The name of the layers of the earth's atmosphere. upper layers of the atmosphere. The composition of the Earth's atmosphere

The atmosphere is the gaseous shell of our planet that rotates with the Earth. The gas in the atmosphere is called air. The atmosphere is in contact with the hydrosphere and partially covers the lithosphere. But it is difficult to determine the upper bounds. Conventionally, it is assumed that the atmosphere extends upwards for about three thousand kilometers. There it flows smoothly into the airless space.

The chemical composition of the Earth's atmosphere

The formation of the chemical composition of the atmosphere began about four billion years ago. Initially, the atmosphere consisted only of light gases - helium and hydrogen. According to scientists, the initial prerequisites for the creation of a gas shell around the Earth were volcanic eruptions, which, together with lava, emitted a huge amount of gases. Subsequently, gas exchange began with water spaces, with living organisms, with the products of their activity. The composition of the air gradually changed and in its present form was fixed several million years ago.

The main components of the atmosphere are nitrogen (about 79%) and oxygen (20%). The remaining percentage (1%) is accounted for by the following gases: argon, neon, helium, methane, carbon dioxide, hydrogen, krypton, xenon, ozone, ammonia, sulfur dioxide and nitrogen, nitrous oxide and carbon monoxide, included in this one percent.

In addition, the air contains water vapor and particulate matter (plant pollen, dust, salt crystals, aerosol impurities).

Recently, scientists have noted not a qualitative, but a quantitative change in some air ingredients. And the reason for this is the person and his activity. Only in the last 100 years, the content of carbon dioxide has increased significantly! This is fraught with many problems, the most global of which is climate change.

Formation of weather and climate

The atmosphere plays a vital role in shaping the climate and weather on Earth. A lot depends on the amount of sunlight, on the nature of the underlying surface and atmospheric circulation.

Let's look at the factors in order.

1. The atmosphere transmits the heat of the sun's rays and absorbs harmful radiation. The ancient Greeks knew that the rays of the Sun fall on different parts of the Earth at different angles. The very word "climate" in translation from ancient Greek means "slope". So, at the equator, the sun's rays fall almost vertically, because it is very hot here. The closer to the poles, the greater the angle of inclination. And the temperature is dropping.

2. Due to the uneven heating of the Earth, air currents are formed in the atmosphere. They are classified according to their size. The smallest (tens and hundreds of meters) are local winds. This is followed by monsoons and trade winds, cyclones and anticyclones, planetary frontal zones.

All these air masses are constantly moving. Some of them are quite static. For example, the trade winds that blow from the subtropics towards the equator. The movement of others is largely dependent on atmospheric pressure.

3. Atmospheric pressure is another factor influencing climate formation. This is the air pressure on the earth's surface. As you know, air masses move from an area with high atmospheric pressure towards an area where this pressure is lower.

There are 7 zones in total. The equator is a low pressure zone. Further, on both sides of the equator up to the thirtieth latitudes - an area of ​​high pressure. From 30° to 60° - again low pressure. And from 60° to the poles - a zone of high pressure. Air masses circulate between these zones. Those that go from the sea to land bring rain and bad weather, and those that blow from the continents bring clear and dry weather. In places where air currents collide, atmospheric front zones are formed, which are characterized by precipitation and inclement, windy weather.

Scientists have proven that even a person's well-being depends on atmospheric pressure. According to international standards, normal atmospheric pressure is 760 mm Hg. column at 0°C. This figure is calculated for those areas of land that are almost flush with sea level. The pressure decreases with altitude. Therefore, for example, for St. Petersburg 760 mm Hg. - is the norm. But for Moscow, which is located higher, the normal pressure is 748 mm Hg.

The pressure changes not only vertically, but also horizontally. This is especially felt during the passage of cyclones.

The structure of the atmosphere

The atmosphere is like a layer cake. And each layer has its own characteristics.

. Troposphere is the layer closest to the Earth. The "thickness" of this layer changes as you move away from the equator. Above the equator, the layer extends upwards for 16-18 km, in temperate zones - for 10-12 km, at the poles - for 8-10 km.

It is here that 80% of the total mass of air and 90% of water vapor are contained. Clouds form here, cyclones and anticyclones arise. The air temperature depends on the altitude of the area. On average, it drops by 0.65°C for every 100 meters.

. tropopause- transitional layer of the atmosphere. Its height is from several hundred meters to 1-2 km. The air temperature in summer is higher than in winter. So, for example, over the poles in winter -65 ° C. And over the equator at any time of the year it is -70 ° C.

. Stratosphere- this is a layer, the upper boundary of which runs at an altitude of 50-55 kilometers. Turbulence is low here, water vapor content in the air is negligible. But a lot of ozone. Its maximum concentration is at an altitude of 20-25 km. In the stratosphere, the air temperature begins to rise and reaches +0.8 ° C. This is due to the fact that the ozone layer interacts with ultraviolet radiation.

. Stratopause- a low intermediate layer between the stratosphere and the mesosphere following it.

. Mesosphere- the upper boundary of this layer is 80-85 kilometers. Here complex photochemical processes involving free radicals take place. It is they who provide that gentle blue glow of our planet, which is seen from space.

Most comets and meteorites burn up in the mesosphere.

. Mesopause- the next intermediate layer, the air temperature in which is at least -90 °.

. Thermosphere- the lower boundary begins at an altitude of 80 - 90 km, and the upper boundary of the layer passes approximately at the mark of 800 km. The air temperature is rising. It can vary from +500° C to +1000° C. During the day, temperature fluctuations amount to hundreds of degrees! But the air here is so rarefied that the understanding of the term "temperature" as we imagine it is not appropriate here.

. Ionosphere- unites mesosphere, mesopause and thermosphere. The air here consists mainly of oxygen and nitrogen molecules, as well as quasi-neutral plasma. The sun's rays, falling into the ionosphere, strongly ionize air molecules. In the lower layer (up to 90 km), the degree of ionization is low. The higher, the more ionization. So, at an altitude of 100-110 km, electrons are concentrated. This contributes to the reflection of short and medium radio waves.

The most important layer of the ionosphere is the upper one, which is located at an altitude of 150-400 km. Its peculiarity is that it reflects radio waves, and this contributes to the transmission of radio signals over long distances.

It is in the ionosphere that such a phenomenon as aurora occurs.

. Exosphere- consists of oxygen, helium and hydrogen atoms. The gas in this layer is very rarefied, and often hydrogen atoms escape into outer space. Therefore, this layer is called the "scattering zone".

The first scientist who suggested that our atmosphere has weight was the Italian E. Torricelli. Ostap Bender, for example, in the novel "The Golden Calf" lamented that each person was pressed by an air column weighing 14 kg! But the great strategist was a little mistaken. An adult person experiences pressure of 13-15 tons! But we do not feel this heaviness, because atmospheric pressure is balanced by the internal pressure of a person. The weight of our atmosphere is 5,300,000,000,000,000 tons. The figure is colossal, although it is only a millionth of the weight of our planet.

Earth's atmosphere

Atmosphere(from. other Greekἀτμός - steam and σφαῖρα - ball) - gas shell ( geosphere) surrounding the planet Earth. Its inner surface is covered hydrosphere and partially bark, the outer one borders on the near-Earth part of outer space.

The totality of sections of physics and chemistry that study the atmosphere is commonly called atmospheric physics. The atmosphere determines weather on the surface of the Earth, is engaged in the study of weather meteorology, and long-term variations climate - climatology.

The structure of the atmosphere

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. It contains more than 80% of the total mass of atmospheric air and about 90% of all water vapor present in the atmosphere. highly developed in the troposphere turbulence And convection, arise clouds, develop cyclones And anticyclones. The temperature decreases with increasing height with an average vertical gradient 0.65°/100 m

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

Stratosphere

The 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 its increase in the 25-40 km layer from -56.5 to 0.8 ° FROM(upper stratosphere or region inversions). 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 stratopause and is the boundary between the stratosphere and mesosphere.

Stratopause

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

Mesosphere

Earth's atmosphere

Mesosphere starts at an altitude of 50 km and extends up to 80-90 km. The 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 involving free radicals, vibrationally excited molecules, etc., determine the glow of the atmosphere.

Mesopause

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

Karman Line

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

Thermosphere

Main article: Thermosphere

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

Atmospheric layers up to a height of 120 km

Exosphere (scattering sphere)

Exosphere- scattering zone, the outer part of the thermosphere, located above 700 km. The gas in the exosphere is very rarefied, and hence its particles leak into interplanetary space ( dissipation).

Up to a height of 100 km, the atmosphere is a homogeneous, well-mixed mixture of gases. In higher layers, the distribution of gases in 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 ~1500 °C. Above 200 km, significant fluctuations in temperature and gas density are observed in time and space.

At an altitude of about 2000-3000 km, the exosphere gradually passes into the so-called near space vacuum, which is filled with highly rarefied particles of interplanetary gas, mainly hydrogen atoms. But this gas is only part of the interplanetary matter. The other part is composed of dust-like particles of cometary and meteoric origin. In addition to extremely rarefied dust-like particles, electromagnetic and corpuscular radiation of solar and galactic origin penetrates into this space.

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

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

Physical properties

The thickness of the atmosphere is approximately 2000 - 3000 km from the Earth's surface. Total mass air- (5.1-5.3) × 10 18 kg. Molar mass clean dry air is 28.966. Pressure at 0 °C at sea level 101.325 kPa; critical temperature-140.7 °C; critical pressure 3.7 MPa; C p 1.0048×10 3 J/(kg K)(at 0°C), C v 0.7159×10 3 J/(kg K) (at 0 °C). Solubility of air in water at 0 °C - 0.036%, at 25 °C - 0.22%.

Physiological and other properties of the atmosphere

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

The atmosphere provides us with the oxygen we need to breathe. However, due to the drop in the total pressure of the atmosphere as you rise to a height, the partial pressure of oxygen also decreases accordingly.

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

At an altitude of about 19-20 km, the atmospheric pressure drops to 47 mm Hg. Art. Therefore, at this height, water and interstitial fluid begin to boil in the human body. Outside the pressurized cabin at these 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, an intense effect on the body is exerted by ionizing radiation- primary cosmic rays; at altitudes of more than 40 km, the ultraviolet part of the solar spectrum, which is dangerous for humans, operates.

As we rise to an ever greater height above the Earth's surface, gradually weaken, and then completely disappear, such phenomena that are familiar to us observed in the lower layers of the atmosphere, such as the propagation of sound, the emergence of aerodynamic lifting force and resistance, heat transfer convection and etc.

In rarefied layers of air, propagation sound turns out to be 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, concepts familiar to every pilot numbers M And sound barrier lose their meaning, there passes the conditional Karman Line beyond which begins the sphere of purely ballistic flight, which can be controlled only by using reactive forces.

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

Composition of the atmosphere

Composition of dry air

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

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

In addition to the gases indicated in the table, the atmosphere contains SO 2, NH 3, CO, ozone, hydrocarbons, HCl, HF, couples hg, I 2 , and NO and many other gases in minor quantities. The troposphere constantly contains a large number of suspended solid and liquid particles ( spray can).

History of the formation of the atmosphere

According to the most common theory, the Earth's atmosphere has been in four different compositions over time. Initially, it consisted of light gases ( hydrogen And helium) captured from interplanetary space. This 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, steam). This is how secondary atmosphere(about three billion years before our days). This atmosphere was restorative. Further, the process of formation of the atmosphere was determined by the following factors:

leakage of light gases (hydrogen and helium) into interplanetary space;

chemical reactions occurring in the atmosphere under the influence of ultraviolet radiation, lightning discharges and some other factors.

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

Nitrogen

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

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

Oxygen

The composition of the atmosphere began to change radically with the advent of living organisms, as a result 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, oxide form gland contained in the oceans, etc. At the end of this stage, the oxygen content in the atmosphere began to grow. Gradually, a modern atmosphere with oxidizing properties formed. Since this caused serious and abrupt changes in many processes occurring in atmosphere, lithosphere And biosphere, this event is called Oxygen catastrophe.

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

Carbon dioxide

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

noble gases

Source of inert gases - argon, helium And krypton- volcanic eruptions and decay of radioactive elements. The earth as a whole and the atmosphere in particular are depleted in 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, the evolution of the atmosphere began to be influenced by human. The result of his activities was a constant significant increase in the content of carbon dioxide in the atmosphere due to the combustion of hydrocarbon fuels accumulated in previous geological epochs. Huge amounts of CO 2 are consumed during photosynthesis and absorbed by the world's oceans. This gas enters the atmosphere due to the decomposition of carbonate rocks and organic substances of plant and animal origin, as well as due to volcanism and human production activities. Over the past 100 years, the content of CO 2 in the atmosphere has increased by 10%, with the main part (360 billion tons) coming from fuel combustion. If the growth rate of fuel combustion continues, then in the next 50 - 60 years the amount of CO 2 in the atmosphere will double and may lead to global climate change.

Fuel combustion is the main source of both pollutant gases ( SO, NO, SO 2 ). Sulfur dioxide is oxidized by atmospheric oxygen to SO 3 in the upper atmosphere, which in turn interacts with water vapor and ammonia, and the resulting sulfuric acid (H 2 SO 4 ) And ammonium sulfate ((NH 4 ) 2 SO 4 ) return to the surface of the Earth in the form of a so-called. acid rain. Usage internal combustion engines leads to significant air pollution with nitrogen oxides, hydrocarbons and lead compounds ( tetraethyl lead Pb(CH 3 CH 2 ) 4 ) ).

Aerosol pollution of the atmosphere is caused both by natural causes (volcanic eruption, dust storms, entrainment of sea water droplets and plant pollen, etc.) and by human economic activity (mining of ores and building materials, fuel combustion, cement production, etc.). Intense large-scale removal of solid particles into the atmosphere is one of the possible causes of climate change on the planet.

The atmosphere has a layered structure. The boundaries between the layers are not sharp and their height depends on latitude and season. The layered structure is the result of temperature changes at different altitudes. Weather is formed in the troposphere (lower about 10 km: about 6 km above the poles and more than 16 km above the equator). And the upper limit of the troposphere is higher in summer than in winter.

From the Earth's surface upwards these layers are:

Troposphere

Stratosphere

Mesosphere

Thermosphere

Exosphere

Troposphere

The lower part of the atmosphere, up to a height of 10-15 km, in which 4/5 of the entire mass of atmospheric air is concentrated, is called the troposphere. It is typical for it that the temperature here falls with height by an average of 0.6°/100 m (in some cases, the temperature distribution along the vertical varies over a wide range). The troposphere contains almost all the water vapor in the atmosphere and almost all clouds form. Turbulence is also highly developed here, especially near the earth's surface, as well as in the so-called jet streams in the upper part of the troposphere.

The height to which the troposphere extends over every place on Earth varies from day to day. In addition, even on average, it is different under different latitudes and in different seasons of the year. On average, the annual troposphere extends over the poles to a height of about 9 km, over temperate latitudes up to 10-12 km and over the equator up to 15-17 km. The average annual air temperature near the earth's surface is about +26° at the equator and about -23° at the north pole. At the upper boundary of the troposphere above the equator, the average temperature is about -70°, over the north pole in winter about -65°, and in summer about -45°.

The air pressure at the upper boundary of the troposphere, corresponding to its height, is 5-8 times less than at the earth's surface. Therefore, the bulk of atmospheric air is located in the troposphere. The processes occurring in the troposphere are of direct and decisive importance for the weather and climate near the earth's surface.

All water vapor is concentrated in the troposphere, which is why all clouds form within the troposphere. The temperature decreases with altitude.

The sun's rays easily pass through the troposphere, and the heat that the Earth heated by the sun's rays radiates accumulates in the troposphere: gases such as carbon dioxide, methane, and water vapor retain heat. This mechanism of warming the atmosphere from the Earth, heated by solar radiation, is called the greenhouse effect. It is because the Earth is the source of heat for the atmosphere that the temperature of the air decreases with height.

The boundary between the turbulent troposphere and the calm stratosphere is called the tropopause. Here, fast moving winds called "jet streams" are formed.

It was once assumed that the temperature of the atmosphere also drops above the troposphere, but measurements in the high layers of the atmosphere showed that this is not so: immediately above the tropopause, the temperature is almost constant, and then begins to increase. Strong horizontal winds blow in the stratosphere without forming turbulence. The air of the stratosphere is very dry and therefore clouds are rare. So-called mother-of-pearl clouds are formed.

The stratosphere is very important for life on Earth, since it is in this layer that there is a small amount of ozone that absorbs strong ultraviolet radiation that is harmful to life. By absorbing ultraviolet radiation, ozone heats the stratosphere.

Stratosphere

Above the troposphere up to a height of 50-55 km lies the stratosphere, characterized by the fact that the temperature in it, on average, increases with height. The transition layer between the troposphere and stratosphere (1-2 km thick) is called the tropopause.

Above were data on the temperature at the upper boundary of the troposphere. These temperatures are also characteristic of the lower stratosphere. Thus, the air temperature in the lower stratosphere above the equator is always very low; moreover, in summer it is much lower than above the pole.

The lower stratosphere is more or less isothermal. But, starting from a height of about 25 km, the temperature in the stratosphere rapidly increases with height, reaching maximum, moreover, positive values ​​(from +10 to +30 °) at an altitude of about 50 km. Due to the increase in temperature with height, turbulence in the stratosphere is low.

There is very little water vapor in the stratosphere. However, at altitudes of 20-25 km, very thin, so-called mother-of-pearl clouds are sometimes observed at high latitudes. During the day they are not visible, but at night they seem to glow, as they are illuminated by the sun below the horizon. These clouds are made up of supercooled water droplets. The stratosphere is also characterized by the fact that it mainly contains atmospheric ozone, as mentioned above.

Mesosphere

Above the stratosphere lies a layer of the mesosphere, up to about 80 km. Here the temperature drops with height to several tens of degrees below zero. Due to the rapid drop in temperature with height, turbulence is highly developed in the mesosphere. At heights close to the upper boundary of the mesosphere (75-90 km), there are still a special kind of clouds, also illuminated by the sun at night, the so-called silver clouds. It is most likely that they are composed of ice crystals.

At the upper boundary of the mesosphere, the air pressure is 200 times less than at the earth's surface. Thus, the troposphere, stratosphere and mesosphere together, up to a height of 80 km, contain more than 99.5% of the total mass of the atmosphere. The overlying layers contain a negligible amount of air

At an altitude of about 50 km above the Earth, the temperature begins to fall again, marking the upper boundary of the stratosphere and the beginning of the next layer - the mesosphere. The mesosphere has the coldest temperature in the atmosphere: from -2 to -138 degrees Celsius. Here are the highest clouds: in clear weather, they can be seen at sunset. They are called noctilucent (luminous at night).

Thermosphere

The upper part of the atmosphere, above the mesosphere, is characterized by very high temperatures and is therefore called the thermosphere. However, two parts are distinguished in it: the ionosphere, which extends from the mesosphere to heights of the order of a thousand kilometers, and the outer part lying above it - the exosphere, passing into the earth's corona.

The air in the ionosphere is extremely rarefied. We have already indicated that at altitudes of 300-750 km its average density is about 10-8-10-10 g/m3. But even with such a low density, each cubic centimeter of air at an altitude of 300 km still contains about one billion (109) molecules or atoms, and at an altitude of 600 km - more than 10 million (107). This is several orders of magnitude greater than the content of gases in interplanetary space.

The ionosphere, as the name itself says, is characterized by a very strong degree of air ionization - the content of ions here is many times greater than in the underlying layers, despite the strong overall rarefaction of the air. These ions are mainly charged oxygen atoms, charged nitric oxide molecules, and free electrons. Their content at altitudes of 100-400 km is about 1015-106 per cubic centimeter.

In the ionosphere, several layers, or regions, are distinguished with maximum ionization, especially at altitudes of 100-120 km and 200-400 km. But even in the intervals between these layers, the degree of ionization of the atmosphere remains very high. The position of the ionospheric layers and the concentration of ions in them change all the time. Sporadic accumulations of electrons with a particularly high concentration are called electron clouds.

The electrical conductivity of the atmosphere depends on the degree of ionization. Therefore, in the ionosphere, the electrical conductivity of air is generally 1012 times greater than that of the earth's surface. Radio waves experience absorption, refraction and reflection in the ionosphere. Waves longer than 20 m cannot pass through the ionosphere at all: they are already reflected by electron layers of low concentration in the lower part of the ionosphere (at altitudes of 70-80 km). Medium and short waves are reflected by the overlying ionospheric layers.

It is due to reflection from the ionosphere that long-range communication at short waves is possible. Multiple reflections from the ionosphere and the earth's surface allow short waves to propagate in a zigzag manner over long distances, skirting the surface of the globe. Since the position and concentration of the ionospheric layers are continuously changing, the conditions for absorption, reflection and propagation of radio waves also change. Therefore, reliable radio communication requires continuous study of the state of the ionosphere. Observations on the propagation of radio waves are precisely the means for such research.

In the ionosphere, auroras and a glow of the night sky close to them in nature are observed - a constant luminescence of atmospheric air, as well as sharp fluctuations in the magnetic field - ionospheric magnetic storms.

Ionization in the ionosphere owes its existence to the action of ultraviolet radiation from the Sun. Its absorption by atmospheric gas molecules leads to the appearance of charged atoms and free electrons, as discussed above. Fluctuations in the magnetic field in the ionosphere and auroras depend on fluctuations in solar activity. Changes in solar activity are associated with changes in the flux of corpuscular radiation coming from the Sun into the Earth's atmosphere. Namely, corpuscular radiation is of fundamental importance for these ionospheric phenomena.

The temperature in the ionosphere increases with height to very high values. At altitudes of about 800 km it reaches 1000°.

Speaking about the high temperatures of the ionosphere, they mean that particles of atmospheric gases move there at very high speeds. However, the air density in the ionosphere is so low that a body located in the ionosphere, such as a flying satellite, will not be heated by heat exchange with air. The temperature regime of the satellite will depend on the direct absorption of solar radiation by it and on the return of its own radiation to the surrounding space. The thermosphere is located above the mesosphere at an altitude of 90 to 500 km above the Earth's surface. The gas molecules here are highly scattered, they absorb X-rays and the short-wavelength part of ultraviolet radiation. Because of this, the temperature can reach 1000 degrees Celsius.

The thermosphere basically corresponds to the ionosphere, where ionized gas reflects radio waves back to the Earth - this phenomenon makes it possible to establish radio communications.

Exosphere

Above 800-1000 km the atmosphere passes into the exosphere and gradually into interplanetary space. The velocities of gas particles, especially light ones, are very high here, and due to the extremely rarefied air at these heights, particles can fly around the Earth in elliptical orbits without colliding with each other. In this case, individual particles can have velocities sufficient to overcome the force of gravity. For uncharged particles, the critical speed will be 11.2 km/sec. Such especially fast particles can, moving along hyperbolic trajectories, fly out of the atmosphere into outer space, "escape", and dissipate. Therefore, the exosphere is also called the scattering sphere.

It is predominantly hydrogen atoms that escape, which is the dominant gas in the highest layers of the exosphere.

It has recently been assumed that the exosphere, and with it the earth's atmosphere in general, ends at altitudes of the order of 2000-3000 km. But observations from rockets and satellites have given rise to the idea that hydrogen escaping from the exosphere forms a so-called terrestrial corona around the Earth, extending to more than 20,000 km. Of course, the density of gas in the Earth's corona is negligible. For every cubic centimeter, there are on average only about a thousand particles. But in interplanetary space, the concentration of particles (mainly protons and electrons) is at least ten times less.

With the help of satellites and geophysical rockets, the existence in the upper part of the atmosphere and in near-Earth outer space of the Earth's radiation belt, which begins at an altitude of several hundred kilometers and extends for tens of thousands of kilometers from the earth's surface, has been established. This belt consists of electrically charged particles - protons and electrons, captured by the Earth's magnetic field and moving at very high speeds. Their energy is on the order of hundreds of thousands of electron volts. The radiation belt constantly loses particles in the earth's atmosphere and is replenished by fluxes of solar corpuscular radiation.

atmosphere temperature stratosphere troposphere

The gaseous envelope that surrounds 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 transitional 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 the weather happens

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 at its bottom - the surface of the planet. It envelops the surface of the Earth and extends upwards for several kilometers. The word troposphere means "change of the ball". A very fitting name, as this layer is where our day to day weather happens.

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. It is the only part of the entire composition of the 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 is a thin layer called the tropopause, which is just a buffer between the troposphere and stratosphere.

Stratosphere: home of 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 balloons travel.

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

Because the stratosphere has warmer temperatures at the bottom and cooler temperatures at the top, convection (vertical movements 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, since the layer acts as a "cap" for convection, through which storm clouds do not penetrate.

The stratosphere is again followed by 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

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

Exosphere: the boundary of 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 meteorological satellites revolve around the Earth.

How about the ionosphere?

The ionosphere is not a separate layer, and in fact this term is used to refer to the atmosphere at an altitude of 60 to 1000 km. 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 Sun's radiation is ionized when it passes the Earth's magnetic fields at and . This phenomenon is observed from the earth as the northern lights.

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

tropopause

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

Stratosphere

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

Stratopause

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

Mesosphere

Earth's atmosphere

Earth's atmosphere boundary

Thermosphere

The upper limit is about 800 km. The temperature rises to altitudes of 200-300 km, where it reaches values ​​of the order of 1500 K, after which it remains almost constant up to high altitudes. Under the influence of ultraviolet and x-ray solar radiation and cosmic radiation, air is ionized ("polar lights") - 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 above the thermosphere. In this region, the absorption of solar radiation is insignificant and the temperature does not actually change with height.

Exosphere (scattering sphere)

Up to a height of 100 km, the atmosphere is a homogeneous, well-mixed mixture of gases. In higher layers, the distribution of gases in 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 are observed in time and space.

At an altitude of about 2000-3500 km, the exosphere gradually passes into the so-called near space vacuum, which is filled with highly rarefied particles of interplanetary gas, mainly hydrogen atoms. But this gas is only part of the interplanetary matter. The other part is composed of dust-like particles of cometary and meteoric origin. In addition to extremely rarefied dust-like particles, electromagnetic and corpuscular radiation of solar and galactic origin penetrates into this space.

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

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

Physiological and other properties of the atmosphere

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

The atmosphere provides us with the oxygen we need to breathe. However, due to the drop in the total pressure of the atmosphere as you rise to a height, the partial pressure of oxygen also decreases accordingly.

In rarefied layers of air, the propagation of sound 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: the conditional Karman line passes there, beyond which the area of ​​\u200b\u200bpurely ballistic flight begins, which can only be controlled using reactive forces.

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

History of the formation of the atmosphere

According to the most common theory, the Earth's atmosphere has been in three different compositions over time. Initially, it consisted of light gases (hydrogen and helium) captured from interplanetary space. This 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 secondary atmosphere(about three billion years before our days). This atmosphere was restorative. Further, the process of formation of the atmosphere was determined by the following factors:

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

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

Nitrogen

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

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

Oxygen

The composition of the atmosphere began to change radically with the advent of living organisms on Earth, as a result of photosynthesis, accompanied by the release of oxygen and the absorption of carbon dioxide. Initially, oxygen was spent on the oxidation of reduced compounds - ammonia, hydrocarbons, the ferrous form of iron contained in the oceans, etc. At the end of this stage, the oxygen content in the atmosphere began to grow. Gradually, a modern atmosphere with oxidizing properties formed. Since this caused serious and abrupt changes in many processes occurring in the atmosphere, lithosphere and biosphere, this event was called the Oxygen catastrophe.

noble gases

Air pollution

Recently, man has begun to influence the evolution of the atmosphere. The result of his activities was a constant significant increase in the content of carbon dioxide in the atmosphere due to the combustion of hydrocarbon fuels accumulated in previous geological epochs. Huge amounts of CO 2 are consumed during photosynthesis and absorbed by the world's oceans. This gas enters the atmosphere due to the decomposition of carbonate rocks and organic substances of plant and animal origin, as well as due to volcanism and human production activities. Over the past 100 years, the content of CO 2 in the atmosphere has increased by 10%, with the main part (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 CO 2 in the atmosphere will double and may lead to global climate change.

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

Aerosol pollution of the atmosphere is caused both by natural causes (volcanic eruption, dust storms, entrainment of sea water droplets and plant pollen, etc.) and by human economic activity (mining of ores and building materials, fuel combustion, cement production, etc.). Intense large-scale removal of solid particles into the atmosphere is one of the possible causes of climate change on the planet.

see also

• Jacchia (atmosphere model)

Notes

Links

Literature

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