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
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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) monuments of history and culture are located, places of interest, 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 facilities; a … - 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:
TRADING PASSIVE - see PASSIVE TRADING BALANCE… - 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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PAYMENT PASSIVE. see PASSIVE BALANCE OF PAYMENTS... - BALANCE in the Dictionary of Economic Terms:
FOREIGN TRADE PAYMENTS - see FOREIGN TRADE BALANCE OF PAYMENTS ... - BALANCE in the Dictionary of Economic Terms:
PAYMENT ACTIVE - see ACTIVE BALANCE OF PAYMENTS ... - BALANCE in the Dictionary of Economic Terms:
PAYMENT - see PAYMENT ... - BALANCE in the Dictionary of Economic Terms:
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:
INTER-BRANCH - see INTER-BRANCH ... - BALANCE in the Dictionary of Economic Terms:
MATERIAL - see MATERIAL ... - BALANCE in the Dictionary of Economic Terms:
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...
Let us first dwell on 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 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 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 a 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.
Heat balance of the Earth-atmosphere system
1. The earth as a whole, the atmosphere in particular and the earth's surface are in a state of thermal equilibrium, if we consider conditions over a long period (a year or, better, a number of years). Their average temperatures change little from year to year, and from one long-term period to another remain almost unchanged. It follows that the influx and loss of heat over a sufficiently long period are equal or almost equal.
The earth receives heat by absorbing solar radiation in the atmosphere and especially on the earth's surface. It loses heat by emitting long-wave radiation from the earth's surface and atmosphere into the world space. With the thermal equilibrium of the Earth as a whole, the influx of solar radiation (to the upper boundary of the atmosphere) and the return of radiation from the upper boundary of the atmosphere to the world space must be equal. In other words, at the upper boundary of the atmosphere there must be radiative equilibrium, i.e., a radiation balance equal to zero.
The atmosphere, taken separately, gains and loses heat by absorbing solar and terrestrial radiation and giving its radiation up and down. In addition, it exchanges heat with the earth's surface in a non-radiative way. Heat is transferred from the earth's surface to the air or vice versa by conduction. Finally, heat is spent on the evaporation of water from the underlying surface; then it is released into the atmosphere when water vapor condenses. All these heat fluxes directed into and out of the atmosphere must balance over a long time.
Rice. 37. Heat balance of the Earth, atmosphere and earth's surface. 1 - short-wave radiation, II - long-wave radiation, III - non-radiation exchange.
Finally, on the earth's surface, the influx of heat due to the absorption of solar and atmospheric radiation, the release of heat by radiation of the earth's surface itself and the non-radiative heat exchange between it and the atmosphere are balanced.
2. Let's take the solar radiation entering the atmosphere as 100 units (Fig. 37). Of this amount, 23 units are reflected back by the clouds and go into the world space, 20 units are absorbed by the air and clouds and thereby go to heat the atmosphere. Another 30 units of radiation are dissipated in the atmosphere and 8 units of them go into the world space. 27 units of direct and 22 units of diffuse radiation reach the earth's surface. Of these, 25 + 20 = 45 units are absorbed and heat the upper layers of soil and water, and 2 + 2 = 4 units are reflected into the world space.
So, from the upper boundary of the atmosphere goes back to the world space 23 + 8 + 4 = 35 units<неиспользованной>solar radiation, i.e. 35% of its inflow to the boundary of the atmosphere. This value (35%) is called, as we already know, the Earth's albedo. To maintain the radiation balance at the upper boundary of the atmosphere, it is necessary that another 65 units of long-wave radiation from the earth's surface go out through it.
3. Let us now turn to the earth's surface. As already mentioned, it absorbs 45 units of direct and diffuse solar radiation. In addition, a flux of long-wave radiation from the atmosphere is directed towards the earth's surface. The atmosphere, according to its temperature conditions, radiates 157 units of energy. Of these 157 units, 102 are directed towards the earth's surface and are absorbed by it, and 55 go into world space. Thus, in addition to 45 units of short-wave solar radiation, the earth's surface absorbs twice as much long-wave atmospheric radiation. In total, the earth's surface receives 147 units of heat from the absorption of radiation.
Obviously, at thermal equilibrium, it should lose the same amount. Through its own long-wave radiation, it loses 117 units. Another 23 units of heat are consumed by the earth's surface during the evaporation of water. Finally, by conduction, in the process of heat exchange between the earth's surface and the atmosphere, the surface loses 7 units of heat (heat leaves it in the atmosphere in large quantities, but is compensated by the reverse transfer, which is only 7 units less).
In total, therefore, the earth's surface loses 117 + 23 + + 7 = 147 units of heat, i.e. the same amount as it receives by absorbing solar and atmospheric radiation.
Of the 117 units of long-wave radiation by the earth's surface, 107 units are absorbed by the atmosphere, and 10 units go beyond the atmosphere into the world space.
4. Now let's do the calculation for the atmosphere. It is said above that it absorbs 20 units of solar radiation, 107 units of terrestrial radiation, 23 units of condensation heat and 7 units in the process of heat exchange with the earth's surface. In total, this will amount to 20 + 107 + 23 + 7 = 157 units of energy, i.e. as much as the atmosphere itself radiates.
Finally, we turn again to the upper surface of the atmosphere. Through it comes 100 units of solar radiation and goes back 35 units of reflected and scattered solar radiation, 10 units of terrestrial radiation and 55 units of atmospheric radiation, for a total of 100 units. Thus, even at the upper boundary of the atmosphere there is a balance between the influx and return of energy, and here, only radiant energy. There are no other mechanisms of heat exchange between the Earth and the world space, except for radiative processes.
All figures given are calculated on the basis of by no means exhaustive observations. Therefore, they should not be looked upon as absolutely accurate. They have been subjected to minor changes more than once, which, however, do not change the essence of the calculation.
5. Let us note that the atmosphere and the earth's surface, taken separately, radiate much more heat than they absorb solar radiation in the same time. This may seem incomprehensible. But in essence it is a mutual exchange, a mutual<перекачка>radiation. For example, the earth's surface ultimately loses not 117 units of radiation at all, it receives 102 units back by absorbing counter radiation; the net loss is only 117-102=15 units. Only 65 units of terrestrial and atmospheric radiation go through the upper boundary of the atmosphere into the world space. The influx of 100 units of solar radiation to the boundary of the atmosphere just balances the net loss of radiation by the Earth through reflection (35) and radiation (65).
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Let us first dwell on 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 and in different ways receives and loses heat. 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. are used to heat the upper layers of soil and water. At the same time, the earth's surface itself radiates and thereby loses heat.
Secondly, heat comes to the earth's surface from above, from the atmosphere, through turbulent heat 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 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.
We will not dwell on less important processes (for example, the expenditure of heat for the melting of snow lying on the surface, or the propagation of heat into the depths of the soil along with precipitation water).
Let us consider the earth's surface as an idealized geometric surface without thickness, the heat capacity of which, therefore, is equal to zero. Then it is clear that in any period of time the same amount of heat will go up and down from the earth's surface as it receives from above and below during the same time. Naturally, if we consider not the surface, but some layer of the earth's surface, then there may not be equality of incoming and outgoing heat fluxes. In this case, the excess of incoming heat flows over outgoing flows, in accordance with the law of conservation of energy, will be used to heat this layer, and in the opposite case, to cool it.
So, the algebraic sum of all heat inflows and outflows on the earth's surface must be equal to zero - this is the equation for the heat balance of the earth's surface. To write the heat balance equation, we combine the absorbed radiation and the effective radiation into the radiation balance:
B = (S sin h + D)(1 – A) – E s .
The arrival of heat from the air or its release into the air by thermal conduction is denoted by the letter R. The same income or consumption by heat exchange with deeper layers of soil or water will be denoted by G. The loss of heat during evaporation or its arrival during condensation on the earth's surface will be denoted LE, where L is the specific heat of vaporization and E is the mass of evaporated or condensed water. Let us recall one more component - the energy spent on photosynthetic processes - PAR, however, is very small in comparison with the others, therefore, in most cases it is not indicated in the equation. Then the equation for the heat balance of the earth's surface takes the form
AT+ R+ G + LE + Q PAR = 0 or AT+ R+ G + LE = 0
It can also be noted that the meaning of the equation is that the radiative balance on the earth's surface is balanced by non-radiative heat transfer.
The heat balance equation is valid for any time, including a multi-year period.
The fact that the heat balance of the earth's surface is zero does not mean that the surface temperature does not change. If the heat transfer is directed downwards, then 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, consequently, the temperature of the earth's surface increases as well. When heat is transferred through the earth's surface from bottom to top, into the atmosphere, heat escapes, first of all, 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, as much heat enters the depths of the soil or water during the day as it leaves it at night. Since during the summer day more heat goes down than comes from below, the layers of soil and water and their surface heat up day by day. In winter, the reverse process occurs. Seasonal changes in heat input and output in soil and water are almost balanced over the year, and the average annual temperature of the earth's surface and the active layer varies little from year to year.
There are sharp differences in the heating and thermal characteristics of the surface layers of the soil and the upper layers of the water basins. In soil, heat propagates vertically by molecular heat conduction, and in lightly moving water, also by turbulent mixing of water layers, which is much more efficient. Turbulence in water bodies is primarily due to waves and currents. At night and in the cold season, thermal convection joins this kind of turbulence: water cooled on the surface sinks down due to increased density and is replaced by warmer water from the lower layers. In the oceans and seas, evaporation also plays a role in the mixing of layers and in the heat transfer associated with it. With significant evaporation from the sea surface, the upper layer of water becomes more saline and therefore more dense, as a result of which the water sinks from the surface to the depths. In addition, radiation penetrates deeper into water compared to soil. Finally, the heat capacity of water is greater than that of soil, and the same amount of heat heats a mass of water to a lower temperature than the same mass of soil.
As a result, daily temperature fluctuations in water extend to a depth of about tens of meters, and in soil - less than one meter. Annual temperature fluctuations in water extend to a depth of hundreds of meters, and in soil - only 10–20 m.
So, the heat that comes to the surface of the water during the day and summer penetrates to a considerable depth and heats up a large thickness of the water. The temperature of the upper layer and the surface of the water itself rises little at the same time. In the soil, the incoming heat is distributed in a thin top layer, which is very hot. Member G in the heat balance equation for water is much greater than for soil, and P correspondingly less.
At night and in winter, water loses heat from the surface layer, but instead of it comes the accumulated heat from the underlying layers. Therefore, the temperature at the surface of the water decreases slowly. On the soil surface, the temperature drops rapidly during heat transfer: the heat accumulated in the thin upper layer quickly leaves it and leaves without being replenished from below.
As a result, during the day and summer, the temperature on the soil surface is higher than the temperature on the water surface; lower at night and in winter. This means that daily and annual temperature fluctuations on the soil surface are greater, and much greater than on the water surface.
Due to these differences in the distribution of heat, the water basin accumulates a large amount of heat in a sufficiently thick layer of water during the warm season, which is released into the atmosphere during the cold season. The soil during the warm season gives off at night most of the heat that it receives during the day, and accumulates little of it by winter. As a result, the air temperature over the sea is lower in summer and higher in winter than over land.
| Table of contents |
|---|
| Climatology and meteorology |
| DIDACTIC PLAN |
| Meteorology and climatology |
| Atmosphere, weather, climate |
| Meteorological observations |
| Application of cards |
| Meteorological Service and World Meteorological Organization (WMO) |
| Climate-forming processes |
| Astronomical factors |
| Geophysical factors |
| Meteorological factors |
| About solar radiation |
| Thermal and radiative equilibrium of the Earth |
| direct solar radiation |
| Changes in solar radiation in the atmosphere and on the earth's surface |
| Radiation Scattering Phenomena |
| Total radiation, reflected solar radiation, absorbed radiation, PAR, Earth's albedo |
| Radiation of the earth's surface |
| Counter-radiation or counter-radiation |
| Radiation balance of the earth's surface |
| Geographic distribution of the radiation balance |
| Atmospheric pressure and baric field |
| pressure systems |
| pressure fluctuations |
| Air acceleration due to baric gradient |
| The deflecting force of the Earth's rotation |
| Geostrophic and gradient wind |
| baric wind law |
| Fronts in the atmosphere |
| Thermal regime of the atmosphere |
| Thermal balance of the earth's surface |
| Daily and annual variation of temperature on the soil surface |
| Air mass temperatures |
| Annual amplitude of air temperature |
| Continental climate |
| Cloud cover and precipitation |
| Evaporation and saturation |
| Humidity |
| Geographic distribution of air humidity |
| atmospheric condensation |
| Clouds |
| International cloud classification |
| Cloudiness, its daily and annual variation |
| Precipitation from clouds (precipitation classification) |
| Characteristics of the precipitation regime |
| The annual course of precipitation |
| Climatic significance of snow cover |
| Atmospheric chemistry |
| The chemical composition of the Earth's atmosphere |
| Chemical composition of clouds |
| Chemical composition of precipitation |
In order to correctly assess the degree of heating and cooling of various earth surfaces, calculate evaporation for , determine changes in the moisture content in the soil, develop methods for predicting freezing, and also evaluate the impact of reclamation work on the climatic conditions of the surface air layer, data on the heat balance of the earth's surface are needed.
The earth's surface continuously receives and loses heat as a result of exposure to a variety of flows of short-wave and long-wave radiation. Absorbing to a greater or lesser extent total radiation and counter radiation, the earth's surface heats up and emits long-wave radiation, which means it loses heat. The value characterizing the loss of heat of the earth
surface is the effective radiation. It is equal to the difference between the own radiation of the earth's surface and the counter radiation of the atmosphere. Since the counter radiation of the atmosphere is always somewhat less than that of the earth, this difference is positive. In the daytime, the effective radiation is blocked by the absorbed short-wave radiation. At night, in the absence of short-wave solar radiation, effective radiation lowers the temperature of the earth's surface. In cloudy weather, due to the increase in the counter radiation of the atmosphere, the effective radiation is much less than in clear weather. Less and nightly cooling of the earth's surface. In middle latitudes, the earth's surface loses through effective radiation about half of the amount of heat that they receive from absorbed radiation.
The arrival and consumption of radiant energy is estimated by the value of the radiation balance of the earth's surface. It is equal to the difference between the absorbed and effective radiation, the thermal state of the earth's surface depends on it - its heating or cooling. During the day, it is positive almost all the time, i.e., the heat input exceeds the consumption. At night, the radiation balance is negative and equal to the effective radiation. The annual values of the radiation balance of the earth's surface, with the exception of the highest latitudes, are everywhere positive. This excess heat is spent on heating the atmosphere by turbulent heat conduction, on evaporation, and on heat exchange with deeper layers of soil or water.
If we consider the temperature conditions for a long period (a year or better a number of years), then the earth's surface, the atmosphere separately and the "Earth-atmosphere" system are in a state of thermal equilibrium. Their average temperature varies little from year to year. In accordance with the law of conservation of energy, we can assume that the algebraic sum of heat fluxes coming to the earth's surface and leaving it is equal to zero. This is the equation for the heat balance of the earth's surface. Its meaning is that the radiation balance of the earth's surface is balanced by non-radiative heat transfer. The heat balance equation, as a rule, does not take into account (because of their smallness) such flows as heat transferred by precipitation, energy consumption for photosynthesis, heat gain from biomass oxidation, as well as heat consumption for melting ice or snow, heat gain from freezing water.
The thermal balance of the "Earth-atmosphere" system for a long period is also equal to zero, i.e., the Earth as a planet is in thermal equilibrium: the solar radiation arriving at the upper boundary of the atmosphere is balanced by the radiation leaving the atmosphere from the upper boundary of the atmosphere.
If we take the air coming to the upper boundary as 100%, then 32% of this amount is dissipated in the atmosphere. Of these, 6% goes back into the world space. Consequently, 26% comes to the earth's surface in the form of scattered radiation; 18% of radiation is absorbed by ozone, aerosols and is used to heat the atmosphere; 5% is absorbed by clouds; 21% of radiation escapes into space as a result of reflection from clouds. Thus, the radiation coming to the earth's surface is 50%, of which direct radiation accounts for 24%; 47% is absorbed by the earth's surface, and 3% of the incoming radiation is reflected back into space. As a result, 30% of solar radiation escapes from the upper boundary of the atmosphere into outer space. This value is called the planetary albedo of the Earth. For the Earth-atmosphere system, 30% of reflected and scattered solar radiation, 5% of terrestrial radiation and 65% of atmospheric radiation, i.e., only 100%, go back into space through the upper boundary of the atmosphere.
