Everyone who has flown on an airplane is used to this kind of message: “our flight is at an altitude of 10,000 m, the temperature overboard is 50 ° C.” It seems nothing special. The farther from the surface of the Earth heated by the Sun, the colder. Many people think that the decrease in temperature with height goes on continuously and gradually the temperature 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 over the poles and swells over the equator. However, this effect is much stronger 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 drops. 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 within the troposphere masses of the atmosphere.
In 1899, a minimum was found in the vertical temperature profile at a certain height, and then the temperature slightly increased. 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 former idea of the uniqueness of the layer lying above the troposphere. The stratosphere extends to a height of about 50 km above the earth's surface. Its feature is, in particular, a sharp increase in air temperature. This increase in temperature is explained ozone formation reaction - one of the main chemical reactions occurring in the atmosphere.
The bulk of the ozone is concentrated at altitudes of about 25 km, but in general the ozone layer is a shell strongly stretched along the height, covering almost the entire stratosphere. The interaction of oxygen with ultraviolet rays is one of the favorable processes in the earth's atmosphere that contribute 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 such a level of energy is created that is suitable for the existence of terrestrial life forms. 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 rises with height 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", here 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 fall indefinitely, then the temperature rises again.
Thermosphere is the first layer ionosphere. Unlike the previously mentioned layers, the ionosphere is not distinguished by temperature. The ionosphere is a region of an electrical nature that makes many types of radio communications possible. The ionosphere is divided into several layers, designating them with the letters D, E, F1 and F2. These layers also have special names. The division 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 thus prevents their further propagation. The best studied layer E is located at an altitude of about 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 farther distances than would be expected if they propagated only in a straight line, without being reflected from the E layer. The F layer also 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 indicates the existence of the outskirts of space near the Earth. It is difficult to determine exactly where the atmosphere ends and space begins, since the density of atmospheric gases gradually decreases with height and the atmosphere itself gradually turns into an almost vacuum, in which only individual molecules meet. Already at an altitude of about 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 the processes in the atmosphere can be found on the website "Earth climate"
The atmosphere is the gaseous shell of our planet that rotates with the Earth. The gas in the atmosphere is called air. The atmosphere is in contact with the hydrosphere and partially covers the lithosphere. But it is difficult to determine the upper bounds. Conventionally, it is assumed that the atmosphere extends upwards for about three thousand kilometers. There it flows smoothly into the airless space.
The chemical composition of the Earth's atmosphere
The formation of the chemical composition of the atmosphere began about four billion years ago. Initially, the atmosphere consisted only of light gases - helium and hydrogen. According to scientists, the initial prerequisites for the creation of a gas shell around the Earth were volcanic eruptions, which, together with lava, emitted a huge amount of gases. Subsequently, gas exchange began with water spaces, with living organisms, with the products of their activity. The composition of the air gradually changed and in its present form was fixed several million years ago.
The main components of the atmosphere are nitrogen (about 79%) and oxygen (20%). The remaining percentage (1%) is accounted for by the following gases: argon, neon, helium, methane, carbon dioxide, hydrogen, krypton, xenon, ozone, ammonia, sulfur dioxide and nitrogen, nitrous oxide and carbon monoxide included in this one percent.
In addition, the air contains water vapor and particulate matter (plant pollen, dust, salt crystals, aerosol impurities).
Recently, scientists have noted not a qualitative, but a quantitative change in some air ingredients. And the reason for this is the person and his activity. Only in the last 100 years, the content of carbon dioxide has increased significantly! This is fraught with many problems, the most global of which is climate change.
Formation of weather and climate
The atmosphere plays a vital role in shaping the climate and weather on Earth. A lot depends on the amount of sunlight, on the nature of the underlying surface and atmospheric circulation.
Let's look at the factors in order.
1. The atmosphere transmits the heat of the sun's rays and absorbs harmful radiation. The ancient Greeks knew that the rays of the Sun fall on different parts of the Earth at different angles. The very word "climate" in translation from ancient Greek means "slope". So, at the equator, the sun's rays fall almost vertically, because it is very hot here. The closer to the poles, the greater the angle of inclination. And the temperature is dropping.
2. Due to the uneven heating of the Earth, air currents are formed in the atmosphere. They are classified according to their size. The smallest (tens and hundreds of meters) are local winds. This is followed by monsoons and trade winds, cyclones and anticyclones, planetary frontal zones.
All these air masses are constantly moving. Some of them are quite static. For example, the trade winds that blow from the subtropics towards the equator. The movement of others is largely dependent on atmospheric pressure.
3. Atmospheric pressure is another factor influencing climate formation. This is the air pressure on the earth's surface. As you know, air masses move from an area with high atmospheric pressure towards an area where this pressure is lower.
There are 7 zones in total. The equator is a low pressure zone. Further, on both sides of the equator up to the thirtieth latitudes - an area of high pressure. From 30° to 60° - again low pressure. And from 60° to the poles - a zone of high pressure. Air masses circulate between these zones. Those that go from the sea to land bring rain and bad weather, and those that blow from the continents bring clear and dry weather. In places where air currents collide, atmospheric front zones are formed, which are characterized by precipitation and inclement, windy weather.
Scientists have proven that even a person's well-being depends on atmospheric pressure. According to international standards, normal atmospheric pressure is 760 mm Hg. column at 0°C. This figure is calculated for those areas of land that are almost flush with sea level. The pressure decreases with altitude. Therefore, for example, for St. Petersburg 760 mm Hg. - is the norm. But for Moscow, which is located higher, the normal pressure is 748 mm Hg.
The pressure changes not only vertically, but also horizontally. This is especially felt during the passage of cyclones.
The structure of the atmosphere
The atmosphere is like a layer cake. And each layer has its own characteristics.
. Troposphere is the layer closest to the Earth. The "thickness" of this layer changes as you move away from the equator. Above the equator, the layer extends upwards for 16-18 km, in temperate zones - for 10-12 km, at the poles - for 8-10 km.
It is here that 80% of the total mass of air and 90% of water vapor are contained. Clouds form here, cyclones and anticyclones arise. The air temperature depends on the altitude of the area. On average, it drops by 0.65°C for every 100 meters.
. tropopause- transitional layer of the atmosphere. Its height is from several hundred meters to 1-2 km. The air temperature in summer is higher than in winter. So, for example, over the poles in winter -65 ° C. And over the equator at any time of the year it is -70 ° C.
. Stratosphere- this is a layer, the upper boundary of which runs at an altitude of 50-55 kilometers. Turbulence is low here, water vapor content in the air is negligible. But a lot of ozone. Its maximum concentration is at an altitude of 20-25 km. In the stratosphere, the air temperature begins to rise and reaches +0.8 ° C. This is due to the fact that the ozone layer interacts with ultraviolet radiation.
. Stratopause- a low intermediate layer between the stratosphere and the mesosphere following it.
. Mesosphere- the upper boundary of this layer is 80-85 kilometers. Here complex photochemical processes involving free radicals take place. It is they who provide that gentle blue glow of our planet, which is seen from space.
Most comets and meteorites burn up in the mesosphere.
. mesopause- the next intermediate layer, the air temperature in which is at least -90 °.
. Thermosphere- the lower boundary begins at an altitude of 80 - 90 km, and the upper boundary of the layer passes approximately at the mark of 800 km. The air temperature is rising. It can vary from +500° C to +1000° C. During the day, temperature fluctuations amount to hundreds of degrees! But the air here is so rarefied that the understanding of the term "temperature" as we imagine it is not appropriate here.
. Ionosphere- unites mesosphere, mesopause and thermosphere. The air here consists mainly of oxygen and nitrogen molecules, as well as quasi-neutral plasma. The sun's rays, falling into the ionosphere, strongly ionize air molecules. In the lower layer (up to 90 km), the degree of ionization is low. The higher, the more ionization. So, at an altitude of 100-110 km, electrons are concentrated. This contributes to the reflection of short and medium radio waves.
The most important layer of the ionosphere is the upper one, which is located at an altitude of 150-400 km. Its peculiarity is that it reflects radio waves, and this contributes to the transmission of radio signals over long distances.
It is in the ionosphere that such a phenomenon as aurora occurs.
. Exosphere- consists of oxygen, helium and hydrogen atoms. The gas in this layer is very rarefied, and often hydrogen atoms escape into outer space. Therefore, this layer is called the "scattering zone".
The first scientist who suggested that our atmosphere has weight was the Italian E. Torricelli. Ostap Bender, for example, in the novel "The Golden Calf" lamented that each person was pressed by an air column weighing 14 kg! But the great strategist was a little mistaken. An adult person experiences pressure of 13-15 tons! But we do not feel this heaviness, because atmospheric pressure is balanced by the internal pressure of a person. The weight of our atmosphere is 5,300,000,000,000,000 tons. The figure is colossal, although it is only a millionth of the weight of our planet.
The stratosphere is one of the upper layers of the air shell of our planet. It starts at an altitude of about 11 km above the ground. Passenger aircraft no longer fly here and clouds rarely form. Ozone is located in the stratosphere - a thin shell that protects the planet from the penetration of harmful ultraviolet radiation.
Air shell of the planet
The atmosphere is the gaseous shell of the Earth, adjacent to the inner surface of the hydrosphere and the earth's crust. Its outer boundary gradually passes into outer space. The composition of the atmosphere includes gases: nitrogen, oxygen, argon, carbon dioxide, and so on, as well as impurities in the form of dust, water drops, ice crystals, combustion products. The ratio of the main elements of the air shell is kept constant. The exceptions are carbon dioxide and water - their amount in the atmosphere often changes.
Layers of the gaseous envelope
The atmosphere is divided into several layers, located one above the other and having features in the composition:
boundary layer - directly adjacent to the surface of the planet, extending to a height of 1-2 km;
troposphere - the second layer, the outer boundary is located on average at an altitude of 11 km, almost all the water vapor of the atmosphere is concentrated here, clouds form, cyclones and anticyclones arise, as the height increases, the temperature rises;
tropopause - transitional layer, characterized by the cessation of temperature decrease;
the stratosphere is a layer that extends up to a height of 50 km and is divided into three zones: from 11 to 25 km the temperature changes slightly, from 25 to 40 - the temperature rises, from 40 to 50 - the temperature remains constant (stratopause);
the mesosphere extends to a height of up to 80-90 km;
the thermosphere reaches 700-800 km above sea level, here at an altitude of 100 km there is the Karman line, which is taken as the boundary between the Earth's atmosphere and space;
The exosphere is also called the scatter zone, here it loses particles of matter a lot, and they fly away into space.
Temperature changes in the stratosphere
So, the stratosphere is the part of the gaseous shell of the planet that follows the troposphere. Here, the air temperature, which is constant throughout the tropopause, begins to change. The height of the stratosphere is approximately 40 km. The lower limit is 11 km above sea level. Starting from this mark, the temperature undergoes slight changes. At an altitude of 25 km, the heating index begins to slowly increase. By the mark of 40 km above sea level, the temperature rises from -56.5º to +0.8ºС. Further, it remains close to zero degrees up to an altitude of 50-55 km. The zone between 40 and 55 kilometers is called the stratopause, since the temperature here does not change. It is a transition zone from the stratosphere to the mesosphere.
Features of the stratosphere
The Earth's stratosphere contains about 20% of the mass of the entire atmosphere. The air here is so rarefied that it is impossible for a person to stay without a special spacesuit. This fact is one of the reasons why flights into the stratosphere began to be carried out only relatively recently.
Another feature of the planet's gas envelope at an altitude of 11-50 km is a very small amount of water vapor. For this reason, clouds almost never form in the stratosphere. For them, there is simply no building material. However, it is rarely possible to observe the so-called mother-of-pearl clouds, which “decorate” the stratosphere (the photo is presented below) at an altitude of 20-30 km above sea level. Thin, as if luminous formations from the inside can be observed after sunset or before sunrise. The shape of mother-of-pearl clouds is similar to cirrus or cirrocumulus.
Earth's ozone layer
The main distinguishing feature of the stratosphere is the maximum concentration of ozone in the entire atmosphere. It is formed under the influence of sunlight and protects all life on the planet from their destructive radiation. The ozone layer of the Earth is located at an altitude of 20-25 km above sea level. O 3 molecules are distributed throughout the stratosphere and even exist near the surface of the planet, but their highest concentration is observed at this level.
It should be noted that the ozone layer of the Earth is only 3-4 mm. This will be its thickness if particles of this gas are placed under conditions of normal pressure, for example, near the surface of the planet. Ozone is formed as a result of the breakdown of an oxygen molecule under the action of ultraviolet radiation into two atoms. One of them combines with a "full-fledged" molecule and ozone is formed - O 3.
Dangerous Defender
Thus, today the stratosphere is a more explored layer of the atmosphere than at the beginning of the last century. However, the future of the ozone layer, without which life on Earth would not have arisen, is still not very clear. While countries are reducing the production of freon, some scientists say that this will not bring much benefit, at least at such a pace, while others say that this is not necessary at all, since most of the harmful substances are formed naturally. Who is right, time will tell.
Together with the Earth, the gaseous shell of our planet, called the atmosphere, also rotates. The processes that take place in it determine the weather on our planet, it is also the atmosphere that protects the animal and plant world from the harmful effects of ultraviolet rays, ensures optimal temperature, and so on. , is not so easy to determine, and here's why.
Atmosphere of the earth km
The atmosphere is a gaseous space. Its upper limit is not clearly expressed, since the gases, the higher, the more rarefied and gradually pass into outer space. If we talk about the approximate diameter of the earth's atmosphere, then scientists call the figure about 2-3 thousand kilometers.
The Earth's atmosphere is of four layers, which also smoothly transition from one to another. This:
- troposphere;
- stratosphere;
- mesosphere;
- ionosphere (thermosphere).
By the way, an interesting fact: the planet earth without an atmosphere would be as quiet as the moon, since sound is vibrations of air particles. And the fact that the sky is blue light is explained by the specifics of the decomposition of the sun's rays passing through the atmosphere.
Features of each layer of the atmosphere
The thickness of the troposphere is from eight to ten kilometers (in temperate latitudes - up to 12, and above the equator - up to 18 kilometers). The air in this layer is heated by land and water, so the more radius of the earth's atmosphere, the lower the temperature. 80 percent of the entire mass of the atmosphere is concentrated here and water vapor is concentrated, thunderstorms, storms, clouds, precipitation are formed, air moves in vertical and horizontal directions.
The stratosphere is located from the troposphere at an altitude of eight to 50 kilometers. The air here is rarefied, so the sun's rays do not scatter, and the color of the sky becomes purple. This layer absorbs ultraviolet radiation due to ozone.
The mesosphere is located even higher - at an altitude of 50-80 kilometers. Here already the sky seems black, and the temperature of the layer is up to minus ninety degrees. Next comes the thermosphere, here the temperature already rises sharply and then stops at an altitude of 600 km at around 240 degrees.
The most rarefied layer is the ionosphere, it is characterized by high electrification, and it also reflects radio waves of different lengths, like a mirror. This is where the northern lights are formed.
Updated: March 31, 2016 by: Anna Volosovets
ATMOSPHERE OF THE EARTH(Greek atmos steam + sphaira ball) - gaseous shell surrounding the Earth. The mass of the atmosphere is about 5.15·10 15 The biological significance of the atmosphere is enormous. In the atmosphere, there is a mass-energy exchange between animate and inanimate nature, between flora and fauna. Atmospheric nitrogen is assimilated by microorganisms; plants synthesize organic substances from carbon dioxide and water due to the energy of the sun and release oxygen. The presence of the atmosphere ensures the preservation of water on Earth, which is also an important condition for the existence of living organisms.
Studies carried out with the help of high-altitude geophysical rockets, artificial earth satellites and interplanetary automatic stations have established that the earth's atmosphere extends for thousands of kilometers. The boundaries of the atmosphere are unstable, they are influenced by the gravitational field of the moon and the pressure of the flow of sunlight. Above the equator in the region of the earth's shadow, the atmosphere reaches heights of about 10,000 km, and above the poles, its boundaries are 3,000 km from the earth's surface. The main mass of the atmosphere (80-90%) is within altitudes up to 12-16 km, which is explained by the exponential (non-linear) nature of the decrease in the density (rarefaction) of its gaseous medium as the height above sea level increases.
The existence of most living organisms in natural conditions is possible in even narrower boundaries of the atmosphere, up to 7-8 km, where a combination of such atmospheric factors as gas composition, temperature, pressure, and humidity, necessary for the active course of biological processes, takes place. The movement and ionization of air, atmospheric precipitation, and the electrical state of the atmosphere are also of hygienic importance.
Gas composition
The atmosphere is a physical mixture of gases (Table 1), mainly nitrogen and oxygen (78.08 and 20.95 vol. %). The ratio of atmospheric gases is almost the same up to altitudes of 80-100 km. The constancy of the main part of the gas composition of the atmosphere is due to the relative balancing of the processes of gas exchange between animate and inanimate nature and the continuous mixing of air masses in the horizontal and vertical directions.
Table 1. CHARACTERISTICS OF THE CHEMICAL COMPOSITION OF DRY ATMOSPHERIC AIR NEAR THE EARTH'S SURFACE
|
Gas composition |
Volume concentration, % |
|
Oxygen |
|
|
Carbon dioxide |
|
|
Nitrous oxide |
|
|
Sulfur dioxide |
0 to 0.0001 |
|
0 to 0.000007 in summer, 0 to 0.000002 in winter |
|
|
nitrogen dioxide |
0 to 0.000002 |
|
Carbon monoxide |
|
At altitudes above 100 km, the percentage of individual gases changes due to their diffuse stratification under the influence of gravity and temperature. In addition, under the action of the short-wavelength part of ultraviolet and X-rays at an altitude of 100 km or more, oxygen, nitrogen and carbon dioxide molecules dissociate into atoms. At high altitudes, these gases are in the form of highly ionized atoms.
The content of carbon dioxide in the atmosphere of different regions of the Earth is less constant, which is partly due to the uneven distribution of large industrial enterprises that pollute the air, as well as the uneven distribution of vegetation and water basins that absorb carbon dioxide on the Earth. Also variable in the atmosphere is the content of aerosols (see) - particles suspended in the air ranging in size from several millimicrons to several tens of microns - formed as a result of volcanic eruptions, powerful artificial explosions, pollution by industrial enterprises. The concentration of aerosols decreases rapidly with altitude.
The most unstable and important of the variable components of the atmosphere is water vapor, the concentration of which at the earth's surface can vary from 3% (in the tropics) to 2 × 10 -10% (in Antarctica). The higher the air temperature, the more moisture, ceteris paribus, can be in the atmosphere and vice versa. The bulk of water vapor is concentrated in the atmosphere up to altitudes of 8-10 km. The content of water vapor in the atmosphere depends on the combined influence of the processes of evaporation, condensation and horizontal transport. At high altitudes, due to a decrease in temperature and condensation of vapors, the air is practically dry.
The Earth's atmosphere, in addition to molecular and atomic oxygen, contains a small amount of ozone (see), the concentration of which is very variable and varies depending on the height and season. Most of the ozone is contained in the region of the poles by the end of the polar night at an altitude of 15-30 km with a sharp decrease up and down. Ozone arises as a result of the photochemical action of ultraviolet solar radiation on oxygen, mainly at altitudes of 20-50 km. In this case, diatomic oxygen molecules partially decompose into atoms and, joining undecomposed molecules, form triatomic ozone molecules (polymeric, allotropic form of oxygen).
The presence in the atmosphere of a group of so-called inert gases (helium, neon, argon, krypton, xenon) is associated with the continuous flow of natural radioactive decay processes.
The biological significance of gases the atmosphere is very large. For most multicellular organisms, a certain content of molecular oxygen in a gaseous or aqueous medium is an indispensable factor in their existence, which during respiration determines the release of energy from organic substances created initially during photosynthesis. It is no coincidence that the upper boundaries of the biosphere (the part of the surface of the globe and the lower part of the atmosphere where life exists) are determined by the presence of a sufficient amount of oxygen. In the process of evolution, organisms have adapted to a certain level of oxygen in the atmosphere; changing the oxygen content in the direction of decreasing or increasing has an adverse effect (see Altitude sickness, Hyperoxia, Hypoxia).
The ozone-allotropic form of oxygen also has a pronounced biological effect. At concentrations not exceeding 0.0001 mg / l, which is typical for resort areas and sea coasts, ozone has a healing effect - it stimulates breathing and cardiovascular activity, improves sleep. With an increase in the concentration of ozone, its toxic effect manifests itself: eye irritation, necrotic inflammation of the mucous membranes of the respiratory tract, exacerbation of pulmonary diseases, autonomic neuroses. Entering into combination with hemoglobin, ozone forms methemoglobin, which leads to a violation of the respiratory function of the blood; the transfer of oxygen from the lungs to the tissues becomes difficult, the phenomena of suffocation develop. Atomic oxygen has a similar adverse effect on the body. Ozone plays a significant role in creating the thermal regimes of various layers of the atmosphere due to the extremely strong absorption of solar radiation and terrestrial radiation. Ozone absorbs ultraviolet and infrared rays most intensively. Solar rays with a wavelength of less than 300 nm are almost completely absorbed by atmospheric ozone. Thus, the Earth is surrounded by a kind of "ozone screen" that protects many organisms from the harmful effects of ultraviolet radiation from the sun. Nitrogen in atmospheric air is of great biological importance, primarily as a source of so-called. fixed nitrogen - a resource of plant (and ultimately animal) food. The physiological significance of nitrogen is determined by its participation in creating the level of atmospheric pressure necessary for life processes. Under certain conditions of pressure changes, nitrogen plays a major role in the development of a number of disorders in the body (see Decompression sickness). Assumptions that nitrogen weakens the toxic effect of oxygen on the body and is absorbed from the atmosphere not only by microorganisms, but also by higher animals, are controversial.
The inert gases of the atmosphere (xenon, krypton, argon, neon, helium) at the partial pressure they create under normal conditions can be classified as biologically indifferent gases. With a significant increase in partial pressure, these gases have a narcotic effect.
The presence of carbon dioxide in the atmosphere ensures the accumulation of solar energy in the biosphere due to the photosynthesis of complex carbon compounds, which continuously arise, change and decompose in the course of life. This dynamic system is maintained as a result of the activity of algae and land plants that capture the energy of sunlight and use it to convert carbon dioxide (see) and water into a variety of organic compounds with the release of oxygen. The upward extension of the biosphere is partially limited by the fact that at altitudes of more than 6-7 km, chlorophyll-containing plants cannot live due to the low partial pressure of carbon dioxide. Carbon dioxide is also very active in physiological terms, as it plays an important role in the regulation of metabolic processes, the activity of the central nervous system, respiration, blood circulation, and the oxygen regime of the body. However, this regulation is mediated by the influence of carbon dioxide produced by the body itself, and not from the atmosphere. In the tissues and blood of animals and humans, the partial pressure of carbon dioxide is approximately 200 times higher than its pressure in the atmosphere. And only with a significant increase in the content of carbon dioxide in the atmosphere (more than 0.6-1%), there are violations in the body, denoted by the term hypercapnia (see). The complete elimination of carbon dioxide from the inhaled air cannot directly have an adverse effect on the human and animal organisms.
Carbon dioxide plays a role in absorbing long-wavelength radiation and maintaining the "greenhouse effect" that raises the temperature near the Earth's surface. The problem of the effect on thermal and other regimes of the atmosphere of carbon dioxide, which enters the air in huge quantities as a waste product of industry, is also being studied.
Atmospheric water vapor (air humidity) also affects the human body, in particular, heat exchange with the environment.
As a result of the condensation of water vapor in the atmosphere, clouds form and precipitation (rain, hail, snow) falls. Water vapor, scattering solar radiation, participate in the creation of the thermal regime of the Earth and the lower layers of the atmosphere, in the formation of meteorological conditions.
Atmosphere pressure
Atmospheric pressure (barometric) is the pressure exerted by the atmosphere under the influence of gravity on the surface of the Earth. The value of this pressure at each point in the atmosphere is equal to the weight of the overlying column of air with a unit base, extending above the place of measurement to the boundaries of the atmosphere. Atmospheric pressure is measured with a barometer (see) and expressed in millibars, in newtons per square meter or the height of the mercury column in the barometer in millimeters, reduced to 0 ° and the normal value of the acceleration of gravity. In table. 2 shows the most commonly used units of atmospheric pressure.
The change in pressure occurs due to uneven heating of air masses located above land and water at different geographical latitudes. As the temperature rises, the density of air and the pressure it creates decrease. A huge accumulation of fast-moving air with reduced pressure (with a decrease in pressure from the periphery to the center of the vortex) is called a cyclone, with increased pressure (with an increase in pressure towards the center of the vortex) - an anticyclone. For weather forecasting, non-periodic changes in atmospheric pressure are important, which occur in moving vast masses and are associated with the emergence, development and destruction of anticyclones and cyclones. Especially large changes in atmospheric pressure are associated with the rapid movement of tropical cyclones. At the same time, atmospheric pressure can vary by 30-40 mbar per day.
The drop in atmospheric pressure in millibars over a distance of 100 km is called the horizontal barometric gradient. Typically, the horizontal barometric gradient is 1–3 mbar, but in tropical cyclones it sometimes increases to tens of millibars per 100 km.
As the altitude rises, atmospheric pressure decreases in a logarithmic relationship: at first very sharply, and then less and less noticeably (Fig. 1). Therefore, the barometric pressure curve is exponential.
The decrease in pressure per unit vertical distance is called the vertical barometric gradient. Often they use the reciprocal of it - the barometric step.
Since the barometric pressure is the sum of the partial pressures of the gases that form the air, it is obvious that with the rise to a height, along with a decrease in the total pressure of the atmosphere, the partial pressure of the gases that make up the air also decreases. The value of the partial pressure of any gas in the atmosphere is calculated by the formula
where P x is the partial pressure of the gas, P z is the atmospheric pressure at altitude Z, X% is the percentage of gas whose partial pressure is to be determined.
Rice. 1. Change in barometric pressure depending on the height above sea level.
Rice. 2. Change in the partial pressure of oxygen in the alveolar air and saturation of arterial blood with oxygen depending on the change in altitude when breathing air and oxygen. Oxygen breathing starts from a height of 8.5 km (experiment in a pressure chamber).
Rice. 3. Comparative curves of the average values of active consciousness in a person in minutes at different heights after a quick rise while breathing air (I) and oxygen (II). At altitudes above 15 km, active consciousness is equally disturbed when breathing oxygen and air. At altitudes up to 15 km, oxygen breathing significantly prolongs the period of active consciousness (experiment in a pressure chamber).
Since the percentage composition of atmospheric gases is relatively constant, to determine the partial pressure of any gas, it is only necessary to know the total barometric pressure at a given altitude (Fig. 1 and Table 3).
Table 3. TABLE OF STANDARD ATMOSPHERE (GOST 4401-64) 1
|
Geometric height (m) |
Temperature |
barometric pressure |
Partial pressure of oxygen (mmHg) |
|||
|
mmHg Art. |
||||||
1 Given in abbreviated form and supplemented by the column "Partial pressure of oxygen".
When determining the partial pressure of a gas in moist air, the pressure (elasticity) of saturated vapors must be subtracted from the barometric pressure.
The formula for determining the partial pressure of a gas in moist air will be slightly different than for dry air:
where pH 2 O is the elasticity of water vapor. At t° 37°, the elasticity of saturated water vapor is 47 mm Hg. Art. This value is used in calculating the partial pressures of gases in alveolar air in ground and high-altitude conditions.
Effects of high and low blood pressure on the body. Changes in barometric pressure upwards or downwards have a variety of effects on the organism of animals and humans. The effect of increased pressure is associated with the mechanical and penetrating physical and chemical action of the gaseous medium (the so-called compression and penetrating effects).
The compression effect is manifested by: general volumetric compression, due to a uniform increase in the forces of mechanical pressure on organs and tissues; mechanonarcosis due to uniform volumetric compression at very high barometric pressure; local uneven pressure on tissues that limit gas-containing cavities when there is a broken connection between the outside air and the air in the cavity, for example, the middle ear, the accessory cavities of the nose (see Barotrauma); an increase in gas density in the external respiration system, which causes an increase in resistance to respiratory movements, especially during forced breathing (exercise, hypercapnia).
The penetrating effect can lead to the toxic effect of oxygen and indifferent gases, an increase in the content of which in the blood and tissues causes a narcotic reaction, the first signs of a cut when using a nitrogen-oxygen mixture in humans occur at a pressure of 4-8 atm. An increase in the partial pressure of oxygen initially reduces the level of functioning of the cardiovascular and respiratory systems due to the shutdown of the regulatory effect of physiological hypoxemia. With an increase in the partial pressure of oxygen in the lungs more than 0.8-1 ata, its toxic effect is manifested (damage to the lung tissue, convulsions, collapse).
The penetrating and compressive effects of the increased pressure of the gaseous medium are used in clinical medicine in the treatment of various diseases with general and local impairment of oxygen supply (see Barotherapy, Oxygen therapy).
Lowering the pressure has an even more pronounced effect on the body. Under conditions of an extremely rarefied atmosphere, the main pathogenetic factor leading to loss of consciousness in a few seconds, and to death in 4-5 minutes, is a decrease in the partial pressure of oxygen in the inhaled air, and then in the alveolar air, blood and tissues (Fig. 2 and 3). Moderate hypoxia causes the development of adaptive reactions of the respiratory system and hemodynamics, aimed at maintaining oxygen supply primarily to vital organs (brain, heart). With a pronounced lack of oxygen, oxidative processes are inhibited (due to respiratory enzymes), and aerobic processes of energy production in mitochondria are disrupted. This leads first to a breakdown in the functions of vital organs, and then to irreversible structural damage and death of the body. The development of adaptive and pathological reactions, a change in the functional state of the body and human performance with a decrease in atmospheric pressure is determined by the degree and rate of decrease in the partial pressure of oxygen in the inhaled air, the duration of stay at a height, the intensity of the work performed, the initial state of the body (see Altitude sickness).
A decrease in pressure at altitudes (even with the exclusion of lack of oxygen) causes serious disorders in the body, united by the concept of "decompression disorders", which include: high-altitude flatulence, barotitis and barosinusitis, high-altitude decompression sickness and high-altitude tissue emphysema.
High-altitude flatulence develops due to the expansion of gases in the gastrointestinal tract with a decrease in barometric pressure on the abdominal wall when ascending to altitudes of 7-12 km or more. Of certain importance is the release of gases dissolved in the intestinal contents.
Expansion of gases leads to stretching of the stomach and intestines, raising the diaphragm, changing the position of the heart, irritating the receptor apparatus of these organs and causing pathological reflexes that disrupt breathing and blood circulation. Often there are sharp pains in the abdomen. Similar phenomena sometimes occur in divers when ascending from depth to the surface.
The mechanism of development of barotitis and barosinusitis, manifested by a feeling of congestion and pain, respectively, in the middle ear or accessory cavities of the nose, is similar to the development of high-altitude flatulence.
The decrease in pressure, in addition to expanding the gases contained in the body cavities, also causes the release of gases from liquids and tissues in which they were dissolved under pressure at sea level or at depth, and the formation of gas bubbles in the body.
This process of an exit of the dissolved gases (first of all nitrogen) causes development of a decompression sickness (see).
Rice. 4. Dependence of the boiling point of water on altitude and barometric pressure. The pressure numbers are located below the corresponding altitude numbers.
With a decrease in atmospheric pressure, the boiling point of liquids decreases (Fig. 4). At an altitude of more than 19 km, where the barometric pressure is equal to (or less than) the elasticity of saturated vapors at body temperature (37 °), “boiling” of the interstitial and intercellular fluid of the body can occur, resulting in large veins, in the cavity of the pleura, stomach, pericardium , in loose adipose tissue, that is, in areas with low hydrostatic and interstitial pressure, water vapor bubbles form, high-altitude tissue emphysema develops. Altitude "boiling" does not affect cellular structures, being localized only in the intercellular fluid and blood.
Massive steam bubbles can block the work of the heart and blood circulation and disrupt the functioning of vital systems and organs. This is a serious complication of acute oxygen starvation that develops at high altitudes. Prevention of high-altitude tissue emphysema can be achieved by creating external counterpressure on the body with high-altitude equipment.
The very process of lowering barometric pressure (decompression) under certain parameters can become a damaging factor. Depending on the speed, decompression is divided into smooth (slow) and explosive. The latter proceeds in less than 1 second and is accompanied by a strong bang (as in a shot), the formation of fog (condensation of water vapor due to cooling of expanding air). Typically, explosive decompression occurs at altitudes when the glazing of a pressurized cockpit or pressure suit breaks.
In explosive decompression, the lungs are the first to suffer. A rapid increase in intrapulmonary excess pressure (more than 80 mm Hg) leads to a significant stretching of the lung tissue, which can cause rupture of the lungs (with their expansion by 2.3 times). Explosive decompression can also cause damage to the gastrointestinal tract. The amount of excess pressure that occurs in the lungs will largely depend on the rate of air outflow from them during decompression and the volume of air in the lungs. It is especially dangerous if the upper airways at the time of decompression turn out to be closed (when swallowing, holding the breath) or decompression coincides with the phase of deep inspiration, when the lungs are filled with a large amount of air.
Atmospheric temperature
The temperature of the atmosphere initially decreases with increasing altitude (on average, from 15° near the ground to -56.5° at an altitude of 11-18 km). The vertical temperature gradient in this zone of the atmosphere is about 0.6° for every 100 m; it changes during the day and year (Table 4).
Table 4. CHANGES IN THE VERTICAL TEMPERATURE GRADIENT OVER THE MIDDLE STRIP OF THE USSR TERRITORY
Rice. 5. Change in the temperature of the atmosphere at different heights. The boundaries of the spheres are indicated by a dotted line.
At altitudes of 11 - 25 km, the temperature becomes constant and amounts to -56.5 °; then the temperature begins to rise, reaching 30–40° at an altitude of 40 km, and 70° at an altitude of 50–60 km (Fig. 5), which is associated with intense absorption of solar radiation by ozone. From a height of 60–80 km, the air temperature again decreases slightly (up to 60°C), and then progressively increases and reaches 270°C at an altitude of 120 km, 800°C at an altitude of 220 km, 1500°C at an altitude of 300 km, and
on the border with outer space - more than 3000 °. It should be noted that due to the high rarefaction and low density of gases at these heights, their heat capacity and ability to heat colder bodies is very small. Under these conditions, the transfer of heat from one body to another occurs only through radiation. All considered changes in temperature in the atmosphere are associated with the absorption of solar thermal energy by air masses - direct and reflected.
In the lower part of the atmosphere near the Earth's surface, the temperature distribution depends on the influx of solar radiation and therefore has a mainly latitudinal character, that is, lines of equal temperature - isotherms - are parallel to latitudes. Since the atmosphere in the lower layers is heated from the earth's surface, the horizontal temperature change is strongly influenced by the distribution of continents and oceans, the thermal properties of which are different. Usually, reference books indicate the temperature measured during network meteorological observations with a thermometer installed at a height of 2 m above the soil surface. The highest temperatures (up to 58°C) are observed in the deserts of Iran, and in the USSR - in the south of Turkmenistan (up to 50°), the lowest (up to -87°) in Antarctica, and in the USSR - in the regions of Verkhoyansk and Oymyakon (up to -68° ). In winter, the vertical temperature gradient in some cases, instead of 0.6 °, can exceed 1 ° per 100 m or even take a negative value. During the day in the warm season, it can be equal to many tens of degrees per 100 m. There is also a horizontal temperature gradient, which is usually referred to as a distance of 100 km along the normal to the isotherm. The magnitude of the horizontal temperature gradient is tenths of a degree per 100 km, and in frontal zones it can exceed 10° per 100 m.
The human body is able to maintain thermal homeostasis (see) within a fairly narrow range of outdoor temperature fluctuations - from 15 to 45 °. Significant differences in the temperature of the atmosphere near the Earth and at heights require the use of special protective technical means to ensure the thermal balance between the human body and the environment in high-altitude and space flights.
Characteristic changes in the parameters of the atmosphere (temperature, pressure, chemical composition, electrical state) make it possible to conditionally divide the atmosphere into zones, or layers. Troposphere- the closest layer to the Earth, the upper boundary of which extends at the equator up to 17-18 km, at the poles - up to 7-8 km, in middle latitudes - up to 12-16 km. The troposphere is characterized by an exponential pressure drop, the presence of a constant vertical temperature gradient, horizontal and vertical movements of air masses, and significant changes in air humidity. The troposphere contains the bulk of the atmosphere, as well as a significant part of the biosphere; here all the main types of clouds arise, air masses and fronts are formed, cyclones and anticyclones develop. In the troposphere, due to the reflection of the sun's rays by the snow cover of the Earth and the cooling of the surface layers of air, the so-called inversion takes place, that is, an increase in temperature in the atmosphere from the bottom up instead of the usual decrease.
In the warm season, constant turbulent (random, chaotic) mixing of air masses and heat transfer by air flows (convection) occur in the troposphere. Convection destroys fogs and reduces the dust content of the lower atmosphere.
The second layer of the atmosphere is stratosphere.
It starts from the troposphere as a narrow zone (1-3 km) with a constant temperature (tropopause) and extends to heights of about 80 km. A feature of the stratosphere is the progressive rarefaction of the air, the exceptionally high intensity of ultraviolet radiation, the absence of water vapor, the presence of a large amount of ozone and the gradual increase in temperature. The high content of ozone causes a number of optical phenomena (mirages), causes the reflection of sounds and has a significant effect on the intensity and spectral composition of electromagnetic radiation. In the stratosphere there is a constant mixing of air, so its composition is similar to the air of the troposphere, although its density at the upper boundaries of the stratosphere is extremely low. The prevailing winds in the stratosphere are westerly, and in the upper zone there is a transition to easterly winds.
The third layer of the atmosphere is ionosphere, which starts from the stratosphere and extends to altitudes of 600-800 km.
Distinctive features of the ionosphere are the extreme rarefaction of the gaseous medium, a high concentration of molecular and atomic ions and free electrons, as well as high temperature. The ionosphere affects the propagation of radio waves, causing their refraction, reflection and absorption.
The main source of ionization in the high layers of the atmosphere is the ultraviolet radiation of the Sun. In this case, electrons are knocked out of the gas atoms, the atoms turn into positive ions, and the knocked-out electrons remain free or are captured by neutral molecules with the formation of negative ions. The ionization of the ionosphere is influenced by meteors, corpuscular, X-ray and gamma radiation of the Sun, as well as the seismic processes of the Earth (earthquakes, volcanic eruptions, powerful explosions), which generate acoustic waves in the ionosphere, which increase the amplitude and speed of oscillations of atmospheric particles and contribute to the ionization of gas molecules and atoms (see Aeroionization).
The electrical conductivity in the ionosphere, associated with a high concentration of ions and electrons, is very high. The increased electrical conductivity of the ionosphere plays an important role in the reflection of radio waves and the occurrence of auroras.
The ionosphere is the area of flights of artificial earth satellites and intercontinental ballistic missiles. Currently, space medicine is studying the possible effects on the human body of flight conditions in this part of the atmosphere.
Fourth, outer layer of the atmosphere - exosphere. From here, atmospheric gases are scattered into the world space due to dissipation (overcoming the forces of gravity by molecules). Then there is a gradual transition from the atmosphere to interplanetary outer space. The exosphere differs from the latter by the presence of a large number of free electrons that form the 2nd and 3rd radiation belts of the Earth.
The division of the atmosphere into 4 layers is very arbitrary. So, according to electrical parameters, the entire thickness of the atmosphere is divided into 2 layers: the neutrosphere, in which neutral particles predominate, and the ionosphere. The temperature distinguishes the troposphere, stratosphere, mesosphere and thermosphere, separated respectively by tropo-, strato- and mesopauses. The layer of the atmosphere located between 15 and 70 km and characterized by a high content of ozone is called the ozonosphere.
For practical purposes, it is convenient to use the International Standard Atmosphere (MCA), for which the following conditions are accepted: the pressure at sea level at t ° 15 ° is 1013 mbar (1.013 X 10 5 nm 2, or 760 mm Hg); the temperature decreases by 6.5° per 1 km to a level of 11 km (conditional stratosphere), and then remains constant. In the USSR, the standard atmosphere GOST 4401 - 64 was adopted (Table 3).
Precipitation. Since the bulk of the atmospheric water vapor is concentrated in the troposphere, the processes of phase transitions of water, which cause precipitation, proceed mainly in the troposphere. Tropospheric clouds usually cover about 50% of the entire earth's surface, while clouds in the stratosphere (at altitudes of 20-30 km) and near the mesopause, called mother-of-pearl and noctilucent clouds, respectively, are observed relatively rarely. As a result of the condensation of water vapor in the troposphere, clouds form and precipitation occurs.
According to the nature of precipitation, precipitation is divided into 3 types: continuous, torrential, drizzling. The amount of precipitation is determined by the thickness of the layer of fallen water in millimeters; precipitation is measured by rain gauges and precipitation gauges. Precipitation intensity is expressed in millimeters per minute.
The distribution of precipitation in certain seasons and days, as well as over the territory, is extremely uneven, due to the circulation of the atmosphere and the influence of the Earth's surface. Thus, on the Hawaiian Islands, on average, 12,000 mm falls per year, and in the driest regions of Peru and the Sahara, precipitation does not exceed 250 mm, and sometimes does not fall for several years. In the annual dynamics of precipitation, the following types are distinguished: equatorial - with a maximum of precipitation after the spring and autumn equinoxes; tropical - with a maximum of precipitation in summer; monsoon - with a very pronounced peak in summer and dry winter; subtropical - with maximum precipitation in winter and dry summer; continental temperate latitudes - with a maximum of precipitation in summer; marine temperate latitudes - with a maximum of precipitation in winter.
The entire atmospheric-physical complex of climatic and meteorological factors that make up the weather is widely used to promote health, hardening, and for medicinal purposes (see Climatotherapy). Along with this, it has been established that sharp fluctuations in these atmospheric factors can adversely affect the physiological processes in the body, causing the development of various pathological conditions and the exacerbation of diseases, which are called meteotropic reactions (see Climatopathology). Of particular importance in this regard are frequent, long-term disturbances of the atmosphere and abrupt fluctuations in meteorological factors.
Meteotropic reactions are observed more often in people suffering from diseases of the cardiovascular system, polyarthritis, bronchial asthma, peptic ulcer, skin diseases.
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