The structure of the earth's atmosphere diagram. I. Changes in the state of the atmosphere. Chemical composition of the Earth's atmosphere

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

The set of branches of physics and chemistry that study the atmosphere is usually called atmospheric physics. The atmosphere determines the weather on the Earth's surface, meteorology studies weather, and climatology deals with long-term climate variations.

Physical properties

The thickness of the atmosphere is approximately 120 km from the Earth's surface. The total mass of air in the atmosphere is (5.1-5.3) 1018 kg. Of these, the mass of dry air is (5.1352 ± 0.0003) 1018 kg, the total mass of water vapor is on average 1.27 1016 kg.

The molar mass of clean dry air is 28.966 g/mol, and the density of air at the sea surface is approximately 1.2 kg/m3. The pressure at 0 °C at sea level is 101.325 kPa; critical temperature- −140.7 °C (~132.4 K); critical pressure - 3.7 MPa; Cp at 0 °C - 1.0048·103 J/(kg·K), Cv - 0.7159·103 J/(kg·K) (at 0 °C). Solubility of air in water (by mass) at 0 °C - 0.0036%, at 25 °C - 0.0023%.

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

Chemical composition

The Earth's atmosphere arose as a result of the release of gases during volcanic eruptions. With the advent of the oceans and the biosphere, it was formed due to gas exchange with water, plants, animals and the products of their decomposition in soils and swamps.

Currently, 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 almost constant, with the exception of water (H2O) and carbon dioxide (CO2).

Composition of dry air


Nitrogen
Oxygen
Argon
Water
Carbon dioxide
Neon
Helium
Methane
Krypton
Hydrogen
Xenon
Nitrous oxide

In addition to the gases indicated in the table, the atmosphere contains SO2, NH3, CO, ozone, hydrocarbons, HCl, HF, Hg vapor, I2, as well as NO and many other gases in small quantities. The troposphere constantly contains a large amount of suspended solid and liquid particles (aerosol).

The structure of the atmosphere

Troposphere

Its upper limit is at an altitude of 8-10 km in polar, 10-12 km in temperate and 16-18 km in tropical latitudes; lower in winter 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 the total water vapor present in the atmosphere. Turbulence and convection are highly developed in the troposphere, clouds arise, and cyclones and anticyclones develop. Temperature decreases with increasing altitude with an average vertical gradient of 0.65°/100 m

Tropopause

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

Stratosphere

A layer of the atmosphere located at an altitude of 11 to 50 km. Characterized by a slight change in temperature in the 11-25 km layer (lower layer of the stratosphere) and an increase in temperature in the 25-40 km layer from −56.5 to 0.8 ° C (upper layer of the stratosphere or inversion region). Having reached a value of about 273 K (almost 0 °C) at an altitude of about 40 km, the temperature remains constant up to an altitude of about 55 km. This region of constant temperature is called the stratopause and is the boundary between the stratosphere and mesosphere.

Stratopause

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

Mesosphere

The mesosphere begins at an altitude of 50 km and extends to 80-90 km. Temperature decreases with height with an average vertical gradient of (0.25-0.3)°/100 m. The main energy process is radiant heat transfer. Complex photochemical processes with the participation of free radicals, vibrationally excited molecules, etc., cause the glow of the atmosphere.

Mesopause

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

Karman Line

The height above sea level, which is conventionally accepted as the boundary between the Earth's atmosphere and space. According to the FAI definition, the Karman line is located at an altitude of 100 km above sea level.

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 to high altitudes. Under the influence of ultraviolet and x-ray solar radiation and cosmic radiation, ionization of the air (“auroras”) occurs - the main regions of the ionosphere lie inside the thermosphere. At altitudes above 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 thermosphere. In this region, the absorption of solar radiation is negligible and the temperature does not actually change with altitude.

Exosphere (scattering sphere)

The exosphere is a dispersion zone, the outer part of the thermosphere, located above 700 km. The gas in the exosphere is very rarefied, and from here its particles leak into interplanetary space (dissipation).

Up to an altitude of 100 km, the atmosphere is a homogeneous, well-mixed mixture of gases. In higher layers, the distribution of gases by height depends on their molecular masses; the concentration of heavier gases decreases faster with distance from the Earth's surface. Due to the decrease in gas density, the temperature drops from 0 °C in the stratosphere to −110 °C in the mesosphere. However, the kinetic energy of individual particles at altitudes of 200-250 km corresponds to a temperature of ~150 °C. Above 200 km, significant fluctuations in temperature and gas density in time and space are observed.

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 represents only part of the interplanetary matter. The other part consists of dust particles of cometary and meteoric origin. In addition to extremely rarefied dust 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%; mass of the mesosphere - no more than 0.3%, thermosphere - less than 0.05% of total mass atmosphere. Based on the electrical properties in the atmosphere, the neutronosphere and ionosphere are distinguished. It is currently believed that the atmosphere extends to an altitude of 2000-3000 km.

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

Other properties of the atmosphere and effects on the human body

Already at an altitude of 5 km above sea level, an untrained person begins to experience oxygen starvation and without adaptation, a person’s performance is significantly reduced. The physiological zone of the atmosphere ends here. Human breathing becomes impossible at an altitude of 9 km, although up to approximately 115 km the atmosphere contains oxygen.

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

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

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

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

As we rise to an ever greater height above the Earth's surface, such familiar phenomena observed in the lower layers of the atmosphere as sound propagation, the occurrence of aerodynamic lift and drag, heat transfer by convection, etc. gradually weaken and then completely disappear.

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

At altitudes above 100 km, the atmosphere is deprived of another remarkable property - the ability to absorb, conduct and transmit thermal energy by convection (i.e. by mixing air). This means that various elements of equipment, orbital equipment space station will not be able to cool outside in the way that is usually done on an airplane - with the help of air jets and air radiators. At such a height, as in space generally, the only way to transfer heat is thermal radiation.

History of atmospheric formation

According to the most common theory, the Earth's atmosphere has had three different compositions over time. Initially, it 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). This is how the secondary atmosphere was formed (about three billion years before the present day). This atmosphere was restorative. Further, the process of atmosphere formation was determined by the following factors:

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

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

Nitrogen

The formation of a large amount of nitrogen N2 is due to the oxidation of the ammonia-hydrogen atmosphere by molecular oxygen O2, which began to come from the surface of the planet as a result of photosynthesis, starting 3 billion years ago. Nitrogen N2 is also 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 N2 reacts only under specific conditions (for example, during a lightning discharge). Oxidation molecular nitrogen ozone during electrical discharges is used in small quantities in the industrial production of nitrogen fertilizers. Cyanobacteria (blue-green algae) and nodule bacteria that form rhizobial symbiosis with leguminous plants, the so-called, can oxidize it with low energy consumption and convert it into a biologically active form. green manure.

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, ferrous form of iron contained in the oceans, etc. At the end of this stage, the oxygen content in the atmosphere began to increase. Gradually, a modern atmosphere with oxidizing properties 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.

During the Phanerozoic, the composition of the atmosphere and oxygen content underwent changes. They correlated primarily with the rate of deposition of organic sediment. Thus, during periods of coal accumulation, the oxygen content in the atmosphere apparently significantly exceeded the modern level.

Carbon dioxide

The CO2 content 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 Earth's biosphere. Almost the entire current biomass of the planet (about 2.4 1012 tons) is formed due to carbon dioxide, nitrogen and water vapor contained in the atmospheric air. Organics buried in the ocean, swamps and forests turn into coal, oil and natural gas.

Noble gases

The source of noble gases - argon, helium and krypton - is volcanic eruptions and the decay of radioactive elements. The Earth in general and the atmosphere in particular are depleted of inert gases compared to space. It is believed that the reason for this lies in the continuous leakage of gases into interplanetary space.

Air pollution

Recently, humans have begun to influence the evolution of the atmosphere. The result of his activities was a constant increase in the content of carbon dioxide in the atmosphere due to the combustion of hydrocarbon fuels accumulated in previous geological eras. Huge amounts of CO2 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 substances of plant and animal origin, as well as due to volcanism and human industrial activity. Over the past 100 years, the CO2 content 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 CO2 in the atmosphere will double and could lead to global climate change.

Fuel combustion is the main source of polluting gases (CO, NO, SO2). Sulfur dioxide is oxidized by atmospheric oxygen to SO3, and nitrogen oxide to NO2 in the upper layers of the atmosphere, which in turn interact with water vapor, and the resulting sulfuric acid H2SO4 and nitric acid HNO3 fall to the surface of the Earth in the form of the so-called. acid rain. Using motors internal combustion leads to significant atmospheric pollution with nitrogen oxides, hydrocarbons and lead compounds (tetraethyl lead) Pb(CH3CH2)4.

Aerosol pollution of the atmosphere is caused by both natural causes (volcanic eruptions, dust storms, entrainment of droplets of sea water and plant pollen, etc.) and economic activity humans (mining ores and building materials, burning fuel, making cement, etc.). Intense large-scale release of particulate matter into the atmosphere is one of the possible causes of climate change on the planet.

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The gaseous envelope surrounding our planet Earth, known as the atmosphere, consists of five main layers. These layers originate on the surface of the planet, from sea level (sometimes below) and rise to outer space in the following sequence:

Troposphere;
Stratosphere;
Mesosphere;
Thermosphere;
Exosphere.

Diagram of the main layers of the Earth's atmosphere

In between each of these main five layers are transition zones called "pauses" where changes in air temperature, composition and density occur. Together with pauses, the Earth's atmosphere includes a total of 9 layers.

Troposphere: where weather occurs

Of all the layers of the atmosphere, the troposphere is the one with which we are most familiar (whether you realize it or not), since we live on its bottom - the surface of the planet. It envelops the surface of the Earth and extends upward for several kilometers. The word troposphere means "change of the globe." A very appropriate name, since this layer is where our everyday weather occurs.

Starting from the surface of the planet, the troposphere rises to a height of 6 to 20 km. The lower third of the layer, closest to us, contains 50% of all atmospheric gases. This is the only part of the entire atmosphere that breathes. Due to the fact that the air is heated from below by the earth's surface, which absorbs the thermal energy of the Sun, the temperature and pressure of the troposphere decrease with increasing altitude.

At the top there is a thin layer called the tropopause, which is just a buffer between the troposphere and the stratosphere.

Stratosphere: home of the ozone

The stratosphere is the next layer of the atmosphere. It extends from 6-20 km to 50 km above the Earth's surface. This is the layer in which most commercial airliners fly and hot air balloons travel.

Here the air does not flow up and down, but moves parallel to the surface in very fast air currents. As you rise, the temperature increases, thanks to the abundance of naturally occurring ozone (O3), a byproduct of solar radiation and oxygen, which has the ability to absorb the sun's harmful ultraviolet rays (any increase in temperature with altitude in meteorology is known as an "inversion") .

Because the stratosphere has warmer temperatures at the bottom and cooler temperatures at the top, convection (vertical movement of air masses) is rare in this part of the atmosphere. In fact, you can view a storm raging in the troposphere from the stratosphere because the layer acts as a convection cap that prevents storm clouds from penetrating.

After the stratosphere there is again a buffer layer, this time called the stratopause.

Mesosphere: middle atmosphere

The mesosphere is located approximately 50-80 km from the Earth's surface. The upper mesosphere is the coldest natural place on Earth, where temperatures can drop below -143°C.

Thermosphere: upper atmosphere

After the mesosphere and mesopause comes the thermosphere, located between 80 and 700 km above the surface of the planet, and contains less than 0.01% of the total air in the atmospheric envelope. Temperatures here reach up to +2000° C, but due to the extreme thinness of the air and the lack of gas molecules to transfer heat, these high temperatures are perceived as very cold.

Exosphere: the boundary between the atmosphere and space

At an altitude of about 700-10,000 km above the earth's surface is the exosphere - the outer edge of the atmosphere, bordering space. Here weather satellites orbit the Earth.

What about the ionosphere?

The ionosphere is not a separate layer, but in fact the term is used to refer to the atmosphere between 60 and 1000 km altitude. It includes the uppermost parts of the mesosphere, the entire thermosphere and part of the exosphere. The ionosphere gets its name because in this part of the atmosphere the radiation from the Sun is ionized when it passes through the Earth's magnetic fields at and. This phenomenon is observed from the ground as the northern lights.

A change in the composition of the atmosphere leads to an impact on the radiation regime of the atmosphere - this is the main mechanism of anthropogenic influence on the global climate system at the current and expected level of industrial development in the coming decades.

Contribution of atmospheric greenhouse gases (see. Greenhouse effect) constitutes the bulk of this impact. The effect of greenhouse gas concentrations on temperature is determined by the absorption of long-wave radiation coming from the Earth, and, consequently, a decrease in effective radiation at the earth's surface. In this case, the maximum temperatures increase, and the temperature of higher layers of the atmosphere decreases due to large radiation losses. This effect is enhanced by two circumstances:

1) an increase in the amount of water vapor in the atmosphere during warming, which also blocks long-wave radiation;

2) retreat of polar ice during warming, which reduces the Earth's albedo at relatively high latitudes.

All long-lived greenhouse gases and ozone provide positive radiative forcing (2.9 ± 0.3 W/m2). The total radiation impact of anthropogenic factors associated with changes in the concentration of all greenhouse gases and aerosols is 1.6 (from 0.6 to 2.4) W/m2. All types of aerosols create a radiation effect directly and indirectly by changing cloud albedo. The total aerosol impact is negative (–1.3 ± 0.8 W/m2). However, the reliability of these estimates is much lower than those obtained for greenhouse gases (Assessment Report, 2008).

Greenhouse gases in the atmosphere that are significantly affected by economic activities:

– carbon dioxide(CO 2) is the most important greenhouse gas in terms of climate control. Over the past 250 years, there has been an unprecedented increase in its concentration in the atmosphere by 35%. In 2005 it amounted to 379 million –1;

– methane(CH 4) is the second most important greenhouse gas after CO 2 ; its concentration increased 2.5 times compared to the pre-industrial period and amounted to 1774 ppb in 2005;

– nitrous oxide(N2O), its concentration increased by 18% by 2005 compared to the pre-industrial period and amounted to 319 billion –1; Currently, approximately 40% of the amount of N 2 O entering the atmosphere is due to economic activities (fertilizers, livestock farming, chemical industry).

On rice. 4.7 the time course of carbon dioxide concentration is presented ( A), methane ( b) and nitrous oxide ( V) in the atmosphere and their changes over the past 10,000 years and since 1750. The time course was obtained from measurements in ice deposits from various researchers and measurements in the atmosphere. The figure clearly shows the progressive increase in CO 2 and other gases during the industrial era.

According to the IPCC Fourth Assessment Report (2007), during the industrial era there is a significant increase in atmospheric concentrations of climate-active gases. Thus, over the past 250 years, atmospheric concentrations of carbon dioxide (CO 2) have increased from 280 to 379 ppm (parts per million per unit volume). The current concentration of greenhouse gases in the atmosphere, as determined by the analysis of air bubbles from ice cores that preserved the composition of the ancient atmosphere of Antarctica, is much higher than at any time in the last 10 thousand years. Global atmospheric methane concentrations have increased from 715 to 1,774 ppb (parts per billion per unit volume) during the industrial era. The most dramatic increase in greenhouse gas concentrations has been observed in recent decades, resulting in warming of the atmosphere.

So the process modern climate warming occurs against the backdrop of sustainable increase in greenhouse gas concentrations, and first of all, carbon dioxide (CO 2). Thus, according to data for 1999, CO 2 emissions as a result of human activity, from the combustion of fossil fuels, reached 6.2 billion tons in 1996, which is almost 4 times more than in 1950. From 1750 to 2000, there was an increase in the concentration of carbon dioxide in the atmosphere by 31% (Perevedentsev Yu.P., 2009).

Time course of CO 2 concentration at Russian station Teriberka (Figure 4.8) shows that the average 20-year growth rate of CO 2 was 1.7 million –1 per year with significant seasonal fluctuations equal to 15÷20 million –1.

Rice. 2.8. Time course of CO 2 concentration in the atmosphere at Teriberka station (Kola Peninsula) for the observation period since 1988. Dots and lines show single measurements ( 1 ), smoothed seasonal variation ( 2 ) and long-term trend ( 3 ) CO 2 CO 2 concentration, ppm (OD, 2008)

The mechanism of the greenhouse effect is explained by the difference in the absorption capacity of the atmosphere for solar radiation coming to the Earth and radiation leaving the Earth. The Earth receives radiation from the Sun in a wide band of the spectrum with an average wavelength of about 0.5 microns, and this short-wave radiation almost passes through the atmosphere. The Earth gives off the received energy almost like a completely black body in the long-wave, infrared range, with an average wavelength of about 10 microns. In this range, many gases (CO 2, CH 4, H 2 O, etc.) have numerous absorption bands; these gases absorb radiation, as a result they release heat and, for the most part, heat the atmosphere. Carbon dioxide intensively absorbs radiation coming from the Earth in the range of 12–18 microns and is one of the main factors providing the greenhouse effect (Perevedentsev Yu.P., 2009).

Modern climate warming. The fact that the modern climate is changing is recognized by everyone, since both instrumental measurements and natural indicators indicate one thing: in recent decades there has been a significant warming of the planet’s climate. IN last century(1906–2005), a ground-based meteorological network recorded a significant increase in the average global temperature at the Earth's surface by 0.74 °C. Disagreements arise when discussing the causes of warming. In the Fourth Assessment Report, IPCC experts (2007) draw conclusions regarding the causes of the observed warming: the likelihood that climate change over the past 50 years occurred without external (anthropogenic) influence is assessed as extremely low (<5%). С высокой степенью вероятности (>90%) states that the changes observed over the past 50 years are caused not only by natural, but also by external influences. With >90% confidence, the report states that rising concentrations of anthropogenic greenhouse gases are responsible for most of the global warming since the mid-20th century.

There are other views on the causes of warming - internal factor, natural variability that causes temperature fluctuations, both in the direction of warming and cooling. Thus, in the work (Datsenko N.M., Monin A.S., Sonechkin D.M., 2004), supporters of this concept indicate that the period of the most intense increase in global temperature of the 20th century (90s) falls on the ascending branch of the 60s. summer fluctuations, identified by them in the indices characterizing the thermal and circulation state of the atmosphere. At the same time, it is suggested that modern climate fluctuations are a consequence of nonlinear responses of the climate system to quasi-periodic external influences (cycles of lunisolar tides and solar activity, cycles of rotation of the largest planets solar system around a common center, etc.) (Perevedentsev Yu.P., 2009).

For the first time, the growth of industrial CO 2 emissions into the atmosphere was established by H.E. Suess in the early 50s of the XX century. From changes in the carbon ratio in tree rings, Suess concluded that atmospheric carbon dioxide already from the second half of the 19th century century is replenished with CO 2 emissions from the combustion of fossil fuels. He discovered that the ratio of radioactive C 14, constantly formed in the atmosphere due to the action of cosmic particles, to stable C 12 has been decreasing over the past hundred years as a result of the “dilution” of atmospheric CO 2 by the flow of CO 2 from fossil fuels, which contain virtually no C (half-life C 14 is equal to 5730 years). Thus, an increase in industrial CO 2 emissions into the atmosphere was detected based on measurements in tree rings. It was only in 1958 that the recording of atmospheric CO 2 concentrations began at the Mauna Loa station in the Pacific Ocean.

Rice. 4.7. Time course of carbon dioxide concentration ( A), methane ( b) and nitrous oxide ( V) in the atmosphere and their changes over the past 10,000 years (large panel) and since 1750 (smaller panel inserted into it). Results of measurements in ice deposits (symbols of different colors and configurations) from various researchers and measurements in the atmosphere (red curve). The rating scale corresponding to the measured concentrations of radiation forcing is shown in the large panels on the right side (Assessment report on climate change and its consequences in the territory Russian Federation(OD), 2008)

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

Atmospheric composition

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

Layers of the atmosphere

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

Airless magnetosphere. This is where most of the Earth's satellites fly outside the Earth's atmosphere.
Exosphere (450-500 km from the surface). Almost no gases. Some weather satellites fly in the exosphere. The thermosphere (80-450 km) is characterized high temperatures, reaching 1700°C in the upper layer.
Mesosphere (50-80 km). In this area, the temperature drops as altitude increases. This is where most meteorites (fragments of space rocks) that enter the atmosphere burn up.
Stratosphere (15-50 km). Contains ozone layer, i.e. a layer of ozone that absorbs ultraviolet radiation from the Sun. This causes temperatures near the Earth's surface to rise. Jet planes usually fly here because Visibility in this layer is very good and there is almost no interference caused by weather conditions.
Troposphere. The height varies from 8 to 15 km from the earth's surface. It is here that the planet's weather is formed, since in This layer contains the most water vapor, dust and winds. The temperature decreases with distance from the earth's surface.

Atmosphere pressure

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

Movement of air masses in the atmosphere

And the pressures force the lower layers of the atmosphere to mix. This is how winds arise, blowing from areas of high pressure to areas of low pressure. In many regions, local winds also arise due to differences in temperature between land and sea. Mountains also have a significant influence on the direction of winds.

Greenhouse effect

Carbon dioxide and other gases that make up the earth's atmosphere trap heat from the sun. This process is commonly called the greenhouse effect, since it is in many ways reminiscent of the circulation of heat in greenhouses. The greenhouse effect causes global warming on the planet. In areas of high pressure - anticyclones - clear sunny weather sets in. Areas of low pressure - cyclones - usually experience unstable weather. Heat and light entering the atmosphere. Gases trap heat reflected from the earth's surface, thereby causing an increase in temperature on Earth.

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

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

A hole in the ozone layer over Antarctica is clearly visible in this satellite photograph. The size of the hole varies, but scientists believe that it is constantly growing. Efforts are being made to reduce the level of exhaust gases in the atmosphere. Air pollution should be reduced and smokeless fuels used in cities. Smog causes eye irritation and suffocation for many people.

The emergence and evolution of the Earth's atmosphere

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

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

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

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

During the Archean and a significant part of the Proterozoic, almost all the oxygen arising in both abiogenic and biogenic ways was mainly spent on the oxidation of iron and sulfur. By the end of the Proterozoic, all metallic divalent iron located on the earth's surface either oxidized or moved into the earth's core. This caused the partial pressure of oxygen in the early Proterozoic atmosphere to change.

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

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

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

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

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

Thus, the gas composition of the atmosphere not only provided living space for organisms, but also determined the characteristics of their life activity and contributed to settlement and evolution. Emerging disruptions in the distribution of the gas composition of the atmosphere favorable for organisms, both due to cosmic and planetary reasons, led to mass extinctions of the organic world, which repeatedly occurred during the Cryptozoic and at certain boundaries of Phanerozoic history.

Ethnospheric functions of the atmosphere

The Earth's atmosphere provides the necessary substances, energy and determines the direction and speed of metabolic processes. The gas composition of the modern atmosphere is optimal for the existence and development of life. Being the area where weather and climate are formed, the atmosphere must create comfortable conditions for the life of people, animals and vegetation. Deviations in one direction or another in the quality of atmospheric air and weather conditions create extreme conditions for the life of flora and fauna, including humans.

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

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

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

IN last years A large number of works by natural scientists have been published, to one degree or another relating to various aspects of activity and the influence of the atmosphere on earthly processes, which indicates the intensification of interdisciplinary interactions in modern natural science. At the same time, the integrating role of certain of its directions is manifested, among which we should note the functional-ecological direction in geoecology.

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

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

The role of the atmosphere in natural processes

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

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

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

The action and direction of natural processes, as well as life and activity on Earth, are determined by solar radiation. It provides 99.98% of the heat supplied to earth's surface. Every year this amounts to 134 * 10 19 kcal. This amount of heat can be obtained by burning 200 billion tons. coal. The reserves of hydrogen that create this flow of thermonuclear energy in the mass of the Sun will last for at least another 10 billion years, i.e., for a period twice as long as the existence of our planet and itself.

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

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

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

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

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

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

Water vapor, like carbon dioxide, enhances the greenhouse effect. In the clouds and fogs that arise in the atmosphere, peculiar physical and chemical processes occur.

The primary source of water vapor into the atmosphere is the surface of the World Ocean. A layer of water with a thickness of 95 to 110 cm evaporates from it annually. Part of the moisture returns to the ocean after condensation, and the other is directed by air currents towards the continents. In areas of variable humid climate, precipitation moistens the soil, and in humid climates it creates groundwater reserves. Thus, the atmosphere is an accumulator of humidity and a reservoir of precipitation. and fogs that form in the atmosphere provide moisture to the soil cover and thereby play a decisive role in the development of flora and fauna.

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

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

Atmospheric pressure is of fundamental importance for the formation of wind, which, being a relief-forming factor, has a strong impact on the animal and plant world.

Wind can suppress plant growth and at the same time promote seed transfer. The role of wind in shaping weather and climate conditions is great. It also acts as a regulator of sea currents. Wind, as one of the exogenous factors, contributes to the erosion and deflation of weathered material over long distances.

Ecological and geological role of atmospheric processes

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

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

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

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

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

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

Tornadoes lift and move cars, houses, carriages, and bridges. Particularly destructive tornadoes are observed in the United States. Every year there are from 450 to 1500 tornadoes with an average death toll of about 100 people. Tornadoes are fast-acting catastrophic atmospheric processes. They are formed in just 20-30 minutes, and their lifetime is 30 minutes. Therefore, it is almost impossible to predict the time and place of tornadoes.

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

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

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

Thunderstorms usually last less than an hour. Particularly dangerous are intense downpours, hail, lightning strikes, gusts of wind, and vertical air currents. The hail hazard is determined by the size of the hailstones. In the North Caucasus, the mass of hailstones once reached 0.5 kg, and in India, hailstones weighing 7 kg were recorded. The most urban-dangerous areas in our country are located in the North Caucasus. In July 1992, hail damaged the airport " Mineral water» 18 aircraft.

Dangerous atmospheric phenomena include lightning. They kill people, livestock, cause fires, and damage the power grid. About 10,000 people die from thunderstorms and their consequences every year around the world. Moreover, in some areas of Africa, France and the USA, the number of victims from lightning is greater than from other natural phenomena. The annual economic damage from thunderstorms in the United States is at least $700 million.

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

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

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

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

Anthropogenic atmospheric changes

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

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

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

As a result of pollution, the transparency of the atmosphere changes, causing aerosols, smog and acid rain.

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

Aerosols began to form from the moment our planet appeared and influenced natural conditions. However, their quantity and actions, balanced with the general cycle of substances in nature, did not cause profound environmental changes. Anthropogenic factors of their formation have shifted this balance towards significant biosphere overloads. This feature has been especially evident since humanity began to use specially created aerosols both in the form of toxic substances and for plant protection.

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

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

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

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

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

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

NO 2 → NO + O

Then ozone synthesis occurs:

O + O 2 + M → O 3 + M

NO + O → NO 2

Photodissociation processes are accompanied by a yellow-green glow.

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

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

The presence of carcinogenic substances in smog leads to breathing problems, irritation of mucous membranes, circulatory disorders, asthmatic suffocation and often death. Smog is especially dangerous for young children.

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

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

Acid rain has an aggressive effect on the Earth's vegetation, on industrial and residential buildings and contributes to a significant acceleration of the weathering of exposed rocks. Increased acidity prevents the self-regulation of neutralization of soils in which nutrients dissolve. In turn, this leads to a sharp decrease in yield and causes degradation of the vegetation cover. Soil acidity promotes the release of bound heavy soils, which are gradually absorbed by plants, causing serious tissue damage and penetrating the human food chain.

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

As a result of acid rain, forests are at risk of destruction Western Europe, Baltic states, Karelia, Urals, Siberia and Canada.

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