Total direct scattered absorbed solar radiation. Measurement of solar radiation

The number of incoming earth's surface direct solar radiation (S) in a cloudless sky depends on the height of the sun and transparency. Table for three latitude zones the distribution of monthly amounts of direct radiation is given for cloudless sky(possible sums) as averages for the central months of the seasons and the year.

The increased arrival of direct radiation in the Asian part is due to the higher transparency of the atmosphere in this region. High values direct radiation in the summer in the northern regions of Russia are explained by a combination of high transparency of the atmosphere and long duration days

Reduces the arrival of direct radiation and can significantly change its daily and annual course. However, under average cloudiness conditions, the astronomical factor is predominant and, therefore, the maximum direct radiation is observed at highest altitude sun.

In most of the continental regions of Russia in the spring-summer months, direct radiation in the pre-noon hours is greater than in the afternoon. This is due to the development of convective cloudiness in the afternoon hours and a decrease in the transparency of the atmosphere at this time of the day compared to the morning hours. In winter, the ratio of pre- and afternoon radiation values ​​is reversed - the pre-noon values ​​of direct radiation are less due to the morning maximum cloudiness and its decrease in the second half of the day. The difference between pre- and afternoon values ​​of direct radiation can reach 25–35%.

In the annual course, the maximum direct radiation falls on June-July, with the exception of areas Far East, where it shifts to May, and in the south of Primorye a secondary maximum is noted in September.
The maximum monthly amount of direct radiation on the territory of Russia is 45–65% of what is possible under a cloudless sky, and even in the south of the European part it reaches only 70%. The minimum values ​​are observed in December and January.

The contribution of direct radiation to the total arrival under actual cloudiness reaches a maximum in the summer months and averages 50–60%. The exception is Primorsky Krai, where the largest contribution of direct radiation falls on the autumn and winter months.

The distribution of direct radiation under average (actual) cloudiness over the territory of Russia largely depends on . This leads to a noticeable violation of the zonal distribution of radiation in certain months. This is especially evident in the spring. So, in April there are two maximums - one in the southern regions

The energy emitted by the Sun is called solar radiation. Coming to earth solar radiation most of it is converted into heat.

Solar radiation is practically the only source of energy for the Earth and the atmosphere. Compared to solar energy, the importance of other energy sources for the Earth is negligible. For example, the temperature of the Earth, on average, increases with depth (about 1 ° C for every 35 m). Due to this, the surface of the Earth receives some heat from the internal parts. It is estimated that on average 1 cm 2 of the earth's surface receives about 220 J per year from the inner parts of the Earth. This amount is 5000 times less than the heat received from the Sun. The Earth receives a certain amount of heat from stars and planets, but even it is many times (approximately 30 million) less than the heat coming from the Sun.

The amount of energy sent by the Sun to the Earth is enormous. Thus, the power of the solar radiation flux entering an area of ​​10 km 2 is 7-9 kW in a cloudless summer (taking into account the weakening of the atmosphere). It's more than power Krasnoyarsk HPP. The amount of radiant energy coming from the Sun in 1 second to an area of ​​15x15 km (this is less area Leningrad) at around noon hours in the summer, exceeds the capacity of all power plants of the collapsed USSR (166 million kW).

Figure 1 - The sun is a source of radiation

Types of solar radiation

In the atmosphere, solar radiation on its way to the earth's surface is partially absorbed, and partially scattered and reflected from clouds and the earth's surface. Three types of solar radiation are observed in the atmosphere: direct, diffuse and total.

direct solar radiation- radiation coming to the earth's surface directly from the solar disk. Solar radiation propagates from the Sun in all directions. But the distance from the Earth to the Sun is so great that direct radiation falls on any surface on the Earth in the form of a beam of parallel rays emanating, as it were, from infinity. Even the whole Earth in general, it is so small in comparison with the distance to the Sun that all solar radiation falling on it can be considered a beam of parallel rays without appreciable error.

Only direct radiation reaches the upper boundary of the atmosphere. About 30% of the radiation incident on the Earth is reflected into outer space. Oxygen, nitrogen, ozone, carbon dioxide, water vapor (clouds) and aerosol particles absorb 23% of direct solar radiation in the atmosphere. Ozone absorbs ultraviolet and visible radiation. Despite the fact that its content in the air is very small, it absorbs all the ultraviolet radiation (about 3%). Thus, it is not observed at all near the earth's surface, which is very important for life on Earth.

Direct solar radiation on its way through the atmosphere is also scattered. A particle (drop, crystal or molecule) of air, which is in the path of an electromagnetic wave, continuously “extracts” energy from the incident wave and re-radiates it in all directions, becoming an energy emitter.

About 25% of the energy of the total solar radiation flux passing through the atmosphere is scattered by molecules atmospheric gases and aerosol and turns into diffuse solar radiation in the atmosphere. Thus scattered solar radiation- solar radiation that has undergone scattering in the atmosphere. Scattered radiation comes to the earth's surface not from the solar disk, but from everything vault of heaven. Scattered radiation is different from direct radiation spectral composition because rays of different wavelengths scatter to different degrees.

Since the original source scattered radiation is direct solar radiation, the flux of diffuse depends on the same factors that affect the flux of direct radiation. In particular, the flux of scattered radiation increases with the increase in the height of the Sun and vice versa. It also increases with an increase in the number of scattering particles in the atmosphere, i.e. with a decrease in the transparency of the atmosphere, and decreases with height above sea level due to a decrease in the number of scattering particles in the overlying layers of the atmosphere. Cloudiness and snow cover have a very great influence on diffuse radiation, which, due to the scattering and reflection of the direct and diffuse radiation incident on them and their re-scattering in the atmosphere, can increase the diffuse solar radiation by several times.

Scattered radiation significantly supplements direct solar radiation and significantly increases the incoming solar energy to the earth's surface. Its role is especially important in winter time at high latitudes and in other areas with high cloudiness, where the proportion of diffuse radiation may exceed the proportion of direct radiation. For example, in the annual amount of solar energy, scattered radiation accounts for 56% in Arkhangelsk and 51% in St. Petersburg.

Total solar radiation is the sum of the fluxes of direct and diffuse radiation arriving on a horizontal surface. Before sunrise and after sunset, as well as in the daytime with continuous cloudiness, the total radiation is completely, and at low altitudes of the Sun it mainly consists of scattered radiation. In a cloudless or slightly cloudy sky, with an increase in the height of the Sun, the proportion of direct radiation in the composition of the total rapidly increases and in the daytime its flux is many times greater than the flux of scattered radiation. Cloudiness on average weakens the total radiation (by 20-30%), however, with partial cloudiness that does not cover the solar disk, its flux may be greater than with a cloudless sky. The snow cover significantly increases the flux of total radiation by increasing the flux of scattered radiation.

Total radiation falling on the earth's surface, for the most part absorbed by the top layer of soil or a thicker layer of water (absorbed radiation) and converted into heat, and partly reflected (reflected radiation).

The sun is the source of corpuscular and electromagnetic radiation. Corpuscular radiation does not penetrate the atmosphere below 90 km, while electromagnetic radiation reaches the earth's surface. In meteorology it is called solar radiation or simply radiation. It is one two-billionth of the total energy of the Sun and travels from the Sun to the Earth in 8.3 minutes. Solar radiation is the source of energy for almost all processes occurring in the atmosphere and on the earth's surface. It is mainly shortwave and consists of invisible ultraviolet radiation - 9%, visible light - 47% and invisible infrared - 44%. Since almost half of the solar radiation is visible light, the Sun is a source of not only heat, but also light - too. necessary condition for life on earth.

Radiation coming to Earth directly from the solar disk is called direct solar radiation. Due to the fact that the distance from the Sun to the Earth is large, and the Earth is small, radiation falls on any of its surfaces in the form of a beam of parallel rays.

Solar radiation has a certain flux density per unit area per unit time. The unit of measurement of radiation intensity is the amount of energy (in joules or calories 1) that 1 cm 2 of the surface per minute receives when the sun's rays fall perpendicularly. At the upper boundary of the atmosphere, at an average distance from the Earth to the Sun, it is 8.3 J / cm 2 per minute, or 1.98 cal / cm 2 per minute. This value is accepted as an international standard and is called solar constant(S0). Her periodic fluctuations during the year are insignificant (+ 3.3%) and are due to a change in the distance from the Earth to

1 1 cal = 4.19 J, 1 kcal = 41.9 MJ.

2 The noon altitude of the Sun depends on the geographic latitude and declination of the Sun.

Sun. Non-periodic fluctuations are caused by different emissivity of the Sun. The climate at the top of the atmosphere is called radiation or solar. It is calculated theoretically, based on the angle of inclination of the sun's rays on a horizontal surface.

AT in general terms the solar climate is reflected on the earth's surface. At the same time, the real radiation and temperature on Earth differ significantly from the solar climate due to various terrestrial factors. The main one is the attenuation of radiation in the atmosphere due to reflections, absorptions and scattering, and also as a result reflections of radiation from the earth's surface.

At the top of the atmosphere, all radiation comes in the form of direct radiation. According to S. P. Khromov and M. A. Petrosyants, 21% of it is reflected from clouds and air back into outer space. The rest of the radiation enters the atmosphere, where direct radiation is partially absorbed and scattered. Remaining direct radiation(24%) reaches the earth's surface, however, it is weakened. The patterns of its weakening in the atmosphere are expressed by Bouguer's law: S=S 0 pm(J, or cal / cm 2, per min), where S is the amount of direct solar radiation that has reached the earth's surface, per unit area (cm 2) located perpendicular to the sun's rays, S 0 is the solar constant, R- coefficient of transparency in fractions of unity, showing what part of the radiation reached the earth's surface, t is the path length of the beam in the atmosphere.

Really Sun rays fall on the earth's surface and on any other level of the atmosphere at an angle of less than 90°. The flow of direct solar radiation onto a horizontal surface is called insolation(5,). It is calculated by the formula S 1 \u003d S sin h ☼ (J, or cal / cm 2, per minute), where h ☼ is the height of the Sun 2. Naturally, there is a smaller amount per unit of horizontal surface

energy than per unit area located perpendicular to the sun's rays (Fig. 22).

In the atmosphere absorbed about 23% and dissipates about 32% of the direct solar radiation entering the atmosphere, with 26% of the scattered radiation then coming to the earth's surface, and 6% going into space.

Solar radiation undergoes not only quantitative but also qualitative changes in the atmosphere, since air gases and aerosols absorb and scatter solar rays selectively. The main absorbers of radiation are water vapor, clouds and aerosols, as well as ozone, which strongly absorbs ultraviolet radiation. Molecules of various gases and aerosols participate in the scattering of radiation. Scattering- deflection of light rays in all directions from the original direction, so that scattered radiation comes to the earth's surface not from the solar disk, but from the entire firmament. Scattering depends on the wavelength: according to Rayleigh's law, the shorter the wavelength, the more intense the scattering. Therefore, ultraviolet rays are scattered most of all, and of the visible ones, violet and blue. Hence the blue color of the air and, accordingly, the sky in clear weather. Direct radiation, on the other hand, turns out to be mostly yellow, so the solar disk appears yellowish. At sunrise and sunset, when the path of the beam in the atmosphere is longer and the scattering is greater, only red rays reach the surface, which makes the Sun appear red. Scattered radiation causes light in the daytime in cloudy weather and in the shade in clear weather; the phenomenon of twilight and white nights is associated with it. On the Moon, where there is no atmosphere and, accordingly, scattered radiation, objects that fall into the shadow become completely invisible.

With height, as the density of air decreases and, accordingly, the number of scattering particles, the color of the sky becomes darker, first turning into deep blue, then into blue-violet, which is clearly visible in the mountains and reflected in the Himalayan landscapes of N. Roerich. In the stratosphere, the color of the air is black and purple. Astronauts testify that at an altitude of 300 km the color of the sky is black.

In the presence of large aerosols, droplets and crystals in the atmosphere, it is no longer scattering, but diffuse reflection, and since diffusely reflected radiation is White light, then the color of the sky becomes whitish.

Direct and diffuse solar radiation have a certain daily and annual course, which depends primarily on the height of the Sun.

Rice. 22. The influx of solar radiation on the surface AB, perpendicular to the rays, and on the horizontal surface AC (according to S. P. Khromov)

above the horizon, from the transparency of the air and cloudiness.

The flux of direct radiation in during the day increases from sunrise to noon and then decreases until sunset due to a change in the height of the Sun and the path of the beam in the atmosphere. However, since the transparency of the atmosphere decreases around noon due to an increase in water vapor in the air and dust, and convective cloudiness increases, the maximum values ​​of radiation are shifted to the pre-noon hours. This pattern is inherent in equatorial-tropical latitudes all year round, and in temperate latitudes in summer. In winter, in temperate latitudes, the maximum radiation occurs at noon.

annual course Monthly average direct radiation values ​​depend on latitude. At the equator, the annual course of direct radiation has the form of a double wave: maxima during the periods of the spring and autumn equinoxes, minima during the periods of summer and winter solstice. In temperate latitudes, the maximum values ​​of direct radiation occur in spring (April in the northern hemisphere), and not in the summer months, since the air at this time is more transparent due to the lower content of water vapor and dust, as well as slight cloudiness. The radiation minimum is observed in December, when smallest height Sun, short daylight hours, and this is the most cloudy month of the year.

Daily and annual course of scattered radiation is determined by the change in the height of the Sun above the horizon and the length of the day, as well as the transparency of the atmosphere. The maximum of scattered radiation during the day is observed during the day with an increase in radiation in general, although its share in the morning and evening hours more than direct, and during the day, on the contrary, direct radiation prevails over diffuse. The annual course of scattered radiation at the equator generally repeats the course of a straight line. In other latitudes, more in summer than in winter, due to an increase in the total influx of solar radiation in summer.

The ratio between direct and scattered radiation varies depending on the height of the Sun, the transparency of the atmosphere and cloudiness.

Proportions between direct and diffuse radiation on different latitudes are not the same. In the polar and subpolar regions, scattered radiation makes up 70% of the total radiation flux. Its value, in addition to the low position of the Sun and cloudiness, is also affected by multiple reflections of solar radiation from the snow surface. Starting from temperate latitudes and almost to the equator, direct radiation prevails over scattered radiation. Its absolute and relative importance is especially great in the inland tropical deserts (Sahara, Arabia), characterized by minimal cloudiness and clear dry air. Along the equator, scattered radiation again dominates over the straight line due to the high humidity of the air and the presence of cumulus clouds that scatter solar radiation well.

With an increase in the height of the place above sea level, the absolute value increases significantly. 23. Annual amount of total solar radiation [MJ / (m 2 x year)]

naya and relative magnitude direct radiation and diffused radiation decreases, as the layer of the atmosphere becomes thinner. At an altitude of 50-60 km, the direct radiation flux approaches the solar constant.

All solar radiation - direct and diffuse, coming to the earth's surface, is called total radiation: (Q=S· sinh¤+D where Q is total radiation, S is direct, D is diffuse, h ¤ is the height of the Sun above the horizon. The total radiation is about 50% of the solar radiation arriving at the upper boundary of the atmosphere.

With a cloudless sky, the total radiation is significant and has a daily variation with a maximum around noon and an annual variation with a maximum in summer. Cloudiness reduces radiation, so in summer its arrival in the pre-noon hours is on average greater than in the afternoon. For the same reason, it is larger in the first half of the year than in the second.

A number of regularities are observed in the distribution of total radiation on the earth's surface.

Main regularity is that the total radiation is distributed zonal, descending from the equatorial tropi-

ic latitudes to the poles in accordance with the decrease in the angle of incidence of the sun's rays (Fig. 23). Deviations from the zonal distribution are explained by different cloudiness and transparency of the atmosphere. The highest annual values ​​of total radiation 7200 - 7500 MJ / m 2 per year (about 200 kcal / cm 2 per year) fall on tropical latitudes, where there is little cloudiness and low air humidity. In the inland tropical deserts (Sahara, Arabia), where there is an abundance of direct radiation and almost no clouds, the total solar radiation even reaches more than 8000 MJ/m 2 per year (up to 220 kcal/cm 2 per year). Near the equator, the total radiation decreases to 5600 - 6500 MJ / m per year (140-160 kcal / cm 2 per year) due to significant cloudiness, high humidity and less air transparency. In temperate latitudes, the total radiation is 5000 - 3500 MJ / m 2 per year (≈ 120 - 80 kcal / cm 2 per year), in the polar regions - 2500 MJ / m per year (≈60 kcal / cm 2 per year). Moreover, in Antarctica it is 1.5-2 times greater than in the Arctic, primarily due to the greater absolute height of the continent (more than 3 km) and therefore the low density of air, its dryness and transparency, as well as partly cloudy weather. The zonality of the total radiation is better expressed over the oceans than over the continents.

The second important pattern total radiation is that the continents receive it more than the oceans, due to less (15-30%) cloudiness over

continents. The only exceptions are equatorial latitudes, since during the day the convective cloudiness over the ocean is less than over land.

Third feature is that in the northern, more continental hemisphere, the total radiation is generally greater than in the southern oceanic.

In June, the largest monthly amounts of solar radiation are received by the northern hemisphere, especially the inland tropical and subtropical regions. In temperate and polar latitudes, the amount of radiation varies slightly across latitudes, since the decrease in the angle of incidence of the rays is compensated by the duration of sunshine, up to polar day beyond the Arctic Circle. In the southern hemisphere, with increasing latitude, radiation rapidly decreases and is zero beyond the Antarctic Circle.

December Southern Hemisphere receives more radiation than the north. At this time, the largest monthly amounts solar heat occur in the deserts of Australia and the Kalahari; further in temperate latitudes, the radiation gradually decreases, but in Antarctica it increases again and reaches the same values ​​as in the tropics. In the northern hemisphere, with increasing latitude, it rapidly decreases and is absent beyond the Arctic Circle.

In general, the largest annual amplitude of the total radiation is observed beyond the polar circles, especially in Antarctica, the smallest - in the equatorial zone.

Solar radiation (solar radiation) is the totality of solar matter and energy coming to the Earth. Solar radiation consists of the following two main parts: firstly, thermal and light radiation, which is a combination electromagnetic waves; secondly, corpuscular radiation.

In the sun thermal energy nuclear reactions turns into radiant energy. When the sun's rays fall on the earth's surface, radiant energy is again converted into thermal energy. Solar radiation thus carries light and heat.

Intensity of solar radiation. solar constant. Solar radiation is the most important source of heat for geographical envelope. The second source of heat for the geographic shell is the heat coming from the inner spheres and layers of our planet.

Due to the fact that in the geographical envelope there is one type of energy ( radiant energy ) is equivalent to another form ( thermal energy ), then the radiant energy of solar radiation can be expressed in units of thermal energy - joules (J).

The intensity of solar radiation must be measured primarily outside the atmosphere, because when passing through the air sphere, it is transformed and weakens. The intensity of solar radiation is expressed by the solar constant.

solar constant - this is the flow of solar energy in 1 minute to an area with a cross section of 1 cm 2, perpendicular to the sun's rays and located outside the atmosphere. The solar constant can also be defined as the amount of heat that is received in 1 minute at the upper boundary of the atmosphere by 1 cm 2 of a black surface perpendicular to the sun's rays.

The solar constant is 1.98 cal / (cm 2 x min), or 1.352 kW / m 2 x min.

Since the upper atmosphere absorbs a significant part of the radiation, it is important to know its value at the upper boundary of the geographic envelope, i.e., in the lower stratosphere. Solar radiation at the upper boundary of the geographic shell is expressed conditional solar constant . The value of the conditional solar constant is 1.90 - 1.92 cal / (cm 2 x min), or 1.32 - 1.34 kW / (m 2 x min).

The solar constant, contrary to its name, does not remain constant. It changes due to the change in the distance from the Sun to the Earth as the Earth moves in its orbit. No matter how small these fluctuations are, they always affect the weather and climate.

On average each square kilometer the troposphere receives 10.8 x 10 15 J. (2.6 x 10 15 cal) per year. This amount of heat can be obtained by burning 400,000 tons hard coal. The whole Earth in a year receives such an amount of heat, which is determined by the value of 5.74 x 10 24 J. (1.37 x 10 24 cal).

The distribution of solar radiation "at the upper boundary of the atmosphere" or with an absolutely transparent atmosphere. Knowledge of the distribution of solar radiation prior to its entry into the atmosphere, or the so-called solar (solar) climate , is important for determining the role and share of participation of the air shell Earth (atmosphere) in the distribution of heat over the earth's surface and in the formation of its thermal regime.

The amount of solar heat and light entering per unit area is determined, firstly, by the angle of incidence of the rays, which depends on the height of the Sun above the horizon, and secondly, by the length of the day.

The distribution of radiation near the upper boundary of the geographic envelope, determined only by astronomical factors, is more even than its actual distribution near the earth's surface.

In the absence of an atmosphere, the annual sum of radiation at equatorial latitudes would be 13,480 MJ/cm 2 (322 kcal/cm 2), and at the poles 5,560 MJ/m 2 (133 kcal/cm 2). In the polar latitudes, the Sun sends heat a little less than half (about 42%) of the amount that enters the equator.

It would seem that the solar irradiation of the Earth is symmetrical with respect to the plane of the equator. But this happens only twice a year, on the days of the spring and autumn equinoxes. The inclination of the axis of rotation and the annual motion of the Earth determine its asymmetric irradiation by the Sun. In the January part of the year, the southern hemisphere receives more heat, in July - the northern one. This is precisely what main reason seasonal rhythms in a geographical envelope.

The difference between the equator and the pole of the summer hemisphere is small: 6,740 MJ/m 2 (161 kcal/cm 2) arrive at the equator, and about 5,560 MJ/m 2 (133 kcal/cm 2 per half year) arrive at the pole. But the polar countries of the winter hemisphere at the same time are completely devoid of solar heat and light.

On the day of the solstice, the pole receives even more heat than the equator - 46.0 MJ / m 2 (1.1 kcal / cm 2) and 33.9 MJ / m 2 (0.81 kcal / cm 2).

In general, the annual solar climate at the poles is 2.4 times colder than at the equator. However, it must be borne in mind that in winter the poles are not heated by the Sun at all.

The real climate of all latitudes is largely due to terrestrial factors. The most important of these factors are: firstly, the weakening of radiation in the atmosphere, and secondly, the different intensity of assimilation of solar radiation by the earth's surface in different geographical conditions.

The change in solar radiation as it passes through the atmosphere. Direct sunlight penetrating the atmosphere when the sky is cloudless is called direct solar radiation . Its maximum value at high transparency of the atmosphere on a surface perpendicular to the rays in tropical zone is about 1.05 - 1.19 kW / m 2 (1.5 - 1.7 cal / cm 2 x min. In the middle latitudes, the voltage of midday radiation is usually about 0.70 - 0.98 kW / m 2 x min (1.0 - 1.4 cal/cm 2 x min) In the mountains, this value increases significantly.

Part of the sun's rays from contact with gas molecules and aerosols are scattered and converted into scattered radiation . On the earth's surface, scattered radiation no longer comes from the solar disk, but from the entire sky and creates widespread daylight illumination. From her to sunny days light and where direct rays do not penetrate, for example, under the canopy of the forest. In addition to direct radiation, diffuse radiation also serves as a source of heat and light.

Absolute value scattered radiation is greater, the more intense the direct line. Relative value scattered radiation increases with a decrease in the role of the direct line: in the middle latitudes in summer it is 41%, and in winter 73% of the total radiation arrival. Specific gravity scattered radiation in total value total radiation also depends on the height of the sun. In high latitudes, scattered radiation accounts for about 30%, and in polar latitudes, approximately 70% of all radiation.

In general, diffuse radiation accounts for about 25% of the total solar radiation that reaches our planet.

Thus, direct and diffuse radiation enters the earth's surface. Together, direct and diffuse radiation form total radiation , which defines thermal regime of the troposphere .

By absorbing and scattering radiation, the atmosphere significantly weakens it. Attenuation amount depends on transparency coefficient, showing how much radiation reaches the earth's surface. If the troposphere consisted only of gases, then the transparency coefficient would be equal to 0.9, i.e., it would pass about 90% of the radiation going to the Earth. However, aerosols are always present in the air, reducing the transparency coefficient to 0.7 - 0.8. The transparency of the atmosphere changes as the weather changes.

Since the air density decreases with height, the layer of gas penetrated by the rays should not be expressed in km of atmospheric thickness. The unit of measurement is optical mass, equal to the thickness of the air layer with vertical incidence of rays.

The weakening of radiation in the troposphere is easy to observe during the day. When the Sun is near the horizon, its rays penetrate several optical masses. At the same time, their intensity is so weakened that one can look at the Sun with an unprotected eye. With the rise of the Sun, the number of optical masses that its rays pass through decreases, which leads to an increase in radiation.

The degree of attenuation of solar radiation in the atmosphere is expressed as Lambert's formula :

I i = I 0 p m , where

I i - radiation reaching the earth's surface,

I 0 - solar constant,

p is the transparency coefficient,

m is the number of optical masses.

Solar radiation near the earth's surface. The amount of radiant energy per unit of the earth's surface depends primarily on the angle of incidence of the sun's rays. On the equal areas at the equator, at middle and high latitudes, there are different amounts of radiation.

Solar insolation (lighting) is greatly weakened cloudiness. The large cloudiness of the equatorial and temperate latitudes and the low cloudiness of the tropical latitudes make significant adjustments to the zonal distribution of the radiant energy of the Sun.

The distribution of solar heat over the earth's surface is depicted on maps of total solar radiation. As these cards show, the largest number solar heat - from 7,530 to 9,200 MJ / m 2 (180-220 kcal / cm 2) receive tropical latitudes. Equatorial latitudes, due to high cloudiness, receive somewhat less heat: 4,185 - 5,860 MJ / m 2 (100-140 kcal / cm 2).

From tropical to temperate latitudes, radiation decreases. On the islands of the Arctic, it is no more than 2,510 MJ/m 2 (60 kcal/cm 2) per year. The distribution of radiation over the earth's surface has a zonal-regional character. Each zone is divided into separate areas (regions), somewhat different from each other.

seasonal fluctuations total radiation.

In equatorial and tropical latitudes, the height of the Sun and the angle of incidence of the sun's rays vary slightly over the months. The total radiation in all months is characterized by large values, seasonal change thermal conditions is either absent or very small. In the equatorial belt, two maxima are faintly outlined, corresponding to the zenithal position of the Sun.

AT temperate zone in the annual course of radiation, the summer maximum is sharply expressed, in which the monthly value of the total radiation is not less than the tropical one. Number warm months decreases with latitude.

In the polar regions the radiation regime changes dramatically. Here, depending on the latitude, from several days to several months, not only heating, but also lighting stops. In summer, the illumination here is continuous, which significantly increases the amount of monthly radiation.

Assimilation of radiation by the earth's surface. Albedo. The total radiation reaching the earth's surface is partially absorbed by the soil and water bodies and turns into heat. On the oceans and seas, the total radiation is spent on evaporation. Part of the total radiation is reflected into the atmosphere ( reflected radiation).

All types of solar rays reach the earth's surface in three ways - in the form of direct, reflected and diffuse solar radiation.
direct solar radiation are rays coming directly from the sun. Its intensity (efficiency) depends on the height of the sun above the horizon: the maximum is observed at noon, and the minimum - in the morning and evening; from the time of year: maximum - in summer, minimum - in winter; from the height of the terrain above sea level (higher in the mountains than on the plain); on the state of the atmosphere (air pollution reduces it). The solar radiation spectrum also depends on the height of the sun above the horizon (the lower the sun is above the horizon, the less ultraviolet rays).
reflected solar radiation are the rays of the sun reflected by the earth or water surface. She expresses herself percentage reflected rays to their total flux is called albedo. The albedo value depends on the nature of the reflective surfaces. When organizing and conducting sunbathing, it is necessary to know and take into account the albedo of the surfaces on which sunbathing is carried out. sunbathing. Some of them are characterized by selective reflectivity. Snow completely reflects infrared rays and ultraviolet to a lesser extent.

scattered solar radiation formed as a result of the scattering of sunlight in the atmosphere. Air molecules and particles suspended in it (the smallest droplets of water, ice crystals, etc.), called aerosols, reflect part of the rays. As a result of multiple reflections, some of them still reach the earth's surface; These are scattered rays of the sun. Mostly ultraviolet, violet and blue rays are scattered, which determines the blue color of the sky in clear weather. The proportion of scattered rays is large at high latitudes (in the northern regions). There the sun is low above the horizon, and therefore the path of the rays to the earth's surface is longer. On the long way rays meet more obstacles and in more dissipate.

(http://new-med-blog.livejournal.com/204

Total solar radiation- all direct and diffuse solar radiation entering the earth's surface. Total solar radiation is characterized by intensity. With a cloudless sky, the total solar radiation is maximum value around noon, and during the year - in the summer.

Radiation balance
The radiation balance of the earth's surface is the difference between the total solar radiation absorbed by the earth's surface and its effective radiation. For the earth's surface
- the incoming part is the absorbed direct and scattered solar radiation, as well as the absorbed counter radiation of the atmosphere;
- the expenditure part consists of heat loss due to the own radiation of the earth's surface.

The radiation balance can be positive(daytime, summer) and negative(at night, in winter); measured in kW/sq.m/min.
Radiation balance of the earth's surface - essential component heat balance of the earth's surface; one of the main climate-forming factors.

Thermal balance of the earth's surface- algebraic sum all types of heat input and output on the surface of land and ocean. The nature of the heat balance and its energy level determine the features and intensity of most exogenous processes. The main components of the ocean heat balance are:
- radiation balance;
- heat consumption for evaporation;
- turbulent heat exchange between the ocean surface and the atmosphere;
- vertical turbulent heat exchange of the ocean surface with the underlying layers; and
- horizontal oceanic advection.

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Measurement of solar radiation.

Actinometers and pyrheliometers are used to measure solar radiation. The intensity of solar radiation is usually measured by its thermal effect and is expressed in calories per unit surface per unit of time.

(http://www.ecosystema.ru/07referats/slo vgeo/967.htm)

Measurement of the intensity of solar radiation is carried out by a Yanishevsky pyranometer complete with a galvanometer or potentiometer.

When measuring total solar radiation, the pyranometer is installed without a shadow screen, while when measuring scattered radiation, with a shadow screen. Direct solar radiation is calculated as the difference between total and scattered radiation.

When determining the intensity of incident solar radiation on the fence, the pyranometer is mounted on it so that the perceived surface of the device is strictly parallel to the surface of the fence. In the absence of automatic recording of radiation, measurements should be made after 30 minutes between sunrise and sunset.

Radiation falling on the surface of the fence is not completely absorbed. Depending on the texture and color of the fence, some of the rays are reflected. The ratio of reflected radiation to incident radiation, expressed as a percentage, is called surface albedo and measured by P.K. Kalitina complete with galvanometer or potentiometer.

For greater accuracy, observations should be carried out in a clear sky and with intense solar irradiation of the fence.

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