Atmosphere (from Greek ατμός - “steam” and σφαῖρα - “sphere”) - gas shell celestial body, held near it by gravity. The atmosphere is the gaseous shell of the planet, consisting of a mixture of various gases, water vapor and dust. The atmosphere exchanges matter between the Earth and the Cosmos. The Earth receives cosmic dust and meteorite material, and loses the lightest gases: hydrogen and helium. The Earth's atmosphere is penetrated through and through by powerful radiation from the Sun, which determines the thermal regime of the planet's surface, causing the dissociation of molecules of atmospheric gases and the ionization of atoms.
The Earth's atmosphere contains oxygen, used by most living organisms for respiration, and carbon dioxide, consumed by plants, algae and cyanobacteria during photosynthesis. The atmosphere is also a protective layer of the planet, protecting its inhabitants from solar ultraviolet radiation.
All massive bodies - terrestrial planets and gas giants - have an atmosphere.
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%), 0.038% carbon dioxide, and not a large number of hydrogen, helium, other noble gases and pollutants.
Modern composition 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 included in 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.
Initial composition A planet's atmosphere usually depends on the chemical and temperature properties of the sun during the formation of planets and the subsequent release of external gases. Then the composition of the gas shell evolves under the influence of various factors.
The atmospheres of Venus and Mars are primarily composed of carbon dioxide with minor additions of nitrogen, argon, oxygen and other gases. Earth's atmosphere in to a large extent is a product of organisms living in it. The low-temperature gas giants - Jupiter, Saturn, Uranus and Neptune - can retain mainly low molecular weight gases - hydrogen and helium. High-temperature gas giants, such as Osiris or 51 Pegasi b, on the contrary, cannot hold it and the molecules of their atmosphere are scattered in space. This process occurs slowly and constantly.
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.
Atmospheric structure
The structure of the atmosphere consists of two parts: the inner one - the troposphere, stratosphere, mesosphere and thermosphere, or ionosphere, and the outer one - the magnetosphere (exosphere).
1) Troposphere– this is the lower part of the atmosphere in which 3/4 i.e. is concentrated. ~ 80% of the entire earth's atmosphere. Its height is determined by the intensity of vertical (ascending or descending) air flows caused by heating of the earth's surface and ocean, therefore the thickness of the troposphere at the equator is 16–18 km, in temperate latitudes 10–11 km, and at the poles – up to 8 km. The air temperature in the troposphere at altitude decreases by 0.6ºС for every 100 m and ranges from +40 to - 50ºС.
2)Stratosphere is located above the troposphere and has a height of up to 50 km from the surface of the planet. The temperature at an altitude of up to 30 km is constant -50ºС. Then it begins to rise and at an altitude of 50 km reaches +10ºС.
The upper boundary of the biosphere is the ozone screen.
The ozone screen is a layer of the atmosphere within the stratosphere, located at different heights from the Earth's surface and having a maximum ozone density at an altitude of 20-26 km.
The height of the ozone layer at the poles is estimated at 7-8 km, at the equator at 17-18 km, and the maximum height of ozone presence is 45-50 km. Life above the ozone shield is impossible due to the harsh ultraviolet radiation of the Sun. If you compress all the ozone molecules, you will get a ~ 3mm layer around the planet.
3) Mesosphere– the upper boundary of this layer is located up to a height of 80 km. Its main feature is a sharp drop in temperature -90ºС at its upper limit. Noctilucent clouds consisting of ice crystals are recorded here.
4) Ionosphere (thermosphere) - is located up to an altitude of 800 km and is characterized by a significant increase in temperature:
150 km temperature +240ºС,
200 km temperature +500ºС,
600 km temperature +1500ºС.
Under the influence of ultraviolet radiation from the Sun, gases are in an ionized state. Ionization is associated with the glow of gases and the appearance of auroras.
The ionosphere has the ability to repeatedly reflect radio waves, which ensures long-distance radio communications on the planet.
5) Exosphere– is located above 800 km and extends up to 3000 km. Here the temperature is >2000ºС. The speed of gas movement is approaching critical ~ 11.2 km/sec. The dominant atoms are hydrogen and helium, which form a luminous corona around the Earth, extending to an altitude of 20,000 km.
Functions of the atmosphere
1) Thermoregulatory - weather and climate on Earth depend on the distribution of heat and pressure.
2) Life-sustaining.
3) In the troposphere, global vertical and horizontal movements of air masses occur, which determine the water cycle and heat exchange.
4) Almost all surfaces geological processes are caused by the interaction of the atmosphere, lithosphere and hydrosphere.
5) Protective - the atmosphere protects the earth from space, solar radiation and meteorite dust.
Functions of the atmosphere. Without the atmosphere, life on Earth would be impossible. A person consumes 12-15 kg daily. air, inhaling every minute from 5 to 100 liters, which significantly exceeds the average daily need for food and water. In addition, the atmosphere reliably protects people from dangers that threaten them from space: it does not allow meteorites or cosmic radiation to pass through. A person can live without food for five weeks, without water for five days, without air for five minutes. Normal human life requires not only air, but also a certain purity of it. The health of people, the state of flora and fauna, the strength and durability of building structures and structures depend on the air quality. Polluted air is destructive to waters, land, seas, and soils. The atmosphere determines the light and regulates the thermal regimes of the earth, contributes to the redistribution of heat on the globe. The gas shell protects the Earth from excessive cooling and heating. If our planet were not surrounded by an air shell, then within one day the amplitude of temperature fluctuations would reach 200 C. The atmosphere saves everything living on Earth from destructive ultraviolet, x-rays and cosmic rays. The atmosphere plays a great role in the distribution of light. Its air breaks the sun's rays into a million small rays, scatters them and creates uniform illumination. The atmosphere serves as a conductor of sounds.
The structure of the Earth's atmosphere
The atmosphere is the gaseous shell of the Earth with the aerosol particles it contains, moving together with the Earth in space as a single whole and at the same time taking part in the rotation of the Earth. Most of our life takes place at the bottom of the atmosphere.
Almost all of our planets have their own atmospheres. solar system, but only the earth's atmosphere is capable of supporting life.
When our planet formed 4.5 billion years ago, it was apparently devoid of an atmosphere. The atmosphere was formed as a result of volcanic emissions of water vapor mixed with carbon dioxide, nitrogen and other chemical substances from the depths of the young planet. But the atmosphere may contain limited quantity moisture, so its excess as a result of condensation gave rise to the oceans. But then the atmosphere was devoid of oxygen. The first living organisms that originated and developed in the ocean, as a result of the photosynthesis reaction (H 2 O + CO 2 = CH 2 O + O 2), began to release small portions of oxygen, which began to enter the atmosphere.
The formation of oxygen in the Earth's atmosphere led to the formation of the ozone layer at altitudes of approximately 8 – 30 km. And, thus, our planet has acquired protection from the harmful effects of ultraviolet study. This circumstance served as an impetus for further evolution life forms on Earth, because As a result of increased photosynthesis, the amount of oxygen in the atmosphere began to grow rapidly, which contributed to the formation and maintenance of life forms, including on land.
Today our atmosphere consists of 78.1% nitrogen, 21% oxygen, 0.9% argon, and 0.04% carbon dioxide. Very small fractions compared to the main gases are neon, helium, methane, and krypton.
The gas particles contained in the atmosphere are affected by the force of gravity of the Earth. And, given that air is compressible, its density gradually decreases with height, passing into outer space without a clear boundary. Half of the total mass of the earth's atmosphere is concentrated in the lower 5 km, three quarters in the lower 10 km, nine tenths in the lower 20 km. 99% of the mass of the Earth's atmosphere is concentrated below an altitude of 30 km, which is only 0.5% of the equatorial radius of our planet.
At sea level, the number of atoms and molecules per cubic centimeter of air is about 2 * 10 19, at an altitude of 600 km only 2 * 10 7. At sea level, an atom or molecule travels approximately 7 * 10 -6 cm before colliding with another particle. At an altitude of 600 km this distance is about 10 km. And at sea level, about 7 * 10 9 such collisions occur every second, at an altitude of 600 km - only about one per minute!
But not only pressure changes with altitude. The temperature also changes. So, for example, at the foot high mountain It can be quite hot, while the top of the mountain is covered with snow and the temperature there at the same time is below zero. And as soon as you fly to an altitude of about 10–11 km, you can hear a message that it is -50 degrees outside, while at the surface of the earth it is 60–70 degrees warmer...
Initially, scientists assumed that the temperature decreases with height until it reaches absolute zero (-273.16°C). But that's not true.
The Earth's atmosphere consists of four layers: troposphere, stratosphere, mesosphere, ionosphere (thermosphere). This division into layers was also adopted based on data on temperature changes with height. The lowest layer, where air temperature decreases with height, is called the troposphere. The layer above the troposphere, where the temperature drop stops, is replaced by isotherm, and finally the temperature begins to rise, is called the stratosphere. The layer above the stratosphere in which the temperature rapidly drops again is the mesosphere. And finally, the layer where the temperature begins to rise again was called the ionosphere or thermosphere.
The troposphere extends on average to the lower 12 km. This is where our weather is formed. The highest clouds (cirrus) form in the uppermost layers of the troposphere. The temperature in the troposphere decreases adiabatically with height, i.e. The temperature change occurs due to the decrease in pressure with height. The temperature profile of the troposphere is largely determined by solar radiation reaching the Earth's surface. As a result of heating the Earth's surface by the Sun, convective and turbulent flows are formed, directed upward, which form the weather. It is worth noting that the influence of the underlying surface on the lower layers of the troposphere extends to a height of approximately 1.5 km. Of course, excluding mountainous areas.
The upper boundary of the troposphere is the tropopause - an isothermal layer. Remember characteristic appearance thunderclouds, the top of which is a "throw" cirrus clouds, called the "anvil". This “anvil” just “spreads” under the tropopause, because due to isotherm, the ascending air currents are significantly weakened, and the cloud stops developing vertically. But in special, rare cases, the tops of cumulonimbus clouds can invade the lower layers of the stratosphere, breaking the tropopause.
The height of the tropopause depends on latitude. Thus, at the equator it is located at an altitude of approximately 16 km, and its temperature is about –80°C. At the poles, the tropopause is located lower, at approximately 8 km altitude. In summer the temperature here is –40°C, and –60°C in winter. Thus, despite higher temperatures at the Earth's surface, the tropical tropopause is much colder than at the poles.
Blue planet...
This topic should have been one of the first to appear on the site. After all, helicopters are atmospheric aircraft. Earth's atmosphere– their habitat, so to speak:-). A physical properties air This is precisely what determines the quality of this habitat :-). That is, this is one of the basics. And they always write about the basis first. But I realized this only now. However, as you know, it’s better late than never... Let’s touch on this issue, without getting into the weeds and unnecessary complications :-).
So… Earth's atmosphere. This is the gaseous shell of our blue planet. Everyone knows this name. Why blue? Simply because the “blue” (and blue and violet) component sunlight(spectrum) is most well scattered in the atmosphere, thereby coloring it bluish-bluish, sometimes with a hint of violet tone (on a sunny day, of course :-)).
Composition of the Earth's atmosphere.
The composition of the atmosphere is quite broad. I will not list all the components in the text; there is a good illustration for this. The composition of all these gases is almost constant, with the exception of carbon dioxide (CO 2 ). In addition, the atmosphere necessarily contains water in the form of vapor, suspended droplets or ice crystals. The amount of water is not constant and depends on temperature and, to a lesser extent, air pressure. In addition, the Earth’s atmosphere (especially the current one) contains a certain amount of, I would say, “all sorts of nasty things” :-). These are SO 2, NH 3, CO, HCl, NO, in addition there are mercury vapors Hg. True, all this is there in small quantities, thank God :-).
Earth's atmosphere It is customary to divide it into several successive zones in height above the surface.
The first, closest to the earth, is the troposphere. This is the lowest and, so to speak, main layer for life. different types. It contains 80% of the mass of all atmospheric air (although by volume it is only about 1% of the entire atmosphere) and about 90% of all atmospheric water. The bulk of all the winds, clouds, rain and snow 🙂 come from there. The troposphere extends to altitudes of about 18 km in tropical latitudes and up to 10 km in polar latitudes. The air temperature in it decreases with an increase in height by approximately 0.65º for every 100 m.
Atmospheric zones.
Zone two - stratosphere. It must be said that between the troposphere and the stratosphere there is another narrow zone - the tropopause. It stops the temperature falling with height. The tropopause has an average thickness of 1.5-2 km, but its boundaries are unclear and the troposphere often overlaps the stratosphere.
So the stratosphere has an average height of 12 km to 50 km. The temperature in it remains unchanged up to 25 km (about -57ºС), then somewhere up to 40 km it rises to approximately 0ºС and then remains unchanged up to 50 km. The stratosphere is a relatively calm part of the earth's atmosphere. There are practically no adverse weather conditions in it. It is in the stratosphere that the famous ozone layer is located at altitudes from 15-20 km to 55-60 km.
This is followed by a small boundary layer, the stratopause, in which the temperature remains around 0ºC, and then the next zone is the mesosphere. It extends to altitudes of 80-90 km, and in it the temperature drops to about 80ºC. In the mesosphere, small meteors usually become visible, which begin to glow in it and burn up there.
The next narrow interval is the mesopause and beyond it the thermosphere zone. Its height is up to 700-800 km. Here the temperature begins to rise again and at altitudes of about 300 km can reach values of the order of 1200ºС. Then it remains constant. Inside the thermosphere, up to an altitude of about 400 km, is the ionosphere. Here the air is highly ionized due to exposure to solar radiation and has high electrical conductivity.
The next and, in general, the last zone is the exosphere. This is the so-called scattering zone. Here, there is mainly very rarefied hydrogen and helium (with a predominance of hydrogen). At altitudes of about 3000 km, the exosphere passes into the near-space vacuum.
Something like this. Why approximately? Because these layers are quite conventional. Various changes in altitude, composition of gases, water, temperature, ionization, and so on are possible. In addition, there are many more terms that define the structure and state of the earth’s atmosphere.
For example, homosphere and heterosphere. In the first, atmospheric gases are well mixed and their composition is quite homogeneous. The second is located above the first and there is practically no such mixing there. The gases in it are separated by gravity. The boundary between these layers is located at an altitude of 120 km, and it is called turbopause.
Let’s finish with the terms, but I’ll definitely add that it is conventionally accepted that the boundary of the atmosphere is located at an altitude of 100 km above sea level. This border is called the Karman Line.
I will add two more pictures to illustrate the structure of the atmosphere. The first one, however, is in German, but it is complete and quite easy to understand :-). It can be enlarged and seen clearly. The second shows the change in atmospheric temperature with altitude.
The structure of the Earth's atmosphere.
Air temperature changes with altitude.
Modern manned orbital spacecraft fly at altitudes of about 300-400 km. However, this is no longer aviation, although the area, of course, is in a certain sense closely related, and we will definitely talk about her later :-).
The aviation zone is the troposphere. Modern atmospheric aircraft can also fly in the lower layers of the stratosphere. For example, the practical ceiling of the MIG-25RB is 23,000 m.
Flight in the stratosphere.
And exactly physical properties of air The troposphere determines what the flight will be like, how effective the aircraft’s control system will be, how turbulence in the atmosphere will affect it, and how the engines will operate.
The first main property is air temperature. In gas dynamics, it can be determined on the Celsius scale or on the Kelvin scale.
Temperature t 1 at a given height N on the Celsius scale is determined by:
t 1 = t - 6.5N, Where t– air temperature near the ground.
Temperature on the Kelvin scale is called absolute temperature, zero on this scale is absolute zero. At absolute zero The thermal movement of molecules stops. Absolute zero on the Kelvin scale corresponds to -273º on the Celsius scale.
Accordingly the temperature T on high N on the Kelvin scale is determined by:
T = 273K + t - 6.5H
Air pressure. Atmospheric pressure is measured in Pascals (N/m2), in the old system of measurement in atmospheres (atm.). There is also such a thing as barometric pressure. This is the pressure measured in millimeters of mercury using a mercury barometer. Barometric pressure (pressure at sea level) equal to 760 mmHg. Art. called standard. In physics 1 atm. exactly equal to 760 mm Hg.
Air density. In aerodynamics, the concept most often used is the mass density of air. This is the mass of air in 1 m3 of volume. The density of air changes with altitude, the air becomes more rarefied.
Air humidity. Shows the amount of water in the air. There is a concept " relative humidity" This is the ratio of the mass of water vapor to the maximum possible at a given temperature. The concept of 0%, that is, when the air is completely dry, can exist, in general, only in the laboratory. On the other hand, 100% humidity is quite possible. This means that the air has absorbed all the water it could absorb. Something like an absolutely “full sponge”. High relative humidity reduces air density, and low relative humidity increases it.
Due to the fact that aircraft flights occur under different atmospheric conditions, their flight and aerodynamic parameters in the same flight mode may be different. Therefore, to correctly estimate these parameters, we introduced International Standard Atmosphere (ISA). It shows the change in the state of air with increasing altitude.
The basic parameters of the air condition at zero humidity are taken as follows:
pressure P = 760 mm Hg. Art. (101.3 kPa);
temperature t = +15°C (288 K);
mass density ρ = 1.225 kg/m 3 ;
For the ISA it is accepted (as mentioned above :-)) that the temperature drops in the troposphere by 0.65º for every 100 meters of altitude.
Standard atmosphere (example up to 10,000 m).
MSA tables are used for calibrating instruments, as well as for navigational and engineering calculations.
Physical properties of air also include such concepts as inertia, viscosity and compressibility.
Inertia is a property of air that characterizes its ability to resist changes in its state of rest or uniform linear motion. . A measure of inertia is the mass density of air. The higher it is, the higher the inertia and resistance force of the medium when the aircraft moves in it.
Viscosity Determines the air friction resistance when the aircraft is moving.
Compressibility determines the change in air density with changes in pressure. At low speeds aircraft(up to 450 km/h) changes in pressure when flowing around it air flow does not happen, but when high speeds The compressibility effect begins to appear. Its influence is especially noticeable at supersonic speeds. This is a separate area of aerodynamics and a topic for a separate article :-).
Well, that seems to be all for now... It's time to finish this slightly tedious enumeration, which, however, cannot be avoided :-). Earth's atmosphere, its parameters, physical properties of air are as important for the aircraft as the parameters of the device itself, and they could not be ignored.
Bye, until next meetings and more interesting topics :) ...
P.S. For dessert, I suggest watching a video filmed from the cockpit of a MIG-25PU twin during its flight into the stratosphere. Apparently it was filmed by a tourist who has money for such flights :-). Filmed mostly through Windshield. Pay attention to the color of the sky...
The atmosphere is air envelope Earth. Extending up to 3000 km from the earth's surface. Its traces can be traced to altitudes of up to 10,000 km. A. has an uneven density 50 5 its masses are concentrated up to 5 km, 75% - up to 10 km, 90% - up to 16 km.
The atmosphere consists of air - a mechanical mixture of several gases.
Nitrogen(78%) in the atmosphere plays the role of an oxygen diluent, regulating the rate of oxidation, and, consequently, the speed and intensity of biological processes. Nitrogen is the main element of the earth’s atmosphere, which continuously exchanges with living matter of the biosphere, and the constituent parts of the latter are nitrogen compounds (amino acids, purines, etc.). Nitrogen is extracted from the atmosphere by inorganic and biochemical routes, although they are closely interrelated. Inorganic extraction is associated with the formation of its compounds N 2 O, N 2 O 5, NO 2, NH 3. They are found in precipitation and are formed in the atmosphere under the influence of electrical discharges during thunderstorms or photos chemical reactions under the influence of solar radiation.
Biological fixation of nitrogen is carried out by some bacteria in symbiosis with higher plants in soils. Nitrogen is also fixed by some plankton microorganisms and algae in marine environment. Quantitatively, the biological fixation of nitrogen exceeds its inorganic fixation. The exchange of all nitrogen in the atmosphere occurs within approximately 10 million years. Nitrogen is found in gases of volcanic origin and in igneous rocks. When various samples of crystalline rocks and meteorites are heated, nitrogen is released in the form of N 2 and NH 3 molecules. However, the main form of the presence of nitrogen, both on Earth and on the terrestrial planets, is molecular. Ammonia, entering the upper atmosphere, quickly oxidizes, releasing nitrogen. In sedimentary rocks it is buried together with organic matter and is found in increased quantities in bituminous deposits. During the regional metamorphism of these rocks, nitrogen in various forms released into the Earth's atmosphere.
Geochemical nitrogen cycle (
Oxygen(21%) is used by living organisms for respiration and is part of organic matter (proteins, fats, carbohydrates). Ozone O 3. delays life-destructive ultraviolet radiation from the Sun.
Oxygen is the second most widespread gas in the atmosphere, playing an extremely important role in many processes in the biosphere. The dominant form of its existence is O 2. In the upper layers of the atmosphere, under the influence of ultraviolet radiation, dissociation of oxygen molecules occurs, and at an altitude of approximately 200 km, the ratio of atomic oxygen to molecular (O: O 2) becomes equal to 10. When these forms of oxygen interact in the atmosphere (at an altitude of 20-30 km), a ozone belt (ozone screen). Ozone (O 3) is necessary for living organisms, blocking most of the ultraviolet radiation from the Sun, which is harmful to them.
In the early stages of the Earth's development, free oxygen appeared in very small quantities as a result of photodissociation of carbon dioxide and water molecules in the upper layers of the atmosphere. However, these small amounts were quickly consumed by the oxidation of other gases. With the appearance of autotrophic photosynthetic organisms in the ocean, the situation changed significantly. The amount of free oxygen in the atmosphere began to increase progressively, actively oxidizing many components of the biosphere. Thus, the first portions of free oxygen contributed primarily to the transition of ferrous forms of iron into oxide forms, and sulfides into sulfates.
Eventually, the amount of free oxygen in the Earth's atmosphere reached a certain mass and was balanced in such a way that the amount produced became equal to the amount absorbed. A relative constant content of free oxygen has been established in the atmosphere.
Geochemical oxygen cycle (V.A. Vronsky, G.V. Voitkevich)
Carbon dioxide, goes into the formation of living matter, and together with water vapor creates the so-called “greenhouse (greenhouse) effect.”
Carbon (carbon dioxide) - most of it in the atmosphere is in the form of CO 2 and much less in the form of CH 4. The significance of the geochemical history of carbon in the biosphere is extremely great, since it is part of all living organisms. Within living organisms, reduced forms of carbon predominate, and in environment biospheres are oxidized. Thus, a chemical exchange is established life cycle: CO 2 ↔ living matter.
The source of primary carbon dioxide in the biosphere is volcanic activity associated with secular degassing of the mantle and lower horizons of the earth's crust. Part of this carbon dioxide arises during the thermal decomposition of ancient limestones in various metamorphic zones. Migration of CO 2 in the biosphere occurs in two ways.
The first method is expressed in the absorption of CO 2 during photosynthesis with the formation of organic substances and subsequent burial in favorable reducing conditions in the lithosphere in the form of peat, coal, oil, and oil shale. According to the second method, carbon migration leads to the creation of a carbonate system in the hydrosphere, where CO 2 turns into H 2 CO 3, HCO 3 -1, CO 3 -2. Then, with the participation of calcium (less commonly magnesium and iron), carbonates are deposited via biogenic and abiogenic pathways. Thick layers of limestone and dolomite appear. According to A.B. Ronov, the ratio of organic carbon (Corg) to carbonate carbon (Ccarb) in the history of the biosphere was 1:4.
Along with the global carbon cycle, there are also a number of small carbon cycles. So, on land, green plants absorb CO 2 for the process of photosynthesis in daytime, and at night they release it into the atmosphere. With the death of living organisms on the earth's surface, oxidation of organic substances occurs (with the participation of microorganisms) with the release of CO 2 into the atmosphere. IN last decades A special place in the carbon cycle is occupied by the massive combustion of fossil fuels and the increase in its content in the modern atmosphere.
Carbon cycle in geographical envelope(after F. Ramad, 1981)
Argon- the third most widespread atmospheric gas, which sharply distinguishes it from the extremely sparsely distributed other inert gases. However, argon in its geological history shares the fate of these gases, which are characterized by two features:
- the irreversibility of their accumulation in the atmosphere;
- close connection with the radioactive decay of certain unstable isotopes.
Inert gases are outside the cycle of most cyclic elements in the Earth's biosphere.
All inert gases can be divided into primary and radiogenic. The primary ones include those that were captured by the Earth during the period of its formation. They are extremely rare. The primary part of argon is represented mainly by the isotopes 36 Ar and 38 Ar, while atmospheric argon consists entirely of the isotope 40 Ar (99.6%), which is undoubtedly radiogenic. In potassium-containing rocks, the accumulation of radiogenic argon occurred and continues to occur due to the decay of potassium-40 through electron capture: 40 K + e → 40 Ar.
Therefore, the argon content in rocks is determined by their age and the amount of potassium. To this extent, the helium concentration in rocks is a function of their age and thorium and uranium content. Argon and helium are released into the atmosphere from the bowels of the earth during volcanic eruptions, through cracks in earth's crust in the form of gas jets, as well as during the weathering of rocks. According to calculations performed by P. Dimon and J. Culp, helium and argon in modern era accumulate in the earth's crust and enter the atmosphere in relatively small quantities. The rate of entry of these radiogenic gases is so low that during the geological history of the Earth it could not ensure their observed content in the modern atmosphere. Therefore, it remains to be assumed that most of the argon in the atmosphere came from the interior of the Earth at the earliest stages of its development, and much less was added subsequently during the process of volcanism and during the weathering of potassium-containing rocks.
Thus, over geological time, helium and argon have had different migration processes. There is very little helium in the atmosphere (about 5 * 10 -4%), and the “helium breathing” of the Earth was lighter, since it, as the lightest gas, evaporated into outer space. And “argon breathing” was heavy and argon remained within our planet. Most of the primordial noble gases, such as neon and xenon, were associated with primordial neon captured by the Earth during its formation, as well as with release during degassing of the mantle into the atmosphere. The entire body of data on the geochemistry of noble gases indicates that the primary atmosphere of the Earth arose at the earliest stages of its development.
The atmosphere contains water vapor And water in liquid and solid state. Water in the atmosphere is an important heat accumulator.
The lower layers of the atmosphere contain a large amount of mineral and technogenic dust and aerosols, combustion products, salts, spores and pollen, etc.
Up to an altitude of 100-120 km, due to complete mixing of the air, the composition of the atmosphere is homogeneous. The ratio between nitrogen and oxygen is constant. Above, inert gases, hydrogen, etc. predominate. In the lower layers of the atmosphere there is water vapor. With distance from the earth its content decreases. Higher the ratio of gases changes, for example, at an altitude of 200-800 km, oxygen predominates over nitrogen by 10-100 times.
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 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 over the poles and swells over the equator. However, this effect is expressed much more strongly in the atmosphere than in the solid shell of the Earth. In the direction from the Earth's surface to 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. At temperate latitudes, more than 75% of the mass of the atmosphere is in the troposphere. In the tropics, about 90% of the mass of the atmosphere is located within the troposphere.
In 1899, a minimum was discovered 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 earth's surface. Its peculiarity is, in particular, a sharp increase in air temperature. This increase in temperature is attributed to the formation of ozone, 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 that has electrical nature, thanks to which many types of radio communications become 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”