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Climatology and meteorologists. Solar radiation

), let us turn to Figure 1 - which shows the parallel and sequential movement of the Sun’s heat to hot brine sunny salt pond. As well as the ongoing changes in the values of various types of solar radiation and their total value along this path.

Figure 1 – Histogram of changes in solar radiation intensity (energy) on the way to the hot brine of a solar salt pond.

To assess the effectiveness of the active use of various types of solar radiation, we will determine which of the natural, man-made and operational factors have a positive and which negative impact on the concentration (increase in input) of solar radiation into the pond and its accumulation by hot brine.

The Earth and atmosphere receive 1.3∙10 24 cal of heat from the Sun per year. It is measured by intensity, i.e. the amount of radiant energy (in calories) that comes from the Sun per unit time per surface area perpendicular to the sun's rays.

The radiant energy of the Sun reaches the Earth in the form of direct and diffuse radiation, i.e. total It is absorbed by the earth's surface and is not completely converted into heat; part of it is lost in the form of reflected radiation.

Direct and scattered (total), reflected and absorbed radiation belong to the short-wave part of the spectrum. Along with short-wave radiation, long-wave radiation from the atmosphere (counter wave) reaches the earth's surface, in turn, the earth's surface emits long-wave radiation (intrinsic).

Direct solar radiation refers to the main natural factor in the supply of energy to the water surface of a solar salt pond.

Solar radiation arriving at the active surface in the form of a beam of parallel rays emanating directly from the solar disk is called direct solar radiation.

Direct solar radiation belongs to the short-wave part of the spectrum (with wavelengths from 0.17 to 4 microns; in fact, rays with a wavelength of 0.29 microns reach the earth’s surface)

The solar spectrum can be divided into three main regions:

Ultraviolet radiation (λ< 0,4 мкм) - 9 % интенсивности.

Short wave ultraviolet region (λ< 0,29 мкм) практически полностью отсутствует на уровне моря вследствие поглощения О 2 , О 3 , О, N 2 и их ионами.

Near ultraviolet range (0.29 microns<λ < 0,4 мкм) достигает Земли малой долей излучения, но вполне достаточной для загара;

Visible radiation (0.4 µm< λ < 0,7 мкм) - 45 % интенсивности.

The clear atmosphere transmits visible radiation almost completely, and it becomes a “window” open for the passage of this type of solar energy to the Earth. The presence of aerosols and atmospheric pollution can cause significant absorption of radiation in this spectrum;

Infrared radiation (λ> 0.7 µm) - 46% intensity. Near infrared (0.7 µm< < 2,5 мкм). На этот диапазон спектра приходится почти половина интенсивности солнечного излучения. Более 20 % солнечной энергии поглощается в атмосфере, в основном парами воды и СО 2 (диоксидом углерода). Концентрация СО 2 в атмосфере относительно постоянна и составляет 0,03 %, а концентрация паров воды меняется очень сильно - почти до 4 %.

At wavelengths greater than 2.5 microns, weak extraterrestrial radiation is intensely absorbed by CO 2 and water, so that only a small part of this range of solar energy reaches the Earth's surface.

The far infrared range (λ>12 µm) of solar radiation practically does not reach the Earth.

From the point of view of the use of solar energy on Earth, only radiation in the wavelength range 0.29 – 2.5 µm should be taken into account

Most of the solar energy outside the atmosphere is in the wavelength range 0.2–4 µm, while on the Earth's surface it is in the range 0.29–2.5 µm.

Let's see how they are redistributed in general , flows of energy that the Sun gives to the Earth. Let's take 100 conventional units of solar power (1.36 kW/m2) falling on the Earth and follow their paths in the atmosphere. One percent (13.6 W/m2), the short ultraviolet of the solar spectrum, is absorbed by molecules in the exosphere and thermosphere, heating them. Another three percent (40.8 W/m2) of near ultraviolet radiation is absorbed by stratospheric ozone. The infrared tail of the solar spectrum (4% or 54.4 W/m2) remains in the upper layers of the troposphere, containing water vapor (there is practically no water vapor above).

The remaining 92 shares of solar energy (1.25 kW/m2) fall within the “transparency window” of the atmosphere of 0.29 microns< < 2,5 мкм. Они проникают в плотные приземные слои воздуха. Значительная часть их (45 единиц или 612 Вт/м 2), преимущественно в синей видимой части спектра, рассеиваются воздухом, придавая голубой цвет небу. Прямые солнечные лучи - оставшиеся 47 процентов (639,2 Вт/м 2) начального светового потока - достигают поверхности. Она отражает примерно 7 процентов (95,2 Вт/м 2) из этих 47 % (639,2 Вт/м 2) и этот свет по пути в космос отдает ещё 3 единицы (40,8 Вт/м 2) диффузному рассеянному свету неба. Forty shares of the energy of the sun's rays, and another 8 from the atmosphere (48 or 652.8 W/m2 in total) are absorbed by the Earth's surface, heating the land and ocean.

The light power scattered in the atmosphere (48 shares in total or 652.8 W/m2) is partially absorbed by it (10 shares or 136 W/m2), and the rest is distributed between the Earth's surface and space. More goes into outer space than reaches the surface, 30 shares (408 W/m2) up, 8 shares (108.8 W/m2) down.

This has been described as a general averaged, a picture of the redistribution of solar energy in the Earth's atmosphere. However, it does not allow solving particular problems of using solar energy to meet the needs of a person in a specific area of his residence and work, and here’s why.

The Earth's atmosphere better reflects oblique solar rays, so hourly insolation at the equator and in middle latitudes is much greater than in high latitudes.

Solar altitude values (elevations above the horizon) of 90, 30, 20, and 12 ⁰ (the air (optical) mass (m) of the atmosphere corresponds to 1, 2, 3, and 5) with a cloudless atmosphere corresponds to an intensity of about 900, 750, 600, and 400 W/m2 (at 42 ⁰ - m = 1.5, and at 15 ⁰ - m = 4). In fact, the total energy of the incident radiation exceeds the indicated values, since it includes not only the direct component, but also the scattered component of the radiation intensity on the horizontal surface under these conditions, scattered at air masses 1, 2, 3 and 5, respectively equal to 110, 90, 70 and 50 W/m2 (with a coefficient of 0.3 - 0.7 for the vertical plane, since only half of the sky is visible). In addition, in areas of the sky close to the Sun, there is a “circumsolar halo” within a radius of ≈ 5⁰.

Table 1 shows insolation data for various regions of the Earth.

Table 1 – Insolation of the direct component by region for a clean atmosphere

From Table 1 it can be seen that the daily amount of solar radiation is maximum not at the equator, but near 40⁰. This fact is also a consequence of the inclination of the earth's axis to the plane of its orbit. During the summer solstice, the Sun in the tropics is overhead almost all day and the duration of daylight is 13.5 hours, more than at the equator on the day of the equinox. With increasing geographic latitude, the length of the day increases, and although the intensity of solar radiation decreases, the maximum value of daytime insolation occurs at a latitude of about 40⁰ and remains almost constant (for cloudless sky conditions) up to the Arctic Circle.

It should be emphasized that the data in Table 1 are valid only for a clean atmosphere. Taking into account cloudiness and atmospheric pollution from industrial waste, which is typical for many countries of the world, the values given in the table should be reduced by at least half. For example, for England in 1970, before the start of the struggle for environmental protection, the annual amount of solar radiation was only 900 kWh/m2 instead of 1700 kWh/m2.

Aerosols significantly reduce the flow of direct solar radiation into the water area of the pond, and they absorb mainly radiation from the visible spectrum, with a wavelength that easily passes through the fresh layer of the pond, and this for the accumulation of solar energy by a pond is of great importance.(A layer of water 1 cm thick is practically opaque to infrared radiation with a wavelength of more than 1 micron). Therefore, water several centimeters thick is used as a heat-protective filter. For glass, the long-wave limit of infrared radiation transmission is 2.7 microns.

A large number of dust particles, freely transported across the steppe, also reduces the transparency of the atmosphere.

Visible solar radiation (0.4 µm< λ < 0,7 мкм) имеет 45 % интенсивности потому, что температура поверхности Солнца 5780 ⁰К.

Great progress was the transition from an electric incandescent lamp with a carbon filament to a modern lamp with a tungsten filament. The thing is that a carbon filament can be brought to a temperature of 2100 ⁰K, and a tungsten filament - up to 2500 ⁰K. Why are these 400 ⁰K so important? The thing is that the purpose of an incandescent lamp is not to heat, but to provide light. Consequently, it is necessary to achieve such a position that the maximum of the curve falls on visible study. The ideal would be to have a filament that could withstand the temperature of the Sun's surface. But even the transition from 2100 to 2500 ⁰K increases the share of energy attributable to visible radiation from 0.5 to 1.6%.

Anyone can feel the infrared rays emanating from a body heated to just 60 - 70 ⁰C by placing their palm from below (to eliminate thermal convection).

The arrival of direct solar radiation into the pond water area corresponds to its arrival on the horizontal irradiation surface. At the same time, the above shows the uncertainty of the quantitative characteristics of the arrival at a specific point in time, both seasonal and daily. The only constant characteristic is the height of the Sun (optical mass of the atmosphere).

The accumulation of solar radiation by the earth's surface and a pond differ significantly.

Natural surfaces of the Earth have different reflective (absorbing) abilities. Thus, dark surfaces (chernozem, peat bogs) have a low albedo value of about 10%. ( Surface albedo- this is the ratio of the flux of radiation reflected by this surface into the surrounding space to the flux incident on it).

Light surfaces (white sand) have a large albedo, 35 – 40%. The albedo of surfaces with grass cover ranges from 15 to 25%. The albedo of the crowns of a deciduous forest in summer is 14–17%, and that of a coniferous forest is 12–15%. The surface albedo decreases with increasing solar altitude.

The albedo of water surfaces ranges from 3 to 45%, depending on the height of the Sun and the degree of excitement.

When the water surface is calm, the albedo depends only on the height of the Sun (Figure 2).

Figure 2 – Dependence of solar radiation reflectance for a calm water surface on the height of the Sun.

The entry of solar radiation and its passage through the water layer has its own characteristics.

In general, the optical properties of water (its solutions) in the visible region of solar radiation are presented in Figure 3.

F0 - flux (power) of incident radiation,

Photr is the flux of radiation reflected by the water surface,

Fpogl is the flux of radiation absorbed by the water mass,

Fpr is the flux of radiation transmitted through the water mass.

Body reflectance Fotr/F0

Absorption coefficient Fpogl/F0

Transmittance coefficient Fpr/F0.

Figure 3 – Optical properties of water (its solutions) in the visible region of solar radiation

At the flat boundary of two media, air - water, the phenomena of reflection and refraction of light are observed.

When light is reflected, the incident beam, the reflected beam and the perpendicular to the reflecting surface, restored at the point of incidence of the beam, lie in the same plane, and the angle of reflection is equal to the angle of incidence. In the case of refraction, the incident ray, the perpendicular reconstructed at the point of incidence of the ray to the interface between the two media, and the refracted ray lie in the same plane. The angle of incidence α and the angle of refraction β (Figure 4) are related sin α /sin β=n2|n1, where n2 is the absolute refractive index of the second medium, n1 - the first. Since for air n1≈1, the formula will take the form sin α /sin β=n2

Figure 4 – Refraction of rays when passing from air to water

When rays go from air to water, they approach the “perpendicular of incidence”; for example, a beam incident on water at an angle to the perpendicular to the surface of the water enters it at an angle that is less than (Figure 4, a). But when the incident beam, sliding along the surface of the water, falls on the water surface almost at a right angle to the perpendicular, for example, at an angle of 89 ⁰ or less, then it enters the water at an angle less than a straight line, namely at an angle of only 48.5 ⁰. At a greater angle to the perpendicular than 48.5 ⁰, the beam cannot enter the water: this is the “limit” angle for water (Figure 4, b).

Consequently, rays falling on water at all possible angles are compressed under water into a rather tight cone with an opening angle of 48.5 ⁰ + 48.5 ⁰ = 97 ⁰ (Figure 4,c).

In addition, the refraction of water depends on its temperature (Table 2), however, these changes are so insignificant that they cannot be of interest for engineering practice on the topic under consideration.

Table 2 - Refractive indexwater at different temperatures t

	n			n			n

Let us now follow the path of the rays going back (from point P) - from water to air (Figure 5). According to the laws of optics, the paths will be the same, and all the rays contained in the aforementioned 97-degree cone will exit into the air at different angles, distributed over the entire 180-degree space above the water. Underwater rays located outside the mentioned angle (97 degrees) will not come out from under the water, but will be reflected entirely from its surface, as from a mirror.

Figure 5 – Refraction of rays when passing from water to air

If n2< n1(вторая среда оптически менее плотная), то α < β. Наибольшему значению β = 90 ⁰ соответствует угол падения α0 , определяемый равенством sinα0=n2/n1. При угле падения α >α0 there is only a reflected ray, there is no refracted ray ( phenomenon of total internal reflection).

Any underwater ray that encounters the surface of the water at an angle greater than the “maximum” (i.e. greater than 48.5⁰) is not refracted, but reflected: it undergoes “ total internal reflection" Reflection is called complete in this case because all the incident rays are reflected here, whereas even the best polished silver mirror reflects only part of the rays incident on it and absorbs the rest. Water under these conditions is an ideal mirror. In this case we are talking about visible light. Generally speaking, the refractive index of water, like other substances, depends on the wavelength (this phenomenon is called dispersion). As a consequence of this, the limiting angle at which total internal reflection occurs is not the same for different wavelengths, but for visible light, when reflected at the water-air boundary, this angle changes by less than 1⁰.

Due to the fact that at a greater angle to the perpendicular than 48.5⁰, a solar ray cannot enter the water: this is the “limiting” angle for water (Figure 4, b), then the water mass does not change so much over the entire range of solar altitudes insignificantly than air - it is always smaller .

However, since the density of water is 800 times greater than the density of air, the absorption of solar radiation by water will change significantly.

In addition, if light radiation passes through a transparent medium, then the spectrum of such light has some characteristics. Certain lines in it are greatly weakened, i.e. waves of the corresponding length are strongly absorbed by the medium under consideration. Such spectra are called absorption spectra. The type of absorption spectrum depends on the substance in question.

Since the salt solution sunny salt pond may contain different concentrations of sodium and magnesium chloride and their ratios, then it makes no sense to speak unambiguously about the absorption spectra. Although there is plenty of research and data on this issue.

For example, studies carried out in the USSR (Yu. Usmanov) to identify the transmittance of radiation of various wavelengths for water and magnesium chloride solutions of various concentrations yielded the following results (Figure 6). And B.J. Brinkworth shows the graphical dependence of the absorption of solar radiation and the monochromatic flux density of solar radiation (radiation) depending on the wavelengths (Figure 7).

Figure 7 – Absorption of solar radiation in water

Figure 6 – Dependence of the throughput of a magnesium chloride solution on concentration

Consequently, the quantitative supply of direct solar radiation to the hot brine of the pond, after entering the water, will depend on: the monochromatic flux density of solar radiation (radiation); from the height of the Sun. And also from the albedo of the surface of the pond, from the purity of the upper layer of the solar salt pond, consisting of fresh water, with a thickness of usually 0.1 - 0.3 m, where mixing cannot be suppressed, the composition, concentration and thickness of the solution in the gradient layer (insulating layer with the brine concentration increasing downwards), on the purity of the water and brine.

From Figures 6 and 7 it follows that water has the greatest transmittance in the visible region of the solar spectrum. This is a very favorable factor for the passage of solar radiation through the upper fresh layer of the solar salt pond.

Bibliography

1 Osadchiy G.B. Solar energy, its derivatives and technologies for their use (Introduction to renewable energy energy) / G.B. Osadchiy. Omsk: IPK Maksheeva E.A., 2010. 572 p.

2 Twidell J. Renewable energy sources / J. Twydell, A . Ware. M.: Energoatomizdat, 1990. 392 p.

3 Duffy J. A. Thermal processes using solar energy / J. A. Duffy, W. A. Beckman. M.: Mir, 1977. 420 p.

4 Climatic resources of Baikal and its basin /N. P. Ladeishchikov, Novosibirsk, Nauka, 1976, 318 p.

5 Pikin S. A. Liquid crystals / S. A. Pikin, L. M. Blinov. M.: Nauka, 1982. 208 p.

6 Kitaygorodsky A.I. Physics for everyone: Photons and nuclei / A.I. Kitaygorodsky. M.: Nauka, 1984. 208 p.

1. On which islands did the extinct dodo bird live?

Mauritius

Comoros

Seychelles

Maldives

2. Near which island is the highest surface temperature of the World Ocean observed?

Socotra

New Britannia

Canary Islands

3. Which of the following languages is not related to the other three?

Danish

Norwegian

Finnish

Swedish

4. What proportion of sunlight is absorbed by the Earth's surface?

5. Which of the following products is not a commercial export item of Ghana?

Cocoa beans

Wood

6. Which of the following French cities experiences the least rainfall in July - August?

Marseilles

7. When did the continent of Pangea break up?

10 million years ago

50 million years ago

250 million years ago

500 million years ago

8. On which island is the Mayon volcano located?

Mindanao

Kalimantan

9. Which of these statements most accurately describes the location of Sofia?

In the Danube basin

In the Balkan Mountains

In the Rhodope Mountains

On the shores of the Black Sea

10. In what city is OPEC headquarters located?

Brussels

Strasbourg

11. In which historical region of Romania are the majority of the population Hungarians?

Wallachia

Moldova

Dobruja

Transylvania

12. Which sea basin does the flow of Lake Baikal belong to?

Laptev

East Siberian

Beringovo

Karskoe

13. Why did the former Renaissance Island almost double in size since 1950?

River sediment

Increase in the area of glaciers

Falling water level

Artificial embankments

14. What is the name of the sparsely populated, hot, arid region of Argentina, prone to severe flooding in the summer?

Gran Chaco

Entre Rios

Patagonia

15. In which part of India do peoples who speak Dravidian languages live?

Northwest

Northeast

16. In which city was the airport named after recently renamed? Chiang Kai-shek

Hong Kong

17. Which Canadian province has recently begun oil sands development?

Ontario

Alberta

British Columbia

18. Which of the following channels does not have gateways?

Kiel

Panamanian

St. Lawrence Riverway

Suez

19. The Nahuatl language is spoken by the descendants of the people who built the majestic cities and temples in Mexico. What kind of people are these?

Olmec

20. Which of the following cities is located in the Basque Country?

Guadalajara

Barcelona

Bilbao

21. Which province in China has the largest population?

Shandong

Sichuan

22. Which countries joined the UN after 2005?

Montenegro

Montenegro and East Timor

Montenegro, East Timor and Eritrea

23. Which part of Great Britain is the least densely populated?

Scotland

Northern Ireland

24. Which city, located on the banks of the Vistula, has its historical center included in the UNESCO World Heritage List?

Katowice

Poznan

25. In what area of geography did Abraham Ortelius distinguish himself?

Oceanology

Meteorology

Geology

Cartography

26. What is Martin Boeheim's greatest achievement?

The world's first printed map

The world's first globe

Conformal projection

Compilation of an encyclopedia of ancient knowledge

27. Which country has the largest number of internal refugees?

Croatia

Bosnia and Herzegovina

Azerbaijan

28. A day is related to 1 year approximately as 1 degree of longitude is to:

360 minutes

60 minutes

60 degrees

Equator length

29. In what direction should you move to get from the point with coordinates 12°N. 176° W to a point with coordinates 30° N. 174°E?

To the northeast

To the southwest

To the northwest

To the southeast

30. Which of the following is characterized by the youngest crust?

East African Rift

East Pacific Rise

Canadian shield

Amazon Basin

31. What tectonic plate movements are observed in the San Andreas Fault zone?

Plate collision

Sliding the plates

Raising and lowering different plates

Horizontal displacement of plates in different directions along one axis

32. In which of these countries is there a migration decline in population?

Ireland

33. What proportion of the world's population lives in urban areas?

34. Which of the following countries is the leader in the number of tourist arrivals?

France

Vietnam

35. Which countries do not have access to the World Ocean and border only on states that also do not have access to the World Ocean?

Uzbekistan

Uzbekistan and Liechtenstein

Uzbekistan, Liechtenstein and Hungary

Uzbekistan, Liechtenstein, Hungary and Central African Republic

36. Which of the following rocks is metamorphic?

Limestone

Basalt

37. At what latitude is the South Magnetic Pole located?

38. Which of the following islands is of coral origin?

Hokkaido

Kiritimati

Seychelles

39. Which of these statements is not true regarding Costa Rica?

Lack of a regular army

High literacy rate

High proportion of indigenous population

High proportion of white population

40. Why can’t Gerhard Mercator’s cylindrical projection be used for topographic calculations?

The areas of objects at the equator are distorted

The areas of objects in high latitudes are distorted

Angles are distorted

The degree grid is distorted

41. Which states are engaged in a territorial dispute about the border running along 22° N latitude?

India and Pakistan

USA and Canada

Egypt and Sudan

Namibia and Angola

42. Which countries recently ended a dispute over the oil-rich area of the Bakassi Peninsula?

Nigeria and Cameroon

DRC and Angola

Gabon and Cameroon

Guinea and Sierra Leone

43. Which of the indicated map scales displays the terrain in the most detail?

44. What is the population density of Singapore?

3543 people/km 2

6573 people/km 2

7350 people/km 2

9433 people/km 2

45. What is the share of the four most populated countries in the Earth's population?

46. What climate zones will you cross when traveling from Darwin to Alice Springs?

Temperate maritime, subequatorial humid, subequatorial dry, tropical dry

Subequatorial dry, tropical dry, tropical desert

Subequatorial humid, subequatorial dry, tropical dry

Subequatorial humid, subequatorial dry, tropical dry, tropical desert

47. What condition can eliminate the influence of typhoons?

Location on the equator

Located at north latitude 15°

Being above the sea

Being in the tropics

48. When is the highest water level in the Zambezi River?

49. What is the reason for the black-red color of the water in the Rio Negro tributary of the Amazon?

Industrial water pollution in the river

Tannins contained in plant litter

Rocks from the Andes

Water erosion of equatorial soils

50. Point with coordinates 18° S. 176° W located on the islands:

Caroline

Societies

Hawaiian

From the list of countries below, select the 5 with the highest fertility rates and rank these countries in descending order:

Israel

Guatemala

Spain

From the list of countries below, select the 5 with the longest coastline and rank them in descending order of their value:

Malaysia

Australia

Ukraine

Indonesia

Venezuela

Brazil

Bangladesh

Costa Rica

On an outline map, mark the 5 most populated countries in South America.

On an outline map, mark the 5 African countries with the largest outflow of refugees.

ANSWERS

1 - Mauritius

2 - Socotra

3 - Finnish

4 - About 50%

6 - Marseille

7 - The closest answer is “250 million years ago.”

9 - The test formulation cannot be considered correct. The option “In the Danube basin” is completely correct, but not accurate: such a definition of the position does not focus on Sofia. The option “In the Balkan Mountains” more accurately indicates the location, but the concept of “Balkan Mountains” itself is vague.

11 - Transylvania

12 - Karskoe

13 - Drop in water level

14 - Patagonia

16 - Taipei

17 - Alberta

18 - Suez

19 - Aztecs

20 - Bilbao

21 - Sichuan

22 - Montenegro

23 - Scotland

24 - Krakow

25 - Cartography

26 - Globe

27 - Bosnia and Herzegovina

28 - Equator length

29 - To the northwest

30 - East Pacific Rise

31 - Horizontal offset...

32 - Apparently, this refers to Iran, although there are no exact data.

33 - 49% (although calculations for 2007 show that the number of city dwellers is already more than 50%).

34 - France

35 - Uzbekistan and Liechtenstein

36 - Marble

38 - Kiritimati

39 - Lack of a regular army. However, other signs cannot be rejected, because The meaning of the word "high" is not defined. The test is incorrect.

40 - The areas of objects in high latitudes are distorted. But the 4th option is not without meaning. The test is incorrect.

41 - Egypt and Sudan

42 - Nigeria and Cameroon

44 - 7350. But such questions cannot be asked.

45 - About 43%

46 - 2nd answer

47 - At the equator

49 - Tannins

Niger, Egypt, Yemen, South Africa, Laos, Malaysia, Australia, Sweden, Indonesia, Brazil. The task, however, is incorrect. The length of the coastline is, in principle, an unmeasurable quantity. Cm.: K.S. Lazarevich. Coastline length//Geography, No./2004.

The wording of the questions is from memory and may differ slightly from the original ones: The US National Geographic Society does not issue tasks to either competition participants or team leaders.

The claim that Hungarians constitute the majority in Transylvania is debatable. Romanians have a different point of view on this matter.

Heat sources. Thermal energy is of decisive importance in the life of the atmosphere. The main source of this energy is the Sun. As for the thermal radiation of the Moon, planets and stars, it is so insignificant for the Earth that it practically cannot be taken into account. Significantly more thermal energy is provided by the internal heat of the Earth. According to geophysicists' calculations, the constant flow of heat from the Earth's interior increases the temperature of the earth's surface by 0°.1. But such a heat influx is still so small that there is no need to take it into account either. Thus, the only source of thermal energy on the surface of the Earth can be considered only the Sun.

Solar radiation. The sun, which has a photosphere (radiating surface) temperature of about 6000°, radiates energy into space in all directions. Part of this energy, in the form of a huge beam of parallel solar rays, hits the Earth. Solar energy that reaches the surface of the Earth in the form of direct rays from the Sun is called direct solar radiation. But not all solar radiation directed at the Earth reaches the earth's surface, since the sun's rays, passing through a thick layer of the atmosphere, are partially absorbed by it, partially scattered by molecules and suspended air particles, and some are reflected by clouds. That part of solar energy that is dissipated in the atmosphere is called scattered radiation. Scattered solar radiation travels through the atmosphere and reaches the Earth's surface. We perceive this type of radiation as uniform daylight, when the Sun is completely covered by clouds or has just disappeared below the horizon.

Direct and diffuse solar radiation, having reached the Earth's surface, is not completely absorbed by it. Part of the solar radiation is reflected from the earth's surface back into the atmosphere and is found there in the form of a stream of rays, the so-called reflected solar radiation.

The composition of solar radiation is very complex, which is associated with the very high temperature of the radiating surface of the Sun. Conventionally, according to wavelength, the spectrum of solar radiation is divided into three parts: ultraviolet (η<0,4<μ видимую глазом (η from 0.4μ to 0.76μ) and the infrared part (η >0.76μ). In addition to the temperature of the solar photosphere, the composition of solar radiation at the earth's surface is also influenced by the absorption and scattering of part of the sun's rays as they pass through the air shell of the Earth. In this regard, the composition of solar radiation at the upper boundary of the atmosphere and at the surface of the Earth will be different. Based on theoretical calculations and observations, it has been established that at the boundary of the atmosphere, ultraviolet radiation accounts for 5%, visible rays - 52% and infrared - 43%. At the earth's surface (at a solar altitude of 40°), ultraviolet rays account for only 1%, visible rays account for 40%, and infrared rays account for 59%.

Solar radiation intensity. The intensity of direct solar radiation is understood as the amount of heat in calories received per minute. from the radiant energy of the Sun's surface in 1 cm 2, located perpendicular to the sun's rays.

To measure the intensity of direct solar radiation, special instruments are used - actinometers and pyrheliometers; The amount of scattered radiation is determined by a pyranometer. Automatic registration of the duration of solar radiation is carried out by actinographs and heliographs. The spectral intensity of solar radiation is determined by a spectrobolograph.

At the boundary of the atmosphere, where the absorbing and scattering effects of the Earth's air shell are excluded, the intensity of direct solar radiation is approximately 2 feces by 1 cm 2 surfaces in 1 min. This quantity is called solar constant. Solar radiation intensity in 2 feces by 1 cm 2 in 1 min. provides such a large amount of heat during the year that it would be enough to melt a layer of ice 35 m thick if such a layer covered the entire earth's surface.

Numerous measurements of the intensity of solar radiation give reason to believe that the amount of solar energy arriving at the upper boundary of the Earth's atmosphere fluctuates by several percent. Oscillations are periodic and non-periodic, apparently associated with processes occurring on the Sun itself.

In addition, some change in the intensity of solar radiation occurs during the year due to the fact that the Earth, in its annual rotation, moves not in a circle, but in an ellipse, at one of the foci of which the Sun is located. In this regard, the distance from the Earth to the Sun changes and, consequently, the intensity of solar radiation fluctuates. The greatest intensity is observed around January 3, when the Earth is closest to the Sun, and the lowest around July 5, when the Earth is at its maximum distance from the Sun.

For this reason, fluctuations in the intensity of solar radiation are very small and can only be of theoretical interest. (The amount of energy at maximum distance is related to the amount of energy at minimum distance as 100:107, i.e. the difference is completely negligible.)

Conditions of irradiation of the surface of the globe. The spherical shape of the Earth alone leads to the fact that the radiant energy of the Sun is distributed very unevenly on the Earth's surface. So, on the days of the spring and autumn equinox (March 21 and September 23), only at the equator at noon the angle of incidence of the rays will be 90° (Fig. 30), and as it approaches the poles it will decrease from 90 to 0°. Thus,

if at the equator the amount of radiation received is taken as 1, then at the 60th parallel it will be expressed as 0.5, and at the pole it will be equal to 0.

The globe, in addition, has a daily and annual movement, and the earth's axis is inclined to the orbital plane by 66°.5. Due to this inclination, an angle of 23°30 is formed between the equatorial plane and the orbital plane. This circumstance leads to the fact that the angles of incidence of the sun's rays for the same latitudes will vary within 47° (23.5 + 23.5) .

Depending on the time of year, not only the angle of incidence of the rays changes, but also the duration of illumination. If in tropical countries the length of day and night is approximately the same at all times of the year, then in polar countries, on the contrary, it is very different. So, for example, at 70° N. w. in summer the Sun does not set for 65 days at 80° N. sh. - 134, and at the pole -186. Because of this, radiation at the North Pole on the day of the summer solstice (June 22) is 36% greater than at the equator. As for the entire summer half of the year, the total amount of heat and light received by the pole is only 17% less than at the equator. Thus, in the summer in polar countries, the duration of illumination largely compensates for the lack of radiation that is a consequence of the small angle of incidence of the rays. In the winter half of the year, the picture is completely different: the amount of radiation at the same North Pole will be equal to 0. As a result, over the year the average amount of radiation at the pole is 2.4 less than at the equator. From all that has been said, it follows that the amount of solar energy that the Earth receives through radiation is determined by the angle of incidence of the rays and the duration of irradiation.

In the absence of an atmosphere at different latitudes, the earth's surface would receive the following amount of heat per day, expressed in calories per 1 cm 2(see table on page 92).

The distribution of radiation over the earth's surface given in the table is usually called solar climate. We repeat that we have such a distribution of radiation only at the upper boundary of the atmosphere.

Weakening of solar radiation in the atmosphere. So far we have talked about the conditions for the distribution of solar heat over the earth's surface, without taking into account the atmosphere. Meanwhile, the atmosphere in this case is of great importance. Solar radiation, passing through the atmosphere, experiences dispersion and, in addition, absorption. Both of these processes together attenuate solar radiation to a significant extent.

The sun's rays, passing through the atmosphere, first experience scattering (diffusion). Scattering is created by the fact that light rays, refracted and reflected from air molecules and particles of solid and liquid bodies in the air, deviate from the straight path To really "dissipate".

Scattering greatly attenuates solar radiation. With an increase in the amount of water vapor and especially dust particles, the dispersion increases and the radiation is weakened. In large cities and desert areas, where the dust content of the air is greatest, dispersion weakens the strength of radiation by 30-45%. Thanks to scattering, daylight is obtained that illuminates objects, even if the sun's rays do not directly fall on them. Scattering also determines the color of the sky.

Let us now dwell on the ability of the atmosphere to absorb radiant energy from the Sun. The main gases that make up the atmosphere absorb relatively little radiant energy. Impurities (water vapor, ozone, carbon dioxide and dust), on the contrary, have a high absorption capacity.

In the troposphere, the most significant impurity is water vapor. They absorb especially strongly infrared (long-wavelength), i.e., predominantly thermal rays. And the more water vapor in the atmosphere, the naturally more and. absorption. The amount of water vapor in the atmosphere is subject to large changes. Under natural conditions, it varies from 0.01 to 4% (by volume).

Ozone has a very high absorption capacity. A significant admixture of ozone, as already mentioned, is located in the lower layers of the stratosphere (above the tropopause). Ozone absorbs ultraviolet (short-wave) rays almost completely.

Carbon dioxide also has a high absorption capacity. It absorbs mainly long-wave, i.e., predominantly thermal rays.

Dust in the air also absorbs some solar radiation. When heated by the sun's rays, it can significantly increase the air temperature.

Of the total amount of solar energy coming to the Earth, the atmosphere absorbs only about 15%.

The attenuation of solar radiation by scattering and absorption by the atmosphere is very different for different latitudes of the Earth. This difference depends primarily on the angle of incidence of the rays. At the zenith position of the Sun, the rays, falling vertically, cross the atmosphere along the shortest path. As the angle of incidence decreases, the path of the rays lengthens and the attenuation of solar radiation becomes more significant. The latter is clearly visible from the drawing (Fig. 31) and the attached table (in the table, the path of the sun's ray at the zenith position of the Sun is taken as one).

Depending on the angle of incidence of the rays, not only the number of rays changes, but also their quality. During the period when the Sun is at its zenith (above the head), ultraviolet rays account for 4%,

visible - 44% and infrared - 52%. When the Sun is positioned near the horizon, there are no ultraviolet rays at all, visible 28% and infrared 72%.

The complexity of the atmosphere's influence on solar radiation is further aggravated by the fact that its transmission capacity varies greatly depending on the time of year and weather conditions. So, if the sky remained cloudless all the time, then the annual course of the influx of solar radiation at various latitudes could be expressed graphically as follows (Fig. 32). The drawing clearly shows that with a cloudless sky in Moscow in May, June and July, the heat more would be received from solar radiation than at the equator. Similarly, in the second half of May, June and the first half of July, more heat would be received at the North Pole than at the equator and in Moscow. We repeat that this would be the case with a cloudless sky. But in reality this does not work, because cloudiness significantly weakens solar radiation. Let's give an example shown on the graph (Fig. 33). The graph shows how much solar radiation does not reach the Earth's surface: a significant part of it is delayed by the atmosphere and clouds.

However, it must be said that the heat absorbed by the clouds partly goes to warm the atmosphere, and partly indirectly reaches the earth's surface.

Daily and annual variations in solar intensitylight radiation. The intensity of direct solar radiation at the Earth's surface depends on the height of the Sun above the horizon and on the state of the atmosphere (its dust content). If. If the transparency of the atmosphere was constant throughout the day, then the maximum intensity of solar radiation would be observed at noon, and the minimum at sunrise and sunset. In this case, the graph of the daily intensity of solar radiation would be symmetrical relative to half a day.

The content of dust, water vapor and other impurities in the atmosphere is constantly changing. In this regard, the transparency of the air changes and the symmetry of the solar radiation intensity graph is disrupted. Often, especially in summer, at midday, when the earth's surface is heated intensely, powerful upward air currents arise, and the amount of water vapor and dust in the atmosphere increases. This results in a significant reduction in solar radiation at midday; The maximum intensity of radiation in this case is observed in the pre-noon or afternoon hours. The annual variation in the intensity of solar radiation is also associated with changes in the height of the Sun above the horizon throughout the year and with the state of transparency of the atmosphere in different seasons. In the countries of the northern hemisphere, the highest height of the Sun above the horizon occurs in the month of June. But at the same time, the greatest dustiness of the atmosphere is observed. Therefore, the maximum intensity usually occurs not in the middle of summer, but in the spring months, when the Sun rises quite high* above the horizon, and the atmosphere after winter remains relatively clear. To illustrate the annual variation of solar radiation intensity in the northern hemisphere, we present data on monthly average midday radiation intensity values in Pavlovsk.

The amount of heat from solar radiation. During the day, the Earth's surface continuously receives heat from direct and diffuse solar radiation or only from diffuse radiation (in cloudy weather). The daily amount of heat is determined based on actinometric observations: by taking into account the amount of direct and diffuse radiation received on the earth's surface. Having determined the amount of heat for each day, the amount of heat received by the earth's surface per month or per year is calculated.

The daily amount of heat received by the earth's surface from solar radiation depends on the intensity of radiation and the duration of its action during the day. In this regard, the minimum heat influx occurs in winter, and the maximum in summer. In the geographic distribution of total radiation around the globe, its increase is observed with decreasing latitude. This position is confirmed by the following table.

The role of direct and diffuse radiation in the annual amount of heat received by the earth's surface at different latitudes of the globe is different. At high latitudes, the annual amount of heat is dominated by scattered radiation. With decreasing latitude, direct solar radiation becomes dominant. For example, in Tikhaya Bay, diffuse solar radiation provides 70% of the annual amount of heat, and direct radiation only 30%. In Tashkent, on the contrary, direct solar radiation provides 70%, scattered only 30%.

Reflectivity of the Earth. Albedo. As already indicated, the Earth's surface absorbs only part of the solar energy that reaches it in the form of direct and diffuse radiation. The other part is reflected into the atmosphere. The ratio of the amount of solar radiation reflected by a given surface to the amount of radiant energy flux incident on this surface is called albedo. Albedo is expressed as a percentage and characterizes the reflectivity of a given surface area.

Albedo depends on the nature of the surface (soil properties, presence of snow, vegetation, water, etc.) and on the angle of incidence of the Sun's rays on the Earth's surface. So, for example, if the rays fall on the earth's surface at an angle of 45°, then:

From the above examples it is clear that the reflectivity of different objects is not the same. It is greatest near snow and least near water. However, the examples we took relate only to those cases when the height of the Sun above the horizon is 45°. As this angle decreases, the reflectivity increases. So, for example, at a solar altitude of 90°, water reflects only 2%, at 50° - 4%, at 20° - 12%, at 5° - 35-70% (depending on the condition of the water surface).

On average, with a cloudless sky, the surface of the globe reflects 8% of solar radiation. In addition, 9% is reflected by the atmosphere. Thus, the globe as a whole, with a cloudless sky, reflects 17% of the radiant energy of the Sun falling on it. If the sky is covered with clouds, then 78% of the radiation is reflected from them. If we take natural conditions, based on the ratio between a cloudless sky and a sky covered with clouds, which is observed in reality, then the reflectivity of the Earth as a whole is equal to 43%.

Terrestrial and atmospheric radiation. The Earth, receiving solar energy, heats up and itself becomes a source of heat radiation into space. However, the rays emitted by the earth's surface are very different from the sun's rays. The earth emits only long-wave (λ 8-14 μ) invisible infrared (thermal) rays. The energy emitted by the earth's surface is called terrestrial radiation. Radiation from the Earth occurs... day and night. The higher the temperature of the emitting body, the greater the radiation intensity. Terrestrial radiation is determined in the same units as solar radiation, i.e. in calories from 1 cm 2 surfaces in 1 min. Observations have shown that the amount of terrestrial radiation is small. Usually it reaches 15-18 hundredths of a calorie. But, acting continuously, it can give a significant thermal effect.

The strongest terrestrial radiation is obtained with a cloudless sky and good transparency of the atmosphere. Cloud cover (especially low clouds) significantly reduces terrestrial radiation and often brings it to zero. Here we can say that the atmosphere, together with the clouds, is a good “blanket” that protects the Earth from excessive cooling. Parts of the atmosphere, like areas of the earth's surface, emit energy according to their temperature. This energy is called atmospheric radiation. The intensity of atmospheric radiation depends on the temperature of the radiating part of the atmosphere, as well as on the amount of water vapor and carbon dioxide contained in the air. Atmospheric radiation belongs to the long-wave group. It spreads in the atmosphere in all directions; a certain amount of it reaches the earth's surface and is absorbed by it, the other part goes into interplanetary space.

ABOUT the arrival and consumption of solar energy on Earth. The earth's surface, on the one hand, receives solar energy in the form of direct and diffuse radiation, and on the other hand, loses part of this energy in the form of terrestrial radiation. As a result of the arrival and consumption of solar energy, some result is obtained. In some cases this result may be positive, in others negative. Let's give examples of both.

January 8. The day is cloudless. On 1 cm 2 earth's surface received in 20 days feces direct solar radiation and 12 feces scattered radiation; in total, this gives 32 cal. During the same time, due to radiation 1 cm? earth's surface lost 202 cal. As a result, in accounting language, the balance sheet has a loss of 170 feces(negative balance).

July 6. The sky is almost cloudless. 630 received from direct solar radiation feces, from scattered radiation 46 cal. In total, therefore, the earth's surface received 1 cm 2 676 cal. 173 lost through terrestrial radiation cal. The balance sheet shows a profit of 503 feces(balance is positive).

From the examples given, among other things, it is completely clear why temperate latitudes are cold in winter and warm in summer.

Use of solar radiation for technical and domestic purposes. Solar radiation is an inexhaustible natural source of energy. The amount of solar energy on Earth can be judged by this example: if, for example, we use the heat of solar radiation falling on only 1/10 of the area of the USSR, then we can obtain energy equal to the work of 30 thousand Dnieper hydroelectric power stations.

People have long sought to use the free energy of solar radiation for their needs. To date, many different solar power plants have been created that operate using solar radiation and are widely used in industry and to meet the domestic needs of the population. In the southern regions of the USSR, solar water heaters, boilers, salt water desalination plants, solar dryers (for drying fruits), kitchens, bathhouses, greenhouses, and devices for medicinal purposes operate on the basis of the widespread use of solar radiation in industry and public utilities. Solar radiation is widely used in resorts to treat and improve people's health.

- Source-

Polovinkin, A.A. Fundamentals of general geoscience/ A.A. Polovinkin. - M.: State educational and pedagogical publishing house of the Ministry of Education of the RSFSR, 1958. - 482 p.

Post Views: 312

To determine the main and minor factors influencing the efficiency of solar energy storage by a solar salt pond, the basic module of a number of renewable energy sources (RES) energy systems and installations, let us turn to Figure 1 - which shows the parallel and sequential movement of the heat of the Sun to the hot brine of a solar salt pond . As well as the ongoing changes in the values of various types of solar radiation and their total value along this path.

Figure 1 – Histogram of changes in solar radiation intensity (energy) on the way to the hot brine of a solar salt pond.

The Earth and atmosphere receive 1.3∙1024 cal of heat from the Sun per year. It is measured by intensity, i.e. the amount of radiant energy (in calories) that comes from the Sun per unit time per surface area perpendicular to the sun's rays.

Direct and scattered (total), reflected and absorbed radiation belong to the short-wave part of the spectrum. Along with short-wave radiation, long-wave radiation from the atmosphere (counter radiation) reaches the earth's surface; in turn, the earth's surface emits long-wave radiation (its own radiation).

Direct solar radiation refers to the main natural factor in the supply of energy to the water surface of a solar salt pond. Solar radiation arriving at the active surface in the form of a beam of parallel rays emanating directly from the disk of the Sun is called direct solar radiation. Direct solar radiation belongs to the short-wave part of the spectrum (with wavelengths from 0.17 to 4 microns; in fact, rays with a wavelength of 0.29 microns reach the earth’s surface)

The solar spectrum can be divided into three main regions:

Ultraviolet radiation (- visible radiation (0.4 µm - infrared radiation (> 0.7 µm) - 46% intensity. Near infrared region (0.7 µm) At wavelengths greater than 2.5 µm, weak extraterrestrial radiation is intensively absorbed by CO2 and water , so only a small portion of this range of solar energy reaches the Earth's surface.

Almost no far infrared (>12 µm) solar radiation reaches the Earth.

From the point of view of the application of solar energy on Earth, only radiation in the wavelength range 0.29 - 2.5 µm should be taken into account. Most solar energy outside the atmosphere occurs in the wavelength range 0.2 - 4 µm, and on the Earth's surface - in range 0.29 – 2.5 µm.

Let us trace how, in general, the flows of energy that the Sun gives to the Earth are redistributed. Let's take 100 conventional units of solar power (1.36 kW/m2) falling on the Earth and follow their paths in the atmosphere. One percent (13.6 W/m2), the short ultraviolet of the solar spectrum, is absorbed by molecules in the exosphere and thermosphere, heating them. Another three percent (40.8 W/m2) of near ultraviolet radiation is absorbed by stratospheric ozone. The infrared tail of the solar spectrum (4% or 54.4 W/m2) remains in the upper layers of the troposphere, containing water vapor (there is practically no water vapor above).

The remaining 92 shares of solar energy (1.25 kW/m2) fall within the “transparency window” of the atmosphere of 0.29 microns. Light power scattered in the atmosphere (48 shares or 652.8 W/m2 in total) is partially absorbed by it (10 shares or 136 W /m2), and the rest is distributed between the Earth’s surface and space. More goes into outer space than reaches the surface, 30 shares (408 W/m2) up, 8 shares (108.8 W/m2) down.

This described the general, averaged picture of the redistribution of solar energy in the Earth's atmosphere. However, it does not allow solving particular problems of using solar energy to meet the needs of a person in a specific area of his residence and work, and here’s why.

The Earth's atmosphere better reflects oblique solar rays, so hourly insolation at the equator and in middle latitudes is much greater than in high latitudes.

The daily amount of solar radiation is maximum not at the equator, but near 40⁰. This fact is also a consequence of the inclination of the earth's axis to the plane of its orbit. During the summer solstice, the Sun in the tropics is overhead almost all day and the duration of daylight is 13.5 hours, more than at the equator on the day of the equinox. With increasing geographic latitude, the length of the day increases, and although the intensity of solar radiation decreases, the maximum value of daytime insolation occurs at a latitude of about 40⁰ and remains almost constant (for cloudless sky conditions) up to the Arctic Circle.

Taking into account cloudiness and atmospheric pollution from industrial waste, which is typical for many countries of the world, the values given in the table should be reduced by at least half. For example, for England in 1970, before the start of the struggle for environmental protection, the annual amount of solar radiation was only 900 kWh/m2 instead of 1700 kWh/m2.

The first data on the transparency of the atmosphere on Lake Baikal were obtained by V.V. Bufal in 1964 It showed that the values of direct solar radiation over Baikal are on average 13% higher than in Irkutsk. The average spectral transparency coefficient of the atmosphere on Northern Baikal in summer is 0.949, 0.906, 0.883 for red, green and blue filters, respectively. In summer, the atmosphere is more optically unstable than in winter, and this instability varies significantly from the afternoon to the afternoon. Depending on the annual course of attenuation by water vapor and aerosols, their contribution to the overall attenuation of solar radiation also changes. In the cold part of the year, aerosols play the main role, in the warm part - water vapor. The Baikal Basin and Lake Baikal are distinguished by a relatively high integral transparency of the atmosphere. At optical mass m = 2, the average values of the transparency coefficient range from 0.73 (summer) to 0.83 (winter). At the same time, day-to-day changes in the integral transparency of the atmosphere are large, especially at midday - from 0.67 to 0.77. Aerosols significantly reduce the entry of direct solar radiation into the pond's water area, and they absorb mainly radiation from the visible spectrum, with a wavelength that easily passes through the fresh layer of the pond, and this is of great importance for the accumulation of solar energy by the pond. (A layer of water 1 cm thick is practically opaque to infrared radiation with a wavelength of more than 1 micron). Therefore, water several centimeters thick is used as a heat-protective filter. For glass, the long-wave limit of infrared radiation transmission is 2.7 microns.

A large number of dust particles, freely transported across the steppe, also reduces the transparency of the atmosphere.

Electromagnetic radiation is emitted by all heated bodies, and the colder the body, the lower the intensity of the radiation and the further into the long-wave region the maximum of its spectrum is shifted. There is a very simple relationship [ = 0.2898 cm∙deg. (Wien’s law)], with the help of which it is easy to establish where the maximum radiation of a body with temperature (⁰K) is located. For example, the human body, having a temperature of 37 + 273 = 310 ⁰K, emits infrared rays with a maximum near the value = 9.3 μm. And the walls, for example, of a solar dryer, with a temperature of 90 ⁰C, will emit infrared rays with a maximum near the value = 8 microns. Visible solar radiation (0.4 microns) At one time, great progress was the transition from an incandescent electric lamp with a carbon filament to a modern lamp with a tungsten filament. The thing is that the carbon filament can be brought to a temperature of 2100 ⁰K, and the tungsten one - up to 2500 ⁰K . Why is this 400 ⁰K so important? The whole point is that the purpose of an incandescent lamp is not to heat, but to give light. Therefore, it is necessary to achieve such a position that the maximum of the curve falls on visible study. The ideal would be to have a filament that would withstand temperature of the surface of the Sun. But even the transition from 2100 to 2500 ⁰K increases the share of energy attributable to visible radiation from 0.5 to 1.6%.

Anyone can feel the infrared rays emanating from a body heated to just 60 - 70 ⁰C by placing their palm from below (to eliminate thermal convection). The arrival of direct solar radiation into the pond water area corresponds to its arrival on the horizontal irradiation surface. At the same time, the above shows the uncertainty of the quantitative characteristics of the arrival at a specific point in time, both seasonal and daily. The only constant characteristic is the height of the Sun (optical mass of the atmosphere).

The accumulation of solar radiation by the earth's surface and a pond differ significantly.

Natural surfaces of the Earth have different reflective (absorbing) abilities. Thus, dark surfaces (chernozem, peat bogs) have a low albedo value of about 10%. (The albedo of a surface is the ratio of the radiation flux reflected by this surface into the surrounding space to the flux incident on it).

The albedo of water surfaces ranges from 3 to 45%, depending on the height of the Sun and the degree of excitement.

When the water surface is calm, the albedo depends only on the height of the Sun (Figure 2).

Figure 2 – Dependence of solar radiation reflectance for a calm water surface on the height of the Sun.

The entry of solar radiation and its passage through the water layer has its own characteristics.

In general, the optical properties of water (its solutions) in the visible region of solar radiation are presented in Figure 3.

Figure 3 – Optical properties of water (its solutions) in the visible region of solar radiation

At the flat boundary of two media, air - water, the phenomena of reflection and refraction of light are observed.

When light is reflected, the incident beam, the reflected beam and the perpendicular to the reflecting surface, restored at the point of incidence of the beam, lie in the same plane, and the angle of reflection is equal to the angle of incidence. In the case of refraction, the incident ray, the perpendicular reconstructed at the point of incidence of the ray to the interface between the two media, and the refracted ray lie in the same plane. The angle of incidence and the angle of refraction (Figure 4) are related to /, where is the absolute refractive index of the second medium, and is the first. Since for air, the formula will take the form

Figure 4 – Refraction of rays when passing from air to water

Consequently, rays falling on water at all possible angles are compressed under water into a rather tight cone with an opening angle of 48.5 ⁰ + 48.5 ⁰ = 97 ⁰ (Figure 4,c). In addition, the refraction of water depends on its temperature, but these changes are so insignificant that they cannot be of interest for engineering practice on the topic under consideration.

Figure 5 – Refraction of rays when passing from water to air

If there is only a reflected ray, there is no refracted ray (the phenomenon of total internal reflection).

Any underwater ray that encounters the surface of the water at an angle greater than the “limiting” one (i.e. greater than 48.5⁰) is not refracted, but reflected: it undergoes “total internal reflection.” Reflection is called complete in this case because all the incident rays are reflected here, whereas even the best polished silver mirror reflects only part of the rays incident on it and absorbs the rest. Water under these conditions is an ideal mirror. In this case we are talking about visible light. Generally speaking, the refractive index of water, like other substances, depends on the wavelength (this phenomenon is called dispersion). As a consequence of this, the limiting angle at which total internal reflection occurs is not the same for different wavelengths, but for visible light, when reflected at the water-air boundary, this angle changes by less than 1⁰.

However, since the density of water is 800 times greater than the density of air, the absorption of solar radiation by water will change significantly. In addition, if light radiation passes through a transparent medium, then the spectrum of such light has some characteristics. Certain lines in it are strongly attenuated, that is, waves of the corresponding length are strongly absorbed by the medium in question. Such spectra are called absorption spectra. The type of absorption spectrum depends on the substance in question.

Since a solution of salts from a solar salt pond may contain different concentrations of sodium and magnesium chloride and their ratios, there is no point in talking unambiguously about absorption spectra. Although there is plenty of research and data on this issue.

Bibliography

1 Osadchiy G.B. Solar energy, its derivatives and technologies for their use (Introduction to renewable energy energy) / G.B. Osadchiy. Omsk: IPK Maksheeva E.A., 2010. 572 p.
2 Twydell J. Renewable energy sources / J. Twydell, A. Ware. M.: Energoatomizdat, 1990. 392 p.
3 Duffy J. A. Thermal processes using solar energy / J. A. Duffy, W. A. Beckman. M.: Mir, 1977. 420 p.
4 Climatic resources of Baikal and its basin /N. P. Ladeishchikov, Novosibirsk, Nauka, 1976, 318 p.
5 Pikin S. A. Liquid crystals / S. A. Pikin, L. M. Blinov. M.: Nauka, 1982. 208 p.
6 Kitaygorodsky A.I. Physics for everyone: Photons and nuclei / A.I. Kitaygorodsky. M.: Nauka, 1984. 208 p.
7 Kuhling H. Handbook of Physics. / H. Kuhling. M.: Mir, 1982. 520 p.
8 Enochovich A. S. Handbook of physics and technology / A. S. Enochovich. M.: Education, 1989. 223 p.
9 Perelman Ya. I. Entertaining physics. Book 2 / Ya. I. Perelman. M.: Nauka, 1986. 272 p.

Solar energy reaches the upper boundary of the atmosphere equal to 100%.

Ultraviolet radiation, which makes up 3% of 100% of incoming sunlight, is mostly absorbed by the ozone layer at the top of the atmosphere.

About 40% of the remaining 97% interacts with clouds - of which 24% is reflected back into space, 2% is absorbed by clouds and 14% is scattered, reaching the earth's surface as diffuse radiation.

32% of incoming radiation interacts with water vapor, dust and haze in the atmosphere - 13% of it is absorbed, 7% is reflected back into space and 12% reaches the earth's surface as scattered sunlight (Fig. 6)

Rice. 6. Radiation balance of the Earth

Consequently, from the original 100% of the solar radiation of the Earth's surface, 2% of direct sunlight and 26% of diffuse light reach.

Of this total, 4% is reflected from the earth's surface back into space, and the total reflection into space is 35% of incident sunlight.

Of the 65% of light absorbed by the Earth, 3% comes from the upper atmosphere, 15% from the lower atmosphere, and 47% from the Earth's surface - ocean and land.

In order for the Earth to maintain thermal equilibrium, 47% of all solar energy that passes through the atmosphere and is absorbed by land and sea must be released back into the atmosphere by land and sea.

The visible part of the spectrum of radiation arriving at the surface of the ocean and creating illumination consists of solar rays passing through the atmosphere (direct radiation) and some of the rays scattered by the atmosphere in all directions, including towards the surface of the ocean (scattered radiation).

The ratio of the energy of these two light fluxes falling on a horizontal surface depends on the height of the Sun - the higher it is above the horizon, the greater the proportion of direct radiation

The illumination of the sea surface under natural conditions also depends on cloudiness. Tall and thin clouds cast down a lot of scattered light, due to which the illumination of the sea surface at average solar altitudes can be even greater than in a cloudless sky. Dense, rainy clouds sharply reduce illumination.

Light rays that create illumination on the sea surface undergo reflection and refraction at the water-air boundary (Fig. 7) according to the well-known physical law of Snell.

Rice. 7. Reflection and refraction of a ray of light on the surface of the ocean

Thus, all light rays falling on the surface of the sea, partially reflected, are refracted and enter the sea.

The ratio between refracted and reflected light fluxes depends on the height of the Sun. At a solar altitude of 0 0, the entire light flux is reflected from the surface of the sea. As the altitude of the Sun increases, the proportion of the light flux penetrating into the water increases, and at a solar altitude of 90 0, 98% of the total flux incident on the surface penetrates into the water.

The ratio of the light flux reflected from the sea surface to the incident light is called sea surface albedo . Then the albedo of the sea surface at a solar altitude of 90 0 will be 2%, and for 0 0 - 100%. The albedo of the sea surface is different for direct and diffuse light fluxes. The albedo of direct radiation depends significantly on the altitude of the Sun, while the albedo of scattered radiation practically does not depend on the altitude of the Sun.

Climatology and meteorologists. Solar radiation

Direct solar radiation refers to the main natural factor in the supply of energy to the water surface of a solar salt pond.

The solar spectrum can be divided into three main regions:

Anyone can feel the infrared rays emanating from a body heated to just 60 - 70 ⁰C by placing their palm from below (to eliminate thermal convection).

Bibliography

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