The thickness of the atmosphere is approximately 120 km from the Earth's surface. The total mass of air in the atmosphere is (5.1-5.3) 10 18 kg. Of these, the mass of dry air is 5.1352 ±0.0003 10 18 kg, the total mass of water vapor is on average 1.27 10 16 kg.
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 ° (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
Earth's atmosphere
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)
Up to an altitude of 100 km, the atmosphere is a homogeneous, well-mixed mixture of gases. In higher layers, the distribution of gases by height depends on their molecular masses; the concentration of heavier gases decreases faster with distance from the Earth's surface. Due to the decrease in gas density, the temperature drops from 0 °C in the stratosphere to −110 °C in the mesosphere. However, the kinetic energy of individual particles at altitudes of 200-250 km corresponds to a temperature of ~150 °C. Above 200 km, significant fluctuations in temperature and gas density in time and space are observed.
At an altitude of about 2000-3500 km, the exosphere gradually turns into the so-called near space vacuum, which is filled with highly rarefied particles of interplanetary gas, mainly hydrogen atoms. But this gas represents only part of the interplanetary matter. The other part consists of dust particles of cometary and meteoric origin. In addition to extremely rarefied dust particles, electromagnetic and corpuscular radiation of solar and galactic origin penetrates into this space.
The troposphere accounts for about 80% of the mass of the atmosphere, the stratosphere - about 20%; 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.
Physiological and other properties of the atmosphere
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.
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 passes 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 it was formed secondary atmosphere(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 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 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 N 2 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.
Noble gases
Air pollution
Recently, humans have 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 eras. 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 industrial activity. Over the past 100 years, the content of CO 2 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 CO 2 in the atmosphere will double and could lead to global climate change.
Fuel combustion is the main source of polluting gases (CO, SO2). Sulfur dioxide is oxidized by atmospheric oxygen to SO 3 in the upper layers of the atmosphere, which in turn interacts with water and ammonia vapor, and the resulting sulfuric acid (H 2 SO 4) and ammonium sulfate ((NH 4) 2 SO 4) are returned 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(CH 3 CH 2) 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.
see also
- Jacchia (atmosphere model)
Notes
Links
Literature
- V. V. Parin, F. P. Kosmolinsky, B. A. Dushkov“Space biology and medicine” (2nd edition, revised and expanded), M.: “Prosveshcheniye”, 1975, 223 pp.
- N. V. Gusakova“Environmental Chemistry”, Rostov-on-Don: Phoenix, 2004, 192 with ISBN 5-222-05386-5
- Sokolov V. A. Geochemistry of natural gases, M., 1971;
- McEwen M., Phillips L. Atmospheric Chemistry, M., 1978;
- Wark K., Warner S. Air pollution. Sources and control, trans. from English, M.. 1980;
- Monitoring of background pollution of natural environments. V. 1, L., 1982.
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The Earth's atmosphere is heterogeneous: at different altitudes there are different air densities and pressures, temperature and gas composition changes. Based on the behavior of the ambient air temperature (i.e., the temperature increases or decreases with height), the following layers are distinguished in it: troposphere, stratosphere, mesosphere, thermosphere and exosphere. The boundaries between layers are called pauses: there are 4 of them, because the upper boundary of the exosphere is very blurred and often refers to near space. The general structure of the atmosphere can be found in the attached diagram.
Fig.1 The structure of the Earth's atmosphere. Credit: website
The lowest atmospheric layer is the troposphere, the upper boundary of which, called the tropopause, varies depending on the geographic latitude and ranges from 8 km. in the polar up to 20 km. in tropical latitudes. In middle or temperate latitudes, its upper limit lies at altitudes of 10-12 km. During the year, the upper limit of the troposphere experiences fluctuations depending on the influx of solar radiation. Thus, as a result of sounding at the South Pole of the Earth by the US meteorological service, it was revealed that from March to August or September there is a steady cooling of the troposphere, as a result of which for a short period in August or September its boundary rises to 11.5 km. Then, in the period from September to December, it quickly decreases and reaches its lowest position - 7.5 km, after which its height remains virtually unchanged until March. Those. The troposphere reaches its greatest thickness in summer and its thinnest in winter.
It is worth noting that, in addition to seasonal ones, there are also daily fluctuations in the height of the tropopause. Also, its position is influenced by cyclones and anticyclones: in the first, it falls, because The pressure in them is lower than in the surrounding air, and secondly, it rises accordingly.
The troposphere contains up to 90% of the total mass of earth's air and 9/10 of all water vapor. Turbulence is highly developed here, especially in the near-surface and highest layers, clouds of all levels develop, cyclones and anticyclones form. And due to the accumulation of greenhouse gases (carbon dioxide, methane, water vapor) of sunlight reflected from the Earth's surface, the greenhouse effect develops.
The greenhouse effect is associated with a decrease in air temperature in the troposphere with height (since the heated Earth gives off more heat to the surface layers). The average vertical gradient is 0.65°/100 m (i.e., the air temperature decreases by 0.65° C for every 100 meters of rise). So, if the average annual air temperature at the surface of the Earth near the equator is +26°, then at the upper boundary it is -70°. The temperature in the tropopause region above the North Pole varies throughout the year from -45° in summer to -65° in winter.
With increasing altitude, air pressure also decreases, amounting to only 12-20% of the near-surface level at the upper boundary of the troposphere.
At the boundary of the troposphere and the overlying layer of the stratosphere lies a layer of the tropopause, 1-2 km thick. The lower boundaries of the tropopause are usually taken to be a layer of air in which the vertical gradient decreases to 0.2°/100 m versus 0.65°/100 m in the underlying regions of the troposphere.
Within the tropopause, air flows of a strictly defined direction are observed, called high-altitude jet streams or “jet streams”, formed under the influence of the rotation of the Earth around its axis and heating of the atmosphere with the participation of solar radiation. Currents are observed at the boundaries of zones with significant temperature differences. There are several centers of localization of these currents, for example, Arctic, subtropical, subpolar and others. Knowledge of the localization of jet streams is very important for meteorology and aviation: the first uses streams for more accurate weather forecasting, the second for constructing aircraft flight routes, because At the boundaries of the flows, there are strong turbulent vortices, similar to small whirlpools, called “clear-sky turbulence” due to the absence of clouds at these altitudes.
Under the influence of high-altitude jet currents, breaks often form in the tropopause, and at times it disappears altogether, although it then forms anew. This is especially often observed in subtropical latitudes, which are dominated by a powerful subtropical high-altitude current. In addition, the difference in tropopause layers in ambient temperature leads to the formation of gaps. For example, a large gap exists between the warm and low polar tropopause and the high and cold tropopause of tropical latitudes. Recently, a layer of the tropopause of temperate latitudes has also emerged, which has discontinuities with the previous two layers: polar and tropical.
The second layer of the earth's atmosphere is the stratosphere. The stratosphere can be roughly divided into two regions. The first of them, lying up to altitudes of 25 km, is characterized by almost constant temperatures, which are equal to the temperatures of the upper layers of the troposphere over a particular area. The second region, or inversion region, is characterized by an increase in air temperature to altitudes of approximately 40 km. This occurs due to the absorption of solar ultraviolet radiation by oxygen and ozone. In the upper part of the stratosphere, thanks to this heating, the temperature is often positive or even comparable to the temperature of the surface air.
Above the inversion region there is a layer of constant temperatures, which is called the stratopause and is the boundary between the stratosphere and mesosphere. Its thickness reaches 15 km.
Unlike the troposphere, turbulent disturbances are rare in the stratosphere, but there are strong horizontal winds or jet streams blowing in narrow zones along the boundaries of temperate latitudes facing the poles. The position of these zones is not constant: they can shift, expand, or even disappear altogether. Often jet streams penetrate into the upper layers of the troposphere, or, conversely, air masses from the troposphere penetrate into the lower layers of the stratosphere. Such mixing of air masses is especially typical in areas of atmospheric fronts.
There is little water vapor in the stratosphere. The air here is very dry, and therefore few clouds form. Only at altitudes of 20-25 km and in high latitudes can you notice very thin pearlescent clouds consisting of supercooled water droplets. During the day, these clouds are not visible, but with the onset of darkness they seem to glow due to the illumination of them by the Sun, which has already set below the horizon.
At the same altitudes (20-25 km) in the lower stratosphere there is the so-called ozone layer - the area with the highest content of ozone, which is formed under the influence of ultraviolet solar radiation (you can find out more about this process on the page). The ozone layer or ozonosphere is of extreme importance for maintaining the life of all organisms living on land, absorbing deadly ultraviolet rays with a wavelength of up to 290 nm. It is for this reason that living organisms do not live above the ozone layer; it is the upper limit of the distribution of life on Earth.
Under the influence of ozone, magnetic fields also change, atoms disintegrate, molecules disintegrate, ionization occurs, and new formation of gases and other chemical compounds occurs.
The layer of the atmosphere lying above the stratosphere is called the mesosphere. It is characterized by a decrease in air temperature with height with an average vertical gradient of 0.25-0.3°/100 m, which leads to severe turbulence. At the upper boundaries of the mesosphere, in the region called the mesopause, temperatures down to -138°C were recorded, which is the absolute minimum for the entire Earth's atmosphere as a whole.
Here, within the mesopause, lies the lower boundary of the region of active absorption of X-ray and short-wave ultraviolet radiation from the Sun. This energy process is called radiant heat transfer. As a result, the gas is heated and ionized, which causes the atmosphere to glow.
At altitudes of 75-90 km at the upper boundaries of the mesosphere, special clouds were noted, occupying vast areas in the polar regions of the planet. These clouds are called noctilucent because of their glow at dusk, which is caused by the reflection of sunlight from the ice crystals of which these clouds are composed.
Air pressure within the mesopause is 200 times less than at the earth's surface. This suggests that almost all the air in the atmosphere is concentrated in its 3 lower layers: the troposphere, stratosphere and mesosphere. The overlying layers, the thermosphere and exosphere, account for only 0.05% of the mass of the entire atmosphere.
The thermosphere lies at altitudes from 90 to 800 km above the Earth's surface.
The thermosphere is characterized by a continuous increase in air temperature to altitudes of 200-300 km, where it can reach 2500°C. The temperature rises due to the absorption of X-rays and short-wavelength ultraviolet radiation from the Sun by gas molecules. Above 300 km above sea level, the temperature increase stops.
Simultaneously with the increase in temperature, the pressure and, consequently, the density of the surrounding air decreases. So if at the lower boundaries of the thermosphere the density is 1.8 × 10 -8 g/cm 3, then at the upper boundaries it is already 1.8 × 10 -15 g/cm 3, which approximately corresponds to 10 million - 1 billion particles per 1 cm 3.
All characteristics of the thermosphere, such as the composition of air, its temperature, density, are subject to strong fluctuations: depending on the geographical location, season of the year and time of day. Even the location of the upper boundary of the thermosphere changes.
The uppermost layer of the atmosphere is called the exosphere or scattering layer. Its lower limit is constantly changing within very wide limits; The average height is taken to be 690-800 km. It is installed where the probability of intermolecular or interatomic collisions can be neglected, i.e. the average distance that a chaotically moving molecule will cover before colliding with another similar molecule (the so-called free path) will be so great that in fact the molecules will not collide with a probability close to zero. The layer where the described phenomenon occurs is called thermal pause.
The upper boundary of the exosphere lies at altitudes of 2-3 thousand km. It is greatly blurred and gradually turns into a near-space vacuum. Sometimes, for this reason, the exosphere is considered part of outer space, and its upper limit is taken to be a height of 190 thousand km, at which the influence of solar radiation pressure on the speed of hydrogen atoms exceeds the gravitational attraction of the Earth. This is the so-called the earth's crown, consisting of hydrogen atoms. The density of the earth's corona is very small: only 1000 particles per cubic centimeter, but this number is more than 10 times higher than the concentration of particles in interplanetary space.
Due to the extreme rarefaction of the air in the exosphere, particles move around the Earth in elliptical orbits without colliding with each other. Some of them, moving along open or hyperbolic trajectories at cosmic speeds (hydrogen and helium atoms), leave the atmosphere and go into outer space, which is why the exosphere is called the scattering sphere.
Encyclopedic YouTube
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Subtitles
Atmospheric boundary
The atmosphere is considered to be that region around the Earth in which the gaseous medium rotates together with the Earth as a single whole. The atmosphere passes into interplanetary space gradually, in the exosphere, starting at an altitude of 500-1000 km from the Earth's surface.
According to the definition proposed by the International Aviation Federation, the boundary of the atmosphere and space is drawn along the Karman line, located at an altitude of about 100 km, above which aviation flights become completely impossible. NASA uses the 122 kilometers (400,000 ft) mark as the atmospheric limit, where the shuttles switch from powered maneuvering to aerodynamic maneuvering.
Physical properties
In addition to the gases indicated in the table, the atmosphere contains Cl 2 (\displaystyle (\ce (Cl2))) , SO 2 (\displaystyle (\ce (SO2))) , NH 3 (\displaystyle (\ce (NH3))) , CO (\displaystyle ((\ce (CO)))) , O 3 (\displaystyle ((\ce (O3)))) , NO 2 (\displaystyle (\ce (NO2))), hydrocarbons, HCl (\displaystyle (\ce (HCl))) , HF (\displaystyle (\ce (HF))) , HBr (\displaystyle (\ce (HBr))) , HI (\displaystyle ((\ce (HI)))), couples Hg (\displaystyle (\ce (Hg))) , I 2 (\displaystyle (\ce (I2))) , Br 2 (\displaystyle (\ce (Br2))), as well as many other gases in small quantities. The troposphere constantly contains a large amount of suspended solid and liquid particles (aerosol). The rarest gas in the Earth's atmosphere is Rn (\displaystyle (\ce (Rn))) .
The structure of the atmosphere
Atmospheric boundary layer
The lower layer of the troposphere (1-2 km thick), in which the state and properties of the Earth's surface directly affect the dynamics 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 appear, and cyclones and anticyclones develop. Temperature decreases with increasing altitude with an average vertical gradient of 0.65°/100 meters.
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 the 25-40 km layer from minus 56.5 to plus 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
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 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 above the thermosphere. In this region, the absorption of solar radiation is negligible and the temperature does not actually change with altitude.
Exosphere (scattering sphere)
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 minus 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 rare 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.
Review
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 electrical properties in the atmosphere, they distinguish neutrosphere And ionosphere .
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.
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.
History of atmospheric formation
According to the most common theory, the Earth's atmosphere has had three different compositions throughout its history. 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 (carbon dioxide, 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:
- 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 is due to the oxidation of the ammonia-hydrogen atmosphere by molecular oxygen O 2 (\displaystyle (\ce (O2))), which began to come from the surface of the planet as a result of photosynthesis, starting 3 billion years ago. Also nitrogen N 2 (\displaystyle (\ce (N2))) released into the atmosphere as a result of denitrification of nitrates and other nitrogen-containing compounds. Nitrogen is oxidized by ozone to NO (\displaystyle ((\ce (NO)))) in the upper layers of the atmosphere.
Nitrogen N 2 (\displaystyle (\ce (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, which form rhizobial symbiosis with leguminous plants, which can be effective green manures - plants that do not deplete, but enrich the soil with natural fertilizers, can oxidize it with low energy consumption and convert it into a biologically active form.
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 and others. 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.
Noble gases
Air pollution
Recently, humans have begun to influence the evolution of the atmosphere. The result of human activity has been a constant increase in the content of carbon dioxide in the atmosphere due to the combustion of hydrocarbon fuels accumulated in previous geological eras. Enormous quantities are consumed during photosynthesis and are 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 last 100 years content CO 2 (\displaystyle (\ce (CO2))) in the atmosphere 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 CO 2 (\displaystyle (\ce (CO2))) in the atmosphere will double and may lead to
Everyone who has flown on an airplane is accustomed to this kind of message: “our flight takes place at an altitude of 10,000 m, the temperature outside is 50 ° C.” It seems nothing special. The farther from the surface of the Earth heated by the Sun, the colder it is. Many people think that the temperature decreases continuously with altitude and that the temperature gradually drops, approaching the temperature of space. By the way, scientists thought so until the end of the 19th century.
Let's take a closer look at the distribution of air temperature over the Earth. The atmosphere is divided into several layers, which primarily reflect the nature of temperature changes.
The lower layer of the atmosphere is called troposphere, which means “sphere of rotation.” All changes in weather and climate are the result of physical processes occurring precisely in this layer. The upper boundary of this layer is located where the decrease in temperature with height is replaced by its increase - approximately at an altitude of 15-16 km above the equator and 7-8 km above the poles. Like the Earth itself, the atmosphere, under the influence of the rotation of our planet, is also somewhat flattened above the poles and swells above the equator. However, this effect is much more pronounced in the atmosphere than in the solid shell of the Earth in the direction from the Earth's surface to. At the upper boundary of the troposphere, the air temperature decreases. Above the equator, the minimum air temperature is about -62 ° C, and above the poles - about -45 ° C. In temperate latitudes, more than 75% of the mass of the atmosphere is in the troposphere. In the tropics, about 90% is located within the troposphere. mass of the atmosphere.
In 1899, a minimum was found in the vertical temperature profile at a certain altitude, and then the temperature increased slightly. The beginning of this increase means the transition to the next layer of the atmosphere - to stratosphere, which means “layer sphere.” The term stratosphere means and reflects the previous idea of the uniqueness of the layer lying above the troposphere. The stratosphere extends to an altitude of about 50 km above the earth’s surface. Its peculiarity is, in particular, a sharp increase in air temperature. This increase in temperature is explained ozone formation reaction is one of the main chemical reactions occurring in the atmosphere.
The bulk of ozone is concentrated at altitudes of approximately 25 km, but in general the ozone layer is a highly extended shell, covering almost the entire stratosphere. The interaction of oxygen with ultraviolet rays is one of the beneficial processes in the earth’s atmosphere that contributes to the maintenance of life on Earth. The absorption of this energy by ozone prevents its excessive flow to the earth's surface, where exactly the level of energy that is suitable for the existence of terrestrial life forms is created. The ozonosphere absorbs some of the radiant energy passing through the atmosphere. As a result, a vertical air temperature gradient of approximately 0.62°C per 100 m is established in the ozonosphere, i.e., the temperature increases with altitude up to the upper limit of the stratosphere - the stratopause (50 km), reaching, according to some data, 0°C.
At altitudes from 50 to 80 km there is a layer of the atmosphere called mesosphere. The word "mesosphere" means "intermediate sphere", where the air temperature continues to decrease with height. Above the mesosphere, in a layer called thermosphere, the temperature rises again with altitude up to about 1000°C, and then drops very quickly to -96°C. However, it does not drop indefinitely, then the temperature increases again.
Thermosphere is the first layer ionosphere. Unlike the previously mentioned layers, the ionosphere is not distinguished by temperature. The ionosphere is an area of electrical nature that makes many types of radio communications possible. The ionosphere is divided into several layers, designated by the letters D, E, F1 and F2. These layers also have special names. The separation into layers is caused by several reasons, among which the most important is the unequal influence of the layers on the passage of radio waves. The lowest layer, D, mainly absorbs radio waves and thereby prevents their further propagation. The best studied layer E is located at an altitude of approximately 100 km above the earth's surface. It is also called the Kennelly-Heaviside layer after the names of the American and English scientists who simultaneously and independently discovered it. Layer E, like a giant mirror, reflects radio waves. Thanks to this layer, long radio waves travel further distances than would be expected if they propagated only in a straight line, without being reflected from the E layer. The F layer has similar properties. It is also called the Appleton layer. Together with the Kennelly-Heaviside layer, it reflects radio waves to terrestrial radio stations. Such reflection can occur at various angles. The Appleton layer is located at an altitude of about 240 km.
The outermost region of the atmosphere, the second layer of the ionosphere, is often called exosphere. This term refers to the existence of the outskirts of space near the Earth. It is difficult to determine exactly where the atmosphere ends and space begins, since with altitude the density of atmospheric gases gradually decreases and the atmosphere itself gradually turns into almost a vacuum, in which only individual molecules are found. Already at an altitude of approximately 320 km, the density of the atmosphere is so low that molecules can travel more than 1 km without colliding with each other. The outermost part of the atmosphere serves as its upper boundary, which is located at altitudes from 480 to 960 km.
More information about processes in the atmosphere can be found on the website “Earth Climate”
- the air shell of the globe, rotating together with the Earth. The upper boundary of the atmosphere is conventionally drawn at altitudes of 150-200 km. The lower boundary is the Earth's surface.
Atmospheric air is a mixture of gases. Most of its volume in the surface layer of air accounts for nitrogen (78%) and oxygen (21%). In addition, the air contains inert gases (argon, helium, neon, etc.), carbon dioxide (0.03), water vapor and various solid particles (dust, soot, salt crystals).
The air is colorless, and the color of the sky is explained by the characteristics of the scattering of light waves.
The atmosphere consists of several layers: the troposphere, stratosphere, mesosphere and thermosphere.
The lower ground layer of air is called troposphere. At different latitudes its power is not the same. The troposphere follows the shape of the planet and participates together with the Earth in axial rotation. At the equator, the thickness of the atmosphere varies from 10 to 20 km. At the equator it is greater, and at the poles it is less. The troposphere is characterized by maximum air density; 4/5 of the mass of the entire atmosphere is concentrated in it. The troposphere determines weather conditions: various air masses form here, clouds and precipitation form, and intense horizontal and vertical air movement occurs.
Above the troposphere, up to an altitude of 50 km, is located stratosphere. It is characterized by lower air density and lacks water vapor. In the lower part of the stratosphere at altitudes of about 25 km. there is an “ozone screen” - a layer of the atmosphere with a high concentration of ozone, which absorbs ultraviolet radiation, which is fatal to organisms.
At an altitude of 50 to 80-90 km it extends mesosphere. With increasing altitude, the temperature decreases with an average vertical gradient of (0.25-0.3)°/100 m, and the air density decreases. The main energy process is radiant heat transfer. The atmospheric glow is caused by complex photochemical processes involving radicals and vibrationally excited molecules.
Thermosphere located at an altitude of 80-90 to 800 km. The air density here is minimal, and the degree of air ionization is very high. Temperature changes depending on the activity of the Sun. Due to the large number of charged particles, auroras and magnetic storms are observed here.
The atmosphere is of great importance for the nature of the Earth. Without oxygen, living organisms cannot breathe. Its ozone layer protects all living things from harmful ultraviolet rays. The atmosphere smoothes out temperature fluctuations: the Earth's surface does not get supercooled at night and does not overheat during the day. In dense layers of atmospheric air, before reaching the surface of the planet, meteorites burn from thorns.
The atmosphere interacts with all layers of the earth. With its help, heat and moisture are exchanged between the ocean and land. Without the atmosphere there would be no clouds, precipitation, or winds.
Human economic activities have a significant adverse impact on the atmosphere. Atmospheric air pollution occurs, which leads to an increase in the concentration of carbon monoxide (CO 2). And this contributes to global warming and increases the “greenhouse effect”. The Earth's ozone layer is destroyed due to industrial waste and transport.
The atmosphere needs protection. In developed countries, a set of measures is being implemented to protect atmospheric air from pollution.
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