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Solar radiation - what is it? Total solar radiation. Structure, radiation and evolution of the sun add your price to the database comment

The sun is a source of light and heat that all living things on Earth need. But in addition to photons of light, it emits hard ionizing radiation, consisting of helium nuclei and protons. Why is this happening?

Causes of solar radiation

Solar radiation is produced in the daytime during chromospheric flares - giant explosions that occur in the solar atmosphere. Some of the solar matter is ejected into outer space, forming cosmic rays, mainly consisting of protons and a small amount of helium nuclei. These charged particles reach the earth's surface 15-20 minutes after the solar flare becomes visible.

The air cuts off primary cosmic radiation, generating a cascading nuclear shower, which fades with decreasing altitude. In this case, new particles are born - pions, which decay and turn into muons. They penetrate into the lower layers of the atmosphere and fall to the ground, burrowing up to 1500 meters deep. It is muons that are responsible for the formation of secondary cosmic radiation and natural radiation affecting humans.

Solar radiation spectrum

The spectrum of solar radiation includes both short-wave and long-wave regions:

  • gamma rays;
  • x-ray radiation;
  • UV radiation;
  • visible light;
  • infrared radiation.

Over 95% of the sun's radiation falls in the region of the “optical window” - the visible part of the spectrum with adjacent regions of ultraviolet and infrared waves. As they pass through the layers of the atmosphere, the effect of the sun's rays is weakened - all ionizing radiation, X-rays and almost 98% of ultraviolet radiation are retained by the earth's atmosphere. Visible light and infrared radiation reach the ground practically without loss, although they are partially absorbed by gas molecules and dust particles in the air.

In this regard, solar radiation does not lead to a noticeable increase in radioactive radiation on the Earth's surface. The contribution of the Sun, together with cosmic rays, to the formation of the total annual radiation dose is only 0.3 mSv/year. But this is an average value; in fact, the level of radiation incident on the earth is different and depends on the geographical location of the area.

Where is solar ionizing radiation greatest?

The greatest power of cosmic rays is recorded at the poles, and the least at the equator. This is due to the fact that the Earth's magnetic field deflects charged particles falling from space towards the poles. In addition, radiation increases with altitude - at an altitude of 10 kilometers above sea level, its indicator increases by 20-25 times. Active influence Residents of high mountains are exposed to higher doses of solar radiation, since the atmosphere in the mountains is thinner and more easily penetrated by streams of gamma quanta and elementary particles coming from the sun.

Important. Radiation levels up to 0.3 mSv/h do not have a serious impact, but at a dose of 1.2 μSv/h it is recommended to leave the area, and in case of emergency, stay in its territory for no more than six months. If the readings exceed twice, you should limit your stay in this area to three months.

If above sea level the annual dose of cosmic radiation is 0.3 mSv/year, then with an increase in altitude every hundred meters this figure increases by 0.03 mSv/year. After some small calculations, we can conclude that a week-long vacation in the mountains at an altitude of 2000 meters will give an exposure of 1 mSv/year and will provide almost half of the total annual norm (2.4 mSv/year).

It turns out that mountain residents receive an annual dose of radiation that is several times higher than normal, and should suffer from leukemia and cancer more often than people living on the plains. In fact, this is not true. On the contrary, in mountainous areas there is a lower mortality rate from these diseases, and part of the population is long-lived. This confirms the fact that long-term stay in places of high radiation activity does not affect negative influence on the human body.

Solar flares - high radiation hazard

Solar flares - great danger for humans and all life on Earth, since the flux density of solar radiation can exceed the normal level of cosmic radiation by a thousand times. Thus, the outstanding Soviet scientist A.L. Chizhevsky connected the periods of sunspot formation with epidemics of typhus (1883-1917) and cholera (1823-1923) in Russia. Based on the graphs he made, back in 1930 he predicted the emergence of an extensive cholera pandemic in 1960-1962, which began in Indonesia in 1961, then quickly spread to other countries in Asia, Africa and Europe.

Today, a wealth of data has been obtained indicating the connection between eleven-year cycles of solar activity and outbreaks of diseases, as well as with mass migrations and seasons of rapid reproduction of insects, mammals and viruses. Hematologists have found an increase in the number of heart attacks and strokes during periods of maximum solar activity. Such statistics are due to the fact that at this time people’s blood clotting increases, and since in patients with heart disease compensatory activity is suppressed, malfunctions occur in its work, including necrosis of cardiac tissue and hemorrhages in the brain.

Large solar flares do not occur so often - once every 4 years. At this time, the number and size of sunspots increases, and powerful coronal rays are formed in the solar corona, consisting of protons and a small amount of alpha particles. Astrologers registered their most powerful flow in 1956, when the density of cosmic radiation on the surface of the earth increased 4 times. Another consequence of such solar activity was the aurora, recorded in Moscow and the Moscow region in 2000.

How to protect yourself?

Of course, increased background radiation in the mountains is not a reason to refuse trips to the mountains. However, it is worth thinking about safety measures and going on a trip with a portable radiometer, which will help control the level of radiation and, if necessary, limit the time spent in dangerous areas. You should not stay in an area where the meter readings show an ionizing radiation level of 7 μSv/h for more than one month.

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 flow electromagnetic vibrations, 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, but 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. The body of animals continuously absorbs and emits 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 peripheral blood red blood cell count and hemoglobin content. 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 increased growth in young animals goes faster. 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 exhausted animals the intensity slows down fat metabolism and increased fat deposition. 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 artificial lighting animals, their gestation period 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 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 immune properties 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, provided with regular exercise, 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. For more precise definition illumination in rooms is used by 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 vascular membranes eyes and damage to 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 disrupted. 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 heart paralysis 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.

Solar radiation is radiation characteristic of the star of our planetary system. Sun - main star, around which the Earth and its neighboring planets orbit. In fact, it is a huge hot ball of gas, constantly emitting streams of energy into the space around it. This is what is called radiation. Deadly, at the same time this energy is one of the main factors making possible life on our planet. Like everything in this world, the benefits and harms of solar radiation for organic life are closely interrelated.

General overview

To understand what solar radiation is, you must first understand what the Sun is. The main source of heat that provides the conditions for organic existence on our planet, in the universal expanses, is only a small star on the galactic outskirts Milky Way. But for earthlings, the Sun is the center of the mini-universe. After all, it is around this gas clump that our planet revolves. The sun gives us warmth and light, that is, it supplies forms of energy without which our existence would be impossible.

In ancient times, the source of solar radiation - the Sun - was a deity, an object worthy of worship. The solar trajectory across the sky seemed to people obvious proof of God's will. Attempts to understand the essence of the phenomenon, to explain what this star is, have been made for a long time, and Copernicus made a particularly significant contribution to them, forming the idea of ​​heliocentrism, which was strikingly different from the generally accepted geocentrism of that era. However, it is known for certain that in ancient times scientists more than once thought about what the Sun is, why it is so important for any forms of life on our planet, why the movement of this luminary is exactly the way we see it.

The progress of technology has made it possible to better understand what the Sun is, what processes occur inside the star, on its surface. Scientists have learned what solar radiation is, how a gas object affects the planets in its zone of influence, in particular, the earth’s climate. Now humanity has a sufficiently voluminous knowledge base to say with confidence: it was possible to find out what the radiation emitted by the Sun is in its essence, how to measure this energy flow and how to formulate the features of its impact on different shapes organic life on Earth.

About terms

The most important step in mastering the essence of the concept was made in the last century. It was then that the eminent astronomer A. Eddington formulated an assumption: thermonuclear fusion occurs in the depths of the sun, which allows the release of a huge amount of energy emitted into the space around the star. Trying to estimate the magnitude of solar radiation, efforts were made to determine the actual parameters of the environment on the luminary. Thus, the temperature of the core, according to scientists, reaches 15 million degrees. This is sufficient to cope with the mutual repulsive influence of protons. The collision of units leads to the formation of helium nuclei.

New information attracted the attention of many prominent scientists, including A. Einstein. In attempts to estimate the amount of solar radiation, scientists found that helium nuclei in their mass are inferior to the total value of 4 protons necessary for the formation of a new structure. This is how a feature of the reactions was identified, called the “mass defect”. But in nature nothing can disappear without a trace! In an attempt to find the “escaped” values, scientists compared energy healing and the specificity of mass changes. It was then that it was possible to reveal that the difference was emitted by gamma rays.

Emitted objects make their way from the core of our star to its surface through numerous gaseous atmospheric layers, which leads to the fragmentation of elements and the formation of electromagnetic radiation based on them. Among other types of solar radiation is light perceived by the human eye. Rough estimates suggest that the process of passing gamma rays takes about 10 million years. Another eight minutes - and the emitted energy reaches the surface of our planet.

How and what?

Solar radiation is the total complex of electromagnetic radiation, which has a fairly wide range. This includes the so-called solar wind, that is, an energy flow formed by electrons and light particles. At the boundary layer of our planet's atmosphere, the same intensity of solar radiation is constantly observed. The energy of a star is discrete, its transfer is carried out through quanta, and the corpuscular nuance is so insignificant that the rays can be considered as electromagnetic waves. And their distribution, as physicists have found, occurs evenly and in a straight line. Thus, in order to describe solar radiation, it is necessary to determine its characteristic wavelength. Based on this parameter, it is customary to distinguish several types of radiation:

  • warm;
  • radio wave;
  • white light;
  • ultraviolet;
  • gamma;
  • X-ray.

The ratio of infrared, visible, ultraviolet is best estimated as follows: 52%, 43%, 5%.

For a quantitative radiation assessment, it is necessary to calculate the energy flux density, that is, the amount of energy that reaches a limited area of ​​the surface in a given time period.

Research has shown that solar radiation is predominantly absorbed by the planetary atmosphere. Thanks to this, heating occurs to a temperature comfortable for organic life characteristic of the Earth. The existing ozone shell allows only one hundredth of ultraviolet radiation to pass through. In this case, the waves are completely blocked short length, dangerous to living beings. Atmospheric layers are capable of scattering almost a third of the Sun's rays, and another 20% are absorbed. Consequently, no more than half of the total energy reaches the planet's surface. It is this “residue” that science calls direct solar radiation.

How about more details?

There are several aspects that determine how intense the direct radiation will be. The most significant are the angle of incidence, which depends on latitude (geographical characteristic of the area on the globe), and the time of year, which determines how great the distance to a specific point from the radiation source is. Much depends on the characteristics of the atmosphere - how polluted it is, how many clouds there are at a given moment. Finally, the nature of the surface on which the beam falls plays a role, namely, its ability to reflect incoming waves.

Total solar radiation is a quantity that combines scattered volumes and direct radiation. The parameter used to assess intensity is estimated in calories per unit area. At the same time, remember that at different times of the day the values ​​characteristic of radiation differ. In addition, energy cannot be distributed evenly over the surface of the planet. The closer to the pole, the higher the intensity, while the snow covers are highly reflective, which means the air does not get the opportunity to warm up. Consequently, the further from the equator, the lower the total solar wave radiation will be.

As scientists have discovered, the energy of solar radiation has a serious impact on the planetary climate and subjugates the life activity of various organisms existing on Earth. In our country, as well as in the territory of our closest neighbors, as well as in other countries located in the northern hemisphere, in winter the predominant share belongs to scattered radiation, but in summer direct radiation dominates.

Infrared waves

Of the total amount of total solar radiation, an impressive percentage belongs to the infrared spectrum, which is not perceived by the human eye. Due to such waves, the surface of the planet heats up, gradually transferring thermal energy to the air masses. This helps maintain a comfortable climate and maintain conditions for the existence of organic life. If no serious disruptions occur, the climate remains relatively unchanged, which means that all creatures can live in their usual conditions.

Our star is not the only source of waves infrared spectrum. Similar radiation is characteristic of any heated object, including a conventional battery in human home. It is on the principle of perception infrared radiation Numerous devices operate that make it possible to see heated bodies in the dark or other conditions that are uncomfortable for the eyes. By the way, compact devices that have become so popular recently work on a similar principle for assessing through which areas of the building the greatest heat loss occurs. These mechanisms are especially widespread among builders, as well as owners of private houses, since they help to identify through which areas heat is lost, organize their protection and prevent unnecessary energy consumption.

Do not underestimate the influence of solar radiation in the infrared spectrum on the human body simply because our eyes cannot perceive such waves. In particular, radiation is actively used in medicine, since it makes it possible to increase the concentration of leukocytes in the circulatory system, as well as normalize blood flow by increasing the lumens of blood vessels. Devices based on the IR spectrum are used as preventative against skin pathologies, therapeutic for inflammatory processes in acute and chronic form. The most modern drugs help cope with colloid scars and trophic wounds.

This is interesting

Based on the study of solar radiation factors, it was possible to create truly unique devices called thermographs. They make it possible to detect in a timely manner various diseases, not accessible to detection by other means. This is how you can find cancer or a blood clot. IR protects to some extent from ultraviolet radiation, which is dangerous to organic life, which has made it possible to use waves of this spectrum to restore the health of astronauts who have been in space for a long time.

The nature around us is still mysterious to this day, this also applies to radiation of various wavelengths. In particular, infrared light has not yet been thoroughly studied. Scientists know that it misuse may cause harm to health. Thus, it is unacceptable to use equipment that generates such light for the treatment of purulent inflamed areas, bleeding and malignant neoplasms. The infrared spectrum is contraindicated for people suffering from dysfunction of the heart and blood vessels, including those located in the brain.

Visible light

One of the elements of total solar radiation is visible to the human eye light. The wave beams travel in straight lines, so they do not overlap each other. At one time, this became the topic of a considerable number of scientific works: scientists set out to understand why there are so many shades around us. It turned out that key light parameters play a role:

  • refraction;
  • reflection;
  • absorption.

As scientists have found, objects are not capable of being sources of visible light, but can absorb radiation and reflect it. Reflection angles and wave frequencies vary. Over the course of many centuries, man's ability to see has gradually improved, but certain limitations are due to biological structure eyes: the retina is such that it can perceive only certain rays of reflected light waves. This radiation is a small gap between ultraviolet and infrared waves.

Numerous curious and mysterious features of light not only became the topic of many works, but also were the basis for the emergence of a new physical discipline. At the same time, non-scientific practices appeared, theories whose adherents believe that color can influence physical condition person, psyche. Based on such assumptions, people surround themselves with objects that are most pleasing to their eyes, making everyday life more comfortable.

Ultraviolet

An equally important aspect of total solar radiation is ultraviolet radiation, formed by waves of large, medium and short lengths. They differ from each other both in physical parameters and in the characteristics of their influence on forms of organic life. Long ultraviolet waves, for example, are mostly scattered in the atmospheric layers, and only a small percentage reaches the earth's surface. The shorter the wavelength, the deeper such radiation can penetrate human (and not only) skin.

On the one hand, ultraviolet radiation is dangerous, but without it the existence of diverse organic life is impossible. This radiation is responsible for the formation of calciferol in the body, and this element is necessary for the construction of bone tissue. The UV spectrum is a powerful prevention of rickets and osteochondrosis, which is especially important in childhood. In addition, such radiation:

  • normalizes metabolism;
  • activates the production of essential enzymes;
  • enhances regenerative processes;
  • stimulates blood flow;
  • expands blood vessels;
  • stimulates the immune system;
  • leads to the formation of endorphin, which means nervous overexcitation decreases.

The other side of the coin

It was stated above that total solar radiation is the amount of radiation that reaches the surface of the planet and is scattered in the atmosphere. Accordingly, the element of this volume is ultraviolet of all lengths. It must be remembered that this factor has both positive and negative aspects influence on organic life. Sunbathing, although often beneficial, can be a source of health hazards. Staying under direct line for too long sunlight, especially in conditions increased activity luminary, harmful and dangerous. Long-term effects on the body, as well as too high radiation activity, cause:

  • burns, redness;
  • swelling;
  • hyperemia;
  • heat;
  • nausea;
  • vomiting.

Long lasting ultraviolet irradiation provokes disturbances in appetite, functioning of the central nervous system, and immune system. In addition, my head starts to hurt. The described symptoms are classic manifestations of sunstroke. The person himself cannot always realize what is happening - the condition worsens gradually. If it is noticeable that someone nearby is feeling ill, first aid should be provided. The scheme is as follows:

  • help move from direct light to a cool, shaded place;
  • put the patient on his back so that his legs are higher than his head (this will help normalize blood flow);
  • cool your neck and face with water, and put a cold compress on your forehead;
  • unfasten the tie, belt, remove tight clothes;
  • half an hour after the attack, give cool water (a small amount) to drink.

If the victim loses consciousness, it is important to immediately seek help from a doctor. The ambulance team will move the person to safety and give an injection of glucose or vitamin C. The medicine is given into a vein.

How to tan correctly?

In order not to learn from your own experience how unpleasant the excessive amount of solar radiation received from tanning can be, it is important to follow the rules of safe spending time in the sun. Ultraviolet light initiates the production of melanin, a hormone that helps the skin protect itself from the negative effects of waves. Under the influence of this substance, the skin becomes darker and the shade turns bronze. To this day, debates continue about how beneficial and harmful it is for humans.

On the one hand, tanning is an attempt by the body to protect itself from excessive exposure to radiation. This increases the likelihood of the formation of malignant neoplasms. On the other hand, tanning is considered fashionable and beautiful. To minimize the risks for yourself, it is wise, before starting beach procedures, to understand why the amount of solar radiation received during sunbathing is dangerous, and how to minimize the risks for yourself. To make the experience as pleasant as possible, sunbathers should:

  • drink a lot of water;
  • use skin protecting products;
  • sunbathe in the evening or in the morning;
  • spend no more than an hour in direct sunlight;
  • do not drink alcohol;
  • include foods rich in selenium, tocopherol, and tyrosine in the menu. Don't forget about beta-carotene.

The importance of solar radiation for the human body is extremely great; both positive and negative aspects should not be overlooked. It should be realized that different people have biochemical reactions with individual characteristics, so for some, half an hour of sunbathing can be dangerous. It is wise to consult a doctor before the beach season to assess the type and condition skin. This will help prevent harm to health.

If possible, you should avoid tanning in old age, during the period of bearing a baby. Cancer, mental disorders, and sunbathing are not combined with sunbathing. skin pathologies and failure of the heart.

Total radiation: where is the shortage?

The process of distribution of solar radiation is quite interesting to consider. As mentioned above, only about half of all waves can reach the surface of the planet. Where do the rest go? The different layers of the atmosphere and the microscopic particles from which they are formed play their role. An impressive part, as stated, is absorbed by the ozone layer - these are all waves whose length is less than 0.36 microns. Additionally, ozone is capable of absorbing some types of waves from the spectrum visible to the human eye, that is, the range of 0.44-1.18 microns.

Ultraviolet light is absorbed to some extent by the oxygen layer. This is typical for radiation with a wavelength of 0.13-0.24 microns. Carbon dioxide and water vapor can absorb a small percentage of the infrared spectrum. The atmospheric aerosol absorbs some part (IR spectrum) of the total amount of solar radiation.

Waves from the short category are scattered in the atmosphere due to the presence of microscopic inhomogeneous particles, aerosol, and clouds. Inhomogeneous elements, particles whose dimensions are smaller than the wavelength, provoke molecular scattering, and larger ones are characterized by a phenomenon described by the indicatrix, that is, aerosol.

The remaining amount of solar radiation reaches the earth's surface. It combines direct radiation and scattered radiation.

Total radiation: important aspects

The total value is the amount of solar radiation received by the territory, as well as absorbed in the atmosphere. If there are no clouds in the sky, the total amount of radiation depends on the latitude of the area, altitude celestial body, the type of ground surface in this area, as well as the level of air transparency. The more aerosol particles scattered in the atmosphere, the lower the direct radiation, but the proportion of scattered radiation increases. Normally, in the absence of clouds, scattered radiation is one fourth of the total radiation.

Our country is one of the northern ones, so most of the year in the southern regions the radiation is significantly greater than in the northern ones. This is due to the position of the star in the sky. But the short time period of May-July is a unique period when, even in the north, the total radiation is quite impressive, since the sun is high in the sky, and the duration of daylight hours is longer than in other months of the year. Moreover, on average, in the Asian half of the country, in the absence of clouds, the total radiation is more significant than in the west. The maximum strength of the wave radiation occurs at midday, and the annual maximum occurs in June, when the sun is highest in the sky.

Total solar radiation is the amount of solar energy reaching our planet. It must be remembered that various atmospheric factors lead to the fact that the annual amount of total radiation is less than it could be. The largest difference between what is actually observed and the maximum possible is typical for the Far Eastern regions in the summer. Monsoons provoke extremely dense clouds, so the total radiation is reduced by approximately half.

Curious to know

The largest percentage of the maximum possible exposure to solar energy is actually observed (per 12 months) in the south of the country. The figure reaches 80%.

Cloudiness does not always result in the same amount of solar radiation dissipation. The shape of the clouds and the features of the solar disk at a particular moment in time play a role. If it is open, then cloudiness causes a decrease in direct radiation, while scattered radiation increases sharply.

There may also be days when direct radiation is approximately the same in strength as scattered radiation. The daily total value may be even greater than the radiation characteristic of a completely cloudless day.

When calculating for 12 months, special attention must be paid to astronomical phenomena as they determine general numerical indicators. At the same time, cloudiness leads to the fact that the radiation maximum may actually be observed not in June, but a month earlier or later.

Radiation in space

From the boundary of the magnetosphere of our planet and further into outer space, solar radiation becomes a factor associated with mortal danger for a person. Back in 1964, an important popular science work was published on protection methods. Its authors were Soviet scientists Kamanin and Bubnov. It is known that for a person, the radiation dose per week should be no more than 0.3 roentgens, while for a year - within 15 R. For short-term exposure, the limit for a person is 600 R. Flights into space, especially in conditions of unpredictable solar activity , may be accompanied by significant exposure of astronauts, which requires additional protective measures to be taken against waves of different lengths.

More than a decade has passed since the Apollo missions, during which protection methods were tested and factors affecting human health were studied, but to this day scientists cannot find effective, reliable methods for predicting geomagnetic storms. You can make a forecast based on hours, sometimes for several days, but even for a weekly assumption, the chances of implementation are no more than 5%. The solar wind is an even more unpredictable phenomenon. With a probability of one in three, astronauts setting off on a new mission may find themselves in powerful streams of radiation. This makes it even more important question both research and prediction of radiation characteristics, and the development of methods of protection against it.

LECTURE 2.

SOLAR RADIATION.

Plan:

1. The importance of solar radiation for life on Earth.

2. Types of solar radiation.

3. Spectral composition of solar radiation.

4. Absorption and dispersion of radiation.

5.PAR (photosynthetically active radiation).

6. Radiation balance.

1. The main source of energy on Earth for all living things (plants, animals and humans) is the energy of the sun.

The Sun is a gas ball with a radius of 695,300 km. The radius of the Sun is 109 times greater than the radius of the Earth (equatorial 6378.2 km, polar 6356.8 km). The sun is composed primarily of hydrogen (64%) and helium (32%). The rest account for only 4% of its mass.

Solar energy is the main condition for the existence of the biosphere and one of the main climate-forming factors. Due to the energy of the Sun, air masses in the atmosphere continuously move, which ensures the constancy of the gas composition of the atmosphere. Under the influence of solar radiation, a huge amount of water evaporates from the surface of reservoirs, soil, and plants. Water vapor carried by the wind from the oceans and seas to the continents is the main source of precipitation for land.

Solar energy is an indispensable condition for the existence of green plants, which convert solar energy into high-energy organic substances through the process of photosynthesis.

The growth and development of plants is a process of assimilation and processing of solar energy, therefore agricultural production is possible only if solar energy reaches the surface of the Earth. A Russian scientist wrote: “Give the best cook as much as you like.” fresh air, sunlight, a whole river of clean water, ask him to prepare sugar, starch, fats and grains from all this, and he will think that you are laughing at him. But what seems absolutely fantastic to a person occurs unhindered in the green leaves of plants under the influence of the energy of the Sun.” It is estimated that 1 sq. A meter of leaves produces a gram of sugar per hour. Due to the fact that the Earth is surrounded by a continuous shell of the atmosphere, the sun's rays, before reaching the surface of the earth, pass through the entire thickness of the atmosphere, which partially reflects them and partially scatters them, i.e., changes the quantity and quality of sunlight arriving at the surface of the earth. Living organisms react sensitively to changes in the intensity of illumination created by solar radiation. Due to different reactions to light intensity, all forms of vegetation are divided into light-loving and shade-tolerant. Insufficient illumination in crops causes, for example, poor differentiation of straw tissues of grain crops. As a result, the strength and elasticity of tissues decrease, which often leads to lodging of crops. In dense corn crops, due to low solar radiation, the formation of cobs on plants is weakened.

Solar radiation affects chemical composition agricultural products. For example, the sugar content of beets and fruits, the protein content in wheat grains directly depend on the number of sunny days. The amount of oil in sunflower and flax seeds also increases with increasing solar radiation.

Illumination of the above-ground parts of plants significantly affects the absorption of nutrients by roots. In low light conditions, the transfer of assimilates to the roots slows down, and as a result, the biosynthetic processes occurring in plant cells are inhibited.

Illumination also affects the appearance, spread and development of plant diseases. The infection period consists of two phases that differ in their reaction to the light factor. The first of them - the actual germination of spores and the penetration of the infectious principle into the tissues of the affected culture - in most cases does not depend on the presence and intensity of light. The second - after germination of the spores - is most active under increased illumination.

The positive effect of light also affects the rate of development of the pathogen in the host plant. This is especially evident in rust fungi. The more light, the shorter incubation period in linear rust of wheat, yellow rust of barley, rust of flax and beans, etc. And this increases the number of generations of the fungus and increases the intensity of the damage. Fertility increases in this pathogen under intense lighting conditions

Some diseases develop most actively in insufficient lighting, which causes weakening of plants and a decrease in their resistance to diseases (pathogens). various kinds rot, especially vegetable crops).

Light duration and plants. The rhythm of solar radiation (alternation of light and dark parts of the day) is the most stable environmental factor that repeats from year to year. As a result of many years of research, physiologists have established the dependence of the transition of plants to generative development on a certain ratio of the length of day and night. In this regard, crops can be classified into groups according to their photoperiodic reaction: short day the development of which is delayed when the day length is more than 10 hours. A short day promotes flower initiation, while a long day prevents this. Such crops include soybeans, rice, millet, sorghum, corn, etc.;

long day until 12-13 o'clock, requiring prolonged lighting for their development. Their development accelerates when the day length is about 20 hours. These crops include rye, oats, wheat, flax, peas, spinach, clover, etc.;

day length neutral, the development of which does not depend on the length of the day, for example, tomato, buckwheat, legumes, rhubarb.

It has been established that for plants to begin flowering, a predominance of a certain spectral composition in the radiant flux is necessary. Short-day plants develop faster when the maximum radiation falls on blue-violet rays, and long-day plants - on red ones. The duration of the daylight hours (astronomical day length) depends on the time of year and latitude. At the equator, the length of the day throughout the year is 12 hours ± 30 minutes. When moving from the equator to the poles after the spring equinox (21.03), the length of the day increases to the north and decreases to the south. After autumn equinox(23.09) the distribution of day length is inverse. In the Northern Hemisphere, June 22 is the longest day, the duration of which is 24 hours north of the Arctic Circle. The shortest day in the Northern Hemisphere is December 22, and beyond the Arctic Circle in the winter months the Sun does not rise above the horizon at all. In middle latitudes, for example in Moscow, the length of the day varies throughout the year from 7 to 17.5 hours.

2. Types of solar radiation.

Solar radiation consists of three components: direct solar radiation, diffuse and total.

DIRECT SOLAR RADIATIONS – radiation coming from the Sun into the atmosphere and then onto the earth's surface in the form of a beam of parallel rays. Its intensity is measured in calories per cm2 per minute. It depends on the height of the sun and the state of the atmosphere (cloudiness, dust, water vapor). The annual amount of direct solar radiation on the horizontal surface of the Stavropol Territory is 65-76 kcal/cm2/min. At sea level, with a high position of the Sun (summer, noon) and good transparency, direct solar radiation is 1.5 kcal/cm2/min. This is the short-wave part of the spectrum. When the flow of direct solar radiation passes through the atmosphere, it weakens, caused by the absorption (about 15%) and dissipation (about 25%) of energy by gases, aerosols, and clouds.

The flow of direct solar radiation falling on a horizontal surface is called insolation S= S sin ho– vertical component of direct solar radiation.

S – the amount of heat received by a surface perpendicular to the beam ,

ho – the height of the Sun, i.e. the angle formed by a solar ray with a horizontal surface .

At the boundary of the atmosphere, the intensity of solar radiation isSo= 1,98 kcal/cm2/min. – according to the international agreement of 1958 And it's called the solar constant. This is how it would look at the surface if the atmosphere were absolutely transparent.

Rice. 2.1. Path of a sunbeam in the atmosphere at different heights Sun

SCATTERED RADIATIOND – As a result of scattering by the atmosphere, part of the solar radiation goes back into space, but a significant part of it arrives on Earth in the form of scattered radiation. Maximum scattered radiation + 1 kcal/cm2/min. It is observed when the sky is clear and there are high clouds. Under cloudy skies, the spectrum of scattered radiation is similar to that of the sun. This is the short-wave part of the spectrum. Wavelength 0.17-4 microns.

TOTAL RADIATIONQ- consists of diffuse and direct radiation onto a horizontal surface. Q= S+ D.

The ratio between direct and diffuse radiation in the composition of total radiation depends on the height of the Sun, cloudiness and atmospheric pollution, and the height of the surface above sea level. As the height of the Sun increases, the proportion of scattered radiation in a cloudless sky decreases. The more transparent the atmosphere and the higher the Sun, the lower the proportion of scattered radiation. With continuous dense clouds, the total radiation consists entirely of scattered radiation. In winter, due to the reflection of radiation from the snow cover and its secondary scattering in the atmosphere, the share of scattered radiation in the total radiation increases noticeably.

The light and heat received by plants from the Sun are the result of the total solar radiation. Therefore, data on the amounts of radiation received by the surface per day, month, growing season, year are of great importance for agriculture.

Reflected solar radiation. Albedo. The total radiation that reaches the earth's surface, partially reflected from it, creates reflected solar radiation (RK), directed from the earth's surface into the atmosphere. The value of reflected radiation largely depends on the properties and condition of the reflecting surface: color, roughness, humidity, etc. The reflectivity of any surface can be characterized by the value of its albedo (Ak), which is understood as the ratio of reflected solar radiation to total. Albedo is usually expressed as a percentage:

Observations show that the albedo of various surfaces varies within relatively narrow limits (10...30%), with the exception of snow and water.

Albedo depends on soil moisture, with an increase in which it decreases, which is important in the process of changing the thermal regime of irrigated fields. Due to a decrease in albedo when the soil is moistened, the absorbed radiation increases. The albedo of various surfaces has a well-defined daily and annual variation, due to the dependence of the albedo on the height of the Sun. The lowest albedo value is observed around midday hours, and throughout the year - in the summer.

Earth's own radiation and counter radiation from the atmosphere. Effective radiation. The Earth's surface as a physical body having a temperature above absolute zero (-273 ° C) is a source of radiation, which is called the Earth's own radiation (E3). It is directed into the atmosphere and is almost completely absorbed by water vapor, water droplets and carbon dioxide contained in the air. The Earth's radiation depends on its surface temperature.

The atmosphere, absorbing a small amount of solar radiation and almost all the energy emitted by the earth's surface, heats up and, in turn, also emits energy. About 30% of atmospheric radiation goes into outer space, and about 70% comes to the surface of the Earth and is called counter atmospheric radiation (Ea).

The amount of energy emitted by the atmosphere is directly proportional to its temperature, carbon dioxide, ozone and cloudiness.

The Earth's surface absorbs this counter radiation almost entirely (90...99%). Thus, it is for the earth's surface important source heat in addition to absorbed solar radiation. This influence of the atmosphere on the thermal regime of the Earth is called the greenhouse or greenhouse effect due to the external analogy with the effect of glass in greenhouses and greenhouses. Glass transmits the sun's rays well, heating the soil and plants, but delays the thermal radiation of heated soil and plants.

The difference between the Earth's surface's own radiation and the counter-radiation of the atmosphere is called effective radiation: Eeff.

Eef= E3-EA

On clear and partly cloudy nights, the effective radiation is much greater than on cloudy nights, and therefore the night cooling of the earth's surface is greater. During the day, it is covered by the absorbed total radiation, as a result of which the surface temperature rises. At the same time, effective radiation also increases. The earth's surface in mid-latitudes loses 70...140 W/m2 due to effective radiation, which is approximately half the amount of heat it receives from the absorption of solar radiation.

3. Spectral composition of radiation.

The sun, as a source of radiation, has a variety of emitted waves. Radiant energy fluxes according to wavelength are conventionally divided into shortwave (X < 4 мкм) и длинноволновую (А. >4 µm) radiation. The spectrum of solar radiation at the boundary of the earth's atmosphere practically lies between wavelengths of 0.17 and 4 microns, and that of terrestrial and atmospheric radiation - from 4 to 120 microns. Consequently, the fluxes of solar radiation (S, D, RK) belong to short-wave radiation, and the radiation of the Earth (£3) and the atmosphere (Ea) belongs to long-wave radiation.

The spectrum of solar radiation can be divided into three qualitatively different parts: ultraviolet (Y< 0,40 мкм), ви­димую (0,40 мкм < Y < 0.75 µm) and infrared (0.76 µm < Y < 4 µm). Before the ultraviolet part of the solar radiation spectrum lies X-ray radiation, and beyond the infrared part lies the radio emission of the Sun. At the upper boundary of the atmosphere, the ultraviolet part of the spectrum accounts for about 7% of the solar radiation energy, 46% for the visible and 47% for the infrared.

The radiation emitted by the Earth and atmosphere is called far infrared radiation.

Biological action different types radiation on plants varies. Ultraviolet radiation slows down growth processes, but accelerates the passage of stages of formation of reproductive organs in plants.

Meaning of infrared radiation, which is actively absorbed by water from the leaves and stems of plants, is its thermal effect, which significantly affects the growth and development of plants.

Far infrared radiation produces only a thermal effect on plants. Its influence on the growth and development of plants is insignificant.

Visible part of the solar spectrum, firstly, creates illumination. Secondly, the so-called physiological radiation (A, = 0.35...0.75 μm), which is absorbed by leaf pigments, almost coincides with the region of visible radiation (partially capturing the region of ultraviolet radiation). Its energy has an important regulatory and energetic significance in plant life. Within this part of the spectrum, a region of photosynthetically active radiation is distinguished.

4. Absorption and dispersion of radiation in the atmosphere.

As solar radiation passes through the earth's atmosphere, it is attenuated due to absorption and scattering by atmospheric gases and aerosols. At the same time, its spectral composition also changes. With different heights of the sun and different heights of the observation point above the earth's surface, the length of the path traveled by a solar ray in the atmosphere is not the same. As the altitude decreases, the ultraviolet part of the radiation decreases especially strongly, the visible part decreases somewhat less, and the infrared part decreases only slightly.

The dispersion of radiation in the atmosphere occurs mainly as a result of continuous fluctuations (fluctuations) in air density at each point in the atmosphere, caused by the formation and destruction of certain “clumps” (clumps) of atmospheric gas molecules. Solar radiation is also scattered by aerosol particles. The scattering intensity is characterized by the scattering coefficient.

K= add formula.

The intensity of scattering depends on the number of scattering particles per unit volume, on their size and nature, as well as on the wavelengths of the scattered radiation itself.

The shorter the wavelength, the more strongly the rays are scattered. For example, violet rays are scattered 14 times more strongly than red ones, which explains the blue color of the sky. As noted above (see Section 2.2), direct solar radiation, passing through the atmosphere, is partially scattered. In clean and dry air, the intensity of the molecular scattering coefficient obeys Rayleigh's law:

k= c/Y4 ,

where C is a coefficient depending on the number of gas molecules per unit volume; X is the length of the scattered wave.

Since the far wavelengths of red light are almost twice the wavelength of violet light, the former are scattered by air molecules 14 times less than the latter. Since the initial energy (before scattering) of violet rays is less than that of blue and cyan ones, the maximum energy in scattered light (scattered solar radiation) shifts to blue-blue rays, which determines the blue color of the sky. Thus, scattered radiation is richer in photosynthetically active rays than direct radiation.

In air containing impurities (small water droplets, ice crystals, dust particles, etc.), scattering is the same for all areas of visible radiation. Therefore, the sky takes on a whitish tint (haze appears). Cloud elements (large droplets and crystals) do not scatter the sun's rays at all, but diffusely reflect them. As a result, clouds illuminated by the Sun have white.

5. PAR (photosynthetically active radiation)

Photosynthetically active radiation. In the process of photosynthesis, not the entire spectrum of solar radiation is used, but only its

part located in the wavelength range 0.38...0.71 µm - photosynthetically active radiation (PAR).

It is known that visible radiation, perceived by the human eye as white, consists of colored rays: red, orange, yellow, green, blue, indigo and violet.

The absorption of solar radiation energy by plant leaves is selective. The leaves most intensively absorb blue-violet (X = 0.48...0.40 µm) and orange-red (X = 0.68 µm) rays, less - yellow-green (A. = 0.58... 0.50 µm) and far red (A. > 0.69 µm) rays.

At the earth's surface, the maximum energy in the spectrum of direct solar radiation, when the Sun is high, falls in the region of yellow-green rays (the solar disk is yellow). When the Sun is located near the horizon, the far red rays have maximum energy (the solar disk is red). Therefore, the energy of direct sunlight contributes little to the process of photosynthesis.

Since PAR is one of the most important factors in the productivity of agricultural plants, information on the amount of incoming PAR, taking into account its distribution over the territory and in time are of great practical importance.

The intensity of the phased array can be measured, but this requires special filters that transmit only waves in the range of 0.38...0.71 microns. There are such devices, but they are not used in the network of actinometric stations; they measure the intensity of the integral spectrum of solar radiation. The PAR value can be calculated from data on the arrival of direct, diffuse or total radiation using the coefficients proposed by X. G. Tooming and:

Qfar = 0.43 S" +0.57 D);

maps of the distribution of monthly and annual Fara amounts on the territory of Russia were compiled.

To characterize the degree of use of PAR by crops, a coefficient is used beneficial use PAR:

KPIfar= (amountQ/ headlights/amountQ/ headlights) 100%,

Where sumQ/ headlights- the amount of PAR spent on photosynthesis during the growing season of plants; sumQ/ headlights- the amount of PAR received for crops during this period;

Crops according to their average KPIFAr values ​​are divided into groups (by): usually observed - 0.5...1.5%; good - 1.5...3.0; record - 3.5...5.0; theoretically possible - 6.0...8.0%.

6. RADIATION BALANCE OF THE EARTH’S SURFACE

The difference between the incoming and outgoing fluxes of radiant energy is called the radiation balance of the earth's surface (B).

The incoming part of the radiation balance of the earth's surface during the day consists of direct solar and scattered radiation, as well as atmospheric radiation. The expenditure part of the balance is the radiation of the earth's surface and reflected solar radiation:

B= S / + D+ Ea-E3-Rk

The equation can be written in another form: B = Q- RK - Eph.

For night time, the radiation balance equation has the following form:

B = Ea - E3, or B = -Eeff.

If the radiation inflow is greater than the outflow, then the radiation balance is positive and the active surface* heats up. When the balance is negative, it cools. In summer, the radiation balance is positive during the day and negative at night. The zero crossing occurs in the morning approximately 1 hour after sunrise, and in the evening 1...2 hours before sunset.

The annual radiation balance in areas where stable snow cover is established has negative values ​​in the cold season and positive values ​​in the warm season.

The radiation balance of the earth's surface significantly affects the distribution of temperature in the soil and the surface layer of the atmosphere, as well as the processes of evaporation and snowmelt, the formation of fogs and frosts, changes in the properties of air masses (their transformation).

Knowledge of the radiation regime of agricultural land makes it possible to calculate the amount of radiation absorbed by crops and soil depending on the height of the Sun, the structure of the crop, and the phase of plant development. Data on the regime are also necessary for assessing various methods of regulating temperature, soil moisture, evaporation, on which the growth and development of plants, crop formation, its quantity and quality depend.

Effective agronomic techniques for influencing the radiation and, consequently, the thermal regime of the active surface are mulching (covering the soil with a thin layer of peat chips, rotted manure, sawdust, etc.), covering the soil with plastic film, and irrigation. All this changes the reflectivity and absorption capacity of the active surface.

* Active surface - the surface of soil, water or vegetation, which directly absorbs solar and atmospheric radiation and releases radiation into the atmosphere, thereby regulating the thermal regime of adjacent layers of air and underlying layers of soil, water, vegetation.

The most important source from which the Earth's surface and atmosphere receive thermal energy is the Sun. It sends a colossal amount of radiant energy into cosmic space: thermal, light, ultraviolet. Emitted by the Sun electromagnetic waves propagate at a speed of 300,000 km/s.

The heating of the earth's surface depends on the angle of incidence of the sun's rays. All the sun's rays arrive at the surface of the Earth parallel to each other, but since the Earth is spherical, the sun's rays fall on different parts of its surface at different angles. When the Sun is at its zenith, its rays fall vertically and the Earth heats up more.

The entire set of radiant energy sent by the Sun is called solar radiation, it is usually expressed in calories per unit surface area per year.

Solar radiation determines the temperature regime of the Earth's air troposphere.

It should be noted that total quantity solar radiation is more than two billion times the amount of energy received by the Earth.

Radiation reaching the earth's surface consists of direct and diffuse.

Radiation that comes to Earth directly from the Sun in the form of direct sunlight under a cloudless sky is called direct. It carries the greatest amount of heat and light. If our planet had no atmosphere, the earth's surface would receive only direct radiation.

However, passing through the atmosphere, approximately a quarter of solar radiation is scattered by gas molecules and impurities and deviates from the direct path. Some of them reach the surface of the Earth, forming scattered solar radiation. Thanks to scattered radiation, light penetrates into places where direct sunlight (direct radiation) does not penetrate. This radiation creates daylight and gives color to the sky.

Total solar radiation

All the sun's rays reaching the Earth are total solar radiation, i.e., the totality of direct and diffuse radiation (Fig. 1).

Rice. 1. Total solar radiation for the year

Distribution of solar radiation over the earth's surface

Solar radiation is distributed unevenly across the earth. It depends:

1. on air density and humidity - the higher they are, the less radiation the earth’s surface receives;

2. depending on the geographic latitude of the area - the amount of radiation increases from the poles to the equator. The amount of direct solar radiation depends on the length of the path that the sun's rays travel through the atmosphere. When the Sun is at its zenith (the angle of incidence of the rays is 90°), its rays hit the Earth through the shortest path and intensively release their energy to a small area. On Earth, this occurs in the band between 23° N. w. and 23° S. sh., i.e. between the tropics. As you move away from this zone to the south or north, the path length of the sun's rays increases, that is, the angle of their incidence on the earth's surface decreases. The rays begin to fall on the Earth at a smaller angle, as if sliding, approaching the tangent line in the region of the poles. As a result, the same energy flow is distributed over a larger area, so the amount of reflected energy increases. Thus, in the region of the equator, where the sun's rays fall on the earth's surface at an angle of 90°, the amount of direct solar radiation received by the earth's surface is higher, and as we move towards the poles, this amount sharply decreases. In addition, the length of the day depends on the latitude of the area. different times year, which also determines the amount of solar radiation entering the earth's surface;

3. from the annual and daily movement of the Earth - in the middle and high latitudes, the influx of solar radiation varies greatly according to the seasons, which is associated with changes in the midday altitude of the Sun and the length of the day;

4. on the nature of the earth's surface - the lighter the surface, the more sunlight it reflects. The ability of a surface to reflect radiation is called albedo(from Latin whiteness). Snow reflects radiation especially strongly (90%), sand weaker (35%), and black soil even weaker (4%).

Earth's surface absorbing solar radiation (absorbed radiation), heats up and radiates heat into the atmosphere (reflected radiation). The lower layers of the atmosphere largely block terrestrial radiation. The radiation absorbed by the earth's surface is spent on heating the soil, air, and water.

That part of the total radiation that remains after reflection and thermal radiation of the earth's surface is called radiation balance. The radiation balance of the earth's surface varies during the day and according to the seasons of the year, but on average per year it is positive value everywhere except the ice deserts of Greenland and Antarctica. The radiation balance reaches its maximum values ​​at low latitudes (between 20° N and 20° S) - over 42 * 10 2 J/m 2, at a latitude of about 60 ° in both hemispheres it decreases to 8 * 10 2 - 13*10 2 J/m 2.

The sun's rays give up to 20% of their energy to the atmosphere, which is distributed throughout the entire thickness of the air, and therefore the heating of the air they cause is relatively small. The sun heats the surface of the Earth, which transfers heat to the atmospheric air due to convection(from lat. convection- delivery), i.e. the vertical movement of air heated at the earth's surface, in place of which colder air descends. This is how the atmosphere receives most of its heat—on average, three times more than directly from the Sun.

The presence of carbon dioxide and water vapor does not allow heat reflected from the earth's surface to freely escape into outer space. They create greenhouse effect, thanks to which the temperature difference on Earth during the day does not exceed 15 °C. In the absence of carbon dioxide in the atmosphere, the earth's surface would cool by 40-50 °C overnight.

As a result of the growing scale economic activity people - burning coal and oil at thermal power plants, emissions from industrial enterprises, increasing automobile emissions - the content of carbon dioxide in the atmosphere increases, which leads to increased greenhouse effect and threatens global change climate.

The sun's rays, having passed through the atmosphere, hit the surface of the Earth and heat it, which, in turn, gives off heat to the atmosphere. This explains characteristic feature troposphere: decrease in air temperature with height. But there are cases when the higher layers of the atmosphere turn out to be warmer than the lower ones. This phenomenon is called temperature inversion(from Latin inversio - turning over).