Sun radiation. The concept of solar radiation

The bright luminary burns us with hot rays and makes us think about the significance of radiation in our life, its benefits and harms. What is solar radiation? The lesson of school physics invites us to get acquainted with the concept of electromagnetic radiation in general. This term refers to another form of matter - different from substance. This also includes visible light, and a spectrum that is not perceived by the eye. That is, x-rays, gamma rays, ultraviolet and infrared.

Electromagnetic waves

In the presence of a source-emitter of radiation, its electromagnetic waves propagate in all directions at the speed of light. These waves, like any other, have certain characteristics. These include the oscillation frequency and wavelength. Any body whose temperature differs from absolute zero has the property to emit radiation.

The sun is the main and most powerful source of radiation near our planet. In turn, the Earth (its atmosphere and surface) itself emits radiation, but in a different range. Watching temperature conditions on the planet for long periods of time gave rise to a hypothesis about the balance of the amount of heat received from the Sun and given off into outer space.

Solar radiation: spectral composition

The vast majority (about 99%) of the solar energy in the spectrum lies in the wavelength range from 0.1 to 4 microns. The remaining 1% is longer and shorter rays, including radio waves and x-rays. About half of the radiant energy of the sun falls on the spectrum that we perceive with our eyes, approximately 44% - in infrared radiation, 9% - in ultraviolet. How do we know how solar radiation is divided? The calculation of its distribution is possible thanks to research from space satellites.

There are substances that can special condition and emit additional radiation of a different wave range. For example, there is a glow at low temperatures that are not characteristic of the emission of light by a given substance. This type of radiation, called luminescent, does not lend itself to the usual principles of thermal radiation.

The phenomenon of luminescence occurs after the absorption of a certain amount of energy by the substance and the transition to another state (the so-called excited state), which is higher in energy than at the substance's own temperature. Luminescence appears during the reverse transition - from an excited to a familiar state. In nature, we can observe it in the form of night sky glows and aurora.

Our luminary

The energy of the sun's rays is almost the only source of heat for our planet. Its own radiation, coming from its depths to the surface, has an intensity that is about 5 thousand times less. At the same time, visible light - one of the most important factors of life on the planet - is only a part of solar radiation.

The energy of the sun's rays is converted into heat by a smaller part - in the atmosphere, a larger one - on the surface of the Earth. There it is spent on heating water and soil ( upper layers), which then release heat to the air. Being heated, the atmosphere and the earth's surface, in turn, emit infrared rays into space, while cooling.

Solar radiation: definition

The radiation that comes to the surface of our planet directly from the solar disk is commonly referred to as direct solar radiation. The sun spreads it in all directions. Given the vast distance from the Earth to the Sun, direct solar radiation at any point earth's surface can be represented as a beam of parallel rays, the source of which is practically in infinity. The area perpendicular to the rays sunlight, thus receives the greatest amount of it.

Radiation flux density (or irradiance) is a measure of the amount of radiation incident on a particular surface. This is the amount of radiant energy falling per unit time per unit area. This value is measured - energy illumination - in W / m 2. Our Earth, as everyone knows, revolves around the Sun in an ellipsoidal orbit. The sun is at one of the foci of this ellipse. Therefore, every year at a certain time (at the beginning of January) the Earth occupies a position closest to the Sun and at another (at the beginning of July) - farthest from it. In this case, the magnitude of the energy illumination varies in inverse proportion with respect to the square of the distance to the luminary.

Where does the solar radiation that reaches the Earth go? Its types are determined by many factors. Depending on the geographic latitude, humidity, cloudiness, part of it is dissipated in the atmosphere, part is absorbed, but most still reaches the surface of the planet. In this case, a small amount is reflected, and the main one is absorbed by the earth's surface, under the influence of which it is heated. Scattered solar radiation also partially falls on the earth's surface, is partially absorbed by it and partially reflected. The rest of it goes into outer space.

How is the distribution

Is solar radiation homogeneous? Its types after all "losses" in the atmosphere can differ in their spectral composition. After all, rays with different lengths are scattered and absorbed differently. On average, about 23% of its initial amount is absorbed by the atmosphere. Approximately 26% of the total flux is converted into diffuse radiation, 2/3 of which then falls on the Earth. In essence, this is a different type of radiation, different from the original. Scattered radiation is sent to Earth not by the disk of the Sun, but by the vault of heaven. It has a different spectral composition.

Absorbs radiation mainly ozone - the visible spectrum, and ultraviolet rays. Infrared radiation is absorbed carbon dioxide(carbon dioxide), which, by the way, is very little in the atmosphere.

Scattering of radiation, weakening it, occurs for any wavelength of the spectrum. In the process, its particles, falling under electromagnetic influence, redistribute the energy of the incident wave in all directions. That is, the particles serve as point sources of energy.

Daylight

Due to scattering, the light coming from the sun changes color when passing through the layers of the atmosphere. Practical value scattering - in the making daylight. If the Earth were devoid of an atmosphere, illumination would exist only in places where direct or reflected rays of the sun hit the surface. That is, the atmosphere is the source of illumination during the day. Thanks to it, it is light both in places inaccessible to direct rays, and when the sun is hidden behind clouds. It is scattering that gives color to the air - we see the sky blue.

What else influences solar radiation? The turbidity factor should not be discounted either. After all, the weakening of radiation occurs in two ways - the atmosphere itself and water vapor, as well as various impurities. The level of dust increases in summer (as does the content of water vapor in the atmosphere).

Total radiation

It means total radiation falling on the earth's surface, both direct and diffuse. The total solar radiation decreases in cloudy weather.

For this reason, in summer, the total radiation is on average higher before noon than after it. And in the first half of the year - more than in the second.

What happens to the total radiation on the earth's surface? Getting there, it is mostly absorbed by the upper layer of soil or water and turns into heat, part of it is reflected. The degree of reflection depends on the nature of the earth's surface. The indicator expressing the percentage of reflected solar radiation to its total amount falling on the surface is called the surface albedo.

The concept of self-radiation of the earth's surface is understood as long-wave radiation emitted by vegetation, snow cover, upper layers water and soil. The radiation balance of a surface is the difference between its amount absorbed and emitted.

Effective Radiation

It is proved that the counter radiation is almost always less than the terrestrial one. Because of this, the surface of the earth bears heat losses. The difference between the intrinsic radiation of the surface and the atmospheric radiation is called the effective radiation. This is actually a net loss of energy and, as a result, heat at night.

It also exists during the daytime. But during the day it is partially compensated or even blocked by absorbed radiation. Therefore, the surface of the earth is warmer during the day than at night.

On the geographical distribution of radiation

Solar radiation on Earth during the year is distributed unevenly. Its distribution has a zonal character, and the isolines (connecting points of equal values) of the radiation flux are by no means identical to the latitudinal circles. This discrepancy is caused by different levels of cloudiness and transparency of the atmosphere in different regions. globe.

The total solar radiation during the year has the highest value in subtropical deserts with cloudy atmosphere. It is much less in forest areas equatorial belt. The reason for this is increased cloudiness. This indicator decreases towards both poles. But in the region of the poles it increases again - in the northern hemisphere it is less, in the region of snowy and slightly cloudy Antarctica - more. Above the surface of the oceans, on average, solar radiation is less than over the continents.

Almost everywhere on Earth, the surface has a positive radiation balance, that is, for the same time, the influx of radiation is greater than the effective radiation. The exceptions are the regions of Antarctica and Greenland with their ice plateaus.

Are we facing global warming?

But the above does not mean the annual warming of the earth's surface. The excess of absorbed radiation is compensated by heat leakage from the surface into the atmosphere, which occurs when the water phase changes (evaporation, condensation in the form of clouds).

Thus, there is no radiation equilibrium as such on the Earth's surface. But there is a thermal equilibrium - the inflow and loss of heat is balanced in different ways, including radiation.

Card balance distribution

In the same latitudes of the globe, the radiation balance is greater on the surface of the ocean than over land. This can be explained by the fact that the layer that absorbs radiation in the oceans has a large thickness, while at the same time, the effective radiation there is less due to the cold of the sea surface compared to land.

Significant fluctuations in the amplitude of its distribution are observed in deserts. The balance is lower there due to the high effective radiation in dry air and low cloud cover. It is lowered to a lesser extent in areas monsoon climate. In the warm season, the cloudiness there is increased, and the absorbed solar radiation is less than in other regions of the same latitude.

Of course, the main factor on which the average annual solar radiation depends is the latitude of a particular area. Record "portions" of ultraviolet go to countries located near the equator. This is North East Africa, East Coast, Arabian Peninsula, north and west of Australia, part of the islands of Indonesia, Western part coasts of South America.

In Europe, Turkey, the south of Spain, Sicily, Sardinia, the islands of Greece, the coast of France ( southern part), as well as part of the regions of Italy, Cyprus and Crete.

How about us?

Solar total radiation in Russia is distributed, at first glance, unexpectedly. On the territory of our country, oddly enough, not at all Black Sea resorts hold the palm. The largest doses of solar radiation fall on the territories bordering China and Severnaya Zemlya. In general, solar radiation in Russia is not particularly intense, which is fully explained by our northern geographic location. The minimum amount of sunlight goes to the northwestern region - St. Petersburg, together with the surrounding areas.

Solar radiation in Russia is inferior to Ukraine. There, the most ultraviolet radiation goes to the Crimea and territories beyond the Danube, in second place is the Carpathians with southern regions Ukraine.

The total (it includes both direct and scattered) solar radiation falling on a horizontal surface is given by months in specially designed tables for different territories and is measured in MJ / m 2. For example, solar radiation in Moscow ranges from 31-58 in the winter months to 568-615 in the summer.

About solar insolation

Insolation, or volume useful radiation, falling on the surface illuminated by the sun, varies significantly in different geographical points. Annual insolation is calculated per square meter in megawatts. For example, in Moscow this value is 1.01, in Arkhangelsk - 0.85, in Astrakhan - 1.38 MW.

When determining it, it is necessary to take into account such factors as the time of year (in winter, the illumination and longitude of the day are lower), the nature of the terrain (mountains can block the sun), characteristic of the area weather- fog, frequent rains and cloudiness. The light-receiving plane can be oriented vertically, horizontally or obliquely. The amount of insolation, as well as the distribution of solar radiation in Russia, is a data grouped in a table by city and region, indicating the geographical latitude.

The sun is a source of heat and light, giving strength and health. However, its impact is not always positive. Lack of energy or its excess can upset the natural processes of life and provoke various problems. Many people believe that tanned skin looks much more beautiful than pale, but if for a long time held under direct rays, you can get a severe burn. Solar radiation is a stream of incoming energy propagating in the form of electromagnetic waves passing through the atmosphere. It is measured by the power of the energy transferred by it per unit surface area (watt / m 2). Knowing how the sun affects a person, you can prevent its negative impact.

What is solar radiation

Many books have been written about the Sun and its energy. The sun is the main source of energy for all physical and geographical phenomena on Earth. One two-billionth of the light penetrates into the upper layers of the planet's atmosphere, while the greater part settles in world space.

Rays of light are the primary sources of other types of energy. Getting on the surface of the earth and into the water, they are formed into heat, affect climatic features and the weather.

The degree of exposure to light rays on a person depends on the level of radiation, as well as the period spent under the sun. People use many types of waves to their advantage, using x-rays, infrared rays, and ultraviolet light. However, solar waves in their pure form in large quantities can adversely affect human health.

The amount of radiation depends on:

• position of the sun. The largest number exposure occurs in the plains and deserts, where the solstice is quite high, and the weather is cloudless. The polar regions receive the minimum amount of light, since cloud cover absorbs a significant part of the light flux;
• day length. The closer to the equator, the longer the day. It is there that people get more heat;
• atmospheric properties: cloudiness and humidity. At the equator, increased cloudiness and humidity, which is an obstacle to the passage of light. That is why the amount of light flux there is less than in tropical areas.

Distribution

The distribution of sunlight over the earth's surface is uneven and depends on:

• density and humidity of the atmosphere. The larger they are, the less exposure;
• geographic latitude of the area. The amount of light received rises from the poles to the equator;
• the movements of the earth. The amount of radiation varies depending on the time of year;
• characteristics of the earth's surface. A large amount of light flux is reflected in light surfaces, such as snow. Chernozem reflects the light energy most weakly.

Due to the extent of its territory, the level of radiation in Russia varies considerably. Solar exposure in the northern regions is approximately the same - 810 kWh / m 2 for 365 days, in the south - more than 4100 kWh / m 2.

Of no small importance is the length of hours during which the sun shines.. These figures are different in different regions, which is influenced not only by geographical latitude, but also by the presence of mountains. On the map of solar radiation in Russia, it is clearly seen that in some regions it is not advisable to install power lines, since natural light is quite capable of providing residents with electricity and heat.

Kinds

Light streams reach the Earth in various ways. It is on this that the types of solar radiation depend:

• The rays from the sun are called direct radiation.. Their strength depends on the height of the sun above the horizon. Max level observed at 12 noon, the minimum - in the morning and evening. In addition, the impact intensity is related to the time of year: the highest occurs in summer, the lowest in winter. It is characteristic that in the mountains the level of radiation is higher than on flat surfaces. Also, dirty air reduces direct light fluxes. The lower the sun above the horizon, the less ultraviolet.
• Reflected radiation is radiation that is reflected by water or the surface of the earth.
• Scattered solar radiation is formed when the light flux is scattered. The blue color of the sky in cloudless weather depends on it.

Absorbed solar radiation depends on the reflectivity of the earth's surface - albedo.

The spectral composition of radiation is diverse:

• colored or visible rays give illumination and have great importance in plant life;
• ultraviolet should penetrate the human body moderately, since its excess or lack can be harmful;
• infrared irradiation gives a feeling of warmth and affects the growth of vegetation.

Total solar radiation is direct and scattered rays penetrating the earth.. In the absence of clouds, at about 12 noon, and also in summer time year it reaches its maximum.

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How does the impact

Electromagnetic waves are made up of different parts. There are invisible, infrared and visible, ultraviolet rays. Characteristically, radiation fluxes have a different energy structure and affect people in different ways.

The light flux can have a beneficial, healing effect on the condition of the human body. Passing through the visual organs, light regulates metabolism, sleep patterns, and affects the general well-being of a person. In addition, light energy can cause a feeling of warmth. When the skin is irradiated, photochemical reactions occur in the body that contribute to the proper metabolism.

Ultraviolet has a high biological ability, having a wavelength of 290 to 315 nm. These waves synthesize vitamin D in the body, and are also capable of destroying the tuberculosis virus in a few minutes, staphylococcus - within a quarter of an hour, typhoid fever bacilli - in 1 hour.

Characteristically, cloudless weather reduces the duration of emerging epidemics of influenza and other diseases, such as diphtheria, which have the ability to be transmitted by airborne droplets.

The natural forces of the body protect a person from sudden atmospheric fluctuations: air temperature, humidity, pressure. However, sometimes such protection is weakened, which, under the influence of high humidity, together with increased temperature, leads to thermal shock.

Exposure to radiation is related to the degree of its penetration into the body. The longer the waves, the stronger force radiation. Infrared waves are able to penetrate up to 23 cm under the skin, visible streams - up to 1 cm, ultraviolet - up to 0.5-1 mm.

All types of rays people receive during the activity of the sun, when they stay on open spaces. Light waves allow a person to adapt to the world, which is why in order to ensure comfortable well-being in rooms, it is necessary to create conditions for an optimal level of lighting.

Human impact

The impact of solar radiation on human health is determined various factors. The place of residence of a person, the climate, as well as the amount of time spent under direct rays matter.

With a lack of sun, residents of the Far North, as well as people whose activities are related to working underground, such as miners, experience various life disorders, bone strength decreases, and nervous disorders occur.

Children who receive less light suffer from rickets more often than others. In addition, they are more susceptible to dental diseases, and also have a longer course of tuberculosis.

However, too long exposure to light waves without a periodic change of day and night can be detrimental to health. For example, residents of the Arctic often suffer from irritability, fatigue, insomnia, depression, and decreased ability to work.

Radiation in the Russian Federation is less active than, for example, in Australia.

Thus, people who are under long-term radiation:

• are at high risk of developing skin cancer;
• have an increased tendency to dry skin, which in turn accelerates the aging process and the appearance of pigmentation and early wrinkles;
• may suffer from visual impairment, cataracts, conjunctivitis;
• have a weakened immune system.

Lack of vitamin D in humans is one of the causes of malignant neoplasms, metabolic disorders, which leads to overweight, endocrine disorders, sleep disturbances, physical exhaustion, bad mood.

A person who systematically receives the light of the sun and does not abuse sunbathing, as a rule, does not experience health problems:

• has a stable work of the heart and blood vessels;
• does not suffer from nervous diseases;
• has a good mood;
• has a normal metabolism;
• rarely gets sick.

Thus, only a dosed intake of radiation can positively affect human health.

How to protect yourself

An excess of radiation can provoke overheating of the body, burns, as well as exacerbation of some chronic diseases.. Fans of sunbathing need to take care of the implementation of simple rules:

• sunbathe in open spaces with caution;
• during hot weather, hide in the shade under scattered rays. This is especially true for young children and older people with tuberculosis and heart disease.

It should be remembered that it is necessary to sunbathe at a safe time of day, and also not to be under the scorching sun for a long time. In addition, it is worth protecting your head from heatstroke by wearing a hat, Sunglasses, closed clothing, and use various sunscreens.

Solar radiation in medicine

Light fluxes are actively used in medicine:

• X-rays use the ability of waves to pass through soft tissues and the skeletal system;
• the introduction of isotopes allows you to fix their concentration in the internal organs, to detect many pathologies and foci of inflammation;
• radiation therapy can destroy the growth and development of malignant neoplasms.

The properties of waves are successfully used in many physiotherapy devices:

• Devices with infrared radiation used for heat treatment of internal inflammatory processes, bone diseases, osteochondrosis, rheumatism, due to the ability of waves to restore cellular structures.
• Ultraviolet rays can adversely affect living beings, inhibit plant growth, suppress microorganisms and viruses.

The hygienic value of solar radiation is great. Devices with ultraviolet radiation are used in therapy:

• various injuries of the skin: wounds, burns;
• infections;
• diseases of the oral cavity;
• oncological neoplasms.

In addition, radiation is positive influence on the human body as a whole: it is able to give strength, strengthen the immune system, make up for the lack of vitamins.

Sunlight is an important source of full human life. Sufficient intake of it leads to a favorable existence of all living beings on the planet. A person cannot reduce the degree of radiation, but he can protect himself from its negative effects.

shortwave radiation from the sun

Ultraviolet and X-rays come mainly from the upper layers of the chromosphere and the corona. This was established by launching rockets with instruments during solar eclipses. The very hot solar atmosphere always emits invisible short-wave radiation, but it is especially powerful during the years of maximum solar activity. At this time, ultraviolet radiation increases by about a factor of two, and X-ray radiation by tens and hundreds of times compared to the radiation in years of minimum. The intensity of shortwave radiation varies from day to day, increasing sharply when flares occur.

Ultraviolet and X-ray radiation partially ionize the layers of the earth's atmosphere, forming the ionosphere at altitudes of 200-500 km from the Earth's surface. The ionosphere is playing important role in the implementation of long-range radio communications: radio waves coming from a radio transmitter, before reaching the receiver antenna, are repeatedly reflected from the ionosphere and the Earth's surface. The state of the ionosphere varies depending on the conditions of its illumination by the Sun and on the phenomena occurring on it. Therefore, to ensure stable radio communication, it is necessary to take into account the time of day, season and the state of solar activity. After the most powerful solar flares, the number of ionized atoms in the ionosphere increases and radio waves are partially or completely absorbed by it. This leads to deterioration and even to a temporary cessation of radio communications.

Scientists pay special attention to the study of the ozone layer in the earth's atmosphere. Ozone is formed as a result of photochemical reactions (absorption of light by oxygen molecules) in the stratosphere, and its bulk is concentrated there. In total, there are approximately 3 10 9 tons of ozone in the earth's atmosphere. This is very small: the thickness of the pure ozone layer near the Earth's surface would not exceed 3 mm! But the role of the ozone layer, which extends at a height of several tens of kilometers above the Earth's surface, is exceptionally great, because it protects all living things from the effects of dangerous short-wave (and, above all, ultraviolet) radiation from the Sun. The ozone content is not constant at different latitudes and in different times of the year. It can decrease (sometimes very significantly) as a result of various processes. This can be facilitated, for example, by emissions into the atmosphere a large number ozone-depleting chlorine-containing substances of industrial origin or aerosol emissions, as well as emissions accompanying volcanic eruptions. Areas of sharp ozone depletion (“ozone holes”) have been found above different regions of our planet, and not only over Antarctica and a number of other territories of the Southern Hemisphere of the Earth, but also over the Northern Hemisphere. In 1992, alarming reports began to appear of temporary depletion of the ozone layer over northern European Russia and a decrease in ozone over Moscow and St. Petersburg. Scientists, realizing global character problems, organize environmental research on a global scale, including primarily a global system of continuous monitoring of the state of the ozone layer. Designed and signed international agreements to protect the ozone layer and limit the production of ozone-depleting substances.

Sun radio emission

A systematic study of the radio emission of the Sun began only after the Second World War, when it was discovered that the Sun is a powerful source of radio emission. Radio waves penetrate into interplanetary space, which are emitted by the chromosphere (centimeter waves) and the corona (decimeter and meter waves). This radio emission reaches the Earth. The radio emission of the Sun has two components - a constant, almost unchanged in intensity, and a variable (bursts, "noise storms").

The radio emission of the quiet Sun is explained by the fact that hot solar plasma always emits radio waves along with electromagnetic oscillations of other wavelengths (thermal radio emission). During large flares, the radio emission from the Sun increases by thousands and even millions of times compared to the radio emission from the quiet Sun. This radio emission, generated by fast non-stationary processes, has a non-thermal nature.

Corpuscular radiation of the Sun

A number of geophysical phenomena ( magnetic storms, i.e. short-term changes in the Earth's magnetic field, auroras, etc.) is also associated with solar activity. But these phenomena occur a day after solar flares. They are caused not by electromagnetic radiation reaching the Earth after 8.3 minutes, but by corpuscles (protons and electrons forming a rarefied plasma), which penetrate the near-Earth space with a delay (by 1-2 days), since they move at speeds of 400 - 1000 km /c.

Corpuscles are emitted by the Sun even when there are no flashes and spots on it. The solar corona is the source of a constant outflow of plasma (solar wind) that occurs in all directions. The solar wind, created by the continuously expanding corona, envelops the planets moving near the Sun and . Flares are accompanied by "gusts" of the solar wind. Experiments at interplanetary stations and artificial satellites The Earth made it possible to directly detect the solar wind in interplanetary space. During flares and during a calm outflow of the solar wind, not only corpuscles but also the magnetic field associated with the moving plasma penetrate into interplanetary space.

All types of solar rays reach the earth's surface in three ways - in the form of direct, reflected and diffuse solar radiation.
direct solar radiation are rays coming directly from the sun. Its intensity (efficiency) depends on the height of the sun above the horizon: the maximum is observed at noon, and the minimum - in the morning and evening; from the time of year: maximum - in summer, minimum - in winter; from the height of the terrain above sea level (higher in the mountains than on the plain); on the state of the atmosphere (air pollution reduces it). The spectrum of solar radiation also depends on the height of the sun above the horizon (the lower the sun is above the horizon, the less ultraviolet rays).
reflected solar radiation- These are the rays of the sun reflected by the earth or water surface. It is expressed as the percentage of reflected rays to their total flux and is called albedo. The albedo value depends on the nature of the reflective surfaces. When organizing and conducting sunbathing, it is necessary to know and take into account the albedo of the surfaces on which sunbathing is carried out. 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 (the smallest droplets of water, ice crystals, etc.), called aerosols, reflect part of the rays. As a result of multiple reflections, some of them still reach the earth's surface; These are scattered rays of the sun. Mostly ultraviolet, violet and blue rays are scattered, which determines the blue color of the sky in clear weather. Specific gravity scattered rays is large at high latitudes (in the northern regions). There the sun is low above the horizon, and therefore the path of the rays to the earth's surface is longer. On a long path, the rays meet more obstacles and scatter to a greater extent.

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

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

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

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

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

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

Measurement of solar radiation.

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

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

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

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

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

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

For greater accuracy, the observation should be carried out at clear sky and with intense solar irradiation fencing.

(http://www.constructioncheck.ru/default.a spx?textpage=5)

Solar radiation, which includes electromagnetic wavelengths less than 4 μm1, is usually called short-wave radiation in meteorology. In the solar spectrum, ultraviolet (< 400 нм), видимую (= 400…760 нм) и инфракрасную (>760 nm) parts.

Solar radiation coming directly from the solar disk is called direct solar radiation S. It is usually characterized by intensity, i.e., the amount of radiant energy in calories passing in 1 minute through 1 cm2 of an area located perpendicular to the sun's rays.

The intensity of direct solar radiation entering the upper boundary of the earth's atmosphere is called the solar constant S 0 . It is approximately 2 cal/cm2 min. At the earth's surface, direct solar radiation is always much less than this value, since, passing through the atmosphere, its solar energy weakened due to absorption and scattering by air molecules and suspended particles (dust grains, droplets, crystals). The attenuation of direct solar radiation by the atmosphere is characterized by either the attenuation coefficient a or the transparency coefficient sp.

To calculate the direct solar radiation falling on a perpendicular surface, the Bouguer formula is usually used:

where S m is direct solar radiation, cal cm-2 min-1, at a given mass of the atmosphere; S 0 is the solar constant; p t is the transparency coefficient for a given mass of the atmosphere;

sa is not according to the formula, but according to the Bemporada table. From formula (3.1) it follows that

1 1 µm = 10-3 nm = 10-6 m. Micrometers are also called microns, and nanometers are called millimicrons. 1 nm = 10-9 m.

where h is the height of the sun above the horizon.

The radiation arriving at the earth's surface from all points of the firmament is called scattered D. The sum of direct and diffuse solar radiation arriving at the horizontal earth's surface is the total solar radiation Q:

Q = S" + D.(3.4)

The total radiation that has reached the earth's surface, partially reflected from it, creates reflected radiation R directed from the earth's surface into the atmosphere. The rest of the total solar radiation is absorbed by the earth's surface. The ratio of the radiation reflected from the earth's surface to the incoming total radiation is called albedoA.

The value of A R characterizes the reflectivity of the earth

surface. It is expressed as a fraction of a unit or a percentage. The difference between the total and reflected radiation is called absorbed radiation, or the balance of short-wave radiation of the earth's surface B to:

The surface of the earth and the earth's atmosphere, like all bodies with a temperature above absolute zero, also emit radiation, which is conventionally called long-wave radiation. Its wavelengths are about

4 to 100 µm.

Self-radiation of the earth's surface, according to the Stefan-Boltzmann law, is proportional to the fourth power of its absolute temperature

where = 0.814 10-10 cal/cm2 min deg4 Stefan-Boltzmann constant; relative emissivity of the active surface: for most natural surfaces 0.95.

Atmospheric radiation is directed both to the Earth and to the world space. The part of the long-wave atmospheric radiation directed downward and reaching the earth's surface is called the counter-radiation of the atmosphere and is denoted by E a.

The difference between the natural radiation of the earth's surface E s and the counter radiation of the atmosphere E a is called the effective radiation

The value of E eff taken from opposite sign, is the balance of long-wave radiation on the earth's surface.

The difference between all incoming and all outgoing radiation is called

3.1. Instruments for measuring radiation balance

and its constituents

Actinometric devices are used to measure the intensity of radiant energy. various designs. Devices are absolute and relative. For absolute instruments, readings are obtained immediately in thermal units, and for relative instruments, in relative ones, therefore, for such instruments, it is necessary to know the conversion factors for the transition to thermal units.

Absolute instruments are quite complex in terms of design and handling and are not widely used. They are mainly used for verification of relative instruments. In the design of relative devices, the thermoelectric method is most often used, which is based on the dependence of the strength of the thermal current on the temperature difference between the junctions.

The receiver of thermoelectric devices are thermopiles made of junctions of two metals (Fig. 3.1). The temperature difference between the junctions is created as a result of the different absorptivity of the junctions or

vanometer 3. In the second case, the temperature difference of the junctions is achieved by shading some (junction3) and irradiating others (junction2) with solar radiation. Since the temperature difference between the junctions is determined by the incoming solar radiation, its intensity will be proportional to the strength of the thermoelectric current:

where N is the deviation of the galvanometer needle; a is the conversion factor, cal / cm2 min.

Thus, to express the intensity of radiation in thermal units, it is necessary to multiply the readings of the galvanometer by a conversion factor.

The conversion factor for a pair of thermoelectric device - galvanometer is determined by comparison with a control device or calculated from the electrical characteristics contained in the certificates of the galvanometer and actinometric device, with an accuracy of 0.0001 cal/cm2 min according to the formula

where a is a conversion factor; scale division value of the galvanometer, mA; k sensitivity of the thermoelectric device, millivolt per 1 cal/cm2 min; R b resistance of the thermopile, Ohm; R r internal resistance of the galvanometer, Ohm; R add additional resistance of the galvanometer, Ohm.

Thermoelectric actinometer AT-50 serves to measure direct solar radiation.

Actinometer device. The receiver of the actinometer is disk1 made of silver foil (Fig. 3.2). On the side facing the sun, the disk is blackened, and on the other side, internal junctions2 of a thermostar made of manganin and constantan, consisting of 36 thermoelements, are glued to it through an insulating paper gasket (only seven thermoelements are shown in the diagram). External junctions of 3 thermal stars through insulating paper

Rice. 3.2. Thermal star circuit

masonry 5 are glued to the copper disk4. By-

actinometer daughters the latter is placed in a massive copper case with brackets to which are attached

thermopile leads and soft wires 6 (Fig. 3.3).

The case with brackets is closed by a casing 7, fixed with a nut8, and connected with a screw10 to a measuring tube9. There are five diaphragms inside the tube, arranged in decreasing order of their diameter from 20 to 10 mm towards the body. The diaphragms are held by flat and spring washers installed between the body and the smallest diaphragm. FROM inside apertures are blackened.

At the ends of the tube there are rings 12 and 13 for aiming the actinometer at the sun. Ring13 has a hole and ring12 has a dot. When installed correctly, the beam of light passing through the hole should exactly fall on the point of the ring12. The tube is closed with a removable cover11, which serves to determine the zero position of the galvanometer and protects the receiver from contamination.

The tube 9 is connected to a stand 14 fixed on a plateau 16 by a parallax stand 17. To set the axis of the tripod according to the latitude of the place, a scale18 with divisions, a risk19 and a screw20 are used.

Installation. First, the tripod axis is set according to the latitude of the observation site. To do this, by loosening the screw 20, turn the axis of the tripod until the scale division 18 coincides, corresponding to

given latitude, with a risk of 19 and Rice. 3.3 Thermoelectricfix the axle in this position

actinometer AT-50

research institutes. Then the actinometer is installed on a horizontal stand so that the arrow on the plateau is oriented to the north, and, having removed the cover, orient it to the sun by loosening the screw 23 and turning the handle 22; the tube 9 is rotated until the beam of light through the hole on the ring 13 hits the point of the ring 12. After that, the wires of the actinometer with the cover open11 are connected to the galvanometer terminals (+) and (C), observing the polarity. If the galvanometer needle deviates beyond zero, the wires are reversed.

Observations. 1 minute before the start of the observation, the installation of the actinometer receiver in the sun is checked. After that, the lid is closed and the zero position N 0 is read using the galvanometer. Then the cover is removed, the accuracy of aiming at the sun is checked and the readings of the galvanometer are counted 3 times with an interval of 10-15 s (N 1 , N 2 , N 3 ) and the temperature on the galvanometer. After observations, the instrument is closed with the lid of the case.

Processing of observations. From three readings on the galvanometer, the average value of N c is found with an accuracy of 0.1:

N with N 1N 2N 3. 3

To obtain a corrected reading N to the average value N, a scale correction N is introduced, a correction for temperature N t from the calibration certificate of the galvanometer and the position of the zero point N 0 is subtracted:

N N Nt N0 .

To express the intensity of solar radiation S in cal / cm2 min, the readings of the galvanometer N are multiplied by the conversion factor:

The intensity of direct solar radiation on a horizontal surface is calculated by formula (3.3).

The height of the sun above the horizon h and sinh can be determined by the equation

sin h = sin sin + cos cos cos,

where is the latitude of the observation site; declination of the sun for a given day (Appendix 9); the hour angle of the sun measured from true noon. It is determined by the true time of the middle of the observations: t st = 15(t st 12h).

Thermoelectric pyranometer P-3x3 used to measure scattered and total solar radiation.

Pyranometer device (Fig. 3.4).

The receiving part of the pyranometer is a thermoelectric battery 1 consisting of 87 thermoelements of manganin and constantan. Strips of manganin and constantan 10 mm long are successively soldered to each other and placed in a 3x3 cm square so that the junctions are located in the middle and at the corners. From the outside, the surface of the thermopile is covered with soot and magnesia. The even junctions of the thermopile are colored in White color, and odd

- in black. Spas are arranged so that

black and white areas alternate in

Rice. 3.4. Thermoelectric pyranometer P-3x3

checkerboard pattern. Through an insulating paper gasket, the thermopile is attached to the ribs of a tile 2 screwed to the body 3.

Due to the different absorption of solar radiation, a temperature difference is created between the black and white junctions, so a thermal current occurs in the circuit. The leads from the thermopile are connected to terminals 4, to which the wires connecting the pyranometer with the galvanometer are connected.

The body is closed from above with a glass hemispherical cap 5 to protect the thermopile from wind and precipitation. To protect the thermopile and the glass cap from possible condensation of water vapor, there is a glass dryer6 with a chemical moisture absorber (metal sodium, silica gel, etc.) on the lower part of the housing.

The case with a thermopile and a glass dome constitutes the head of the pyranometer, which is screwed to the stand 7, clamped in the tripod 8 with a screw 9. The tripod is mounted on the base of the case and has two set screws 10 . When measuring scattered or total radiation, the pyranometer is installed horizontally according to the level11 by rotating the screws10.

To shade the head of the pyranometer from direct sunlight, a shadow screen is used, the diameter of which is equal to the diameter of the glass cap. The shadow screen is mounted on a tube 14, which is connected by a screw 13 to a horizontal rod 12.

When the pyranometer receiver is shaded with a shadow screen, diffuse radiation is measured, and without shading, total radiation is measured.

To determine the zero position of the galvanometer needle, as well as to protect the glass cap from damage, the head of the pyranometer is closed with a metal cover 16.

Installation. The device is installed in an open area. Before observation, the presence of the desiccant in the glass dryer is checked (1/3 of the dryer must be filled with the desiccant). Then the tube 14 with a shadow screen 15 is attached to the rod 12 with a screw 13.

The pyranometer is always turned towards the sun with the same side marked with a number on the head. To turn the head of the pyranometer with a number towards the sun, screw 9 is slightly loosened and fixed in this position.

The horizontality of the thermopile is checked at level 11 and, in case of violation, it is adjusted with set screws 10.

A galvanometer for measuring the strength of the thermal current is installed on the north side of the pyranometer at such a distance that the observer, when reading, does not shade the pyranometer not only from direct sunlight.

rays, but also from parts of the sky. The correct connection of the pyranometer to the galvanometer is checked with the cover of the pyranometer removed and the galvanometer cage released. When the arrow deviates beyond zero, the wire scales are interchanged.

Observations. Immediately before observation, check the correct installation of the device in terms of level and relative to the sun. To read the zero position of the galvanometer, the head of the pyranometer is closed with a lid16 and the readings of the galvanometer N 0 are recorded. After that, the cover of the pyranometer is removed and a series of readings is taken with an interval of 10-15 s.

First, the readings of the galvanometer are counted with a shaded pyranometer to determine the scattered radiation N 1, N 2, N 3, then - in an unshaded position (the shadow screen is lowered by loosening the screw13) to determine the total radiation N 4, N 5, N 6. After observations, the tube with the shadow screen is unscrewed and the pyranometer is closed with the lid of the case.

Processing of observations. From a series of readings on a galvanometer for each type of radiation, the average values ​​of N D and N Q are determined:

The corrected values ​​of N D and N Q are then obtained. For this purpose, the scale corrections N D and N Q are determined from the average values ​​from the verification certificate of the galvanometer and the bullet reading of the galvanometer is subtracted:

ND ND N N0 , NQ NQ N N0 .

To determine the intensity of scattered radiation D in cal / cm2 min, it is necessary to multiply the readings of the galvanometer N D by the conversion factor:

To determine the total radiation Q in cal / cm2 min, a correction factor for the height of the sun F h is also introduced. This correction factor is given in the verification certificate in the form of a graph: the height of the sun above the horizon is plotted along the abscissa axis, and the correction factor along the ordinate axis.

Taking into account the correction factor for the height of the sun, the total radiation is determined by the formula

Q = a (NQ ND )Fh + ND .

When observing with a pyranometer, the intensity of direct radiation to a horizontal surface can also be calculated as the difference between the total and scattered radiation:

The traveling thermoelectric albedometer AP-3x3 is intended for

chen for measurement in field conditions of total, scattered and reflected radiation. In practice, it is mainly used to measure the albedo of the active surface.

Albedometer device. The receiver of the albedometer (Fig. 3.5) is the head of the pyranometer 1, screwed on the sleeve 2 to the tube 3 with a gimbal suspension 4 and a handle 5. By turning the handle through 180°, the receiver can be turned upwards to measure incoming shortwave radiation and downwards to measure reflected shortwave radiation. In order for the tube to be in a vertical position, a special weight slides on the rod inside it, which always moves down when the device is turned. To mitigate shocks when turning the device, rubber pads6 are placed at the ends of the tube.

When disassembled, the device is mounted on the base of a metal case.

(C) with the receiver open and the galvanometer clamp released. If the galvanometer needle goes beyond zero, the wires are reversed.

During observations on a permanent site, the albedometer receiver is installed at a height of 1-1.5 m above the active surface, and in agricultural fields - at a distance of 0.5 m from the top level of the vegetation cover. When measuring total and scattered radiation, the head of the albedometer is turned with its number towards the sun.

Observations. Zero point is marked 3 minutes before the start of observations. To do this, the head of the albedometer is closed with a lid and the readings of the galvanometer N 0 are read. Then the lid is opened and three readings are made on the galvanometer with the position of the albedometer receiver up to measure the incoming total radiation: N 1 , N 2 , N 3 . After the third reading, the receiver is turned down and after 1 min three readings are made to measure the reflected radiation: N 4 , N 5 , N 6 . Then the receiver is turned up again and after 1 min, three more readings are taken to measure the incoming total radiation: N 7, N 8, N 9. After the end of a series of readings, the receiver is closed with a lid.

Processing of observations. First, calculate the average readings on the galvanometer for each type of radiation N Q and N Rk:

N Q N 1N 2N 3N 7N 8N 9, 6

N Rk N 4N 5N 6. 3

Then, a scale correction is introduced to the average values ​​from the verification certificate N Q and N Rk, the zero place N 0 is subtracted and the corrected values ​​N Q and N Rk are determined:

N QN QN N 0 , N RkN RkN N 0 .

Since albedo is expressed as the ratio of reflected radiation to total radiation, the conversion factor is reduced and albedo is calculated as the ratio of the corrected galvanometer readings when measuring reflected and total radiation (in percent):

The albedometer is the most versatile instrument. In the presence of a conversion factor, they can determine the total radiation, scattered, reflected, and calculate direct radiation to a horizontal surface. When observing scattered radiation, it is necessary to use a shadow screen to protect the receiver from direct sunlight.

Thermoelectric balance meter M-10 used for measuring

of the radiation balance of the underlying surface, or residual radiation, which is the algebraic sum of all types of radiation entering and losing this surface. The incoming part of the radiation consists of direct radiation to a horizontal surface S ", scattered radiation D and atmospheric radiation E a. The expenditure part of the radiation balance, or outgoing radiation, is reflected short-wave radiation R K and long-wave radiation of the earth E 3.

The action of the balance meter is based on the conversion of radiation fluxes into thermoelectromotive force using a thermopile.

Arising in a thermopile electromotive force proportional to the temperature difference between the upper and lower receivers of the balance meter. Since the temperature of the receivers depends on the incoming and outgoing radiation, the electromotive force will also be proportional to the difference in the radiation fluxes coming from above and below the receivers.

The radiation balance B when measured by a balance meter is expressed by the equation

N galvanometer readings; k is a correction factor that takes into account the influence of wind speed (Table 3.1).

Table 3.1

Correction factor k (example)

Balance gauge readings, multiplied by a correction factor corresponding to a given wind speed, are reduced to balance gauge readings in calm.

balance meter device(Fig. 3.6). The receiver of the balance meter is two blackened thin copper plates 1 and 2, having the shape of a square with a side of 48 mm. From the inside, junctions 3, 4 thermopiles are glued to them through paper spacers. The junctions are formed by coils of constantan tape wound around a copper bar5. Each turn of the ribbon is half silver plated. The beginning and end of the silver layer serve as thermal junctions. Even junctions are glued to the top, and odd junctions

nye to the bottom plate. The whole thermopile consists of ten bars, each of which is wound with 32-33 turns. The receiver of the balance meter is placed in a housing6 having the shape of a disk with a diameter of 96 mm and a thickness of 4 mm. The case is connected to the handle7, through which leads8 from the thermopile are passed. balance meter with ball-joint

Installation. The device is attached with a socket to the end of a wooden lath at a height of 1.5 m from the ground. The receiver is always installed horizontally with the same receiving side up, marked on the device with the number 1. The leads from the thermopile are connected to the galvanometer.

In most cases, the balance meter is shaded with a screen from direct solar radiation. Therefore, an actinometer is installed on the same rail with a balance meter to measure direct solar radiation. To take into account the influence of wind speed at the level of the balance meter and at a small distance from it, an anemometer is installed.

Observations. 3 minutes before the start of the observation, the zero point of the balance meter N 0 is determined. This is done with an open circuit. After that, the balance meter is connected to the galvanometer so that the galvanometer needle deviates to the right, and three readings are made on the balance meter N 1, N 2, N 3 and simultaneously three readings on the anemometer 1, 2, 3. If the balance meter is installed with a shadow screen, then after the first and second readings on the balance meter, two readings are made on the actinometer