ATMOSPHERE OF THE EARTH(Greek atmos steam + sphaira ball) - gaseous shell surrounding the Earth. The mass of the atmosphere is about 5.15·10 15 The biological significance of the atmosphere is enormous. In the atmosphere, there is a mass-energy exchange between animate and inanimate nature, between flora and fauna. Atmospheric nitrogen is assimilated by microorganisms; plants synthesize organic substances from carbon dioxide and water due to the energy of the sun and release oxygen. The presence of the atmosphere ensures the preservation of water on Earth, which is also an important condition for the existence of living organisms.

Studies carried out with the help of high-altitude geophysical rockets, artificial earth satellites and interplanetary automatic stations have established that the earth's atmosphere extends for thousands of kilometers. The boundaries of the atmosphere are unstable, they are influenced by the gravitational field of the moon and the pressure of the flow of sunlight. Above the equator in the region of the earth's shadow, the atmosphere reaches heights of about 10,000 km, and above the poles, its boundaries are 3,000 km from the earth's surface. The bulk of the atmosphere (80-90%) is within altitudes up to 12-16 km, which is explained by the exponential (non-linear) nature of the decrease in the density (rarefaction) of its gaseous medium as the height above sea level increases.

The existence of most living organisms in natural conditions is possible in even narrower boundaries of the atmosphere, up to 7-8 km, where a combination of such atmospheric factors as gas composition, temperature, pressure, and humidity, necessary for the active course of biological processes, takes place. The movement and ionization of air, atmospheric precipitation, and the electrical state of the atmosphere are also of hygienic importance.

Gas composition

The atmosphere is a physical mixture of gases (Table 1), mainly nitrogen and oxygen (78.08 and 20.95 vol. %). The ratio of atmospheric gases is almost the same up to altitudes of 80-100 km. The constancy of the main part of the gas composition of the atmosphere is due to the relative balancing of the processes of gas exchange between animate and inanimate nature and the continuous mixing of air masses in the horizontal and vertical directions.

Table 1. CHARACTERISTICS OF THE CHEMICAL COMPOSITION OF DRY ATMOSPHERIC AIR NEAR THE EARTH'S SURFACE

Gas composition	Volume concentration, %
Oxygen
Carbon dioxide
Nitrous oxide
Sulfur dioxide	0 to 0.0001
	0 to 0.000007 in summer, 0 to 0.000002 in winter
nitrogen dioxide	0 to 0.000002
Carbon monoxide

At altitudes above 100 km, the percentage of individual gases changes due to their diffuse stratification under the influence of gravity and temperature. In addition, under the action of the short-wavelength part of ultraviolet and X-rays at an altitude of 100 km or more, oxygen, nitrogen and carbon dioxide molecules dissociate into atoms. At high altitudes, these gases are in the form of highly ionized atoms.

The content of carbon dioxide in the atmosphere of different regions of the Earth is less constant, which is partly due to the uneven distribution of large industrial enterprises that pollute the air, as well as the uneven distribution of vegetation and water basins that absorb carbon dioxide on the Earth. Also variable in the atmosphere is the content of aerosols (see) - particles suspended in the air ranging in size from several millimicrons to several tens of microns - formed as a result of volcanic eruptions, powerful artificial explosions, pollution by industrial enterprises. The concentration of aerosols decreases rapidly with altitude.

The most unstable and important of the variable components of the atmosphere is water vapor, the concentration of which at the earth's surface can vary from 3% (in the tropics) to 2 × 10 -10% (in Antarctica). The higher the air temperature, the more moisture, ceteris paribus, can be in the atmosphere and vice versa. The bulk of water vapor is concentrated in the atmosphere up to altitudes of 8-10 km. The content of water vapor in the atmosphere depends on the combined influence of the processes of evaporation, condensation and horizontal transport. At high altitudes, due to a decrease in temperature and condensation of vapors, the air is practically dry.

The Earth's atmosphere, in addition to molecular and atomic oxygen, contains a small amount of ozone (see), the concentration of which is very variable and varies depending on the height and season. Most of the ozone is contained in the region of the poles by the end of the polar night at an altitude of 15-30 km with a sharp decrease up and down. Ozone arises as a result of the photochemical action of ultraviolet solar radiation on oxygen, mainly at altitudes of 20-50 km. In this case, diatomic oxygen molecules partially decompose into atoms and, joining undecomposed molecules, form triatomic ozone molecules (polymeric, allotropic form of oxygen).

The presence in the atmosphere of a group of so-called inert gases (helium, neon, argon, krypton, xenon) is associated with the continuous flow of natural radioactive decay processes.

The biological significance of gases the atmosphere is very large. For most multicellular organisms, a certain content of molecular oxygen in a gaseous or aqueous medium is an indispensable factor in their existence, which during respiration determines the release of energy from organic substances created initially during photosynthesis. It is no coincidence that the upper boundaries of the biosphere (the part of the surface of the globe and the lower part of the atmosphere where life exists) are determined by the presence of a sufficient amount of oxygen. In the process of evolution, organisms have adapted to a certain level of oxygen in the atmosphere; changing the oxygen content in the direction of decreasing or increasing has an adverse effect (see Altitude sickness, Hyperoxia, Hypoxia).

The ozone-allotropic form of oxygen also has a pronounced biological effect. At concentrations not exceeding 0.0001 mg / l, which is typical for resort areas and sea coasts, ozone has a healing effect - it stimulates respiration and cardiovascular activity, improves sleep. With an increase in the concentration of ozone, its toxic effect is manifested: eye irritation, necrotic inflammation of the mucous membranes of the respiratory tract, exacerbation of pulmonary diseases, autonomic neuroses. Entering into combination with hemoglobin, ozone forms methemoglobin, which leads to a violation of the respiratory function of the blood; the transfer of oxygen from the lungs to the tissues becomes difficult, the phenomena of suffocation develop. Atomic oxygen has a similar adverse effect on the body. Ozone plays a significant role in creating the thermal regimes of various layers of the atmosphere due to the extremely strong absorption of solar radiation and terrestrial radiation. Ozone absorbs ultraviolet and infrared rays most intensively. Solar rays with a wavelength of less than 300 nm are almost completely absorbed by atmospheric ozone. Thus, the Earth is surrounded by a kind of "ozone screen" that protects many organisms from the harmful effects of ultraviolet radiation from the sun. Nitrogen in atmospheric air is of great biological importance, primarily as a source of so-called. fixed nitrogen - a resource of plant (and ultimately animal) food. The physiological significance of nitrogen is determined by its participation in creating the level of atmospheric pressure necessary for life processes. Under certain conditions of pressure changes, nitrogen plays a major role in the development of a number of disorders in the body (see Decompression sickness). Assumptions that nitrogen weakens the toxic effect of oxygen on the body and is absorbed from the atmosphere not only by microorganisms, but also by higher animals, are controversial.

The inert gases of the atmosphere (xenon, krypton, argon, neon, helium) at the partial pressure they create under normal conditions can be classified as biologically indifferent gases. With a significant increase in partial pressure, these gases have a narcotic effect.

The presence of carbon dioxide in the atmosphere ensures the accumulation of solar energy in the biosphere due to the photosynthesis of complex carbon compounds, which continuously arise, change and decompose in the course of life. This dynamic system is maintained as a result of the activity of algae and land plants that capture the energy of sunlight and use it to convert carbon dioxide (see) and water into a variety of organic compounds with the release of oxygen. The upward extension of the biosphere is partially limited by the fact that at altitudes of more than 6-7 km, chlorophyll-containing plants cannot live due to the low partial pressure of carbon dioxide. Carbon dioxide is also very active in physiological terms, as it plays an important role in the regulation of metabolic processes, the activity of the central nervous system, respiration, blood circulation, and the oxygen regime of the body. However, this regulation is mediated by the influence of carbon dioxide produced by the body itself, and not from the atmosphere. In the tissues and blood of animals and humans, the partial pressure of carbon dioxide is approximately 200 times higher than its pressure in the atmosphere. And only with a significant increase in the content of carbon dioxide in the atmosphere (more than 0.6-1%), there are violations in the body, denoted by the term hypercapnia (see). The complete elimination of carbon dioxide from the inhaled air cannot directly have an adverse effect on the human and animal organisms.

Carbon dioxide plays a role in absorbing long-wavelength radiation and maintaining the "greenhouse effect" that raises the temperature near the Earth's surface. The problem of the influence on thermal and other regimes of the atmosphere of carbon dioxide, which enters the air in huge quantities as a waste product of industry, is also being studied.

Atmospheric water vapor (air humidity) also affects the human body, in particular, heat exchange with the environment.

As a result of the condensation of water vapor in the atmosphere, clouds form and precipitation (rain, hail, snow) falls. Water vapor, scattering solar radiation, participate in the creation of the thermal regime of the Earth and the lower layers of the atmosphere, in the formation of meteorological conditions.

Atmosphere pressure

Atmospheric pressure (barometric) is the pressure exerted by the atmosphere under the influence of gravity on the surface of the Earth. The value of this pressure at each point in the atmosphere is equal to the weight of the overlying column of air with a unit base, extending above the place of measurement to the boundaries of the atmosphere. Atmospheric pressure is measured with a barometer (see) and expressed in millibars, in newtons per square meter or the height of the mercury column in the barometer in millimeters, reduced to 0 ° and the normal value of the acceleration of gravity. In table. 2 shows the most commonly used units of atmospheric pressure.

The change in pressure occurs due to uneven heating of air masses located above land and water at different geographical latitudes. As the temperature rises, the density of air and the pressure it creates decrease. A huge accumulation of fast-moving air with reduced pressure (with a decrease in pressure from the periphery to the center of the vortex) is called a cyclone, with increased pressure (with an increase in pressure towards the center of the vortex) - an anticyclone. For weather forecasting, non-periodic changes in atmospheric pressure are important, which occur in moving vast masses and are associated with the emergence, development and destruction of anticyclones and cyclones. Especially large changes in atmospheric pressure are associated with the rapid movement of tropical cyclones. At the same time, atmospheric pressure can vary by 30-40 mbar per day.

The drop in atmospheric pressure in millibars over a distance of 100 km is called the horizontal barometric gradient. Typically, the horizontal barometric gradient is 1–3 mbar, but in tropical cyclones it sometimes rises to tens of millibars per 100 km.

As the altitude rises, atmospheric pressure decreases in a logarithmic relationship: at first very sharply, and then less and less noticeably (Fig. 1). Therefore, the barometric pressure curve is exponential.

The decrease in pressure per unit vertical distance is called the vertical barometric gradient. Often they use the reciprocal of it - the barometric step.

Since the barometric pressure is the sum of the partial pressures of the gases that form the air, it is obvious that with the rise to a height, along with a decrease in the total pressure of the atmosphere, the partial pressure of the gases that make up the air also decreases. The value of the partial pressure of any gas in the atmosphere is calculated by the formula

where P x ​​is the partial pressure of the gas, P z is the atmospheric pressure at altitude Z, X% is the percentage of gas whose partial pressure is to be determined.

Rice. 1. Change in barometric pressure depending on the height above sea level.

Rice. 2. Change in the partial pressure of oxygen in the alveolar air and saturation of arterial blood with oxygen depending on the change in altitude when breathing air and oxygen. Oxygen breathing starts from a height of 8.5 km (experiment in a pressure chamber).

Rice. 3. Comparative curves of the average values ​​of active consciousness in a person in minutes at different heights after a rapid rise while breathing air (I) and oxygen (II). At altitudes above 15 km, active consciousness is equally disturbed when breathing oxygen and air. At altitudes up to 15 km, oxygen breathing significantly prolongs the period of active consciousness (experiment in a pressure chamber).

Since the percentage composition of atmospheric gases is relatively constant, to determine the partial pressure of any gas, it is only necessary to know the total barometric pressure at a given height (Fig. 1 and Table 3).

Table 3. TABLE OF STANDARD ATMOSPHERE (GOST 4401-64) 1

Geometric height (m)	Temperature		barometric pressure			Partial pressure of oxygen (mmHg)
				mmHg Art.

1 Given in abbreviated form and supplemented by the column "Partial pressure of oxygen".

When determining the partial pressure of a gas in moist air, the pressure (elasticity) of saturated vapors must be subtracted from the barometric pressure.

The formula for determining the partial pressure of a gas in moist air will be slightly different than for dry air:

where pH 2 O is the elasticity of water vapor. At t° 37°, the elasticity of saturated water vapor is 47 mm Hg. Art. This value is used in calculating the partial pressures of gases in alveolar air in ground and high-altitude conditions.

Effects of high and low blood pressure on the body. Changes in barometric pressure upwards or downwards have a variety of effects on the organism of animals and humans. The influence of increased pressure is associated with the mechanical and penetrating physical and chemical action of the gaseous medium (the so-called compression and penetrating effects).

The compression effect is manifested by: general volumetric compression, due to a uniform increase in the forces of mechanical pressure on organs and tissues; mechanonarcosis due to uniform volumetric compression at very high barometric pressure; local uneven pressure on tissues that limit gas-containing cavities when there is a broken connection between the outside air and the air in the cavity, for example, the middle ear, the accessory cavities of the nose (see Barotrauma); an increase in gas density in the external respiration system, which causes an increase in resistance to respiratory movements, especially during forced breathing (exercise, hypercapnia).

The penetrating effect can lead to the toxic effect of oxygen and indifferent gases, an increase in the content of which in the blood and tissues causes a narcotic reaction, the first signs of a cut when using a nitrogen-oxygen mixture in humans occur at a pressure of 4-8 atm. An increase in the partial pressure of oxygen initially reduces the level of functioning of the cardiovascular and respiratory systems due to the shutdown of the regulatory effect of physiological hypoxemia. With an increase in the partial pressure of oxygen in the lungs more than 0.8-1 ata, its toxic effect is manifested (damage to the lung tissue, convulsions, collapse).

The penetrating and compressive effects of the increased pressure of the gaseous medium are used in clinical medicine in the treatment of various diseases with general and local impairment of oxygen supply (see Barotherapy, Oxygen therapy).

Lowering the pressure has an even more pronounced effect on the body. Under conditions of an extremely rarefied atmosphere, the main pathogenetic factor leading to loss of consciousness in a few seconds, and to death in 4-5 minutes, is a decrease in the partial pressure of oxygen in the inhaled air, and then in the alveolar air, blood and tissues (Fig. 2 and 3). Moderate hypoxia causes the development of adaptive reactions of the respiratory system and hemodynamics, aimed at maintaining oxygen supply primarily to vital organs (brain, heart). With a pronounced lack of oxygen, oxidative processes are inhibited (due to respiratory enzymes), and aerobic processes of energy production in mitochondria are disrupted. This leads first to a breakdown in the functions of vital organs, and then to irreversible structural damage and death of the body. The development of adaptive and pathological reactions, a change in the functional state of the body and human performance with a decrease in atmospheric pressure is determined by the degree and rate of decrease in the partial pressure of oxygen in the inhaled air, the duration of stay at a height, the intensity of the work performed, the initial state of the body (see Altitude sickness).

A decrease in pressure at altitudes (even with the exclusion of lack of oxygen) causes serious disorders in the body, united by the concept of "decompression disorders", which include: high-altitude flatulence, barotitis and barosinusitis, high-altitude decompression sickness and high-altitude tissue emphysema.

High-altitude flatulence develops due to the expansion of gases in the gastrointestinal tract with a decrease in barometric pressure on the abdominal wall when ascending to altitudes of 7-12 km or more. Of certain importance is the release of gases dissolved in the intestinal contents.

Expansion of gases leads to stretching of the stomach and intestines, raising the diaphragm, changing the position of the heart, irritating the receptor apparatus of these organs and causing pathological reflexes that disrupt breathing and blood circulation. Often there are sharp pains in the abdomen. Similar phenomena sometimes occur in divers when ascending from depth to the surface.

The mechanism of development of barotitis and barosinusitis, manifested by a feeling of congestion and pain, respectively, in the middle ear or accessory cavities of the nose, is similar to the development of high-altitude flatulence.

The decrease in pressure, in addition to expanding the gases contained in the body cavities, also causes the release of gases from liquids and tissues in which they were dissolved under pressure at sea level or at depth, and the formation of gas bubbles in the body.

This process of an exit of the dissolved gases (first of all nitrogen) causes development of a decompression sickness (see).

Rice. 4. Dependence of the boiling point of water on altitude and barometric pressure. The pressure numbers are located below the corresponding altitude numbers.

With a decrease in atmospheric pressure, the boiling point of liquids decreases (Fig. 4). At an altitude of more than 19 km, where the barometric pressure is equal to (or less than) the elasticity of saturated vapors at body temperature (37 °), “boiling” of the interstitial and intercellular fluid of the body can occur, resulting in large veins, in the cavity of the pleura, stomach, pericardium , in loose adipose tissue, that is, in areas with low hydrostatic and interstitial pressure, water vapor bubbles form, high-altitude tissue emphysema develops. Altitude "boiling" does not affect cellular structures, being localized only in the intercellular fluid and blood.

Massive steam bubbles can block the work of the heart and blood circulation and disrupt the functioning of vital systems and organs. This is a serious complication of acute oxygen starvation that develops at high altitudes. Prevention of high-altitude tissue emphysema can be achieved by creating external counterpressure on the body with high-altitude equipment.

The very process of lowering barometric pressure (decompression) under certain parameters can become a damaging factor. Depending on the speed, decompression is divided into smooth (slow) and explosive. The latter proceeds in less than 1 second and is accompanied by a strong bang (as in a shot), the formation of fog (condensation of water vapor due to cooling of expanding air). Typically, explosive decompression occurs at altitudes when the glazing of a pressurized cockpit or pressure suit breaks.

In explosive decompression, the lungs are the first to suffer. A rapid increase in intrapulmonary excess pressure (more than 80 mm Hg) leads to a significant stretching of the lung tissue, which can cause rupture of the lungs (with their expansion by 2.3 times). Explosive decompression can also cause damage to the gastrointestinal tract. The amount of overpressure that occurs in the lungs will largely depend on the rate of air outflow from them during decompression and the volume of air in the lungs. It is especially dangerous if the upper airways at the time of decompression turn out to be closed (when swallowing, holding the breath) or decompression coincides with the phase of deep inspiration, when the lungs are filled with a large amount of air.

Atmospheric temperature

The temperature of the atmosphere initially decreases with increasing altitude (on average, from 15° near the ground to -56.5° at an altitude of 11-18 km). The vertical temperature gradient in this zone of the atmosphere is about 0.6° for every 100 m; it changes during the day and year (Table 4).

Table 4. CHANGES IN THE VERTICAL TEMPERATURE GRADIENT OVER THE MIDDLE STRIP OF THE USSR TERRITORY

Rice. 5. Change in the temperature of the atmosphere at different heights. The boundaries of the spheres are indicated by a dotted line.

At altitudes of 11 - 25 km, the temperature becomes constant and amounts to -56.5 °; then the temperature begins to rise, reaching 30–40° at an altitude of 40 km, and 70° at an altitude of 50–60 km (Fig. 5), which is associated with intense absorption of solar radiation by ozone. From a height of 60-80 km, the air temperature again decreases slightly (up to 60°C), and then progressively increases and reaches 270°C at an altitude of 120 km, 800°C at an altitude of 220 km, 1500°C at an altitude of 300 km, and

on the border with outer space - more than 3000 °. It should be noted that due to the high rarefaction and low density of gases at these heights, their heat capacity and ability to heat colder bodies is very small. Under these conditions, the transfer of heat from one body to another occurs only through radiation. All considered changes in temperature in the atmosphere are associated with the absorption by air masses of the thermal energy of the Sun - direct and reflected.

In the lower part of the atmosphere near the Earth's surface, the temperature distribution depends on the influx of solar radiation and therefore has a mainly latitudinal character, that is, lines of equal temperature - isotherms - are parallel to latitudes. Since the atmosphere in the lower layers is heated from the earth's surface, the horizontal temperature change is strongly influenced by the distribution of continents and oceans, the thermal properties of which are different. Usually, reference books indicate the temperature measured during network meteorological observations with a thermometer installed at a height of 2 m above the soil surface. The highest temperatures (up to 58°C) are observed in the deserts of Iran, and in the USSR - in the south of Turkmenistan (up to 50°), the lowest (up to -87°) in Antarctica, and in the USSR - in the regions of Verkhoyansk and Oymyakon (up to -68° ). In winter, the vertical temperature gradient in some cases, instead of 0.6 °, can exceed 1 ° per 100 m or even take a negative value. During the day in the warm season, it can be equal to many tens of degrees per 100 m. There is also a horizontal temperature gradient, which is usually referred to as a distance of 100 km along the normal to the isotherm. The magnitude of the horizontal temperature gradient is tenths of a degree per 100 km, and in frontal zones it can exceed 10° per 100 m.

The human body is able to maintain thermal homeostasis (see) within a fairly narrow range of outdoor temperature fluctuations - from 15 to 45 °. Significant differences in the temperature of the atmosphere near the Earth and at heights require the use of special protective technical means to ensure the thermal balance between the human body and the environment in high-altitude and space flights.

Characteristic changes in the parameters of the atmosphere (temperature, pressure, chemical composition, electrical state) make it possible to conditionally divide the atmosphere into zones, or layers. Troposphere- the closest layer to the Earth, the upper boundary of which extends at the equator up to 17-18 km, at the poles - up to 7-8 km, in middle latitudes - up to 12-16 km. The troposphere is characterized by an exponential pressure drop, the presence of a constant vertical temperature gradient, horizontal and vertical movements of air masses, and significant changes in air humidity. The troposphere contains the bulk of the atmosphere, as well as a significant part of the biosphere; here all the main types of clouds arise, air masses and fronts are formed, cyclones and anticyclones develop. In the troposphere, due to the reflection of the sun's rays by the snow cover of the Earth and the cooling of the surface layers of air, the so-called inversion takes place, that is, an increase in temperature in the atmosphere from the bottom up instead of the usual decrease.

In the warm season in the troposphere there is a constant turbulent (random, chaotic) mixing of air masses and heat transfer by air flows (convection). Convection destroys fogs and reduces the dust content of the lower atmosphere.

The second layer of the atmosphere is stratosphere.

It starts from the troposphere as a narrow zone (1-3 km) with a constant temperature (tropopause) and extends to heights of about 80 km. A feature of the stratosphere is the progressive rarefaction of the air, the exceptionally high intensity of ultraviolet radiation, the absence of water vapor, the presence of a large amount of ozone and the gradual increase in temperature. The high content of ozone causes a number of optical phenomena (mirages), causes the reflection of sounds and has a significant effect on the intensity and spectral composition of electromagnetic radiation. In the stratosphere there is a constant mixing of air, so its composition is similar to the air of the troposphere, although its density at the upper boundaries of the stratosphere is extremely low. The prevailing winds in the stratosphere are westerly, and in the upper zone there is a transition to easterly winds.

The third layer of the atmosphere is ionosphere, which starts from the stratosphere and extends to altitudes of 600-800 km.

Distinctive features of the ionosphere are the extreme rarefaction of the gaseous medium, a high concentration of molecular and atomic ions and free electrons, as well as high temperature. The ionosphere affects the propagation of radio waves, causing their refraction, reflection and absorption.

The main source of ionization in the high layers of the atmosphere is the ultraviolet radiation of the Sun. In this case, electrons are knocked out of the gas atoms, the atoms turn into positive ions, and the knocked-out electrons remain free or are captured by neutral molecules with the formation of negative ions. The ionization of the ionosphere is influenced by meteors, corpuscular, X-ray and gamma radiation of the Sun, as well as the seismic processes of the Earth (earthquakes, volcanic eruptions, powerful explosions), which generate acoustic waves in the ionosphere, which increase the amplitude and speed of oscillations of atmospheric particles and contribute to the ionization of gas molecules and atoms (see Aeroionization).

The electrical conductivity in the ionosphere, associated with a high concentration of ions and electrons, is very high. The increased electrical conductivity of the ionosphere plays an important role in the reflection of radio waves and the occurrence of auroras.

The ionosphere is the area of ​​flights of artificial earth satellites and intercontinental ballistic missiles. Currently, space medicine is studying the possible effects on the human body of flight conditions in this part of the atmosphere.

Fourth, outer layer of the atmosphere - exosphere. From here, atmospheric gases are scattered into the world space due to dissipation (overcoming the forces of gravity by molecules). Then there is a gradual transition from the atmosphere to interplanetary outer space. The exosphere differs from the latter in the presence of a large number of free electrons that form the 2nd and 3rd radiation belts of the Earth.

The division of the atmosphere into 4 layers is very arbitrary. So, according to electrical parameters, the entire thickness of the atmosphere is divided into 2 layers: the neutrosphere, in which neutral particles predominate, and the ionosphere. The temperature distinguishes the troposphere, stratosphere, mesosphere and thermosphere, separated respectively by tropo-, strato- and mesopauses. The layer of the atmosphere located between 15 and 70 km and characterized by a high content of ozone is called the ozonosphere.

For practical purposes, it is convenient to use the International Standard Atmosphere (MCA), for which the following conditions are accepted: the pressure at sea level at t ° 15 ° is 1013 mbar (1.013 X 10 5 nm 2, or 760 mm Hg); the temperature decreases by 6.5° per 1 km to a level of 11 km (conditional stratosphere), and then remains constant. In the USSR, the standard atmosphere GOST 4401 - 64 was adopted (Table 3).

Precipitation. Since the bulk of the atmospheric water vapor is concentrated in the troposphere, the processes of phase transitions of water, which cause precipitation, proceed mainly in the troposphere. Tropospheric clouds usually cover about 50% of the entire earth's surface, while clouds in the stratosphere (at altitudes of 20-30 km) and near the mesopause, called mother-of-pearl and noctilucent clouds, respectively, are observed relatively rarely. As a result of the condensation of water vapor in the troposphere, clouds form and precipitation occurs.

According to the nature of precipitation, precipitation is divided into 3 types: overcast, torrential, drizzling. The amount of precipitation is determined by the thickness of the layer of fallen water in millimeters; precipitation is measured by rain gauges and precipitation gauges. Precipitation intensity is expressed in millimeters per minute.

The distribution of precipitation in certain seasons and days, as well as over the territory, is extremely uneven, due to the circulation of the atmosphere and the influence of the Earth's surface. Thus, on the Hawaiian Islands, on average, 12,000 mm falls per year, and in the driest regions of Peru and the Sahara, precipitation does not exceed 250 mm, and sometimes does not fall for several years. In the annual dynamics of precipitation, the following types are distinguished: equatorial - with a maximum of precipitation after the spring and autumn equinoxes; tropical - with a maximum of precipitation in summer; monsoon - with a very pronounced peak in summer and dry winter; subtropical - with maximum precipitation in winter and dry summer; continental temperate latitudes - with a maximum of precipitation in summer; marine temperate latitudes - with a maximum of precipitation in winter.

The entire atmospheric-physical complex of climatic and meteorological factors that make up the weather is widely used to promote health, hardening, and for medicinal purposes (see Climatotherapy). Along with this, it has been established that sharp fluctuations in these atmospheric factors can adversely affect the physiological processes in the body, causing the development of various pathological conditions and the exacerbation of diseases, which are called meteotropic reactions (see Climatopathology). Of particular importance in this regard are frequent, long-term disturbances of the atmosphere and abrupt fluctuations in meteorological factors.

Meteotropic reactions are observed more often in people suffering from diseases of the cardiovascular system, polyarthritis, bronchial asthma, peptic ulcer, skin diseases.

Bibliography: Belinsky V. A. and Pobiyaho V. A. Aerology, L., 1962, bibliogr.; Biosphere and its resources, ed. V. A. Kovdy. Moscow, 1971. Danilov A. D. Chemistry of the ionosphere, L., 1967; Kolobkov N. V. Atmosphere and its life, M., 1968; Kalitin H.H. Fundamentals of atmospheric physics as applied to medicine, L., 1935; Matveev L. T. Fundamentals of general meteorology, Physics of the atmosphere, L., 1965, bibliogr.; Minkh A. A. Air ionization and its hygienic value, M., 1963, bibliogr.; it, Methods of hygienic researches, M., 1971, bibliogr.; Tverskoy P. N. Course of meteorology, L., 1962; Umansky S.P. Man in space, M., 1970; Khvostikov I. A. High layers of the atmosphere, L., 1964; X r g and a N A. X. Physics of the atmosphere, L., 1969, bibliogr.; Khromov S.P. Meteorology and climatology for geographical faculties, L., 1968.

Effects of high and low blood pressure on the body- Armstrong G. Aviation medicine, trans. from English, M., 1954, bibliogr.; Saltsman G.L. Physiological bases of a person's stay in conditions of high pressure of the gases of the environment, L., 1961, bibliogr.; Ivanov D. I. and Khromushkin A. I. Human life support systems during high-altitude and space flights, M., 1968, bibliogr.; Isakov P. K., etc. Theory and practice of aviation medicine, M., 1971, bibliogr.; Kovalenko E. A. and Chernyakov I. N. Oxygen of fabrics at extreme factors of flight, M., 1972, bibliogr.; Miles S. Underwater medicine, trans. from English, M., 1971, bibliography; Busby D. E. Space clinical medicine, Dordrecht, 1968.

I. H. Chernyakov, M. T. Dmitriev, S. I. Nepomnyashchy.

And impurities (aerosols). In terms of composition, the air near the earth's surface contains 78% nitrogen (N 2) and about 21% oxygen (O 2), i.e. these two elements account for about 99% of the volume of air. A significant proportion belongs to argon (Ar) - 0.9%. Important components of the atmosphere are ozone (O 3), carbon dioxide (CO 2), and water vapor. The 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.

Carbon dioxide is one of the most important components of plant nutrition. It enters the atmosphere as a result of the processes of combustion, respiration of living organisms and decay, but is consumed in the process of assimilation by plants.

Ozone, most of which is concentrated in the so-called ozone layer (), serves as a natural absorber of the ultraviolet radiation of the Sun, which is harmful to living organisms.

The composition also includes numerous solid and liquid impurities suspended in it - the so-called aerosols. They are of natural and artificial (anthropogenic) origin (dust, soot, ash, ice and sea salt crystals, water droplets, microorganisms, etc.).

A characteristic property of the atmosphere is that the content of at least the main gases (N 2 , O 2 , Ar) changes slightly with height. So, at an altitude of 65 km in the atmosphere, the content of nitrogen is 86%, oxygen - 19, argon - 0.91, and at an altitude of 95 km - 77, 21.3 and 0.82%, respectively. The constancy of the composition of atmospheric air both vertically and horizontally is maintained by its mixing.

The modern composition of the Earth's air was established at least several hundred million years ago and remained unchanged until the production activity of man increased sharply. In the current century, there has been an increase in the content of CO 2 around the globe by about 10 - 12%.

The atmosphere has a complex structure. In accordance with the change in temperature with height, four layers are distinguished: the troposphere (up to 12 km), the stratosphere (up to 50 km), the upper ones, which include the mesosphere (up to 80 km) and the thermosphere, gradually turning into interplanetary space. In the troposphere and mesosphere, it decreases with height, while in the stratosphere and thermosphere, on the contrary, it increases.

Troposphere - the lower layer of the atmosphere, the height of which varies from 8 km above the poles to 17 km (average 12 km). It contains up to 4/5 of the entire mass of the atmosphere and almost all of the water vapor. Air is dominated by nitrogen, oxygen, argon and carbon dioxide. The air of the troposphere is heated from the earth's surface - the surface of water and land. The air in the troposphere is constantly churning. Water vapor condenses, and forms, rains fall, and storms occur. The temperature decreases with height by an average of 0.6°C for every 100 m, and at the upper limit it is — 70°C at the equator and -65°C over the North Pole.

The stratosphere is the second layer of the atmosphere above the troposphere. It extends up to a height of 50 km. Gases in the stratosphere are constantly mixed, in its lower part there are stable so-called jet streams of air with a speed of up to 300 km/h. The color of the sky in the stratosphere does not seem blue, as in the troposphere, but purple. This is due to the rarefaction of the air, as a result of which the sun's rays almost do not scatter. There is very little water vapor in the stratosphere, and there are no active processes of cloud formation and precipitation. Occasionally, in the stratosphere at an altitude of » 30 km in high latitudes, thin bright clouds appear, called mother-of-pearl. It is in the stratosphere, approximately at an altitude of 20-30 km, that a layer of maximum ozone concentration is released - the ozone layer (ozone screen, ozonosphere). Thanks to ozone, the temperature in the stratosphere and at the upper boundary is within +50 +55°C.

Above the stratosphere are the high layers of the atmosphere - the mesosphere and the thermosphere.

Mesosphere - the middle sphere extends from 40-45 to 80-85 km. The color of the sky in the mesosphere appears black, day and night bright non-flickering stars are visible. The temperature drops to 75-90°C below zero.

The thermosphere extends from the mesosphere and above. Its upper limit is supposed to be at an altitude of 800 km. It mainly consists of ions formed under the influence of cosmic rays, the action of which on gas molecules leads to their decay into charged particles of atoms. The layer of ions in the thermosphere is called the ionosphere, which is characterized by high electrification and from which, like a mirror, long and medium radio waves are reflected. In the ionosphere arise - the glow of rarefied gases under the influence of electrically charged particles flying from the Sun.

The thermosphere is characterized by an increasing increase in temperature: at an altitude of 150 km it reaches 220-240°C; at an altitude of 500-600 km it exceeds 1500°C.

Above the thermosphere (i.e., above 800 km) is the outer sphere, the sphere of dispersion is the exosphere, which extends up to several thousand kilometers.

It is conditionally considered that the atmosphere extends up to an altitude of 3000 km.

At sea level 1013.25 hPa (about 760 mmHg). The average global 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 geographical 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 characterized in general by an increase in temperature with height. The transition 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. Higher, the temperature rises due to the absorption of solar UV radiation by ozone, slowly at first, and faster from a level of 34-36 km. 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 drops again with height, is called the mesosphere, at its upper boundary - the mesopause - the temperature reaches 150-160 K in summer, and 200-230 K in winter. The thermosphere begins above the mesopause - a layer, characterized by a rapid increase in temperature, reaching values ​​of 800-1200 K at an altitude of 250 km. The corpuscular and X-ray radiation of the Sun is absorbed in the thermosphere, meteors are slowed down and burned out, so it performs the function of the Earth's protective layer. Even higher is the exosphere, from where atmospheric gases are dissipated into world space due to dissipation and where a gradual transition from the atmosphere to interplanetary space takes place.

Composition of the atmosphere. Up to a height 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 components of the air is constant over time and uniform in different geographical areas. The content of water vapor and ozone is variable in space and time; despite the low content, their role in atmospheric processes is very significant.

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

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

An important component of atmospheric air is ozone, 90% concentrated in the stratosphere (between 10 and 50 km), about 10% of it is in the troposphere. Ozone provides absorption of 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 the latitude and season, ranging 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 the ozone holes observed in spring in Antarctica since the early 1980s, the ozone content can drop to 0.07 cm. grows at high latitudes. An essential 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 the anthropogenic factor. Its latitudinal and seasonal variability is observed, associated with plant photosynthesis and solubility in sea water (according to Henry's law, the solubility of gas in water decreases with increasing 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. There are aerosols of natural and anthropogenic origin. Aerosol is formed in the process of gas-phase reactions from the products of plant life and human economic activity, volcanic eruptions, as a result of dust being lifted by the wind from the surface of the planet, especially from its desert regions, and is also formed from cosmic dust entering 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 industries, fuel combustion, etc. Therefore, in some areas the composition of the atmosphere differs markedly from ordinary air, which required the creation of a special service for monitoring and controlling the level of atmospheric air pollution.

Atmospheric evolution. The modern atmosphere is apparently of secondary origin: it was formed from the gases released by the solid shell of the Earth after the formation of the planet was completed 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 the components of the atmosphere and the rocks that make up the earth's crust; photochemical reactions in the atmosphere itself under the influence of solar UV radiation; accretion (capture) of the matter of the interplanetary medium (for example, meteoric matter). The development of the atmosphere is closely connected with geological and geochemical processes, and for 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, which carried them out from the depths of the Earth. Oxygen appeared in appreciable 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. During the Phanerozoic (the last 570 million years of the Earth's history), the amount of carbon dioxide in the atmosphere varied widely in accordance with the level of volcanic activity, ocean temperature and photosynthesis. Most of this time, the concentration of carbon dioxide in the atmosphere was significantly higher than the current one (up to 10 times). The amount of oxygen in the atmosphere of the Phanerozoic 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 atmosphere of the Phanerozoic. Fluctuations in the amount of carbon dioxide have had a significant impact on the climate in the past, increasing the greenhouse effect with an increase in the concentration of carbon dioxide, due to which the climate during the main part of the Phanerozoic was much warmer than in the modern era.

atmosphere and life. Without an atmosphere, Earth would be a dead planet. Organic life proceeds in close interaction with the atmosphere and its associated climate and weather. Insignificant 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, and ozone are the most important atmospheric gases for the life of organisms. When carbon dioxide is absorbed by photosynthetic plants, organic matter is created, which is used as an energy source by the vast majority of living beings, including humans. Oxygen is necessary for the existence of aerobic organisms, for which the energy supply 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 Sun's harsh UV radiation, significantly attenuates this life-threatening portion of the sun's radiation. Condensation of water vapor in the atmosphere, the formation of clouds and the subsequent precipitation of precipitation supply water to land, without which no form of life is 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 significantly depends 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 quite well, but actively absorbs the thermal long-wave radiation of the earth's surface, part of which returns to the surface in the form of counter radiation that compensates for the radiative heat loss of the earth's surface (see Atmospheric radiation ). In the absence of an atmosphere, the average temperature of the earth's surface would be -18°C, in reality it is 15°C. 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 black soil) to 70-90% for freshly fallen snow. The radiative heat exchange between the earth's surface and the atmosphere essentially depends 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 the condensation of water vapor. The shares of these heat inflows are on average 20%, 7% and 23%, respectively. About 20% of heat is also added here due to the absorption of direct solar radiation. The flux of solar radiation per unit of time through a single 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 / m 2, the changes are 1-2 W / m 2 depending on cycle of solar activity. With a planetary albedo of about 30%, the time-average global influx of solar energy to the planet is 239 W/m 2 . 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 33°C difference 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 surface of the Earth, 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 river flow that flows 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 relative position of the oceans and continents also significantly affects the distribution of temperature. Due to the large mass of ocean waters and the high heat capacity of water, seasonal fluctuations in ocean surface temperature are much less than those of land. In this regard, in the middle and high latitudes, the air temperature over the oceans is noticeably lower in summer than over the continents, and higher in winter.

The uneven heating of the atmosphere in different regions of the globe causes a distribution of atmospheric pressure that is not uniform in space. At sea level, the pressure distribution is characterized by relatively low values ​​near the equator, an increase in the subtropics (high-pressure zones) and a decrease in middle and high latitudes. At the same time, over the continents of extratropical latitudes, the pressure is usually increased in winter, and lowered in summer, which is associated with the temperature distribution. Under the action of a pressure gradient, the air experiences an acceleration directed 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 (the Coriolis force), the friction force, which decreases with height, and in the case of curvilinear trajectories, the centrifugal force. Of great importance is the turbulent mixing of air (see Turbulence in the atmosphere).

A complex system of air currents (general circulation of the atmosphere) is associated with the planetary distribution of pressure. In the meridional plane, on average, two or three meridional circulation cells are traced. Near the equator, heated air rises and falls in the subtropics, forming a Hadley cell. The air of the reverse Ferrell cell also descends there. At high latitudes, a direct polar cell is often traced. Meridional circulation velocities are on 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 speeds in the middle troposphere of about 15 m/s. There are relatively stable wind systems. These include 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 quite stable - air currents that have 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 middle latitudes, the movement of air masses is mainly western (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 differ in smaller sizes, but very high wind speeds, reaching hurricane force (33 m/s or more), the so-called tropical cyclones. In the Atlantic and eastern Pacific they are called hurricanes, and in the western Pacific they are called typhoons. In the upper troposphere and lower stratosphere, in the areas separating the direct cell of the Hadley meridional circulation and the reverse Ferrell cell, relatively narrow, hundreds of kilometers wide, jet streams with sharply defined 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 coming at different latitudes to the earth's surface, which is diverse in 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 changes little during the year. In the equatorial zone, a lot of precipitation usually falls, which creates conditions for excessive moisture there. In tropical zones, the amount of precipitation decreases and in some areas becomes very small. Here are the vast deserts of the Earth.

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

In the 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, occupying over 65% of Russia's area, mainly in Siberia.

Over the past decades, changes in the global climate have become more and more noticeable. The temperature rises more at high latitudes than at low latitudes; 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 increased by 1.5-2 ° C, and in some regions of Siberia an increase of several degrees is observed. This is associated with an increase in the greenhouse effect due to an increase in the concentration of small gaseous impurities.

The weather is determined by the conditions of atmospheric circulation and the geographical location of the area, it is most stable in the tropics and most changeable in the middle and high latitudes. Most of all, the weather changes in the zones of change of air masses, due to the passage of atmospheric fronts, cyclones and anticyclones, carrying precipitation and increasing wind. Data for weather forecasting is collected from ground-based weather stations, ships and aircraft, and meteorological satellites. See also meteorology.

Optical, acoustic and electrical phenomena in the atmosphere. When electromagnetic radiation propagates in the atmosphere, as a result of refraction, absorption and scattering of light by air and various particles (aerosol, ice crystals, water drops), various optical phenomena arise: rainbow, crowns, halo, mirage, etc. Light scattering determines the apparent height of the firmament and blue color of the sky. The visibility range of objects is determined by the conditions of light propagation in the atmosphere (see Atmospheric visibility). The transparency of the atmosphere at different wavelengths determines the communication range and the possibility of detecting objects with instruments, including the possibility of astronomical observations from the Earth's surface. For studies of optical inhomogeneities in the stratosphere and mesosphere, the phenomenon of twilight plays an important role. For example, photographing twilight from spacecraft makes it possible to detect aerosol layers. 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).

The propagation of sound 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 wind systems and the course of temperature in the stratosphere and mesosphere. In a stably stratified atmosphere, when the temperature falls with height 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 electric field caused by it, the atmosphere, together with the electrically charged ionosphere and magnetosphere, create a global electrical circuit. An important role is played by the formation of clouds and lightning electricity. The danger of lightning discharges necessitated the development of methods for lightning protection of buildings, structures, power lines and communications. This phenomenon is of particular danger to 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 on 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 a number of light and heavy ions, which vary greatly depending on the 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 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 past century was given by freons, which practically did not exist in the atmosphere until the middle of the 20th century. These substances are recognized as stratospheric ozone depleters and their production is prohibited by the 1987 Montreal Protocol. The increase in carbon dioxide concentration in the atmosphere is caused by the burning of ever-increasing amounts of coal, oil, gas and other carbon fuels, as well as the deforestation, which reduces the absorption of carbon dioxide through photosynthesis. 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 climate warming.

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

Study of the atmosphere. Information about the 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 about 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, where meteorological measurements are made with the help of radiosondes up to a height of 30-35 km. At a number of stations, observations are made of atmospheric ozone, electrical phenomena in the atmosphere, and the chemical composition of the air.

Data from ground stations are supplemented by observations on the oceans, where "weather ships" operate, permanently located in certain areas of the World Ocean, as well as meteorological information received from research and other ships.

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

Lit .: Budyko M. I. Climate in the past and 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: A Handbook. L., 1991; Khromov S. P., Petrosyants M. A. Meteorology and climatology. 5th ed. M., 2001.

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

Atmosphere- this is the air shell that surrounds the Earth and the force of gravity associated with it. The atmosphere is involved in the daily rotation and annual movement of our planet. Atmospheric air is a mixture of gases in which liquid (water droplets) and solid particles (smoke, dust) are suspended. The gas composition of the atmosphere is unchanged up to a height of 100-110 km, which is due to the balance in nature. The volume fractions of gases are: nitrogen - 78%, oxygen - 21%, inert gases (argon, xenon, krypton) - 0.9%, carbon - 0.03%. In addition, water vapor is always present in the atmosphere.

In addition to biological processes, oxygen, nitrogen and carbon are actively involved in the chemical weathering of rocks. The role of ozone 03 is very important, absorbing most of the ultraviolet radiation of the Sun, in large doses it is dangerous for living organisms. Solid particles, which are especially abundant above cities, serve as condensation nuclei (water drops and snowflakes form around them).

Height, boundaries and structure of the atmosphere

The upper boundary of the atmosphere is conditionally drawn at an altitude of about 1000 km, although it can be traced much higher - up to 20,000 km, but there it is very rarefied.

Through the different nature of changes in air temperature with altitude, other physical properties in the atmosphere, several parts are distinguished, which are separated from each other by transitional layers.

The troposphere is the lowest and densest layer of the atmosphere. Its upper boundary is drawn at an altitude of 18 km above the equator and 8-12 km above the poles. The temperature in the troposphere decreases by an average of 0.6 ° C for every 100 m. It is characterized by significant horizontal differences in the distribution of temperature, pressure, wind speed, as well as the formation of clouds and precipitation. In the troposphere there is an intense vertical movement of air - convection. It is in this lower layer of the atmosphere that the weather is mainly formed. Almost all of the water vapor in the atmosphere is concentrated here.

The stratosphere extends mainly up to a height of 50 km. The ozone concentration at an altitude of 20-25 km reaches its highest values, forming an ozone screen. The air temperature in the stratosphere, as a rule, increases with height by an average of 1-2 ° C per 1 km, reaching 0 ° C and higher at the upper limit. This is due to the absorption of solar energy by ozone. There is almost no water vapor and clouds in the stratosphere, and hurricane-force winds blow at speeds up to 300-400 km/h.

In the mesosphere, the air temperature drops to -60 ... - 100 ° C, intensive vertical and horizontal air movements occur.

In the upper layers of the thermosphere, where the air is highly ionized, the temperature rises again to 2000 ° C. Here, auroras and magnetic storms are observed.

The atmosphere plays a big role in the life of the Earth. It prevents excessive heating of the earth's surface during the day and its cooling at night, redistributes moisture on the Earth, protects its surface from meteorite impacts. The presence of an atmosphere is an indispensable condition for the existence of organic life on our planet.

Solar radiation. Heating of the atmosphere

The sun radiates a huge amount of energy, only a small fraction of which is received by the Earth.

The emission of light and heat from the Sun is called solar radiation. Solar radiation travels a long way in the atmosphere before reaching the earth's surface. Overcoming it, it is largely absorbed and dissipated by the air shell. Radiation that directly reaches the earth's surface in the form of direct rays is called direct radiation. Part of the radiation that is scattered in the atmosphere also reaches the Earth's surface in the form of scattered radiation.

The combination of direct and diffuse radiation entering a horizontal surface is called total solar radiation. The atmosphere absorbs about 20% of the solar radiation entering its upper boundary. Another 34% of the radiation is reflected from the Earth's surface and atmosphere (reflected radiation). 46% of solar radiation is absorbed by the earth's surface. Such radiation is called absorbed (absorbed).

The ratio of the intensity of the reflected solar radiation to the intensity of all the radiant energy of the Sun entering the upper boundary of the atmosphere is called the Earth's albedo and is expressed as a percentage.

So, the albedo of our planet, together with its atmosphere, averages 34%. The albedo value at different latitudes has significant differences associated with the color of the surface, vegetation, cloudiness, and the like. A surface area covered with fresh snow reflects 80-85% of radiation, grass vegetation and sand - respectively 26% and 30%, and water - only 5%.

The amount of solar energy received by individual parts of the Earth depends primarily on the angle of incidence of the sun's rays. The straighter they fall (i.e., the greater the height of the Sun above the horizon), the greater the amount of solar energy per unit area.

The dependence of the total radiation on the angle of incidence of the rays is due to two reasons. Firstly, the smaller the angle of incidence of the sun's rays, the larger the area distributed this flux of light and the less energy per unit surface. Secondly, the smaller the angle of incidence, the longer the path of the beam in the atmosphere.

The amount of solar radiation that hits the earth's surface is affected by the transparency of the atmosphere, especially cloudiness. The dependence of solar radiation on the angle of incidence of solar rays and the transparency of the atmosphere determines the zonal nature of its distribution. Differences in the amount of total solar radiation at the same latitude are mainly caused by cloudiness.

The amount of heat entering the earth's surface is determined in calories per unit area (1 cm) per unit time (1 year).

The absorbed radiation is spent on heating the thin near-surface layer of the Earth and water evaporation. The heated earth's surface transfers heat to the environment through radiation, conduction, convection and condensation of water vapor.

Changes in air temperature depending on the geographical latitude of the place and on the height above sea level

The total radiation decreases from the equatorial-tropical latitudes to the poles. It is maximum - about 850 J / m2 per year (200 kcal / cm2 per year) - in tropical deserts, where direct solar radiation through the high altitude of the Sun and a cloudless sky is intense. In the summer half of the year, the differences in the total solar radiation inflow between low and high latitudes are smoothed out. This is due to the longer duration of solar illumination, especially in the polar regions, where the polar day lasts even half a year.

Although the total solar radiation entering the earth's surface is partially reflected by it, however, most of it is absorbed by the earth's surface and converted into heat. Part of the total radiation that remains after its costs for reflection and for thermal radiation of the earth's surface is called the radiation balance (residual radiation). In general, for the year it is positive everywhere on Earth, with the exception of the high ice deserts of Antarctica and Greenland. The radiation balance naturally decreases in the direction from the equator to the poles, where it is close to zero.

Accordingly, the air temperature is distributed zonal, that is, it decreases in the direction from the equator to the poles. .Air temperature also depends on the height of the area above sea level: the higher the area, the lower the temperature.

Significant influence on air temperature distribution of land and water. The surface of the land heats up quickly, but quickly cools, and the surface of the water heats up more slowly, but retains heat longer and releases it more slowly into the air.

As a result of the different intensity of heating and cooling of the Earth's surface day and night, in the warm and cold seasons, the air temperature changes during the day and year.

Thermometers are used to measure air temperature. it is measured 8 times a day and the average is taken per day. At the average daily temperature, monthly averages are calculated. It is they who, as a rule, are shown on climate maps by isotherms (lines that connect points with the same temperature over a certain period of time). To characterize temperatures, average monthly January and July indicators are most often taken, less often annual ones. ,

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

The role of the atmosphere in the life of the Earth

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

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

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

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

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

Sound does not propagate.

There is no aerodynamic force and drag.

Heat is not transferred by convection, etc.

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

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

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

Troposphere.

Stratosphere.

Mesosphere.

Thermosphere.

Exosphere

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

The structure of the Earth's atmosphere by layers:

What is the earth's atmosphere made of?

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

Troposphere

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

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

Stratosphere

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

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

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

Mesosphere

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

Thermosphere

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

Ionosphere.

exospheres.

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

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

Exosphere

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

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