Why does the earth have an atmosphere? Atmosphere
Gaseous. Consists of a mixture (air) and impurities. The air at the underlying surface contains 78% nitrogen, about 21% oxygen and less than 1% other gases.
The atmosphere has a layered structure. In accordance with the change in temperature with height, 4 layers are distinguished: the troposphere (up to 16 km), the stratosphere (up to 50 km), the mesosphere (up to 80 km), the thermosphere, which gradually turns into outer space. Its role in the life of the Earth is great. It contains the oxygen necessary for breathing for all living things, protects the Earth from deadly cosmic rays, from falling and other cosmic bodies. Thanks to the atmosphere, the Earth's surface does not heat up so much during the day and does not cool down so quickly at night.
Air temperature distribution at earth's surface shown using isotherms - lines connecting points with the same temperature. Its complex distribution can be judged from maps of average January, July and annual isotherms. do not coincide with parallels, since the distribution of temperatures is influenced not only by position, but also by the underlying surface, and.
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” (as well as blue and violet) component of 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 closely related in a certain sense, and we will certainly talk about it 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 motion of molecules stops. Absolute zero on the Kelvin scale corresponds to -273º on the Celsius scale.
Accordingly the temperature T on top 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.
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 of the aircraft (up to 450 km/h), there is no change in pressure when the air flow flows around it, but at 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 :-). Mostly everything was filmed through the windshield. Pay attention to the color of the sky...
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 all 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. 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, air ionization occurs (“ auroras") - 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, a noticeable decrease in the size of this layer occurs.
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)
Atmospheric layers up to an altitude of 120 km
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 density of gases 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.
- 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 dispersion 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 glow of the atmosphere 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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Today, in our article, we will talk about one of the most important layers of our celestial body, the Earth’s atmosphere, and will give answers to many popular questions about this gaseous shell.
What is atmosphere
The atmosphere is one of the layers of our planet, which is nothing more than a gaseous shell. Our atmosphere is held in place due to the earth's attraction, due to the forces of gravity. Basically, our atmosphere consists of oxygen as well as carbon dioxide.
Why is the atmosphere called the Earth's armor?
Often the gas layer of the shell of our planet is conventionally called our invisible armor. And the answer to the question about the origin of this name is quite simple, because it is the Earth’s atmosphere that is our protection from meteorites and other cosmic bodies that can fall to the surface. In addition, the atmosphere also protects us from radiation rays emitted by the Sun. They are not able to pass through the gas layer and harm humanity.
Meteorites, as is known, are capable of falling towards the Earth, but many of them simply catch fire and do not reach the surface. And if we talk about why a meteorite, flying through the Earth’s atmosphere, becomes hot, then the answer here is also extremely simple. Entering the atmosphere, due to the very decent speed of fall, and due to the friction created between the atmosphere and the cosmic body itself, it heats up and simply lights up.
Why does the atmosphere exist: how did it appear?
There is also a question, which is why the atmosphere exists at all, why it rotates with our planet and does not escape into space. And here, too, there are no secrets from the modern minds of humanity; people have already received the answer to this question a long time ago.
First we need to answer why the atmosphere rotates with the Earth. The fact is that here the force of universal gravity comes into play again, gravity, which holds our atmosphere in the position in which it is located. However, what was said above is quite suitable as an answer to the question of why the Earth’s atmosphere does not escape into space.
Why is there no hydrogen in the atmosphere?
It is a common fact that there is almost no hydrogen in our atmosphere. The reason for this phenomenon is that its molecules are very light; accordingly, it quickly evaporates into space, and its share in the Earth’s atmospheric layer is minimal.