10.045×10 3 J/(kg*K) (in the temperature range from 0-100°C), C v 8.3710*10 3 J/(kg*K) (0-1500°C). The solubility of air in water at 0°C is 0.036%, at 25°C - 0.22%.
Atmospheric composition
History of atmospheric formation
Early history
Currently, science cannot trace all stages of the formation of the Earth with one hundred percent accuracy. According to the most common theory, the Earth's atmosphere has had four different compositions over time. Initially, it consisted of light gases (hydrogen and helium) captured from interplanetary space. This is the so-called primary atmosphere. At the next stage, active volcanic activity led to the saturation of the atmosphere with gases other than hydrogen (hydrocarbons, ammonia, water vapor). This is how it was formed secondary atmosphere. This atmosphere was restorative. Further, the process of atmosphere formation was determined by the following factors:
- constant leakage of hydrogen 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).
The emergence of life and oxygen
With the appearance of living organisms on Earth as a result of photosynthesis, accompanied by the release of oxygen and the absorption of carbon dioxide, the composition of the atmosphere began to change. There is, however, data (analysis of the isotopic composition of atmospheric oxygen and that released during photosynthesis) that indicates the geological origin of atmospheric oxygen.
Initially, oxygen was spent on the oxidation of reduced compounds - hydrocarbons, ferrous form of iron contained in the oceans, etc. At the end of this stage, the oxygen content in the atmosphere began to increase.
In the 1990s, experiments were carried out to create a closed ecological system (“Biosphere 2”), during which it was not possible to create a stable system with a uniform air composition. The influence of microorganisms led to a decrease in oxygen levels and an increase in the amount of carbon dioxide.
Nitrogen
The formation of a large amount of N 2 is due to the oxidation of the primary ammonia-hydrogen atmosphere with molecular O 2, which began to come from the surface of the planet as a result of photosynthesis, supposedly about 3 billion years ago (according to another version, atmospheric oxygen is of geological origin). Nitrogen is oxidized to NO in the upper atmosphere, used in industry and bound by nitrogen-fixing bacteria, while N2 is released into the atmosphere as a result of denitrification of nitrates and other nitrogen-containing compounds.
Nitrogen N 2 is an inert gas and reacts only under specific conditions (for example, during a lightning discharge). Cyanobacteria and some bacteria (for example, nodule bacteria that form rhizobial symbiosis with leguminous plants) can oxidize it and convert it into biological form.
The oxidation of molecular nitrogen by electrical discharges is used in the industrial production of nitrogen fertilizers, and it also led to the formation of unique deposits of nitrate in the Chilean Atacama Desert.
Noble gases
Fuel combustion is the main source of polluting gases (CO, NO, SO2). Sulfur dioxide is oxidized by air O 2 to SO 3 in the upper layers of the atmosphere, which interacts with H 2 O and NH 3 vapors, and the resulting H 2 SO 4 and (NH 4) 2 SO 4 return to the Earth's surface along with precipitation. The use of internal combustion engines leads to significant atmospheric pollution with nitrogen oxides, hydrocarbons and Pb compounds.
Aerosol pollution of the atmosphere is caused by both natural causes (volcanic eruptions, dust storms, carryover of droplets of sea water and plant pollen particles, etc.) and human economic activities (mining ores and building materials, burning fuel, making cement, etc.) . Intense large-scale release of particulate matter into the atmosphere is one of the possible causes of climate change on the planet.
The structure of the atmosphere and characteristics of individual shells
The physical state of the atmosphere is determined by weather and climate. Basic parameters of the atmosphere: air density, pressure, temperature and composition. As altitude increases, air density and atmospheric pressure decrease. Temperature also changes with changes in altitude. The vertical structure of the atmosphere is characterized by different temperature and electrical properties, and different air conditions. Depending on the temperature in the atmosphere, the following main layers are distinguished: troposphere, stratosphere, mesosphere, thermosphere, exosphere (scattering sphere). The transitional regions of the atmosphere between neighboring shells are called tropopause, stratopause, etc., respectively.
Troposphere
Stratosphere
In the stratosphere, most of the short-wave part of ultraviolet radiation (180-200 nm) is retained and the energy of short waves is transformed. Under the influence of these rays, magnetic fields change, molecules disintegrate, ionization occurs, and new formation of gases and other chemical compounds occurs. These processes can be observed in the form of northern lights, lightning, and other glows.
In the stratosphere and higher layers, under the influence of solar radiation, gas molecules dissociate into atoms (above 80 km CO 2 and H 2 dissociate, above 150 km - O 2, above 300 km - H 2). At an altitude of 100-400 km, ionization of gases also occurs in the ionosphere; at an altitude of 320 km, the concentration of charged particles (O + 2, O − 2, N + 2) is ~ 1/300 of the concentration of neutral particles. In the upper layers of the atmosphere there are free radicals - OH, HO 2, etc.
There is almost no water vapor in the stratosphere.
Mesosphere
Up to an altitude of 100 km, the atmosphere is a homogeneous, well-mixed mixture of gases. In higher layers, the distribution of gases by height depends on their molecular weights; the concentration of heavier gases decreases faster with distance from the Earth's surface. Due to a 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 in time and space are observed.
At an altitude of about 2000-3000 km, the exosphere gradually turns into the so-called near-space vacuum, which is filled with highly rarefied particles of interplanetary gas, mainly hydrogen atoms. But this gas represents only part of the interplanetary matter. The other part consists of dust particles of cometary and meteoric origin. In addition to these extremely rarefied particles, electromagnetic and corpuscular radiation of solar and galactic origin penetrates into this space.
The troposphere accounts for about 80% of the mass of the atmosphere, the stratosphere - about 20%; the mass of the mesosphere is no more than 0.3%, the thermosphere is less than 0.05% of the total mass of the atmosphere. Based on the electrical properties in the atmosphere, the neutronosphere and ionosphere are distinguished. It is currently believed that the atmosphere extends to an altitude of 2000-3000 km.
Depending on the composition of the gas in the atmosphere, they emit homosphere And heterosphere. Heterosphere- This is the area where gravity affects the separation of gases, since their mixing at such an altitude is negligible. This implies a variable composition of the heterosphere. Below it lies a well-mixed, homogeneous part of the atmosphere called the homosphere. The boundary between these layers is called the turbopause, it lies at an altitude of about 120 km.
Atmospheric properties
Already at an altitude of 5 km above sea level, an untrained person begins to experience oxygen starvation and without adaptation, a person’s performance is significantly reduced. The physiological zone of the atmosphere ends here. Human breathing becomes impossible at an altitude of 15 km, although up to approximately 115 km the atmosphere contains oxygen.
The atmosphere supplies us with the oxygen necessary for breathing. However, due to the drop in the total pressure of the atmosphere, as you rise to altitude, the partial pressure of oxygen decreases accordingly.
The human lungs constantly contain about 3 liters of alveolar air. The partial pressure of oxygen in alveolar air at normal atmospheric pressure is 110 mmHg. Art., carbon dioxide pressure - 40 mm Hg. Art., and water vapor −47 mm Hg. Art. With increasing altitude, oxygen pressure drops, and the total vapor pressure of water and carbon dioxide in the lungs remains almost constant - about 87 mm Hg. Art. The supply of oxygen to the lungs will completely stop when the ambient air pressure becomes equal to this value.
At an altitude of about 19-20 km, the atmospheric pressure drops to 47 mm Hg. Art. Therefore, at this altitude, water and interstitial fluid begin to boil in the human body. Outside the pressurized cabin at these altitudes, death occurs almost instantly. Thus, from the point of view of human physiology, “space” begins already at an altitude of 15-19 km.
Dense layers of air - the troposphere and stratosphere - protect us from the damaging effects of radiation. With sufficient rarefaction of air, at altitudes of more than 36 km, ionizing radiation - primary cosmic rays - has an intense effect on the body; At altitudes of more than 40 km, the ultraviolet part of the solar spectrum is dangerous for humans.
Atmosphere (from ancient Greek ἀτμός - steam and σφαῖρα - ball) is a gas shell (geosphere) surrounding planet Earth. Its inner surface covers the hydrosphere and partly the earth's crust, while its outer surface borders the near-Earth part of outer space.
The set of branches of physics and chemistry that study the atmosphere is usually called atmospheric physics. The atmosphere determines the weather on the Earth's surface, meteorology studies weather, and climatology deals with long-term climate variations.
Physical properties
The thickness of the atmosphere is approximately 120 km from the Earth's surface. The total mass of air in the atmosphere is (5.1-5.3) 1018 kg. Of these, the mass of dry air is (5.1352 ± 0.0003) 1018 kg, the total mass of water vapor is on average 1.27 1016 kg.
The molar mass of clean dry air is 28.966 g/mol, and the density of air at the sea surface is approximately 1.2 kg/m3. The pressure at 0 °C at sea level is 101.325 kPa; critical temperature - −140.7 °C (~132.4 K); critical pressure - 3.7 MPa; Cp at 0 °C - 1.0048·103 J/(kg·K), Cv - 0.7159·103 J/(kg·K) (at 0 °C). Solubility of air in water (by mass) at 0 °C - 0.0036%, at 25 °C - 0.0023%.
The following are accepted as “normal conditions” at the Earth’s surface: density 1.2 kg/m3, barometric pressure 101.35 kPa, temperature plus 20 °C and relative humidity 50%. These conditional indicators have purely engineering significance.
Chemical composition
The Earth's atmosphere arose as a result of the release of gases during volcanic eruptions. With the advent of the oceans and the biosphere, it was formed due to gas exchange with water, plants, animals and the products of their decomposition in soils and swamps.
Currently, the Earth's atmosphere consists mainly of gases and various impurities (dust, water droplets, ice crystals, sea salts, combustion products).
The concentration of gases that make up the atmosphere is almost constant, with the exception of water (H2O) and carbon dioxide (CO2).
Composition of dry air
| Nitrogen | ||
| Oxygen | ||
| Argon | ||
| Water | ||
| Carbon dioxide | ||
| Neon | ||
| Helium | ||
| Methane | ||
| Krypton | ||
| Hydrogen | ||
| Xenon | ||
| Nitrous oxide |
In addition to the gases indicated in the table, the atmosphere contains SO2, NH3, CO, ozone, hydrocarbons, HCl, HF, Hg vapor, I2, as well as NO and many other gases in small quantities. The troposphere constantly contains a large amount of suspended solid and liquid particles (aerosol).
The structure of the atmosphere
Troposphere
Its upper limit is at an altitude of 8-10 km in polar, 10-12 km in temperate and 16-18 km in tropical latitudes; lower in winter than in summer. The lower, main layer of the atmosphere contains more than 80% of the total mass of atmospheric air and about 90% of the total water vapor present in the atmosphere. Turbulence and convection are highly developed in the troposphere, clouds arise, and cyclones and anticyclones develop. Temperature decreases with increasing altitude with an average vertical gradient of 0.65°/100 m
Tropopause
The transition layer from the troposphere to the stratosphere, a layer of the atmosphere in which the decrease in temperature with height stops.
Stratosphere
A layer of the atmosphere located at an altitude of 11 to 50 km. Characterized by a slight change in temperature in the 11-25 km layer (lower layer of the stratosphere) and an increase in temperature in the 25-40 km layer from −56.5 to 0.8 ° C (upper layer of the stratosphere or inversion region). Having reached a value of about 273 K (almost 0 °C) at an altitude of about 40 km, the temperature remains constant up to an altitude of about 55 km. This region of constant temperature is called the stratopause and is the boundary between the stratosphere and mesosphere.
Stratopause
The boundary layer of the atmosphere between the stratosphere and mesosphere. In the vertical temperature distribution there is a maximum (about 0 °C).
Mesosphere
The mesosphere begins at an altitude of 50 km and extends to 80-90 km. Temperature decreases with height with an average vertical gradient of (0.25-0.3)°/100 m. The main energy process is radiant heat transfer. Complex photochemical processes involving free radicals, vibrationally excited molecules, etc. cause atmospheric luminescence.
Mesopause
Transitional layer between the mesosphere and thermosphere. There is a minimum in the vertical temperature distribution (about -90 °C).
Karman Line
The height above sea level, which is conventionally accepted as the boundary between the Earth's atmosphere and space. According to the FAI definition, the Karman line is located at an altitude of 100 km above sea level.
Boundary of the Earth's atmosphere
Thermosphere
The upper limit is about 800 km. The temperature rises to altitudes of 200-300 km, where it reaches values of the order of 1500 K, after which it remains almost constant to high altitudes. Under the influence of ultraviolet and x-ray solar radiation and cosmic radiation, ionization of the air (“auroras”) occurs - the main regions of the ionosphere lie inside the thermosphere. At altitudes above 300 km, atomic oxygen predominates. The upper limit of the thermosphere is largely determined by the current activity of the Sun. During periods of low activity - for example, in 2008-2009 - there is a noticeable decrease in the size of this layer.
Thermopause
The region of the atmosphere adjacent to the thermosphere. In this region, the absorption of solar radiation is negligible and the temperature does not actually change with altitude.
Exosphere (scattering sphere)
The exosphere is a dispersion zone, the outer part of the thermosphere, located above 700 km. The gas in the exosphere is very rarefied, and from here its particles leak into interplanetary space (dissipation).
Up to an altitude of 100 km, the atmosphere is a homogeneous, well-mixed mixture of gases. In higher layers, the distribution of gases by height depends on their molecular weights; the concentration of heavier gases decreases faster with distance from the Earth's surface. Due to the decrease in gas density, the temperature drops from 0 °C in the stratosphere to −110 °C in the mesosphere. However, the kinetic energy of individual particles at altitudes of 200-250 km corresponds to a temperature of ~150 °C. Above 200 km, significant fluctuations in temperature and gas density in time and space are observed.
At an altitude of about 2000-3500 km, the exosphere gradually turns into the so-called near-space vacuum, which is filled with highly rarefied particles of interplanetary gas, mainly hydrogen atoms. But this gas represents only part of the interplanetary matter. The other part consists of dust particles of cometary and meteoric origin. In addition to extremely rarefied dust particles, electromagnetic and corpuscular radiation of solar and galactic origin penetrates into this space.
The troposphere accounts for about 80% of the mass of the atmosphere, the stratosphere - about 20%; 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 neutronosphere and ionosphere are distinguished. It is currently believed that the atmosphere extends to an altitude of 2000-3000 km.
Depending on the composition of the gas in the atmosphere, homosphere and heterosphere are distinguished. The heterosphere is an area where gravity affects the separation of gases, since their mixing at such a height is negligible. This implies a variable composition of the heterosphere. Below it lies a well-mixed, homogeneous part of the atmosphere called the homosphere. The boundary between these layers is called the turbopause; it lies at an altitude of about 120 km.
Other properties of the atmosphere and effects on the human body
Already at an altitude of 5 km above sea level, an untrained person begins to experience oxygen starvation and without adaptation, a person’s performance is significantly reduced. The physiological zone of the atmosphere ends here. Human breathing becomes impossible at an altitude of 9 km, although up to approximately 115 km the atmosphere contains oxygen.
The atmosphere supplies us with the oxygen necessary for breathing. However, due to the drop in the total pressure of the atmosphere, as you rise to altitude, the partial pressure of oxygen decreases accordingly.
The human lungs constantly contain about 3 liters of alveolar air. The partial pressure of oxygen in alveolar air at normal atmospheric pressure is 110 mmHg. Art., carbon dioxide pressure - 40 mm Hg. Art., and water vapor - 47 mm Hg. Art. With increasing altitude, oxygen pressure drops, and the total vapor pressure of water and carbon dioxide in the lungs remains almost constant - about 87 mm Hg. Art. The supply of oxygen to the lungs will completely stop when the ambient air pressure becomes equal to this value.
At an altitude of about 19-20 km, the atmospheric pressure drops to 47 mm Hg. Art. Therefore, at this altitude, water and interstitial fluid begin to boil in the human body. Outside the pressurized cabin at these altitudes, death occurs almost instantly. Thus, from the point of view of human physiology, “space” begins already at an altitude of 15-19 km.
Dense layers of air - the troposphere and stratosphere - protect us from the damaging effects of radiation. With sufficient rarefaction of air, at altitudes of more than 36 km, ionizing radiation - primary cosmic rays - has an intense effect on the body; At altitudes of more than 40 km, the ultraviolet part of the solar spectrum is dangerous for humans.
As we rise to an ever greater height above the Earth's surface, such familiar phenomena observed in the lower layers of the atmosphere as sound propagation, the occurrence of aerodynamic lift and drag, heat transfer by convection, etc. gradually weaken and then completely disappear.
In rarefied layers of air, sound propagation is impossible. Up to altitudes of 60-90 km, it is still possible to use air resistance and lift for controlled aerodynamic flight. But starting from altitudes of 100-130 km, the concepts of the M number and the sound barrier, familiar to every pilot, lose their meaning: there lies the conventional Karman line, beyond which the region of purely ballistic flight begins, which can only be controlled using reactive forces.
At altitudes above 100 km, the atmosphere is deprived of another remarkable property - the ability to absorb, conduct and transmit thermal energy by convection (i.e. by mixing air). This means that various elements of equipment on the orbital space station will not be able to be cooled from the outside in the same way as is usually done on an airplane - with the help of air jets and air radiators. At this altitude, as in space generally, the only way to transfer heat is thermal radiation.
History of atmospheric formation
According to the most common theory, the Earth's atmosphere has had three different compositions over time. Initially, it consisted of light gases (hydrogen and helium) captured from interplanetary space. This is the so-called primary atmosphere (about four billion years ago). At the next stage, active volcanic activity led to the saturation of the atmosphere with gases other than hydrogen (carbon dioxide, ammonia, water vapor). This is how the secondary atmosphere was formed (about three billion years before the present day). This atmosphere was restorative. Further, the process of atmosphere formation was determined by the following factors:
- leakage of light gases (hydrogen and helium) into interplanetary space;
- chemical reactions occurring in the atmosphere under the influence of ultraviolet radiation, lightning discharges and some other factors.
Gradually, these factors led to the formation of a tertiary atmosphere, characterized by much less hydrogen and much more nitrogen and carbon dioxide (formed as a result of chemical reactions from ammonia and hydrocarbons).
Nitrogen
The formation of a large amount of nitrogen N2 is due to the oxidation of the ammonia-hydrogen atmosphere by molecular oxygen O2, which began to come from the surface of the planet as a result of photosynthesis, starting 3 billion years ago. Nitrogen N2 is also released into the atmosphere as a result of denitrification of nitrates and other nitrogen-containing compounds. Nitrogen is oxidized by ozone to NO in the upper atmosphere.
Nitrogen N2 reacts only under specific conditions (for example, during a lightning discharge). The oxidation of molecular nitrogen by ozone during electrical discharges is used in small quantities in the industrial production of nitrogen fertilizers. Cyanobacteria (blue-green algae) and nodule bacteria that form rhizobial symbiosis with leguminous plants, the so-called, can oxidize it with low energy consumption and convert it into a biologically active form. green manure.
Oxygen
The composition of the atmosphere began to change radically with the appearance of living organisms on Earth, as a result of photosynthesis, accompanied by the release of oxygen and the absorption of carbon dioxide. Initially, oxygen was spent on the oxidation of reduced compounds - ammonia, hydrocarbons, ferrous form of iron contained in the oceans, etc. At the end of this stage, the oxygen content in the atmosphere began to increase. Gradually, a modern atmosphere with oxidizing properties formed. Since this caused serious and abrupt changes in many processes occurring in the atmosphere, lithosphere and biosphere, this event was called the Oxygen Catastrophe.
During the Phanerozoic, the composition of the atmosphere and oxygen content underwent changes. They correlated primarily with the rate of deposition of organic sediment. Thus, during periods of coal accumulation, the oxygen content in the atmosphere apparently significantly exceeded the modern level.
Carbon dioxide
The CO2 content in the atmosphere depends on volcanic activity and chemical processes in the earth's shells, but most of all - on the intensity of biosynthesis and decomposition of organic matter in the Earth's biosphere. Almost the entire current biomass of the planet (about 2.4 1012 tons) is formed due to carbon dioxide, nitrogen and water vapor contained in the atmospheric air. Organics buried in the ocean, swamps and forests turn into coal, oil and natural gas.
Noble gases
The source of noble gases - argon, helium and krypton - is volcanic eruptions and the decay of radioactive elements. The Earth in general and the atmosphere in particular are depleted of inert gases compared to space. It is believed that the reason for this lies in the continuous leakage of gases into interplanetary space.
Air pollution
Recently, humans have begun to influence the evolution of the atmosphere. The result of his activities was a constant increase in the content of carbon dioxide in the atmosphere due to the combustion of hydrocarbon fuels accumulated in previous geological eras. Huge amounts of CO2 are consumed during photosynthesis and absorbed by the world's oceans. This gas enters the atmosphere due to the decomposition of carbonate rocks and organic substances of plant and animal origin, as well as due to volcanism and human industrial activity. Over the past 100 years, the CO2 content in the atmosphere has increased by 10%, with the bulk (360 billion tons) coming from fuel combustion. If the growth rate of fuel combustion continues, then in the next 200-300 years the amount of CO2 in the atmosphere will double and could lead to global climate change.
Fuel combustion is the main source of polluting gases (CO, NO, SO2). Sulfur dioxide is oxidized by atmospheric oxygen to SO3, and nitrogen oxide to NO2 in the upper layers of the atmosphere, which in turn interact with water vapor, and the resulting sulfuric acid H2SO4 and nitric acid HNO3 fall to the surface of the Earth in the form of the so-called. acid rain. The use of internal combustion engines leads to significant atmospheric pollution with nitrogen oxides, hydrocarbons and lead compounds (tetraethyl lead) Pb(CH3CH2)4.
Aerosol pollution of the atmosphere is caused by both natural causes (volcanic eruptions, dust storms, entrainment of drops of sea water and plant pollen, etc.) and human economic activities (mining ores and building materials, burning fuel, making cement, etc.). Intense large-scale release of particulate matter into the atmosphere is one of the possible causes of climate change on the planet.
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At sea level 1013.25 hPa (about 760 mmHg). The global average air temperature at the Earth's surface is 15°C, with temperatures varying from approximately 57°C in subtropical deserts to -89°C in Antarctica. Air density and pressure decrease with height according to a law close to exponential.
The structure of the atmosphere. Vertically, the atmosphere has a layered structure, determined mainly by the features of the vertical temperature distribution (figure), which depends on the geographical location, season, time of day, and so on. The lower layer of the atmosphere - the troposphere - is characterized by a drop in temperature with height (by about 6°C per 1 km), its height from 8-10 km in polar latitudes to 16-18 km in the tropics. Due to the rapid decrease in air density with height, about 80% of the total mass of the atmosphere is located in the troposphere. Above the troposphere is the stratosphere, a layer generally characterized by an increase in temperature with height. The transition layer between the troposphere and stratosphere is called the tropopause. In the lower stratosphere, down to a level of about 20 km, the temperature changes little with height (the so-called isothermal region) and often even decreases slightly. Above that, the temperature increases due to the absorption of UV radiation from the Sun by ozone, slowly at first, and faster from a level of 34-36 km. The upper boundary of the stratosphere - the stratopause - is located at an altitude of 50-55 km, corresponding to the maximum temperature (260-270 K). The layer of the atmosphere located at an altitude of 55-85 km, where the temperature again drops with height, is called the mesosphere; at its upper boundary - the mesopause - the temperature reaches 150-160 K in summer, and 200-230 K in winter. Above the mesopause, the thermosphere begins - a layer characterized by a rapid increase in temperature, reaching 800-1200 K at an altitude of 250 km. In the thermosphere, corpuscular and X-ray radiation from the Sun is absorbed, meteors are slowed down and burned, so it acts as a protective layer of the Earth. Even higher is the exosphere, from where atmospheric gases are dispersed into outer space due to dissipation and where a gradual transition from the atmosphere to interplanetary space occurs.
Atmospheric composition. Up to an altitude of about 100 km, the atmosphere is almost homogeneous in chemical composition and the average molecular weight of the air (about 29) is constant. Near the Earth's surface, the atmosphere consists of nitrogen (about 78.1% by volume) and oxygen (about 20.9%), and also contains small amounts of argon, carbon dioxide (carbon dioxide), neon and other permanent and variable components (see Air ).
In addition, the atmosphere contains small amounts of ozone, nitrogen oxides, ammonia, radon, etc. The relative content of the main components of air is constant over time and uniform in different geographical areas. The content of water vapor and ozone is variable in space and time; Despite their low content, their role in atmospheric processes is very significant.
Above 100-110 km, dissociation of molecules of oxygen, carbon dioxide and water vapor occurs, so the molecular mass of air decreases. At an altitude of about 1000 km, light gases - helium and hydrogen - begin to predominate, and even higher the Earth's atmosphere gradually turns into interplanetary gas.
The most important variable component of the atmosphere is water vapor, which enters the atmosphere through evaporation from the surface of water and moist soil, as well as through transpiration by plants. The relative content of water vapor varies at the earth's surface from 2.6% in the tropics to 0.2% in polar latitudes. It falls quickly with height, decreasing by half already at an altitude of 1.5-2 km. The vertical column of the atmosphere at temperate latitudes contains about 1.7 cm of “precipitated water layer”. When water vapor condenses, clouds form, from which atmospheric precipitation falls in the form of rain, hail, and snow.
An important component of atmospheric air is ozone, concentrated 90% in the stratosphere (between 10 and 50 km), about 10% of it is in the troposphere. Ozone provides absorption of hard UV radiation (with a wavelength of less than 290 nm), and this is its protective role for the biosphere. The values of the total ozone content vary depending on the latitude and season in the range from 0.22 to 0.45 cm (the thickness of the ozone layer at pressure p = 1 atm and temperature T = 0°C). In ozone holes observed in the spring in Antarctica since the early 1980s, ozone content can drop to 0.07 cm. It increases from the equator to the poles and has an annual cycle with a maximum in spring and a minimum in autumn, and the amplitude of the annual cycle is small in the tropics and grows towards high latitudes. A significant variable component of the atmosphere is carbon dioxide, the content of which in the atmosphere has increased by 35% over the past 200 years, which is mainly explained by the anthropogenic factor. Its latitudinal and seasonal variability is observed, associated with plant photosynthesis and solubility in sea water (according to Henry’s law, the solubility of a gas in water decreases with increasing temperature).
An important role in shaping the planet's climate is played by atmospheric aerosol - solid and liquid particles suspended in the air ranging in size from several nm to tens of microns. There are aerosols of natural and anthropogenic origin. Aerosol is formed in the process of gas-phase reactions from the products of plant life and human economic activity, volcanic eruptions, as a result of dust rising by the wind from the surface of the planet, especially from its desert regions, and is also formed from cosmic dust falling into the upper layers of the atmosphere. Most of the aerosol is concentrated in the troposphere; aerosol from volcanic eruptions forms the so-called Junge layer at an altitude of about 20 km. The largest amount of anthropogenic aerosol enters the atmosphere as a result of the operation of vehicles and thermal power plants, chemical production, fuel combustion, etc. Therefore, in some areas the composition of the atmosphere is noticeably different from ordinary air, which required the creation of a special service for observing and monitoring the level of atmospheric air pollution.
Evolution of the atmosphere. The modern atmosphere is apparently of secondary origin: it was formed from gases released by the solid shell of the Earth after the formation of the planet was completed about 4.5 billion years ago. During the geological history of the Earth, the atmosphere has undergone significant changes in its composition under the influence of a number of factors: dissipation (volatilization) of gases, mainly lighter ones, into outer space; release of gases from the lithosphere as a result of volcanic activity; chemical reactions between the components of the atmosphere and the rocks that make up the earth’s crust; photochemical reactions in the atmosphere itself under the influence of solar UV radiation; accretion (capture) of matter from the interplanetary medium (for example, meteoric matter). The development of the atmosphere is closely related to geological and geochemical processes, and over the last 3-4 billion years also to the activity of the biosphere. A significant part of the gases that make up the modern atmosphere (nitrogen, carbon dioxide, water vapor) arose during volcanic activity and intrusion, which carried them from the depths of the Earth. Oxygen appeared in appreciable quantities about 2 billion years ago as a result of photosynthetic organisms that originally arose in the surface waters of the ocean.
Based on data on the chemical composition of carbonate deposits, estimates of the amount of carbon dioxide and oxygen in the atmosphere of the geological past were obtained. Throughout the Phanerozoic (the last 570 million years of Earth's history), the amount of carbon dioxide in the atmosphere varied widely depending on the level of volcanic activity, ocean temperature and the rate of photosynthesis. For most of this time, the concentration of carbon dioxide in the atmosphere was significantly higher than today (up to 10 times). The amount of oxygen in the Phanerozoic atmosphere changed significantly, with a prevailing trend towards its increase. In the Precambrian atmosphere, the mass of carbon dioxide was, as a rule, greater, and the mass of oxygen was smaller compared to the Phanerozoic atmosphere. Fluctuations in the amount of carbon dioxide had a significant impact on the climate in the past, increasing the greenhouse effect with increasing concentrations of carbon dioxide, making the climate much warmer throughout the main part of the Phanerozoic compared to the modern era.
Atmosphere and life. Without an atmosphere, the Earth would be a dead planet. Organic life occurs in close interaction with the atmosphere and the associated climate and weather. Insignificant in mass compared to the planet as a whole (about a part in a million), the atmosphere is an indispensable condition for all forms of life. The most important of the atmospheric gases for the life of organisms are oxygen, nitrogen, water vapor, carbon dioxide, and ozone. When carbon dioxide is absorbed by photosynthetic plants, organic matter is created, which is used as a source of energy by the vast majority of living beings, including humans. Oxygen is necessary for the existence of aerobic organisms, for which the flow of energy is provided by oxidation reactions of organic matter. Nitrogen, assimilated by some microorganisms (nitrogen fixers), is necessary for the mineral nutrition of plants. Ozone, which absorbs hard UV radiation from the Sun, significantly weakens this part of solar radiation harmful to life. The condensation of water vapor in the atmosphere, the formation of clouds and subsequent precipitation supply water to land, without which no form of life is possible. The vital activity of organisms in the hydrosphere is largely determined by the amount and chemical composition of atmospheric gases dissolved in water. Since the chemical composition of the atmosphere significantly depends on the activities of organisms, the biosphere and atmosphere can be considered as part of a single system, the maintenance and evolution of which (see Biogeochemical cycles) was of great importance for changing the composition of the atmosphere throughout the history of the Earth as a planet.
Radiation, heat and water balances of the atmosphere. Solar radiation is practically the only source of energy for all physical processes in the atmosphere. The main feature of the radiation regime of the atmosphere is the so-called greenhouse effect: the atmosphere transmits solar radiation to the earth's surface quite well, but actively absorbs thermal long-wave radiation from the earth's surface, part of which returns to the surface in the form of counter radiation, compensating for radiative heat loss from the earth's surface (see Atmospheric radiation ). In the absence of an atmosphere, the average temperature of the earth's surface would be -18°C, but in reality it is 15°C. Incoming solar radiation is partially (about 20%) absorbed into the atmosphere (mainly by water vapor, water droplets, carbon dioxide, ozone and aerosols), and is also scattered (about 7%) by aerosol particles and density fluctuations (Rayleigh scattering). The total radiation reaching the earth's surface is partially (about 23%) reflected from it. The reflectance coefficient is determined by the reflectivity of the underlying surface, the so-called albedo. On average, the Earth's albedo for the integral flux of solar radiation is close to 30%. It varies from a few percent (dry soil and black soil) to 70-90% for freshly fallen snow. Radiative heat exchange between the earth's surface and the atmosphere significantly depends on albedo and is determined by the effective radiation of the earth's surface and the counter-radiation of the atmosphere absorbed by it. The algebraic sum of radiation fluxes entering the earth's atmosphere from outer space and leaving it back is called the radiation balance.
Transformations of solar radiation after its absorption by the atmosphere and the earth's surface determine the heat balance of the Earth as a planet. The main source of heat for the atmosphere is the earth's surface; heat from it is transferred not only in the form of long-wave radiation, but also by convection, and is also released during condensation of water vapor. The shares of these heat inflows are on average 20%, 7% and 23%, respectively. About 20% of heat is also added here due to the absorption of direct solar radiation. The flux of solar radiation per unit time through a single area perpendicular to the sun's rays and located outside the atmosphere at an average distance from the Earth to the Sun (the so-called solar constant) is equal to 1367 W/m2, changes are 1-2 W/m2 depending on cycle of solar activity. With a planetary albedo of about 30%, the time-average global influx of solar energy to the planet is 239 W/m2. Since the Earth as a planet emits on average the same amount of energy into space, then, according to the Stefan-Boltzmann law, the effective temperature of the outgoing thermal long-wave radiation is 255 K (-18 ° C). At the same time, the average temperature of the earth's surface is 15°C. The difference of 33°C is due to the greenhouse effect.
The water balance of the atmosphere generally corresponds to the equality of the amount of moisture evaporated from the Earth's surface and the amount of precipitation falling on the Earth's surface. The atmosphere over the oceans receives more moisture from evaporation processes than over land, and loses 90% in the form of precipitation. Excess water vapor over the oceans is transported to the continents by air currents. The amount of water vapor transferred into the atmosphere from the oceans to the continents is equal to the volume of the rivers flowing into the oceans.
Air movement. The Earth is spherical, so much less solar radiation reaches its high latitudes than the tropics. As a result, large temperature contrasts arise between latitudes. The temperature distribution is also significantly affected by the relative positions of the oceans and continents. Due to the large mass of ocean waters and the high heat capacity of water, seasonal fluctuations in ocean surface temperature are much less than on land. In this regard, in the middle and high latitudes, the air temperature over the oceans in summer is noticeably lower than over the continents, and higher in winter.
Uneven heating of the atmosphere in different regions of the globe causes a spatially inhomogeneous distribution of atmospheric pressure. At sea level, the pressure distribution is characterized by relatively low values near the equator, increases in the subtropics (high pressure belts) and decreases in the middle and high latitudes. At the same time, over the continents of extratropical latitudes, the pressure is usually increased in winter and decreased in summer, which is associated with temperature distribution. Under the influence of a pressure gradient, air experiences acceleration directed from areas of high pressure to areas of low pressure, which leads to the movement of air masses. Moving air masses are also affected by the deflecting force of the Earth's rotation (Coriolis force), the friction force, which decreases with height, and, for curved trajectories, the centrifugal force. Turbulent mixing of air is of great importance (see Turbulence in the atmosphere).
A complex system of air currents (general atmospheric circulation) is associated with the planetary pressure distribution. In the meridional plane, on average, two or three meridional circulation cells can be traced. Near the equator, heated air rises and falls in the subtropics, forming a Hadley cell. The air of the reverse Ferrell cell also descends there. At high latitudes, a straight polar cell is often visible. Meridional circulation velocities are on the order of 1 m/s or less. Due to the Coriolis force, westerly winds are observed in most of the atmosphere with speeds in the middle troposphere of about 15 m/s. There are relatively stable wind systems. These include trade winds - winds blowing from high pressure zones in the subtropics to the equator with a noticeable eastern component (from east to west). Monsoons are fairly stable - air currents that have a clearly defined seasonal character: they blow from the ocean to the mainland in the summer and in the opposite direction in the winter. The Indian Ocean monsoons are especially regular. In mid-latitudes, the movement of air masses is mainly westerly (from west to east). This is a zone of atmospheric fronts on which large vortices arise - cyclones and anticyclones, covering many hundreds and even thousands of kilometers. Cyclones also occur in the tropics; here they are distinguished by their smaller sizes, but very high wind speeds, reaching hurricane force (33 m/s or more), the so-called tropical cyclones. In the Atlantic and eastern Pacific Oceans they are called hurricanes, and in the western Pacific Ocean they are called typhoons. In the upper troposphere and lower stratosphere, in the areas separating the direct Hadley meridional circulation cell and the reverse Ferrell cell, relatively narrow, hundreds of kilometers wide, jet streams with sharply defined boundaries are often observed, within which the wind reaches 100-150 and even 200 m/ With.
Climate and weather. The difference in the amount of solar radiation arriving at different latitudes to the earth's surface, which is varied in its physical properties, determines the diversity of the Earth's climates. From the equator to tropical latitudes, the air temperature at the earth's surface averages 25-30°C and varies little throughout the year. In the equatorial belt, there is usually a lot of precipitation, which creates conditions of excess moisture there. In tropical zones, precipitation decreases and in some areas becomes very low. Here are the vast deserts of the Earth.
In subtropical and middle latitudes, air temperature varies significantly throughout the year, and the difference between summer and winter temperatures is especially large in areas of the continents far from the oceans. Thus, in some areas of Eastern Siberia, the annual air temperature range reaches 65°C. Humidification conditions in these latitudes are very diverse, depend mainly on the regime of general atmospheric circulation and vary significantly from year to year.
In polar latitudes, the temperature remains low throughout the year, even if there is a noticeable seasonal variation. This contributes to the widespread distribution of ice cover on the oceans and land and permafrost, which occupy over 65% of its area in Russia, mainly in Siberia.
Over the past decades, changes in the global climate have become increasingly noticeable. Temperatures rise more at high latitudes than at low latitudes; more in winter than in summer; more at night than during the day. Over the 20th century, the average annual air temperature at the earth's surface in Russia increased by 1.5-2°C, and in some areas of Siberia an increase of several degrees was observed. This is associated with an increase in the greenhouse effect due to an increase in the concentration of trace gases.
The weather is determined by the conditions of atmospheric circulation and the geographical location of the area; it is most stable in the tropics and most variable in the middle and high latitudes. The weather changes most of all in zones of changing air masses caused by the passage of atmospheric fronts, cyclones and anticyclones carrying precipitation and increased wind. Data for weather forecasting are collected at ground-based weather stations, ships and aircraft, and from meteorological satellites. See also Meteorology.
Optical, acoustic and electrical phenomena in the atmosphere. When electromagnetic radiation propagates in the atmosphere, as a result of refraction, absorption and scattering of light by air and various particles (aerosol, ice crystals, water drops), various optical phenomena arise: rainbows, crowns, halo, mirage, etc. The scattering of light determines the apparent height of the vault of heaven and blue color of the sky. The visibility range of objects is determined by the conditions of light propagation in the atmosphere (see Atmospheric visibility). The transparency of the atmosphere at different wavelengths determines the communication range and the ability to detect objects with instruments, including the possibility of astronomical observations from the Earth’s surface. For studies of optical inhomogeneities of the stratosphere and mesosphere, the twilight phenomenon plays an important role. For example, photographing twilight from spacecraft makes it possible to detect aerosol layers. Features of the propagation of electromagnetic radiation in the atmosphere determine the accuracy of methods for remote sensing of its parameters. All these questions, as well as many others, are studied by atmospheric optics. Refraction and scattering of radio waves determine the possibilities of radio reception (see Propagation of radio waves).
The propagation of sound in the atmosphere depends on the spatial distribution of temperature and wind speed (see Atmospheric acoustics). It is of interest for atmospheric sensing by remote methods. Explosions of charges launched by rockets into the upper atmosphere provided rich information about wind systems and temperature variations in the stratosphere and mesosphere. In a stably stratified atmosphere, when the temperature decreases with height slower than the adiabatic gradient (9.8 K/km), so-called internal waves arise. These waves can propagate upward into the stratosphere and even into the mesosphere, where they attenuate, contributing to increased winds and turbulence.
The negative charge of the Earth and the resulting electric field, the atmosphere, together with the electrically charged ionosphere and magnetosphere, create a global electrical circuit. The formation of clouds and thunderstorm electricity plays an important role in this. The danger of lightning discharges has necessitated the development of lightning protection methods for buildings, structures, power lines and communications. This phenomenon poses a particular danger to aviation. Lightning discharges cause atmospheric radio interference, called atmospherics (see Whistling atmospherics). During a sharp increase in the electric field strength, luminous discharges are observed that appear on the tips and sharp corners of objects protruding above the earth's surface, on individual peaks in the mountains, etc. (Elma lights). The atmosphere always contains a greatly varying amount of light and heavy ions, depending on specific conditions, which determine the electrical conductivity of the atmosphere. The main ionizers of air near the earth's surface are radiation from radioactive substances contained in the earth's crust and atmosphere, as well as cosmic rays. See also Atmospheric electricity.
Human influence on the atmosphere. Over the past centuries, there has been an increase in the concentration of greenhouse gases in the atmosphere due to human economic activities. The percentage of carbon dioxide increased from 2.8-10 2 two hundred years ago to 3.8-10 2 in 2005, the methane content - from 0.7-10 1 approximately 300-400 years ago to 1.8-10 -4 at the beginning of the 21st century; about 20% of the increase in the greenhouse effect over the last century came from freons, which were practically absent in the atmosphere until the mid-20th century. These substances are recognized as stratospheric ozone depleters, and their production is prohibited by the 1987 Montreal Protocol. The increase in the concentration of carbon dioxide in the atmosphere is caused by the burning of ever-increasing amounts of coal, oil, gas and other types of carbon fuels, as well as the clearing of forests, as a result of which the absorption of carbon dioxide through photosynthesis decreases. The concentration of methane increases with an increase in oil and gas production (due to its losses), as well as with the expansion of rice crops and an increase in the number of cattle. All this contributes to climate warming.
To change the weather, methods have been developed to actively influence atmospheric processes. They are used to protect agricultural plants from hail by dispersing special reagents in thunderclouds. There are also methods for dispersing fog at airports, protecting plants from frost, influencing clouds to increase precipitation in desired areas, or for dispersing clouds during public events.
Study of the atmosphere. Information about physical processes in the atmosphere is obtained primarily from meteorological observations, which are carried out by a global network of permanently operating meteorological stations and posts located on all continents and on many islands. Daily observations provide information about air temperature and humidity, atmospheric pressure and precipitation, cloudiness, wind, etc. Observations of solar radiation and its transformations are carried out at actinometric stations. Of great importance for studying the atmosphere are networks of aerological stations, at which meteorological measurements are carried out up to an altitude of 30-35 km using radiosondes. At a number of stations, observations of atmospheric ozone, electrical phenomena in the atmosphere, and the chemical composition of the air are carried out.
Data from ground stations are supplemented by observations on the oceans, where “weather ships” operate, constantly located in certain areas of the World Ocean, as well as meteorological information received from research and other ships.
In recent decades, an increasing amount of information about the atmosphere has been obtained using meteorological satellites, which carry instruments for photographing clouds and measuring fluxes of ultraviolet, infrared and microwave radiation from the Sun. Satellites make it possible to obtain information about vertical profiles of temperature, cloudiness and its water supply, elements of the radiation balance of the atmosphere, ocean surface temperature, etc. Using measurements of the refraction of radio signals from a system of navigation satellites, it is possible to determine vertical profiles of density, pressure and temperature, as well as moisture content in the atmosphere . With the help of satellites, it has become possible to clarify the value of the solar constant and planetary albedo of the Earth, build maps of the radiation balance of the Earth-atmosphere system, measure the content and variability of small atmospheric pollutants, and solve many other problems of atmospheric physics and environmental monitoring.
Lit.: Budyko M.I. Climate in the past and future. L., 1980; Matveev L. T. Course of general meteorology. Atmospheric physics. 2nd ed. L., 1984; Budyko M.I., Ronov A.B., Yanshin A.L. History of the atmosphere. L., 1985; Khrgian A. Kh. Atmospheric Physics. M., 1986; Atmosphere: Directory. L., 1991; Khromov S.P., Petrosyants M.A. Meteorology and climatology. 5th ed. M., 2001.
G. S. Golitsyn, N. A. Zaitseva.
The world around us is formed from three very different parts: earth, water and air. Each of them is unique and interesting in its own way. Now we will talk only about the last of them. What is atmosphere? How did it come about? What does it consist of and into what parts is it divided? All these questions are extremely interesting.
The name “atmosphere” itself is formed from two words of Greek origin, translated into Russian they mean “steam” and “ball”. And if you look at the exact definition, you can read the following: “The atmosphere is the air shell of the planet Earth, which rushes along with it in outer space.” It developed in parallel with the geological and geochemical processes that took place on the planet. And today all processes occurring in living organisms depend on it. Without an atmosphere, the planet would become a lifeless desert, like the Moon.
What does it consist of?
The question of what the atmosphere is and what elements are included in it has interested people for a long time. The main components of this shell were already known in 1774. They were installed by Antoine Lavoisier. He discovered that the composition of the atmosphere was largely composed of nitrogen and oxygen. Over time, its components were refined. And now it is known that it contains many other gases, as well as water and dust.
Let's take a closer look at what makes up the Earth's atmosphere near its surface. The most common gas is nitrogen. It contains slightly more than 78 percent. But, despite such a large amount, nitrogen is practically inactive in the air.
The next element in quantity and very important in importance is oxygen. This gas contains almost 21%, and it exhibits very high activity. Its specific function is to oxidize dead organic matter, which decomposes as a result of this reaction.
Low but important gases
The third gas that is part of the atmosphere is argon. It's a little less than one percent. After it come carbon dioxide with neon, helium with methane, krypton with hydrogen, xenon, ozone and even ammonia. But there are so few of them that the percentage of such components is equal to hundredths, thousandths and millionths. Of these, only carbon dioxide plays a significant role, since it is the building material that plants need for photosynthesis. Its other important function is to block radiation and absorb some of the sun's heat.
Another small but important gas, ozone exists to trap ultraviolet radiation coming from the Sun. Thanks to this property, all life on the planet is reliably protected. On the other hand, ozone affects the temperature of the stratosphere. Due to the fact that it absorbs this radiation, the air heats up.
The constancy of the quantitative composition of the atmosphere is maintained by non-stop mixing. Its layers move both horizontally and vertically. Therefore, anywhere on the globe there is enough oxygen and no excess carbon dioxide.
What else is in the air?
It should be noted that steam and dust can be found in the airspace. The latter consists of pollen and soil particles; in the city they are joined by impurities of solid emissions from exhaust gases.
But there is a lot of water in the atmosphere. Under certain conditions, it condenses and clouds and fog appear. In essence, these are the same thing, only the first ones appear high above the surface of the Earth, and the last one spreads along it. Clouds take different shapes. This process depends on the height above the Earth.
If they formed 2 km above land, then they are called layered. It is from them that rain pours on the ground or snow falls. Above them, cumulus clouds form up to a height of 8 km. They are always the most beautiful and picturesque. They are the ones who look at them and wonder what they look like. If such formations appear in the next 10 km, they will be very light and airy. Their name is feathery.
What layers is the atmosphere divided into?
Although they have very different temperatures from each other, it is very difficult to tell at what specific height one layer begins and the other ends. This division is very conditional and is approximate. However, the layers of the atmosphere still exist and perform their functions.
The lowest part of the air shell is called the troposphere. Its thickness increases as it moves from the poles to the equator from 8 to 18 km. This is the warmest part of the atmosphere because the air in it is heated by the earth's surface. Most of the water vapor is concentrated in the troposphere, which is why clouds form, precipitation falls, thunderstorms rumble and winds blow.
The next layer is about 40 km thick and is called the stratosphere. If an observer moves into this part of the air, he will find that the sky has turned purple. This is explained by the low density of the substance, which practically does not scatter the sun's rays. It is in this layer that jet planes fly. All open spaces are open for them, since there are practically no clouds. Inside the stratosphere there is a layer consisting of large amounts of ozone.
After it come the stratopause and mesosphere. The latter is about 30 km thick. It is characterized by a sharp decrease in air density and temperature. The sky appears black to the observer. Here you can even watch the stars during the day.
Layers in which there is practically no air
The structure of the atmosphere continues with a layer called the thermosphere - the longest of all the others, its thickness reaches 400 km. This layer is distinguished by its enormous temperature, which can reach 1700 °C.
The last two spheres are often combined into one and called the ionosphere. This is due to the fact that reactions occur in them with the release of ions. It is these layers that make it possible to observe such a natural phenomenon as the northern lights.
The next 50 km from the Earth are allocated to the exosphere. This is the outer shell of the atmosphere. It disperses air particles into space. Weather satellites usually move in this layer.
The Earth's atmosphere ends with the magnetosphere. It is she who sheltered most of the planet’s artificial satellites.
After all that has been said, there should be no questions left about what the atmosphere is. If you have doubts about its necessity, they can be easily dispelled.
The meaning of atmosphere
The main function of the atmosphere is to protect the planet's surface from overheating during the day and excessive cooling at night. The next important purpose of this shell, which no one will dispute, is to supply oxygen to all living beings. Without this they would suffocate.
Most meteorites burn up in the upper layers, never reaching the Earth's surface. And people can admire the flying lights, mistaking them for shooting stars. Without an atmosphere, the entire Earth would be littered with craters. And protection from solar radiation has already been discussed above.
How does a person influence the atmosphere?
Very negative. This is due to the growing activity of people. The main share of all negative aspects falls on industry and transport. By the way, it is cars that emit almost 60% of all pollutants that penetrate into the atmosphere. The remaining forty are divided between energy and industry, as well as waste disposal industries.
The list of harmful substances that daily replenish the air is very long. Due to transport in the atmosphere there are: nitrogen and sulfur, carbon, blue and soot, as well as a strong carcinogen that causes skin cancer - benzopyrene.
The industry accounts for the following chemical elements: sulfur dioxide, hydrocarbons and hydrogen sulfide, ammonia and phenol, chlorine and fluorine. If the process continues, then soon the answers to the questions: “What is the atmosphere? What does it consist of? will be completely different.
Atmosphere(from the Greek atmos - steam and spharia - ball) - the air shell of the Earth, rotating with it. The development of the atmosphere was closely related to the geological and geochemical processes occurring on our planet, as well as to the activities of living organisms.
The lower boundary of the atmosphere coincides with the surface of the Earth, since air penetrates into the smallest pores in the soil and is dissolved even in water.
The upper boundary at an altitude of 2000-3000 km gradually passes into outer space.
Thanks to the atmosphere, which contains oxygen, life on Earth is possible. Atmospheric oxygen is used in the breathing process of humans, animals, and plants.
If there were no atmosphere, the Earth would be as quiet as the Moon. After all, sound is the vibration of air particles. The blue color of the sky is explained by the fact that the sun's rays, passing through the atmosphere, like through a lens, are decomposed into their component colors. In this case, the rays of blue and blue colors are scattered the most.
The atmosphere traps most of the sun's ultraviolet radiation, which has a detrimental effect on living organisms. It also retains heat near the Earth's surface, preventing our planet from cooling.
The structure of the atmosphere
In the atmosphere, several layers can be distinguished, differing in density (Fig. 1).
Troposphere
Troposphere- the lowest layer of the atmosphere, the thickness of which above the poles is 8-10 km, in temperate latitudes - 10-12 km, and above the equator - 16-18 km.
Rice. 1. The structure of the Earth's atmosphere
The air in the troposphere is heated by the earth's surface, that is, by land and water. Therefore, the air temperature in this layer decreases with height by an average of 0.6 °C for every 100 m. At the upper boundary of the troposphere it reaches -55 °C. At the same time, in the region of the equator at the upper boundary of the troposphere, the air temperature is -70 °C, and in the region of the North Pole -65 °C.
About 80% of the mass of the atmosphere is concentrated in the troposphere, almost all the water vapor is located, thunderstorms, storms, clouds and precipitation occur, and vertical (convection) and horizontal (wind) movement of air occurs.
We can say that weather is mainly formed in the troposphere.
Stratosphere
Stratosphere- a layer of the atmosphere located above the troposphere at an altitude of 8 to 50 km. The color of the sky in this layer appears purple, which is explained by the thinness of the air, due to which the sun's rays are almost not scattered.
The stratosphere contains 20% of the mass of the atmosphere. The air in this layer is rarefied, there is practically no water vapor, and therefore almost no clouds and precipitation form. However, stable air currents are observed in the stratosphere, the speed of which reaches 300 km/h.
This layer is concentrated ozone(ozone screen, ozonosphere), a layer that absorbs ultraviolet rays, preventing them from reaching the Earth and thereby protecting living organisms on our planet. Thanks to ozone, the air temperature at the upper boundary of the stratosphere ranges from -50 to 4-55 °C.
Between the mesosphere and stratosphere there is a transition zone - the stratopause.
Mesosphere
Mesosphere- a layer of the atmosphere located at an altitude of 50-80 km. The air density here is 200 times less than at the Earth's surface. The color of the sky in the mesosphere appears black, and stars are visible during the day. The air temperature drops to -75 (-90)°C.
At an altitude of 80 km begins thermosphere. The air temperature in this layer rises sharply to a height of 250 m, and then becomes constant: at an altitude of 150 km it reaches 220-240 ° C; at an altitude of 500-600 km exceeds 1500 °C.
In the mesosphere and thermosphere, under the influence of cosmic rays, gas molecules disintegrate into charged (ionized) particles of atoms, so this part of the atmosphere is called ionosphere- a layer of very rarefied air, located at an altitude of 50 to 1000 km, consisting mainly of ionized oxygen atoms, nitrogen oxide molecules and free electrons. This layer is characterized by high electrification, and long and medium radio waves are reflected from it, like from a mirror.
In the ionosphere, aurorae appear - the glow of rarefied gases under the influence of electrically charged particles flying from the Sun - and sharp fluctuations in the magnetic field are observed.
Exosphere
Exosphere- the outer layer of the atmosphere located above 1000 km. This layer is also called the scattering sphere, since gas particles move here at high speed and can be scattered into outer space.
Atmospheric composition
The atmosphere is a mixture of gases consisting of nitrogen (78.08%), oxygen (20.95%), carbon dioxide (0.03%), argon (0.93%), a small amount of helium, neon, xenon, krypton (0.01%), ozone and other gases, but their content is negligible (Table 1). The modern composition of the Earth's air was established more than a hundred million years ago, but the sharply increased human production activity nevertheless led to its change. Currently, there is an increase in CO 2 content by approximately 10-12%.
The gases that make up the atmosphere perform various functional roles. However, the main significance of these gases is determined primarily by the fact that they very strongly absorb radiant energy and thereby have a significant impact on the temperature regime of the Earth's surface and atmosphere.
Table 1. Chemical composition of dry atmospheric air near the earth's surface
|
Volume concentration. % |
Molecular weight, units |
|
|
Oxygen |
||
|
Carbon dioxide |
||
|
Nitrous oxide |
||
|
from 0 to 0.00001 |
||
|
Sulfur dioxide |
from 0 to 0.000007 in summer; from 0 to 0.000002 in winter |
|
|
From 0 to 0.000002 |
46,0055/17,03061 |
|
|
Azog dioxide |
||
|
Carbon monoxide |
Nitrogen, The most common gas in the atmosphere, it is chemically inactive.
Oxygen, unlike nitrogen, is a chemically very active element. The specific function of oxygen is the oxidation of organic matter of heterotrophic organisms, rocks and under-oxidized gases emitted into the atmosphere by volcanoes. Without oxygen, there would be no decomposition of dead organic matter.
The role of carbon dioxide in the atmosphere is extremely large. It enters the atmosphere as a result of the processes of combustion, respiration of living organisms, and decay and is, first of all, the main building material for the creation of organic matter during photosynthesis. In addition, the ability of carbon dioxide to transmit short-wave solar radiation and absorb part of the thermal long-wave radiation is of great importance, which will create the so-called greenhouse effect, which will be discussed below.
Atmospheric processes, especially the thermal regime of the stratosphere, are also influenced by ozone. This gas serves as a natural absorber of ultraviolet radiation from the sun, and the absorption of solar radiation leads to heating of the air. Average monthly values of the total ozone content in the atmosphere vary depending on the latitude and time of year within the range of 0.23-0.52 cm (this is the thickness of the ozone layer at ground pressure and temperature). There is an increase in ozone content from the equator to the poles and an annual cycle with a minimum in autumn and a maximum in spring.
A characteristic property of the atmosphere is that the content of the main gases (nitrogen, oxygen, argon) changes slightly with altitude: at an altitude of 65 km in the atmosphere the content of nitrogen is 86%, oxygen - 19, argon - 0.91, at an altitude of 95 km - nitrogen 77, oxygen - 21.3, argon - 0.82%. The constancy of the composition of atmospheric air vertically and horizontally is maintained by its mixing.
In addition to gases, the air contains water vapor And solid particles. The latter can have both natural and artificial (anthropogenic) origin. These are pollen, tiny salt crystals, road dust, and aerosol impurities. When the sun's rays penetrate the window, they can be seen with the naked eye.
There are especially many particulate particles in the air of cities and large industrial centers, where emissions of harmful gases and their impurities formed during fuel combustion are added to aerosols.
The concentration of aerosols in the atmosphere determines the transparency of the air, which affects solar radiation reaching the Earth's surface. The largest aerosols are condensation nuclei (from lat. condensatio- compaction, thickening) - contribute to the transformation of water vapor into water droplets.
The importance of water vapor is determined primarily by the fact that it delays long-wave thermal radiation from the earth's surface; represents the main link of large and small moisture cycles; increases the air temperature during condensation of water beds.
The amount of water vapor in the atmosphere varies in time and space. Thus, the concentration of water vapor at the earth's surface ranges from 3% in the tropics to 2-10 (15)% in Antarctica.
The average content of water vapor in the vertical column of the atmosphere in temperate latitudes is about 1.6-1.7 cm (this is the thickness of the layer of condensed water vapor). Information regarding water vapor in different layers of the atmosphere is contradictory. It was assumed, for example, that in the altitude range from 20 to 30 km, specific humidity increases strongly with altitude. However, subsequent measurements indicate greater dryness of the stratosphere. Apparently, the specific humidity in the stratosphere depends little on altitude and is 2-4 mg/kg.
The variability of water vapor content in the troposphere is determined by the interaction of the processes of evaporation, condensation and horizontal transport. As a result of condensation of water vapor, clouds form and precipitation falls in the form of rain, hail and snow.
The processes of phase transitions of water occur predominantly in the troposphere, which is why clouds in the stratosphere (at altitudes of 20-30 km) and mesosphere (near the mesopause), called pearlescent and silvery, are observed relatively rarely, while tropospheric clouds often cover about 50% of the entire earth's surface. surfaces.
The amount of water vapor that can be contained in the air depends on the air temperature.
1 m 3 of air at a temperature of -20 ° C can contain no more than 1 g of water; at 0 °C - no more than 5 g; at +10 °C - no more than 9 g; at +30 °C - no more than 30 g of water.
Conclusion: The higher the air temperature, the more water vapor it can contain.
The air may be rich And not saturated water vapor. So, if at a temperature of +30 °C 1 m 3 of air contains 15 g of water vapor, the air is not saturated with water vapor; if 30 g - saturated.
Absolute humidity is the amount of water vapor contained in 1 m3 of air. It is expressed in grams. For example, if they say “absolute humidity is 15,” this means that 1 m L contains 15 g of water vapor.
Relative humidity- this is the ratio (in percentage) of the actual content of water vapor in 1 m 3 of air to the amount of water vapor that can be contained in 1 m L at a given temperature. For example, if the radio broadcast a weather report that the relative humidity is 70%, this means that the air contains 70% of the water vapor it can hold at that temperature.
The higher the relative humidity, i.e. The closer the air is to a state of saturation, the more likely precipitation is.
Always high (up to 90%) relative air humidity is observed in the equatorial zone, since the air temperature remains high there throughout the year and large evaporation occurs from the surface of the oceans. The relative humidity is also high in the polar regions, but because at low temperatures even a small amount of water vapor makes the air saturated or close to saturated. In temperate latitudes, relative humidity varies with the seasons - it is higher in winter, lower in summer.
The relative air humidity in deserts is especially low: 1 m 1 of air there contains two to three times less water vapor than is possible at a given temperature.
To measure relative humidity, a hygrometer is used (from the Greek hygros - wet and metreco - I measure).
When cooled, saturated air cannot retain the same amount of water vapor; it thickens (condenses), turning into droplets of fog. Fog can be observed in summer on a clear, cool night.
Clouds- this is the same fog, only it is formed not at the earth’s surface, but at a certain height. As the air rises, it cools and the water vapor in it condenses. The resulting tiny droplets of water make up clouds.
Cloud formation also involves particulate matter suspended in the troposphere.
Clouds can have different shapes, which depend on the conditions of their formation (Table 14).
The lowest and heaviest clouds are stratus. They are located at an altitude of 2 km from the earth's surface. At an altitude of 2 to 8 km, more picturesque cumulus clouds can be observed. The highest and lightest are cirrus clouds. They are located at an altitude of 8 to 18 km above the earth's surface.
|
Families |
Kinds of clouds |
Appearance |
|
A. Upper clouds - above 6 km |
I. Cirrus |
Thread-like, fibrous, white |
|
II. Cirrocumulus |
Layers and ridges of small flakes and curls, white |
|
|
III. Cirrostratus |
Transparent whitish veil |
|
|
B. Mid-level clouds - above 2 km |
IV. Altocumulus |
Layers and ridges of white and gray color |
|
V. Altostratified |
Smooth veil of milky gray color |
|
|
B. Low clouds - up to 2 km |
VI. Nimbostratus |
Solid shapeless gray layer |
|
VII. Stratocumulus |
Non-transparent layers and ridges of gray color |
|
|
VIII. Layered |
Non-transparent gray veil |
|
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D. Clouds of vertical development - from the lower to the upper tier |
IX. Cumulus |
Clubs and domes are bright white, with torn edges in the wind |
|
X. Cumulonimbus |
Powerful cumulus-shaped masses of dark lead color |
Atmospheric protection
The main sources are industrial enterprises and cars. In large cities, the problem of gas pollution on main transport routes is very acute. That is why many large cities around the world, including our country, have introduced environmental control of the toxicity of vehicle exhaust gases. According to experts, smoke and dust in the air can reduce the supply of solar energy to the earth's surface by half, which will lead to a change in natural conditions.