100°C), C v 8.3710*10 3 J/(kg*K) (0-1500°C). The solubility of air in water at 0°C is 0.036%, at 25°C - 0.22%.

Atmospheric composition

History of atmospheric formation

Early history

Currently, science cannot trace all stages of the formation of the Earth with one hundred percent accuracy. According to the most common theory, the Earth's atmosphere has had four different compositions over time. Initially, it consisted of light gases (hydrogen and helium) captured from interplanetary space. This is the so-called primary atmosphere. At the next stage, active volcanic activity led to the saturation of the atmosphere with gases other than hydrogen (hydrocarbons, ammonia, water vapor). This is how it was formed secondary atmosphere. This atmosphere was restorative. Further, the process of atmosphere formation was determined by the following factors:

constant leakage of hydrogen into interplanetary space;
chemical reactions occurring in the atmosphere under the influence of ultraviolet radiation, lightning discharges and some other factors.

Gradually these factors led to the formation tertiary atmosphere, characterized by a much lower content of hydrogen and a much higher content of nitrogen and carbon dioxide(formed as a result chemical reactions from ammonia and hydrocarbons).

The emergence of life and oxygen

With the appearance of living organisms on Earth as a result of photosynthesis, accompanied by the release of oxygen and the absorption of carbon dioxide, the composition of the atmosphere began to change. There is, however, data (analysis of the isotopic composition of atmospheric oxygen and that released during photosynthesis) that indicates the geological origin of atmospheric oxygen.

Initially, oxygen was spent on the oxidation of reduced compounds - hydrocarbons, ferrous form of iron contained in the oceans, etc. At the end of this stage, the oxygen content in the atmosphere began to increase.

In the 1990s, experiments were carried out to create a closed ecological system (“Biosphere 2”), during which it was not possible to create a stable system with a uniform air composition. The influence of microorganisms led to a decrease in oxygen levels and an increase in the amount of carbon dioxide.

Nitrogen

The formation of a large amount of N 2 is due to the oxidation of the primary ammonia-hydrogen atmosphere with molecular O 2, which began to come from the surface of the planet as a result of photosynthesis, supposedly about 3 billion years ago (according to another version, atmospheric oxygen is of geological origin). Nitrogen is oxidized to NO in the upper atmosphere, used in industry and bound by nitrogen-fixing bacteria, while N2 is released into the atmosphere as a result of denitrification of nitrates and other nitrogen-containing compounds.

Nitrogen N 2 is an inert gas and reacts only under specific conditions (for example, during a lightning discharge). Cyanobacteria and some bacteria (for example, nodule bacteria that form rhizobial symbiosis with leguminous plants) can oxidize it and convert it into biological form.

Oxidation of molecular nitrogen by electrical discharges is used in industrial production nitrogen fertilizers, it also led to the formation of unique saltpeter deposits in the Chilean Atacama Desert.

Noble gases

Fuel combustion is the main source of polluting gases (CO, NO, SO2). Sulfur dioxide is oxidized by air O 2 to SO 3 in the upper layers of the atmosphere, which interacts with H 2 O and NH 3 vapors, and the resulting H 2 SO 4 and (NH 4) 2 SO 4 return to the Earth's surface along with precipitation. The use of internal combustion engines leads to significant atmospheric pollution with nitrogen oxides, hydrocarbons and Pb compounds.

Aerosol pollution of the atmosphere is due to both natural causes (volcanic eruptions, dust storms, entrainment of droplets sea water and plant pollen particles, etc.), and economic activity people (ore mining and building materials, fuel combustion, cement production, etc.). Intensive large-scale emission of solid particles into the atmosphere is one of the possible reasons changes in the planet's climate.

The structure of the atmosphere and characteristics of individual shells

The physical state of the atmosphere is determined by weather and climate. Basic parameters of the atmosphere: air density, pressure, temperature and composition. As altitude increases, air density and atmospheric pressure decrease. Temperature also changes with changes in altitude. Vertical structure The atmosphere 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 neighboring shells are called tropopause, stratopause, etc., respectively.

Troposphere

Stratosphere

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 - H 2). At an altitude of 100-400 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.

Mesosphere

Up to an altitude of 100 km, the atmosphere is a homogeneous, well-mixed mixture of gases. In higher layers, the distribution of gases by height depends on their molecular masses; the concentration of heavier gases decreases faster with distance from the Earth's surface. Due to a decrease in gas density, the temperature drops from 0°C in the stratosphere to −110°C in the mesosphere. However, the kinetic energy of individual particles at altitudes of 200-250 km corresponds to a temperature of ~1500°C. Above 200 km, significant fluctuations in temperature and gas density in time and space are observed.

At an altitude of about 2000-3000 km, the exosphere gradually turns into the so-called near-space vacuum, which is filled with highly rarefied particles of interplanetary gas, mainly hydrogen atoms. But this gas represents only part of the interplanetary matter. The other part consists of dust 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. Based on the electrical properties in the atmosphere, the neutronosphere and ionosphere are distinguished. It is currently believed that the atmosphere extends to an altitude of 2000-3000 km.

Depending on the composition of the gas in the atmosphere, they emit homosphere And heterosphere. Heterosphere- This is the area where gravity affects the separation of gases, since their mixing at such an altitude is negligible. This implies a 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 properties

Already at an altitude of 5 km above sea level, an untrained person begins to experience oxygen starvation and without adaptation, a person’s performance is significantly reduced. The physiological zone of the atmosphere ends here. Human breathing becomes impossible at an altitude of 15 km, although up to approximately 115 km the atmosphere contains oxygen.

The atmosphere supplies us with the oxygen necessary for breathing. However, due to the drop in the total pressure of the atmosphere, as you rise to altitude, the partial pressure of oxygen decreases accordingly.

The human lungs constantly contain about 3 liters of alveolar air. Partial pressure of oxygen in alveolar air at normal atmospheric pressure is 110 mm Hg. Art., carbon dioxide pressure - 40 mm Hg. Art., and water vapor −47 mm Hg. Art. With increasing altitude, oxygen pressure drops, and the total vapor pressure of water and carbon dioxide in the lungs remains almost constant - about 87 mm Hg. Art. The supply of oxygen to the lungs will completely stop when the ambient air pressure becomes equal to this value.

At an altitude of about 19-20 km, the atmospheric pressure drops to 47 mm Hg. Art. Therefore, at this altitude, water and interstitial fluid begin to boil in the human body. Outside the pressurized cabin at these altitudes, death occurs almost instantly. Thus, from the point of view of human physiology, “space” begins already at an altitude of 15-19 km.

Dense layers of air - the troposphere and stratosphere - protect us from the damaging effects of radiation. With sufficient rarefaction of air, at altitudes of more than 36 km, ionizing radiation - primary cosmic rays - has an intense effect on the body; At altitudes of more than 40 km, the ultraviolet part of the solar spectrum is dangerous for humans.

Everyone who has flown on an airplane is accustomed to this kind of message: “our flight takes place at an altitude of 10,000 m, the temperature outside is 50 ° C.” It seems nothing special. The farther from the surface of the Earth heated by the Sun, the colder it is. Many people think that the temperature decreases continuously with altitude and that the temperature gradually drops, approaching the temperature of space. By the way, scientists thought so until the end of the 19th century.

Let's take a closer look at the distribution of air temperature over the Earth. The atmosphere is divided into several layers, which primarily reflect the nature of temperature changes.

The lower layer of the atmosphere is called troposphere, which means “sphere of rotation.” All changes in weather and climate are the result of physical processes occurring precisely in this layer. The upper boundary of this layer is located where the decrease in temperature with height is replaced by its increase - approximately at an altitude of 15-16 km above the equator and 7-8 km above the poles. Like the Earth itself, the atmosphere, under the influence of the rotation of our planet, is also somewhat flattened above the poles and swells above the equator. However, this effect is expressed in the atmosphere much more strongly than in the solid shell of the Earth. In the direction from the Earth's surface to At the upper boundary of the troposphere, the air temperature decreases. Above the equator minimum temperature air is about -62°C, and above the poles about -45°C. At temperate latitudes, more than 75% of the mass of the atmosphere is in the troposphere. In the tropics, about 90% of the mass of the atmosphere is located within the troposphere.

In 1899, a minimum was found in the vertical temperature profile at a certain altitude, and then the temperature increased slightly. The beginning of this increase means the transition to the next layer of the atmosphere - to stratosphere, which means “layer sphere.” The term stratosphere means and reflects the previous idea of the uniqueness of the layer lying above the troposphere. The stratosphere extends to an altitude of about 50 km above the earth’s surface. Its peculiarity is, in particular, a sharp increase in air temperature. This increase in temperature is explained ozone formation reaction is one of the main chemical reactions occurring in the atmosphere.

The bulk of ozone is concentrated at altitudes of approximately 25 km, but in general the ozone layer is a highly extended shell, covering almost the entire stratosphere. The interaction of oxygen with ultraviolet rays is one of the beneficial processes in the earth’s atmosphere that contributes to the maintenance of life on Earth. The absorption of this energy by ozone prevents its excessive flow to the earth's surface, where exactly the level of energy that is suitable for the existence of terrestrial life forms is created. The ozonosphere absorbs some of the radiant energy passing through the atmosphere. As a result, a vertical air temperature gradient of approximately 0.62°C per 100 m is established in the ozonosphere, i.e., the temperature increases with altitude up to the upper limit of the stratosphere - the stratopause (50 km), reaching, according to some data, 0°C.

At altitudes from 50 to 80 km there is a layer of the atmosphere called mesosphere. The word "mesosphere" means "intermediate sphere", where the air temperature continues to decrease with height. Above the mesosphere, in a layer called thermosphere, the temperature rises again with altitude up to about 1000°C, and then drops very quickly to -96°C. However, it does not drop indefinitely, then the temperature increases again.

Thermosphere is the first layer ionosphere. Unlike the previously mentioned layers, the ionosphere is not distinguished by temperature. The ionosphere is an area of electrical nature that makes many types of radio communications possible. The ionosphere is divided into several layers, designated by the letters D, E, F1 and F2. These layers also have special names. The separation into layers is caused by several reasons, among which the most important is the unequal influence of the layers on the passage of radio waves. The lowest layer, D, mainly absorbs radio waves and thereby prevents their further propagation. The best studied layer E is located at an altitude of approximately 100 km above the earth's surface. It is also called the Kennelly-Heaviside layer after the names of the American and English scientists who simultaneously and independently discovered it. Layer E, like a giant mirror, reflects radio waves. Thanks to this layer, long radio waves travel further distances than would be expected if they propagated only in a straight line, without being reflected from the E layer. The F layer has similar properties. It is also called the Appleton layer. Together with the Kennelly-Heaviside layer, it reflects radio waves to terrestrial radio stations. Such reflection can occur at various angles. The Appleton layer is located at an altitude of about 240 km.

The outermost region of the atmosphere, the second layer of the ionosphere, is often called exosphere. This term refers to the existence of the outskirts of space near the Earth. It is difficult to determine exactly where the atmosphere ends and space begins, since the density increases with height. atmospheric gases decreases gradually and the atmosphere itself gradually turns into almost a vacuum, in which only individual molecules occur. Already at an altitude of approximately 320 km, the density of the atmosphere is so low that molecules can travel more than 1 km without colliding with each other. The outermost part of the atmosphere serves as its upper boundary, which is located at altitudes from 480 to 960 km.

More information about processes in the atmosphere can be found on the website “Earth Climate”