Layers of the atmosphere and their boundaries. Atmosphere and the world of atmospheric phenomena

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. Temperatures different layers noticeably different from each other.

Airless magnetosphere. Most of the Earth's satellites fly here 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 by 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.

Atmospheric 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 usually called 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.

In the stratosphere there is a special ozone layer. Ozone retains most ultraviolet radiation The sun, protecting the Earth and all life on it from it. Scientists have found that the cause of the destruction of the ozone layer 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 of the composition and structure of the early atmosphere has changed somewhat. 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 during 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 concentration of oxygen 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 advent of organisms, the process of fixing atmospheric nitrogen into organic matter and its burial in marine sediments. 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.

So gas atmospheric composition not only provided organisms with living space, but also determined the characteristics of their life activity, 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 necessary substance, energy and determines the direction and speed of metabolic processes. The gas composition of the modern atmosphere is optimal for the existence and development of life. 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 quality 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 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 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 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 the energy of 500 thousand atomic bombs dropped on Hiroshima and Nagasaki in just one day. 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 recent years, a large number of works by natural scientists have been published, in one way or another dealing with 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 for the 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. In the upper part of the troposphere and lower part 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, are various shapes economic activity person. 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, depending on the quantity, nature and frequency atmospheric precipitation, the frequency and strength of the winds and especially the air temperature determine the weathering and intensity of destruction of rocks, the transfer and accumulation of clastic material. Atmosphere is a central component 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 solar radiation through the atmosphere and prevent the Earth's thermal radiation from escaping 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 the earth's surface. Every year this amounts to 134*1019 kcal. This amount of heat can be obtained by burning 200 billion tons of 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, total quantity 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 day summer day usually colder than on a clear day, 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 the regions variable humid climate precipitation moistens the soil, and in wet areas 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 general circulation atmosphere. In addition, they are sources of catastrophic atmospheric phenomena.

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

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, causing the decomposition of ozone and the generation of “pearl” clouds consisting of water vapor. Global change reflectivity, as well as changes in the gas composition of the atmosphere, mainly greenhouse gases, are the cause of climate change.

Uneven heating, which causes differences in atmospheric pressure over different parts of the earth's surface, leads to atmospheric circulation, which is 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.

Large negative environmental impact from catastrophic consequences are caused by squalls and tornadoes (tornadoes) - atmospheric vortices that arise in the warm season on powerful atmospheric fronts, with speeds of up to 100 m/s. Squalls are horizontal whirlwinds with hurricane wind speeds (up to 60-80 m/s). They are often accompanied by heavy 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 sparsity and high speed rotation, the tornado travels up to several hundred kilometers, drawing in dust, water from reservoirs and various objects. Powerful tornadoes are accompanied by thunderstorms, rain and have great destructive power.

Tornadoes rarely occur in subpolar or equatorial regions, where it is constantly cold or hot. 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 rising currents of moist warm air and with high speed They rotate clockwise in the southern hemisphere and counterclockwise in the northern hemisphere. 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 the temperature rises very quickly humid air. On the border of tropical and subtropical zones thunderstorms occur 90-100 days a year, in the temperate zone 10-30 days. In our country greatest number 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 " Mineralnye Vody» 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 natural environment through processes such as soil salinization, hot 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 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, the greatest impact on the atmosphere comes from two sources: 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 with inhaled air into respiratory organs animals and humans, have an aggressive effect on 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, in which they are capable of being 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 the water vapor present in it forms sulfuric and nitric acids.

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. In the modern era, the pH value of rainwater is 5.6, although in the recent past it was neutral. A decrease in pH value by one corresponds to a tenfold increase in acidity and, therefore, at present, 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, 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 Earth's atmosphere is the gaseous envelope of our planet. Its lower boundary is at the level earth's crust and hydrosphere, and the upper one goes into the near-Earth region of outer space. The atmosphere contains about 78% nitrogen, 20% oxygen, up to 1% argon, carbon dioxide, hydrogen, helium, neon and some other gases.

This earth's shell is characterized by clearly defined layering. The layers of the atmosphere are determined by the vertical distribution of temperature and the different densities of gases at different levels. There are such layers of the Earth's atmosphere: troposphere, stratosphere, mesosphere, thermosphere, exosphere. The ionosphere is separated separately.

Up to 80% of the total mass of the atmosphere is the troposphere - the lower ground layer of the atmosphere. The troposphere in the polar zones is located at a level of up to 8-10 km above the earth's surface, in the tropical zone - up to a maximum of 16-18 km. Between the troposphere and the overlying layer of the stratosphere there is a tropopause - a transition layer. In the troposphere, the temperature decreases as altitude increases, and similarly, atmospheric pressure decreases with altitude. The average temperature gradient in the troposphere is 0.6°C per 100 m. The temperature at different levels of this shell is determined by the characteristics of the absorption of solar radiation and the efficiency of convection. Almost all human activity takes place in the troposphere. The most high mountains do not go beyond the troposphere, only air transport can cross the upper boundary of this shell at a low altitude and be in the stratosphere. A large proportion of water vapor is found in the troposphere, which is responsible for the formation of almost all clouds. Also, almost all aerosols (dust, smoke, etc.) formed on the earth’s surface are concentrated in the troposphere. In the boundary lower layer of the troposphere, daily fluctuations in temperature and air humidity are pronounced, and wind speed is usually reduced (it increases with increasing altitude). In the troposphere, there is a variable division of the air thickness into air masses in the horizontal direction, differing in a number of characteristics depending on the zone and area of ​​their formation. At atmospheric fronts - the boundaries between air masses - cyclones and anticyclones form, which determine the weather in a certain area for a specific period of time.

The stratosphere is the layer of atmosphere between the troposphere and mesosphere. The limits of this layer range from 8-16 km to 50-55 km above the Earth's surface. In the stratosphere, the gas composition of the air is approximately the same as in the troposphere. A distinctive feature is a decrease in water vapor concentration and an increase in ozone content. The ozone layer of the atmosphere protects the biosphere from aggressive influences ultraviolet light, is located at a level of 20 to 30 km. In the stratosphere, temperature increases with altitude, and temperature values ​​are determined by solar radiation, and not by convection (movements of air masses), as in the troposphere. The heating of the air in the stratosphere is due to the absorption of ultraviolet radiation by ozone.

Above the stratosphere the mesosphere extends to a level of 80 km. This layer of the atmosphere is characterized by the fact that the temperature decreases as the altitude increases from 0 ° C to - 90 ° C. This is the coldest region of the atmosphere.

Above the mesosphere is the thermosphere up to a level of 500 km. From the border with the mesosphere to the exosphere, the temperature varies from approximately 200 K to 2000 K. Up to the level of 500 km, the air density decreases several hundred thousand times. The relative composition of the atmospheric components of the thermosphere is similar to the surface layer of the troposphere, but with increasing altitude, more oxygen becomes atomic. A certain proportion of molecules and atoms of the thermosphere are in an ionized state and are distributed in several layers; they are united by the concept of the ionosphere. The characteristics of the thermosphere vary over a wide range depending on geographic latitude, the amount of solar radiation, time of year and day.

The upper layer of the atmosphere is the exosphere. This is the thinnest layer of the atmosphere. In the exosphere, the mean free path of particles is so enormous that particles can freely escape into interplanetary space. The mass of the exosphere is one ten-millionth of the total mass of the atmosphere. The lower boundary of the exosphere is the level of 450-800 km, and the upper boundary is considered to be the region where the concentration of particles is the same as in outer space - several thousand kilometers from the Earth's surface. The exosphere consists of plasma - ionized gas. Also in the exosphere are the radiation belts of our planet.

Video presentation - layers of the Earth's atmosphere:

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The Earth's atmosphere is the gaseous envelope of our planet. By the way, almost all celestial bodies have similar shells, from the planets of the solar system to large asteroids. depends on many factors - the size of its speed, mass and many other parameters. But only the shell of our planet contains the components that allow us to live.

Earth's atmosphere: brief history emergence

It is believed that at the beginning of its existence our planet had no gas shell at all. But the young, newly formed celestial body was constantly evolving. The Earth's primary atmosphere was formed as a result of constant volcanic eruptions. This is how, over many thousands of years, a shell of water vapor, nitrogen, carbon and other elements (except oxygen) formed around the Earth.

Since the amount of moisture in the atmosphere is limited, its excess turned into precipitation - this is how seas, oceans and other bodies of water were formed. IN aquatic environment The first organisms that populated the planet appeared and developed. Most of them belonged to plant organisms that produce oxygen through photosynthesis. Thus, the Earth's atmosphere began to fill with this vital gas. And as a result of the accumulation of oxygen, the ozone layer was formed, which protected the planet from the harmful effects of ultraviolet radiation. It is these factors that created all the conditions for our existence.

The structure of the Earth's atmosphere

As you know, the gas shell of our planet consists of several layers - the troposphere, stratosphere, mesosphere, thermosphere. It is impossible to draw clear boundaries between these layers - it all depends on the time of year and the latitude of the planet.

The troposphere is the lower part of the gas shell, the height of which averages from 10 to 15 kilometers. This is where most of the moisture is concentrated. By the way, this is where all the moisture is located and clouds form. Due to the oxygen content, the troposphere supports the life activity of all organisms. In addition, it is crucial in shaping the weather and climatic features of the area - not only clouds, but also winds are formed here. Temperature drops with altitude.

Stratosphere - starts from the troposphere and ends at an altitude of 50 to 55 kilometers. Here the temperature increases with altitude. This part of the atmosphere contains virtually no water vapor, but does have an ozone layer. Sometimes here you can notice the formation of “pearl” clouds, which can only be seen at night - they are believed to be represented by highly condensed water drops.

The mesosphere stretches up to 80 kilometers up. In this layer you can notice a sharp drop in temperature as you move up. Turbulence is also highly developed here. By the way, so-called “noctilucent clouds” are formed in the mesosphere, which consist of small ice crystals - they can only be seen at night. It is interesting that there is practically no air at the upper boundary of the mesosphere - it is 200 times less than near the earth's surface.

The thermosphere is the upper layer of the earth's gas shell, in which it is customary to distinguish between the ionosphere and the exosphere. Interestingly, the temperature here rises very sharply with altitude - at an altitude of 800 kilometers from the earth's surface it is more than 1000 degrees Celsius. The ionosphere is characterized by highly diluted air and a huge content of active ions. As for the exosphere, this part of the atmosphere smoothly passes into interplanetary space. It is worth noting that the thermosphere does not contain air.

It can be noted that the Earth's atmosphere is a very important part of our planet, which remains a decisive factor in the emergence of life. It ensures life activity, maintains the existence of the hydrosphere (the watery shell of the planet) and protects from ultraviolet radiation.

The atmosphere extends upward for many hundreds of kilometers. Its upper limit, at an altitude of about 2000-3000 km, to a certain extent, it is conditional, since the gases that make it up, gradually becoming rarefied, pass into cosmic space. Changes with altitude chemical composition atmosphere, pressure, density, temperature and other physical properties. As mentioned earlier, the chemical composition of air up to a height of 100 km does not change significantly. Slightly higher, the atmosphere also consists mainly of nitrogen and oxygen. But at altitudes 100-110 km, Under the influence of ultraviolet radiation from the sun, oxygen molecules are split into atoms and atomic oxygen appears. Above 110-120 km almost all oxygen becomes atomic. It is assumed that above 400-500 km The gases that make up the atmosphere are also in an atomic state.

Air pressure and density decrease rapidly with altitude. Although the atmosphere extends upward for hundreds of kilometers, the bulk of it is located in a rather thin layer adjacent to the surface of the earth in its lowest parts. So, in the layer between sea level and heights 5-6 km half the mass of the atmosphere is concentrated in layer 0-16 km-90%, and in the layer 0-30 km- 99%. The same rapid decrease in air mass occurs above 30 km. If weight 1 m 3 air at the surface of the earth is 1033 g, then at an altitude of 20 km it is equal to 43 g, and at a height of 40 km only 4 years

At an altitude of 300-400 km and above, the air is so rarefied that during the day its density changes many times. Research has shown that this change in density is related to the position of the Sun. The highest air density is around noon, the lowest at night. This is partly explained by the fact that the upper layers of the atmosphere react to changes electromagnetic radiation Sun.

Air temperature also varies unequally with altitude. According to the nature of temperature changes with altitude, the atmosphere is divided into several spheres, between which there are transition layers, so-called pauses, where the temperature changes little with altitude.

Here are the names and main characteristics of the spheres and transition layers.

Let us present basic data on the physical properties of these spheres.

Troposphere. The physical properties of the troposphere are largely determined by the influence of the earth's surface, which is its lower boundary. The highest altitude of the troposphere is observed in the equatorial and tropical zones. Here it reaches 16-18 km and is subject to relatively little daily and seasonal changes. Over the polar and adjacent regions, the upper boundary of the troposphere lies on average at a level of 8-10 km. In middle latitudes it ranges from 6-8 to 14-16 km.

The vertical thickness of the troposphere depends significantly on the nature of atmospheric processes. Often during the day the upper boundary of the troposphere above a given point or area falls or rises by several kilometers. This is mainly due to changes in air temperature.

More than 4/5 of the mass of the earth's atmosphere and almost all the water vapor contained in it are concentrated in the troposphere. In addition, from the surface of the earth to the upper boundary of the troposphere, the temperature decreases by an average of 0.6° for every 100 m, or 6° per 1 km raising . This is explained by the fact that the air in the troposphere is heated and cooled primarily by the earth's surface.

In accordance with the influx of solar energy, the temperature decreases from the equator to the poles. So, average temperature air near the surface of the earth at the equator reaches +26°, over the polar regions in winter -34°, -36°, and in summer about 0°. Thus, the temperature difference between the equator and the pole in winter is 60°, and in summer only 26°. True, such low temperatures in the Arctic in winter are observed only near the surface of the earth due to cooling of the air above the icy expanses.

In winter in Central Antarctica, surface air temperature ice sheet even lower. At Vostok station in August 1960, the lowest temperature on the globe was recorded -88.3°, and most often in Central Antarctica it is -45°, -50°.

With height, the temperature difference between the equator and the pole decreases. For example, at an altitude of 5 km at the equator the temperature reaches -2°, -4°, and at the same altitude in the Central Arctic -37°, -39° in winter and -19°, -20° in summer; therefore, the temperature difference in winter is 35-36°, and in summer 16-17°. In the southern hemisphere these differences are somewhat larger.

The energy of atmospheric circulation can be determined by equator-pole temperature contracts. Since the magnitude of temperature contrasts is greater in winter, atmospheric processes occur more intensely than in summer. This also explains the fact that the prevailing westerly winds in the troposphere in winter have higher speeds than in summer. In this case, the wind speed, as a rule, increases with height, reaching a maximum at the upper boundary of the troposphere. Horizontal transfer is accompanied by vertical movements of air and turbulent (disordered) movement. Due to the rise and fall of large volumes of air, clouds form and dissipate, precipitation occurs and ceases. The transition layer between the troposphere and the overlying sphere is tropopause. Above it lies the stratosphere.

Stratosphere extends from heights 8-17 to 50-55 km. It was discovered at the beginning of our century. In terms of physical properties, the stratosphere differs sharply from the troposphere in that the air temperature here, as a rule, increases by an average of 1 - 2 ° per kilometer of elevation and at the upper boundary, at an altitude of 50-55 km, even becomes positive. The increase in temperature in this area is caused by the presence of ozone (O 3), which is formed under the influence of ultraviolet radiation from the Sun. The ozone layer occupies almost the entire stratosphere. The stratosphere is very poor in water vapor. There are no violent processes of cloud formation and no precipitation.

More recently, it was assumed that the stratosphere is a relatively calm environment where air mixing does not occur, as in the troposphere. Therefore, it was believed that gases in the stratosphere are divided into layers in accordance with their specific gravities. Hence the name stratosphere (“stratus” - layered). It was also believed that the temperature in the stratosphere is formed under the influence of radiative equilibrium, that is, when absorbed and reflected solar radiation is equal.

New data obtained from radiosondes and weather rockets have shown that the stratosphere, like the upper troposphere, experiences intense air circulation with large changes in temperature and wind. Here, as in the troposphere, the air experiences significant vertical movements and turbulent movements with strong horizontal air currents. All this is the result of a non-uniform temperature distribution.

The transition layer between the stratosphere and the overlying sphere is stratopause. However, before moving on to the characteristics of higher layers of the atmosphere, let us become familiar with the so-called ozonosphere, the boundaries of which approximately correspond to the boundaries of the stratosphere.

Ozone in the atmosphere. Ozone plays a large role in creating temperature regimes and air currents in the stratosphere. Ozone (O 3) is felt by us after a thunderstorm when inhaled clean air with a pleasant aftertaste. However, here we will not talk about this ozone formed after a thunderstorm, but about the ozone contained in the 10-60 layer km with a maximum at an altitude of 22-25 km. Ozone is formed under the influence of ultraviolet rays from the Sun and, although its total amount is small, plays an important role in the atmosphere. Ozone has the ability to absorb ultraviolet radiation from the Sun and thereby protects flora and fauna from its destructive effects. Even that insignificant share ultraviolet rays, which reaches the surface of the earth, severely burns the body when a person is overly keen on sunbathing.

The amount of ozone varies over different parts of the Earth. There is more ozone in high latitudes, less in middle and low latitudes, and this amount varies depending on the changing seasons of the year. There is more ozone in spring, less in autumn. In addition, non-periodic fluctuations occur depending on the horizontal and vertical circulation of the atmosphere. Many atmospheric processes are closely related to ozone content, since it has a direct impact on the temperature field.

In winter, under polar night conditions, at high latitudes, radiation and cooling of the air occurs in the ozone layer. As a result, in the stratosphere of high latitudes (in the Arctic and Antarctic) in winter, a cold region is formed, a stratospheric cyclonic vortex with large horizontal temperature and pressure gradients, causing westerly winds over the mid-latitudes of the globe.

In summer, under polar day conditions, at high latitudes, the ozone layer absorbs solar heat and warms the air. As a result of an increase in temperature in the stratosphere at high latitudes, a heat region and a stratospheric anticyclonic vortex are formed. Therefore, above the middle latitudes of the globe above 20 km In summer, easterly winds predominate in the stratosphere.

Mesosphere. Observations using meteorological rockets and other methods have established that the general increase in temperature observed in the stratosphere ends at altitudes of 50-55 km. Above this layer, the temperature decreases again and at the upper boundary of the mesosphere (about 80 km) reaches -75°, -90°. Then the temperature increases again with height.

It is interesting to note that the decrease in temperature with height, characteristic of the mesosphere, occurs differently at different latitudes and throughout the year. In low latitudes, the temperature drop occurs more slowly than in high latitudes: the average vertical temperature gradient for the mesosphere is respectively 0.23° - 0.31° per 100 m or 2.3°-3.1° per 1 km. In summer it is much larger than in winter. As the latest research in high latitudes has shown, the temperature at the upper boundary of the mesosphere in summer is several tens of degrees lower than in winter. In the upper mesosphere at an altitude of about 80 km In the mesopause layer, the decrease in temperature with height stops and its increase begins. Here, under the inversion layer at dusk or before sunrise in clear weather, shiny thin clouds are observed, illuminated by the sun below the horizon. Against the dark background of the sky they glow with a silvery-blue light. That's why these clouds are called noctilucent.

The nature of noctilucent clouds has not yet been sufficiently studied. For a long time it was believed that they consisted of volcanic dust. However, the lack optical phenomena, characteristic of real volcanic clouds, led to the rejection of this hypothesis. It was then proposed that noctilucent clouds were composed of cosmic dust. In recent years, a hypothesis has been proposed that these clouds are composed of ice crystals, like ordinary cirrus clouds. The level of noctilucent clouds is determined by the blocking layer due to temperature inversion during the transition from the mesosphere to the thermosphere at an altitude of about 80 km. Since the temperature in the sub-inversion layer reaches -80° and below, the most favorable conditions are created here for the condensation of water vapor, which enters here from the stratosphere as a result of vertical movement or by turbulent diffusion. Noctilucent clouds are usually observed in the summer, sometimes in very large numbers and for several months.

Observations of noctilucent clouds have established that in summer the winds at their level are highly variable. Wind speeds vary widely: from 50-100 to several hundred kilometers per hour.

Temperature at altitudes. A visual representation of the nature of the temperature distribution with height, between the earth's surface and altitudes of 90-100 km, in winter and summer in the northern hemisphere, is given by Figure 5. The surfaces separating the spheres are shown here with thick dashed lines. At the very bottom, the troposphere is clearly visible with a characteristic decrease in temperature with height. Above the tropopause, in the stratosphere, on the contrary, the temperature generally increases with height and at altitudes of 50-55 km reaches + 10°, -10°. Let's pay attention to an important detail. In winter, in the stratosphere of high latitudes, the temperature above the tropopause drops from -60 to -75° and only above 30 km again increases to -15°. In summer, starting from the tropopause, the temperature rises with altitude by 50 km reaches + 10°. Above the stratopause, the temperature decreases again with height, and at a level of 80 km it does not exceed -70°, -90°.

From Figure 5 it follows that in the layer 10-40 km The air temperature in winter and summer at high latitudes is sharply different. In winter, under polar night conditions, the temperature here reaches -60°, -75°, and in summer a minimum of -45° is near the tropopause. Above the tropopause, the temperature increases at altitudes of 30-35 km is only -30°, -20°, which is caused by the heating of the air in the ozone layer under polar day conditions. It also follows from the figure that even in the same season and at the same level, the temperature is not the same. Their difference between different latitudes exceeds 20-30°. In this case, the heterogeneity is especially significant in the layer low temperatures (18-30 km) and in the layer of maximum temperatures (50-60 km) in the stratosphere, as well as in the layer of low temperatures in the upper mesosphere (75-85km).

The average temperatures shown in Figure 5 are obtained from observational data in the northern hemisphere, however, judging by the available information, they can also be attributed to the southern hemisphere. Some differences exist mainly at high latitudes. Over Antarctica in winter, the air temperature in the troposphere and lower stratosphere is noticeably lower than over the Central Arctic.

Winds at heights. The seasonal distribution of temperature is determined by a rather complex system of air currents in the stratosphere and mesosphere.

Figure 6 shows a vertical section of the wind field in the atmosphere between the earth's surface and a height of 90 km in winter and summer over the northern hemisphere. The isolines depict the average speeds of the prevailing wind (in m/sec). It follows from the figure that the wind regime in the stratosphere in winter and summer is sharply different. In winter, both the troposphere and stratosphere are dominated by westerly winds with maximum speeds of about

100 m/sec at an altitude of 60-65 km. In summer, westerly winds prevail only up to heights of 18-20 km. Higher up they become eastern, with maximum speeds up to 70 m/sec at an altitude of 55-60km.

In summer, above the mesosphere, the winds become westerly, and in winter - eastern.

Thermosphere. Above the mesosphere is the thermosphere, which is characterized by an increase in temperature With height. According to the data obtained, mainly with the help of rockets, it was established that in the thermosphere already at a level of 150 km air temperature reaches 220-240°, and at 200 km more than 500°. Above the temperature continues to rise and at the level of 500-600 km exceeds 1500°. Based on data obtained from the launches of artificial Earth satellites, it was found that in the upper thermosphere the temperature reaches about 2000° and fluctuates significantly during the day. The question arises as to how to explain such high temperatures in the high layers of the atmosphere. Recall that the temperature of a gas is a measure of the average speed of movement of molecules. In the lower, densest part of the atmosphere, the molecules of the gases that make up the air often collide with each other when moving and instantly transfer kinetic energy to each other. Therefore, the kinetic energy in a dense medium is on average the same. In high layers, where the air density is very low, collisions between molecules located at large distances occur less frequently. When energy is absorbed, the speed of molecules changes greatly between collisions; in addition, molecules of lighter gases move at higher speeds than molecules of heavy gases. As a result, the temperature of the gases may be different.

In rarefied gases there are relatively few molecules of very small sizes (light gases). If they move at high speeds, then the temperature in a given volume of air will be high. In the thermosphere, every cubic centimeter of air contains tens and hundreds of thousands of molecules of various gases, while at the surface of the earth there are about hundreds of millions of billions of them. Therefore, excessively high temperatures in the high layers of the atmosphere, showing the speed of movement of molecules in this very loose environment, cannot cause even slight heating of the body located here. Just as a person does not feel high temperature under the dazzling light of electric lamps, although the filaments in a rarefied environment instantly heat up to several thousand degrees.

In the lower thermosphere and mesosphere, the main part of meteor showers burns up before reaching the earth's surface.

Available information about atmospheric layers above 60-80 km are still insufficient for final conclusions about the structure, regime and processes developing in them. However, it is known that in the upper mesosphere and lower thermosphere the temperature regime is created as a result of the transformation of molecular oxygen (O 2) into atomic oxygen (O), which occurs under the influence of ultraviolet solar radiation. In the thermosphere, the temperature regime is greatly influenced by corpuscular, x-ray and. ultraviolet radiation from the Sun. Here, even during the day, there are sharp changes in temperature and wind.

Ionization of the atmosphere. Most interesting feature atmosphere above 60-80 km is her ionization, i.e., the process of formation of a huge number of electrically charged particles - ions. Since the ionization of gases is characteristic of the lower thermosphere, it is also called the ionosphere.

Gases in the ionosphere are mostly in an atomic state. Under the influence of ultraviolet and corpuscular radiation from the Sun, which have high energy, the process of splitting off electrons from neutral atoms and air molecules occurs. Such atoms and molecules that have lost one or more electrons become positively charged, and the free electron can rejoin a neutral atom or molecule and endow it with its negative charge. Such positively and negatively charged atoms and molecules are called ions, and gases - ionized, i.e., having received an electric charge. At higher concentrations of ions, gases become electrically conductive.

The ionization process occurs most intensively in thick layers limited by heights of 60-80 and 220-400 km. In these layers there are optimal conditions for ionization. Here, the air density is noticeably greater than in the upper atmosphere, and the supply of ultraviolet and corpuscular radiation from the Sun is sufficient for the ionization process.

The discovery of the ionosphere is one of the important and brilliant achievements of science. After all distinctive feature The ionosphere is its influence on the propagation of radio waves. In the ionized layers, radio waves are reflected, and therefore long-distance radio communication becomes possible. Charged atoms-ions reflect short radio waves, and they return to the earth's surface again, but at a considerable distance from the place of radio transmission. Obviously, short radio waves make this path several times, and thus long-distance radio communication is ensured. If it were not for the ionosphere, then it would be necessary to build expensive radio relay lines to transmit radio signals over long distances.

However, it is known that sometimes radio communications on short waves are disrupted. This occurs as a result of chromospheric flares on the Sun, due to which the ultraviolet radiation of the Sun sharply increases, leading to strong disturbances of the ionosphere and the Earth's magnetic field - magnetic storms. During magnetic storms, radio communications are disrupted, since the movement of charged particles depends on the magnetic field. During magnetic storms, the ionosphere reflects radio waves worse or transmits them into space. Mainly with the change solar activity, accompanied by an increase in ultraviolet radiation, the electron density of the ionosphere and the absorption of radio waves during the daytime increase, leading to disruption of radio communications on short waves.

According to new research, in a powerful ionized layer there are zones where the concentration of free electrons reaches a slightly higher concentration than in neighboring layers. Four such zones are known, which are located at altitudes of about 60-80, 100-120, 180-200 and 300-400 km and are designated by letters D, E, F 1 And F 2 . With increasing radiation from the Sun, charged particles (corpuscles) under the influence of the Earth's magnetic field are deflected towards high latitudes. Upon entering the atmosphere, the corpuscles increase the ionization of gases so much that they begin to glow. This is how they arise auroras- in the form of beautiful multicolored arcs that light up in the night sky mainly in the high latitudes of the Earth. Auroras are accompanied by strong magnetic storms. In such cases, auroras become visible at mid-latitudes, and in rare cases even at tropical zone. For example, the intense aurora observed on January 21-22, 1957, was visible in almost all southern regions of our country.

By photographing auroras from two points located at a distance of several tens of kilometers, the height of the auroras is determined with great accuracy. Usually auroras are located at an altitude of about 100 km, They are often found at an altitude of several hundred kilometers, and sometimes at a level of about 1000 km. Although the nature of the auroras has been clarified, there are still many unresolved questions related to this phenomenon. The reasons for the diversity of forms of auroras are still unknown.

According to the third Soviet satellite, between altitudes 200 and 1000 km During the day, positive ions of split molecular oxygen, i.e., atomic oxygen (O), predominate. Soviet scientists are exploring the ionosphere using artificial satellites of the Cosmos series. American scientists also study the ionosphere using satellites.

The surface separating the thermosphere from the exosphere experiences fluctuations depending on changes in solar activity and other factors. Vertically, these fluctuations reach 100-200 km and more.

Exosphere (scattering sphere) - the most upper part atmosphere, located above 800 km. It has been little studied. According to observational data and theoretical calculations, the temperature in the exosphere increases with altitude, presumably up to 2000°. Unlike the lower ionosphere, in the exosphere the gases are so rarefied that their particles, moving at enormous speeds, almost never meet each other.

Until relatively recently, it was assumed that the conventional boundary of the atmosphere is at an altitude of about 1000 km. However, based on the braking of artificial Earth satellites, it has been established that at altitudes of 700-800 km at 1 cm 3 contains up to 160 thousand positive ions of atomic oxygen and nitrogen. This suggests that the charged layers of the atmosphere extend into space over a much greater distance.

At high temperatures on conditional border atmosphere, gas particle velocities reach approximately 12 km/sec. At these speeds, gases gradually escape from the region of gravity into interplanetary space. This happens over a long period of time. For example, particles of hydrogen and helium are removed into interplanetary space over several years.

In the study of high layers of the atmosphere, rich data was obtained both from satellites of the Cosmos and Electron series, and from geophysical rockets and space stations Mars-1, Luna-4, etc. Direct observations of astronauts also turned out to be valuable. Thus, according to photographs taken in space by V. Nikolaeva-Tereshkova, it was established that at an altitude of 19 km There is a dust layer from the Earth. This was confirmed by the data received by the crew spaceship"Sunrise". Apparently, there is a close connection between the dust layer and the so-called pearly clouds, sometimes observed at altitudes of about 20-30km.

From the atmosphere to outer space. Previous assumptions that beyond the Earth's atmosphere, in the interplanetary

space, gases are very rarefied and the concentration of particles does not exceed several units in 1 cm 3, didn't come true. Research has shown that near-Earth space is filled with charged particles. On this basis, a hypothesis was put forward about the existence of zones around the Earth with a noticeably increased content of charged particles, i.e. radiation belts- internal and external. New data helped clarify things. It turned out that there are also charged particles between the inner and outer radiation belts. Their number varies depending on geomagnetic and solar activity. Thus, according to the new assumption, instead of radiation belts, there are radiation zones without clearly defined boundaries. The boundaries of radiation zones change depending on solar activity. When it intensifies, that is, when spots and jets of gas appear on the Sun, ejected over hundreds of thousands of kilometers, the flow of cosmic particles increases, which feed the Earth's radiation zones.

Radiation zones are dangerous for people flying on spacecraft. Therefore, before a flight into space, the state and position of radiation zones are determined, and the orbit of the spacecraft is chosen so that it passes outside areas of increased radiation. However, the high layers of the atmosphere, as well as outer space close to the Earth, have still been little explored.

The study of the high layers of the atmosphere and near-Earth space uses rich data obtained from Cosmos satellites and space stations.

The high layers of the atmosphere are the least studied. However modern methods her research allows us to hope that in the coming years people will know many details of the structure of the atmosphere at the bottom of which they live.

In conclusion, we present a schematic vertical section of the atmosphere (Fig. 7). Here, altitudes in kilometers and air pressure in millimeters are plotted vertically, and temperature is plotted horizontally. The solid curve shows the change in air temperature with height. At the corresponding altitudes, the most important phenomena observed in the atmosphere are noted, as well as maximum heights, achieved by radiosondes and other means of sensing the atmosphere.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Ozone also changes magnetic fields, atoms disintegrate into molecules, ionization occurs, new formation of gases and other chemical compounds occurs.

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

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

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

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

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

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

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

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

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

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

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