Solar radiation or ionizing radiation from the sun. Total solar 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- These are rays coming directly from the sun. Its intensity (effectiveness) depends on the height of the sun above the horizon: the maximum is observed at noon, and the minimum in the morning and evening; depending on the time of year: maximum - in summer, minimum - in winter; on the altitude of the area above sea level (higher in the mountains than on the plain); on the state of the atmosphere (air pollution reduces it). The spectrum of solar radiation 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- These are the rays of the sun reflected by the earth or water surface. It is expressed as a percentage of reflected rays to their total flux and is called albedo. The magnitude of the albedo depends on the nature of the reflecting 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. Some of them are characterized by selective reflectivity. Snow completely reflects infrared rays, and ultraviolet rays 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 (tiny 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 sun rays. 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 high 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 a long path, the rays encounter more obstacles and are scattered to a greater extent.

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Total solar radiation- all direct and diffuse solar radiation reaching the earth's surface. Total solar radiation is characterized by intensity. With a cloudless sky, the total solar radiation has a maximum value around noon, and throughout 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 absorbed direct and diffuse solar radiation, as well as absorbed counter radiation from the atmosphere;
- the consumable part consists of heat loss due to the earth’s own radiation.

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

Heat balance of the earth's surface- the algebraic sum of all types of heat inflow and outflow to the surface of land and ocean. The nature of the heat balance and its energy level determine the characteristics 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.

(http://www.glossary.ru/cgi-bin/gl_sch2.c gi?RQgkog.outt:p!hgrgtx!nlstup!vuilw)tux yo)

Solar radiation measurement.

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 area per unit time.

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

The intensity of solar radiation is measured using a Janiszewski 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, it is installed with a shadow screen. Direct solar radiation is calculated as the difference between total and diffuse radiation.

When determining the intensity of incident solar radiation on a fence, the pyranometer is installed on it so that the perceived surface of the device is strictly parallel to the surface of the fence. If there is no automatic recording of radiation, measurements should be taken every 30 minutes between sunrise and sunset.

Radiation incident 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 is measured by an albedometer P.K. Kalitina complete with galvanometer or potentiometer.

For greater accuracy, observations should be made under clear skies and with intense sunlight irradiating the fence.

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Solar radiation called the flow of radiant energy from the sun going to the surface of the globe. Radiant energy from the sun is the primary source of other types of energy. Absorbed by the surface of the earth and water, it is converted into thermal energy, and in green plants - into the chemical energy of organic compounds. Solar radiation is the most important climate factor and the main cause of weather changes, since various phenomena occurring in the atmosphere are associated with thermal energy received from the sun.

Solar radiation, or radiant energy, by its nature is a stream of electromagnetic oscillations propagating in a straight line at a speed of 300,000 km/sec with a wavelength from 280 nm to 30,000 nm. Radiant energy is emitted in the form of individual particles called quanta, or photons. To measure the wavelength of light, nanometers (nm), or microns, millimicrons (0.001 microns) and anstromes (0.1 millimicrons) are used. There are infrared invisible heat rays with a wavelength from 760 to 2300 nm; visible light rays (red, orange, yellow, green, cyan, indigo and violet) with wavelengths from 400 (violet) to 759 nm (red); ultraviolet, or chemical invisible, rays with a wavelength from 280 to 390 nm. Rays with a wavelength less than 280 millimicrons do not reach the earth's surface due to their absorption by ozone in high layers of the atmosphere.

At the edge of the atmosphere, the spectral composition of solar rays in percentage is as follows: infrared rays 43%, light rays 52% and ultraviolet rays 5%. At the earth's surface, at a sun altitude of 40°, solar radiation has (according to N.P. Kalitin) the following composition: infrared rays 59%, light rays 40% and ultraviolet rays 1% of the total energy. The voltage of solar radiation increases with altitude above sea level, and also when the sun's rays fall vertically, since the rays have to pass through less atmosphere. In other cases, the surface will receive less sunlight the lower the sun, or depending on the angle of incidence of the rays. The voltage of solar radiation decreases due to cloudiness, atmospheric air pollution with dust, smoke, etc.

Moreover, first of all, the loss (absorption) of short-wave rays occurs, and then heat and light. The radiant energy of the sun is the source of life on earth for plant and animal organisms and the most important factor in the surrounding air environment. It has a variety of effects on the body, which, with optimal dosage, can be very positive, and with excessive (overdose) can be negative. All rays have both thermal and chemical effects. Moreover, for rays with a long wavelength, the thermal effect comes to the fore, and with a shorter wavelength, the chemical effect comes to the fore.

The biological effect of rays on an animal’s body depends on the wavelength and their amplitude: the shorter the waves, the more frequent their oscillations, the greater the quantum energy and the stronger the body’s reaction to such irradiation. Short-wave ultraviolet rays, when exposed to tissue, cause the phenomenon of photoelectric effect in them with the appearance of detached electrons and positive ions in atoms. The depth of penetration of different rays into the body is not the same: infrared and red rays penetrate several centimeters, visible (light) rays penetrate several millimeters, and ultraviolet rays penetrate only 0.7-0.9 mm; rays shorter than 300 millimicrons penetrate animal tissue to a depth of 2 millimicrons. With such an insignificant depth of penetration of the rays, the latter have a diverse and significant effect on the entire body.

Solar radiation- a very biologically active and constantly operating factor, which is of great importance in the formation of a number of body functions. For example, through the eye, visible light rays influence the entire organism of animals, causing unconditioned and conditioned reflex reactions. Infrared heat rays exert their influence on the body both directly and through objects surrounding the animal. Animals' bodies continuously absorb and emit infrared rays (radiative exchange), and this process can vary significantly depending on the temperature of the animal's skin and surrounding objects. Ultraviolet chemical rays, the quanta of which have significantly higher energy than the quanta of visible and infrared rays, are distinguished by the greatest biological activity and act on the animal body through humoral and neuroreflex pathways. UV rays primarily act on the exteroreceptors of the skin, and then reflexively affect the internal organs, in particular the endocrine glands.

Long-term exposure to optimal doses of radiant energy leads to skin adaptation and less reactivity. Under the influence of sunlight, hair growth, the function of sweat and sebaceous glands increase, the stratum corneum thickens and the epidermis thickens, which leads to an increase in the body's skin resistance. In the skin, biologically active substances (histamine and histamine-like substances) are formed, which enter the blood. These same rays accelerate cell regeneration during the healing of wounds and ulcers on the skin. Under the influence of radiant energy, especially ultraviolet rays, the pigment melanin is formed in the basal layer of the skin, which reduces the skin's sensitivity to ultraviolet rays. Pigment (tan) is like a biological screen that facilitates the reflection and dispersion of rays.

The positive effect of sunlight affects the blood. Systematic moderate exposure to them significantly enhances hematopoiesis with a simultaneous increase in the number of erythrocytes and hemoglobin content in the peripheral blood. In animals after blood loss or who have suffered from serious illnesses, especially infectious ones, moderate exposure to sunlight stimulates blood regeneration and increases its coagulability. Moderate exposure to sunlight increases gas exchange in animals. The depth of breathing increases and the frequency of breathing decreases, the amount of oxygen introduced increases, more carbon dioxide and water vapor are released, and therefore oxygen supply to tissues improves and oxidative processes increase.

An increase in protein metabolism is expressed by increased nitrogen deposition in tissues, resulting in faster growth in young animals. Excessive solar radiation can cause a negative protein balance, especially in animals suffering from acute infectious diseases, as well as other diseases accompanied by elevated body temperature. Irradiation leads to increased deposition of sugar in the liver and muscles in the form of glycogen. The amount of under-oxidized products (acetone bodies, lactic acid, etc.) in the blood sharply decreases, the formation of acetylcholine increases and metabolism is normalized, which is especially important for highly productive animals.

In emaciated animals, the intensity of fat metabolism slows down and fat deposition increases. Intense lighting in obese animals, on the contrary, increases fat metabolism and causes increased fat burning. Therefore, it is advisable to carry out semi-fat and fat fattening of animals under conditions of less solar radiation.

Under the influence of ultraviolet rays of solar radiation, ergosterol found in food plants and dehydrocholesterol in the skin of animals are converted into active vitamins D 2 and D 3, which enhance phosphorus-calcium metabolism; the negative balance of calcium and phosphorus becomes positive, which contributes to the deposition of these salts in the bones. Sunlight and artificial irradiation with ultraviolet rays are one of the effective modern methods for the prevention and treatment of rickets and other animal diseases associated with impaired calcium and phosphorus metabolism.

Solar radiation, especially light and ultraviolet rays, is the main factor causing seasonal sexual periodicity in animals, since light stimulates the gonadotropic function of the pituitary gland and other organs. In spring, during the period of increasing intensity of solar radiation and light exposure, the secretion of the gonads, as a rule, increases in most animal species. An increase in sexual activity in camels, sheep and goats is observed with a shortening of daylight hours. If sheep are kept in darkened rooms in April-June, then they will come into estrus not in the fall (as usual), but in May. Lack of light in growing animals (during the period of growth and puberty), according to K.V. Svechin, leads to profound, often irreversible qualitative changes in the gonads, and in adult animals it reduces sexual activity and fertility or causes temporary infertility.

Visible light or the degree of illumination has a significant impact on egg development, estrus, duration of the breeding season and pregnancy. In the northern hemisphere, the breeding season is usually short, and in the southern hemisphere it is the longest. Under the influence of artificial lighting in animals, their pregnancy duration is reduced from several days to two weeks. The effect of visible light rays on the gonads can be widely used in practice. Experiments carried out in the laboratory of zoohygiene VIEV have proven that the illumination of premises at a geometric coefficient of 1: 10 (according to KEO, 1.2-2%) compared to the illumination of 1: 15-1: 20 and lower (according to KEO, 0.2 -0.5%) has a positive effect on the clinical and physiological state of pregnant sows and piglets up to 4 months of age, ensuring the production of strong and viable offspring. The weight gain of piglets increases by 6% and their safety by 10-23.9%.

Sun rays, especially ultraviolet, violet and blue, kill or weaken the viability of many pathogenic microorganisms and delay their reproduction. Thus, solar radiation is a powerful natural disinfectant of the external environment. Under the influence of sunlight, the general tone of the body and its resistance to infectious diseases increase, and specific immune reactions also increase (P. D. Komarov, A. P. Onegov, etc.). It has been proven that moderate irradiation of animals during vaccination helps to increase the titer and other immune bodies, the growth of the phagocytic index, and, conversely, intense irradiation reduces the immune properties of the blood.

From all that has been said, it follows that the lack of solar radiation must be considered as a very unfavorable external condition for animals, under which they are deprived of the most important activator of physiological processes. Taking this into account, animals should be placed in sufficiently bright rooms, exercised regularly, and kept on pasture in the summer.

Normalization of natural lighting in rooms is carried out using geometric or lighting methods. In the practice of constructing livestock and poultry buildings, the geometric method is mainly used, according to which the norms of natural lighting are determined by the ratio of the area of ​​windows (glass without frames) to the floor area. However, despite the simplicity of the geometric method, illumination standards are not established accurately using it, since in this case the light-climatic features of different geographical zones are not taken into account. To more accurately determine the illumination in rooms, use the lighting method, or determination daylight factor(KEO). The natural light factor is the ratio of room illumination (measured point) to external illumination in the horizontal plane. KEO is derived by the formula:

K = E:E n ⋅100%

Where K is the coefficient of natural light; E - indoor illumination (in lux); E n - outdoor illumination (in lux).

It must be borne in mind that excessive use of solar radiation, especially on days with high insolation, can cause significant harm to animals, in particular cause burns, eye disease, sunstroke, etc. Sensitivity to the effects of sunlight increases significantly from the introduction of so-called sensitizers (hematoporphyrin, bile pigments, chlorophyll, eosin, methylene blue, etc.). It is believed that these substances accumulate short-wave rays and convert them into long-wave rays with the absorption of part of the energy released by the tissues, as a result of which the reactivity of the tissues increases.

Sunburn in animals is most often observed on areas of the body with delicate, sparsely covered with hair, non-pigmented skin as a result of exposure to heat (solar erythema) and ultraviolet rays (photochemical inflammation of the skin). In horses, sunburn is noted on non-pigmented areas of the scalp, lips, nostrils, neck, groin and limbs, and in cattle on the skin of the udder teats and perineum. In the southern regions, sunburn is possible in white pigs.

Strong sunlight can irritate the retina, cornea and choroids of the eye and damage the lens. With prolonged and intense radiation, keratitis, clouding of the lens and impaired visual accommodation occur. Accommodation disturbances are more often observed in horses if they are kept in stables with low windows facing south, against which the horses are tied.

Sunstroke occurs as a result of severe and prolonged overheating of the brain, predominantly by thermal infrared rays. The latter penetrate through the scalp and skull, reach the brain and cause hyperemia and an increase in its temperature. As a result, the animal first appears depressed, and then excited, the respiratory and vasomotor centers are disturbed. Weakness, uncoordinated movements, shortness of breath, rapid pulse, hyperemia and cyanosis of the mucous membranes, trembling and convulsions are noted. The animal cannot stand on its feet and falls to the ground; severe cases often end in the death of the animal due to symptoms of paralysis of the heart or respiratory center. Sunstroke is especially severe if it is combined with heatstroke.

To protect animals from direct sunlight, it is necessary to keep them in the shade during the hottest hours of the day. To prevent sunstroke, particularly in working horses, they are given white canvas forehead protectors.

I was among those who liked to lie on the beach under the scorching sun. Everything was like this until I received a very severe burn. The effects of the sun on humans are not so harmless. I'll tell you more about solar radiation and what to expect from it.

What is solar radiation and what types does it exist?

We all know how important the Sun is for our planet. All the energy it emits is called solar radiation. Its path from the star itself to the Earth is very long, and therefore part of the solar energy is absorbed, and part is scattered. Solar radiation is divided into several types:

• straight;
• absent-minded;
• total;
• absorbed;
• reflected.

Direct solar radiation is that which reaches the Earth's surface in full, while scattered radiation does not penetrate the atmosphere. Together these two radiations are called total. A certain portion of the sun's heat escapes into the earth's surface. Such radiation is usually called absorbed. Some areas of the ground may reflect the sun's rays. This is where the name comes from - reflected solar radiation. Before sunrise, the total energy of the Sun. When the Sun is not very high, most of the radiation is scattered.

Impact of solar radiation on humans

The sun can both improve your health and have a detrimental effect on it. If you are exposed to sunlight too often, your risk of developing skin diseases, including cancer, increases. In addition, vision problems may appear.

Although being in the sun a lot is harmful, I would never want to live in the northern regions, where people are constantly waiting for sunny weather. Lack of sun exposure can disrupt the body's metabolism and cause excess weight. For children, lack of sunshine is also extremely undesirable.

Under normal living conditions, solar radiation maintains human health at the desired level. All organs and systems function without failures. In general, solar radiation is good in moderation, and this should always be remembered.

The blinding disk of the sun has always excited the minds of people and served as a fertile theme for legends and myths. Since ancient times, people have guessed about its impact on the Earth. How close our distant ancestors were to the truth. It is to the radiant energy of the Sun that we owe the existence of life on Earth.

What is the radioactive radiation of our star and how does it affect earthly processes?

What is solar radiation

Solar radiation is the totality of solar matter and energy entering the Earth. The energy travels in the form of electromagnetic waves at a speed of 300 thousand kilometers per second, passes through the atmosphere and reaches the Earth in 8 minutes. The range of waves participating in this “marathon” is very wide - from radio waves to x-rays, including the visible part of the spectrum. The earth's surface is under the influence of both direct and scattered solar rays from the earth's atmosphere. It is the scattering of blue-blue rays in the atmosphere that explains the blueness of the sky on a clear day. The yellow-orange color of the solar disk is due to the fact that the corresponding waves pass through almost without scattering.

With a delay of 2–3 days, the “solar wind” reaches the earth, which is a continuation of the solar corona and consists of the nuclei of atoms of light elements (hydrogen and helium), as well as electrons. It is quite natural that solar radiation has a strong effect on the human body.

The influence of solar radiation on the human body

The electromagnetic spectrum of solar radiation consists of infrared, visible and ultraviolet parts. Since their quanta have different energies, they have a varied effect on a person.

indoor lighting

The hygienic significance of solar radiation is also extremely high. Since visible light is a decisive factor in obtaining information about the outside world, it is necessary to provide a sufficient level of illumination in the room. Its regulation is carried out in accordance with SNiP, which for solar radiation are drawn up taking into account the light and climatic characteristics of various geographical zones and are taken into account when designing and constructing various facilities.

Even a superficial analysis of the electromagnetic spectrum of solar radiation proves how great the influence of this type of radiation on the human body is.

Distribution of solar radiation over the Earth's territory

Not all radiation coming from the Sun reaches the surface of the earth. And there are many reasons for this. The Earth steadfastly repels the attack of those rays that are destructive to its biosphere. This function is performed by the ozone shield of our planet, preventing the passage of the most aggressive part of ultraviolet radiation. An atmospheric filter in the form of water vapor, carbon dioxide, and dust particles suspended in the air largely reflects, scatters and absorbs solar radiation.

That part of it that has overcome all these obstacles falls to the surface of the earth at different angles, depending on the latitude of the area. The life-giving heat of the sun is distributed unevenly across the territory of our planet. As the height of the sun changes throughout the year above the horizon, the mass of air through which the path of the sun's rays passes changes. All this affects the distribution of solar radiation intensity across the planet. The general tendency is this: this parameter increases from the pole to the equator, since the greater the angle of incidence of the rays, the more heat falls per unit area.

Solar radiation maps allow you to have a picture of the distribution of solar radiation intensity over the Earth's territory.

The influence of solar radiation on the Earth's climate

The infrared component of solar radiation has a decisive influence on the Earth's climate.

It is clear that this only happens when the Sun is above the horizon. This influence depends on the distance of our planet from the Sun, which changes throughout the year. The Earth's orbit is an ellipse, within which the Sun is located. Making its annual journey around the Sun, the Earth either moves away from its luminary or approaches it.

In addition to the change in distance, the amount of radiation reaching the earth is determined by the inclination of the earth's axis to the orbital plane (66.5°) and the change of seasons caused by it. In summer it is greater than in winter. At the equator this factor does not exist, but as the latitude of the observation site increases, the gap between summer and winter becomes significant.

In the processes occurring on the Sun, all kinds of cataclysms take place. Their impact is partly offset by enormous distances, the protective properties of the earth's atmosphere and the earth's magnetic field.

How to protect yourself from solar radiation

The infrared component of solar radiation is the coveted warmth that residents of middle and northern latitudes look forward to during all other seasons of the year. Solar radiation as a health factor is used by both healthy and sick people.

However, we must not forget that heat, like ultraviolet radiation, is a very strong irritant. Abuse of their effects can lead to burns, general overheating of the body, and even exacerbation of chronic diseases. When sunbathing, you should adhere to life-tested rules. You should be especially careful when sunbathing on clear sunny days. Infants and elderly people, patients with chronic tuberculosis and problems with the cardiovascular system should be content with diffuse solar radiation in the shade. This ultraviolet light is quite enough to meet the needs of the body.

Even young people who do not have any special health problems should be protected from solar radiation.

Now a movement has emerged whose activists oppose tanning. And not in vain. Tanned skin is undoubtedly beautiful. But the melanin produced by the body (what we call tanning) is its protective reaction to exposure to solar radiation. There are no benefits from tanning! There is even evidence that tanning shortens life, since radiation has a cumulative property - it accumulates throughout life.

If the situation is so serious, you should scrupulously follow the rules prescribing how to protect yourself from solar radiation:

• strictly limit the time for tanning and do it only during safe hours;
• when in the active sun, you should wear a wide-brimmed hat, closed clothing, sunglasses and an umbrella;
• Use only high-quality sunscreen.

Is solar radiation dangerous for humans at all times of the year? The amount of solar radiation reaching the earth is associated with the change of seasons. At mid-latitudes in summer it is 25% more than in winter. There is no difference at the equator, but as the latitude of the observation site increases, this difference increases. This is due to the fact that our planet is tilted at an angle of 23.3 degrees in relation to the sun. In winter, it is low above the horizon and illuminates the ground only with sliding rays, which heat up the illuminated surface less. This position of the rays causes them to be distributed over a larger surface, which reduces their intensity compared to the summer sheer drop. In addition, the presence of an acute angle when rays pass through the atmosphere “lengthens” their path, causing them to lose more heat. This circumstance reduces the impact of solar radiation in winter.

The sun is a star that is a source of heat and light for our planet. It “controls” the climate, the change of seasons and the state of the entire biosphere of the Earth. And only knowledge of the laws of this powerful influence will allow us to use this life-giving gift for the benefit of people's health.

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

On the Sun, the thermal energy of 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.

Solar radiation intensity. Solar constant. Solar radiation is the most important source of heat for the geographic 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 shell there is one type of energy ( radiant energy ) equivalently goes into 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, since when passing through the air sphere it is transformed and weakened. The intensity of solar radiation is expressed by the solar constant.

Solar constant - this is the flow of solar energy in 1 minute onto 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 portion of radiation, it is important to know its magnitude at the upper boundary of the geographic envelope, i.e., in the lower stratosphere. Solar radiation at the upper boundary of the geographic envelope is expressed conventional solar constant . The value of the conventional 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 changes in the distance from the Sun to the Earth as the Earth moves along its orbit. No matter how small these fluctuations are, they always affect the weather and climate.

On average, each square kilometer of 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 of coal. The entire Earth receives an amount of heat per year that is determined by the value 5.74 x 10 24 J (1.37 x 10 24 cal).

Distribution of solar radiation “at the upper boundary of the atmosphere” or with an absolutely transparent atmosphere. Knowledge of the distribution of solar radiation before it enters the atmosphere, or the so-called solar (sunny) climate , is important for determining the role and share of participation of the Earth’s air shell itself (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 received per unit area is determined, firstly, by the angle of incidence of the rays, depending on the height of the Sun above the horizon, and secondly, by the length of the day.

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

In the absence of an atmosphere, the annual amount of radiation at equatorial latitudes would be 13,480 MJ/cm2 (322 kcal/cm2), and at the poles 5,560 MJ/m2 (133 kcal/cm2). To the polar latitudes, the Sun sends heat slightly less than half (about 42%) of the amount that arrives at the equator.

It would seem that the solar irradiation of the Earth is symmetrical relative to the equatorial plane. But this happens only twice a year, on the days of the spring and autumn equinox. The tilt of the rotation axis 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, and in the July part, the northern hemisphere receives more heat. This is precisely the main reason for the seasonal rhythm in the geographical envelope.

The difference between the equator and the pole of the summer hemisphere is small: the equator receives 6,740 MJ/m2 (161 kcal/cm2), and the pole receives about 5,560 MJ/m2 (133 kcal/cm2 per half-year). But the polar countries of the winter hemisphere at the same time are completely deprived of solar heat and light.

On the day of the solstice, the pole receives even more heat than the equator - 46.0 MJ/m2 (1.1 kcal/cm2) and 33.9 MJ/m2 (0.81 kcal/cm2).

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

The actual 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 absorption of solar radiation by the earth’s surface in different geographical conditions.

Changes in solar radiation as it passes through the atmosphere. Direct sunlight penetrating the atmosphere under a cloudless sky is called direct solar radiation . Its maximum value with high transparency of the atmosphere on a surface perpendicular to the rays in the tropical zone is about 1.05 - 1.19 kW/m 2 (1.5 - 1.7 cal/cm 2 x min. In mid-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.

Some of the sun's rays from contact with gas molecules and aerosols are scattered and become scattered radiation . Scattered radiation no longer comes to the earth's surface from the solar disk, but from the entire sky and creates widespread daylight. It makes it light on sunny days and where direct rays do not penetrate, for example under the forest canopy. Along with direct radiation, diffuse radiation also serves as a source of heat and light.

The more intense the direct line, the greater the absolute value of scattered radiation. The relative importance of scattered radiation increases with the decreasing role of direct radiation: in mid-latitudes in summer it makes up 41%, and in winter 73% of the total radiation arrival. The share of scattered radiation in the total amount of total radiation also depends on the height of the Sun. At high latitudes, scattered radiation accounts for about 30%, and at polar latitudes it accounts for approximately 70% of all radiation.

In general, scattered radiation accounts for about 25% of the total flux of solar rays arriving on our planet.

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

By absorbing and scattering radiation, the atmosphere significantly weakens it. Attenuation amount depends on transparency coefficient, showing what proportion of 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 transmit about 90% of the radiation reaching 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 with the weather.

Since the density of air decreases with height, the layer of gas penetrated by the rays should not be expressed in km of atmospheric thickness. The unit of measurement adopted 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 weakens so much that one can look at the Sun with an unprotected eye. As the Sun rises, 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 Lambert's formula :

I i = I 0 p m , where

I i – radiation reaching the earth’s surface,

I 0 – solar constant,

p – transparency coefficient,

m is the number of optical masses.

Solar radiation at the earth's surface. The amount of radiant energy per unit of the earth's surface depends, first of all, on the angle of incidence of the sun's rays. Equal areas at the equator and in the middle and high latitudes receive different amounts of radiation.

Solar insolation (lighting) is greatly reduced cloudiness. Large clouds at equatorial and temperate latitudes and low clouds at tropical latitudes make significant adjustments to the zonal distribution of solar radiant energy.

The distribution of solar heat over the earth's surface is depicted on maps of total solar radiation. As these maps show, tropical latitudes receive the greatest amount of solar heat - from 7,530 to 9,200 MJ/m2 (180-220 kcal/cm2). Equatorial latitudes, due to heavy cloudiness, receive slightly less heat: 4,185 – 5,860 MJ/m2 (100-140 kcal/cm2).

From tropical to temperate latitudes, radiation decreases. On the Arctic islands it is no more than 2,510 MJ/m2 (60 kcal/cm2) per year. The distribution of radiation over the earth's surface has a zonal-regional character. Each zone is divided into separate areas (regions), slightly different from each other.

Seasonal fluctuations in total radiation.

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

In the temperate zone In the annual course of radiation, the summer maximum is clearly pronounced, in which the monthly value of total radiation is not less than the tropical value. The number of warm months decreases with latitude.

In the polar zones 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 lighting here is continuous, which significantly increases the amount of monthly radiation.

Assimilation of radiation by the earth's surface. Albedo. The total radiation that reaches the earth's surface is partially absorbed by 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).