Let us consider, along with the atmosphere, the thermal regime of the Earth's active layer. The active layer is such a layer of soil or water, the temperature of which experiences daily and annual fluctuations. Observations show that on land, daily fluctuations propagate to a depth of 1 - 2 m, annual fluctuations - to a layer of several tens of meters. In the seas and oceans, the thickness of the active layer is ten times greater than on land. The connection between the thermal regimes of the atmosphere and the active layer of the Earth is carried out using the so-called heat balance equation of the earth's surface. This equation was first used in 1941 to construct the theory of the daily variation of air temperature by A.A. Dorodnitsyn. In subsequent years, the heat balance equation was widely used by many researchers to study various properties of the surface layer of the atmosphere, up to assessing the changes that will occur under the influence of active influences, for example, on the ice cover of the Arctic. Let us dwell on the derivation of the equation for the heat balance of the earth's surface. Solar radiation that has arrived at the earth's surface is absorbed on land in a thin layer, the thickness of which will be denoted by (Fig. 1). In addition to the flow of solar radiation, the earth's surface receives heat in the form of a flow of infrared radiation from the atmosphere, it loses heat through its own radiation.
Rice. one.
In the soil, each of these streams undergoes a change. If in an elementary layer with a thickness (- the depth counted from the surface into the depth of the soil) the flux Ф has changed by dФ, then we can write
where a is the absorption coefficient, is the density of the soil. Integrating the last relation in the range from to, we obtain
where is the depth at which the flow decreases by a factor of e compared with the flow Ф(0) at. Along with radiation, heat transfer is carried out by turbulent exchange of the soil surface with the atmosphere and molecular exchange with the underlying soil layers. Under the influence of turbulent exchange, the soil loses or receives an amount of heat equal to
In addition, water evaporates from the soil surface (or water vapor condenses), which consumes the amount of heat
The molecular flow through the lower boundary of the layer is written as
where is the coefficient of thermal conductivity of the soil, is its specific heat capacity, is the coefficient of molecular thermal diffusivity.
Under the influence of the influx of heat, the temperature of the soil changes, and at temperatures close to 0, ice melts (or water freezes). Based on the law of conservation of energy in a vertical column of soil, we can write down the thickness.
In equation (19), the first term on the left side is the amount of heat spent on changing the heat content cm 3 of the soil per unit time, the second amount of heat used to melt ice (). On the right side, all heat fluxes that enter the soil layer through the upper and lower boundaries are taken with the “+” sign, and those that leave the layer are taken with the “-” sign. Equation (19) is the heat balance equation for the soil layer thickness. In this general form, this equation is nothing more than the heat influx equation written for a layer of finite thickness. It is not possible to extract from it any additional information (compared to the heat influx equation) on the thermal regime of air and soil. However, several special cases of the heat balance equation can be indicated, when it can be used as a boundary condition independent of differential equations. In this case, the heat balance equation makes it possible to determine the unknown temperature of the earth's surface. The following are such special cases. On land that is not covered with snow or ice, the value, as already indicated, is quite small. At the same time, the ratio to each of the quantities that are of the order of the molecular range is quite large. As a result, the equation for land in the absence of ice melting processes can be written with a sufficient degree of accuracy in the form:
The sum of the first three terms in equation (20) is nothing but the radiation balance R of the earth's surface. Thus, the equation for the heat balance of the land surface takes the form:
The heat balance equation in the form (21) is used as a boundary condition in the study of the thermal regime of the atmosphere and soil.
HEAT BALANCE OF THE EARTH
the balance of the Earth, the ratio of the income and consumption of energy (radiant and thermal) on the earth's surface, in the atmosphere and in the Earth-atmosphere system. The main source of energy for the vast majority of physical, chemical, and biological processes in the atmosphere, hydrosphere, and upper layers of the lithosphere is solar radiation; therefore, the distribution and ratio of the components of T. b. characterize its transformations in these shells.
T. b. are private formulations of the law of conservation of energy and are compiled for a section of the Earth's surface (T. b. of the earth's surface); for a vertical column passing through the atmosphere (T. b. atmosphere); for the same column passing through the atmosphere and the upper layers of the lithosphere or the hydrosphere (T. b. the Earth-atmosphere system).
Equation T. b. earth's surface: R + P + F0 + LE 0 is the algebraic sum of energy flows between an element of the earth's surface and the surrounding space. These streams include the radiation balance (or residual radiation) R - the difference between the absorbed short-wave solar radiation and the long-wave effective radiation from the earth's surface. The positive or negative value of the radiation balance is compensated by several heat fluxes. Since the temperature of the earth's surface is usually not equal to the air temperature, a heat flux P arises between the underlying surface and the atmosphere. A similar heat flux F 0 is observed between the earth's surface and deeper layers of the lithosphere or hydrosphere. In this case, the heat flux in the soil is determined by molecular thermal conductivity, while in water bodies, heat transfer, as a rule, is more or less turbulent. The heat flux F 0 between the surface of the reservoir and its deeper layers is numerically equal to the change in the heat content of the reservoir over a given time interval and the heat transfer by currents in the reservoir. Essential value in T. b. the surface of the earth's surface usually has a heat consumption for evaporation LE, which is defined as the product of the mass of evaporated water E and the heat of evaporation L. The value of LE depends on the moistening of the earth's surface, its temperature, air humidity and the intensity of turbulent heat transfer in the surface air layer, which determines the rate of transfer of water steam from the earth's surface to the atmosphere.
Equation T. b. atmosphere has the form: Ra + Lr + P + Fa D W.
T. b. atmosphere is composed of its radiation balance R a ; heat input or output Lr during phase transformations of water in the atmosphere (r is the sum of precipitation); the arrival or consumption of heat P, due to the turbulent heat exchange of the atmosphere with the earth's surface; the arrival or loss of heat F a caused by heat exchange through the vertical walls of the column, which is associated with ordered atmospheric movements and macroturbulence. In addition, in the equation T. b. atmosphere includes a term DW, equal to the change in heat content inside the column.
Equation T. b. systems Earth - atmosphere corresponds to the algebraic sum of the terms of the equations T. b. earth's surface and atmosphere. Components of T. b. Earth's surface and atmosphere for various regions of the globe are determined by meteorological observations (at actinometric stations, at special stations in the sky, and on Earth's meteorological satellites) or by climatological calculations.
The average latitudinal values of the components of T. b. the earth's surface for the oceans, land and Earth, and T. b. atmospheres are given in tables 1, 2, where the values of the members of T. b. are considered positive if they correspond to the arrival of heat. Since these tables refer to average annual conditions, they do not include terms characterizing changes in the heat content of the atmosphere and the upper layers of the lithosphere, since for these conditions they are close to zero.
For the Earth as a planet, together with the atmosphere, the scheme of T. b. shown in fig. A solar radiation flux equal to an average of about 250 kcal/cm 2 per year per unit surface of the outer boundary of the atmosphere, of which about 167 kcal/cm 2 is absorbed by the Earth per year (arrow Q s in Fig.). The earth's surface reaches short-wave radiation, equal to 126 kcal / cm 2 per year; 18 kcal/cm 2 per year of this amount is reflected, and 108 kcal/cm 2 per year is absorbed by the earth's surface (arrow Q). The atmosphere absorbs 59 kcal / cm 2 per year of short-wave radiation, that is, much less than the earth's surface. The effective long-wave radiation of the Earth's surface is 36 kcal/cm 2 per year (arrow I), so the radiation balance of the earth's surface is 72 kcal/cm 2 per year. The long-wave radiation of the Earth into the world space is equal to 167 kcal/cm 2 per year (arrow Is). Thus, the Earth's surface receives about 72 kcal / cm 2 per year of radiant energy, which is partially spent on the evaporation of water (circle LE) and partially returned to the atmosphere through turbulent heat transfer (arrow P).
Tab. one . - Heat balance of the earth's surface, kcal / cm 2 year
Latitude, degrees
Earth average
70-60 north latitude
0-10 south latitude
Earth as a whole
Data on the components of T. b. are used in the development of many problems of climatology, land hydrology, and oceanology; they are used to substantiate numerical models of climate theory and to empirically test the results of applying these models. Materials about T. b. play an important role in the study of climate change, they are also used in calculations of evaporation from the surface of river basins, lakes, seas and oceans, in studies of the energy regime of sea currents, for the study of snow and ice covers, in plant physiology for the study of transpiration and photosynthesis, in physiology animals to study the thermal regime of living organisms. Data about T. b. were also used to study geographic zoning in the works of the Soviet geographer A. A. Grigoriev.
Tab. 2. - Heat balance of the atmosphere, kcal/cm2 year
Latitude, degrees
70-60 north latitude
0-10 south latitude
Earth as a whole
Lit.: Atlas of the heat balance of the globe, ed. M. I. Budyko. Moscow, 1963. Budyko M.I., Climate and life, L., 1971; Grigoriev A. A., Patterns of the structure and development of the geographical environment, M., 1966.
M. I. Budyko.
Great Soviet Encyclopedia, TSB. 2012
See also interpretations, synonyms, word meanings and what is EARTH HEAT BALANCE in Russian in dictionaries, encyclopedias and reference books:
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AGRICULTURAL PURPOSE - land provided for the needs of agriculture or intended for these ... - EARTH in the Dictionary of Economic Terms:
RECREATIONAL PURPOSE - lands allocated in accordance with the established procedure, intended and used for organized mass recreation and tourism of the population. To them … - EARTH in the Dictionary of Economic Terms:
ENVIRONMENTAL PURPOSE - lands of reserves (with the exception of hunting); prohibited and spawning zones; lands occupied by forests that perform protective functions; other … - EARTH in the Dictionary of Economic Terms:
NATURAL RESERVE FUND - lands of nature reserves, natural monuments, natural (national) and dendrological, botanical gardens. The composition of the Z.p.-z.f. includes land with... - EARTH in the Dictionary of Economic Terms:
DAMAGE - see DAMAGE TO THE EARTH ... - EARTH in the Dictionary of Economic Terms:
HEALTH PURPOSE - land plots with natural healing factors (mineral springs, deposits of therapeutic mud, climatic and other conditions), favorable ... - EARTH in the Dictionary of Economic Terms:
GENERAL USE - in cities, towns and rural settlements - lands used as means of communication (squares, streets, alleys, ... - EARTH in the Dictionary of Economic Terms:
LAND PRICE - see LAND REGULATION PRICE… - EARTH in the Dictionary of Economic Terms:
SETTLEMENTS - see URBAN LAND ... - EARTH in the Dictionary of Economic Terms:
MUNICIPALIZATION - see MUNICIPALIZATION OF THE LAND ... - EARTH in the Dictionary of Economic Terms:
FOREST FUND - lands covered with forest, as well as. not covered with forest, but provided for the needs of forestry and forestry ... - EARTH in the Dictionary of Economic Terms:
HISTORICAL AND CULTURAL PURPOSE - lands on which (and in which) historical and cultural monuments, places of interest are located, including those declared ... - EARTH in the Dictionary of Economic Terms:
RESERVE - all lands not provided for ownership, possession, use and lease. include lands, ownership, possessions… - EARTH in the Dictionary of Economic Terms:
RAILWAY TRANSPORT - federal lands provided free of charge for permanent (unlimited) use to enterprises and institutions of railway transport for the implementation of assigned ... - EARTH in the Dictionary of Economic Terms:
FOR THE NEEDS OF DEFENSE - lands provided for the placement and permanent activity of military units, institutions, military educational institutions, enterprises and organizations of the Armed ... - EARTH in the Dictionary of Economic Terms:
URBAN - see URBAN LAND ... - EARTH in the Dictionary of Economic Terms:
WATER FUND - lands occupied by reservoirs, glaciers, swamps, with the exception of the tundra and forest-tundra zones, hydraulic and other water management structures; but … - BALANCE in the Dictionary of Economic Terms:
LABOR RESOURCES - a balance of the availability and use of labor resources, compiled taking into account their replenishment and disposal, employment, productivity ... - BALANCE in the Dictionary of Economic Terms:
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CURRENT OPERATIONS - a balance showing the state's net exports, equal to the volume of exports of goods and services minus imports, with the addition of net ... - BALANCE in the Dictionary of Economic Terms:
CONSOLIDATED - see CONSOLIDATED BALANCE ... - BALANCE in the Dictionary of Economic Terms:
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ESTIMATED - see ESTIMATED ... - BALANCE in the Dictionary of Economic Terms:
SEPARATING - see SEPARATING BALANCE ... - BALANCE in the Dictionary of Economic Terms:
WORKING TIME - a balance that characterizes the resources of the working time of the employees of the enterprise and their use for different types of work. Presented as… - BALANCE in the Dictionary of Economic Terms:
PAYMENT CURRENT see CURRENT BALANCE ... - BALANCE in the Dictionary of Economic Terms:
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PAYMENTS FOR CLEARING SETTLEMENTS - the balance of non-cash settlements for payment obligations or mutual claims ... - BALANCE in the Dictionary of Economic Terms:
PASSIVE TRADING (PAYING) - see PASSIVE TRADING (PAYING) ... - BALANCE in the Dictionary of Economic Terms:
FIXED ASSETS - a balance sheet that compares cash fixed assets, taking into account their depreciation and disposal, and newly introduced funds ... - BALANCE in the Dictionary of Economic Terms:
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LIQUIDATION - see LIQUIDATION ... - BALANCE in the Dictionary of Economic Terms:
INCOME AND EXPENSES - a financial balance sheet, in sections of which the sources and amounts of income and expenses are indicated for a certain period ... - BALANCE in the Great Soviet Encyclopedia, TSB:
(French balance, literally - scales, from Latin bilanx - having two weight bowls), 1) balance, balancing. 2) A system of indicators that ... - EARTH
Old Russian regions formed near the old cities. Z., often for a very significant distance from the city, was the property of its inhabitants and always ... - BALANCE in the Encyclopedic Dictionary of Brockhaus and Euphron:
Accounting balance. In B.'s accounting, an equilibrium is established between debit and credit, and B.'s account is distinguished incoming, if commercial books are opened, and ... - BALANCE in the Encyclopedic Dictionary:
I a, pl. no, m. 1. The ratio of mutually related indicators of some activity, process. B. production and consumption. and the balance of trade...
Radiation balance is the difference between the inflow and outflow of radiant energy absorbed and emitted by the Earth's surface.
Radiation balance - the algebraic sum of radiation fluxes in a certain volume or on a certain surface. Speaking about the radiation balance of the atmosphere or the "Earth - atmosphere" system, most often they mean the radiation balance of the earth's surface, which determines heat transfer at the lower boundary of the atmosphere. It represents the difference between the absorbed total solar radiation and the effective radiation of the earth's surface.
The radiation balance is the difference between the incoming and outgoing radiant energy absorbed and emitted by the Earth's surface.
The radiation balance is the most important climatic factor, since the temperature distribution in the soil and the air layers adjacent to it largely depends on its value. It determines the physical properties of air masses moving across the Earth, as well as the intensity of evaporation and melting of snow.
The distribution of annual values of the radiation balance on the surface of the globe is not the same: in tropical latitudes, these values reach 100 ... 120 kcal / (cm2-year), and the maximum (up to 140 kcal / (cm2-year)) are observed off the northwestern coast of Australia ). In desert and arid regions, the values of the radiation balance are lower compared to areas of sufficient and excessive moisture at the same latitudes. This is caused by an increase in albedo and an increase in effective radiation due to the high dryness of the air and low cloudiness. In temperate latitudes, the values of the radiation balance rapidly decrease with increasing latitude due to a decrease in total radiation.
On average, over the year, the sums of the radiation balance for the entire surface of the globe turn out to be positive, with the exception of areas with a permanent ice cover (Antarctica, the central part of Greenland, etc.).
The energy, measured by the value of the radiation balance, is partly spent on evaporation, partly transferred to the air, and, finally, a certain amount of energy goes into the soil and goes to heat it. Thus, the total heat input-output for the Earth's surface, called the heat balance, can be represented as the following equation:
Here B is the radiation balance, M is the heat flux between the Earth's surface and the atmosphere, V is the heat consumption for evaporation (or heat release during condensation), T is the heat exchange between the soil surface and the deep layers.
Figure 16 - The impact of solar radiation on the Earth's surface
On average, over the year, the soil practically gives off as much heat to the air as it receives, therefore, in the annual conclusions, the heat turnover in the soil is zero. Heat consumption for evaporation is distributed on the surface of the globe very unevenly. On the oceans, they depend on the amount of solar energy reaching the surface of the ocean, as well as on the nature of ocean currents. Warm currents increase the consumption of heat for evaporation, while cold ones reduce it. On the continents, the cost of heat for evaporation is determined not only by the amount of solar radiation, but also by the reserves of moisture contained in the soil. With a lack of moisture, causing a reduction in evaporation, the heat costs for evaporation are reduced. Therefore, in deserts and semi-deserts, they are significantly reduced.
Practically the only source of energy for all physical processes developing in the atmosphere is solar radiation. The main feature of the radiation regime of the atmosphere is the so-called. greenhouse effect: the atmosphere weakly absorbs short-wave solar radiation (most of it reaches the earth's surface), but delays long-wave (entirely infrared) thermal radiation of the earth's surface, which significantly reduces the heat transfer of the Earth into outer space and increases its temperature.
The solar radiation entering the atmosphere is partially absorbed in the atmosphere mainly by water vapor, carbon dioxide, ozone and aerosols and is scattered by aerosol particles and atmospheric density fluctuations. Due to the scattering of the radiant energy of the Sun in the atmosphere, not only direct solar radiation is observed, but also scattered radiation, together they constitute the total radiation. Reaching the earth's surface, the total radiation is partially reflected from it. The amount of reflected radiation is determined by the reflectivity of the underlying surface, the so-called. albedo. Due to the absorbed radiation, the earth's surface heats up and becomes a source of its own long-wave radiation directed towards the atmosphere. In turn, the atmosphere also emits long-wave radiation directed towards the earth's surface (the so-called counter-radiation of the atmosphere) and outer space (the so-called outgoing radiation). Rational heat exchange between the earth's surface and the atmosphere is determined by effective radiation - the difference between the Earth's own surface radiation and the atmosphere's counter-radiation absorbed by it. The difference between the shortwave radiation absorbed by the earth's surface and the effective radiation is called the radiation balance.
Transformations of the energy of solar radiation after its absorption on the earth's surface and in the atmosphere constitute the heat balance of the Earth. The main source of heat for the atmosphere is the earth's surface, which absorbs the bulk of solar radiation. Since the absorption of solar radiation in the atmosphere is less than the loss of heat from the atmosphere to the world space by long-wave radiation, the radiative heat consumption is compensated by the influx of heat to the atmosphere from the earth's surface in the form of turbulent heat transfer and the arrival of heat as a result of condensation of water vapor in the atmosphere. Since the total amount of condensation in the entire atmosphere is equal to the amount of precipitation, as well as the amount of evaporation from the earth's surface, the influx of condensation heat in the atmosphere is numerically equal to the heat spent on evaporation on the Earth's surface.
The difference between absorbed solar radiation and effective radiation is the radiation balance, or residual radiation of the earth's surface (B). The radiation balance, averaged over the entire surface of the Earth, can be written as the formula B = Q * (1 - A) - E eff or B = Q - R k - E eff. Figure 24 shows the approximate percentage of different types of radiation involved in the radiation and heat balance. It is obvious that the surface of the Earth absorbs 47% of all the radiation that has arrived on the planet, and the effective radiation is 18%. Thus, the radiation balance, averaged over the surface of the entire Earth, is positive and amounts to 29%.
Rice. 24. Scheme of radiation and heat balances of the earth's surface (according to K. Ya. Kondratiev)
The distribution of the radiation balance over the earth's surface is highly complex. Knowledge of the patterns of this distribution is extremely important, since under the influence of residual radiation the temperature regime of the underlying surface and the troposphere and the Earth's climate as a whole are formed. Analysis of maps of the radiation balance of the earth's surface for the year (Fig. 25) leads to the following conclusions.
The annual sum of the radiation balance of the Earth's surface is almost everywhere positive, with the exception of the ice plateaus of Antarctica and Greenland. Its annual values zonally and regularly decrease from the equator to the poles in accordance with the main factor - total radiation. Moreover, the difference in the values of the radiation balance between the equator and the poles is more significant than the difference in the values of the total radiation. Therefore, the zonality of the radiation balance is very pronounced.
The next regularity of the radiation balance is its increase during the transition from land to the ocean with discontinuities and mixing of isolines along the coast. This feature is better expressed in the equatorial-tropical latitudes and gradually smoothes out to the polar ones. The greater radiation balance over the oceans is explained by the lower water albedo, especially in the equatorial-tropical latitudes, and the reduced effective radiation due to the lower temperature of the Ocean surface and the significant moisture content of the air and cloudiness. Due to the increased values of the radiation balance and the large area of the Ocean on the planet (71%), it is he who plays the leading role in the thermal regime of the Earth, and the difference in the radiation balance of the oceans and continents determines their constant and deep mutual influence on each other at all latitudes.
Rice. 25. Radiation balance of the earth's surface for the year [MJ / (m 2 X year)] (according to S. P. Khromov and M. A. Petrosyants)
Seasonal changes in the radiation balance in the equatorial-tropical latitudes are small (Fig. 26, 27). This results in small fluctuations in temperature throughout the year. Therefore, the seasons of the year are determined there not by the course of temperatures, but by the annual rainfall regime. In extratropical latitudes, there are qualitative changes in the radiation balance from positive to negative values during the year. In summer, over vast expanses of temperate and partly high latitudes, the values of the radiation balance are significant (for example, in June on land near the Arctic Circle they are the same as in tropical deserts) and its fluctuations in latitudes are relatively small. This is reflected in the temperature regime and, accordingly, in the weakening of the interlatitudinal circulation during this period. In winter, over large expanses, the radiation balance is negative: the line of zero radiation balance of the coldest month passes over the land approximately along 40 ° latitude, over the oceans - along 45 °. Different thermobaric conditions in winter lead to the activation of atmospheric processes in temperate and subtropical latitude zones. The negative radiation balance in winter in temperate and polar latitudes is partly compensated by the influx of heat with air and water masses from the equatorial-tropical latitudes. In contrast to low latitudes in temperate and high latitudes, the seasons of the year are determined primarily by thermal conditions that depend on the radiation balance.
Rice. 26. Radiation balance of the earth's surface for June [in 10 2 MJ / (m 2 x M es.) |
In the mountains of all latitudes, the distribution of the radiation balance is complicated by the influence of height, duration of snow cover, insolation exposure of slopes, cloudiness, etc. In general, despite the increased values of total radiation in the mountains, the radiation balance is lower there due to the albedo of snow and ice, an increase in the proportion of effective radiation and other factors.
The Earth's atmosphere has its own radiation balance. The arrival of radiation into the atmosphere is due to the absorption of both short-wave solar radiation and long-wave terrestrial radiation. Radiation is consumed by the atmosphere with counter radiation, which is completely compensated by terrestrial radiation, and due to outgoing radiation. According to experts, the radiation balance of the atmosphere is negative (-29%).
In general, the radiation balance of the Earth's surface and atmosphere is 0, i.e., the Earth is in a state of radiative equilibrium. However, the excess of radiation on the Earth's surface and the lack of it in the atmosphere make one ask the question: why, with an excess of radiation, the Earth's surface does not incinerate, and the atmosphere, with its deficiency, does not freeze to a temperature of absolute zero? The fact is that between the surface of the Earth and the atmosphere (as well as between the surface and deep layers of the Earth and water) there are non-radiative methods of heat transfer. The first one is molecular thermal conductivity and turbulent heat transfer (H), during which the atmosphere is heated and heat is redistributed in it vertically and horizontally. The deep layers of the earth and water are also heated. The second is active heat exchange, which occurs when water passes from one phase state to another: during evaporation, heat is absorbed, and during condensation and sublimation of water vapor, the latent heat of vaporization (LE) is released.
It is non-radiative methods of heat transfer that balance the radiation balances of the earth's surface and atmosphere, bringing both to zero and preventing overheating of the surface and supercooling of the Earth's atmosphere. The earth's surface loses 24% of radiation as a result of water evaporation (and the atmosphere, respectively, receives the same amount due to subsequent condensation and sublimation of water vapor in the form of clouds and fogs) and 5% of radiation when the atmosphere is heated from the earth's surface. In total, this amounts to the very 29% of radiation that is excessive on the earth's surface and which is lacking in the atmosphere.
Rice. 27. Radiation balance of the earth's surface for December [in 10 2 MJ / (m 2 x M es.)]
Rice. 28. Components of the heat balance of the earth's surface in the daytime (according to S. P. Khromov)
The algebraic sum of all incomes and expenditures of heat on the earth's surface and in the atmosphere is called the heat balance; the radiation balance is thus the most important component of the heat balance. The equation for the heat balance of the earth's surface has the form:
B – LE – P±G = 0,
where B is the radiation balance of the earth's surface, LE is the heat consumption for evaporation (L is the specific heat of evaporation, £ is the mass of evaporated water), P is the turbulent heat exchange between the underlying surface and the atmosphere, G is the heat exchange with the underlying surface (Fig. 28). The loss of surface heat for heating the active layer during the day and summer is almost completely compensated by its return from the depths to the surface at night and in winter, therefore, the average long-term annual temperature of the upper layers of soil and water of the World Ocean is considered constant and G for almost any surface can be considered equal to zero. Therefore, in the long-term conclusion, the annual heat balance of the land surface and the World Ocean is spent on evaporation and heat exchange between the underlying surface and the atmosphere.
The distribution of the heat balance over the Earth's surface is more complex than the radiative one, due to numerous factors affecting it: cloudiness, precipitation, surface heating, etc. At different latitudes, the heat balance values differ from 0 in one direction or another: at high latitudes it negative, and in low - positive. The lack of heat in the northern and southern polar regions is compensated by its transfer from tropical latitudes mainly with the help of ocean currents and air masses, thereby establishing thermal equilibrium between different latitudes of the earth's surface.
The heat balance of the atmosphere is written as follows: –B + LE + P = 0.
Obviously, the mutually complementary thermal regimes of the Earth's surface and atmosphere balance each other: all solar radiation entering the Earth (100%) is balanced by the loss of Earth's radiation due to reflection (30%) and radiation (70%), therefore, in general, thermal The balance of the Earth, like the radiation one, is equal to 0. The Earth is in radiant and thermal equilibrium, and any violation of it can lead to overheating or cooling of our planet.
The nature of the heat balance and its energy level determine the features and intensity of most of the processes occurring in the geographic envelope, and above all the thermal regime of the troposphere.
Let us first consider the thermal conditions of the earth's surface and the uppermost layers of soil and water bodies. This is necessary because the lower layers of the atmosphere are heated and cooled most of all by radiative and non-radiative heat exchange with the upper layers of soil and water. Therefore, temperature changes in the lower layers of the atmosphere are primarily determined by changes in the temperature of the earth's surface and follow these changes.
The earth's surface, i.e., the surface of soil or water (as well as vegetation, snow, ice cover), continuously receives and loses heat in various ways. Through the earth's surface, heat is transferred upward - into the atmosphere and downward - into the soil or water.
First, the total radiation and the counter radiation of the atmosphere enter the earth's surface. They are absorbed to a greater or lesser extent by the surface, i.e., they go to heat the upper layers of soil and water. At the same time, the earth's surface itself radiates and loses heat in the process.
Secondly, heat comes to the earth's surface from above, from the atmosphere, by conduction. In the same way, heat escapes from the earth's surface into the atmosphere. By conduction, heat also leaves the earth's surface down into the soil and water, or comes to the earth's surface from the depths of the soil and water.
Thirdly, the earth's surface receives heat when water vapor condenses on it from the air or, on the contrary, loses heat when water evaporates from it. In the first case, latent heat is released, in the second case, heat passes into a latent state.
In any period of time, the same amount of heat goes up and down from the earth's surface as it receives from above and below during this time. If it were otherwise, the law of conservation of energy would not be fulfilled: it would be necessary to assume that energy arises or disappears on the earth's surface. However, it is possible that, for example, more heat may go up than came from above; in this case, the excess heat transfer should be covered by the arrival of heat to the surface from the depths of the soil or water.
So, the algebraic sum of all incomes and expenses of heat on the earth's surface should be equal to zero. This is expressed by the equation of the heat balance of the earth's surface.
To write this equation, first, we combine the absorbed radiation and the effective radiation into a radiation balance.
We will denote the arrival of heat from the air or its return to the air by thermal conductivity as P. The same income or consumption by heat exchange with deeper layers of soil or water will be called A. The loss of heat during evaporation or its arrival during condensation on the earth's surface will be denoted by LE, where L is the specific the heat of evaporation and E is the mass of evaporated or condensed water.
It can also be said that the meaning of the equation is that the radiative balance on the earth's surface is balanced by non-radiative heat transfer (Fig. 5.1).
Equation (1) is valid for any period of time, including for many years.
The fact that the heat balance of the earth's surface is zero does not mean that the surface temperature does not change. When the heat transfer is directed downwards, the heat that comes to the surface from above and leaves it deep into it remains to a large extent in the uppermost layer of soil or water (in the so-called active layer). The temperature of this layer, and therefore the temperature of the earth's surface, increases as well. On the contrary, when heat is transferred through the earth's surface from the bottom up, into the atmosphere, the heat escapes primarily from the active layer, as a result of which the surface temperature drops.
From day to day and from year to year, the average temperature of the active layer and the earth's surface in any place varies little. This means that during the day, almost as much heat enters the depths of the soil or water during the day as it leaves it at night. But still, during the summer days, the heat goes down a little more than it comes from below. Therefore, the layers of soil and water, and therefore their surface, are heated day by day. In winter, the reverse process occurs. These seasonal changes in heat input - heat consumption in soil and water almost balance out over the year, and the average annual temperature of the earth's surface and the active layer varies little from year to year.
Heat balance of the Earth- the ratio of the income and consumption of energy (radiant and thermal) on the earth's surface, in the atmosphere and in the Earth-atmosphere system. The main source of energy for the vast majority of physical, chemical and biological processes in the atmosphere, hydrosphere and in the upper layers of the lithosphere is solar radiation, so the distribution and ratio of the heat balance components characterize its transformations in these shells.
The heat balance is a particular formulation of the law of conservation of energy and is compiled for a section of the Earth's surface (the heat balance of the earth's surface); for a vertical column passing through the atmosphere (heat balance of the atmosphere); for the same column passing through the atmosphere and the upper layers of the lithosphere or the hydrosphere (thermal balance of the Earth-atmosphere system).
The equation for the heat balance of the earth's surface:
R + P + F0 + LE = 0. (15)
represents the algebraic sum of energy flows between an element of the earth's surface and the surrounding space. In this formula:
R - radiation balance, the difference between the absorbed short-wave solar radiation and long-wave effective radiation from the earth's surface.
P is the heat flux that occurs between the underlying surface and the atmosphere;
F0 - heat flow is observed between the earth's surface and deeper layers of the lithosphere or hydrosphere;
LE - heat consumption for evaporation, which is defined as the product of the mass of evaporated water E and the heat of evaporation L heat balance
These streams include the Radiation balance (or residual radiation) R - the difference between the absorbed short-wave solar radiation and the long-wave effective radiation from the earth's surface. The positive or negative value of the radiation balance is compensated by several heat fluxes. Since the temperature of the earth's surface is usually not equal to the air temperature, a heat flux P arises between the underlying surface and the atmosphere. A similar heat flux F0 is observed between the earth's surface and deeper layers of the lithosphere or hydrosphere. In this case, the heat flux in the soil is determined by molecular thermal conductivity, while in water bodies, heat transfer, as a rule, has a turbulent character to a greater or lesser extent. The heat flux F0 between the surface of the reservoir and its deeper layers is numerically equal to the change in the heat content of the reservoir over a given time interval and the heat transfer by currents in the reservoir. In the heat balance of the earth's surface, the heat consumption for evaporation LE is usually of significant importance, which is defined as the product of the mass of evaporated water E and the heat of evaporation L. The value of LE depends on the moistening of the earth's surface, its temperature, air humidity and the intensity of turbulent heat transfer in the surface air layer, which determines the rate of transfer of water vapor from the earth's surface to the atmosphere.
The atmosphere heat balance equation has the form:
Ra + Lr + P + Fa = ΔW, (16)
where ΔW is the change in heat content inside the vertical wall of the atmospheric column.
The heat balance of the atmosphere is composed of its radiation balance Ra; heat input or output Lr during phase transformations of water in the atmosphere (r is the sum of precipitation); the arrival or consumption of heat P, due to the turbulent heat exchange of the atmosphere with the earth's surface; heat gain or loss Fa caused by heat exchange through the vertical walls of the column, which is associated with ordered atmospheric motions and macroturbulence. In addition, the equation for the heat balance of the atmosphere includes the term ΔW, which is equal to the change in heat content inside the column.
The heat balance equation for the Earth-atmosphere system corresponds to the algebraic sum of the terms of the equations for the heat balance of the earth's surface and atmosphere. The components of the heat balance of the earth's surface and atmosphere for various regions of the globe are determined by meteorological observations (at actinometric stations, at special heat balance stations, on meteorological satellites of the Earth) or by climatological calculations.
The average latitudinal values of the components of the heat balance of the earth's surface for the oceans, land and Earth and the heat balance of the atmosphere are given in tables, where the values of the terms of the heat balance are considered positive if they correspond to the arrival of heat. Since these tables refer to average annual conditions, they do not include terms characterizing changes in the heat content of the atmosphere and the upper layers of the lithosphere, since for these conditions they are close to zero.
For the Earth as a planet, together with the atmosphere, the heat balance diagram is shown in Fig. A unit surface of the outer boundary of the atmosphere receives a solar radiation flux equal to an average of about 250 kcal / cm 2 per year, of which about 1/3 is reflected into the world space, and 167 kcal / cm 2 per year is absorbed by the Earth
Heat exchange spontaneous irreversible process of heat transfer in space, due to a non-uniform temperature field. In the general case, heat transfer can also be caused by the inhomogeneity of the fields of other physical quantities, for example, the difference in concentrations (diffusion thermal effect). There are three types of heat transfer: thermal conductivity, convection and radiant heat transfer (in practice, heat transfer is usually carried out by all 3 types at once). Heat transfer determines or accompanies many processes in nature (for example, the evolution of stars and planets, meteorological processes on the surface of the Earth, etc.). in technology and everyday life. In many cases, for example, when studying the processes of drying, evaporative cooling, diffusion, heat transfer is considered together with mass transfer. Heat transfer between two coolants through a solid wall separating them or through the interface between them is called heat transfer.
Thermal conductivity one of the types of heat transfer (energy of thermal motion of microparticles) from more heated parts of the body to less heated ones, leading to temperature equalization. With thermal conductivity, the transfer of energy in the body is carried out as a result of the direct transfer of energy from particles (molecules, atoms, electrons) that have more energy to particles with less energy. If the relative change in the thermal conductivity temperature at a distance of the mean free path of particles l is small, then the basic law of thermal conductivity (Fourier law) is satisfied: the heat flux density q is proportional to the temperature gradient grad T, i.e. (17)
where λ is the thermal conductivity, or simply thermal conductivity, does not depend on grad T [λ depends on the aggregate state of the substance (see table), its atomic and molecular structure, temperature and pressure, composition (in the case of a mixture or solution).
The minus sign on the right side of the equation indicates that the direction of the heat flow and the temperature gradient are mutually opposite.
The ratio of the Q value to the cross-sectional area F is called the specific heat flux or heat load and is denoted by the letter q.
(18)
The values of the thermal conductivity coefficient λ for some gases, liquids and solids at an atmospheric pressure of 760 mm Hg is selected from the tables.
Heat transfer. Heat transfer between two coolants through a solid wall separating them or through the interface between them. Heat transfer includes heat transfer from a hotter fluid to the wall, thermal conductivity in the wall, heat transfer from the wall to a colder moving medium. The intensity of heat transfer during heat transfer is characterized by a heat transfer coefficient k, numerically equal to the amount of heat that is transferred through a unit of wall surface per unit time at a temperature difference between liquids of 1 K; dimension k - W/(m2․K) [kcal/m2․°С)]. The value R, the reciprocal of the heat transfer coefficient, is called the total thermal resistance heat transfer. For example, R of a single-layer wall
,
where α1 and α2 are the heat transfer coefficients from the hot liquid to the wall surface and from the wall surface to the cold liquid; δ - wall thickness; λ is the coefficient of thermal conductivity. In most cases encountered in practice, the heat transfer coefficient is determined empirically. In this case, the results obtained are processed by the similarity theory methods
Radiant heat transfer - radiative heat transfer is carried out as a result of the processes of transformation of the internal energy of matter into radiation energy, the transfer of radiation energy and its absorption by matter. The course of processes of radiant heat transfer is determined by the mutual arrangement in space of the bodies exchanging heat, the properties of the medium separating these bodies. The essential difference between radiant heat transfer and other types of heat transfer (thermal conduction, convective heat transfer) is that it can also occur in the absence of a material medium separating the heat transfer surfaces, since it is carried out as a result of the propagation of electromagnetic radiation.
The radiant energy incident in the process of radiant heat transfer onto the surface of an opaque body and characterized by the value of the incident radiation flux Qfall is partially absorbed by the body and partially reflected from its surface (see Fig.).
The flux of absorbed radiation Qabs is determined by the relation:
Qabs \u003d A Qpad, (20)
where A is the absorptive capacity of the body. Due to the fact that for an opaque body
Qfall \u003d Qab + Qotr, (21)
where Qotr is the flux of radiation reflected from the surface of the body, this last value is equal to:
Qotr \u003d (1 - A) Qpad, (22)
where 1 - A \u003d R is the reflectivity of the body. If the absorption capacity of a body is 1, and therefore its reflectivity is 0, that is, the body absorbs all the energy incident on it, then it is called an absolutely black body. Any body whose temperature is different from absolute zero emits energy due to the heating of the body. This radiation is called the body's own radiation and is characterized by the flux of its own radiation Qe. Self-radiation, related to the unit surface of the body, is called the flux density of its own radiation, or the emissivity of the body. The latter, in accordance with the Stefan-Boltzmann law of radiation, is proportional to the temperature of the body to the fourth power. The ratio of the emissivity of a body to the emissivity of a completely black body at the same temperature is called the degree of blackness. For all bodies, the degree of blackness is less than 1. If for some body it does not depend on the wavelength of radiation, then such a body is called gray. The nature of the distribution of radiation energy of a gray body over wavelengths is the same as that of an absolutely black body, that is, it is described by Planck's law of radiation. The degree of blackness of a gray body is equal to its absorption capacity.
The surface of any body entering the system emits fluxes of reflected radiation Qotr and its own radiation Qcob; the total amount of energy leaving the surface of the body is called the effective radiation flux Qeff and is determined by the relation:
Qeff \u003d Qotr + Qcob. (23)
Part of the energy absorbed by the body returns to the system in the form of its own radiation, so the result of radiant heat transfer can be represented as the difference between the fluxes of its own and absorbed radiation. Value
Qpez \u003d Qcob - Qabs (24)
is called the resulting radiation flux and shows how much energy the body receives or loses per unit time as a result of radiant heat transfer. The resulting radiation flux can also be expressed as
Qpez \u003d Qeff - Qpad, (25)
that is, as the difference between the total consumption and the total arrival of radiant energy on the surface of the body. Hence, given that
Qpad = (Qcob - Qpez) / A, (26)
we obtain an expression that is widely used in calculations of radiant heat transfer:
The task of calculating radiant heat transfer is, as a rule, to find the resulting radiation fluxes on all surfaces included in a given system, if the temperatures and optical characteristics of all these surfaces are known. To solve this problem, in addition to the last relation, it is necessary to find out the relationship between the flux Qinc on a given surface and the fluxes Qeff on all surfaces included in the radiant heat exchange system. To find this connection, the concept of the average angular coefficient of radiation is used, which shows what proportion of the hemispherical (that is, emitted in all directions within the hemisphere) radiation of a certain surface included in the radiant heat exchange system falls on this surface. Thus, the flux Qfall on any surfaces included in the radiative heat exchange system is defined as the sum of the products Qeff of all surfaces (including the given one, if it is concave) and the corresponding angular coefficients of radiation.
Radiant heat transfer plays a significant role in heat transfer processes occurring at temperatures of about 1000 °C and above. It is widely used in various fields of technology: in metallurgy, thermal power engineering, nuclear power engineering, rocket technology, chemical technology, drying technology, and solar technology.
