The heat balance of the Earth, atmosphere and earth's surface Over a long period, the heat balance is zero, i.e., the Earth is in thermal equilibrium. I - shortwave radiation, II - longwave radiation, III - non-radiative exchange.
Electromagnetic Radiation Radiation or radiation is a form of matter other than matter. A special case of radiation is visible light; but radiation also includes gamma rays that are not perceived by the eye, x-rays, ultraviolet and infrared radiation, radio waves, including television waves.
Characteristics of electromagnetic waves Radiation propagates in all directions from the emitter source in the form of m electromagnetic waves with the speed of light in a vacuum of about 300,000 km/s. Wavelength is the distance between adjacent maxima (or minima). m The oscillation frequency is the number of oscillations per second.
Wavelengths Ultraviolet radiation - wavelength from 0.01 to 0.39 microns. It is invisible, that is, it is not perceived by the eye. Visible light perceived by the eye, wavelengths 0.40 0.76 microns. Waves around 0.40 µm are purple, waves around 0.76 µm are red. Between 0.40 and 0.76 microns is the light of all colors of the visible spectrum. Infrared radiation - waves > 0.76 microns and up to several hundred microns are invisible to the human eye. In meteorology, it is customary to distinguish shortwave and longwave radiation. Shortwave is called radiation in the wavelength range from 0.1 to 4 microns. P
Wavelengths When white light is decomposed by a prism into a continuous spectrum, the colors in it gradually pass one into another. It is generally accepted that within certain limits of wavelengths (nm) radiation has the following colors: 390-440 - violet 440-480 blue 480-510 - blue 510-550 - green 550-575 yellow-green 575-585 yellow 585-620 - orange 630-770 - red
Wavelength perception The human eye is most sensitive to yellow-green radiation with a wavelength of about 555 nm. There are three radiation zones: blue-violet (wavelength 400-490 nm), green (length 490-570 nm) red (length 580-720 nm). These spectral zones are also the zones of predominant spectral sensitivity of the eye detectors and three layers of color film.
ABSORPTION OF SOLAR RADIATION IN THE ATMOSPHERE About 23% of direct solar radiation is absorbed in the atmosphere. e Absorption is selective: different gases absorb radiation in different parts of the spectrum and to different degrees. Nitrogen absorbs R very small wavelengths in the ultraviolet part of the spectrum. The energy of solar radiation in this part of the spectrum is completely negligible, so the absorption by nitrogen has practically no effect on the flux of solar radiation. Oxygen absorbs more, but also very little - in two narrow sections of the visible part of the spectrum and in the ultraviolet part. Ozone absorbs ultraviolet and visible solar radiation. There is very little of it in the atmosphere, but it absorbs ultraviolet radiation so strongly in upper layers atmosphere, that in the solar spectrum near the earth's surface, waves shorter than 0.29 microns are not observed at all. Its absorption of solar radiation by ozone reaches 3% of direct solar radiation.
ABSORPTION OF SOLAR RADIATION IN THE ATMOSPHERE CO 2 absorbs strongly in the infrared spectrum, but its content in the atmosphere is very small, so its absorption of direct solar radiation is generally small. Water vapor is the main absorber of radiation, concentrated in the troposphere. Absorbs radiation in the visible and near infrared regions of the spectrum. Clouds and atmospheric impurities (aerosol particles) absorb solar radiation in different parts of the spectrum, depending on the composition of the impurities. Water vapor and aerosols absorb about 15%, clouds 5% of radiation.
Heat balance of the Earth Scattered radiation passes through the atmosphere and is scattered by gas molecules. Such radiation is 70% in the polar latitudes and 30% in the tropics.
The heat balance of the Earth 38% of the scattered radiation returns to space. It gives the blue color to the sky and diffuses light before and after sunset.
Heat balance of the Earth Direct + diffuse = total R 4% is reflected by the atmosphere 10% is reflected by the earth's surface 20% is converted into thermal energy 24% is spent on air heating Total heat loss through the atmosphere is 58% of all received
Air advection Movement of air in a horizontal direction. We can talk about advection: air masses, heat, water vapor, moment of motion, vortex of speed, etc. Atmospheric phenomena that occur as a result of advection are called advective: advective fogs, advective thunderstorms, advective frosts, etc.
ALBEDO 1. In a broad sense, the reflectivity of the surface: water, vegetation (forest, steppe), arable land, clouds, etc. For example, Albedo of forest crowns is 10 - 15%, grass - 20 - 25%, sand - 30 - 35%, freshly fallen snow - 50 - 75% or more. 2. Albedo of the Earth - the percentage of solar radiation reflected by the globe together with the atmosphere back into the world space, to the solar radiation that arrived at the boundary of the atmosphere. A = O / P The return of radiation by the Earth occurs by reflection from the earth's surface and clouds of long-wave radiation, as well as scattering of direct short-wave radiation by the atmosphere. The snow surface has the highest reflectivity (85%). Earth's albedo is about 42%
Consequences of the inversion When the normal process of convection stops, the lower layer of the atmosphere is polluted Winter smoke in the city of Shanghai, the boundary of the vertical distribution of air is clearly visible
Temperature inversion The sinking of cold air creates a steady state of the atmosphere. The smoke from the chimney cannot overcome the descending air mass
Pressure stroke atmospheric air. 760 mm tr. Art. = 1033 Pa atmospheric pressure
Water in the atmosphere The total volume is 12 - 13 thousand km 3 of water vapor. Evaporation from the surface of the ocean 86% Evaporation from the surface of the continents 14% The amount of water vapor decreases with height, but the intensity of this process depends on: surface temperature and humidity, wind speed and atmospheric pressure
Atmospheric Humidity Characteristics Air humidity is the amount of water vapor in the air. Absolute air humidity - the content of water vapor (g) per 1 m 3 of air or its pressure (mm Hg) Relative humidity - the degree of saturation of air with water vapor (%)
Atmospheric Humidity Characteristics Maximum moisture saturation is the limit of water vapor content in the air at a given temperature. Dew point - the temperature at which the water vapor contained in the air saturates it (τ)
Atmospheric humidity characteristics Evaporation - the actual evaporation from a given surface at a given temperature Evaporation - the maximum possible evaporation at a given temperature
Atmospheric Humidity Characteristics Evaporation is equal to evapotranspiration over the water surface, and much less over land. At high temperatures, absolute humidity increases, relative humidity remains the same if there is not enough water.
Atmospheric Humidity Characteristics In cold air, with low absolute humidity, the relative humidity can reach 100%. Precipitation falls when the dew point is reached. In cold climates, even at very low relative humidity.
Causes of changes in air humidity 1. ZONALITY Absolute humidity decreases from the equator (20 - 30 mm) to the poles (1 - 2 mm). Relative humidity changes little (70 - 80%).
Causes of changes in air humidity 2. The annual course of absolute humidity corresponds to the course of temperatures: the warmer, the higher
INTERNATIONAL CLASSIFICATION OF CLOUDS Clouds are divided into 10 main forms (genera) according to their appearance. In the main genera, there are: species, varieties, and other features; as well as intermediate forms. g Cloudiness is measured in points: 0 - cloudless; 10 - the sky is completely covered with clouds.
INTERNATIONAL CLASSIFICATION OF CLOUDS Types of clouds Russian name Latin name I Cirrus (Ci) II Cirrocumulus (Cc) III Cirrostratus (Cs) IV Altocumulus (Ac) V Altostratus (As) VI Nimbostratus (Ns) VII Stratocumulus ( Sc) VIII Stratus Stratus (St) IX Cumulus Cumulus (Cu) X Cumulonimbus Cumulonimbus (Cb) Stage height H = 7 – 18 km H = 2 – 8 km H = up to 2 km
Clouds of the lower tier. Stratostratus clouds have the same origin as Altostratus. However, their layer is several kilometers. These clouds are in the lower, middle and often upper tiers. In the upper part they consist of the smallest drops and snowflakes, in the lower part they can contain large drops and snowflakes. Therefore, the layer of these clouds has a dark gray color. The sun and moon do not shine through it. As a rule, overcast rain or snow falls from stratocinimbus clouds, reaching the earth's surface.
Mid-tier clouds Altocumulus clouds are cloud layers or ridges of white or gray color (or both). These are rather thin clouds, more or less obscuring the sun. Layers or ridges consist of flat shafts, disks, plates, often arranged in rows. Optical phenomena appear in them - crowns, iridescence - iridescent coloring of the edges of clouds directed towards the sun. Irisa indicates that altocumulus clouds are composed of very small, uniform droplets, usually supercooled.
Mid-tier clouds Optical phenomena in clouds Altocumulus Clouds Crowns in clouds Cloud iridescence Halo
Upper Clouds These are the highest clouds in the troosphere, form at the lowest temperatures, and are composed of ice crystals, are white, translucent, and obscure little sunlight.
Phase composition of clouds Water (droplet) clouds, consisting only of drops. They can exist not only at positive temperatures, but also at negative ones (-100 C and below). In this case, the droplets are in a supercooled state, which is quite usual under atmospheric conditions. c Mixed clouds consisting of a mixture of supercooled clouds and ice crystals. They can exist, as a rule, at temperatures from -10 to -40°C. Ice (crystalline) clouds, consisting only of ice and crystals. They predominate, as a rule, at temperatures below 30°C.
The concept of the thermobaric field of the Earth
seasonal fluctuations radiation balance
Seasonal fluctuations in the radiation regime of the Earth as a whole correspond to changes in the exposure of the northern and southern hemispheres during the annual revolution of the Earth around the Sun.
In the equatorial belt there are no seasonal fluctuations in solar heat: both in December and July, the radiation balance is 6-8 kcal/cm 2 on land and 10-12 kcal/cm 2 at sea per month.
In tropical zones seasonal fluctuations are already quite clearly expressed. In the Northern Hemisphere - in North Africa, South Asia and Central America- in December, the radiation balance is 2-4 kcal / cm 2, and in June 6-8 kcal / cm 2 per month. The same picture is observed in southern hemisphere: radiation balance is higher in December (summer), lower in June (winter).
Throughout the temperate zone in December north of the subtropics (zero balance line passes through France, Central Asia and the island of Hokkaido) the balance is negative. In June, even near the Arctic Circle, the radiation balance is 8 kcal/cm2 per month. The greatest amplitude of the radiation balance is characteristic of the continental Northern Hemisphere.
The thermal regime of the troposphere is determined both by the influx of solar heat and by the dynamics of air masses, which carry out the advection of heat and cold. On the other hand, the air movement itself is caused by a temperature gradient (a drop in temperature per unit distance) between equatorial and polar latitudes and between oceans and continents. As a result of these complex dynamic processes, the thermobaric field of the Earth was formed. Both of its elements - temperature and pressure - are so interconnected that it is customary in geography to speak of a single thermobaric field of the Earth.
The heat received by the earth's surface is converted and redistributed by the atmosphere and hydrosphere. Heat is spent mainly on evaporation, turbulent heat exchange, and on the redistribution of heat between land and ocean.
The largest number heat is spent on the evaporation of water from the oceans and continents. In the tropical latitudes of the oceans, evaporation consumes approximately 100-120 kcal / cm 2 per year, and in water areas with warm currents up to 140 kcal / cm 2 per year, which corresponds to the evaporation of a water layer of 2 m thick. In the equatorial belt, much less energy is spent on evaporation, that is, approximately 60 kcal / cm 2 per year; this is equivalent to the evaporation of a one-meter layer of water.
On the continents, the maximum heat consumption for evaporation occurs in the equatorial zone with its humid climate. In the tropical latitudes of the land there are deserts with negligible evaporation. In temperate latitudes, the cost of heat for evaporation in the oceans is 2.5 times greater than on land. The surface of the ocean absorbs from 55 to 97% of all radiation falling on it. On the entire planet, 80% of solar radiation is spent on evaporation, and about 20% on turbulent heat transfer.
The heat expended on the evaporation of water is transferred to the atmosphere during the condensation of steam in the form of latent heat of vaporization. This process plays a major role in heating the air and the movement of air masses.
The maximum amount of heat for the entire troposphere from the condensation of water vapor is received by equatorial latitudes - approximately 100-140 kcal / cm 2 per year. This is due to the influx of a huge amount of moisture brought here by the trade winds from tropical waters, and the rise of air above the equator. In dry tropical latitudes, the amount of latent heat of vaporization is naturally negligible: less than 10 kcal/cm2 per year in continental deserts and about 20 kcal/cm2 per year over the oceans. Water plays a decisive role in the thermal and dynamic regime of the atmosphere.
Radiative heat also enters the atmosphere through turbulent air heat exchange. Air is a poor conductor of heat, therefore, molecular thermal conductivity can provide heating of only a small (a few meters) lower layer of the atmosphere. The troposphere is heated by turbulent, jet, vortex mixing: the air of the lower layer adjacent to the earth heats up, rises in jets, and the upper cold air descends in its place, which also heats up. In this way, heat is quickly transferred from the soil to the air, from one layer to another.
Turbulent heat flow is greater over continents and less over oceans. It reaches its maximum value in tropical deserts, up to 60 kcal / cm 2 per year, in the equatorial and subtropical zones it decreases to 30-20 kcal / cm 2, and in temperate - 20-10 kcal / cm 2 per year. On the larger area oceans water gives the atmosphere about 5 kcal / cm 2 per year, and only in subpolar latitudes the air from the Gulf Stream and Kuroshivo receives heat up to 20-30 kcal / cm 2 per year.
In contrast to the latent heat of vaporization, the turbulent flow is weakly retained by the atmosphere. Over deserts, it is transmitted upwards and dissipates, which is why desert zones act as areas of cooling of the atmosphere.
The thermal regime of the continents is different due to their geographical position. The cost of heat for evaporation on the northern continents is determined by their position in the temperate zone; in Africa and Australia - the aridity of their large areas. In all oceans, a huge proportion of heat is spent on evaporation. Then part of this heat is transferred to the continents and insulates the climate of high latitudes.
An analysis of heat transfer between the surface of continents and oceans allows us to draw the following conclusions:
1. In the equatorial latitudes of both hemispheres, the atmosphere receives heat from the heated oceans up to 40 kcal / cm 2 per year.
2. Almost no heat enters the atmosphere from continental tropical deserts.
3. The line of zero balance passes through the subtropics, near 40 0 latitude.
4. In temperate latitudes, the heat consumption by radiation is greater than the absorbed radiation; this means that the climatic air temperature of temperate latitudes is determined not by solar, but by advective (brought from low latitudes) heat.
5. The radiation balance of the Earth-Atmosphere is dissymmetric relative to the plane of the equator: in the polar latitudes of the northern hemisphere it reaches 60, and in the corresponding southern latitudes - only 20 kcal/cm 2 per year; heat is transferred to North hemisphere more intense than in the south, approximately 3 times. The balance of the Earth-atmosphere system determines the air temperature.
8.16. Heating and cooling of the atmosphere in the process of interaction of the "ocean-atmosphere-continent" system
The absorption of solar rays by air gives no more than 0.1 0 C of heat to the lower kilometer layer of the troposphere. The atmosphere receives no more than 1/3 of the heat directly from the Sun, and it absorbs 2/3 from the earth's surface and, above all, from the hydrosphere, which transfers heat to it through water vapor evaporated from the surface of the water shell.
The sun's rays that have passed through the gas envelope of the planet meet water in most places on the earth's surface: on the oceans, in water bodies and land swamps, in moist soil and in the foliage of plants. The thermal energy of solar radiation is spent primarily on evaporation. The amount of heat expended per unit of evaporating water is called the latent heat of vaporization. When steam condenses, the heat of vaporization enters the air and heats it.
The assimilation of solar heat by water bodies differs from the heating of land. The heat capacity of water is about 2 times greater than that of soil. With the same amount of heat, water heats up twice as weakly as soil. On cooling, the ratio is reversed. If a cold air mass penetrates a warm ocean surface, then heat penetrates into a layer up to 5 km. The heating of the troposphere is due to the latent heat of vaporization.
Turbulent mixing of air (random, uneven, chaotic) creates convection currents, the intensity and direction of which depend on the nature of the terrain and the planetary circulation of air masses.
The concept of an adiabatic process. An important role in the thermal regime of air belongs to the adiabatic process.
The concept of an adiabatic process. The most important role in the thermal regime of the atmosphere belongs to the adiabatic process. Adiabatic heating and cooling of air occurs in the same mass, without heat exchange with other media.
When air descends from the upper or middle layers of the troposphere or along the slopes of mountains, it enters denser layers from rarefied layers, gas molecules approach each other, their collisions intensify, and the kinetic energy of the movement of air molecules turns into heat. The air is heated without receiving heat either from other air masses or from the earth's surface. Adiabatic heating occurs, for example, in the tropical zone, over deserts and over oceans in the same latitudes. Adiabatic heating of air is accompanied by its drying (which is main reason formation of deserts in the tropics).
In ascending currents, the air cools adiabatically. From the dense lower troposphere, it rises to the rarefied middle and upper troposphere. At the same time, its density decreases, the molecules move away from each other, collide less often, the thermal energy received by air from the heated surface turns into kinetic energy, is spent on mechanical work to expand the gas. This explains the cooling of the air as it rises.
Dry air cools adiabatically by 1 0 C per 100 m of elevation, this is an adiabatic process. However, natural air contains water vapor, which condenses to release heat. Therefore, in fact, the temperature drops by 0.6 0 C per 100 m (or 6 0 C per 1 km of altitude). This is a wet adiabatic process.
When lowering, both dry and moist air heat up equally, since in this case moisture condensation does not occur and the latent heat of vaporization is not released.
The most clearly typical features of the thermal regime of the land are manifested in deserts: a large proportion of solar radiation is reflected from their bright surface, heat is not spent on evaporation, and goes to heat dry rocks. From them during the day the air is heated to high temperatures. In dry air, heat does not linger and is freely radiated into the upper atmosphere and interplanetary space. Deserts also serve as cooling windows for the atmosphere on a planetary scale.
The source of heat and light energy for the Earth is solar radiation. Its value depends on the latitude of the place, since the angle of incidence of the sun's rays decreases from the equator to the poles. The smaller the angle of incidence of the sun's rays, the large surface a beam of solar rays of the same cross section is distributed, and therefore there is less energy per unit area.
Due to the fact that during the year the Earth makes 1 revolution around the Sun, moving, maintaining a constant angle of inclination of its axis to the plane of the orbit (ecliptic), seasons of the year appear, characterized by different surface heating conditions.
On March 21 and September 23, the Sun is at its zenith under the equator (equinoxes). On June 22, the Sun is at its zenith over the Northern Tropic, on December 22 - over the Southern. Light zones and thermal zones are distinguished on the earth's surface (according to the average annual isotherm + 20 ° C, the boundary of the warm (hot) zone passes; between the average annual isotherms + 20 ° C and the isotherm + 10 ° C there is a temperate zone; according to the isotherm + 10 ° C - the boundaries cold belt.
The sun's rays pass through the transparent atmosphere without heating it, they reach the earth's surface, heat it, and from it, due to long-wave radiation, the air is heated. The degree of heating of the surface, and hence the air, depends primarily on the latitude of the area, as well as on 1) height above sea level (as it rises, the air temperature decreases by an average of 0.6ºС per 100 m; 2) features of the underlying surface which can be different in color and have different albedo - the reflective ability of rocks. Also different surfaces have different heat capacity and heat dissipation. Water, due to its high heat capacity, heats up slowly and slowly, while land is vice versa. 3) from the coasts to the depths of the continents, the amount of water vapor in the air decreases, and the more transparent the atmosphere, the less sunlight is scattered in it by water drops, and more sunlight reaches the Earth's surface.
The totality of solar matter and energy entering the earth is called solar radiation. It is divided into direct and scattered. direct radiation- a set of direct sunlight penetrating the atmosphere with a cloudless sky. scattered radiation- part of the radiation scattered in the atmosphere, while the rays go in all directions. P + P = Total radiation. Part of the total radiation reflected from the Earth's surface is called reflected radiation. Part of the total radiation absorbed by the Earth's surface is absorbed radiation. Thermal energy moving from the heated atmosphere to the surface of the Earth, towards the flow of heat from the Earth is called the counter radiation of the atmosphere.
Annual amount of total solar radiation in kcal/cm 2 year (according to T.V. Vlasova).
Effective Radiation- a value expressing the actual transfer of heat from the Earth's surface to the atmosphere. The difference between the radiation of the Earth and the counter radiation of the atmosphere determines the heating of the surface. Radiation balance directly depends on effective radiation - the result of the interaction of two processes of arrival and consumption of solar radiation. The amount of balance is largely affected by cloudiness. Where it is significant at night, it intercepts the long-wave radiation of the Earth, preventing it from escaping into space.
The temperature of the underlying surface and surface layers of air and the heat balance directly depend on the influx of solar radiation.
The heat balance determines the temperature, its magnitude and change on the surface that is directly heated by the sun's rays. When heated, this surface transfers heat (in the long-wave range) both to the underlying layers and to the atmosphere. The surface itself is called the active surface.
Main components heat balance atmosphere and surface of the earth as a whole
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Energy coming to the Earth's surface from the Sun |
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Radiation reflected by the atmosphere into interplanetary space, including 1) reflected by clouds 2) dissipates |
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Radiation absorbed by the atmosphere, including: 1) absorbed by clouds 2) absorbed by ozone 3) absorbed by water vapor |
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Radiation reaching the underlying surface (direct + diffuse) |
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From it: 1) is reflected by the underlying surface outside the atmosphere 2) is absorbed by the underlying surface. |
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From it: 1) effective radiation 2) turbulent heat exchange with the atmosphere 3) heat consumption for evaporation |
In the diurnal course of surface temperature, dry and devoid of vegetation, on a clear day, the maximum occurs after 14:00, and the minimum occurs around the time of sunrise. Cloudiness, humidity and surface vegetation can disrupt the daily course of temperature.
Daytime maxima of land surface temperature can be +80 o C or more. Daily fluctuations reach 40 o. The values of extreme values and temperature amplitudes depend on the latitude of the place, season, cloudiness, thermal properties of the surface, its color, roughness, nature of the vegetation cover, slope orientation (exposure).
When heated, the surface transfers heat to the soil. Time is spent on the transfer of heat from layer to layer, and the moments of the onset of maximum and minimum temperature values during the day are delayed by every 10 cm by about 3 hours. The deeper the layer, the less heat it receives and the weaker the temperature fluctuations in it. At an average depth of about 1 m, the daily fluctuations in soil temperature "fade out". The layer in which they stop is called the layer of constant daily temperature.
At a depth of 5-10 m in tropical latitudes and 25 m in high latitudes, there is a layer of constant annual temperature, where the temperature is close to the average annual air temperature above the surface.
Water heats up more slowly and releases heat more slowly. In addition, the sun's rays can penetrate to great depths, directly heating the deeper layers. The transfer of heat to depth is not so much due to molecular thermal conductivity, but to a greater extent due to the mixing of waters in a turbulent way or currents. When the surface layers of water cool, thermal convection occurs, which is also accompanied by mixing.
Unlike land, the diurnal temperature fluctuations on the surface of the ocean are less. In high latitudes, on average, only 0.1ºС, in temperate - 0.4ºС, in tropical - 0.5ºС. The penetration depth of these oscillations is 15-20 m.
Annual temperature amplitudes on the ocean surface from 1ºС in equatorial latitudes to 10.2ºС in temperate latitudes. Annual temperature fluctuations penetrate to a depth of 200-300 m.
The moments of temperature maxima in water bodies are delayed compared to land. The maximum occurs at about 15-16 hours, the minimum - 2-3 hours after sunrise. The annual maximum temperature on the surface of the ocean in the northern hemisphere occurs in August, the minimum - in February.
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 long time should be balanced.
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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The earth's surface, absorbing solar radiation and heating up, itself becomes a source of heat radiation into the atmosphere and through it into the world space. The higher the surface temperature, the higher the radiation. The Earth's own long-wave radiation is mostly retained in the troposphere, which heats up and emits radiation - atmospheric counter-radiation. The difference between the radiation of the earth's surface and the counter-radiation of the atmosphere is called efficient radiation. It shows the actual loss of heat by the Earth's surface and is about 20%.
Rice. 7.2. Scheme of the average annual radiation and heat balance, (according to K.Ya.Kondratiev, 1992)
The atmosphere, unlike the earth's surface, radiates more than it absorbs. The energy deficit is compensated by the arrival of heat from the earth's surface along with water vapor, as well as due to turbulence (during the rise of air heated near the earth's surface). The temperature contrasts that arise between low and high latitudes are smoothed out due to advection - heat transfer by marine and mainly air currents from low latitudes to high latitudes (Fig. 7.2, right side). For general geographical conclusions, rhythmic fluctuations in radiation due to the change of seasons are also important, since the thermal regime of a particular area depends on this. The reflective properties of earth covers, the heat capacity and thermal conductivity of media further complicate the transfer of thermal energy and the distribution of thermal energy characteristics.
Heat balance equation. The amount of heat is described by the heat balance equation, which is different for each geographical area. Its most important component is the radiation balance of the earth's surface. Solar radiation is spent on heating the soil and air (and water), evaporation, melting snow and ice, photosynthesis, soil formation processes and weathering of rocks. Since equilibrium is always characteristic of nature, equality is observed between the arrival of energy and its consumption, which is expressed heat balance equation earth surface:
where R- radiation balance; LE is the heat used to evaporate water and melt snow or ice (L- latent heat of evaporation or vaporization; E- the rate of evaporation or condensation); BUT - horizontal heat transfer by air and ocean currents or turbulent flow; R - heat exchange of the earth's surface with air; AT - heat exchange of the earth's surface with soil and rocks; F- energy consumption for photosynthesis; FROM- energy consumption for soil formation and weathering; Q+q- total radiation; a- albedo; I- effective radiation of the atmosphere.
The share of energy spent on photosynthesis and soil formation accounts for less than 1% of the radiation budget, so these components are often omitted from the equation. However, in reality, they can matter, since this energy has the ability to accumulate and transform into other forms (convertible energy). A low-power, but long-term (hundreds of millions of years) process of accumulating convertible energy had a significant impact on the geographic envelope. About 11 × 10 14 J / m 2 of energy accumulated in it in scattered organic matter in sedimentary rocks, as well as in the form hard coal, oil, shale.
The heat balance equation can be derived for any geographic area and time interval, taking into account the specificity of climatic conditions and the contribution of components (for land, ocean, areas with ice formation, non-freezing, etc.).
Transfer and distribution of heat. The transfer of heat from the surface to the atmosphere occurs in three ways: thermal radiation, heating or cooling of air upon contact with land, and evaporation of water. Water vapor, rising into the atmosphere, condenses and forms clouds or falls out as precipitation, and the heat released in this case enters the atmosphere. The radiation absorbed by the atmosphere and the heat of condensation of water vapor delay the loss of heat from the earth's surface. Over arid regions, this influence decreases, and we observe the largest daily and annual temperature amplitudes. The smallest temperature amplitudes are inherent in oceanic regions. As a huge reservoir, the ocean stores more heat, which reduces annual temperature fluctuations due to high temperatures. specific heat water. Thus, on Earth, water plays an important role as a heat accumulator.
The structure of the heat balance depends on the geographic latitude and the type of landscape, which, in turn, itself depends on it. It changes significantly not only when moving from the equator to the poles, but also when moving from land to sea. Land and ocean differ both in the amount of absorbed radiation and in the nature of the distribution of heat. In the ocean in summer, heat spreads to a depth of several hundred meters. During the warm season, the ocean accumulates from 1.3×10 9 to 2.5×10 9 J/m 2 . On land, heat spreads to a depth of only a few meters, and during the warm season about 0.1 × 10 9 J/m 2 accumulates here, which is 10-25 times less than in the ocean. Due to the large supply of heat, the ocean cools less in winter than the land. Calculations show that the one-time heat content in the ocean is 21 times greater than its supply to the earth's surface as a whole. Even in the 4 meter layer ocean water heat is 4 times greater than in the entire atmosphere.
Up to 80% of the energy absorbed by the ocean is used to evaporate water. This is 12×10 23 J/m 2 per year, which is 7 times more than the same article of the land heat balance. 20% of the energy is spent on turbulent heat exchange with the atmosphere (which is also more than on land). The vertical heat exchange of the ocean with the atmosphere also stimulates the horizontal transfer of heat, due to which it partially ends up on land. A 50-meter layer of water participates in the heat exchange between the ocean and the atmosphere.
Changes in radiation and heat balance. The annual sum of the radiation balance is positive almost everywhere on Earth, with the exception of the glacial regions of Greenland and Antarctica. Its average annual values decrease in the direction from the equator to the poles, following the patterns of distribution of solar radiation over the globe (Fig. 7.3). The radiation balance over the ocean is greater than over land. This is due to the lower albedo water surface, increased moisture content in equatorial and tropical latitudes. Seasonal changes in the radiation balance occur at all latitudes, but with varying degrees of severity. At low latitudes, seasonality is determined by the precipitation regime, since thermal conditions change little here. In temperate and high latitudes, seasonality is determined by the thermal regime: the radiation balance changes from positive in summer to negative in winter. The negative balance of the cold period of the year in temperate and polar latitudes is partially compensated for by advection of heat by air and sea currents from low latitudes.
To maintain the energy balance of the Earth, there must be a transfer of heat towards the poles. A little less of this heat is carried by ocean currents, the rest by the atmosphere. Differences in the heating of the Earth determine its action as a geographic heat engine in which heat is transferred from the heater to the refrigerator. In nature, this process is realized in two forms: firstly, thermodynamic spatial inhomogeneities form planetary systems of winds and sea currents; secondly, these planetary systems themselves participate in the redistribution of heat and moisture to the globe. Thus, heat is transferred from the equator towards the poles by air currents or ocean currents, and cold air or water masses are transferred to the equator. On fig. Figure 7.4 shows the poleward transport of warm surface water in the Atlantic Ocean. The heat transfer towards the poles reaches a maximum near a latitude of 40° and becomes zero at the poles.
The influx of solar radiation depends not only on the geographic latitude, but also on the season (Table 7.4). It is noteworthy that in summer even more heat enters the Arctic than at the equator, however, due to the high albedo of the Arctic seas, ice does not melt here.
Temperature distribution. On the horizontal distribution temperatures affect geographical position, relief, properties and material composition of the underlying surface, systems of ocean currents and the nature of atmospheric circulation in the surface and near-surface layers.
Rice. 7.3. Distribution of the average annual radiation balance on the earth's surface, MJ / (m 2 × year) (according to S.P. Khromov and M.A. Petrosyants, 1994)
Rice. 7.4. Heat transfer in the northern part Atlantic Ocean, °С(according to S. Neshiba, 1991). Shaded areas are areas where surface water is warmer than the ocean average. The numbers indicate the volumetric water transfers (million m 3 / s), the arrows indicate the direction of the currents, the thick line indicates the Gulf Stream
Table 7.4. Total radiation entering the earth's surface (N.I. Egorov, 1966)