The Earth receives from the Sun 1.36 * 10v24 cal of heat per year. Compared to this amount of energy, the remaining amount of radiant energy reaching the Earth's surface is negligible. Thus, the radiant energy of stars is one hundred millionth solar energy, cosmic radiation - two billionths, internal warmth Earth at its surface is equal to one five-thousandth of the solar heat.
Radiation of the Sun - solar radiation- is the main source of energy for almost all processes occurring in the atmosphere, hydrosphere and in the upper layers of the lithosphere.
The unit of measurement of the intensity of solar radiation is the number of calories of heat absorbed by 1 cm2 of an absolutely black surface perpendicular to the direction of the sun's rays in 1 minute (cal/cm2*min).

The flow of radiant energy from the Sun, reaching the earth's atmosphere, is very constant. Its intensity is called the solar constant (Io) and is taken on average to be 1.88 kcal/cm2 min.
The value of the solar constant fluctuates depending on the distance of the Earth from the Sun and on solar activity. Its fluctuations during the year are 3.4-3.5%.
If the sun's rays everywhere fell vertically on the earth's surface, then in the absence of an atmosphere and at a solar constant of 1.88 cal/cm2*min, each square centimeter it would receive 1000 kcal per year. Due to the fact that the Earth is spherical, this amount is reduced by 4 times, and 1 sq. cm receives an average of 250 kcal per year.
The amount of solar radiation received by the surface depends on the angle of incidence of the rays.
Maximum amount radiation receives a surface perpendicular to the direction of the sun's rays, because in this case all the energy is distributed to a site with a cross section, equal to the cross section beam of rays - a. With oblique incidence of the same beam of rays, the energy is distributed over a large area (section c) and a unit surface receives a smaller amount of it. The smaller the angle of incidence of the rays, the lower the intensity of solar radiation.
The dependence of the intensity of solar radiation on the angle of incidence of rays is expressed by the formula:

I1 = I0 * sinh,

where I0 is the intensity of solar radiation at a sheer incidence of rays. Outside the atmosphere, the solar constant;
I1 - the intensity of solar radiation when the sun's rays fall at an angle h.
I1 is as many times less than I0, how many times the section a is less than the section b.
Figure 27 shows that a / b \u003d sin A.
The angle of incidence of the sun's rays (the height of the Sun) is equal to 90 ° only at latitudes from 23 ° 27 "N to 23 ° 27" S. (i.e. between the tropics). At other latitudes, it is always less than 90° (Table 8). According to the decrease in the angle of incidence of rays, the intensity of solar radiation arriving at the surface at different latitudes should also decrease. Since the height of the Sun does not remain constant throughout the year and during the day, the amount of solar heat received by the surface changes continuously.

The amount of solar radiation received by the surface is directly related to from the duration of its exposure to sunlight.

In the equatorial zone outside the atmosphere, the amount of solar heat during the year does not experience big fluctuations, whereas in high latitudes these fluctuations are very large (see Table 9). AT winter period differences in solar heat gain between high and low latitudes are especially significant. AT summer period, in conditions of continuous illumination, the polar regions receive the maximum amount of solar heat per day on Earth. On the day of the summer solstice in the northern hemisphere, it is 36% higher than the daily amount of heat at the equator. But since the duration of the day at the equator is not 24 hours (as at this time at the pole), but 12 hours, the amount of solar radiation per unit of time at the equator remains the largest. The summer maximum of the daily sum of solar heat, observed at about 40-50° latitude, is associated with a relatively long day (greater than at this time by 10-20° latitude) at a significant height of the Sun. Differences in the amount of heat received by the equatorial and polar regions are smaller in summer than in winter.
The southern hemisphere receives more heat in summer than the northern one, and vice versa in winter (it is affected by the change in the distance of the Earth from the Sun). And if the surface of both hemispheres were completely homogeneous, the annual amplitudes of temperature fluctuations in the southern hemisphere would be greater than in the northern.
Solar radiation in the atmosphere undergoes quantitative and qualitative changes.
Even an ideal, dry and clean atmosphere absorbs and scatters rays, reducing the intensity of solar radiation. The weakening effect of the real atmosphere, containing water vapor and solid impurities, on solar radiation is much greater than the ideal one. The atmosphere (oxygen, ozone, carbon dioxide, dust and water vapor) absorbs mainly ultraviolet and infrared rays. The radiant energy of the Sun absorbed by the atmosphere is converted into other types of energy: thermal, chemical, etc. In general, absorption weakens solar radiation by 17-25%.
Molecules of atmospheric gases scatter rays with relatively short waves - violet, blue. This is what explains the blue color of the sky. Impurities equally scatter rays with waves of different wavelengths. Therefore, with a significant content of them, the sky acquires a whitish tint.
Due to the scattering and reflection of the sun's rays by the atmosphere, daylight is observed on cloudy days, objects in the shade are visible, and the phenomenon of twilight occurs.
The longer the path of the beam in the atmosphere, the greater its thickness it must pass and the more significantly the solar radiation is attenuated. Therefore, with elevation, the influence of the atmosphere on radiation decreases. The length of the path of sunlight in the atmosphere depends on the height of the Sun. If we take as a unit the length of the path of the solar beam in the atmosphere at the height of the Sun 90 ° (m), the relationship between the height of the Sun and the length of the path of the beam in the atmosphere will be as shown in Table. ten.

The total attenuation of radiation in the atmosphere at any height of the Sun can be expressed by the Bouguer formula: Im = I0 * pm, where Im is the intensity of solar radiation changed in the atmosphere y earth's surface; I0 - solar constant; m is the path of the beam in the atmosphere; at a solar altitude of 90 ° it is equal to 1 (the mass of the atmosphere), p is the transparency coefficient ( fractional number, showing what fraction of radiation reaches the surface at m=1).
At a height of the Sun of 90°, at m=1, the intensity of solar radiation near the earth's surface I1 is p times less than Io, i.e. I1=Io*p.
If the height of the Sun is less than 90°, then m is always greater than 1. The path of a solar ray can consist of several segments, each of which is equal to 1. The intensity of solar radiation at the border between the first (aa1) and second (a1a2) segments I1 is obviously equal to Io *p, radiation intensity after passing the second segment I2=I1*p=I0 p*p=I0 p2; I3=I0p3 etc.

The transparency of the atmosphere is not constant and is not the same in various conditions. The ratio of the transparency of the real atmosphere to the transparency of the ideal atmosphere - the turbidity factor - is always greater than one. It depends on the content of water vapor and dust in the air. With an increase in geographical latitude, the turbidity factor decreases: at latitudes from 0 to 20 ° N. sh. it is equal to 4.6 on average, at latitudes from 40 to 50 ° N. sh. - 3.5, at latitudes from 50 to 60 ° N. sh. - 2.8 and at latitudes from 60 to 80 ° N. sh. - 2.0. In temperate latitudes, the turbidity factor is less in winter than in summer, and less in the morning than in the afternoon. It decreases with height. The greater the turbidity factor, the greater the attenuation of solar radiation.
Distinguish direct, diffuse and total solar radiation.
Part of the solar radiation that penetrates through the atmosphere to the earth's surface is direct radiation. Part of the radiation scattered by the atmosphere is converted into diffuse radiation. All solar radiation entering the earth's surface, direct and diffuse, is called total radiation.
The ratio between direct and scattered radiation varies considerably depending on the cloudiness, dustiness of the atmosphere, and also on the height of the Sun. In clear skies, the fraction of scattered radiation does not exceed 0.1%; in cloudy skies, diffuse radiation can be greater than direct radiation.
At a low altitude of the Sun, the total radiation consists almost entirely of scattered radiation. At a solar altitude of 50° and a clear sky, the fraction of scattered radiation does not exceed 10-20%.
Maps of average annual and monthly values total radiation allow us to notice the main patterns in its geographical distribution. The annual values ​​of total radiation are distributed mainly zonal. The largest annual amount of total radiation on Earth is received by the surface in tropical inland deserts (Eastern Sahara and central part Arabia). A noticeable decrease in total radiation at the equator is caused by high air humidity and high cloudiness. In the Arctic, the total radiation is 60-70 kcal/cm2 per year; in the Antarctic, due to the frequent recurrence of clear days and the greater transparency of the atmosphere, it is somewhat larger.

In June, the northern hemisphere receives the largest amounts of radiation, and especially the inland tropical and subtropical regions. The amounts of solar radiation received by the surface in the temperate and polar latitudes of the northern hemisphere differ little, owing mainly to the long duration of the day in the polar regions. Zoning in the distribution of total radiation above. continents in the northern hemisphere and tropical latitudes southern hemisphere almost not expressed. It is better manifested in the northern hemisphere over the Ocean and is clearly expressed in the extratropical latitudes of the southern hemisphere. At the southern polar circle, the value of total solar radiation approaches 0.
In December, the largest amounts of radiation enter the southern hemisphere. The high-lying ice surface of Antarctica, with high air transparency, receives significantly more total radiation than the surface of the Arctic in June. There is a lot of heat in the deserts (Kalahari, Great Australian), but due to the greater oceanicity of the southern hemisphere (the influence of high air humidity and cloudiness), its amounts here are somewhat less than in June at the same latitudes of the northern hemisphere. In the equatorial and tropical latitudes of the northern hemisphere, the total radiation varies relatively little, and the zoning in its distribution is clearly expressed only to the north of the northern tropic. With increasing latitude, the total radiation decreases rather rapidly; its zero isoline passes somewhat north of the Arctic Circle.
The total solar radiation, falling on the Earth's surface, is partially reflected back into the atmosphere. The ratio of the amount of radiation reflected from a surface to the amount of radiation incident on that surface is called albedo. Albedo characterizes the reflectivity of a surface.
The albedo of the earth's surface depends on its condition and properties: color, humidity, roughness, etc. Freshly fallen snow has the highest reflectivity (85-95%). A calm water surface reflects only 2-5% of the sun's rays when it falls vertically, and almost all the rays falling on it (90%) when the sun is low. Albedo of dry chernozem - 14%, wet - 8, forest - 10-20, meadow vegetation - 18-30, sandy desert surface - 29-35, sea ice surface - 30-40%.
The large albedo of the ice surface, especially when covered with fresh snow (up to 95%), is the reason for low temperatures in the polar regions in summer, when the arrival of solar radiation is significant there.
Radiation of the earth's surface and atmosphere. Any body with a temperature above absolute zero(greater than minus 273°), emits radiant energy. The total emissivity of a blackbody is proportional to the fourth power of its absolute temperature (T):
E \u003d σ * T4 kcal / cm2 per minute (Stefan-Boltzmann law), where σ is a constant coefficient.
The higher the temperature radiating body, the shorter the wavelength of the emitted nm rays. The incandescent Sun sends into space shortwave radiation. The earth's surface, absorbing short-wave solar radiation, heats up and also becomes a source of radiation (terrestrial radiation). Ho, since the temperature of the earth's surface does not exceed several tens of degrees, its long-wave radiation, invisible.
Earth radiation is largely retained by the atmosphere (water vapor, carbon dioxide, ozone), but rays with a wavelength of 9-12 microns freely go beyond the atmosphere, and therefore the Earth loses some of its heat.
The atmosphere, absorbing part of the solar radiation passing through it and more than half of the earth's, itself radiates energy both into the world space and to the earth's surface. Atmospheric radiation directed towards the earth's surface towards the earth's surface is called opposite radiation. This radiation, like the terrestrial, long-wave, invisible.
Two streams of long-wave radiation meet in the atmosphere - the radiation of the Earth's surface and the radiation of the atmosphere. The difference between them, which determines the actual loss of heat by the earth's surface, is called efficient radiation. Effective radiation is the greater, the higher the temperature of the radiating surface. Air humidity reduces the effective radiation, its clouds greatly reduce it.
The highest value of the annual sums of effective radiation is observed in tropical deserts- 80 kcal/cm2 per year - thanks to high temperature surface, dryness of the air and clarity of the sky. At the equator, with high air humidity, the effective radiation is only about 30 kcal/cm2 per year, and its value for land and for the ocean differs very little. The lowest effective radiation in the polar regions. In temperate latitudes, the earth's surface loses about half of the amount of heat that it receives from the absorption of total radiation.
The ability of the atmosphere to pass the short-wave radiation of the Sun (direct and diffuse radiation) and delay the long-wave radiation of the Earth is called the greenhouse (greenhouse) effect. Due to the greenhouse effect, the average temperature of the earth's surface is +16°, in the absence of an atmosphere it would be -22° (38° lower).
Radiation balance (residual radiation). The earth's surface simultaneously receives radiation and gives it away. The arrival of radiation is the total solar radiation and the counter radiation of the atmosphere. Consumption - the reflection of sunlight from the surface (albedo) and the own radiation of the earth's surface. The difference between the incoming and outgoing radiation is radiation balance, or residual radiation. The value of the radiation balance is determined by the equation

R \u003d Q * (1-α) - I,

where Q is the total solar radiation per unit surface; α - albedo (fraction); I - effective radiation.
If the input is greater than the output, the radiation balance is positive; if the input is less than the output, the balance is negative. At night, at all latitudes, the radiation balance is negative; during the day, until noon, it is positive everywhere, except for high latitudes in winter; in the afternoon - again negative. On average per day, the radiation balance can be both positive and negative (Table 11).


On the map of the annual sums of the radiation balance of the earth's surface, one can see abrupt change positions of isolines during their transition from land to the ocean. As a rule, the radiation balance of the Ocean surface exceeds the radiation balance of the land (the effect of albedo and effective radiation). The distribution of the radiation balance is generally zonal. On the Ocean in tropical latitudes, the annual values ​​of the radiation balance reach 140 kcal/cm2 (Arabian Sea) and do not exceed 30 kcal/cm2 near the border floating ice. Deviations from the zonal distribution of the radiation balance in the Ocean are insignificant and are caused by the distribution of clouds.
On land in the equatorial and tropical latitudes, the annual values ​​of the radiation balance vary from 60 to 90 kcal/cm2, depending on the moisture conditions. The largest annual sums of the radiation balance are noted in those areas where the albedo and effective radiation are relatively small (moist tropical forests, savannahs). Their lowest value is in very humid (large cloudiness) and in very dry (large effective radiation) regions. In temperate and high latitudes, the annual value of the radiation balance decreases with increasing latitude (the effect of a decrease in total radiation).
The annual sums of the radiation balance over central regions Antarctica are negative (a few calories per 1 cm2). In the Arctic, these values ​​are close to zero.
In July, the radiation balance of the earth's surface in a significant part of the southern hemisphere is negative. The zero balance line runs between 40 and 50°S. sh. The highest value of the radiation balance is reached on the surface of the Ocean in the tropical latitudes of the northern hemisphere and on the surface of some inland seas, such as the Black Sea (14-16 kcal/cm2 per month).
In January, the zero balance line is located between 40 and 50°N. sh. (over the oceans it rises somewhat to the north, over the continents it descends to the south). A significant part of the northern hemisphere has a negative radiation balance. The largest values ​​of the radiation balance are confined to the tropical latitudes of the southern hemisphere.
On average for the year, the radiation balance of the earth's surface is positive. In this case, the surface temperature does not increase, but remains approximately constant, which can only be explained by the continuous consumption of excess heat.
The radiation balance of the atmosphere consists of the solar and terrestrial radiation absorbed by it, on the one hand, and atmospheric radiation, on the other. It is always negative, since the atmosphere absorbs only a small part of solar radiation, and radiates almost as much as the surface.
The radiation balance of the surface and the atmosphere together, as a whole, for the entire Earth for a year is equal to zero on average, but in latitudes it can be both positive and negative.
The consequence of such a distribution of the radiation balance should be the transfer of heat in the direction from the equator to the poles.
Thermal balance. The radiation balance is the most important component of the heat balance. The surface heat balance equation shows how the incoming solar radiation energy is converted on the earth's surface:

where R is the radiation balance; LE - heat consumption for evaporation (L - latent heat of vaporization, E - evaporation);
P - turbulent heat exchange between the surface and the atmosphere;
A - heat exchange between the surface and underlying layers of soil or water.
The radiation balance of a surface is considered positive if the radiation absorbed by the surface exceeds the heat loss, and negative if it does not replenish them. All other terms of the heat balance are considered positive if they cause heat loss by the surface (if they correspond to heat consumption). As. all terms of the equation can change, the heat balance is constantly disturbed and restored again.
The equation of the heat balance of the surface considered above is approximate, since it does not take into account some secondary, but under specific conditions, factors that become important, for example, the release of heat during freezing, its consumption for thawing, etc.
The heat balance of the atmosphere consists of the radiation balance of the atmosphere Ra, the heat coming from the surface, Pa, the heat released in the atmosphere during condensation, LE, and the horizontal heat transfer (advection) Aa. The radiation balance of the atmosphere is always negative. The influx of heat as a result of moisture condensation and the magnitude of turbulent heat transfer are positive. Heat advection leads, on average per year, to its transfer from low latitudes to high latitudes: thus, it means heat consumption at low latitudes and arrival at high latitudes. In a multi-year derivation, the heat balance of the atmosphere can be expressed by the equation Ra=Pa+LE.
The heat balance of the surface and the atmosphere together as a whole is equal to 0 on a long-term average (Fig. 35).

The amount of solar radiation entering the atmosphere per year (250 kcal/cm2) is taken as 100%. Solar radiation, penetrating into the atmosphere, is partially reflected from the clouds and goes back beyond the atmosphere - 38%, partially absorbed by the atmosphere - 14%, and partially in the form of direct solar radiation reaches the earth's surface - 48%. Of the 48% that reach the surface, 44% are absorbed by it, and 4% are reflected. Thus, the Earth's albedo is 42% (38+4).
The radiation absorbed by the earth's surface is spent as follows: 20% is lost through effective radiation, 18% is spent on evaporation from the surface, 6% is spent on heating the air during turbulent heat transfer (total 24%). The loss of heat by the surface balances its arrival. The heat received by the atmosphere (14% directly from the Sun, 24% from the earth's surface), together with the effective radiation of the Earth, is directed into the world space. The Earth's albedo (42%) and radiation (58%) balance the influx of solar radiation to the atmosphere.

Solar radiation is the leading climate-forming factor and practically the only source of energy for all physical processes occurring on the earth's surface and in its atmosphere. It determines the vital activity of organisms, creating one or another temperature regime; leads to the formation of clouds and precipitation; is the fundamental cause of the general circulation of the atmosphere, thereby a huge impact on human life in all its manifestations. In construction and architecture, solar radiation is the most important environmental factor - the orientation of buildings, their constructive, space-planning, coloristic, plastic solutions and many other features depend on it.

According to GOST R 55912-2013 "Construction Climatology", the following definitions and concepts related to solar radiation are adopted:

• direct radiation - part of the total solar radiation entering the surface in the form of a beam of parallel rays coming directly from the visible disk of the sun;
• scattered solar radiation- part of the total solar radiation coming to the surface from the entire sky after scattering in the atmosphere;
• reflected radiation- part of the total solar radiation reflected from the underlying surface (including from the facades, roofs of buildings);
• solar radiation intensity- the amount of solar radiation passing per unit of time through a single area located perpendicular to the rays.

All values ​​of solar radiation in modern domestic state standards, joint ventures (SNiPs) and other regulatory documents related to construction and architecture are measured in kilowatts per hour per 1 m 2 (kW h / m 2). As a rule, a month is taken as a unit of time. To get the instantaneous (second) value of the power of the solar radiation flux (kW / m 2), the value given for the month should be divided by the number of days in a month, the number of hours in a day and seconds in hours.

In many early editions of building regulations and in many modern reference books on climatology, solar radiation values ​​are given in megajoules or kilocalories per m 2 (MJ / m 2, Kcal / m 2). The coefficients for the conversion of these quantities from one to another are given in Appendix 1.

physical entity. Solar radiation comes to Earth from the Sun. The Sun is the closest star to us, which is on average 149,450,000 km away from the Earth. In early July, when the Earth is farthest from the Sun (aphelion), this distance increases to 152 million km, and in early January it decreases to 147 million km (perihelion).

Inside the solar core, the temperature exceeds 5 million K, and the pressure is several billion times greater than that of the earth, as a result of which hydrogen turns into helium. In the course of this thermonuclear reaction, radiant energy is born, which propagates from the Sun in all directions in the form of electromagnetic waves. At the same time, a whole spectrum of wavelengths comes to the Earth, which in meteorology is usually divided into short-wave and long-wave sections. shortwave call radiation in the wavelength range from 0.1 to 4 microns (1 micron \u003d 10 ~ 6 m). Radiation with long lengths (from 4 to 120 microns) is referred to as longwave. Solar radiation is predominantly short-wave - the indicated wavelength range accounts for 99% of all energy solar radiation, while the earth's surface and atmosphere emit long-wave radiation, and can only reflect short-wave radiation.

The sun is a source of not only energy, but also light. Visible light occupies a narrow range of wavelengths, only from 0.40 to 0.76 microns, but 47% of all solar radiant energy is contained in this interval. Light with a wavelength of about 0.40 µm is perceived as violet, with a wavelength of about 0.76 µm as red. All other wavelengths are not perceived by the human eye; they are invisible to us 1 . Infrared radiation (from 0.76 to 4 microns) accounts for 44%, and ultraviolet (from 0.01 to 0.39 microns) - 9% of all energy. The maximum energy in the spectrum of solar radiation at the upper boundary of the atmosphere lies in the blue-blue region of the spectrum, and near the earth's surface - in the yellow-green.

A quantitative measure of solar radiation entering a certain surface is energy illumination, or flux of solar radiation, - the amount of radiant energy incident on a unit area per unit time. The maximum amount of solar radiation enters the upper boundary of the atmosphere and is characterized by the value of the solar constant. Solar constant - is the flux of solar radiation at the upper boundary of the earth's atmosphere through an area perpendicular to the sun's rays, at an average distance of the Earth from the Sun. According to the latest data approved by the World Meteorological Organization (WMO) in 2007, this value is 1.366 kW / m 2 (1366 W / m 2).

Much less solar radiation reaches the earth's surface, since as the sun's rays move through the atmosphere, the radiation undergoes a series significant changes. Part of it is absorbed by atmospheric gases and aerosols and passes into heat, i.e. goes to warm the atmosphere, and part is scattered and goes into a special form of diffuse radiation.

Process takeovers radiation in the atmosphere is selective in nature - different gases absorb it in different parts of the spectrum and to different degrees. The main gases that absorb solar radiation are water vapor (H 2 0), ozone (0 3) and carbon dioxide (CO 2). For example, as mentioned above, stratospheric ozone completely absorbs radiation harmful to living organisms with wavelengths shorter than 0.29 microns, which is why the ozone layer is a natural shield for the existence of life on Earth. On average, ozone absorbs about 3% of solar radiation. In the red and infrared regions of the spectrum, water vapor absorbs solar radiation most significantly. In the same region of the spectrum are the absorption bands of carbon dioxide, however

More details about light and color are discussed in other sections of the discipline "Architectural Physics".

in general, its absorption of direct radiation is small. Absorption of solar radiation occurs both by aerosols of natural and anthropogenic origin, especially strongly by soot particles. In total, about 15% of solar radiation is absorbed by water vapor and aerosols, and about 5% by clouds.

Scattering radiation is physical process interactions electromagnetic radiation and substances, during which molecules and atoms absorb part of the radiation, and then re-emit it in all directions. This is very important process, which depends on the ratio of the size of the scattering particles and the wavelength of the incident radiation. In absolutely clean air, where scattering is produced only by gas molecules, it obeys Rayleigh law, i.e. inversely proportional to the fourth power of the wavelength of the scattered rays. Thus, the blue color of the sky is the color of the air itself, due to the scattering of sunlight in it, since violet and blue rays are scattered by air much better than orange and red ones.

If there are particles in the air whose dimensions are comparable to the wavelength of radiation - aerosols, water droplets, ice crystals - then the scattering will not obey the Rayleigh law, and the scattered radiation will not be so rich in short-wavelength rays. On particles with a diameter greater than 1-2 microns, there will be no scattering, but diffuse reflection, which determines the whitish color of the sky.

Scattering plays huge role in the formation of natural illumination: in the absence of the Sun in the daytime, it creates diffuse (diffuse) light. If there were no scattering, it would be light only where direct sunlight would fall. Dusk and dawn, the color of the clouds at sunrise and sunset are also associated with this phenomenon.

So, solar radiation reaches the earth's surface in the form of two streams: direct and diffuse radiation.

direct radiation(5) comes to the earth's surface directly from the solar disk. In this case, the maximum possible amount of radiation will be received by a single site located perpendicular to the sun's rays (5). per unit horizontal surface will have a smaller amount of radiant energy Y, also called insolation:

Y \u003d? -8shA 0, (1.1)

where And 0- The height of the sun above the horizon, which determines the angle of incidence of the sun's rays on a horizontal surface.

scattered radiation(/)) comes to the earth's surface from all points of the firmament, with the exception of the solar disk.

All solar radiation reaching the earth's surface is called total solar radiation (0:

• (1.2)
• 0 = + /) = And 0+ /).

The arrival of these types of radiation significantly depends not only on astronomical causes, but also on cloudiness. Therefore, in meteorology it is customary to distinguish possible amounts of radiation observed under cloudless conditions, and actual amounts of radiation, which take place at real conditions cloudiness.

Not all solar radiation falling on the earth's surface is absorbed by it and converted into heat. Part of it is reflected and therefore lost by the underlying surface. This part is called reflected radiation(/? k), and its value depends on albedo ground surface (L to):

A k = - 100%.

The albedo value is measured in fractions of a unit or as a percentage. In construction and architecture, fractions of a unit are more often used. They also measure the reflectivity of building and finishing materials, the lightness of facades, etc. In climatology, albedo is measured as a percentage.

Albedo has a significant impact on the formation of the Earth's climate, as it is an integral indicator of the reflectivity of the underlying surface. It depends on the state of this surface (roughness, color, moisture) and varies over a very wide range. The highest albedo values ​​(up to 75%) are characteristic of freshly fallen snow, while the lowest values ​​are characteristic of the water surface during sheer sunlight (“3%). The albedo of the soil and vegetation surface varies on average from 10 to 30%.

If we consider the entire Earth as a whole, then its albedo is 30%. This value is called Earth's planetary albedo and represents the ratio of the reflected and scattered solar radiation leaving into space to the total amount of radiation entering the atmosphere.

On the territory of cities, the albedo is, as a rule, lower than in natural, undisturbed landscapes. The characteristic value of albedo for the territory of large cities with a temperate climate is 15-18%. In southern cities, the albedo is usually higher due to the use of lighter tones in the color of facades and roofs, in northern cities with dense buildings and dark color solutions of albedo buildings below. This allows in hot southern countries to reduce the amount of absorbed solar radiation, thereby reducing the thermal background of buildings, and in the northern cold regions, on the contrary, to increase the share of absorbed solar radiation, increasing the overall thermal background.

Absorbed radiation(* U P0GL) is also called balance of shortwave radiation (VK) and is the difference between the total and reflected radiation (two short-wave fluxes):

^abs \u003d 5 k = 0~ I K- (1.4)

It heats the upper layers of the earth's surface and everything that is located on it (vegetation cover, roads, buildings, structures, etc.), as a result of which they emit long-wave radiation invisible to the human eye. This radiation is often called own radiation of the earth's surface(? 3). Its value, according to the Stefan-Boltzmann law, is proportional to the fourth power of absolute temperature.

The atmosphere also emits long-wave radiation, most of which reaches the earth's surface and is almost completely absorbed by it. This radiation is called counter radiation of the atmosphere (E a). The counter radiation of the atmosphere increases with increasing cloudiness and air humidity and is a very important source of heat for the earth's surface. However, the long-wave radiation of the atmosphere is always slightly less than the earth's, due to which the earth's surface loses heat, and the difference between these values ​​is called effective radiation of the Earth (E ef).

On average, in temperate latitudes, the earth's surface through effective radiation loses about half of the amount of heat that it receives from absorbed solar radiation. By absorbing terrestrial radiation and sending counter radiation to the earth's surface, the atmosphere reduces the cooling of this surface at night. During the day, it does little to prevent the heating of the Earth's surface. This influence of the earth's atmosphere on the thermal regime of the earth's surface is called greenhouse effect. Thus, the phenomenon of the greenhouse effect consists in the retention of heat near the surface of the Earth. Big role this process is played by gases of technogenic origin, primarily carbon dioxide, the concentration of which in urban areas is especially high. But the main role still belongs to the gases of natural origin.

The main substance in the atmosphere that absorbs long-wave radiation from the Earth and sends back radiation is water vapor. It absorbs almost all long-wave radiation except for the wavelength range from 8.5 to 12 microns, which is called "transparency window" water vapor. Only in this interval does the terrestrial radiation pass into the world space through the atmosphere. In addition to water vapor, carbon dioxide strongly absorbs long-wave radiation, and it is in the transparency window of water vapor that ozone is much weaker, as well as methane, nitrogen oxide, chlorofluorocarbons (freons) and some other gas impurities.

Keeping heat close to the earth's surface is a very important process for sustaining life. Without it, the average temperature of the Earth would be 33 ° C lower than the current one, and living organisms could hardly live on the Earth. Therefore, the point is not in the greenhouse effect as such (after all, it arose from the moment the atmosphere was formed), but in the fact that under the influence anthropogenic activities going on gain this effect. The reason is the rapid growth in the concentration of greenhouse gases of technogenic origin, mainly CO 2 emitted during the combustion of fossil fuels. This can lead to the fact that with the same incoming radiation, the proportion of heat remaining on the planet will increase, and, consequently, the temperature of the earth's surface and atmosphere will also increase. Over the past 100 years, the air temperature of our planet has increased by an average of 0.6 ° C.

It is believed that when the concentration of CO 2 doubles relative to its pre-industrial value global warming will be about 3°C ​​(according to various estimates - from 1.5 to 5.5°C). Wherein biggest changes should occur in the high latitude troposphere during the autumn-winter period. As a result, the ice in the Arctic and Antarctica will begin to melt and the level of the World Ocean will begin to rise. This increase can range from 25 to 165 cm, which means that many cities located in the coastal zones of the seas and oceans will be flooded.

Thus, this is a very important issue affecting the lives of millions of people. With this in mind, in 1988 the first International Conference on the problem of anthropogenic change climate. Scientists have come to the conclusion that the consequences of an increase in the greenhouse effect due to an increase in the content of carbon dioxide in the atmosphere are second only to the consequences of a global nuclear war. At the same time, the Intergovernmental Panel on Climate Change (IPCC) was formed at the United Nations (UN). IPCC - Intergovernmental Panel on Climate Change), which studies the impact of an increase in surface temperature on the climate, the ecosystem of the World Ocean, the biosphere as a whole, including the life and health of the planet's population.

In 1992, the Framework Convention on Climate Change (FCCC) was adopted in New York, the main goal of which was proclaimed to ensure the stabilization of greenhouse gas concentrations in the atmosphere at levels that prevent dangerous consequences human intervention in the climate system. For the practical implementation of the convention in December 1997 in Kyoto (Japan) at an international conference, the Kyoto Protocol was adopted. It defines specific quotas for greenhouse gas emissions by member countries, including Russia, which ratified this Protocol in 2005.

At the time of this writing, one of the last conferences devoted to climate change, is the Climate Conference in Paris, held from November 30 to December 12, 2015. The purpose of this conference is the signing of an international agreement to curb the increase in the average temperature of the planet by 2100 no higher than 2 ° С.

So, as a result of the interaction of various flows of short-wave and long-wave radiation, the earth's surface continuously receives and loses heat. The resulting value of the incoming and outgoing radiation is radiation balance (AT), which determines the thermal state of the earth's surface and the surface layer of air, namely their heating or cooling:

AT = Q- «k - ?ef \u003d 60 - BUT)-? ef =

= (5 "sin / ^ > + D) (l-A) -E ^ f \u003d B to + B a. (

Data on the radiation balance are necessary to assess the degree of heating and cooling of various surfaces both in natural conditions and in the architectural environment, to calculate thermal regime buildings and structures, determination of evaporation, heat reserves in the soil, regulation of irrigation of agricultural fields and other national economic purposes.

Measurement methods. The key importance of studies of the Earth's radiation balance for understanding the patterns of climate and the formation of microclimatic conditions determines the fundamental role of observational data on its components - actinometric observations.

At meteorological stations in Russia, thermoelectric method measurements of radiation fluxes. The measured radiation is absorbed by the black receiving surface of the devices, turns into heat and heats the active junctions of the thermopile, while passive junctions are not heated by radiation and have more low temperature. Due to the difference in temperatures of active and passive junctions, a thermoelectromotive force arises at the output of the thermopile, which is proportional to the intensity of the measured radiation. Thus, most actinometric instruments are relative- they do not measure the radiation fluxes themselves, but quantities proportional to them - current strength or voltage. To do this, devices are connected, for example, to digital multimeters, and earlier to pointer galvanometers. At the same time, in the passport of each device, the so-called "conversion factor" - division price of an electrical measuring instrument (W / m 2). This multiplier is calculated by comparing the readings of one or another relative instrument with the readings absolute appliances - pyrheliometers.

The principle of operation of absolute devices is different. So, in the Angstrom compensation pyrheliometer, the blackened metal plate exposed to the sun, while another similar plate remains in the shade. A temperature difference arises between them, which is transferred to the junctions of the thermoelement attached to the plates, and thus a thermoelectric current is excited. In this case, current from the battery is passed through the shaded plate until it heats up to the same temperature as the plate in the sun, after which the thermoelectric current disappears. By the strength of the passed "compensating" current, you can determine the amount of heat received by the blackened plate, which, in turn, will be equal to the amount of heat received from the Sun by the first plate. Thus, it is possible to determine the amount of solar radiation.

At the meteorological stations of Russia (and earlier - the USSR), conducting observations of the components of the radiation balance, the homogeneity of the series of actinometric data is ensured by the use of the same type of instruments and their careful calibration, as well as the same measurement and data processing methods. As receivers of integral solar radiation (

In the Savinov-Yanishevsky thermoelectric actinometer, appearance which is shown in Fig. 1.6, the receiving part is a thin metal blackened disk of silver foil, to which the odd (active) junctions of the thermopile are glued through the insulation. During measurements, this disk absorbs solar radiation, as a result of which the temperature of the disk and active junctions rises. The even (passive) junctions are glued through the insulation to the copper ring in the device case and have a temperature close to the outside temperature. This temperature difference, when the external circuit of the thermopile is closed, creates a thermoelectric current, the strength of which is proportional to the intensity of solar radiation.

Rice. 1.6.

In a pyranometer (Fig. 1.7), the receiving part is most often a battery of thermoelements, for example, from manganin and constantan, with blackened and white junctions, which are heated differently under the action of incoming radiation. The receiving part of the device must have a horizontal position in order to perceive scattered radiation from the entire firmament. From direct radiation, the pyranometer is shaded by a screen, and from the oncoming radiation of the atmosphere it is protected by a glass cap. When measuring total radiation, the pyranometer is not shaded from direct rays.

Rice. 1.7.

A special device (folding plate) allows you to give the head of the pyranometer two positions: receiver up and receiver down. In the latter case, the pyranometer measures short-wave radiation reflected from the earth's surface. In route observations, the so-called camping albe-meter, which is a pyranometer head connected to a tilting gimbal suspension with a handle.

The thermoelectric balance meter consists of a body with a thermopile, two receiving plates and a handle (Fig. 1.8). The disc-shaped body (/) has a square cutout where the thermopile is fixed (2). Handle ( 3 ), soldered to the body, serves to install the balance meter on the rack.

Rice. 1.8.

One blackened receiving plate of the balance meter is directed upwards, the other downwards, towards the earth's surface. The principle of operation of an unshaded balance meter is based on the fact that all types of radiation coming to the active surface (Y, /) and E a), are absorbed by the blackened receiving surface of the device, facing upwards, and all types of radiation leaving the active surface (/? k, /? l and E 3), absorbed by the downward facing plate. Each receiving plate itself also emits long-wave radiation, in addition, there is heat exchange with the surrounding air and the body of the device. However, due to the high thermal conductivity of the body, a large heat transfer occurs, which does not allow the formation of a significant temperature difference between the receiving plates. For this reason, the self-radiation of both plates can be neglected, and the difference in their heating can be used to determine the value of the radiation balance of any surface in the plane of which the balance meter is located.

Since the receiving surfaces of the balance meter are not covered with a glass dome (otherwise it would be impossible to measure long-wave radiation), the readings of this device depend on the wind speed, which reduces the temperature difference between the receiving surfaces. For this reason, the readings of the balance meter lead to calm conditions, having previously measured the wind speed at the level of the device.

For automatic registration measurements, the thermoelectric current arising in the devices described above is fed to a self-recording electronic potentiometer. Changes in current strength are recorded on a moving paper tape, while the actinometer must automatically rotate so that its receiving part follows the Sun, and the pyranometer must always be shaded from direct radiation by a special ring protection.

Actinometric observations, in contrast to the main meteorological observations, are carried out six times a day at the following times: 00:30, 06:30, 09:30, 12:30, 15:30 and 18:30. Since the intensity of all types of short-wave radiation depends on the height of the Sun above the horizon, the timing of observations is set according to mean solar time stations.

characteristic values. The values ​​of direct and total radiation fluxes play one of the critical roles in architectural and climatic analysis. It is with their consideration that the orientation of buildings on the sides of the horizon, their space-planning and coloristic solution, internal layout, dimensions of light openings and a number of other architectural features are connected. Therefore, the daily and annual variation of characteristic values ​​will be considered for these solar radiation values.

Energy illumination direct solar radiation in a cloudless sky depends on the height of the sun, the properties of the atmosphere in the path of the sun's ray, characterized by transparency factor(a value showing what fraction of solar radiation reaches the earth's surface during a sheer incidence of sunlight) and the length of this path.

Direct solar radiation with a cloudless sky has a fairly simple daily variation with a maximum around noon (Fig. 1.9). As follows from the figure, during the day, the solar radiation flux first rapidly, then more slowly increases from sunrise to noon and slowly at first, then rapidly decreases from noon to sunset. Differences in clear-sky noon irradiance in January and July are primarily due to differences in the Sun's noon height, which is lower in winter than in summer. At the same time, in continental regions, an asymmetry of the diurnal variation is often observed, due to the difference in the transparency of the atmosphere in the morning and afternoon hours. The transparency of the atmosphere also affects the annual course of average monthly values ​​of direct solar radiation. The maximum radiation in a cloudless sky can shift by spring months, since in spring the dust content and moisture content of the atmosphere are lower than in autumn.

5 1 , kW/m 2

b", kW / m 2

Rice. 1.9.

and under average cloudiness conditions (b):

7 - on the surface perpendicular to the rays in July; 2 - on a horizontal surface in July; 3 - on a perpendicular surface in January; 4 - on a horizontal surface in January

Cloudiness reduces the arrival of solar radiation and can significantly change its daily course, which is manifested in the ratio of pre- and post-noon hourly sums. Thus, in most of the continental regions of Russia in the spring-summer months, the hourly amounts of direct radiation in the pre-noon hours are greater than in the afternoon (Fig. 1.9, b). This is mainly determined by the daily course of cloudiness, which begins to develop at 9-10 am and reaches a maximum in the afternoon, thus reducing radiation. The general decrease in the influx of direct solar radiation under actual cloudy conditions can be very significant. For example, in Vladivostok, with its monsoon climate, these losses in summer amount to 75%, and in St. Petersburg, even on average per year, clouds do not transmit 65% of direct radiation to the earth's surface, in Moscow - about half.

Distribution annual amounts direct solar radiation under average cloudiness over the territory of Russia is shown in fig. 1.10. To a large extent, this factor, which reduces the amount of solar radiation, depends on the circulation of the atmosphere, which leads to a violation of the latitudinal distribution of radiation.

As can be seen from the figure, on the whole, the annual amounts of direct radiation arriving on a horizontal surface increase from high to lower latitudes from 800 to almost 3000 MJ/m 2 . A large number of clouds in the European part of Russia leads to a decrease in annual totals compared to the regions of Eastern Siberia, where, mainly due to the influence of the Asian anticyclone, annual totals increase in winter. At the same time, the summer monsoon leads to a decrease in the annual radiation influx in coastal areas in the Far East. The range of changes in the midday intensity of direct solar radiation on the territory of Russia varies from 0.54-0.91 kW / m 2 in summer to 0.02-0.43 kW / m 2 in winter.

scattered radiation, arriving at a horizontal surface also changes during the day, increasing before noon and decreasing after it (Fig. 1.11).

As in the case of direct solar radiation, the arrival of diffuse radiation is affected not only by the height of the sun and the length of the day, but also by the transparency of the atmosphere. However, a decrease in the latter leads to an increase in scattered radiation (in contrast to direct radiation). In addition, scattered radiation depends on cloudiness in a very wide range: under average cloudiness, its arrival is more than twice the values ​​observed in a clear sky. On some days, cloudiness increases this figure by 3-4 times. Thus, scattered radiation can significantly supplement the direct line, especially at a low position of the Sun.

Rice. 1.10. Direct solar radiation arriving on a horizontal surface under average cloudiness, MJ / m 2 per year (1 MJ / m 2 \u003d 0.278 kW h / m 2)

/), kW / m 2 0.3 g

• 0,2 -
• 0,1 -

4 6 8 10 12 14 16 18 20 22 hours

Rice. 1.11.

and under average cloudy conditions (b)

The value of scattered solar radiation in the tropics is from 50 to 75% of the direct; at 50-60° latitude it is close to a straight line, and at high latitudes it exceeds direct solar radiation for almost the entire year.

A very important factor influencing the flux of scattered radiation is albedo underlying surface. If the albedo is high enough, then the radiation reflected from the underlying surface, scattered by the atmosphere in the opposite direction, can cause a significant increase in the arrival of scattered radiation. The effect is most pronounced in the presence of snow cover, which has the highest reflectivity.

Total radiation in a cloudless sky (possible radiation) depends on the latitude of the place, the height of the sun, the optical properties of the atmosphere and the nature of the underlying surface. In conditions clear sky it has a simple daily course with a maximum at noon. The asymmetry of the diurnal variation, characteristic of direct radiation, is little manifested in the total radiation, since the decrease in direct radiation due to an increase in atmospheric turbidity in the second half of the day is compensated by an increase in scattered radiation due to the same factor. In the annual course, the maximum intensity of total radiation with a cloudless sky over most of the territory

The territory of Russia is observed in June due to the maximum midday height of the sun. However, in some regions this influence is overlapped by the influence of atmospheric transparency, and the maximum is shifted to May (for example, in Transbaikalia, Primorye, Sakhalin, and in a number of regions of Eastern Siberia). The distribution of monthly and annual total solar radiation in a cloudless sky is given in Table. 1.9 and in fig. 1.12 as latitude-averaged values.

From the above table and figure, it can be seen that in all seasons of the year, both the intensity and the amount of radiation increase from north to south in accordance with the change in the height of the sun. The exception is the period from May to July, when the combination of a long day and the height of the sun provides rather high values ​​of total radiation in the north and, in general, on the territory of Russia, the radiation field is blurred, i.e. has no pronounced gradients.

Table 1.9

Total solar radiation on a horizontal surface

with a cloudless sky (kW h / m 2)

	Geographic latitude, ° N
September

Rice. 1.12. Total solar radiation to a horizontal surface with a cloudless sky at different latitudes (1 MJ / m 2 \u003d 0.278 kWh / m 2)

In the presence of clouds total solar radiation is determined not only by the number and shape of clouds, but also by the state of the solar disk. When the solar disk is translucent through the clouds, the total radiation compared to cloudless conditions can even increase due to the growth of scattered radiation.

For medium cloudy conditions, a completely regular daily course of total radiation is observed: a gradual increase from sunrise to noon and a decrease from noon to sunset. At the same time, the daily course of cloudiness violates the symmetry of the course relative to noon, which is characteristic of a cloudless sky. Thus, in most regions of Russia during the warm period, the pre-noon values ​​of total radiation are 3-8% higher than the afternoon values, with the exception of the monsoon regions of the Far East, where the ratio is reversed. In the annual course of the average multi-year monthly sums of total radiation, along with the determining astronomical factor, a circulation factor is manifested (through the influence of cloudiness), so the maximum can shift from June to July and even to May (Fig. 1.13).

• 600 -
• 500 -
• 400 -
• 300 -
• 200 -

m. Chelyuskin

Salekhard

Arkhangelsk

St. Petersburg

Petropavlovsk

Kamchatsky

Khabarovsk

Astrakhan

Rice. 1.13. Total solar radiation on a horizontal surface in individual cities of Russia under real cloudiness conditions (1 MJ / m 2 \u003d 0.278 kWh / m 2)

5", MJ/m 2 700

So, the real monthly and annual arrival of the total radiation is only a part of the possible. The largest deviations of real amounts from those possible in summer are noted in the Far East, where cloudiness reduces the total radiation by 40-60%. In general, the total annual income of total radiation varies across the territory of Russia in the latitudinal direction, increasing from 2800 MJ/m 2 on the coasts of the northern seas to 4800-5000 MJ/m 2 in southern regions Russia - the North Caucasus, the Lower Volga region, Transbaikalia and Primorsky Krai (Fig. 1.14).

Rice. 1.14. Total radiation entering a horizontal surface, MJ / m 2 per year

In summer, the differences in total solar radiation under real cloudiness conditions between cities located at different latitudes are not as “dramatic” as it might seem at first glance. For the European part of Russia from Astrakhan to Cape Chelyuskin, these values ​​lie in the range of 550-650 MJ/m 2 . In winter, in most cities, with the exception of the Arctic, where polar night, the total radiation is 50-150 MJ / m 2 per month.

For comparison: the average heat values ​​for January for 1 urban area (calculated according to actual data for Moscow) range from 220 MJ/m2 per month in urban urban development hubs to 120-150 MJ/m2 in inter-main areas with low-density residential development. On the territories of industrial and communal storage zones, the heat index in January is 140 MJ/m 2 . The total solar radiation in Moscow in January is 62 MJ/m 2 . Thus, in winter time due to the use of solar radiation, it is possible to cover no more than 10-15% (taking into account the efficiency of solar panels 40%) of the estimated calorific value of the building medium density even in Irkutsk and Yakutsk, famous for their sunny winter weather, even if their territory is completely covered with photovoltaic panels.

In summer, total solar radiation increases by 6-9 times, and heat consumption is reduced by 5-7 times compared to winter. Heat values ​​in July decrease to 35 MJ/m 2 or less in residential areas and 15 MJ/m 2 or less in industrial areas, i.e. up to values ​​constituting no more than 3-5% of the total solar radiation. Therefore, in the summer, when the demand for heating and lighting is minimal, there is an excess of this renewable natural resource throughout Russia that cannot be utilized, which once again casts doubt on the feasibility of using photovoltaic panels, at least in cities and apartment buildings.

Electricity consumption (without heating and hot water supply), also associated with the uneven distribution of the total building area, population density and the functional purpose of various territories, is in the

Warmth - an average indicator of the consumption of all types of energy (electricity, heating, hot water supply) per 1 m 2 of the building area.

cases from 37 MJ / m 2 per month (calculated as 1/12 of the annual amount) in densely built-up areas and up to 10-15 MJ / m 2 per month in areas with low building density. During the daytime and in summer, electricity consumption naturally falls. Electricity consumption density in July in most areas of residential and mixed development is 8-12 MJ/m 2 with total solar radiation under real cloudy conditions in Moscow about 600 MJ/m 2 . Thus, to cover the needs in the power supply of urban areas (for example, Moscow), it is required to utilize only about 1.5-2% of solar radiation. The rest of the radiation, if disposed of, will be redundant. At the same time, the issue of accumulation and preservation of daytime solar radiation for lighting in the evening and at night, when the loads on the power supply systems are maximum, and the sun almost or does not shine, remains to be resolved. This will require the transmission of electricity over long distances between areas where the Sun is still high enough, and those where the Sun has already set below the horizon. At the same time, electricity losses in the networks will be comparable to its savings through the use of photovoltaic panels. Or it will require the use of high-capacity batteries, the production, installation and subsequent disposal of which will require energy costs that are unlikely to be covered by the energy savings accumulated over the entire period of their operation.

Another, no less important factor that makes doubtful the feasibility of switching to solar panels as alternative source power supply on a city scale is that, ultimately, the operation of photocells will lead to a significant increase in solar radiation absorbed in the city, and consequently, to an increase in air temperature in the city in summer time. Thus, simultaneously with cooling due to photopanels and air conditioners powered by them, the internal environment will general increase temperature in the city, which will ultimately negate all the economic and environmental benefits of saving electricity through the use of still very expensive photovoltaic panels.

It follows that the installation of equipment for converting solar radiation into electricity justifies itself in a very limited list of cases: only in summer, only in climatic regions with dry, hot, cloudy weather, only in small towns or individual cottage settlements and only if this electricity is used for the operation of air conditioning and ventilation installations for the internal environment of buildings. In other cases - other areas, other urban conditions and at other times of the year - the use of photovoltaic panels and solar collectors for the needs of electricity and heat supply of ordinary buildings in medium and large cities located in a temperate climate is inefficient.

Bioclimatic significance of solar radiation. The decisive role of the impact of solar radiation on living organisms is reduced to participation in the formation of their radiation and heat balances due to thermal energy in the visible and infrared parts of the solar spectrum.

Visible rays are of particular importance to organisms. Most animals, like humans, are good at distinguishing the spectral composition of light, and some insects can even see in the ultraviolet range. The presence of light vision and light orientation is an important survival factor. For example, in humans, the presence of color vision is one of the most psycho-emotional and optimizing factors of life. Staying in the dark has the opposite effect.

As you know, green plants synthesize organic matter and, consequently, produce food for all other organisms, including humans. This most important process for life occurs during the assimilation of solar radiation, and plants use a certain range of the spectrum in the wavelength range of 0.38-0.71 microns. This radiation is called photosynthetically active radiation(PAR) and is very important for plant productivity.

The visible part of the light creates natural light. In relation to it, all plants are divided into light-loving and shade-tolerant. Insufficient illumination causes weakness of the stem, weakens the formation of ears and cobs on plants, reduces the sugar content and the amount of oils in cultivated plants, and makes it difficult for them to use mineral nutrition and fertilizers.

Biological action infrared rays consists in the thermal effect when they are absorbed by the tissues of plants and animals. At the same time, it changes kinetic energy molecules, there is an acceleration of electrical and chemical processes. Due to infrared radiation, the lack of heat (especially in high-mountainous regions and at high latitudes) received by plants and animals from the surrounding space is compensated.

Ultraviolet radiation on biological properties and the impact on humans is usually divided into three areas: area A - with wavelengths from 0.32 to 0.39 microns; region B, from 0.28 to 0.32 μm; and region C, from 0.01 to 0.28 μm. Area A is characterized by a relatively weakly expressed biological effect. It causes only the fluorescence of a number of organic substances, in humans it contributes to the formation of pigment in the skin and mild erythema (reddening of the skin).

The rays of area B are much more active. Diverse reactions of organisms to ultraviolet radiation, changes in the skin, blood, etc. mostly due to them. A well-known vitamin-forming effect of ultraviolet light is that the ergosterone of nutrients is converted into vitamin O, which has a strong stimulating effect on growth and metabolism.

Rays of region C have the most powerful biological effect on living cells. The bactericidal effect of sunlight is mainly due to them. In small doses ultra-violet rays necessary for plants, animals and humans, especially children. However, in in large numbers the rays of region C are destructive to all living things, and life on Earth is possible only because this short-wave radiation is almost completely blocked by the ozone layer of the atmosphere. The solution of the issue of the impact of excessive doses of ultraviolet radiation on the biosphere and humans has become especially relevant in recent decades due to the depletion of the ozone layer in the Earth's atmosphere.

The effect of ultraviolet radiation (UVR), which reaches the earth's surface, on a living organism is very diverse. As mentioned above, in moderate doses, it has a beneficial effect: it increases vitality, enhances the body's resistance to infectious diseases. The lack of UVR leads to pathological phenomena, which are called UV deficiency or UV starvation and manifest themselves in a lack of vitamin E, which leads to a violation of phosphorus-calcium metabolism in the body.

Excess UVR can lead to very serious consequences: the formation of skin cancer, the development of other oncological formations, the appearance of photokeratitis (“snow blindness”), photoconjunctivitis and even cataracts; violation of the immune system of living organisms, as well as mutagenic processes in plants; change in the properties and destruction of polymeric materials widely used in construction and architecture. For example, UVR can discolor facade paints or lead to mechanical destruction of polymeric finishing and structural building products.

Architectural and construction significance of solar radiation. Solar energy data is used in the calculation of the heat balance of buildings and heating and air conditioning systems, in the analysis of aging processes various materials, taking into account the effect of radiation on the thermal state of a person, choosing the optimal species composition of green spaces for planting greenery in a particular area, and many other purposes. Solar radiation determines the mode of natural illumination of the earth's surface, the knowledge of which is necessary when planning the consumption of electricity, designing various structures and organizing the operation of transport. Thus, the radiation regime is one of the leading urban planning and architectural and construction factors.

Building insolation is one of the essential conditions hygiene of the building, therefore, the irradiation of surfaces with direct sunlight is given special attention as an important environmental factor. At the same time, the Sun not only has a hygienic effect on the internal environment, killing pathogens, but also psychologically affects a person. The effect of such irradiation depends on the duration of the process of exposure to sunlight, so insolation is measured in hours, and its duration is normalized by the relevant documents of the Ministry of Health of Russia.

Required minimum solar radiation, providing comfortable conditions the internal environment of buildings, conditions for work and rest of a person, consists of the required illumination of living and working premises, the amount of ultraviolet radiation required for the human body, the amount of heat absorbed by external fences and transferred into buildings, providing thermal comfort of the internal environment. Based on these requirements, architectural and planning decisions are made, the orientation of living rooms, kitchens, utility and work rooms is determined. With an excess of solar radiation, the installation of loggias, blinds, shutters and other sun protection devices is provided.

It is recommended to analyze the sums of solar radiation (direct and diffuse) arriving at variously oriented surfaces (vertical and horizontal) according to the following scale:

• less than 50 kW h / m 2 per month - insignificant radiation;
• 50-100 kW h / m 2 per month - average radiation;
• 100-200 kW h / m 2 per month - high radiation;
• more than 200 kW h / m 2 per month - excess radiation.

With insignificant radiation, which is observed in temperate latitudes mainly in the winter months, its contribution to the heat balance of buildings is so small that it can be neglected. With average radiation in temperate latitudes, there is a transition to the region of negative values ​​of the radiation balance of the earth's surface and buildings, structures, artificial coatings, etc. located on it. In this regard, they begin to lose more thermal energy in the daily course than they receive heat from the sun during the day. These losses in the heat balance of buildings are not covered by internal heat sources (electrical appliances, hot water pipes, metabolic heat release of people, etc.), and they must be compensated for by the operation of heating systems - the heating period begins.

At high radiation and under real cloudy conditions, the thermal background of the urban area and the internal environment of buildings is in the comfort zone without the use of artificial systems heating and cooling.

With excess radiation in cities of temperate latitudes, especially those located in a temperate continental and sharply continental climate, overheating of buildings, their internal and external environments can be observed in summer. In this regard, architects are faced with the task of protecting the architectural environment from excessive insolation. They apply appropriate space-planning solutions, choose the optimal orientation of buildings on the sides of the horizon, architectural sun-protection elements of facades and light openings. If architectural means to protect against overheating are not enough, then there is a need for artificial conditioning of the internal environment of buildings.

The radiation regime also affects the choice of orientation and dimensions of light apertures. At low radiation, the size of the light openings can be increased to any size, provided that heat losses through external fences are maintained at a level not exceeding the standard. In case of excessive radiation, light openings are made minimal in size, meeting the requirements for insolation and natural illumination of the premises.

The lightness of the facades, which determines their reflectivity (albedo), is also selected based on the requirements of sun protection or, conversely, taking into account the possibility of maximum absorption of solar radiation in areas with a cool and cold humid climate and with an average or low level of solar radiation in the summer months. To select facing materials based on their reflectivity, it is necessary to know how much solar radiation enters the walls of buildings of various orientations and what is the ability of various materials to absorb this radiation. Since the arrival of radiation to the wall depends on the latitude of the place and how the wall is oriented in relation to the sides of the horizon, the heating of the wall and the temperature inside the rooms adjacent to it will depend on this.

The absorbing capacity of various facade finishing materials depends on their color and condition (Table 1.10). If the monthly sums of solar radiation entering the walls of various orientations 1 and the albedo of these walls are known, then the amount of heat absorbed by them can be determined.

Table 1.10

absorbency building materials

Data on the amount of incoming solar radiation (direct and diffuse) in a cloudless sky on vertical surfaces of various orientations are given in the Joint Venture "Construction Climatology".

Material name and processing	Characteristic surfaces	surfaces	Absorbed radiation,%
Concrete	Rough
		light blue
		Dark grey
		Bluish
	Hewn
		Yellowish brown
	polished
	Clean hewn	light gray
	Hewn
Roof
Ruberoid		brown
Galvanized steel		light gray
Roof tiles

Choosing the appropriate materials and colors for building envelopes, i.e. by changing the albedo of the walls, it is possible to change the amount of radiation absorbed by the wall and, thus, to reduce or increase the heating of the walls by solar heat. This technique is actively used in traditional architecture. various countries. Everyone knows that southern cities differ in the general light (white with colored decor) color of most residential buildings, while, for example, Scandinavian cities are mainly cities built of dark brick or using dark-colored tesa for sheathing buildings.

It is calculated that 100 kWh/m 2 of absorbed radiation raises the temperature of the outer surface by about 4°C. The walls of buildings in most regions of Russia receive such an amount of radiation per hour on average if they are oriented to the south and east, as well as western, southwestern and southeastern ones if they are made of dark brick and not plastered or have dark-colored plaster.

To move from the average wall temperature for a month without taking into account radiation to the most commonly used characteristic in thermal engineering calculations - the outdoor air temperature, an additional temperature additive is introduced At, depending on the monthly amount of solar radiation absorbed by the wall VK(Fig. 1.15). Thus, knowing the intensity of the total solar radiation coming to the wall and the albedo of the surface of this wall, it is possible to calculate its temperature by introducing an appropriate correction to the air temperature.

VK, kWh/m2

Rice. 1.15. Increase in the temperature of the outer surface of the wall due to the absorption of solar radiation

AT general case the temperature addition due to absorbed radiation is determined under otherwise equal conditions, i.e. at the same air temperature, humidity and thermal resistance of the building envelope, regardless of wind speed.

In clear weather at midday, the southern, before noon - southeastern and in the afternoon - southwestern walls can absorb up to 350-400 kWh / m 2 of solar heat and heat up so that their temperature can exceed 15-20 ° C outside air temperature. This creates large temperature con-

trusts between the walls of the same building. These contrasts in some areas turn out to be significant not only in summer, but also in the cold season with sunny low-wind weather, even at very low air temperatures. Metal structures are subjected to especially severe overheating. Thus, according to available observations, in Yakutia, located in a temperate sharply continental climate, characterized by cloudy weather in winter and summer, at midday hours with a clear sky, the aluminum parts of the enclosing structures and the roof of the Yakutskaya HPP heat up by 40-50 ° C above the air temperature, even at low values ​​of the latter.

Overheating of insolated walls due to the absorption of solar radiation must be provided for already at the stage of architectural design. This effect requires not only the protection of the walls from excessive insolation by architectural methods, but also the appropriate planning decisions buildings, the use of heating systems of various capacities for differently oriented facades, laying in the project of seams to relieve stress in structures and violation of the tightness of joints due to their temperature deformations, etc.

In table. 1.11 as an example, monthly sums of absorbed solar radiation in June are given for several geographical objects former USSR at given albedo values. This table shows that if the albedo of the northern wall of the building is 30%, and the southern one is 50%, then in Odessa, Tbilisi and Tashkent they will heat up to the same extent. If in northern regions reduce the albedo of the northern wall to 10%, then it will receive almost 1.5 times more heat than the wall with 30% albedo.

Table 1.11

Monthly sums of solar radiation absorbed by building walls in June at different values albedo (kW h / m 2)

The above examples, based on data on total (direct and diffuse) solar radiation contained in the Joint Venture "Construction Climatology" and climate reference books, do not take into account the solar radiation reflected from the earth's surface and surrounding objects (for example, existing buildings) arriving at various building walls. It depends less on their orientation, therefore, it is not given in the regulatory documents for construction. However, this reflected radiation can be quite intense and comparable in power to direct or diffuse radiation. Therefore, in architectural design, it must be taken into account, calculating for each specific case.

Answer from Caucasian[newbie]
Total radiation - part of the reflected and part of the direct radiation. Depends on clouds and cloud cover.

Answer from Arman Shaysultanov[newbie]
solar radiation value in saryarka

Answer from Vova Vasiliev[newbie]
Solar radiation - electromagnetic and corpuscular radiation of the Sun

Answer from Nasopharynx[active]
Solar radiation - electromagnetic and corpuscular radiation of the Sun. electromagnetic radiation propagates in the form of electromagnetic waves at the speed of light and penetrates into earth's atmosphere. Solar radiation reaches the earth's surface in the form of direct and diffuse radiation.
Solar radiation - main source energy for all physical and geographical processes occurring on the earth's surface and in the atmosphere. Solar radiation is usually measured by its thermal action and is expressed in calories per unit surface per unit of time. In total, the Earth receives from the Sun less than one two-billionth of its radiation.
Total solar radiation is measured in kilocalories per square centimeter.
When moving from north to south, the amount of solar radiation received by the territory increases.
Solar radiation is the radiation of light and heat from the Sun.

TASK-RES

How is the total amount of energy radiated by 1 m 2 of the surface in 1 sec determined. ANSWER How the total amount of energy emitted by 1 m 2 of the surface in 1 sec is determined E (T) \u003d aT 4

where a \u003d 5.67 10 -8 W / (m 2 K 4), T- the absolute temperature of a completely black body on the Kelvin scale. This pattern is called by the Stefan-Boltzmann radiation law. It was established in the last century on the basis of numerous experimental observations and Stefan, theoretically substantiated by L. Boltzmann, based on the classical laws of thermodynamics and electrodynamics of equilibrium radiation, and later, at the beginning of our century, it was found that this regularity follows from the quantum law of energy distribution in spectrum of equilibrium radiation, derived by M. Planck.

Calculation method for determining the wavelength λ m , which accounts for the maximum radiation energy of a blackbodyAccording to Wien's displacement law, the wavelength λm, which accounts for the maximum radiation energy of a blackbody, is inversely proportional to the absolute temperature T:

The law of distribution of the spectral power of the radiation of a completely black body was established by Planck, it is called therefore Planck's law of radiation. This law establishes that the radiation power in a unit wavelength interval is determined by the temperature T absolutely black body: Moreover, The derivation of this formula, in addition to the assumption of thermodynamic equilibrium of radiation, is based on its quantum nature, i.e., the radiation energy is summed from the energy of individual photons with the energy E h \u003d hv. Note that it represents the total energy radiated by a unit of the surface of a completely black body into a solid angle of 2π in 1 sec, over the entire frequency range, and it coincides with the Stefan-Boltzmann law

The calculation method for determining the optical mass of direct sunlight through the atmosphere The distance traveled by direct sunlight through the atmosphere depends on the angle of incidence (zenith angle) and the height of the observer above sea level. We assume the presence of a clear sky without clouds, dust or air pollution. Since the upper boundary of the atmosphere is not exactly defined, more important than the distance traveled is the interaction of radiation with atmospheric gases and vapors. A direct stream that normally passes through the atmosphere at normal pressure interacts with a certain mass of air. Increasing the length of the path with an oblique incidence of the beam.

A direct stream, normally passing through the atmosphere at normal pressure, interacts with a certain mass of air. Increasing the length of the path with an oblique incidence of the beam.

optical mass m = secθz:1-length of run, increased by a factor t; 2-normal-incidence At an angle θ z , compared to the normal-incidence path, is called optical mass and is denoted by the symbol t. From the figure, without taking into account the curvature of the earth's surface, we obtain m=secθz .

Calculation method for determining the intensity of cosmic solar radiation (solar constant) S o received from the Sun Earth radius R, and the intensity of cosmic solar radiation (solar constant) S o, then the energy received from the Sun is π R2 (1 - ρ 0)So. This energy is equal to the energy emitted in space Earth with emissivity ε = 1 and average temperature T e, Hence .

The spectral distribution of long-wavelength radiation of the Earth's surface, observed from space, approximately corresponds to the spectral distribution of a black body at a temperature of 250 K. Atmospheric radiation propagates both to the Earth's surface and in opposite direction. The effective temperature of the Earth's black body as a radiator is equivalent to the temperature at which the outer layers of the atmosphere radiate, and not the Earth's surface.

Calculation method for determining the flux and density of the radiant energy of the sun In meteorology, radiant energy fluxes are subdivided into short-wave radiation with wavelengths from 0.2 to 5.0 µm and long-wave radiation with wavelengths from 5.0 to 100 µm. Streams of short-wave solar radiation are divided into:- straight;

- scattered (diffuse); - total. Solar energy W- called the energy carried by electromagnetic waves. The unit of radiation energy W in the international system of units SI is 1 joule. radiant streamФ e - which is determined by the formula: F e \u003d W / t,

where W- radiation energy over time t.

Assuming W=1 j, t=1 s, we get: 1 SI (F e) \u003d 1 J / 1 sec \u003d 1 W. Radiant flux density radiation ( radiation flux I) which is defined by the formula: where F e is the radiation flux uniformly incident on the surface S.

Assuming F e \u003d 1 W, S \u003d 1 m 2, we find: 1 SI (E e) \u003d 1 W / 1 m 2 \u003d 1 W / m 2.

Calculation formula direct and total solar radiation

Direct solar radiation-I p represents the flux of radiation coming from the solar disk and measured in a plane perpendicular to the sun's rays. Direct radiation coming to a horizontal surface (S ") is calculated by the formula:

S" \u003d I p sin h, where h is the height of the sun above the horizon. Savinov-Yanishevsky actinometer is used to measure direct solar radiation. Scattered solar radiation (D) - called the radiation arriving on a horizontal surface from all points of the firmament, with the exception of the disk of the Sun and the near-solar zone with a radius of 5 0, as a result of the scattering of solar radiation by molecules atmospheric gases, water drops or ice crystal clouds and solid particles suspended in the atmosphere. Total solar radiation Q- includes radiation incident on a horizontal plane, of two types: direct and diffuse. Q=S"+D(4.7) The total radiation that has reached the earth's surface is mostly absorbed in the upper, thin layer of soil or water and passes into heat, and is partially reflected.

Determine the main points of the celestial sphere Celestial sphere is an imaginary sphere of arbitrary radius. Its center, depending on the problem being solved, is combined with one or another point in space. The plumb line intersects the surface of the celestial sphere at two points: at the top Z - zenith - and at the bottom Z "- nadir Basic points and circles on the celestial sphere

Determine the Celestial Coordinates of the SunBasic the circles relative to which the place of the Sun (luminaries) is determined are the true horizon and the celestial meridian coordinates are Sun height (h) and its azimuth (A) .The apparent position of the Sun at any point on the Earth is determined by these two angles Horizontal coordinate system Height h of the Sun above the horizon – the angle between the direction to the Sun from the point of observation and the horizontal plane passing through this point. Azimuth A of the Sun - the angle between the meridian plane and the vertical plane drawn through the observation point and the Sun. Zenith angleZ - the angle between the direction to the zenith (Z) and the direction to the Sun. This angle is complementary to the height of the solstice. h + z = 90. When the earth is facing the sun south side, the azimuth is zero, and the height is maximum. From this comes the concept noon, which is taken as the beginning of the countdown time of the day (or the second half of the day).

Calculation technique for determining angular solar time (hour angle of the Sun) Angular solar time (hour angle of the Sun) τ - represents the angular displacement of the Sun from noon (1 h corresponds to π/12 glad, or 15° angular displacement). The displacement to the East from the South (i.e., the morning value) is considered positive. The hourly angle of the Sun τ varies between the planes of the local meridian and the solar meridian. Once every 24 hours, the Sun enters the meridional plane. Due to daily rotation Earth hour angle τ changes during the day from 0 to 360 o or 2π rad (radian), in 24 hours, thus, the Earth, moving along the Orbit, rotates around its axis with an angular velocity If we take solar time from true noon, corresponding to the moment of passage of the Sun through the planes of the local meridian, then we can write: , hail or glad

Calculation Method for Determining the Declination of the Sun declination sun - the angle between the direction to the Sun and the equatorial plane is called declination δ and is a measure of seasonal variation. Declination is usually expressed in radians (or degrees) north or south of the equator. Measured from 0° to 90° (positive north of the equator, negative south). The earth revolves around the sun in a year. Direction earth's axis remains fixed in space at an angle δ 0 \u003d 23.5 ° to the normal to the plane rotation, North hemisphere δ changes smoothly from δ 0 = + 23.5 ° during the summer solstice to δ 0 = -23.5 ° during the winter solstice. Analytically obtained hail

where P- day of the year ( n= 1 corresponds to January 1). At the equinoxes δ = 0 , and the points of sunrise and sunset are located strictly on the line of the E-W horizon. Thus, the trajectory of the Sun along the celestial sphere is not a closed curve, but is a kind of spherical spiral, stuffing side surface spheres within the band - .

During the summer half-year from March 21 to September 23, the Sun is above the equatorial plane in the northern celestial hemisphere. During the winter half-year from September 23 to March 21, the Sun is below the equatorial plane in the southern celestial hemisphere.

The most important source from which the surface of the Earth and the atmosphere receive thermal energy is the Sun. It sends a colossal amount of radiant energy into the world space: thermal, light, ultraviolet. Electromagnetic waves emitted by the Sun propagate at a speed of 300,000 km/s.

The heating of the earth's surface depends on the angle of incidence of the sun's rays. All the sun's rays hit the Earth's surface parallel to each other, but since the Earth has a spherical shape, the sun's rays fall on different parts of its surface at different angles. When the Sun is at its zenith, its rays fall vertically and the Earth heats up more.

The totality of radiant energy sent by the Sun is called solar radiation, it is usually expressed in calories per surface area per year.

Solar radiation determines the temperature regime of the Earth's air troposphere.

It should be noted that the total amount of solar radiation is more than two billion times the amount of energy received by the Earth.

Radiation reaching the earth's surface consists of direct and diffuse.

Radiation that comes to Earth directly from the Sun in the form of direct sunlight in a cloudless sky is called straight. It carries the greatest amount of heat and light. If our planet had no atmosphere, the earth's surface would receive only direct radiation.

However, passing through the atmosphere, about a quarter of the solar radiation is scattered by gas molecules and impurities, deviates from the direct path. Some of them reach the Earth's surface, forming scattered solar radiation. Thanks to scattered radiation, light also penetrates into places where direct sunlight (direct radiation) does not penetrate. This radiation creates daylight and gives color to the sky.

Total solar radiation

All the rays of the sun that hit the earth are total solar radiation i.e., the totality of direct and diffuse radiation (Fig. 1).

Rice. 1. Total solar radiation per year

Distribution of solar radiation over the earth's surface

Solar radiation is distributed unevenly over the earth. It depends:

1. on the density and humidity of the air - the higher they are, the less radiation the earth's surface receives;

2. from the geographical latitude of the area - the amount of radiation increases from the poles to the equator. The amount of direct solar radiation depends on the length of the path that the sun's rays travel through the atmosphere. When the Sun is at its zenith (the angle of incidence of the rays is 90 °), its rays hit the Earth in the shortest way and intensively give off their energy to a small area. On Earth, this occurs in the band between 23° N. sh. and 23°S sh., i.e. between the tropics. As you move away from this zone to the south or north, the length of the path of the sun's rays increases, i.e., the angle of their incidence on the earth's surface decreases. The rays begin to fall on the Earth at a smaller angle, as if gliding, approaching the tangent line in the region of the poles. As a result, the same energy flow is distributed over a larger area, so the amount of reflected energy increases. Thus, in the region of the equator, where the sun's rays fall on the earth's surface at an angle of 90 °, the amount of direct solar radiation received by the earth's surface is higher, and as you move towards the poles, this amount is sharply reduced. In addition, the length of the day at different times of the year also depends on the latitude of the area, which also determines the amount of solar radiation entering the earth's surface;

3. from the annual and daily movement of the Earth - in the middle and high latitudes, the influx of solar radiation varies greatly over the seasons, which is associated with a change midday height Sun and day length;

4. on the nature of the earth's surface - the brighter the surface, the more sunlight it reflects. The ability of a surface to reflect radiation is called albedo(from lat. whiteness). Snow reflects radiation especially strongly (90%), sand is weaker (35%), chernozem is even weaker (4%).

Earth's surface, absorbing solar radiation (absorbed radiation), heats up and radiates heat into the atmosphere (reflected radiation). The lower layers of the atmosphere largely delay terrestrial radiation. The radiation absorbed by the earth's surface is spent on heating the soil, air, and water.

That part of the total radiation that remains after reflection and thermal radiation earth's surface is called radiation balance. The radiation balance of the earth's surface varies during the day and seasons of the year, but on average for the year it has a positive value everywhere, with the exception of the icy deserts of Greenland and Antarctica. Radiation balance reaches its maximum values ​​at low latitudes (between 20°N and 20°S) - over 42*10 2 J/m 2 , at a latitude of about 60° in both hemispheres it decreases to 8*10 2 - 13 * 10 2 J / m 2.

The sun's rays give up to 20% of their energy to the atmosphere, which is distributed throughout the entire thickness of the air, and therefore the heating of the air caused by them is relatively small. The sun heats the earth's surface, which transfers heat atmospheric air at the expense convection(from lat. convection- delivery), that is, the vertical movement of air heated at the earth's surface, in place of which more than cold air. This is how the atmosphere receives most of its heat - on average, three times more than directly from the Sun.

The presence of carbon dioxide and water vapor does not allow the heat reflected from the earth's surface to freely escape into outer space. They create the greenhouse effect, due to which the temperature drop on Earth during the day does not exceed 15 ° C. In the absence of carbon dioxide in the atmosphere, the earth's surface would cool down by 40-50 °C overnight.

As a result of the growth in the scale of human economic activity - the burning of coal and oil at thermal power plants, emissions industrial enterprises, an increase in car emissions - the content of carbon dioxide in the atmosphere is increasing, which leads to an increase in the greenhouse effect and threatens global climate change.

The sun's rays, having passed through the atmosphere, fall on the surface of the Earth and heat it, and that, in turn, gives off heat to the atmosphere. This explains salient feature troposphere: decrease in air temperature with height. But there are times when the upper layers of the atmosphere are warmer than the lower ones. Such a phenomenon is called temperature inversion(from lat. inversio - turning over).