Solar radiation is the radiation inherent in the luminary of our planetary system. The sun - main star, around which the Earth revolves, as well as neighboring planets. In fact, this is a huge hot gas ball, constantly emitting energy flows into the space around it. This is what they call radiation. Deadly, at the same time it is this energy - one of the main factors that make life possible on our planet. Like everything in this world, the benefits and harms of solar radiation for organic life are closely interrelated.

General view

To understand what solar radiation is, you must first understand what the Sun is. The main source of heat, which provides the conditions for organic existence on our planet, in the universal spaces is only a small star on the galactic outskirts of the Milky Way. But for earthlings, the Sun is the center of a mini-universe. After all, it is around this gas clot that our planet revolves. The sun gives us heat 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 an obvious proof of God's will. Attempts to delve into the essence of the phenomenon, to explain what this luminary is, have been made for a long time, and Copernicus made a particularly significant contribution to them, having formed the idea of ​​heliocentrism, which was strikingly different from the geocentrism generally accepted in that era. However, it is known for certain that even in ancient times, scientists more than once thought about what the Sun is, why it is so important for any life forms 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 take place 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 large knowledge base to say with confidence: it was possible to find out what the radiation emitted by the Sun is, how to measure this energy flow and how to formulate the features of its impact on various forms of organic life on Earth.

About terms

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 solar depths, which allows a huge amount of energy to be released into the space around the star. Trying to estimate the amount of solar radiation, efforts were made to determine the actual parameters of the environment on the star. Thus, the core temperature, 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 an attempt to estimate the amount of solar radiation, scientists have found that helium nuclei are inferior in mass to the total value of 4 protons required to form new structure. Thus, a feature of the reactions, called the "mass defect", was revealed. But in nature, nothing can disappear without a trace! In an attempt to find "escaped" quantities, scientists compared the energy recovery and the specifics of the change in mass. It was then that it was possible to reveal that the difference is emitted by gamma quanta.

The radiated 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 on their basis. Among other types of solar radiation is the light perceived by the human eye. Approximate estimates suggested that the process of passage of gamma rays takes about 10 million years. Another eight minutes - and the radiated energy reaches the surface of our planet.

How and what?

Solar radiation is called the total complex of electromagnetic radiation, which is characterized by a fairly wide range. This includes the so-called solar wind, that is, the energy flow formed by electrons, light particles. At the boundary layer of the atmosphere of our planet, the same intensity of solar radiation is constantly observed. The energy of a star is discrete, its transfer is carried out through quanta, while the corpuscular nuance is so insignificant that one can consider the rays as electromagnetic waves. And their distribution, as physicists have found out, 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:

• warmly;
• radio wave;
• White light;
• ultraviolet;
• gamma;
• x-ray.

The ratio of infrared, visible, ultraviolet best is 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.

Studies have shown that solar radiation is mainly absorbed by the planetary atmosphere. Due to this, heating occurs to a temperature comfortable for organic life, characteristic of the Earth. The existing ozone shell allows only one hundredth of the ultraviolet radiation to pass through. At the same time, short wavelengths that are dangerous to living beings are completely blocked. Atmospheric layers are able to scatter almost a third of the sun's rays, another 20% are absorbed. Consequently, no more than half of all energy reaches the surface of the planet. It is this "residue" in science that is called direct solar radiation.

How about in more detail?

Several aspects are known that determine how intense direct radiation will be. The most significant are the angle of incidence, which depends on latitude (a geographical characteristic of the terrain on the globe), the time of year, which determines how great the distance to a particular 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, namely, its ability to reflect the incoming waves, plays a role.

Total solar radiation is a value that combines scattered volumes and direct radiation. The parameter used to estimate the intensity is estimated in calories per unit area. At the same time, it is remembered that at different times of the day the values ​​inherent in 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 that the air does not get the opportunity to warm up. Therefore, the farther from the equator, the lower the total indicators of solar wave radiation will be.

As scientists have found out, the energy of solar radiation has a serious impact on planetary climate, subjugates the vital activity of various organisms that exist on Earth. In our country, as well as in the territory of its nearest neighbors, 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 is heated, gradually transferring thermal energy to air masses. This helps to maintain a comfortable climate, maintain conditions for the existence of organic life. If there are no serious failures, the climate remains conditionally unchanged, which means that all creatures can live in their usual conditions.

Our luminary is not the only source of infrared spectrum waves. Similar radiation is characteristic of any heated object, including an ordinary battery in a human house. It is on the principle of infrared radiation perception that numerous devices work, making it possible to see heated bodies in the dark, otherwise uncomfortable conditions for the eyes. By the way, according to a similar principle, the ones that have become so popular in recent times compact devices for assessing through which parts of the building the greatest heat losses occur. These mechanisms are especially widespread among builders, as well as owners of private houses, as they help to identify through which areas heat is lost, organize their protection and prevent unnecessary energy consumption.

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

It's curious

Based on the study of solar radiation factors, it was possible to create truly unique devices called thermographs. They make it possible to timely detect various diseases that are not available for detection in other ways. This is how you can find cancer or a blood clot. IR to some extent protects against ultraviolet radiation, which is dangerous for organic life, which made it possible to use waves of this spectrum to restore the health of astronauts who were 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 is still not fully explored. Scientists know that its improper use can 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 impaired functioning of the heart, blood vessels, including those located in the brain.

visible light

One of the elements of total solar radiation is the light visible to the human eye. Wave beams propagate in straight lines, so there is no superposition on each other. At one time, this became the topic of a considerable number scientific works: scientists set out to understand why there are so many shades around us. It turned out that the key parameters of light play a role:

• refraction;
• reflection;
• absorption.

As the scientists found out, objects are not capable of being sources of visible light on their own, but they can absorb radiation and reflect it. Reflection angles, wave frequency vary. Over the centuries, the ability of a person to see has been gradually improved, but certain limitations are due to the biological structure of the eye: 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 light features not only became the subject of many works, but also were the basis for the birth of a new physical discipline. At the same time, non-scientific practices, theories appeared, the adherents of which believe that color can affect the physical state of a person, the 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 the total solar radiation is the ultraviolet study, formed by waves of large, medium and small lengths. They differ from each other both in physical parameters and in the peculiarities of their influence on the forms of organic life. Long ultraviolet waves, for example, in the atmospheric layers are mainly scattered, and before earth's surface get only a small percentage. 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. Such 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, 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;
• dilates blood vessels;
• stimulates the immune system;
• leads to the formation of endorphins, which means that nervous overexcitation decreases.

but on the other hand

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

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

Continuous ultraviolet irradiation provokes a violation of appetite, the functioning of the central nervous system, the immune system. Also, my head starts to hurt. The described symptoms are classic manifestations sunstroke. The person himself cannot always realize what is happening - the condition worsens gradually. If it is noticeable that someone nearby has become ill, first aid should be provided. The scheme is as follows:

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

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

How to sunbathe properly?

In order not to learn from experience how unpleasant the excessive amount of solar radiation received during 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 negative impact waves. Under the influence of this substance, the skin becomes darker, and the shade turns into bronze. To this day, disputes about how useful and harmful it is for a person do not subside.

On the one hand, sunburn 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, tan is considered fashionable and beautiful. In order to minimize risks for yourself, it is reasonable to analyze before starting beach procedures how dangerous the amount of solar radiation received during sunbathing is, how to minimize risks for yourself. To make the experience as pleasant as possible, sunbathers should:

• to drink a lot of water;
• use skin protection products;
• sunbathe in the evening or in the morning;
• do not operate under direct sunlight more than an hour;
• do not drink alcohol;
• include foods rich in selenium, tocopherol, tyrosine in the menu. Don't forget about beta-carotene.

The value of solar radiation for the human body is exceptionally high, both positive and negative aspects should not be overlooked. It should be recognized that in different people biochemical reactions occur with individual characteristics, so for someone and half-hour sunbathing can be dangerous. It is reasonable to consult a doctor before the beach season, assess the type and condition of the skin. This will help prevent harm to health.

If possible, sunburn should be avoided in old age, during the period of bearing a baby. Not compatible with sunbathing cancer diseases, mental disorders, skin pathologies and insufficiency of the functioning of the heart.

Total radiation: where is the shortage?

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

The ultraviolet is absorbed to some extent by the oxygen layer. This is characteristic of radiation with a wavelength of 0.13-0.24 microns. Carbon dioxide, water vapor can absorb a small percentage of the infrared spectrum. 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 here. Inhomogeneous elements, particles whose dimensions are inferior to the wavelength, provoke molecular scattering, and for larger ones, the phenomenon described by the indicatrix, that is, aerosol, is characteristic.

The rest of the solar radiation reaches the earth's surface. It combines direct radiation, diffused.

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, the altitude of the celestial body, the type of earth's surface in this area, and 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 cloudiness in the total radiation, diffuse is one fourth.

Our country belongs to the northern ones, so most of the year in southern regions 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 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 daylight hours more than in other months of the year. At the same time, 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 wave radiation is observed at noon, and the annual maximum occurs in June, when the sun is highest in the sky.

The total solar radiation is the amount solar energy reaching our planet. At the same time, it must be remembered that various atmospheric factors lead to the fact that the annual arrival of total radiation is less than it could be. The biggest difference between the actually observed and the maximum possible is typical for the Far Eastern regions in the summer. Monsoons provoke exceptionally dense clouds, so the total radiation is reduced by about half.

curious to know

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

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

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

Based on 12 months, special attention should be paid to astronomical phenomena as determining the overall numerical indicators. At the same time, cloudiness leads to the fact that the real radiation maximum can 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 a mortal danger to humans. As early as 1964, an important popular science work on defense methods was published. Its authors were Soviet scientists Kamanin, 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 it should be within 15 R. For short-term exposure, the limit for a person is 600 R. Space flights, especially in unpredictable conditions solar activity, may be accompanied by significant exposure of astronauts, which obliges to take additional measures to protect against waves of different lengths.

After the Apollo missions, during which methods of protection were tested, factors affecting human health were studied, more than one decade has passed, but to this day scientists cannot find effective, reliable methods for predicting geomagnetic storms. You can make a forecast for hours, sometimes for several days, but even for a weekly forecast, the chances of realization 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, can fall into powerful radiation fluxes. This makes even more important the issue of both research and prediction of radiation features, and the development of methods of protection against it.

Solar radiation is the leading climate-forming factor and practically the only source of energy for all physical processes occurring on the earth's surface and in its atmosphere. It determines the vital activity of organisms, creating one or another temperature regime; leads to the formation of clouds and precipitation; is the fundamental cause of the general circulation of the atmosphere, thereby exerting a huge impact on human life in all its manifestations. In construction and architecture, solar radiation is the most important environmental factor - the orientation of buildings, their constructive, space-planning, coloristic, plastic solutions and many other features depend on it.

According to GOST R 55912-2013 "Construction Climatology", the following definitions and concepts related to solar radiation are adopted:

• direct radiation - part of the total solar radiation entering the surface in the form of a beam of parallel rays coming directly from the visible disk of the sun;
• scattered solar radiation- part of the total solar radiation coming to the surface from the entire sky after scattering in the atmosphere;
• reflected radiation- part of the total solar radiation reflected from the underlying surface (including from the facades, roofs of buildings);
• solar radiation intensity- the amount of solar radiation passing per unit of time through a single area located perpendicular to the rays.

All values ​​of solar radiation in modern domestic state standards, joint ventures (SNiPs) and other regulatory documents related to construction and architecture are measured in kilowatts per hour per 1 m 2 (kW h / m 2). As a rule, a month is taken as a unit of time. To get the instantaneous (second) value of the power of the solar radiation flux (kW / m 2), the value given for the month should be divided by the number of days in a month, the number of hours in a day and seconds in hours.

In many early editions of building regulations and in many modern reference books on climatology, solar radiation values ​​are given in megajoules or kilocalories per m 2 (MJ / m 2, Kcal / m 2). The coefficients for the conversion of these quantities from one to another are given in Appendix 1.

physical entity. Solar radiation comes to Earth from the Sun. The Sun is the closest star to us, which is on average 149,450,000 km away from the Earth. In early July, when the Earth is at its furthest from the Sun (“aphelion”), this distance increases to 152 million km, and in early January it decreases to 147 million km (“perihelion”).

Inside the solar core, the temperature exceeds 5 million K, and the pressure is several billion times greater than that of the earth, as a result of which hydrogen turns into helium. In the course of this thermonuclear reaction, radiant energy is born, which propagates from the Sun in all directions in the form of electromagnetic waves. At the same time, a whole spectrum of wavelengths comes to the Earth, which in meteorology is usually divided into short-wave and long-wave sections. shortwave call radiation in the wavelength range from 0.1 to 4 microns (1 micron \u003d 10 ~ 6 m). Radiation with long lengths (from 4 to 120 microns) is referred to as longwave. Solar radiation is predominantly shortwave - the indicated wavelength range accounts for 99% of all solar radiation energy, while the earth's surface and atmosphere emit longwave radiation, and can only reflect shortwave radiation.

The sun is a source of not only energy, but also light. Visible light occupies a narrow range of wavelengths, only from 0.40 to 0.76 microns, but 47% of all solar radiant energy is contained in this interval. Light with a wavelength of about 0.40 microns is perceived as violet, with a wavelength of about 0.76 microns - as red. All other wavelengths are not perceived by the human eye; they are invisible to us 1 . Infrared radiation (from 0.76 to 4 microns) accounts for 44%, and ultraviolet (from 0.01 to 0.39 microns) - 9% of all energy. The maximum energy in the spectrum of solar radiation at the upper boundary of the atmosphere lies in the blue-blue region of the spectrum, and near the earth's surface - in the yellow-green.

A quantitative measure of solar radiation entering a certain surface is energy illumination, or flux of solar radiation, - the amount of radiant energy incident on a unit area per unit time. The maximum amount of solar radiation enters the upper boundary of the atmosphere and is characterized by the value of the solar constant. Solar constant - is the flux of solar radiation at the upper boundary of the earth's atmosphere through an area perpendicular to the sun's rays, at an average distance of the Earth from the Sun. According to the latest data approved by the World Meteorological Organization (WMO) in 2007, this value is 1.366 kW / m 2 (1366 W / m 2).

Much less solar radiation reaches the earth's surface, since as the sun's rays move through the atmosphere, the radiation undergoes a series significant changes. Part of it is absorbed by atmospheric gases and aerosols and passes into heat, i.e. goes to warm the atmosphere, and part is dissipated and goes into special form scattered radiation.

Process takeovers radiation in the atmosphere is selective in nature - different gases absorb it in different parts of the spectrum and to different degrees. The main gases that absorb solar radiation are water vapor (H 2 0), ozone (0 3) and carbon dioxide (CO 2). For example, as mentioned above, stratospheric ozone completely absorbs radiation harmful to living organisms with wavelengths shorter than 0.29 microns, which is why the ozone layer is a natural shield for the existence of life on Earth. On average, ozone absorbs about 3% of solar radiation. In the red and infrared regions of the spectrum, water vapor absorbs solar radiation most significantly. In the same region of the spectrum are the absorption bands of carbon dioxide, however

More details about light and color are discussed in other sections of the discipline "Architectural Physics".

in general, its absorption of direct radiation is small. Absorption of solar radiation occurs both by aerosols of natural and anthropogenic origin, especially strongly by soot particles. In total, about 15% of solar radiation is absorbed by water vapor and aerosols, and about 5% by clouds.

Scattering radiation is a physical process of interaction between electromagnetic radiation and matter, during which molecules and atoms absorb part of the radiation, and then re-emit it in all directions. This is very important process, which depends on the ratio of the size of the scattering particles and the wavelength of the incident radiation. In absolutely pure air, where scattering is produced only by gas molecules, it obeys Rayleigh law, i.e. inversely proportional to the fourth power of the wavelength of the scattered rays. Thus, the blue color of the sky is the color of the air itself, due to the scattering of sunlight in it, since violet and blue rays are scattered by air much better than orange and red ones.

If there are particles in the air whose dimensions are comparable to the wavelength of radiation - aerosols, water droplets, ice crystals - then the scattering will not obey Rayleigh's law, and the scattered radiation will not be so rich in short-wavelength rays. On particles with a diameter greater than 1-2 microns, not scattering will occur, but diffuse reflection, which determines the whitish color of the sky.

Scattering plays a huge role in the formation of natural light: in the absence of the Sun during the daytime, it creates scattered (diffuse) light. If there were no scattering, it would be light only where direct sunlight would fall. Dusk and dawn, the color of the clouds at sunrise and sunset are also associated with this phenomenon.

So, solar radiation reaches the earth's surface in the form of two streams: direct and diffuse radiation.

direct radiation(5) comes to the earth's surface directly from the solar disk. In this case, the maximum possible amount of radiation will be received by a single site located perpendicular to the sun's rays (5). per unit horizontal surface will have a smaller amount of radiant energy Y, also called insolation:

Y \u003d? -8shA 0, (1.1)

where And 0- The height of the sun above the horizon, which determines the angle of incidence of the sun's rays on a horizontal surface.

scattered radiation(/)) comes to the earth's surface from all points of the firmament, with the exception of the solar disk.

All solar radiation reaching the earth's surface is called total solar radiation (0:

• (1.2)
• 0 = + /) = And 0+ /).

The arrival of these types of radiation significantly depends not only on astronomical causes, but also on cloudiness. Therefore, in meteorology it is customary to distinguish possible amounts of radiation observed under cloudless conditions, and actual amounts of radiation taking place under real cloudiness conditions.

Not all solar radiation falling on the earth's surface is absorbed by it and converted into heat. Part of it is reflected and therefore lost by the underlying surface. This part is called reflected radiation(/? k), and its value depends on albedo ground surface (L to):

A k = - 100%.

The albedo value is measured in fractions of a unit or as a percentage. In construction and architecture, fractions of a unit are more often used. They also measure the reflectivity of building and finishing materials, the lightness of facades, etc. In climatology, albedo is measured as a percentage.

Albedo has a significant impact on the formation of the Earth's climate, as it is an integral indicator of the reflectivity of the underlying surface. It depends on the state of this surface (roughness, color, moisture) and varies over a very wide range. The highest albedo values ​​(up to 75%) are characteristic of freshly fallen snow, while the lowest values ​​are characteristic of the water surface during sheer sunlight (“3%). The albedo of the soil and vegetation surface varies on average from 10 to 30%.

If we consider the entire Earth as a whole, then its albedo is 30%. This value is called Earth's planetary albedo and represents the ratio of the reflected and scattered solar radiation leaving into space to the total amount of radiation entering the atmosphere.

On the territory of cities, the albedo is, as a rule, lower than in natural, undisturbed landscapes. Characteristic value of albedo for the territory major cities temperate climate is 15-18%. In southern cities, the albedo is, as a rule, higher due to the use of lighter tones in the color of facades and roofs; in northern cities with dense buildings and dark color schemes of buildings, the albedo is lower. This allows in hot southern countries to reduce the amount of absorbed solar radiation, thereby reducing the thermal background of buildings, and in the northern cold regions, on the contrary, to increase the share of absorbed solar radiation, increasing the overall thermal background.

Absorbed radiation(* U P0GL) is also called balance of shortwave radiation (VK) and is the difference between the total and reflected radiation (two short-wave fluxes):

^abs \u003d 5 k = 0~ I K- (1.4)

It heats the upper layers of the earth's surface and everything that is located on it (vegetation cover, roads, buildings, structures, etc.), as a result of which they emit long-wave radiation invisible to the human eye. This radiation is often called own radiation of the earth's surface(? 3). Its value, according to the Stefan-Boltzmann law, is proportional to the fourth degree absolute temperature.

The atmosphere also emits long-wave radiation, most of which reaches the earth's surface and is almost completely absorbed by it. This radiation is called counter radiation of the atmosphere (E a). The counter radiation of the atmosphere increases with increasing cloudiness and air humidity and is a very important source of heat for the earth's surface. However, the long-wave radiation of the atmosphere is always slightly less than the earth's, due to which the earth's surface loses heat, and the difference between these values ​​is called effective radiation of the Earth (E ef).

On average, in temperate latitudes, the earth's surface through effective radiation loses about half of the amount of heat that it receives from absorbed solar radiation. By absorbing terrestrial radiation and sending counter radiation to the earth's surface, the atmosphere reduces the cooling of this surface at night. During the day, it does little to prevent the heating of the Earth's surface. This influence of the earth's atmosphere on the thermal regime of the earth's surface is called greenhouse effect. Thus, the phenomenon of the greenhouse effect consists in the retention of heat near the surface of the Earth. An important role in this process is played by gases of technogenic origin, primarily carbon dioxide, whose concentration in urban areas is especially high. But the main role still belongs to the gases of natural origin.

The main substance in the atmosphere that absorbs long-wave radiation from the Earth and sends back radiation is water vapor. It absorbs almost all long-wave radiation except for the wavelength range from 8.5 to 12 microns, which is called "transparency window" water vapor. Only in this interval does the terrestrial radiation pass into the world space through the atmosphere. In addition to water vapor, carbon dioxide strongly absorbs long-wave radiation, and it is in the transparency window of water vapor that ozone is much weaker, as well as methane, nitrogen oxide, chlorofluorocarbons (freons) and some other gas impurities.

Keeping heat close to the earth's surface is a very important process for sustaining life. Without it, the average temperature of the Earth would be 33 ° C lower than the current one, and living organisms could hardly live on the Earth. Therefore, the point is not in the greenhouse effect as such (after all, it arose from the moment the atmosphere was formed), but in the fact that under the influence of anthropogenic activity, gain this effect. The reason is the rapid growth in the concentration of greenhouse gases of technogenic origin, mainly CO 2 emitted during the combustion of fossil fuels. This can lead to the fact that with the same incoming radiation, the proportion of heat remaining on the planet will increase, and, consequently, the temperature of the earth's surface and atmosphere will also increase. Over the past 100 years, the air temperature of our planet has increased by an average of 0.6 ° C.

It is believed that when the concentration of CO 2 doubles relative to its pre-industrial value global warming will be about 3°C ​​(according to various estimates - from 1.5 to 5.5°C). In this case, the greatest changes should occur in the troposphere of high latitudes in the autumn-winter period. As a result, the ice in the Arctic and Antarctica will begin to melt and the level of the World Ocean will begin to rise. This increase can range from 25 to 165 cm, which means that many cities located in the coastal zones of the seas and oceans will be flooded.

Thus, this is a very important issue affecting the lives of millions of people. With this in mind, in 1988 the first International Conference on the problem of anthropogenic climate change was held in Toronto. Scientists have come to the conclusion that the consequences of an increase in the greenhouse effect due to an increase in the content of carbon dioxide in the atmosphere are second only to the consequences of a global nuclear war. At the same time, the Intergovernmental Panel on Climate Change (IPCC) was formed at the United Nations (UN). IPCC - Intergovernmental Panel on Climate Change), which studies the impact of an increase in surface temperature on the climate, the ecosystem of the World Ocean, the biosphere as a whole, including the life and health of the planet's population.

In 1992, the Framework Convention on Climate Change (FCCC) was adopted in New York, the main goal of which was proclaimed to ensure the stabilization of greenhouse gas concentrations in the atmosphere at levels that prevent dangerous consequences human intervention in the climate system. For the practical implementation of the convention in December 1997 in Kyoto (Japan) for international conference the Kyoto Protocol was adopted. It defines specific quotas for greenhouse gas emissions by member countries, including Russia, which ratified this Protocol in 2005.

At the time of writing this book, one of the latest conferences on climate change is the Climate Conference in Paris, which took place from November 30 to December 12, 2015. The purpose of this conference is to sign an international agreement to curb the increase in the average temperature of the planet by 2100 no higher 2°C.

So, as a result of the interaction of various flows of short-wave and long-wave radiation, the earth's surface continuously receives and loses heat. The resulting value of the incoming and outgoing radiation is radiation balance (AT), which determines the thermal state of the earth's surface and the surface layer of air, namely their heating or cooling:

AT = Q- «k - ?ef \u003d 60 - BUT)-? ef =

= (5 "sin / ^ > + D) (l-A) -E ^ f \u003d B to + B a. (

Radiation balance data are needed to estimate the degree of heating and cooling various surfaces both in natural conditions and in the architectural environment, calculation of the thermal regime of buildings and structures, determination of evaporation, heat reserves in the soil, regulation of irrigation of agricultural fields and other national economic purposes.

Measurement methods. The key importance of studies of the Earth's radiation balance for understanding the patterns of climate and the formation of microclimatic conditions determines the fundamental role of observational data on its components - actinometric observations.

At meteorological stations in Russia, thermoelectric method measurements of radiation fluxes. The measured radiation is absorbed by the black receiving surface of the devices, turns into heat and heats the active junctions of the thermopile, while the passive junctions are not heated by radiation and have a lower temperature. Due to the difference in temperatures of active and passive junctions, a thermoelectromotive force arises at the output of the thermopile, which is proportional to the intensity of the measured radiation. Thus, most actinometric instruments are relative- they do not measure the radiation fluxes themselves, but quantities proportional to them - current strength or voltage. To do this, devices are connected, for example, to digital multimeters, and earlier to pointer galvanometers. At the same time, in the passport of each device, the so-called "conversion factor" - division price of an electrical measuring instrument (W / m 2). This multiplier is calculated by comparing the readings of one or another relative instrument with the readings absolute appliances - pyrheliometers.

The principle of operation of absolute devices is different. So, in the Angstrom compensation pyrheliometer, the blackened metal plate exposed to the sun, while another similar plate remains in the shade. A temperature difference arises between them, which is transferred to the junctions of the thermoelement attached to the plates, and thus a thermoelectric current is excited. In this case, current from the battery is passed through the shaded plate until it heats up to the same temperature as the plate in the sun, after which the thermoelectric current disappears. By the strength of the passed "compensating" current, you can determine the amount of heat received by the blackened plate, which, in turn, will be equal to the amount of heat received from the Sun by the first plate. Thus, it is possible to determine the amount of solar radiation.

At the meteorological stations of Russia (and earlier - the USSR), conducting observations of the components of the radiation balance, the homogeneity of the series of actinometric data is ensured by the use of the same type of instruments and their careful calibration, as well as the same measurement and data processing methods. As receivers of integral solar radiation (

In the Savinov-Yanishevsky thermoelectric actinometer, the appearance of which is shown in Fig. 1.6, the receiving part is a thin metal blackened disk of silver foil, to which the odd (active) junctions of the thermopile are glued through the insulation. During measurements, this disk absorbs solar radiation, as a result of which the temperature of the disk and active junctions rises. The even (passive) junctions are glued through the insulation to the copper ring in the device case and have a temperature close to the outside temperature. This temperature difference, when the external circuit of the thermopile is closed, creates a thermoelectric current, the strength of which is proportional to the intensity of solar radiation.

Rice. 1.6.

In a pyranometer (Fig. 1.7), the receiving part is most often a battery of thermoelements, for example, from manganin and constantan, with blackened and white junctions, which are heated differently under the action of incoming radiation. The receiving part of the device must have a horizontal position in order to perceive scattered radiation from the entire firmament. From direct radiation, the pyranometer is shaded by a screen, and from the oncoming radiation of the atmosphere it is protected by a glass cap. When measuring total radiation, the pyranometer is not shaded from direct rays.

Rice. 1.7.

A special device (folding plate) allows you to give the head of the pyranometer two positions: receiver up and receiver down. In the latter case, the pyranometer measures short-wave radiation reflected from the earth's surface. In route observations, the so-called camping albe-meter, which is a pyranometer head connected to a tilting gimbal suspension with a handle.

The thermoelectric balance meter consists of a body with a thermopile, two receiving plates and a handle (Fig. 1.8). The disc-shaped body (/) has a square cutout where the thermopile is fixed (2). Handle ( 3 ), soldered to the body, serves to install the balance meter on the rack.

Rice. 1.8.

One blackened receiving plate of the balance meter is directed upwards, the other downwards, towards the earth's surface. The principle of operation of an unshaded balance meter is based on the fact that all types of radiation coming to the active surface (Y, /) and E a), are absorbed by the blackened receiving surface of the device, facing upwards, and all types of radiation leaving the active surface (/? k, /? l and E 3), absorbed by the downward facing plate. Each receiving plate itself also emits long-wave radiation, in addition, there is heat exchange with the surrounding air and the body of the device. However, due to the high thermal conductivity of the body, a large heat transfer occurs, which does not allow the formation of a significant temperature difference between the receiving plates. For this reason, the self-radiation of both plates can be neglected, and the difference in their heating can be used to determine the value of the radiation balance of any surface in the plane of which the balance meter is located.

Since the receiving surfaces of the balance meter are not covered with a glass dome (otherwise it would be impossible to measure long-wave radiation), the readings of this device depend on the wind speed, which reduces the temperature difference between the receiving surfaces. For this reason, the readings of the balance meter lead to calm conditions, having previously measured the wind speed at the level of the device.

For automatic registration measurements, the thermoelectric current arising in the devices described above is fed to a self-recording electronic potentiometer. Changes in current strength are recorded on a moving paper tape, while the actinometer must automatically rotate so that its receiving part follows the Sun, and the pyranometer must always be shaded from direct radiation by a special ring protection.

Actinometric observations, in contrast to the main meteorological observations, are carried out six times a day at the following times: 00:30, 06:30, 09:30, 12:30, 15:30 and 18:30. Since the intensity of all types of short-wave radiation depends on the height of the Sun above the horizon, the timing of observations is set according to mean solar time stations.

characteristic values. The values ​​of direct and total radiation fluxes play one of the most important roles in architectural and climatic analysis. It is with their consideration that the orientation of buildings on the sides of the horizon, their space-planning and coloristic solution, internal layout, dimensions of light openings and a number of other architectural features are connected. Therefore, the daily and annual course characteristic values will be considered precisely for these values ​​of solar radiation.

Energy illumination direct solar radiation in a cloudless sky depends on the height of the sun, the properties of the atmosphere in the path of the sun's ray, characterized by transparency factor(a value showing what fraction of solar radiation reaches the earth's surface during a sheer incidence of sunlight) and the length of this path.

Direct solar radiation with a cloudless sky has a fairly simple daily variation with a maximum around noon (Fig. 1.9). As follows from the figure, during the day, the solar radiation flux first rapidly, then more slowly increases from sunrise to noon and slowly at first, then rapidly decreases from noon to sunset. Differences in energy illumination at noon at clear sky in January and July are primarily due to differences in the Sun's noon height, which is lower in winter than in summer. At the same time, in continental regions, an asymmetry of the diurnal variation is often observed, due to the difference in the transparency of the atmosphere in the morning and afternoon hours. The transparency of the atmosphere also affects the annual course of average monthly values ​​of direct solar radiation. The maximum radiation in a cloudless sky can shift by spring months, since in spring the dust content and moisture content of the atmosphere are lower than in autumn.

5 1 , kW/m 2

b", kW / m 2

Rice. 1.9.

and under average cloudiness conditions (b):

7 - on the surface perpendicular to the rays in July; 2 - on a horizontal surface in July; 3 - on a perpendicular surface in January; 4 - on a horizontal surface in January

Cloudiness reduces the arrival of solar radiation and can significantly change its daily course, which is manifested in the ratio of pre- and post-noon hourly sums. Thus, in most of the continental regions of Russia in the spring-summer months, the hourly amounts of direct radiation in the pre-noon hours are greater than in the afternoon (Fig. 1.9, b). This is mainly determined by the daily course of cloudiness, which begins to develop at 9-10 am and reaches a maximum in the afternoon, thus reducing radiation. The general decrease in the influx of direct solar radiation under actual cloudy conditions can be very significant. For example, in Vladivostok, with its monsoon climate, these losses in summer amount to 75%, and in St. Petersburg, even on average per year, clouds do not transmit 65% of direct radiation to the earth's surface, in Moscow - about half.

Distribution annual amounts direct solar radiation under average cloudiness over the territory of Russia is shown in fig. 1.10. To a large extent, this factor, which reduces the amount of solar radiation, depends on the circulation of the atmosphere, which leads to a violation of the latitudinal distribution of radiation.

As can be seen from the figure, on the whole, the annual amounts of direct radiation arriving on a horizontal surface increase from high to lower latitudes from 800 to almost 3000 MJ/m 2 . A large number of clouds in the European part of Russia leads to a decrease in annual totals compared to the regions of Eastern Siberia, where, mainly due to the influence of the Asian anticyclone, annual totals increase in winter. At the same time, the summer monsoon leads to a decrease in the annual radiation inflow in coastal areas by Far East. The range of changes in the midday intensity of direct solar radiation on the territory of Russia varies from 0.54-0.91 kW / m 2 in summer to 0.02-0.43 kW / m 2 in winter.

scattered radiation, arriving at a horizontal surface also changes during the day, increasing before noon and decreasing after it (Fig. 1.11).

As in the case of direct solar radiation, the arrival of scattered radiation is affected not only by the height of the sun and the length of the day, but also by the transparency of the atmosphere. However, a decrease in the latter leads to an increase in scattered radiation (in contrast to direct radiation). In addition, scattered radiation depends on cloudiness to a very wide extent: under average cloudiness, its arrival is more than twice the values ​​observed in clear skies. On some days, cloudiness increases this figure by 3-4 times. Thus, scattered radiation can significantly supplement the direct line, especially at a low position of the Sun.

Rice. 1.10. Direct solar radiation arriving on a horizontal surface under average cloudiness, MJ / m 2 per year (1 MJ / m 2 \u003d 0.278 kW h / m 2)

/), kW / m 2 0.3 g

• 0,2 -
• 0,1 -

4 6 8 10 12 14 16 18 20 22 hours

Rice. 1.11.

and under average cloudy conditions (b)

The value of scattered solar radiation in the tropics is from 50 to 75% of the direct; at 50-60° latitude it is close to a straight line, and at high latitudes it exceeds direct solar radiation for almost the entire year.

Highly an important factor, affecting the scattered radiation flux, is albedo underlying surface. If the albedo is large enough, then the radiation reflected from the underlying surface, scattered by the atmosphere in reverse direction, can cause a significant increase in the arrival of scattered radiation. The effect is most pronounced in the presence of snow cover, which has the highest reflectivity.

Total radiation in a cloudless sky (possible radiation) depends on the latitude of the place, the height of the sun, the optical properties of the atmosphere and the nature of the underlying surface. Under clear sky conditions, it has a simple diurnal variation with a maximum at noon. The asymmetry of the diurnal variation, characteristic of direct radiation, is little manifested in the total radiation, since the decrease in direct radiation due to an increase in atmospheric turbidity in the second half of the day is compensated by an increase in scattered radiation due to the same factor. In the annual course, the maximum intensity of total radiation with a cloudless sky over most of the territory

The territory of Russia is observed in June due to the maximum midday height of the sun. However, in some regions this influence is overlapped by the influence of atmospheric transparency, and the maximum is shifted to May (for example, in Transbaikalia, Primorye, Sakhalin, and in a number of regions of Eastern Siberia). The distribution of monthly and annual total solar radiation in a cloudless sky is given in Table. 1.9 and in fig. 1.12 as latitude-averaged values.

From the above table and figure, it can be seen that in all seasons of the year, both the intensity and the amount of radiation increase from north to south in accordance with the change in the height of the sun. The exception is the period from May to July, when the combination of a long day and the height of the sun provides rather high values ​​of total radiation in the north and, in general, on the territory of Russia, the radiation field is blurred, i.e. has no pronounced gradients.

Table 1.9

Total solar radiation on a horizontal surface

with a cloudless sky (kW h / m 2)

	Geographic latitude, ° N
September

Rice. 1.12. Total solar radiation to a horizontal surface with a cloudless sky at different latitudes (1 MJ / m 2 \u003d 0.278 kWh / m 2)

In the presence of clouds total solar radiation is determined not only by the number and shape of clouds, but also by the state of the solar disk. When the solar disk is translucent through the clouds, the total radiation compared to cloudless conditions can even increase due to the growth of scattered radiation.

For medium cloudy conditions, a completely regular daily course of total radiation is observed: a gradual increase from sunrise to noon and a decrease from noon to sunset. At the same time, the daily course of cloudiness violates the symmetry of the course relative to noon, which is characteristic of a cloudless sky. Thus, in most regions of Russia during the warm period, the pre-noon values ​​of total radiation are 3-8% higher than the afternoon values, with the exception of the monsoon regions of the Far East, where the ratio is reversed. In the annual course of the average multi-year monthly sums of total radiation, along with the determining astronomical factor, a circulation factor is manifested (through the influence of cloudiness), so the maximum can shift from June to July and even to May (Fig. 1.13).

• 600 -
• 500 -
• 400 -
• 300 -
• 200 -

m. Chelyuskin

Salekhard

Arkhangelsk

St. Petersburg

Petropavlovsk

Kamchatsky

Khabarovsk

Astrakhan

Rice. 1.13. Total solar radiation on a horizontal surface in individual cities of Russia under real cloudiness conditions (1 MJ / m 2 \u003d 0.278 kW h / m 2)

5", MJ/m 2 700

So, the real monthly and annual arrival of the total radiation is only a part of the possible. The largest deviations of real amounts from those possible in summer are noted in the Far East, where cloudiness reduces the total radiation by 40-60%. In general, the total annual income of total radiation varies across the territory of Russia in the latitudinal direction, increasing from 2800 MJ / m 2 on the coasts of the northern seas to 4800-5000 MJ / m 2 in the southern regions of Russia - the North Caucasus, the Lower Volga region, Transbaikalia and Primorsky Krai (Fig. 1.14).

Rice. 1.14. Total radiation entering a horizontal surface, MJ / m 2 per year

In summer, the differences in total solar radiation under real cloudiness conditions between cities located at different latitudes are not as “dramatic” as it might seem at first glance. For the European part of Russia from Astrakhan to Cape Chelyuskin, these values ​​lie in the range of 550-650 MJ/m 2 . In winter, in most cities, with the exception of the Arctic, where the polar night sets in, the total radiation is 50-150 MJ / m 2 per month.

For comparison: the average heat values ​​for January for 1 urban area (calculated according to actual data for Moscow) range from 220 MJ/m2 per month in urban urban development hubs to 120-150 MJ/m2 in inter-main areas with low-density residential development. On the territories of industrial and communal storage zones, the heat index in January is 140 MJ/m 2 . The total solar radiation in Moscow in January is 62 MJ/m 2 . Thus, in winter time due to the use of solar radiation, it is possible to cover no more than 10-15% (taking into account the efficiency of solar panels 40%) of the calculated calorific value of medium-density buildings even in Irkutsk and Yakutsk, known for their sunny winter weather, even if their territory is completely covered with photovoltaic panels.

In summer, total solar radiation increases by 6-9 times, and heat consumption is reduced by 5-7 times compared to winter. Heat values ​​in July decrease to 35 MJ/m 2 or less in residential areas and 15 MJ/m 2 or less in industrial areas, i.e. up to values ​​constituting no more than 3-5% of the total solar radiation. Therefore, in summer, when the need for heating and lighting is minimal, there is an excess of this renewable energy throughout Russia. natural resource, which cannot be recycled, which once again calls into question the feasibility of using photovoltaic panels, according to at least, in cities and apartment buildings.

Electricity consumption (without heating and hot water), also associated with uneven distribution total area development, population density and functional purpose of various territories, is in the

Warmth - an average indicator of the consumption of all types of energy (electricity, heating, hot water supply) per 1 m 2 of the building area.

cases from 37 MJ / m 2 per month (calculated as 1/12 of the annual amount) in densely built-up areas and up to 10-15 MJ / m 2 per month in areas with low building density. During the daytime and in summer, electricity consumption naturally falls. Electricity consumption density in July in most areas of residential and mixed development is 8-12 MJ/m 2 with total solar radiation under real cloudy conditions in Moscow about 600 MJ/m 2 . Thus, to cover the needs in the power supply of urban areas (for example, Moscow), it is required to utilize only about 1.5-2% of solar radiation. The rest of the radiation, if disposed of, will be redundant. At the same time, the issue of accumulation and preservation of daytime solar radiation for lighting in the evening and at night, when the loads on the power supply systems are maximum, and the sun almost or does not shine, remains to be solved. This will require the transmission of electricity over long distances between areas where the Sun is still high enough, and those where the Sun has already set below the horizon. At the same time, electricity losses in the networks will be comparable to its savings through the use of photovoltaic panels. Or it will require the use of high-capacity batteries, the production, installation and subsequent disposal of which will require energy costs that are unlikely to be covered by the energy savings accumulated over the entire period of their operation.

Another, no less important factor that makes doubtful the feasibility of switching to solar panels as an alternative source of electricity throughout the city is that, ultimately, the operation of photovoltaic cells will lead to a significant increase in solar radiation absorbed in the city, and, consequently, to an increase in air temperature in the city. city ​​in the summer. Thus, at the same time as cooling due to photopanels and air conditioners powered by them, there will be a general increase in air temperature in the city, which ultimately will nullify all economic and environmental benefits from saving electricity through the use of still very expensive photovoltaic panels. .

It follows that the installation of equipment for converting solar radiation into electricity justifies itself in a very limited list of cases: only in summer, only in climatic regions with dry, hot, cloudy weather, only in small towns or individual cottage settlements, and only if this electricity is used to operate installations for air conditioning and ventilation of the internal environment of buildings. In other cases - other areas, other urban conditions and at other times of the year - the use of photovoltaic panels and solar collectors for the needs of electricity and heat supply of ordinary buildings in medium and major cities located in temperate climates is inefficient.

Bioclimatic significance of solar radiation. The decisive role of the impact of solar radiation on living organisms is reduced to participation in the formation of their radiation and heat balances due to thermal energy in the visible and infrared parts of the solar spectrum.

Visible rays are of particular importance to organisms. Most animals, like humans, are good at distinguishing the spectral composition of light, and some insects can even see in the ultraviolet range. The presence of light vision and light orientation is an important survival factor. For example, a person has color vision- one of the most psycho-emotional and optimizing factors of life. Staying in the dark has the opposite effect.

As you know, green plants synthesize organic matter and, consequently, produce food for all other organisms, including humans. This most important process for life occurs during the assimilation of solar radiation, and plants use specific range spectrum in the wavelength range of 0.38-0.71 μm. This radiation is called photosynthetically active radiation(PAR) and is very important for plant productivity.

The visible part of the light creates natural light. In relation to it, all plants are divided into light-loving and shade-tolerant. Insufficient illumination causes weakness of the stem, weakens the formation of ears and cobs on plants, reduces the sugar content and the amount of oils in cultivated plants, makes it difficult for them to use mineral nutrition and fertilizers.

Biological action infrared rays consists of thermal effect when they are absorbed by the tissues of plants and animals. In this case, the kinetic energy of molecules changes, and electrical and chemical processes are accelerated. Due to infrared radiation, the lack of heat (especially in high-mountainous regions and at high latitudes) received by plants and animals from the surrounding space is compensated.

Ultraviolet radiation according to biological properties and effects on humans, it is customary to divide into three areas: area A - with wavelengths from 0.32 to 0.39 microns; region B, from 0.28 to 0.32 μm; and region C, from 0.01 to 0.28 μm. Area A is characterized by a relatively weakly expressed biological effect. It causes only the fluorescence of a number of organic substances, in humans it contributes to the formation of pigment in the skin and mild erythema (reddening of the skin).

The rays of area B are much more active. Diverse reactions of organisms to ultraviolet radiation, changes in the skin, blood, etc. mostly due to them. The well-known vitamin-forming effect of ultraviolet radiation is that ergosterone nutrients goes into vitamin O, which has a strong stimulating effect on growth and metabolism.

The most powerful biological action on living cells, rays of the C region have a bactericidal effect sunlight mainly due to them. AT small doses Ultraviolet rays are necessary for plants, animals and humans, especially children. However, in large quantities, the rays of region C are detrimental to all living things, and life on Earth is possible only because this short-wave radiation is almost completely blocked by the ozone layer of the atmosphere. Especially up-to-date solution The question of the impact of excess doses of ultraviolet radiation on the biosphere and humans has become in recent decades due to the depletion of the ozone layer of the Earth's atmosphere.

The effect of ultraviolet radiation (UVR), which reaches the earth's surface, on a living organism is very diverse. As mentioned above, in moderate doses, it has a beneficial effect: it increases vitality, enhances the body's resistance to infectious diseases. The lack of UVR leads to pathological phenomena, which are called UV deficiency or UV starvation and manifest themselves in a lack of vitamin E, which leads to a violation of phosphorus-calcium metabolism in the body.

Excess UVR can lead to very serious consequences: the formation of skin cancer, the development of other oncological formations, the appearance of photokeratitis (“snow blindness”), photoconjunctivitis and even cataracts; violation of the immune system of living organisms, as well as mutagenic processes in plants; change in the properties and destruction of polymeric materials widely used in construction and architecture. For example, UVR can discolor facade paints or lead to mechanical destruction of polymeric finishing and structural building products.

Architectural and construction significance of solar radiation. Solar energy data is used in calculating the heat balance of buildings and heating and air conditioning systems, in analyzing the aging processes of various materials, taking into account the effect of radiation on the thermal state of a person, choosing the optimal species composition of green spaces for planting greenery in a particular area, and many other purposes. Solar radiation determines the mode of natural illumination of the earth's surface, the knowledge of which is necessary when planning the consumption of electricity, designing various structures and organizing the operation of transport. Thus, the radiation regime is one of the leading urban planning and architectural and construction factors.

Insolation of buildings is one of the most important conditions for the hygiene of buildings, therefore, irradiation of surfaces with direct sunlight is given Special attention as an important environmental factor. At the same time, the Sun not only has a hygienic effect on the internal environment, killing pathogens, but also psychologically affects a person. The effect of such irradiation depends on the duration of the process of exposure to sunlight, so insolation is measured in hours, and its duration is normalized by the relevant documents of the Ministry of Health of Russia.

Required minimum solar radiation, providing comfortable conditions the internal environment of buildings, conditions for work and rest of a person, consists of the required illumination of living and working premises, the amount of ultraviolet radiation required for the human body, the amount of heat absorbed by external fences and transferred into buildings, providing thermal comfort of the internal environment. Based on these requirements, architectural and planning decisions are made, the orientation of living rooms, kitchens, utility and work rooms is determined. With an excess of solar radiation, the installation of loggias, blinds, shutters and other sun protection devices is provided.

It is recommended to analyze the sums of solar radiation (direct and diffuse) arriving at variously oriented surfaces (vertical and horizontal) according to the following scale:

• less than 50 kW h / m 2 per month - insignificant radiation;
• 50-100 kW h / m 2 per month - average radiation;
• 100-200 kW h / m 2 per month - high radiation;
• more than 200 kW h / m 2 per month - excess radiation.

With insignificant radiation, which is observed in temperate latitudes mainly in the winter months, its contribution to the heat balance of buildings is so small that it can be neglected. With average radiation in temperate latitudes, there is a transition to the region of negative values ​​​​of the radiation balance of the earth's surface and the buildings, structures, artificial coatings, etc. located on it. In this regard, they begin to lose more thermal energy in the daily course than they receive heat from the sun during the day. These losses in the heat balance of buildings are not covered by internal sources heat (electrical appliances, hot water pipes, metabolic heat release of people, etc.), and they must be compensated by the operation of heating systems - the heating period begins.

At high radiation and under real cloudy conditions, the thermal background of the urban area and the internal environment of buildings is in the comfort zone without the use of artificial heating and cooling systems.

With excess radiation in cities of temperate latitudes, especially those located in a temperate continental and sharply continental climate, overheating of buildings, their internal and external environments can be observed in summer. In this regard, architects are faced with the task of protecting the architectural environment from excessive insolation. They apply appropriate space-planning solutions, choose the optimal orientation of buildings on the sides of the horizon, architectural sun-protection elements of facades and light openings. If architectural means to protect against overheating are not enough, then there is a need for artificial conditioning of the internal environment of buildings.

The radiation regime also affects the choice of orientation and dimensions of light apertures. At low radiation, the size of the light apertures can be increased to any size, provided that heat losses through external fences are maintained at a level not exceeding the standard. In case of excessive radiation, light apertures are made minimal in size, ensuring the requirements for insolation and natural illumination of the premises.

The lightness of the facades, which determines their reflectivity (albedo), is also selected based on the requirements of sun protection or, conversely, taking into account the possibility of maximum absorption of solar radiation in areas with a cool and cold humid climate and with an average or low level of solar radiation in the summer months. To select facing materials based on their reflectivity, it is necessary to know how much solar radiation enters the walls of buildings of various orientations and what is the ability of various materials to absorb this radiation. Since the arrival of radiation to the wall depends on the latitude of the place and how the wall is oriented in relation to the sides of the horizon, the heating of the wall and the temperature inside the rooms adjacent to it will depend on this.

The absorbing capacity of various facade finishing materials depends on their color and condition (Table 1.10). If the monthly sums of solar radiation entering the walls of different orientations 1 and the albedo of these walls are known, then it is possible to determine the amount of heat absorbed by them.

Table 1.10

Absorption capacity of building materials

Data on the amount of incoming solar radiation (direct and diffuse) in a cloudless sky on vertical surfaces of various orientations are given in the Joint Venture "Construction Climatology".

Material name and processing	Characteristic surfaces	surfaces	Absorbed radiation,%
Concrete	Rough
		light blue
		Dark grey
		Bluish
	Hewn
		Yellowish brown
	polished
	Clean hewn	light gray
	Hewn
Roof
Ruberoid		brown
Galvanized steel		light gray
Roof tiles

Choosing the appropriate materials and colors for building envelopes, i.e. by changing the albedo of the walls, it is possible to change the amount of radiation absorbed by the wall and, thus, to reduce or increase the heating of the walls by solar heat. This technique is actively used in the traditional architecture of various countries. Everyone knows that southern cities are distinguished by a general light (white with colored decor) color of most residential buildings, while, for example, Scandinavian cities are mainly cities built of dark brick or using dark-colored tesa for cladding buildings.

It is calculated that 100 kWh/m 2 of absorbed radiation raises the temperature of the outer surface by about 4°C. The walls of buildings in most regions of Russia receive such an amount of radiation per hour on average if they are oriented to the south and east, as well as western, southwestern and southeastern ones if they are made of dark brick and not plastered or have dark-colored plaster.

To move from the average wall temperature for a month without taking into account radiation to the most commonly used characteristic in thermal engineering calculations - the outdoor air temperature, an additional temperature additive is introduced At, depending on the monthly amount of solar radiation absorbed by the wall VK(Fig. 1.15). Thus, knowing the intensity of the total solar radiation coming to the wall and the albedo of the surface of this wall, it is possible to calculate its temperature by introducing an appropriate correction to the air temperature.

VK, kWh/m2

Rice. 1.15. Increase in the temperature of the outer surface of the wall due to the absorption of solar radiation

In the general case, the temperature addition due to absorbed radiation is determined under otherwise equal conditions, i.e. at the same air temperature, humidity and thermal resistance of the building envelope, regardless of wind speed.

In clear weather at midday, the southern, before noon - southeastern and in the afternoon - southwestern walls can absorb up to 350-400 kWh / m 2 of solar heat and heat up so that their temperature can exceed 15-20 ° C outside air temperature. This creates large temperature con-

trusts between the walls of the same building. These contrasts in some areas turn out to be significant not only in summer, but also in the cold season with sunny low-wind weather, even at very low air temperatures. Metal structures are subjected to especially severe overheating. Thus, according to available observations, in Yakutia, located in a temperate sharply continental climate, characterized by cloudy weather in winter and summer, at midday hours with a clear sky, the aluminum parts of the enclosing structures and the roof of the Yakutskaya HPP heat up by 40-50 ° C above the air temperature, even at low values ​​of the latter.

Overheating of insolated walls due to the absorption of solar radiation must be provided for already at the stage of architectural design. This effect requires not only the protection of walls from excessive insolation by architectural methods, but also the appropriate planning solutions for buildings, the use of heating systems of various capacities for differently oriented facades, laying in the project of seams to relieve stress in structures and violation of the tightness of joints due to their temperature deformations. etc.

In table. 1.11, as an example, the monthly sums of absorbed solar radiation in June for several geographical objects of the former USSR are given for given albedo values. This table shows that if the albedo of the northern wall of the building is 30%, and the southern wall is 50%, then in Odessa, Tbilisi and Tashkent they will heat up in the same degree. If in northern regions reduce the albedo of the northern wall to 10%, then it will receive almost 1.5 times more heat than the wall with 30% albedo.

Table 1.11

Monthly sums of solar radiation absorbed by building walls in June at different values albedo (kW h / m 2)

The above examples, based on data on total (direct and diffuse) solar radiation contained in the Joint Venture "Construction Climatology" and climate reference books, do not take into account the solar radiation reflected from the earth's surface and surrounding objects (for example, existing buildings) arriving at various building walls. It depends less on their orientation, therefore, it is not given in the regulatory documents for construction. However, this reflected radiation can be quite intense and comparable in power to direct or diffuse radiation. Therefore, in architectural design, it must be taken into account, calculating for each specific case.

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The most important source from which the surface of the Earth and the atmosphere receive thermal energy is the Sun. It sends a colossal amount of radiant energy into the world 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 hit the Earth's surface parallel to each other, but since the Earth has a spherical shape, 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 totality of radiant energy sent by the Sun is called solar radiation, it is usually expressed in calories per surface area per year.

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

It should be noted that the total amount of 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 in a cloudless sky is called straight. She carries the largest number warmth and light. If our planet had no atmosphere, the earth's surface would receive only direct radiation.

However, passing through the atmosphere, about a quarter of the solar radiation is scattered by gas molecules and impurities, deviates from the direct path. Some of them reach the Earth's surface, forming scattered solar radiation. Thanks to scattered radiation, light also 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 rays of the sun that hit the earth are total solar radiation i.e., the totality of direct and diffuse radiation (Fig. 1).

Rice. 1. Total solar radiation per year

Distribution of solar radiation over the earth's surface

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

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

2. from geographical latitude terrain - 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 fall on the Earth the shortest way and intensively give their energy to a small area. On Earth, this occurs in the band between 23° N. sh. and 23°S sh., i.e. between the tropics. As you move away from this zone to the south or north, the length of the path of the sun's rays increases, i.e., 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 gliding, 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 you move towards the poles, this amount is sharply reduced. In addition, the length of the day at different times of the year also depends on the latitude of the area, 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 a change in the noon altitude of the Sun and the length of the day;

4. on the nature of the earth's surface - the brighter the surface, the more sunlight it reflects. The ability of a surface to reflect radiation is called albedo(from lat. whiteness). Snow reflects radiation especially strongly (90%), sand is weaker (35%), chernozem is 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 delay 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 earth's surface is called radiation balance. The radiation balance of the earth's surface varies during the day and seasons of the year, but on average for the year it has a positive value everywhere, with the exception of the icy deserts of Greenland and Antarctica. 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 caused by them is relatively small. The sun heats the earth's surface, 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 the heat reflected from the earth's surface to freely escape into space. They create the greenhouse effect, due to which the temperature drop 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 down by 40-50 °C overnight.

As a result of the growth in the scale of human economic activity - the burning of coal and oil at thermal power plants, emissions industrial enterprises, an increase in car emissions - the content of carbon dioxide in the atmosphere is increasing, which leads to an increase in the greenhouse effect and threatens global climate change.

The sun's rays, having passed through the atmosphere, fall on the surface of the Earth and heat it, and that, in turn, gives off heat to the atmosphere. This explains the characteristic feature of the troposphere: a decrease in air temperature with height. But there are times when the upper layers of the atmosphere are warmer than the lower ones. Such a phenomenon is called temperature inversion(from lat. inversio - turning over).

The Earth receives from the Sun 1.36 * 10v24 cal of heat per year. Compared to this amount of energy, the remaining amount of radiant energy reaching the Earth's surface is negligible. Thus, the radiant energy of the stars is one hundred millionth of the solar energy, cosmic radiation- two billionths, the internal heat of the Earth at its surface is equal to one five thousandth of the solar heat.
Radiation of the Sun - solar radiation- is the main source of energy for almost all processes occurring in the atmosphere, hydrosphere and in the upper layers of the lithosphere.
The unit of measurement of the intensity of solar radiation is the number of calories of heat absorbed by 1 cm2 of an absolutely black surface perpendicular to the direction of the sun's rays in 1 minute (cal/cm2*min).

The flow of radiant energy from the Sun, reaching the earth's atmosphere, is very constant. Its intensity is called the solar constant (Io) and is taken on average to be 1.88 kcal/cm2 min.
The value of the solar constant fluctuates depending on the distance of the Earth from the Sun and on solar activity. Its fluctuations during the year are 3.4-3.5%.
If the sun's rays everywhere fell vertically on the earth's surface, then in the absence of an atmosphere and at a solar constant of 1.88 cal/cm2*min, each square centimeter it would receive 1000 kcal per year. Due to the fact that the Earth is spherical, this amount is reduced by 4 times, and 1 sq. cm receives an average of 250 kcal per year.
The amount of solar radiation received by the surface depends on the angle of incidence of the rays.
The maximum amount of radiation is received by the surface perpendicular to the direction of the sun's rays, because in this case all the energy is distributed to the area with a cross section equal to the cross section of the beam of rays - a. With oblique incidence of the same beam of rays, the energy is distributed over a large area (section c) and a unit surface receives a smaller amount of it. The smaller the angle of incidence of the rays, the lower the intensity of solar radiation.
The dependence of the intensity of solar radiation on the angle of incidence of rays is expressed by the formula:

I1 = I0 * sinh,

where I0 is the intensity of solar radiation at a sheer incidence of rays. Outside the atmosphere, the solar constant;
I1 - the intensity of solar radiation when the sun's rays fall at an angle h.
I1 is as many times less than I0, how many times the section a is less than the section b.
Figure 27 shows that a / b \u003d sin A.
The angle of incidence of the sun's rays (the height of the Sun) is equal to 90 ° only at latitudes from 23 ° 27 "N to 23 ° 27" S. (i.e. between the tropics). At other latitudes, it is always less than 90° (Table 8). According to the decrease in the angle of incidence of rays, the intensity of solar radiation arriving at the surface at different latitudes should also decrease. Since the height of the Sun does not remain constant throughout the year and during the day, the amount of solar heat received by the surface changes continuously.

The amount of solar radiation received by the surface is directly related to from the duration of its exposure to sunlight.

In the equatorial zone outside the atmosphere, the amount of solar heat during the year does not experience big fluctuations, whereas at high latitudes these fluctuations are very large (see Table 9). In winter, the differences in the arrival of solar heat between high and low latitudes are especially significant. In summer, under conditions of continuous illumination, the polar regions receive the maximum amount of solar heat per day on Earth. On the day of the summer solstice in the northern hemisphere, it is 36% higher than the daily amount of heat at the equator. But since the duration of the day at the equator is not 24 hours (as at this time at the pole), but 12 hours, the amount of solar radiation per unit of time at the equator remains the largest. The summer maximum of the daily sum of solar heat, observed at about 40-50° latitude, is associated with a relatively long day (greater than at this time by 10-20° latitude) at a significant height of the Sun. Differences in the amount of heat received by the equatorial and polar regions are smaller in summer than in winter.
The southern hemisphere receives more heat in summer than the northern one, and vice versa in winter (it is affected by the change in the distance of the Earth from the Sun). And if the surface of both hemispheres were completely homogeneous, the annual amplitudes of temperature fluctuations in the southern hemisphere would be greater than in the northern.
Solar radiation in the atmosphere undergoes quantitative and qualitative changes.
Even an ideal, dry and clean atmosphere absorbs and scatters rays, reducing the intensity of solar radiation. The weakening effect of the real atmosphere, containing water vapor and solid impurities, on solar radiation is much greater than the ideal one. The atmosphere (oxygen, ozone, carbon dioxide, dust and water vapor) absorbs mainly ultraviolet and infrared rays. The radiant energy of the Sun absorbed by the atmosphere is converted into other types of energy: thermal, chemical, etc. In general, absorption weakens solar radiation by 17-25%.
Molecules of atmospheric gases scatter rays with relatively short waves - violet, blue. This is what explains the blue color of the sky. Impurities equally scatter rays with waves various lengths. Therefore, with a significant content of them, the sky acquires a whitish tint.
Due to the scattering and reflection of the sun's rays by the atmosphere, daylight is observed on cloudy days, objects in the shade are visible, and the phenomenon of twilight occurs.
The longer the path of the beam in the atmosphere, the greater its thickness it must pass and the more significantly the solar radiation is attenuated. Therefore, with elevation, the influence of the atmosphere on radiation decreases. The length of the path of sunlight in the atmosphere depends on the height of the Sun. If we take as a unit the length of the path of the solar beam in the atmosphere at the height of the Sun 90 ° (m), the ratio between the height of the Sun and the path length of the beam in the atmosphere will be as shown in Table. ten.

The total attenuation of radiation in the atmosphere at any height of the Sun can be expressed by the Bouguer formula: Im = I0 * pm, where Im is the intensity of solar radiation near the earth's surface changed in the atmosphere; I0 - solar constant; m is the path of the beam in the atmosphere; at a solar height of 90 ° it is equal to 1 (the mass of the atmosphere), p is the transparency coefficient (a fractional number showing what fraction of radiation reaches the surface at m = 1).
At a height of the Sun of 90°, at m=1, the intensity of solar radiation near the earth's surface I1 is p times less than Io, i.e. I1=Io*p.
If the height of the Sun is less than 90°, then m is always greater than 1. The path of a solar ray can consist of several segments, each of which is equal to 1. The intensity of solar radiation at the border between the first (aa1) and second (a1a2) segments I1 is obviously equal to Io *p, radiation intensity after passing the second segment I2=I1*p=I0 p*p=I0 p2; I3=I0p3 etc.

The transparency of the atmosphere is not constant and is not the same in various conditions. The ratio of the transparency of the real atmosphere to the transparency of the ideal atmosphere - the turbidity factor - is always greater than one. It depends on the content of water vapor and dust in the air. With an increase in geographical latitude, the turbidity factor decreases: at latitudes from 0 to 20 ° N. sh. it is equal to 4.6 on average, at latitudes from 40 to 50 ° N. sh. - 3.5, at latitudes from 50 to 60 ° N. sh. - 2.8 and at latitudes from 60 to 80 ° N. sh. - 2.0. In temperate latitudes, the turbidity factor is less in winter than in summer, and less in the morning than in the afternoon. It decreases with height. The greater the turbidity factor, the greater the attenuation of solar radiation.
Distinguish direct, diffuse and total solar radiation.
Part of the solar radiation that penetrates through the atmosphere to the earth's surface is direct radiation. Part of the radiation scattered by the atmosphere is converted into diffuse radiation. All solar radiation entering the earth's surface, direct and diffuse, is called total radiation.
The ratio between direct and scattered radiation varies considerably depending on the cloudiness, dustiness of the atmosphere, and also on the height of the Sun. In clear skies, the fraction of scattered radiation does not exceed 0.1%; in cloudy skies, diffuse radiation can be greater than direct radiation.
At a low altitude of the Sun, the total radiation consists almost entirely of scattered radiation. At a solar altitude of 50° and a clear sky, the fraction of scattered radiation does not exceed 10-20%.
Maps of average annual and monthly values ​​of total radiation make it possible to notice the main patterns in its geographical distribution. The annual values ​​of total radiation are distributed mainly zonal. The largest annual amount of total radiation on Earth is received by the surface in tropical inland deserts (Eastern Sahara and the central part of Arabia). A noticeable decrease in total radiation at the equator is caused by high air humidity and high cloudiness. In the Arctic, the total radiation is 60-70 kcal/cm2 per year; in the Antarctic, due to the frequent recurrence of clear days and the greater transparency of the atmosphere, it is somewhat greater.

In June, the northern hemisphere receives the largest amounts of radiation, and especially the inland tropical and subtropical regions. The amounts of solar radiation received by the surface in the temperate and polar latitudes of the northern hemisphere differ little, owing mainly to the long duration of the day in the polar regions. Zoning in the distribution of total radiation above. continents in the northern hemisphere and in the tropical latitudes of the southern hemisphere is almost not expressed. It is better manifested in the northern hemisphere over the Ocean and is clearly expressed in the extratropical latitudes of the southern hemisphere. South polar circle the value of total solar radiation approaches 0.
In December, the largest amounts of radiation enter the southern hemisphere. The high-lying ice surface of Antarctica, with high air transparency, receives significantly more total radiation than the surface of the Arctic in June. There is a lot of heat in the deserts (Kalahari, Great Australian), but due to the greater oceanicity of the southern hemisphere (the influence of high air humidity and cloudiness), its amounts here are somewhat less than in June at the same latitudes of the northern hemisphere. In the equatorial and tropical latitudes of the northern hemisphere, the total radiation varies relatively little, and the zoning in its distribution is clearly expressed only to the north of the northern tropic. With increasing latitude, the total radiation decreases rather rapidly; its zero isoline passes somewhat north of the Arctic Circle.
The total solar radiation, falling on the Earth's surface, is partially reflected back into the atmosphere. The ratio of the amount of radiation reflected from a surface to the amount of radiation incident on that surface is called albedo. Albedo characterizes the reflectivity of a surface.
The albedo of the earth's surface depends on its condition and properties: color, humidity, roughness, etc. Freshly fallen snow has the highest reflectivity (85-95%). Calm water surface when the sun's rays fall on it vertically, it reflects only 2-5%, and when the sun is low, almost all the rays falling on it (90%). Albedo of dry chernozem - 14%, wet - 8, forest - 10-20, meadow vegetation - 18-30, sandy desert surfaces - 29-35, surfaces sea ​​ice - 30-40%.
The large albedo of the ice surface, especially covered with fresh snow (up to 95%), is the reason low temperatures in the polar regions in the summer, when the arrival of solar radiation is significant there.
Radiation of the earth's surface and atmosphere. Any body with a temperature above absolute zero (greater than minus 273°) emits radiant energy. The total emissivity of a blackbody is proportional to the fourth power of its absolute temperature (T):
E \u003d σ * T4 kcal / cm2 per minute (Stefan-Boltzmann law), where σ is a constant coefficient.
The higher the temperature of the radiating body, the shorter the wavelength of the emitted nm rays. The incandescent Sun sends into space shortwave radiation. The earth's surface, absorbing short-wave solar radiation, heats up and also becomes a source of radiation (terrestrial radiation). Ho, since the temperature of the earth's surface does not exceed several tens of degrees, its long-wave radiation, invisible.
Terrestrial radiation is largely retained by the atmosphere (water vapor, carbon dioxide, ozone), but rays with a wavelength of 9-12 microns freely go beyond the atmosphere, and therefore the Earth loses some of its heat.
The atmosphere, absorbing part of the solar radiation passing through it and more than half of the earth's, itself radiates energy both into the world space and to the earth's surface. Atmospheric radiation directed towards the earth's surface towards the earth's surface is called opposite radiation. This radiation, like the terrestrial, long-wave, invisible.
Two streams of long-wave radiation meet in the atmosphere - the radiation of the Earth's surface and the radiation of the atmosphere. The difference between them, which determines the actual loss of heat by the earth's surface, is called efficient radiation. Effective radiation is the greater, the higher the temperature of the radiating surface. Air humidity reduces the effective radiation, its clouds greatly reduce it.
The highest value of the annual sums of effective radiation is observed in tropical deserts - 80 kcal / cm2 per year - due to the high surface temperature, dry air and clear sky. At the equator, with high air humidity, the effective radiation is only about 30 kcal/cm2 per year, and its value for land and for the ocean differs very little. The lowest effective radiation in the polar regions. In temperate latitudes, the earth's surface loses about half of the amount of heat that it receives from the absorption of total radiation.
The ability of the atmosphere to pass the short-wave radiation of the Sun (direct and diffuse radiation) and delay the long-wave radiation of the Earth is called the greenhouse (greenhouse) effect. Due to the greenhouse effect, the average temperature of the earth's surface is +16°, in the absence of an atmosphere it would be -22° (38° lower).
Radiation balance (residual radiation). The earth's surface simultaneously receives radiation and gives it away. The arrival of radiation is the total solar radiation and the counter radiation of the atmosphere. Consumption - the reflection of sunlight from the surface (albedo) and the own radiation of the earth's surface. The difference between the incoming and outgoing radiation is radiation balance, or residual radiation. The value of the radiation balance is determined by the equation

R \u003d Q * (1-α) - I,

where Q is the total solar radiation per unit surface; α - albedo (fraction); I - effective radiation.
If the input is greater than the output, the radiation balance is positive; if the input is less than the output, the balance is negative. At night, at all latitudes, the radiation balance is negative; during the day, until noon, it is positive everywhere, except for high latitudes in winter; in the afternoon - again negative. On average per day, the radiation balance can be both positive and negative (Table 11).


On the map of the annual sums of the radiation balance of the earth's surface, one can see abrupt change positions of isolines during their transition from land to the ocean. As a rule, the radiation balance of the Ocean surface exceeds the radiation balance of the land (the effect of albedo and effective radiation). The distribution of the radiation balance is generally zonal. On the Ocean in tropical latitudes, the annual values ​​of the radiation balance reach 140 kcal/cm2 (Arabian Sea) and do not exceed 30 kcal/cm2 at the boundary of floating ice. Deviations from the zonal distribution of the radiation balance in the Ocean are insignificant and are caused by the distribution of clouds.
On land in the equatorial and tropical latitudes, the annual values ​​of the radiation balance vary from 60 to 90 kcal/cm2, depending on the moisture conditions. The largest annual sums of the radiation balance are noted in those regions where the albedo and effective radiation are relatively small (humid rainforests, savannas). Their lowest value is in very humid (large cloudiness) and in very dry (large effective radiation) regions. In temperate and high latitudes, the annual value of the radiation balance decreases with increasing latitude (the effect of a decrease in total radiation).
The annual sums of the radiation balance over the central regions of Antarctica are negative (several calories per 1 cm2). In the Arctic, these values ​​are close to zero.
In July, the radiation balance of the earth's surface in a significant part of the southern hemisphere is negative. The zero balance line runs between 40 and 50°S. sh. The highest value of the radiation balance is reached on the surface of the Ocean in the tropical latitudes of the northern hemisphere and on the surface of some inland seas, for example Black (14-16 kcal / cm2 per month).
In January, the zero balance line is located between 40 and 50°N. sh. (over the oceans it rises somewhat to the north, over the continents it descends to the south). A significant part of the northern hemisphere has a negative radiation balance. The largest values ​​of the radiation balance are confined to the tropical latitudes of the southern hemisphere.
On average for the year, the radiation balance of the earth's surface is positive. In this case, the surface temperature does not rise, but remains approximately constant, which can only be explained by the continuous consumption of excess heat.
The radiation balance of the atmosphere consists of the solar and terrestrial radiation absorbed by it, on the one hand, and atmospheric radiation, on the other. It is always negative, since the atmosphere absorbs only a small part of solar radiation, and radiates almost as much as the surface.
The radiation balance of the surface and the atmosphere together, as a whole, for the entire Earth for a year is equal to zero on average, but in latitudes it can be both positive and negative.
The consequence of such a distribution of the radiation balance should be the transfer of heat in the direction from the equator to the poles.
Thermal balance. The radiation balance is the most important component of the heat balance. The surface heat balance equation shows how the incoming solar radiation energy is converted on the earth's surface:

where R is the radiation balance; LE - heat consumption for evaporation (L - latent heat of vaporization, E - evaporation);
P - turbulent heat exchange between the surface and the atmosphere;
A - heat exchange between the surface and underlying layers of soil or water.
The radiation balance of a surface is considered positive if the radiation absorbed by the surface exceeds the heat loss, and negative if it does not replenish them. All other terms of the heat balance are considered positive if they cause heat loss by the surface (if they correspond to heat consumption). As. all terms of the equation can change, the heat balance is constantly disturbed and restored again.
The equation of the surface heat balance considered above is approximate, since it does not take into account some secondary, but under specific conditions, acquiring importance factors, such as the release of heat during freezing, its consumption for thawing, etc.
The heat balance of the atmosphere consists of the radiation balance of the atmosphere Ra, the heat coming from the surface, Pa, the heat released in the atmosphere during condensation, LE, and the horizontal heat transfer (advection) Aa. The radiation balance of the atmosphere is always negative. The influx of heat as a result of moisture condensation and the magnitude of turbulent heat transfer are positive. Heat advection leads, on average per year, to its transfer from low latitudes to high latitudes: thus, it means heat consumption at low latitudes and arrival at high latitudes. In a multi-year derivation, the heat balance of the atmosphere can be expressed by the equation Ra=Pa+LE.
The heat balance of the surface and the atmosphere together as a whole is equal to 0 on a long-term average (Fig. 35).

The amount of solar radiation entering the atmosphere per year (250 kcal/cm2) is taken as 100%. Solar radiation, penetrating into the atmosphere, is partially reflected from the clouds and goes back beyond the atmosphere - 38%, partially absorbed by the atmosphere - 14%, and partially in the form of direct solar radiation reaches the earth's surface - 48%. Of the 48% that reach the surface, 44% are absorbed by it, and 4% are reflected. Thus, the Earth's albedo is 42% (38+4).
The radiation absorbed by the earth's surface is spent as follows: 20% is lost through effective radiation, 18% is spent on evaporation from the surface, 6% is spent on heating the air during turbulent heat transfer (total 24%). The loss of heat by the surface balances its arrival. The heat received by the atmosphere (14% directly from the Sun, 24% from the earth's surface), together with the effective radiation of the Earth, is directed to the world space. The Earth's albedo (42%) and radiation (58%) balance the influx of solar radiation to the atmosphere.