The atmosphere of the earth and its constituent parts. Layers of the atmosphere in order from the earth's surface. The structure of the gas shell of the Earth

At sea level, 1013.25 hPa (about 760 mm Hg). The global average air temperature at the Earth's surface is 15 ° C, while the temperature varies from about 57 ° C in subtropical deserts to -89 ° C in Antarctica. Air density and pressure decrease with height according to a law close to exponential.

The structure of the atmosphere... Vertically, the atmosphere has a layered structure, determined mainly by the features of the vertical temperature distribution (figure), which depends on the geographic location, season, time of day, and so on. The lower layer of the atmosphere - the troposphere - is characterized by a drop in temperature with height (by about 6 ° C per 1 km), its height is from 8-10 km in polar latitudes to 16-18 km in the tropics. Due to the rapid decrease in air density with height, about 80% of the total mass of the atmosphere is in the troposphere. Above the troposphere is the stratosphere - a layer that is generally characterized by an increase in temperature with height. The transitional layer between the troposphere and stratosphere is called the tropopause. In the lower stratosphere, up to a level of about 20 km, the temperature changes little with height (the so-called isothermal region) and often even slightly decreases. Above, the temperature rises due to the absorption of UV radiation from the Sun by ozone, at first slowly, and from a level of 34-36 km - faster. The upper boundary of the stratosphere - the stratopause - is located at an altitude of 50-55 km, corresponding to the maximum temperature (260-270 K). The layer of the atmosphere, located at an altitude of 55-85 km, where the temperature again drops with altitude, is called the mesosphere, at its upper boundary - the mesopause - the temperature reaches 150-160 K in summer, and 200-230 K in winter. Above the mesopause begins the thermosphere - a layer, characterized by a rapid increase in temperature, reaching 800-1200 K at an altitude of 250 km. The thermosphere absorbs corpuscular and X-ray radiation from the Sun, decelerates and burns meteors, therefore it performs the function of a protective layer of the Earth. Even higher is the exosphere, from where atmospheric gases are scattered into world space due to dissipation and where there is a gradual transition from the atmosphere to interplanetary space.

Atmosphere composition... Up to an altitude of about 100 km, the atmosphere is practically homogeneous in chemical composition and the average molecular weight of air (about 29) is constant in it. Near the Earth's surface, the atmosphere consists of nitrogen (about 78.1% by volume) and oxygen (about 20.9%), and also contains small amounts of argon, carbon dioxide (carbon dioxide), neon and other constant and variable components (see Air ).

In addition, the atmosphere contains small amounts of ozone, nitrogen oxides, ammonia, radon, etc. The relative content of the main constituents of the air is constant over time and uniformly in different geographic regions. The content of water vapor and ozone is variable in space and time; despite their low content, their role in atmospheric processes is very significant.

Above 100-110 km, oxygen, carbon dioxide and water vapor molecules dissociate, so the molecular mass of air decreases. At an altitude of about 1000 km, light gases begin to dominate - helium and hydrogen, and even higher, the Earth's atmosphere gradually turns into interplanetary gas.

The most important variable component of the atmosphere is water vapor, which is released into the atmosphere by evaporation from the surface of water and moist soil, as well as by transpiration by plants. The relative content of water vapor varies near the earth's surface from 2.6% in the tropics to 0.2% at polar latitudes. With height, it quickly falls, decreasing by half already at an altitude of 1.5-2 km. The vertical column of the atmosphere in temperate latitudes contains about 1.7 cm of "precipitated water layer". When water vapor condenses, clouds are formed, from which atmospheric precipitation falls in the form of rain, hail, snow.

An important component of atmospheric air is ozone, which is concentrated 90% in the stratosphere (between 10 and 50 km), about 10% of it is in the troposphere. Ozone absorbs hard UV radiation (with a wavelength of less than 290 nm), and this is its protective role for the biosphere. The values ​​of the total ozone content vary depending on latitude and season in the range from 0.22 to 0.45 cm (the thickness of the ozone layer at a pressure of p = 1 atm and a temperature of T = 0 ° C). In ozone holes observed in spring in Antarctica since the early 1980s, the ozone content can fall to 0.07 cm.It increases from the equator to the poles and has an annual variation with a maximum in spring and a minimum in autumn, and the amplitude of the annual variation is small in the tropics and grows towards high latitudes. A significant variable component of the atmosphere is carbon dioxide, the content of which in the atmosphere has increased by 35% over the past 200 years, which is mainly explained by an anthropogenic factor. Its latitudinal and seasonal variability is observed, associated with photosynthesis of plants and solubility in seawater (according to Henry's law, the solubility of gas in water decreases with an increase in its temperature).

An important role in the formation of the planet's climate is played by atmospheric aerosol - solid and liquid particles suspended in the air, ranging in size from several nm to tens of microns. Aerosols of natural and anthropogenic origin are distinguished. Aerosol is formed in the process of gas-phase reactions from the waste products of plants and human economic activities, volcanic eruptions, as a result of the rise of dust by the wind from the surface of the planet, especially from its desert regions, and is also formed from cosmic dust falling into the upper atmosphere. Most of the aerosol is concentrated in the troposphere; aerosol from volcanic eruptions forms the so-called Junge layer at an altitude of about 20 km. The largest amount of anthropogenic aerosol enters the atmosphere as a result of the operation of vehicles and thermal power plants, chemical production, fuel combustion, etc. Therefore, in some regions, the composition of the atmosphere differs markedly from ordinary air, which required the creation of a special service for monitoring and monitoring the level of atmospheric air pollution.

Evolution of the atmosphere... The modern atmosphere has, apparently, a secondary origin: it was formed from gases released by the solid shell of the Earth after the completion of the formation of the planet about 4.5 billion years ago. During the geological history of the Earth, the atmosphere has undergone significant changes in its composition under the influence of a number of factors: dissipation (volatilization) of gases, mainly lighter ones, into outer space; release of gases from the lithosphere as a result of volcanic activity; chemical reactions between components of the atmosphere and rocks that make up the earth's crust; photochemical reactions in the atmosphere itself under the influence of solar UV radiation; accretion (capture) of matter of the interplanetary medium (for example, meteoric matter). The development of the atmosphere is closely related to geological and geochemical processes, and the last 3-4 billion years also with the activity of the biosphere. A significant part of the gases that make up the modern atmosphere (nitrogen, carbon dioxide, water vapor) arose during volcanic activity and intrusion that carried them out of the depths of the Earth. Oxygen appeared in noticeable quantities about 2 billion years ago as a result of the activity of photosynthetic organisms that originally originated in the surface waters of the ocean.

Based on the data on the chemical composition of carbonate deposits, estimates of the amount of carbon dioxide and oxygen in the atmosphere of the geological past were obtained. Throughout the Phanerozoic (the last 570 million years of Earth's history), the amount of carbon dioxide in the atmosphere varied widely in accordance with the level of volcanic activity, ocean temperature and the level of photosynthesis. For most of this time, the concentration of carbon dioxide in the atmosphere was significantly higher than today (up to 10 times). The amount of oxygen in the Phanerozoic atmosphere changed significantly, and the tendency to increase it prevailed. In the Precambrian atmosphere, the mass of carbon dioxide was, as a rule, greater, and the mass of oxygen, less than in the Phanerozoic atmosphere. Fluctuations in the amount of carbon dioxide in the past had a significant impact on the climate, intensifying the greenhouse effect when the concentration of carbon dioxide increased, due to which the climate during the main part of the Phanerozoic was much warmer than in the modern era.

Atmosphere and life... Without the atmosphere, the Earth would be a dead planet. Organic life takes place in close interaction with the atmosphere and the associated climate and weather. Small in mass compared to the planet as a whole (about a millionth part), the atmosphere is a sine qua non for all life forms. Oxygen, nitrogen, water vapor, carbon dioxide, ozone are of the greatest importance for the vital activity of organisms. When carbon dioxide is absorbed by photosynthetic plants, organic matter is created, which is used as a source of energy by the vast majority of living things, including humans. Oxygen is necessary for the existence of aerobic organisms, for which the flow of energy is provided by the oxidation reactions of organic matter. Nitrogen, assimilated by some microorganisms (nitrogen fixers), is necessary for the mineral nutrition of plants. Ozone, which absorbs the hard UV radiation of the Sun, significantly attenuates this part of the solar radiation, which is harmful to life. Condensation of water vapor in the atmosphere, the formation of clouds and the subsequent precipitation of atmospheric precipitation supply water to land, without which no life forms are possible. The vital activity of organisms in the hydrosphere is largely determined by the amount and chemical composition of atmospheric gases dissolved in water. Since the chemical composition of the atmosphere depends significantly on the activities of organisms, the biosphere and atmosphere can be considered as part of a single system, the maintenance and evolution of which (see Biogeochemical cycles) was of great importance for changing the composition of the atmosphere throughout the history of the Earth as a planet.

Radiation, heat and water balances of the atmosphere... Solar radiation is practically the only source of energy for all physical processes in the atmosphere. The main feature of the radiation regime of the atmosphere is the so-called greenhouse effect: the atmosphere transmits solar radiation to the earth's surface well enough, but actively absorbs long-wave thermal radiation of the earth's surface, part of which returns to the surface in the form of counter radiation, which compensates for the radiation heat loss by the earth's surface (see Atmospheric radiation ). In the absence of the atmosphere, the average temperature of the earth's surface would be -18 ° C, in reality it is 15 ° C. The incoming solar radiation is partially (about 20%) absorbed into the atmosphere (mainly by water vapor, water droplets, carbon dioxide, ozone and aerosols), and is also scattered (about 7%) by aerosol particles and density fluctuations (Rayleigh scattering). The total radiation, reaching the earth's surface, is partially (about 23%) reflected from it. The reflectance is determined by the reflectivity of the underlying surface, the so-called albedo. On average, the Earth's albedo for the integral solar radiation flux is close to 30%. It varies from a few percent (dry soil and chernozem) to 70-90% for freshly fallen snow. Radiation heat exchange between the Earth's surface and the atmosphere depends significantly on the albedo and is determined by the effective radiation of the Earth's surface and the counter-radiation of the atmosphere absorbed by it. The algebraic sum of radiation fluxes entering the Earth's atmosphere from outer space and leaving it back is called the radiation balance.

Transformations of solar radiation after its absorption by the atmosphere and the earth's surface determine the heat balance of the Earth as a planet. The main source of heat for the atmosphere is the earth's surface; heat from it is transferred not only in the form of long-wave radiation, but also by convection, and is also released during condensation of water vapor. The shares of these heat inflows are on average 20%, 7% and 23%, respectively. This also adds about 20% of the heat due to the absorption of direct solar radiation. The solar radiation flux per unit time through a unit area perpendicular to the sun's rays and located outside the atmosphere at an average distance from the Earth to the Sun (the so-called solar constant) is 1367 W / m2, the changes are 1-2 W / m2, depending on cycle of solar activity. With a planetary albedo of about 30%, the time-average global inflow of solar energy to the planet is 239 W / m2. Since the Earth as a planet emits the same amount of energy into space on average, then, according to the Stefan-Boltzmann law, the effective temperature of the outgoing thermal long-wave radiation is 255 K (-18 ° C). At the same time, the average temperature of the earth's surface is 15 ° C. The difference of 33 ° C is due to the greenhouse effect.

The water balance of the atmosphere as a whole corresponds to the equality of the amount of moisture evaporated from the Earth's surface and the amount of precipitation falling on the Earth's surface. The atmosphere over the oceans receives more moisture from evaporation processes than over land, and loses 90% in the form of precipitation. Excess water vapor over the oceans is carried to the continents by air currents. The amount of water vapor transported into the atmosphere from the oceans to the continents is equal to the volume of the rivers flowing into the oceans.

Air movement... The Earth has a spherical shape, so much less solar radiation comes to its high latitudes than to the tropics. As a result, large temperature contrasts arise between latitudes. The temperature distribution is also significantly influenced by the relative position of the oceans and continents. Due to the large mass of oceanic waters and the high heat capacity of water, seasonal fluctuations in the temperature of the ocean surface are much less than that of land. In this regard, in the middle and high latitudes, the air temperature over the oceans in summer is noticeably lower than over the continents, and higher in winter.

Unequal heating of the atmosphere in different regions of the globe causes a non-uniform distribution of atmospheric pressure in space. At sea level, the pressure distribution is characterized by relatively low values ​​near the equator, an increase in the subtropics (high pressure belts) and a decrease in the middle and high latitudes. At the same time, over the continents of extratropical latitudes, the pressure is usually increased in winter and decreased in summer, which is associated with the temperature distribution. Under the influence of a pressure gradient, the air experiences acceleration from areas of high pressure to areas of low pressure, which leads to the movement of air masses. The moving air masses are also affected by the deflecting force of the Earth's rotation (Coriolis force), the friction force, which decreases with height, and with curvilinear trajectories, the centrifugal force. Turbulent mixing of air is of great importance (see Turbulence in the atmosphere).

A complex system of air currents (general circulation of the atmosphere) is associated with the planetary pressure distribution. In the meridional plane, on average, two or three cells of meridional circulation are traced. Near the equator, heated air rises and falls in the subtropics, forming the Hadley cell. In the same place, the air of the Ferrell return cell is lowered. At high latitudes, a straight polar cell is often traced. The meridional circulation velocities are of the order of 1 m / s or less. Due to the action of the Coriolis force, westerly winds are observed in most of the atmosphere with velocities in the middle troposphere of about 15 m / s. There are relatively stable wind systems. These include the trade winds - winds blowing from high-pressure belts in the subtropics to the equator with a noticeable eastern component (from east to west). Monsoons are fairly stable - air currents with a clearly pronounced seasonal character: they blow from the ocean to the mainland in summer and in the opposite direction in winter. The monsoons of the Indian Ocean are especially regular. In the middle latitudes, the movement of air masses is mainly westerly (from west to east). This is a zone of atmospheric fronts, on which large eddies arise - cyclones and anticyclones, covering many hundreds and even thousands of kilometers. Cyclones also occur in the tropics; here they are smaller, but very high wind speeds reaching hurricane force (33 m / s and more), the so-called tropical cyclones. In the Atlantic and in the east of the Pacific they are called hurricanes, and in the west of the Pacific they are called typhoons. In the upper troposphere and lower stratosphere, in the regions separating the direct cell of the Hadley meridional circulation and the reverse Ferrell cell, relatively narrow, hundreds of kilometers wide, jet currents with sharply delineated boundaries are often observed, within which the wind reaches 100-150 and even 200 m / with.

Climate and weather... The difference in the amount of solar radiation arriving at different latitudes to the earth's surface with various physical properties determines the diversity of the Earth's climates. From the equator to tropical latitudes, the air temperature near the earth's surface averages 25-30 ° C and varies little throughout the year. In the equatorial belt, there is usually a lot of precipitation, which creates conditions for excessive moisture there. In tropical zones, the amount of precipitation decreases and in some areas becomes very low. The vast deserts of the Earth are located here.

In subtropical and middle latitudes, the air temperature varies significantly throughout the year, and the difference between the temperatures of summer and winter is especially great in areas of continents far from the oceans. Thus, in some regions of Eastern Siberia, the annual amplitude of air temperature reaches 65 ° C. Humidification conditions at these latitudes are very diverse, depend mainly on the general circulation of the atmosphere and vary significantly from year to year.

In polar latitudes, the temperature remains low throughout the year, even if there is a noticeable seasonal variation. This contributes to the widespread distribution of ice cover on the oceans and land and permafrost, which occupies over 65% of its area in Russia, mainly in Siberia.

Over the past decades, changes in the global climate have become more and more noticeable. Temperatures rise more at high latitudes than at low ones; more in winter than in summer; more at night than during the day. Over the 20th century, the average annual air temperature near the earth's surface in Russia has increased by 1.5-2 ° C, and in some regions of Siberia there is an increase of several degrees. This is associated with an increase in the greenhouse effect due to an increase in the concentration of trace gases.

The weather is determined by the conditions of atmospheric circulation and the geographic location of the terrain; it is most stable in the tropics and most variable in the middle and high latitudes. Most of all, the weather changes in the zones of change in air masses, caused by the passage of atmospheric fronts, cyclones and anticyclones, carrying precipitation and increased wind. Data for weather forecasting is collected at ground-based weather stations, ships and aircraft, from meteorological satellites. See also Meteorology.

Optical, acoustic and electrical phenomena in the atmosphere... With the propagation of electromagnetic radiation in the atmosphere as a result of refraction, absorption and scattering of light by air and various particles (aerosol, ice crystals, water droplets), various optical phenomena arise: rainbows, crowns, halos, mirage, etc. Light scattering determines the apparent height of the sky and blue sky. The visibility range of objects is determined by the conditions of light propagation in the atmosphere (see Atmospheric visibility). The communication range and the ability to detect objects by instruments, including the possibility of astronomical observations from the Earth's surface, depend on the transparency of the atmosphere at different wavelengths. The phenomenon of twilight plays an important role in studies of optical inhomogeneities in the stratosphere and mesosphere. For example, photographing twilight from spacecraft makes it possible to detect aerosol layers. The features of the propagation of electromagnetic radiation in the atmosphere determine the accuracy of methods for remote sensing of its parameters. All these questions, like many others, are studied by atmospheric optics. Refraction and scattering of radio waves determine the possibilities of radio reception (see Propagation of radio waves).

Sound propagation in the atmosphere depends on the spatial distribution of temperature and wind speed (see Atmospheric Acoustics). It is of interest for remote sensing of the atmosphere. Explosions of charges launched by rockets into the upper atmosphere provided a wealth of information about the wind systems and the course of temperature in the stratosphere and mesosphere. In a stably stratified atmosphere, when the temperature decreases with altitude more slowly than the adiabatic gradient (9.8 K / km), so-called internal waves arise. These waves can propagate upward into the stratosphere and even into the mesosphere, where they attenuate, contributing to increased wind and turbulence.

The negative charge of the Earth and the resulting electric field, the atmosphere, together with the electrically charged ionosphere and magnetosphere, create a global electric circuit. The formation of clouds and thunderstorm electricity plays an important role in this. The danger of lightning discharges has caused the need to develop methods for lightning protection of buildings, structures, power lines and communications. This phenomenon is especially dangerous for aviation. Lightning discharges cause atmospheric radio interference, called atmospherics (see Whistling atmospherics). During a sharp increase in the strength of the electric field, luminous discharges are observed that arise at the points and sharp corners of objects protruding above the earth's surface, on individual peaks in the mountains, etc. (Elma lights). The atmosphere always contains the amount of light and heavy ions that vary greatly depending on specific conditions, which determine the electrical conductivity of the atmosphere. The main air ionizers near the earth's surface are the radiation of radioactive substances contained in the earth's crust and in the atmosphere, as well as cosmic rays. See also Atmospheric electricity.

Human influence on the atmosphere. Over the past centuries, there has been an increase in the concentration of greenhouse gases in the atmosphere due to human economic activities. The percentage of carbon dioxide increased from 2.8-10 2 two hundred years ago to 3.8-10 2 in 2005, the content of methane - from 0.7-10 1 about 300-400 years ago to 1.8-10 -4 at the beginning of the 21st century; About 20% of the increase in the greenhouse effect over the last century was given by freons, which were practically absent in the atmosphere until the middle of the 20th century. These substances are recognized as stratospheric ozone destructors and their production is prohibited by the 1987 Montreal Protocol. The increase in the concentration of carbon dioxide in the atmosphere is caused by the burning of increasing amounts of coal, oil, gas and other types of carbon fuels, as well as deforestation, as a result of which the absorption of carbon dioxide through photosynthesis decreases. The concentration of methane increases with the growth of oil and gas production (due to its losses), as well as with the expansion of rice crops and an increase in the number of cattle. All this contributes to the warming of the climate.

Methods of active influence on atmospheric processes have been developed to change the weather. They are used to protect agricultural plants from hail by dispersing special reagents in thunderclouds. There are also methods for dispersing fog at airports, protecting plants from frost, acting on clouds to increase precipitation in the right places, or to dissipate clouds at times of mass events.

Study of the atmosphere... Information about physical processes in the atmosphere is obtained primarily from meteorological observations, which are carried out by a global network of permanent meteorological stations and posts located on all continents and on many islands. Daily observations provide information on air temperature and humidity, atmospheric pressure and precipitation, cloudiness, wind, etc. Observations of solar radiation and its transformations are carried out at actinometric stations. Of great importance for the study of the atmosphere are the networks of aerological stations, at which meteorological measurements are carried out with the help of radiosondes up to an altitude of 30-35 km. A number of stations are monitoring atmospheric ozone, electrical phenomena in the atmosphere, and the chemical composition of the air.

The data of the ground stations are supplemented by observations on the oceans, where “weather ships” operate permanently in certain areas of the oceans, as well as meteorological information received from research and other vessels.

An increasing amount of information about the atmosphere in recent decades has been obtained with the help of meteorological satellites, which are equipped with instruments for photographing clouds and measuring fluxes of ultraviolet, infrared and microwave radiation from the Sun. Satellites make it possible to obtain information about the vertical profiles of temperature, cloudiness and its water content, elements of the radiation balance of the atmosphere, the temperature of the ocean surface, etc. ... With the help of satellites, it became possible to clarify the value of the solar constant and planetary albedo of the Earth, build maps of the radiation balance of the Earth-atmosphere system, measure the content and variability of trace atmospheric impurities, and solve many other problems of atmospheric physics and environmental monitoring.

Lit .: Budyko MI Climate in the past and the future. L., 1980; Matveev L.T. Course of General Meteorology. Physics of the atmosphere. 2nd ed. L., 1984; Budyko M.I., Ronov A. B., Yanshin A. L. History of the atmosphere. L., 1985; Khrgian A. Kh. Atmospheric Physics. M., 1986; Atmosphere: Handbook. L., 1991; Khromov S.P., Petrosyants M.A. Meteorology and climatology. 5th ed. M., 2001.

G. S. Golitsyn, N. A. Zaitseva.

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.

Tropopause

The transitional layer from the troposphere to the stratosphere, the layer of the atmosphere in which the temperature decrease with height stops.

Stratosphere

The layer of the atmosphere located at an altitude of 11 to 50 km. A slight change in temperature in the layer of 11-25 km (the lower layer of the stratosphere) and its increase in the layer 25-40 km from -56.5 to 0.8 ° (the upper layer of the stratosphere or the inversion region) are characteristic. 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.

Stratopause

The boundary layer of the atmosphere between the stratosphere and the mesosphere. The vertical temperature distribution has a maximum (about 0 ° C).

Mesosphere

Atmosphere of earth

Boundary of the earth's atmosphere

Thermosphere

The upper limit is about 800 km. The temperature rises to altitudes of 200-300 km, where it reaches values ​​of the order of 1500 K, after which it remains almost constant up to high altitudes. Under the influence of ultraviolet and X-ray solar radiation and cosmic radiation, air ionization ("polar lights") occurs - the main areas of the ionosphere lie inside the thermosphere. At altitudes over 300 km, atomic oxygen predominates. The upper limit of the thermosphere is largely determined by the current activity of the Sun. During periods of low activity - for example, in 2008-2009 - there is a noticeable decrease in the size of this layer.

Thermopause

The region of the atmosphere adjacent to the top of the thermosphere. In this area, the absorption of solar radiation is negligible and the temperature does not actually change with altitude.

Exosphere (Orb of Dispersion)

Up to an altitude of 100 km, the atmosphere is a homogeneous, well-mixed mixture of gases. In higher layers, the distribution of gases along the height depends on their molecular masses, the concentration of heavier gases decreases faster with distance from the Earth's surface. Due to the decrease in the density of gases, 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 ~ 150 ° C. Above 200 km, significant fluctuations in the temperature and density of gases are observed in time and space.

At an altitude of about 2000-3500 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 is only a fraction of the interplanetary matter. Another part is made up of dust-like particles of cometary and meteoric origin. In addition to extremely rarefied dust-like particles, electromagnetic and corpuscular radiation of solar and galactic origin penetrates into this space.

The troposphere accounts for about 80% of the mass of the atmosphere, the stratosphere - about 20%; the mass of the mesosphere is no more than 0.3%, the thermosphere is less than 0.05% of the total mass of the atmosphere. On the basis of electrical properties in the atmosphere, the neutrosphere and ionosphere are distinguished. At present, it is believed that the atmosphere extends to an altitude of 2000-3000 km.

Depending on the composition of the gas in the atmosphere, homosphere and heterosphere. Heterosphere- this is the area where gravity affects the separation of gases, since their mixing at this height is negligible. Hence the variable composition of the heterosphere. Below it lies a well-mixed, homogeneous part of the atmosphere, called the homosphere. The boundary between these layers is called the turbopause; it lies at an altitude of about 120 km.

Physiological and other properties of the atmosphere

Already at an altitude of 5 km above sea level, an untrained person develops oxygen starvation and without adaptation, the person's working capacity is significantly reduced. This is where the physiological zone of the atmosphere ends. Human breathing becomes impossible at an altitude of 9 km, although the atmosphere contains oxygen up to about 115 km.

The atmosphere supplies us with the oxygen we need to breathe. However, due to the drop in the total pressure of the atmosphere as it rises to altitude, the partial pressure of oxygen also decreases accordingly.

In rarefied layers of air, the propagation of sound is impossible. Up to heights of 60-90 km, it is still possible to use the resistance and lift of the air for controlled aerodynamic flight. But starting from heights of 100-130 km, the concepts of the number M and the sound barrier, familiar to every pilot, lose their meaning: the conditional Karman line passes there, beyond which the area of ​​purely ballistic flight begins, which can be controlled only using reactive forces.

At altitudes above 100 km, the atmosphere also lacks another remarkable property - the ability to absorb, conduct and transfer thermal energy by convection (i.e., by mixing air). This means that various elements of equipment, equipment of the orbiting space station will not be able to cool from the outside as it is usually done on an airplane - with the help of air jets and air radiators. At this altitude, as in space in general, the only way to transfer heat is through thermal radiation.

The history of the formation of the atmosphere

According to the most common theory, the Earth's atmosphere over time was in three different compositions. It originally consisted of light gases (hydrogen and helium) captured from interplanetary space. This is the so-called primary atmosphere(about four billion years ago). At the next stage, active volcanic activity led to the saturation of the atmosphere with gases other than hydrogen (carbon dioxide, ammonia, water vapor). So it was formed secondary atmosphere(about three billion years ago). The atmosphere was restorative. Further, the process of formation of the atmosphere was determined by the following factors:

• leakage of light gases (hydrogen and helium) into interplanetary space;
• chemical reactions 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 hydrogen content and a much higher nitrogen and carbon dioxide content (formed as a result of chemical reactions from ammonia and hydrocarbons).

Nitrogen

The formation of a large amount of nitrogen N 2 is due to the oxidation of the ammonia-hydrogen atmosphere with molecular oxygen O 2, which began to flow from the planet's surface as a result of photosynthesis, starting from 3 billion years ago. Also, nitrogen N 2 is released into the atmosphere as a result of denitrification of nitrates and other nitrogen-containing compounds. Nitrogen is oxidized by ozone to NO in the upper atmosphere.

Nitrogen N 2 reacts only under specific conditions (for example, during a lightning strike). Oxidation of molecular nitrogen by ozone with electrical discharges in small quantities is used in the industrial production of nitrogen fertilizers. It can be oxidized with low energy consumption and converted into a biologically active form by cyanobacteria (blue-green algae) and nodule bacteria that form rhizobial symbiosis with legumes, the so-called. siderates.

Oxygen

The composition of the atmosphere began to change radically 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. Initially, oxygen was spent on the oxidation of reduced compounds - ammonia, hydrocarbons, the ferrous form of iron contained in the oceans, etc. At the end of this stage, the oxygen content in the atmosphere began to grow. Gradually, a modern atmosphere with oxidizing properties was formed. Since this caused serious and abrupt changes in many processes occurring in the atmosphere, lithosphere and biosphere, this event was called the Oxygen Catastrophe.

Noble gases

Air pollution

Recently, humans have begun to influence the evolution of the atmosphere. The result of his activities was a constant significant increase in the content of carbon dioxide in the atmosphere due to the combustion of hydrocarbon fuels accumulated in previous geological eras. Enormous amounts of CO 2 are consumed during photosynthesis and absorbed by the world's oceans. This gas enters the atmosphere due to the decomposition of carbonate rocks and organic matter of plant and animal origin, as well as due to volcanism and human production activities. Over the past 100 years, the content of CO 2 in the atmosphere has increased by 10%, with the bulk (360 billion tons) coming from fuel combustion. If the growth rate of fuel combustion continues, then in the next 200-300 years the amount of СО 2 in the atmosphere will double and may lead to global climate changes.

Fuel combustion is the main source of polluting gases (CO, SO 2). Sulfur dioxide is oxidized by atmospheric oxygen to SO 3 in the upper atmosphere, which in turn interacts with water and ammonia vapors, and the resulting sulfuric acid (H 2 SO 4) and ammonium sulfate ((NH 4) 2 SO 4) return to the surface of the Earth in the form of the so-called. acid rain. The use of internal combustion engines leads to significant pollution of the atmosphere with nitrogen oxides, hydrocarbons and lead compounds (tetraethyl lead Pb (CH 3 CH 2) 4)).

Aerosol pollution of the atmosphere is caused both by natural causes (volcanic eruptions, dust storms, carry-over of sea water droplets and pollen of plants, etc.), and by human economic activities (mining of ores and building materials, burning fuel, making cement, etc.). Intensive large-scale removal of particulate matter into the atmosphere is one of the possible causes of climate change on the planet.

see also

• Jacchia (atmosphere model)

Notes (edit)

Links

Literature

1. V. V. Parin, F. P. Kosmolinsky, B. A. Dushkov"Space biology and medicine" (2nd edition, revised and enlarged), M .: "Education", 1975, 223 pages.
2. N.V. Gusakova"Chemistry of the Environment", Rostov-on-Don: Phoenix, 2004, 192 with ISBN 5-222-05386-5
3. Sokolov V.A. Geochemistry of natural gases, M., 1971;
4. McEwen M., Phillips L. Chemistry of the atmosphere, M., 1978;
5. Work K., Warner S. Air pollution. Sources and Control, trans. from English., M .. 1980;
6. Monitoring of background pollution of natural environments. v. 1, L., 1982.

Every literate person should know not only that the planet is surrounded by an atmosphere of a mixture of all kinds of gases, but also that there are different layers of the atmosphere, which are located at different distances from the Earth's surface.

Observing in the sky, we absolutely do not see either its complex structure, or its heterogeneous composition, or other things hidden from our eyes. But it is precisely due to the complex and multicomponent composition of the air layer around the planet on it that conditions exist that have allowed life to arise here, vegetation to flourish, and everything that has ever appeared here.

Knowledge about the subject of the conversation is already given to people by the 6th grade at school, but some have not yet finished their studies, and some have been there so long ago that they have already forgotten everything. Nevertheless, every educated person should know what the world around him consists of, especially that part of it, on which the very possibility of his normal life directly depends.

What is the name of each of the layers of the atmosphere, at what height is it located, what role does it play? All these issues will be discussed below.

The structure of the Earth's atmosphere

Looking at the sky, especially when it is completely cloudless, it is very difficult to even assume that it has such a complex and multi-layered structure that the temperature there at different heights is very different, and that it is there, in altitude, that the most important processes for all flora and fauna take place. on the ground.

If it were not for such a complex composition of the gas cover of the planet, then there simply would not be any life and even the possibility for its origin.

The first attempts to study this part of the surrounding world were undertaken by the ancient Greeks, but they could not go too far in their conclusions, since they did not have the necessary technical base. They did not see the boundaries of different layers, could not measure their temperature, study the component composition, etc.

Basically, only weather phenomena pushed the most progressive minds into thinking that the visible sky is not as simple as it seems.

It is believed that the structure of the modern gas shell around the Earth was formed in three stages. First there was a primordial atmosphere of hydrogen and helium captured from outer space.

Then volcanic eruptions filled the air with a mass of other particles, and a secondary atmosphere arose. After going through all the basic chemical reactions and particle relaxation processes, the current situation arose.

Layers of the atmosphere in order from the surface of the earth and their characteristics

The structure of the planet's gas envelope is rather complex and diverse. Let's consider it in more detail, gradually reaching the highest levels.

Troposphere

Apart from the boundary layer, the troposphere is the lowest layer of the atmosphere. It extends to a height of approximately 8-10 km above the earth's surface in the polar regions, 10-12 km in temperate climates, and in tropical parts - 16-18 kilometers.

Interesting fact: this distance can vary depending on the season - in winter it is slightly less than in summer.

The air of the troposphere contains the main life-giving force for all life on earth. It contains about 80% of all available atmospheric air, more than 90% of water vapor, it is here that clouds, cyclones and other atmospheric phenomena are formed.

It is interesting to note the gradual decrease in temperature as it rises from the surface of the planet. Scientists have calculated that for every 100 m of altitude, the temperature decreases by about 0.6-0.7 degrees.

Stratosphere

The next most important layer is the stratosphere. The height of the stratosphere is approximately 45-50 kilometers. It starts from 11 km and negative temperatures already prevail here, reaching as much as -57 ° С.

Why is this layer important for humans, all animals and plants? It is here, at an altitude of 20-25 kilometers, that the ozone layer is located - it traps ultraviolet rays emanating from the sun and reduces their destructive effect on flora and fauna to an acceptable value.

It is very interesting to note that the stratosphere absorbs many types of radiation that come to earth from the sun, other stars, and outer space. The energy received from these particles is used to ionize the molecules and atoms located here, various chemical compounds appear.

All this leads to such a famous and colorful phenomenon as the northern lights.

Mesosphere

The mesosphere starts at about 50 and extends up to 90 kilometers. The gradient, or temperature drop with a change in altitude, is no longer as large here as in the lower layers. In the upper boundaries of this shell, the temperature is about -80 ° C. The composition of this area includes approximately 80% nitrogen as well as 20% oxygen.

It is important to note that the mesosphere is a kind of dead zone for any flying device. Airplanes cannot fly here, since the air is excessively rarefied, while satellites do not fly at such a low altitude, since the available air density for them is very high.

Another interesting characteristic of the mesosphere is it is here that the meteorites hitting the planet burn. The study of such layers remote from the earth is carried out using special rockets, but the efficiency of the process is low, therefore, the study of the region leaves much to be desired.

Thermosphere

Immediately after the considered layer goes thermosphere, the height in km of which extends as much as 800 km. In a way, this is almost open space. Aggressive effects of cosmic radiation, radiation, solar radiation are observed here.

All this gives rise to such a wonderful and beautiful phenomenon as the polar lights.

The lowest layer of the thermosphere is heated to a temperature of about 200 K and more. This happens due to elementary processes between atoms and molecules, their recombination and radiation.

The upper layers are heated due to magnetic storms flowing here, electric currents, which are generated in this case. The bed temperature is uneven and can fluctuate very significantly.

Most artificial satellites, ballistic bodies, manned stations, etc. fly in the thermosphere. It also tests launches of various weapons and missiles.

Exosphere

The exosphere, or as it is also called the sphere of dispersion, is the highest level of our atmosphere, its limit, followed by interplanetary space. The exosphere begins from an altitude of about 800-1000 kilometers.

Dense layers are left behind and here the air is extremely rarefied, any particles that come from the side are simply carried away into space due to the very weak action of the force of gravity.

This shell ends at an altitude of approximately 3000-3500 km, and there are almost no particles here. This zone is called the near-space vacuum. It is not individual particles in their usual state that predominate here, but plasma, most often completely ionized.

The importance of the atmosphere in the life of the Earth

This is how all the main levels of the structure of the atmosphere of our planet look like. Its detailed scheme may include other regions, but they are already of secondary importance.

It is important to note that the atmosphere plays a decisive role for life on Earth. A lot of ozone in its stratosphere allows flora and fauna to escape the damaging effects of radiation and radiation from space.

It is also here that the weather is formed, all atmospheric phenomena occur, cyclones, winds arise and die, this or that pressure is established. All this has a direct impact on the state of man, all living organisms and plants.

The nearest layer, the troposphere, gives us the ability to breathe, oxygenates all living things and allows them to live. Even small deviations in the structure and composition of the atmosphere can have the most detrimental effect on all living things.

That is why now such a campaign has been launched against harmful emissions from cars and production, environmentalists are sounding the alarm about the thickness of the ozone ball, the Green Party and others like it are advocating for the maximum preservation of nature. This is the only way to prolong normal life on earth and not make it climatically unbearable.

Atmosphere(from the Greek atmos - steam and spharia - a ball) - the air shell of the Earth, rotating with it. The development of the atmosphere was closely associated with the geological and geochemical processes taking place on our planet, as well as with the activities of living organisms.

The lower boundary of the atmosphere coincides with the surface of the Earth, since air penetrates into the smallest pores in the soil and is dissolved even in water.

The upper boundary at an altitude of 2000-3000 km gradually passes into outer space.

Thanks to the atmosphere, which contains oxygen, life on Earth is possible. Atmospheric oxygen is used in the process of respiration by humans, animals, and plants.

If there was no atmosphere, the earth would be as quiet as the moon. After all, sound is the vibration of air particles. The blue color of the sky is explained by the fact that the sun's rays, passing through the atmosphere, as through a lens, decompose into their constituent colors. At the same time, the rays of blue and blue colors are scattered most of all.

The atmosphere traps most of the sun's ultraviolet radiation, which has a detrimental effect on living organisms. It also keeps heat at the surface of the Earth, preventing our planet from cooling.

The structure of the atmosphere

Several layers can be distinguished in the atmosphere, differing in density and density (Fig. 1).

Troposphere

Troposphere- the lowest layer of the atmosphere, the thickness of which is 8-10 km above the poles, 10-12 km in temperate latitudes, and 16-18 km above the equator.

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

The air in the troposphere is heated from the earth's surface, that is, from land and water. Therefore, the air temperature in this layer decreases with height by an average of 0.6 ° C for every 100 m. At the upper border of the troposphere, it reaches -55 ° C. At the same time, in the equatorial region at the upper border of the troposphere, the air temperature is -70 ° С, and in the North Pole area -65 ° С.

In the troposphere, about 80% of the mass of the atmosphere is concentrated, almost all water vapor is located, thunderstorms, storms, clouds and precipitation occur, and vertical (convection) and horizontal (wind) air movement also occurs.

We can say that the weather is mainly formed in the troposphere.

Stratosphere

Stratosphere- the layer of the atmosphere located above the troposphere at an altitude of 8 to 50 km. The color of the sky in this layer appears purple, which is due to the rarefaction of the air, due to which the sun's rays are almost not scattered.

The stratosphere contains 20% of the mass of the atmosphere. The air in this layer is rarefied, there is practically no water vapor, and therefore almost no clouds and precipitation are formed. However, stable air currents are observed in the stratosphere, the speed of which reaches 300 km / h.

This layer is concentrated ozone(ozone screen, ozonosphere), a layer that absorbs ultraviolet rays, preventing them from reaching the Earth and thereby protecting living organisms on our planet. Thanks to ozone, the air temperature at the upper boundary of the stratosphere is in the range from -50 to 4-55 ° C.

Between the mesosphere and the stratosphere, there is a transition zone - the stratopause.

Mesosphere

Mesosphere- the layer of the atmosphere located at an altitude of 50-80 km. The density of air here is 200 times less than at the surface of the Earth. The color of the sky in the mesosphere appears to be black, and stars are visible during the day. The air temperature drops to -75 (-90) ° С.

At an altitude of 80 km begins thermosphere. The air temperature in this layer rises sharply to a height of 250 m, and then becomes constant: at an altitude of 150 km, it reaches 220-240 ° C; at an altitude of 500-600 km, it exceeds 1500 ° C.

In the mesosphere and thermosphere, under the action of cosmic rays, gas molecules decay into charged (ionized) particles of atoms, therefore this part of the atmosphere was called ionosphere- a layer of very rarefied air located at an altitude of 50 to 1000 km, consisting mainly of ionized oxygen atoms, nitrogen oxide molecules and free electrons. This layer is characterized by a high electrification, and long and medium radio waves are reflected from it, as from a mirror.

In the ionosphere, auroras arise - the glow of rarefied gases under the influence of electrically charged particles flying from the Sun - and sharp fluctuations of the magnetic field are observed.

Exosphere

Exosphere- the outer layer of the atmosphere, located above 1000 km. This layer is also called the scattering sphere, since gas particles move here with high speed and can be scattered into outer space.

Atmosphere composition

The atmosphere is a mixture of gases, consisting of nitrogen (78.08%), oxygen (20.95%), carbon dioxide (0.03%), argon (0.93%), a small amount of helium, neon, xenon, krypton (0.01%), ozone and other gases, but their content is negligible (Table 1). The modern composition of the Earth's air was established more than a hundred million years ago, but the dramatically increased production activity of man still led to its change. Currently, there is an increase in the content of CO 2 by about 10-12%.

The gases in the atmosphere have different functional roles. However, the main significance of these gases is determined primarily by the fact that they very strongly absorb radiant energy and thus have a significant effect on the temperature regime of the Earth's surface and atmosphere.

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

Nitrogen, the most widespread gas in the atmosphere, it is not chemically active.

Oxygen, unlike nitrogen, it is a very active chemical element. The specific function of oxygen is the oxidation of organic matter of heterotrophic organisms, rocks and under-oxidized gases emitted into the atmosphere by volcanoes. Without oxygen, there would be no decomposition of dead organic matter.

The role of carbon dioxide in the atmosphere is exceptionally great. It enters the atmosphere as a result of combustion processes, respiration of living organisms, decay and is, first of all, the main building material for the creation of organic matter during photosynthesis. In addition, the property of carbon dioxide is of great importance to transmit short-wave solar radiation and absorb part of the thermal long-wave radiation, which will create the so-called greenhouse effect, which will be discussed below.

The influence on atmospheric processes, especially on the thermal regime of the stratosphere, is also exerted by ozone. This gas serves as a natural absorber of ultraviolet radiation from the sun, and absorption of solar radiation leads to heating of the air. The average monthly values ​​of the total ozone content in the atmosphere vary depending on the latitude of the area and the time of year in the range of 0.23-0.52 cm (this is the thickness of the ozone layer at ground pressure and temperature). An increase in ozone content from the equator to the poles and an annual variation with a minimum in autumn and maximum in spring are observed.

A characteristic property of the atmosphere is that the content of the main gases (nitrogen, oxygen, argon) changes insignificantly with altitude: at an altitude of 65 km in the atmosphere, the content of nitrogen is 86%, oxygen is 19, argon is 0.91, and at an altitude of 95 km - nitrogen 77, oxygen - 21.3, argon - 0.82%. The constancy of the composition of atmospheric air vertically and horizontally is maintained by mixing it.

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

Particles are especially abundant in the air of cities and large industrial centers, where emissions of harmful gases and their impurities formed during fuel combustion are added to aerosols.

The concentration of aerosols in the atmosphere determines the transparency of the air, which affects the solar radiation reaching the Earth's surface. The largest aerosols are condensation nuclei (from lat. condensatio- compaction, thickening) - contribute to the transformation of water vapor into water droplets.

The value of water vapor is determined primarily by the fact that it delays the long-wave thermal radiation of the earth's surface; represents the main link of large and small moisture cycles; increases the air temperature during condensation of water beds.

The amount of water vapor in the atmosphere changes over time and space. Thus, the concentration of water vapor at the earth's surface ranges from 3% in the tropics to 2-10 (15)% in Antarctica.

The average content of water vapor in the vertical column of the atmosphere in temperate latitudes is about 1.6-1.7 cm (such a thickness will have a layer of condensed water vapor). Information on water vapor in different layers of the atmosphere is contradictory. It was assumed, for example, that in the altitude range from 20 to 30 km, the specific humidity increases strongly with height. However, subsequent measurements indicate a greater dryness of the stratosphere. Apparently, the specific humidity in the stratosphere depends little on the height and amounts to 2-4 mg / kg.

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

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

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

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

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

The air can be saturated and not saturated water vapor. So, if at a temperature of +30 ° C 1 m 3 of air contains 15 g of water vapor, the air is not saturated with water vapor; if 30 g is saturated.

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

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

The greater the relative humidity of the air, i.e. the closer the air is to saturation, the more likely precipitation is.

Always high (up to 90%) relative air humidity is observed in the equatorial zone, since there is a high air temperature throughout the year and there is a lot of evaporation from the surface of the oceans. The same high relative humidity and in the polar regions, but only because at low temperatures, even a small amount of water vapor makes the air saturated or close to saturation. In temperate latitudes, the relative humidity changes with the seasons - in winter it is higher, in summer it is lower.

Especially low relative humidity of air in deserts: 1 m 1 of air there contains two to three times less than the amount of water vapor possible at a given temperature.

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

When cooled, saturated air cannot retain the same amount of water vapor; it thickens (condenses), turning into fog droplets. Fog can be observed in the summer on a clear cool night.

Clouds- this is the same fog, only it is formed not near the earth's surface, but at a certain height. Rising up, the air is cooled, and the water vapor in it condenses. The resulting tiny droplets of water make up the clouds.

In the formation of clouds are involved and solid particles suspended in the troposphere.

Clouds can have different shapes, which depend 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.

Protection of the atmosphere

The main source is industrial plants and automobiles. In big cities, the problem of gas pollution on the main transport routes is very acute. That is why in many large cities of the world, including in our country, environmental control of the toxicity of vehicle exhaust gases has been introduced. According to experts, smoke and dustiness of the air can halve the supply of solar energy to the earth's surface, which will lead to a change in natural conditions.

Its upper boundary is at an altitude of 8-10 km in polar, 10-12 km in temperate and 16-18 km in tropical latitudes; in winter it is lower than in summer. The lower, main layer of the atmosphere. Contains more than 80% of the total mass of atmospheric air and about 90% of all water vapor in the atmosphere. Turbulence and convection are highly developed in the troposphere, clouds appear, cyclones and anticyclones develop. Temperature decreases with increasing altitude with an average vertical gradient of 0.65 ° / 100 m

For "normal conditions" at the Earth's surface, the following are taken: density 1.2 kg / m3, barometric pressure 101.35 kPa, temperature plus 20 ° C and relative humidity 50%. These conditional indicators are of purely engineering significance.

Stratosphere

The layer of the atmosphere located at an altitude of 11 to 50 km. A slight change in temperature in the layer of 11-25 km (the lower layer of the stratosphere) and its increase in the layer 25-40 km from -56.5 to 0.8 ° (the upper layer of the stratosphere or the inversion region) are characteristic. 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.

Stratopause

The boundary layer of the atmosphere between the stratosphere and the mesosphere. The vertical temperature distribution has a maximum (about 0 ° C).

Mesosphere

Mesopause

Transitional layer between the mesosphere and thermosphere. The vertical temperature distribution has a minimum (about -90 ° C).

Pocket Line

Height above sea level, which is conventionally taken as the boundary between the Earth's atmosphere and space.

Thermosphere

The upper limit is about 800 km. The temperature rises to altitudes of 200-300 km, where it reaches values ​​of the order of 1500 K, after which it remains almost constant up to high altitudes. Under the influence of ultraviolet and X-ray solar radiation and cosmic radiation, air ionization ("polar lights") occurs - the main areas of the ionosphere lie inside the thermosphere. At altitudes over 300 km, atomic oxygen predominates.

Exosphere (Orb of Dispersion)

Up to an altitude of 100 km, the atmosphere is a homogeneous, well-mixed mixture of gases. In higher layers, the distribution of gases along the height depends on their molecular masses, the concentration of heavier gases decreases faster with distance from the Earth's surface. Due to the decrease in the density of gases, 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 the temperature and density of gases are observed in time and space.

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 is only a fraction of the interplanetary matter. Another part is made up of dust-like particles of cometary and meteoric origin. In addition to extremely rarefied dust-like particles, electromagnetic and corpuscular radiation of solar and galactic origin penetrates into this space.

The troposphere accounts for about 80% of the mass of the atmosphere, the stratosphere - about 20%; the mass of the mesosphere is no more than 0.3%, the thermosphere is less than 0.05% of the total mass of the atmosphere. On the basis of electrical properties in the atmosphere, the neutrosphere and ionosphere are distinguished. At present, it is believed that the atmosphere extends to an altitude of 2000-3000 km.

Depending on the composition of the gas in the atmosphere, homosphere and heterosphere. Heterosphere- this is the area where gravity affects the separation of gases, since their mixing at this height is negligible. Hence the variable composition of the heterosphere. Below it lies a well-mixed, homogeneous part of the atmosphere, called the homosphere. The boundary between these layers is called the turbopause; it lies at an altitude of about 120 km.

Physical properties

The thickness of the atmosphere is approximately 2000 - 3000 km from the Earth's surface. The total mass of air is (5.1-5.3) × 10 18 kg. The molar mass of clean dry air is 28.966. Pressure at 0 ° C at sea level 101.325 kPa; critical temperature - 140.7 ° C; critical pressure 3.7 MPa; C p 1.0048 × 10 J / (kg K) (at 0 ° C), C v 0.7159 10? J / (kg K) (at 0 ° C). Solubility of air in water at 0 ° С - 0.036%, at 25 ° С - 0.22%.

Physiological and other properties of the atmosphere

Already at an altitude of 5 km above sea level, an untrained person develops oxygen starvation and without adaptation, the person's working capacity is significantly reduced. This is where the physiological zone of the atmosphere ends. Human breathing becomes impossible at an altitude of 15 km, although the atmosphere contains oxygen up to about 115 km.

The atmosphere supplies us with the oxygen we need to breathe. However, due to the drop in the total pressure of the atmosphere as it rises to altitude, the partial pressure of oxygen also decreases accordingly.

The human lungs constantly contain about 3 liters of alveolar air. The partial pressure of oxygen in the alveolar air at normal atmospheric pressure is 110 mm Hg. Art., the pressure of carbon dioxide is 40 mm Hg. Art., and water vapor - 47 mm Hg. Art. With increasing altitude, the oxygen pressure drops, and the total pressure of water vapor and carbon dioxide in the lungs remains almost constant - about 87 mm Hg. Art. The supply of oxygen to the lungs will stop completely when the pressure of the surrounding air 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 height, water and interstitial fluid begin to boil in the human body. Outside the pressurized cabin at these heights, 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 - 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 - exerts an intense effect on the body; at altitudes of more than 40 km, the ultraviolet part of the solar spectrum, which is dangerous for humans, operates.

As it rises to an ever greater height above the Earth's surface, such phenomena familiar to us, observed in the lower layers of the atmosphere, such as the propagation of sound, the emergence of aerodynamic lift and resistance, heat transfer by convection, gradually weaken, and then completely disappear.

In rarefied layers of air, the propagation of sound is impossible. Up to heights of 60-90 km, it is still possible to use the resistance and lift of the air for controlled aerodynamic flight. But starting from altitudes of 100-130 km, the concepts of the number M and the sound barrier, familiar to every pilot, lose their meaning, the conditional Karman Line passes there, behind which the sphere of purely ballistic flight begins, which can be controlled only using reactive forces.

At altitudes above 100 km, the atmosphere also lacks another remarkable property - the ability to absorb, conduct and transfer thermal energy by convection (i.e., by mixing air). This means that various elements of equipment, equipment of the orbiting space station will not be able to cool from the outside as it is usually done on an airplane - with the help of air jets and air radiators. At this altitude, as in space in general, the only way to transfer heat is through thermal radiation.

Atmosphere composition

The Earth's atmosphere consists mainly of gases and various impurities (dust, water droplets, ice crystals, sea salts, combustion products).

The concentration of gases that make up the atmosphere is practically constant, with the exception of water (H 2 O) and carbon dioxide (CO 2).

In addition to the gases indicated in the table, the atmosphere contains SO 2, NH 3, CO, ozone, hydrocarbons, HCl, vapors, I 2, as well as many other gases in small quantities. A large number of suspended solid and liquid particles (aerosol) are constantly found in the troposphere.

The history of the formation of the atmosphere

According to the most common theory, the Earth's atmosphere over time was in four different compositions. It originally consisted of light gases (hydrogen and helium) captured from interplanetary space. This is the so-called primary atmosphere(about four billion years ago). At the next stage, active volcanic activity led to the saturation of the atmosphere with gases other than hydrogen (carbon dioxide, ammonia, water vapor). So it was formed secondary atmosphere(about three billion years ago). The atmosphere was restorative. Further, the process of formation of the atmosphere was determined by the following factors:

• leakage of light gases (hydrogen and helium) into interplanetary space;
• chemical reactions 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 hydrogen content and a much higher nitrogen and carbon dioxide content (formed as a result of chemical reactions from ammonia and hydrocarbons).

Nitrogen

The formation of a large amount of N 2 is due to the oxidation of the ammonia-hydrogen atmosphere with molecular O 2, which began to flow from the planet's surface as a result of photosynthesis, starting from 3 billion years ago. Also, N 2 is released into the atmosphere as a result of denitrification of nitrates and other nitrogen-containing compounds. Nitrogen is oxidized by ozone to NO in the upper atmosphere.

Nitrogen N 2 reacts only under specific conditions (for example, during a lightning strike). Oxidation of molecular nitrogen with ozone during electrical discharges is used in the industrial production of nitrogen fertilizers. It can be oxidized with low energy consumption and converted into a biologically active form by cyanobacteria (blue-green algae) and nodule bacteria that form rhizobial symbiosis with legumes, the so-called. siderates.

Oxygen

The composition of the atmosphere began to change radically 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. Initially, oxygen was spent on the oxidation of reduced compounds - ammonia, hydrocarbons, the ferrous form of iron contained in the oceans, etc. At the end of this stage, the oxygen content in the atmosphere began to grow. Gradually, a modern atmosphere with oxidizing properties was formed. Since this caused serious and abrupt changes in many processes occurring in the atmosphere, lithosphere and biosphere, this event was called the Oxygen Catastrophe.

Carbon dioxide

The content of CO 2 in the atmosphere depends on volcanic activity and chemical processes in the earth's shells, but most of all on the intensity of biosynthesis and decomposition of organic matter in the biosphere of the Earth. Almost all of the planet's current biomass (about 2.4 × 10 12 tons) is formed by carbon dioxide, nitrogen and water vapor contained in the atmospheric air. Buried in the ocean, swamps and forests, organic matter is converted into coal, oil and natural gas. (see Geochemical cycle of carbon)

Noble gases

Air pollution

Recently, humans have begun to influence the evolution of the atmosphere. The result of his activities was a constant significant increase in the content of carbon dioxide in the atmosphere due to the combustion of hydrocarbon fuels accumulated in previous geological eras. Enormous amounts of CO 2 are consumed during photosynthesis and absorbed by the world's oceans. This gas enters the atmosphere due to the decomposition of carbonate rocks and organic matter of plant and animal origin, as well as due to volcanism and human production activities. Over the past 100 years, the content of CO 2 in the atmosphere has increased by 10%, with the bulk (360 billion tons) coming from fuel combustion. If the growth rate of fuel combustion continues, then in the next 50-60 years the amount of СО 2 in the atmosphere will double and may lead to global climate changes.

Fuel combustion is the main source of polluting gases (CO, SO 2). Sulfur dioxide is oxidized by atmospheric oxygen to SO 3 in the upper atmosphere, which in turn interacts with water and ammonia vapors, and the resulting sulfuric acid (H 2 SO 4) and ammonium sulfate ((NH 4) 2 SO 4) return to the surface of the Earth in the form of the so-called. acid rain. The use of internal combustion engines leads to significant pollution of the atmosphere with nitrogen oxides, hydrocarbons and lead compounds (tetraethyl lead Pb (CH 3 CH 2) 4)).

Aerosol pollution of the atmosphere is caused both by natural causes (volcanic eruptions, dust storms, carry-over of sea water droplets and pollen of plants, etc.), and by human economic activities (mining of ores and building materials, burning fuel, making cement, etc.). Intensive large-scale removal of particulate matter into the atmosphere is one of the possible causes of climate change on the planet.

Literature

1. V. V. Parin, F. P. Kosmolinsky, B. A. Dushkov "Space biology and medicine" (2nd edition, revised and enlarged), Moscow: "Education", 1975, 223 pages.
2. N. V. Gusakova "Chemistry of the Environment", Rostov-on-Don: Phoenix, 2004, 192 with ISBN 5-222-05386-5
3. Sokolov V. A .. Geochemistry of natural gases, M., 1971;
4. McEwen M., Phillips L. .. Chemistry of the atmosphere, M., 1978;
5. Work K., Warner S., Air pollution. Sources and Control, trans. from English., M .. 1980;
6. Monitoring of background pollution of natural environments. v. 1, L., 1982.

see also

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