Vertical structure of the atmosphere. Determining the altitude of condensation and sublimation levels Temperature change with altitude

To somewhat simplify the consideration of the issue, the atmosphere is divided into three main layers. Atmospheric stratification is primarily the result of unequal changes in air temperature with height. The lower two layers are relatively homogeneous in composition. For this reason they are usually said to form a homosphere.

Troposphere. The lower layer of the atmosphere is called the troposphere. This term itself means “sphere of rotation” and is associated with the turbulence characteristics of this layer. All changes in weather and climate are the result of physical processes occurring in this layer. In the 18th century, since the study of the atmosphere was limited only to this layer, it was believed that what was discovered in it A decrease in air temperature with height is also inherent in the rest of the atmosphere.

Various energy transformations occur primarily in the troposphere. Due to the continuous contact of air with the earth's surface, as well as the entry of energy into it from space, it begins to move. 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, under the influence of the rotation of our planet, it is also somewhat flattened above the poles and swells above 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. However, depending on the measurement point, the temperature may be slightly different. Thus, over the island of Java at the upper boundary of the troposphere, the air temperature drops to a record low of -95°C.

The upper boundary of the troposphere is called the tropopause. More than 75% of the atmosphere's mass lies below the tropopause. In the tropics, about 90% of the mass of the atmosphere is located within the troposphere.

The tropopause was discovered in 1899, when a minimum was found in the vertical temperature profile at a certain altitude, and then the temperature increased slightly. The beginning of this increase marks the transition to the next layer of the atmosphere - the stratosphere.

Stratosphere. The term stratosphere means “layer sphere” and reflects the previous 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 peculiarity is, in particular, a sharp increase in air temperature compared to its exceptionally low values ​​​​at the tropopause The temperature in the stratosphere rises to approximately -40 ° C. This increase in temperature is explained by the reaction of ozone formation - one of the main chemical reactions occurring in the atmosphere.

Ozone is a special form of oxygen. Unlike the usual diatomic oxygen molecule (O2). Ozone consists of its triatomic molecules (Oz). It appears as a result of the interaction of ordinary oxygen with oxygen entering the upper layers of 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. In the ozonosphere, ultraviolet rays interact most frequently and most strongly with atmospheric oxygen. causes the breakdown of ordinary diatomic oxygen molecules into individual atoms. In turn, the oxygen atoms often reattach to the diatomic molecules and form ozone molecules. In the same way, individual oxygen atoms combine to form diatomic molecules. The intensity of ozone formation turns out to be sufficient for a layer of high ozone concentration to exist in the 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 existence is created earthly forms life. Perhaps in the past, Earth received large quantity energy than now, which influenced the emergence of primary forms of life on our planet. But modern living organisms could not withstand more significant amounts of ultraviolet radiation coming from the Sun.

The ozonosphere absorbs the part 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).

At altitudes from 50 to 80 km there is a layer of the atmosphere called the mesosphere. The word "mesosphere" means "intermediate sphere", where the air temperature continues to decrease with height.

Above the mesosphere, in a layer called the thermosphere, temperatures rise again with altitude up to about 1000°C and then drop very quickly to -96°C. However, it does not drop indefinitely, then the temperature increases again.

The division of the atmosphere into separate layers is quite easy to notice by the peculiarities of temperature changes with height in each layer.

Unlike the previously mentioned layers, the ionosphere is not highlighted. according to temperature. main feature ionosphere - high degree of ionization of atmospheric gases. This ionization is caused by the absorption of solar energy by atoms of various gases. Ultraviolet and other solar rays, carrying high-energy quanta, entering the atmosphere, ionize nitrogen and oxygen atoms - electrons located in outer orbits are removed from the atoms. By losing electrons, the atom acquires a positive charge. If an electron is added to an atom, the atom becomes negatively charged. Thus, the ionosphere is a region of 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

Layer F has similar properties. It is also called Appleton's 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 is often called the exosphere.

This term refers to the existence of the outskirts of space near the Earth. It is difficult to determine exactly where space ends and begins, since with altitude the density of atmospheric gases gradually decreases and itself gradually turns into almost a vacuum, in which only individual molecules are found. With removal from earth's surface atmospheric gases experience less and less gravity of the planet and from a certain height tend to leave the earth's gravitational field. 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.

In the troposphere, the air temperature decreases with height, as noted, on average by 0.6 "C for every 100 m of height. However, in the surface layer, the distribution of temperature can be different: it can decrease, increase, or remain constant. Idea of ​​distribution temperature with height gives the vertical temperature gradient (VTG):

VGT = (/„ - /B)/(ZB -

where /n - /v - temperature difference at the lower and upper levels, °C; ZB - ZH - height difference, m. Usually the VGT is calculated per 100 m of height.

In the surface layer of the atmosphere, the VGT can be 1000 times higher than the average for the troposphere

The value of VGT in the surface layer depends on weather conditions (in clear weather it is greater than in cloudy weather), time of year (more in summer than in winter) and time of day (more during the day than at night). Wind reduces the VGT, since when the air is mixed, its temperature at different altitudes is equalized. Above moist soil, the VGT in the ground layer sharply decreases, and above bare soil (fallow field) the VGT is greater than over dense crops or meadows. This is due to differences in the temperature regime of these surfaces (see Chapter 3).

As a result of a certain combination of these factors, the VGT near the surface, calculated per 100 m of height, can be more than 100 °C/100 m. In such cases, thermal convection occurs.

The change in air temperature with height determines the sign of the VGT: if VGT > 0, then the temperature decreases with distance from the active surface, which usually happens during the day and summer (Fig. 4.4); if VGT = 0, then the temperature does not change with height; if VGT< 0, то температура увеличивается с высотой и такое рас­пределение температуры называют инверсией.

Depending on the conditions for the formation of inversions in the surface layer of the atmosphere, they are divided into radiative and advective.

1. Radiation inversions occur during radiation cooling of the earth's surface. Such inversions form at night during the warm season, and are also observed during the day in winter. Therefore, radiation inversions are divided into nighttime (summer) and winter.

Night inversions are established in clear, quiet weather after the radiation balance passes through 0 1.0...1.5 hours before sunset. During the night they intensify and reach their greatest power before sunrise. After sunrise, the active surface and air warm up, which destroys the inversion. The height of the inversion layer is most often several tens of meters, but under certain conditions (for example, in closed valleys surrounded by significant elevations) it can reach 200 m or more. This is facilitated by the flow of cooled air from the slopes into the valley. Cloudiness weakens the inversion, and wind speeds of more than 2.5...3.0 m/s destroy it. Under the canopy of dense grass, crops, and forests in summer, inversions are also observed during the day.

Nighttime radiation inversions in spring and autumn, and in some places in summer, can cause a decrease in soil and air surface temperatures to negative values(frost), which causes damage to many cultivated plants.

Winter inversions occur in clear, calm weather under short-day conditions, when the cooling of the active surface continuously increases every day; they may persist for several weeks, weakening slightly during the day and becoming stronger again at night.

Radiation inversions are especially intensified under highly heterogeneous terrain. The cooling air flows into lowlands and basins, where weakened turbulent mixing contributes to its further cooling. Radiation inversions associated with terrain features are usually called orographic.

2. Advective inversions are formed when warm air advects (moves) onto a cold underlying surface, which cools the adjacent layers of advancing air. These inversions also include snow inversions. They arise during the advection of air having a temperature above O "C onto a surface covered with snow. A decrease in temperature in the lowest layer in this case is associated with the heat consumption for melting snow.

INDICATORS OF TEMPERATURE REGIME IN A GIVEN LOCATION AND THE HEAT REQUIREMENT OF PLANTS

When assessing the temperature regime large territory or a separate point, temperature characteristics are applied for the year or for individual periods (growing season, season, month, decade and day). The main ones of these indicators are the following.

Average daily temperature is the arithmetic mean of temperatures measured during all observation periods. At weather stations Russian Federation air temperature is measured eight times a day. By summing the results of these measurements and dividing the sum by 8, the average daily air temperature is obtained.

Average monthly temperature is the arithmetic mean of the average daily temperatures for the entire day of the month.

The average annual temperature is the arithmetic mean of the average daily (or average monthly) temperatures for the entire year.

The average code air temperature gives only a general idea of ​​the amount of heat; it does not characterize the annual temperature variation. Thus, the average annual temperature in the south of Ireland and in the steppes of Kalmykia, located at the same latitude, is close (9°C). But in Ireland the average January temperature is 5...8 "C, and the meadows are green all winter here, and in the steppes of Kalmykia the average January temperature is -5...-8 °C. In the summer in Ireland it is cool: 14 °C, and The average July temperature in Kalmykia is 23...26 °C.

Therefore for more full characteristics The annual variation of temperature in a given place uses data on the average temperature of the coldest (January) and warmest (July) months.

However, all averaged characteristics do not give an accurate idea of ​​the daily and annual temperature variations, i.e., precisely the conditions that are especially important for agricultural production. In addition to the average temperatures are the maximum and minimum temperatures, amplitude. For example, knowing the minimum temperature in winter months, one can judge the overwintering conditions of winter crops and fruit and berry plantings. Data about maximum temperature show in winter the frequency of thaws and their intensity, and in summer - the number of hot days when damage to grain is possible during the filling period, etc.

Extreme temperatures are distinguished: absolute maximum (minimum) - the highest (lowest) temperature for the entire observation period; the average of the absolute maximums (minimums) - the arithmetic mean of the absolute extremes; average maximum (minimum) - the arithmetic average of all extreme temperatures, for example, for a month, season, year. Moreover, they can be calculated both for a long-term observation period and for an actual month, year, etc.

The amplitude of the daily and annual variations in temperature characterizes the degree of continental climate: the greater the amplitude, the more continental the climate.

The temperature regime in a given area for a certain period is also characterized by the sums of average daily temperatures above or below a certain limit. For example, in climate reference books and atlases the sums of temperatures above 0, 5, 10 and 15 °C are given, as well as below -5 and -10 °C.

Visual representation of geographical distribution indicators of the temperature regime are provided by maps on which isotherms are drawn - lines of equal temperature values ​​or sums of temperatures (Fig. 4.7). Maps, for example, of temperature sums are used to justify the placement of crops (plantings) of cultural plants with different heat requirements.

To clarify the thermal conditions necessary for plants, the sums of day and night temperatures are also used, since the average daily temperature and its sums neutralize thermal differences in diurnal course air temperature.

Studying the thermal regime separately for day and night has deep physiological significance. It is known that all processes occurring in the plant and animal world are subject to natural rhythms determined by external conditions, that is, they are subject to the law of the so-called “biological” clock. For example, according to (1964), for optimal growth conditions for tropical plants, the difference between day and night temperatures should be 3...5 ° C, for plants temperate zone-5...7, and for desert plants - 8 °C or more. The study of day and night temperatures acquires special meaning to increase the productivity of agricultural plants, which is determined by the relationship between two processes - assimilation and respiration, occurring in qualitatively different light and dark hours of the day for plants.

The average day and night temperatures and their sums indirectly take into account the latitudinal variability of day and night lengths, as well as changes in the continentality of the climate and the influence of various relief forms on the temperature regime.

The sums of average daily air temperatures that are close for a pair of weather stations located approximately at the same latitude, but significantly different in longitude, i.e., located in different conditions continental climate are shown in table 4.1.

In the more continental eastern regions, the sums of daytime temperatures are 200...500 °C higher, and the sums of night temperatures are 300 °C less than in the western and especially maritime regions, which explains long ago known fact- acceleration of the development of agricultural crops in a sharply continental climate.

Plant heat requirements are expressed as sums of active and effective temperatures. In agricultural meteorology, active temperature is the average daily air (or soil) temperature above the biological minimum for crop development. Effective temperature is the average daily air (or soil) temperature reduced by the biological minimum value.

Plants develop only if the average daily temperature exceeds their biological minimum, which is, for example, 5 °C for spring wheat, 10 °C for corn, 13 °C for cotton (15 °C for southern cotton varieties). The sums of active and effective temperatures are established both for individual interphase periods and for the entire growing season of many varieties and hybrids of the main agricultural crops (Table 11.1).

The sums of active and effective temperatures also express the need for warmth of poikilothermic (cold-blooded) organisms both during the ontogenetic period and throughout the century. there is a biological cycle.

When calculating the sums of average daily temperatures characterizing the heat needs of plants and poikilothermic organisms, it is necessary to introduce a correction for ballast temperatures that do not accelerate growth and development, i.e., take into account the upper temperature level for crops and organisms. For most plants and pests of the temperate zone this will be an average daily temperature exceeding 20...25 "C.

Task:

It is known that at an altitude of 750 meters above sea level the temperature is +22 o C. Determine the air temperature at the altitude:

a) 3500 meters above sea level

b) 250 meters above sea level

Solution:

We know that when the altitude changes by 1000 meters (1 km), the air temperature changes by 6 o C. Moreover, with an increase in altitude, the air temperature decreases, and with a decrease, it increases.

a) 1. Determine the difference in heights: 3500 m -750 m = 2750 m = 2.75 km

2. Determine the difference in air temperatures: 2.75 km × 6 o C = 16.5 o C

3. Let’s determine the air temperature at an altitude of 3500 m: 22 o C - 16.5 o C = 5.5 o C

Answer: at an altitude of 3500 m the air temperature is 5.5 o C.

b) 1. Determine the height difference: 750 m -250 m = 500 m = 0.5 km

2. Determine the difference in air temperatures: 0.5 km × 6 o C = 3 o C

3. Determine the air temperature at an altitude of 250 m: 22 o C + 3 o C = 25 o C

Answer: at an altitude of 250 m the air temperature is 25 o C.

2. Determination of atmospheric pressure depending on altitude

Task:

It is known that at an altitude of 2205 meters above sea level the atmospheric pressure is 550 mm mercury. Determine the atmospheric pressure at altitude:

a) 3255 meters above sea level

b) 0 meters above sea level

Solution:

We know that when the altitude changes by 10.5 meters, the atmospheric pressure changes by 1 mmHg. Art. Moreover, with increasing altitude, atmospheric pressure decreases, and with decreasing altitude, it increases.

a) 1. Determine the difference in heights: 3255 m - 2205 m = 1050 m

2. Determine the difference in atmospheric pressure: 1050 m: 10.5 m = 100 mm Hg.

3. Let us determine the atmospheric pressure at an altitude of 3255 m: 550 mm Hg. - 100 mm Hg. = 450 mmHg

Answer: at an altitude of 3255 m, the atmospheric pressure is 450 mm Hg.

b) 1. Determine the difference in heights: 2205 m - 0 m = 2205 m

2. Let's determine the difference in atmospheric pressure: 2205 m: 10.5 m = 210 mm Hg. Art.

3. Determine the atmospheric pressure at an altitude of 0 m: 550 mm Hg. + 210 mm Hg. Art. = 760 mm Hg. Art.

Answer: at an altitude of 0 m the atmospheric pressure is 760 mm Hg.

3. Beaufort scale

(wind speed scale)

In the troposphere, air temperature decreases with altitude, as noted, by an average of 0.6 ºС for every 100 m of altitude. However, in the surface layer the temperature distribution can be different: it can decrease, increase, or remain constant. The vertical temperature gradient (VTG) gives an idea of ​​the distribution of temperature with height:

The value of VGT in the surface layer depends on weather conditions (in clear weather it is greater than in cloudy weather), time of year (more in summer than in winter) and time of day (more during the day than at night). Wind reduces the VGT, since when the air is mixed, its temperature at different altitudes is equalized. Above moist soil, the VGT in the ground layer sharply decreases, and above bare soil (fallow field) the VGT is greater than over dense crops or meadows. This is due to differences in the temperature regime of these surfaces.

The change in air temperature with height determines the sign of the VGT: if VGT > 0, then the temperature decreases with distance from the active surface, which usually happens during the day and summer; if VGT = 0, then the temperature does not change with height; if VGT< 0, то температура увеличивается с высотой и такое распределение температуры называют инверсией.

Depending on the conditions for the formation of inversions in the surface layer of the atmosphere, they are divided into radiative and advective.

1. Radiation inversions occur during radiation cooling of the earth's surface. Such inversions form at night during the warm season, and are also observed during the day in winter. Therefore, radiation inversions are divided into nighttime (summer) and winter.

2. Advective inversions are formed by the advection (movement) of warm air onto a cold underlying surface, which cools the adjacent layers of advancing air. These inversions also include snow inversions. They occur when air with a temperature above 0°C advects onto a surface covered with snow. The decrease in temperature in the lowest layer in this case is associated with the heat consumed by snow melting.

Air temperature measurement

At meteorological stations, thermometers are installed in a special booth, called a psychrometric booth, the walls of which are louvered. The rays of the Sun do not penetrate into such a booth, but at the same time air has free access to it.

Thermometers are installed on a tripod so that the reservoirs are located at a height of 2 m from the active surface.

Urgent air temperature is measured with a mercury psychrometric thermometer TM-4, which is installed vertically. At temperatures below -35°C, use a low-degree alcohol thermometer TM-9.

Extreme temperatures are measured using maximum TM-1 and minimum TM-2 thermometers, which are laid horizontally.

For continuous recording of air temperature, use thermograph M-16A, which is placed in a louvred recording booth. Depending on the rotation speed of the drum, thermographs are available for daily or weekly use.

In crops and plantings, the air temperature is measured without disturbing the vegetation cover. For this purpose, an aspiration psychrometer is used.

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 usually divided into several next friend behind each other in height above the surface of the zones.

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 total mass atmospheric air(although by volume it makes up 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 drops 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. Stops at absolute zero thermal movement molecules. 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. Atmosphere pressure 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 most often used concept 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 only exist 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, while 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...