The number of straight lines coming to the earth's surface solar radiation(S) under cloudless conditions depends on the height of the sun and transparency. The table for three latitudinal zones shows the distribution of monthly totals of direct radiation with a cloudless sky (possible sums) in the form of averaged values for the central months of the seasons and the year.
The increased arrival of direct radiation in the Asian part is due to the higher transparency of the atmosphere in this region. The high values of direct radiation in the summer in the northern regions of Russia are explained by a combination of high transparency of the atmosphere and a long day
Reduces the arrival of direct radiation and can significantly change its daily and annual course. However, under average cloudy conditions, the astronomical factor is predominant and, consequently, the maximum direct radiation is observed at the highest altitude of the sun.
In most of the continental regions of Russia in the spring-summer months, direct radiation in the pre-noon hours is greater than in the afternoon. This is due to the development of convective cloudiness in the afternoon hours and a decrease in the transparency of the atmosphere at this time of the day compared to the morning hours. In winter, the ratio of pre- and afternoon radiation values is reversed - the pre-noon values of direct radiation are less due to the morning maximum cloudiness and its decrease in the second half of the day. The difference between pre- and afternoon values of direct radiation can reach 25–35%.
In the annual course, the maximum direct radiation falls on June-July, with the exception of areas Far East, where it shifts to May, and in the south of Primorye a secondary maximum is noted in September.
The maximum monthly amount of direct radiation on the territory of Russia is 45–65% of what is possible under a cloudless sky, and even in the south of the European part it reaches only 70%. Minimum values celebrated in December and January.
The contribution of direct radiation to the total arrival under actual cloudiness reaches a maximum in the summer months and averages 50–60%. The exception is Primorsky Krai, where the largest contribution of direct radiation falls on the autumn and winter months.
The distribution of direct radiation under average (actual) cloudiness over the territory of Russia largely depends on . This leads to a noticeable violation of the zonal distribution of radiation in certain months. This is especially evident in the spring. So, in April there are two maximums - one in the southern regions
Solar radiation is the radiation inherent in the luminary of our planetary system. The Sun is the 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 that is one of the main factors that make possible life 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 thought more than once about what the Sun is, why it is so important for all forms of life on our planet, why the movement of this luminary is exactly the way we see it.
The progress of technology has made it possible to better understand what the Sun is, what processes 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 voluminous 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 effect on different forms organic life on earth.
About terms
The most important step in mastering the essence of the concept was made in the last century. It was then that the eminent astronomer A. Eddington formulated an assumption: thermonuclear fusion occurs in the solar depths, which makes it possible to stand out a huge number energy radiated 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 found that helium nuclei are inferior in mass to the total value of 4 protons required to form a 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 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:
- warm;
- 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 limited area surfaces.
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 considered to be the angle of incidence depending on latitude ( geographical feature terrain on the globe), a season that determines how far a particular point is from a radiation source. 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 managed to reveal, the energy of solar radiation has a serious impact on the 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 transmitting thermal energy 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 perception infrared radiation Numerous devices are in operation, 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 circulatory system, as well as 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. Most modern drugs help to cope with colloid 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 of 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 human ability 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 appeared, theories, the adherents of which believe that color can affect physical state human, 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, are mainly scattered in the atmospheric layers, and only a small percentage reaches the earth's surface. The shorter the wavelength, the deeper such radiation can penetrate human (and not only) skin.
On the one hand, ultraviolet radiation is dangerous, but without it, the existence of diverse organic life is impossible. Such radiation is responsible for the formation of calciferol in the body, and this element is necessary for the construction of bone tissue. 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. Excessive exposure to direct sunlight, especially in conditions increased activity shining, harmful and dangerous. Long-term effects on the body, as well as too high radiation activity, cause:
- burns, redness;
- edema;
- hyperemia;
- heat;
- nausea;
- vomiting.
Prolonged ultraviolet irradiation provokes a violation of appetite, the functioning of the central nervous system, 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 initiates the production of melanin, a hormone that helps the skin protect itself from the negative effects of waves. Under the influence of this substance, the skin becomes darker, and the shade turns 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;
- spend no more than an hour under the direct rays of the sun;
- 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 human body exceptionally large, one should not lose sight of both positive and negative aspects. It should be realized that different people biochemical reactions take place individual features, so for someone and half-hour sunbathing can be dangerous. It is reasonable to consult a doctor before the beach season, assess the type, condition skin. This will help prevent harm to health.
If possible, sunburn should be avoided in old age, during the period of bearing a baby. Cancer diseases, mental disorders are not combined with sunbathing, skin pathologies and failure 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 height of the position celestial body, the type of land surface in this area, as well as the level of air transparency. The more aerosol particles scattered in the atmosphere, the lower the direct radiation, but the proportion of scattered radiation increases. Normally, in the absence of cloudiness in the total radiation, diffuse is one fourth.
Our country belongs to the northern ones, therefore most years 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 interval May-July is a unique period when even in the north total radiation quite impressive, since the sun is high in the sky, and the duration of daylight hours is longer than in other months of the year. 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. Max Strength wave radiation is observed at noon, and the annual maximum occurs in June, when the sun is highest in the sky.
Total solar radiation is the amount of solar energy reaching our planet. 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. Flights into space, especially in conditions of unpredictable solar activity , may be accompanied by significant exposure of astronauts, which obliges to take additional measures protection 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 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, going to new mission, can get into powerful streams of radiation. This makes it even more important question both research and forecasting of radiation features, and development of methods of protection against it.
Radiation coming to the upper boundary of the atmosphere and then to the earth's surface directly from the Sun (from the solar disk) in the form of a beam of parallel rays is called direct solar radiation. Direct solar radiation entering the upper boundary of the atmosphere changes over time within small limits, so it is called the solar constant (Sq). With an average distance from the Earth to the Sun of 149.5 * 106 km, Sq is about 1400 W/m2.
When the flow of direct solar radiation passes through the atmosphere, it weakens due to absorption (about 15%) and scattering (about 25%) of energy by gases, aerosols, clouds.
According to Bouguer's law of attenuation, direct solar radiation entering the Earth's surface during a vertical (perpendicular) incidence of rays,
where p is the transparency coefficient of the atmosphere; m is the number of optical masses of the atmosphere.
The weakening of the solar flux in the atmosphere depends on the height of the Sun above the Earth's horizon and the transparency of the atmosphere. The lower its height above the horizon, the more optical masses of the atmosphere passes the sunbeam. One optical mass of the atmosphere is taken as the mass that the rays pass when the Sun is at its zenith (Fig. 2.1). When the Sun is at the horizon, the beam travels in the atmosphere a path that is almost 35 times greater than when the rays fall at an angle of 90 ° to the Earth's surface. The number of optical masses of the atmosphere (m) at different heights of the Sun (Lf) is given below.
t 1.0 1.0 1.1 1.2 1.3 1.6 2.0 2.9 5.6 10.4 26.0 34.4 L0 90 80 70 60 50 40 30 20 10 5 1 0
The longer the path of the sun's rays in the atmosphere, the stronger their absorption and scattering, and the more their intensity changes.
The transparency coefficient depends on the content of water vapor and aerosols in the atmosphere: the more of them, the lower the transparency coefficient at the same number passable optical masses. On average, for the entire radiation flux in an ideally clean atmosphere, p at sea level is about 0.9, in actual atmospheric conditions it is 0.70 ... 0.85, in winter it is slightly higher than in summer. The arrival of direct radiation on the earth's surface depends on the angle of incidence of the sun's rays. The flow of direct solar radiation falling on a horizontal surface is called insolation.
S" \u003d Ssin A. If the earth's surface is not horizontal, as is mostly the case in nature, then the arrival of radiation on it depends not only on the height of the Sun, but also on the slope of the surface, and on its orientation with respect to the cardinal points ( from exposure).
At meteorological stations, thermometers are installed in a special booth called a psychrometric booth, the walls of which are louvered. The rays of the Sun do not penetrate into such a booth, but at the same time the air has Free access into her.
Thermometers are mounted on a tripod so that the tanks are located at a height of 2 m from the active surface.
Urgent air temperature is measured with a mercury psychrometric thermometer TM-4, which is installed vertically. At temperatures below -35 ° C, a low-degree alcohol thermometer TM-9 is used.
Extreme temperatures are measured by maximum TM-1 and minimum TM-2 thermometers, which are laid horizontally.
For continuous recording of air temperature, an M-16A thermograph is used, which is placed in a louvered box for recorders. Temperature fluctuations are perceived by a curved bimetallic plate. Depending on the speed of rotation of the drum, thermographs are daily and weekly.
In crops and plantations, the air temperature is measured without disturbing the vegetation cover. For this, remote electrical resistance thermometers with a small-sized receiving part are used.
Interior view of the psychrometric booth:
1 - hygrometer; 2 - dry and wet thermometers; 3 - maximum and minimum thermometers
Thermograph M-16A:
1 - drum with tape; 2-- arrow with a pen; 3 - bimetallic plate
The sun is the source of corpuscular and electromagnetic radiation. Corpuscular radiation does not penetrate the atmosphere below 90 km, while electromagnetic radiation reaches the earth's surface. In meteorology it is called solar radiation or simply radiation. It is one two-billionth of the total energy of the Sun and travels from the Sun to the Earth in 8.3 minutes. Solar radiation is the source of energy for almost all processes occurring in the atmosphere and on the earth's surface. It is mainly shortwave and consists of invisible ultraviolet radiation - 9%, visible light - 47% and invisible infrared - 44%. Since almost half of the solar radiation is visible light, the Sun is a source of not only heat, but also light - too. necessary condition for life on earth.
Radiation coming to Earth directly from the solar disk is called direct solar radiation. Due to the fact that the distance from the Sun to the Earth is large, and the Earth is small, radiation falls on any of its surfaces in the form of a beam of parallel rays.
Solar radiation has a certain flux density per unit area per unit time. The unit of measurement of radiation intensity is the amount of energy (in joules or calories 1) that 1 cm 2 of the surface per minute receives when the sun's rays fall perpendicularly. At the upper boundary of the atmosphere, at an average distance from the Earth to the Sun, it is 8.3 J / cm 2 per minute, or 1.98 cal / cm 2 per minute. This value is accepted as an international standard and is called solar constant(S0). Its periodic fluctuations during the year are insignificant (+ 3.3%) and are due to a change in the distance from the Earth to
1 1 cal = 4.19 J, 1 kcal = 41.9 MJ.
2 The noon altitude of the Sun depends on the geographic latitude and declination of the Sun.
Sun. Non-periodic fluctuations are caused by different emissivity of the Sun. The climate at the top of the atmosphere is called radiation or solar. It is calculated theoretically, based on the angle of inclination of the sun's rays on a horizontal surface.
AT in general terms the solar climate is reflected on the earth's surface. At the same time, the real radiation and temperature on Earth differ significantly from the solar climate due to various terrestrial factors. The main one is the attenuation of radiation in the atmosphere due to reflections, absorptions and scattering, and also as a result reflections of radiation from the earth's surface.
At the top of the atmosphere, all radiation comes in the form of direct radiation. According to S. P. Khromov and M. A. Petrosyants, 21% of it is reflected from clouds and air back into outer space. The rest of the radiation enters the atmosphere, where direct radiation is partially absorbed and scattered. Remaining direct radiation(24%) reaches the earth's surface, however, it is weakened. The patterns of its weakening in the atmosphere are expressed by Bouguer's law: S=S 0 pm(J, or cal / cm 2, per min), where S is the amount of direct solar radiation that has reached the earth's surface, per unit area (cm 2) located perpendicular to the sun's rays, S 0 is the solar constant, R- coefficient of transparency in fractions of unity, showing what part of the radiation reached the earth's surface, t is the path length of the beam in the atmosphere.
In reality, the sun's rays fall on the earth's surface and on any other level of the atmosphere at an angle of less than 90°. The flow of direct solar radiation onto a horizontal surface is called insolation(5,). It is calculated by the formula S 1 \u003d S sin h ☼ (J, or cal / cm 2, per minute), where h ☼ is the height of the Sun 2. Naturally, there is a smaller amount per unit of horizontal surface
energy than per unit area located perpendicular to the sun's rays (Fig. 22).
In the atmosphere absorbed about 23% and dissipates about 32% of the direct solar radiation entering the atmosphere, with 26% of the scattered radiation then coming to the earth's surface, and 6% going into space.
Solar radiation undergoes not only quantitative but also qualitative changes in the atmosphere, since air gases and aerosols absorb and scatter solar rays selectively. The main absorbers of radiation are water vapor, clouds and aerosols, as well as ozone, which strongly absorbs ultraviolet radiation. Molecules of various gases and aerosols participate in the scattering of radiation. Scattering- deflection of light rays in all directions from the original direction, so that scattered radiation comes to the earth's surface not from the solar disk, but from the entire firmament. Scattering depends on the wavelength: according to Rayleigh's law, the shorter the wavelength, the more intense the scattering. Therefore, ultraviolet rays are scattered most of all, and of the visible ones, violet and blue. Hence the blue color of the air and, accordingly, the sky in clear weather. Direct radiation, on the other hand, turns out to be mostly yellow, so the solar disk appears yellowish. At sunrise and sunset, when the path of the beam in the atmosphere is longer and the scattering is greater, only red rays reach the surface, which makes the Sun appear red. Scattered radiation causes light in the daytime in cloudy weather and in the shade in clear weather; the phenomenon of twilight and white nights is associated with it. On the Moon, where there is no atmosphere and, accordingly, scattered radiation, objects that fall into the shadow become completely invisible.
With height, as the density of air decreases and, accordingly, the number of scattering particles, the color of the sky becomes darker, first turning into deep blue, then into blue-violet, which is clearly visible in the mountains and reflected in the Himalayan landscapes of N. Roerich. In the stratosphere, the color of the air is black and purple. Astronauts testify that at an altitude of 300 km the color of the sky is black.
In the presence of large aerosols, droplets and crystals in the atmosphere, it is no longer scattering, but diffuse reflection, and since the diffusely reflected radiation is white light, the color of the sky becomes whitish.
Direct and diffuse solar radiation have a certain daily and annual course, which depends primarily on the height of the Sun.
Rice. 22. The influx of solar radiation on the surface AB, perpendicular to the rays, and on the horizontal surface AC (according to S. P. Khromov)
above the horizon, from the transparency of the air and cloudiness.
The flux of direct radiation in during the day increases from sunrise to noon and then decreases until sunset due to a change in the height of the Sun and the path of the beam in the atmosphere. However, since the transparency of the atmosphere decreases around noon due to an increase in water vapor in the air and dust, and convective cloudiness increases, the maximum values of radiation are shifted to pre-noon hours. This pattern is inherent in equatorial-tropical latitudes all year round, and in temperate latitudes in summer. In winter, in temperate latitudes, the maximum radiation occurs at noon.
annual course Monthly average direct radiation values depend on latitude. At the equator, the annual course of direct radiation has the form of a double wave: maxima during the periods of spring and autumn equinox, minimums during the summer and winter solstices. In temperate latitudes, the maximum values of direct radiation occur in the spring (April in the northern hemisphere), and not in the summer months, since the air at this time is more transparent due to the lower content of water vapor and dust, as well as slight cloudiness. The radiation minimum is observed in December, when the sun is at its lowest, daylight hours are short, and it is the most cloudy month of the year.
Daily and annual course of scattered radiation is determined by the change in the height of the Sun above the horizon and the length of the day, as well as the transparency of the atmosphere. The maximum of scattered radiation during the day is observed during the day with an increase in radiation as a whole, although its share in the morning and evening hours is greater than direct radiation, and during the day, on the contrary, direct radiation prevails over diffuse radiation. The annual course of scattered radiation at the equator generally repeats the course of a straight line. In other latitudes, more in summer than in winter, due to an increase in the total influx of solar radiation in summer.
The ratio between direct and scattered radiation varies depending on the height of the Sun, the transparency of the atmosphere and cloudiness.
Proportions between direct and diffuse radiation on different latitudes are not the same. In the polar and subpolar regions, scattered radiation makes up 70% of the total radiation flux. Its value, in addition to the low position of the Sun and cloudiness, is also affected by multiple reflections of solar radiation from the snow surface. Starting from temperate latitudes and almost to the equator, direct radiation prevails over scattered radiation. Its absolute and relative importance is especially great in the inland tropical deserts (Sahara, Arabia), characterized by minimal cloudiness and clear dry air. Along the equator, scattered radiation again dominates over the straight line due to the high humidity of the air and the presence of cumulus clouds that scatter solar radiation well.
With an increase in the height of the place above sea level, the absolute value increases significantly. 23. Annual amount of total solar radiation [MJ / (m 2 x year)]
naya and relative magnitude direct radiation and diffused radiation decreases, as the layer of the atmosphere becomes thinner. At an altitude of 50-60 km, the direct radiation flux approaches the solar constant.
All solar radiation - direct and diffuse, coming to the earth's surface, is called total radiation: (Q=S· sinh¤+D where Q is total radiation, S is direct, D is diffuse, h ¤ is the height of the Sun above the horizon. The total radiation is about 50% of the solar radiation arriving at the upper boundary of the atmosphere.
With a cloudless sky, the total radiation is significant and has a daily variation with a maximum around noon and an annual variation with a maximum in summer. Cloudiness reduces radiation, so in summer its arrival in the pre-noon hours is on average greater than in the afternoon. For the same reason, it is larger in the first half of the year than in the second.
A number of regularities are observed in the distribution of total radiation on the earth's surface.
Main regularity is that the total radiation is distributed zonal, descending from the equatorial tropi-
ic latitudes to the poles in accordance with the decrease in the angle of incidence of the sun's rays (Fig. 23). Deviations from the zonal distribution are explained by different cloudiness and transparency of the atmosphere. The highest annual values of total radiation 7200 - 7500 MJ / m 2 per year (about 200 kcal / cm 2 per year) fall on tropical latitudes, where there is little cloudiness and low air humidity. In the inland tropical deserts (Sahara, Arabia), where there is an abundance of direct radiation and almost no clouds, the total solar radiation even reaches more than 8000 MJ/m 2 per year (up to 220 kcal/cm 2 per year). Near the equator, the total radiation decreases to 5600 - 6500 MJ / m per year (140-160 kcal / cm 2 per year) due to significant cloudiness, high humidity and less air transparency. In temperate latitudes, the total radiation is 5000 - 3500 MJ / m 2 per year (≈ 120 - 80 kcal / cm 2 per year), in the polar regions - 2500 MJ / m per year (≈60 kcal / cm 2 per year). Moreover, in Antarctica it is 1.5-2 times greater than in the Arctic, primarily due to the greater absolute height of the mainland (more than 3 km) and therefore the low air density, its dryness and transparency, as well as cloudy weather. The zonality of the total radiation is better expressed over the oceans than over the continents.
The second important pattern total radiation is that the continents receive it more than the oceans, due to less (15-30%) cloudiness over
continents. The only exceptions are equatorial latitudes, since during the day the convective cloudiness over the ocean is less than over land.
Third feature is that in the northern, more continental hemisphere, the total radiation is generally greater than in the southern oceanic.
In June, the largest monthly amounts of solar radiation are received by the northern hemisphere, especially the inland tropical and subtropical regions. In temperate and polar latitudes, the amount of radiation varies slightly across latitudes, since the decrease in the angle of incidence of the rays is compensated by the duration of sunshine, up to the polar day beyond the Arctic Circle. In the southern hemisphere, with increasing latitude, radiation rapidly decreases and is zero beyond the Antarctic Circle.
In December, the southern hemisphere receives more radiation than the northern. At this time, the largest monthly amounts of solar heat fall on the deserts of Australia and the Kalahari; further in temperate latitudes, the radiation gradually decreases, but in Antarctica it increases again and reaches the same values as in the tropics. In the northern hemisphere, with increasing latitude, it rapidly decreases and is absent beyond the Arctic Circle.
In general, the largest annual amplitude of the total radiation is observed beyond the polar circles, especially in Antarctica, the smallest - in the equatorial zone.
All types of solar rays reach the earth's surface in three ways - in the form of direct, reflected and diffuse solar radiation.
direct solar radiation are rays coming directly from the sun. Its intensity (efficiency) depends on the height of the sun above the horizon: the maximum is observed at noon, and the minimum - in the morning and evening; from the time of year: maximum - in summer, minimum - in winter; from the height of the terrain above sea level (higher in the mountains than on the plain); on the state of the atmosphere (air pollution reduces it). The spectrum of solar radiation also depends on the height of the sun above the horizon (the lower the sun is above the horizon, the less ultraviolet rays).
reflected solar radiation- These are the rays of the sun reflected by the earth or water surface. She expresses herself percentage reflected rays to their total flux is called albedo. The albedo value depends on the nature of the reflecting surfaces. When organizing and conducting sunbathing, it is necessary to know and take into account the albedo of the surfaces on which sunbathing is carried out. Some of them are characterized by selective reflectivity. Snow completely reflects infrared rays, and ultraviolet - in lesser degree.
scattered solar radiation formed as a result of the scattering of sunlight in the atmosphere. Air molecules and particles suspended in it (the smallest droplets of water, ice crystals, etc.), called aerosols, reflect part of the rays. As a result of multiple reflections, some of them still reach the earth's surface; These are scattered rays of the sun. Mostly ultraviolet, violet and blue rays are scattered, which determines the blue color of the sky in clear weather. The proportion of scattered rays is large at high latitudes (in the northern regions). There the sun is low above the horizon, and therefore the path of the rays to the earth's surface is longer. On a long path, the rays meet more obstacles and scatter to a greater extent.
(http://new-med-blog.livejournal.com/204
Total solar radiation- all direct and diffuse solar radiation entering the earth's surface. Total solar radiation is characterized by intensity. With a cloudless sky, the total solar radiation has a maximum value around noon, and during the year - in summer.
Radiation balance
The radiation balance of the earth's surface is the difference between the total solar radiation absorbed by the earth's surface and its effective radiation. For the earth's surface
- the incoming part is the absorbed direct and scattered solar radiation, as well as the absorbed counter radiation of the atmosphere;
- the expenditure part consists of heat loss due to the own radiation of the earth's surface.
The radiation balance can be positive(daytime, summer) and negative(at night, in winter); measured in kW/sq.m/min.
The radiation balance of the earth's surface is the most important component of the heat balance of the earth's surface; one of the main climate-forming factors.
Thermal balance of the earth's surface- the algebraic sum of all types of heat input and output on the surface of land and ocean. The nature of the heat balance and its energy level determine the features and intensity of most exogenous processes. The main components of the ocean heat balance are:
- radiation balance;
- heat consumption for evaporation;
- turbulent heat exchange between the ocean surface and the atmosphere;
- vertical turbulent heat exchange of the ocean surface with the underlying layers; and
- horizontal oceanic advection.
(http://www.glossary.ru/cgi-bin/gl_sch2.c gi?RQgkog.outt:p!hgrgtx!nlstup!vuilw)tux yo)
Measurement of solar radiation.
Actinometers and pyrheliometers are used to measure solar radiation. The intensity of solar radiation is usually measured by its thermal effect and is expressed in calories per unit surface per unit of time.
(http://www.ecosystema.ru/07referats/slo vgeo/967.htm)
Measurement of the intensity of solar radiation is carried out by a Yanishevsky pyranometer complete with a galvanometer or a potentiometer.
When measuring total solar radiation, the pyranometer is installed without a shadow screen, while when measuring scattered radiation, with a shadow screen. Direct solar radiation is calculated as the difference between total and scattered radiation.
When determining the intensity of incident solar radiation on the fence, the pyranometer is installed on it so that the perceived surface of the device is strictly parallel to the surface of the fence. In the absence of automatic recording of radiation, measurements should be made after 30 minutes between sunrise and sunset.
Radiation falling on the surface of the fence is not completely absorbed. Depending on the texture and color of the fence, some of the rays are reflected. The ratio of reflected radiation to incident radiation, expressed as a percentage, is called surface albedo and measured by P.K. Kalitina complete with galvanometer or potentiometer.
For greater accuracy, observations should be carried out in a clear sky and with intense solar irradiation of the fence.
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