Solar radiation. Solar radiation or ionizing radiation from the sun

The most important source from which the Earth's surface and atmosphere receive thermal energy is the Sun. It sends a colossal amount of radiant energy into cosmic space: thermal, light, ultraviolet. Electromagnetic waves emitted by the Sun travel 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 Sun rays come to the surface of the Earth parallel to each other, but since the Earth is spherical, the sun's rays fall on different parts of its surface at different angles. When the Sun is at its zenith, its rays fall vertically and the Earth heats up more.

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

Solar radiation determines temperature regime air troposphere of the Earth.

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 under a cloudless sky is called straight. She carries greatest 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 solar radiation scattered by gas molecules and impurities, deviates from the straight path. Some of them reach the surface of the Earth, forming scattered solar radiation. Thanks to scattered radiation, light penetrates into places where direct sunlight (direct radiation) does not penetrate. This radiation creates daylight and gives color to the sky.

Total solar radiation

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

Rice. 1. Total solar radiation for the year

Distribution of solar radiation over the earth's surface

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

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

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

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

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

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

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

The sun's rays give up to 20% of their energy to the atmosphere, which is distributed throughout the entire thickness of the air, and therefore the heating of the air they cause is relatively small. The sun heats the Earth's surface, which transfers heat 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. That's how the atmosphere gets most heat - on average three times more than directly from the Sun.

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

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

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

Heat sources. In the life of the atmosphere is of decisive importance thermal energy. The main source of this energy is the Sun. As for the thermal radiation of the Moon, planets and stars, it is so insignificant for the Earth that it practically cannot be taken into account. Provides significantly more thermal energy internal heat Earth. According to geophysicists' calculations, the constant flow of heat from the Earth's interior increases the temperature of the earth's surface by 0°.1. But such a heat influx is still so small that there is no need to take it into account either. Thus, the only source of thermal energy on the surface of the Earth can be considered only the Sun.

Solar radiation. The sun, which has a photosphere (radiating surface) temperature of about 6000°, radiates energy into space in all directions. Part of this energy, in the form of a huge beam of parallel solar rays, hits the Earth. Solar energy that reaches the surface of the Earth in the form of direct rays from the Sun is called direct solar radiation. But not all solar radiation directed at the Earth reaches the earth's surface, since the sun's rays, passing through a thick layer of the atmosphere, are partially absorbed by it, partially scattered by molecules and suspended air particles, and some are reflected by clouds. That part of solar energy that is dissipated in the atmosphere is called scattered radiation. Scattered solar radiation travels through the atmosphere and reaches the Earth's surface. We perceive this type of radiation as uniform daylight, when the Sun is completely covered by clouds or has just disappeared below the horizon.

Direct and diffuse solar radiation, having reached the Earth's surface, is not completely absorbed by it. Part of the solar radiation is reflected from the earth's surface back into the atmosphere and is found there in the form of a stream of rays, the so-called reflected solar radiation.

The composition of solar radiation is very complex, which is associated with the very high temperature of the radiating surface of the Sun. Conventionally, according to wavelength, the spectrum of solar radiation is divided into three parts: ultraviolet (η<0,4<μ видимую глазом (η from 0.4μ to 0.76μ) and the infrared part (η >0.76μ). In addition to the temperature of the solar photosphere, the composition of solar radiation at the earth's surface is also influenced by the absorption and scattering of part of the sun's rays as they pass through the air shell of the Earth. In this regard, the composition of solar radiation at the upper boundary of the atmosphere and at the surface of the Earth will be different. Based on theoretical calculations and observations, it has been established that at the boundary of the atmosphere, ultraviolet radiation accounts for 5%, visible rays - 52% and infrared - 43%. At the earth's surface (at a solar altitude of 40°), ultraviolet rays account for only 1%, visible rays account for 40%, and infrared rays account for 59%.

Solar radiation intensity. The intensity of direct solar radiation is understood as the amount of heat in calories received per minute. from the radiant energy of the Sun's surface in 1 cm 2, located perpendicular to the sun's rays.

To measure the intensity of direct solar radiation, special instruments are used - actinometers and pyrheliometers; The amount of scattered radiation is determined by a pyranometer. Automatic registration of the duration of solar radiation is carried out by actinographs and heliographs. The spectral intensity of solar radiation is determined by a spectrobolograph.

At the boundary of the atmosphere, where the absorbing and scattering effects of the Earth's air shell are excluded, the intensity of direct solar radiation is approximately 2 feces by 1 cm 2 surfaces in 1 min. This quantity is called solar constant. Solar radiation intensity in 2 feces by 1 cm 2 in 1 min. provides such a large amount of heat during the year that it would be enough to melt a layer of ice 35 m thick if such a layer covered the entire earth's surface.

Numerous measurements of the intensity of solar radiation give reason to believe that the amount of solar energy arriving at the upper boundary of the Earth's atmosphere fluctuates by several percent.

In addition, some change in the intensity of solar radiation occurs during the year due to the fact that the Earth, in its annual rotation, moves not in a circle, but in an ellipse, at one of the foci of which the Sun is located. In this regard, the distance from the Earth to the Sun changes and, consequently, the intensity of solar radiation fluctuates. The greatest intensity is observed around January 3, when the Earth is closest to the Sun, and the lowest around July 5, when the Earth is at its maximum distance from the Sun.

For this reason, fluctuations in the intensity of solar radiation are very small and can only be of theoretical interest. (The amount of energy at maximum distance is related to the amount of energy at minimum distance as 100:107, i.e. the difference is completely negligible.)

Conditions of irradiation of the surface of the globe. The spherical shape of the Earth alone leads to the fact that the radiant energy of the Sun is distributed very unevenly on the earth's surface.

So, on the days of the spring and autumn equinox (March 21 and September 23), only at the equator at noon the angle of incidence of the rays will be 90° (Fig. 30), and as it approaches the poles it will decrease from 90 to 0°. Thus,

if at the equator the amount of radiation received is taken as 1, then at the 60th parallel it will be expressed as 0.5, and at the pole it will be equal to 0.

Depending on the time of year, not only the angle of incidence of the rays changes, but also the duration of illumination. If in tropical countries the length of day and night is approximately the same at all times of the year, then in polar countries, on the contrary, it is very different. So, for example, at 70° N. w. in summer the Sun does not set for 65 days at 80° N. sh. - 134, and at the pole -186. Because of this, radiation at the North Pole on the day of the summer solstice (June 22) is 36% greater than at the equator. As for the entire summer half of the year, the total amount of heat and light received by the pole is only 17% less than at the equator.

Thus, in the summer in polar countries, the duration of illumination largely compensates for the lack of radiation that is a consequence of the small angle of incidence of the rays. In the winter half of the year, the picture is completely different: the amount of radiation at the same North Pole will be equal to 0. As a result, over the year the average amount of radiation at the pole is 2.4 less than at the equator. From all that has been said, it follows that the amount of solar energy that the Earth receives through radiation is determined by the angle of incidence of the rays and the duration of irradiation. cm 2 In the absence of an atmosphere at different latitudes, the earth's surface would receive the following amount of heat per day, expressed in calories per 1

(see table on page 92). The distribution of radiation over the earth's surface given in the table is usually called solar climate.

We repeat that we have such a distribution of radiation only at the upper boundary of the atmosphere. Weakening of solar radiation in the atmosphere.

So far we have talked about the conditions for the distribution of solar heat over the earth's surface, without taking into account the atmosphere. Meanwhile, the atmosphere in this case is of great importance. Solar radiation, passing through the atmosphere, experiences dispersion and, in addition, absorption. Both of these processes together attenuate solar radiation to a significant extent. The sun's rays, passing through the atmosphere, first of all experience scattering (diffusion). Scattering is created by the fact that light rays, refracted and reflected from air molecules and particles of solid and liquid bodies in the air, deviate from the straight path

Scattering greatly attenuates solar radiation. With an increase in the amount of water vapor and especially dust particles, the dispersion increases and the radiation is weakened. In large cities and desert areas, where the dust content of the air is greatest, dispersion weakens the strength of radiation by 30-45%. Thanks to scattering, daylight is obtained that illuminates objects, even if the sun's rays do not directly fall on them. Scattering also determines the color of the sky.

Let us now dwell on the ability of the atmosphere to absorb radiant energy from the Sun. The main gases that make up the atmosphere absorb relatively little radiant energy. Impurities (water vapor, ozone, carbon dioxide and dust), on the contrary, have a high absorption capacity.

In the troposphere, the most significant impurity is water vapor. They absorb especially strongly infrared (long-wavelength), i.e., predominantly thermal rays. And the more water vapor in the atmosphere, the naturally more and. absorption. The amount of water vapor in the atmosphere is subject to large changes. Under natural conditions, it varies from 0.01 to 4% (by volume).

Ozone has a very high absorption capacity. A significant admixture of ozone, as already mentioned, is located in the lower layers of the stratosphere (above the tropopause). Ozone absorbs ultraviolet (short-wave) rays almost completely.

Carbon dioxide also has a high absorption capacity. It absorbs mainly long-wave, i.e., predominantly thermal rays.

Dust in the air also absorbs some solar radiation.

When heated by the sun's rays, it can significantly increase the air temperature.

Of the total amount of solar energy coming to the Earth, the atmosphere absorbs only about 15%.

Depending on the angle of incidence of the rays, not only the number of rays changes, but also their quality. During the period when the Sun is at its zenith (above the head), ultraviolet rays account for 4%,

visible - 44% and infrared - 52%. When the Sun is positioned near the horizon, there are no ultraviolet rays at all, visible 28% and infrared 72%.

The complexity of the atmosphere's influence on solar radiation is further aggravated by the fact that its transmission capacity varies greatly depending on the time of year and weather conditions. So, if the sky remained cloudless all the time, then the annual course of the influx of solar radiation at various latitudes could be expressed graphically as follows (Fig. 32). The drawing clearly shows that with a cloudless sky in Moscow in May, June and July, the heat more would be received from solar radiation than at the equator. Similarly, in the second half of May, June and the first half of July, more heat would be received at the North Pole than at the equator and in Moscow. We repeat that this would be the case in a cloudless sky. But in reality this does not work, because cloudiness significantly weakens solar radiation. Let's give an example shown on the graph (Fig. 33). The graph shows how much solar radiation does not reach the Earth's surface: a significant part of it is delayed by the atmosphere and clouds.

However, it must be said that the heat absorbed by the clouds partly goes to warm the atmosphere, and partly indirectly reaches the earth's surface.

Daily and annual variations in solar intensitylight radiation. The intensity of direct solar radiation at the Earth's surface depends on the height of the Sun above the horizon and on the state of the atmosphere (its dust content). If. If the transparency of the atmosphere was constant throughout the day, then the maximum intensity of solar radiation would be observed at noon, and the minimum at sunrise and sunset. In this case, the graph of the daily intensity of solar radiation would be symmetrical relative to half a day.

The content of dust, water vapor and other impurities in the atmosphere is constantly changing. In this regard, the transparency of the air changes and the symmetry of the solar radiation intensity graph is disrupted. Often, especially in summer, at midday, when the earth's surface is heated intensely, powerful upward air currents arise, and the amount of water vapor and dust in the atmosphere increases.

This results in a significant reduction in solar radiation at midday; The maximum intensity of radiation in this case is observed in the pre-noon or afternoon hours. The annual variation in the intensity of solar radiation is also associated with changes in the height of the Sun above the horizon throughout the year and with the state of transparency of the atmosphere in different seasons. In the countries of the northern hemisphere, the highest height of the Sun above the horizon occurs in the month of June. But at the same time, the greatest dustiness of the atmosphere is observed. Therefore, the maximum intensity usually occurs not in the middle of summer, but in the spring months, when the Sun rises quite high* above the horizon, and the atmosphere after winter remains relatively clean. To illustrate the annual variation of solar radiation intensity in the northern hemisphere, we present data on monthly average midday radiation intensity values ​​in Pavlovsk.

The amount of heat from solar radiation.

The role of direct and diffuse radiation in the annual amount of heat received by the earth's surface at different latitudes of the globe is different. At high latitudes, the annual amount of heat is dominated by scattered radiation. With decreasing latitude, direct solar radiation becomes dominant.

For example, in Tikhaya Bay, diffuse solar radiation provides 70% of the annual amount of heat, and direct radiation only 30%. In Tashkent, on the contrary, direct solar radiation provides 70%, scattered only 30%. Reflectivity of the Earth. Albedo. As already indicated, the Earth's surface absorbs only part of the solar energy that reaches it in the form of direct and diffuse radiation. The other part is reflected into the atmosphere. The ratio of the amount of solar radiation reflected by a given surface to the amount of radiant energy flux incident on this surface is called albedo.

Albedo is expressed as a percentage and characterizes the reflectivity of a given surface area.

Albedo depends on the nature of the surface (soil properties, presence of snow, vegetation, water, etc.) and on the angle of incidence of the Sun's rays on the Earth's surface. So, for example, if the rays fall on the earth's surface at an angle of 45°, then:

From the above examples it is clear that the reflectivity of different objects is not the same.

It is greatest near snow and least near water. However, the examples we took relate only to those cases when the height of the Sun above the horizon is 45°. As this angle decreases, the reflectivity increases. So, for example, at a solar altitude of 90°, water reflects only 2%, at 50° - 4%, at 20° - 12%, at 5° - 35-70% (depending on the condition of the water surface). The Earth, receiving solar energy, heats up and itself becomes a source of heat radiation into space. However, the rays emitted by the earth's surface are very different from the sun's rays. The earth emits only long-wave (λ 8-14 μ) invisible infrared (thermal) rays. The energy emitted by the earth's surface is called terrestrial radiation. Radiation from the Earth occurs... day and night. The higher the temperature of the emitting body, the greater the radiation intensity. Terrestrial radiation is determined in the same units as solar radiation, i.e. in calories from 1 cm 2 surfaces in 1 min. Observations have shown that the amount of terrestrial radiation is small. Usually it reaches 15-18 hundredths of a calorie. But, acting continuously, it can give a significant thermal effect.

The strongest terrestrial radiation is obtained with a cloudless sky and good transparency of the atmosphere. Cloud cover (especially low clouds) significantly reduces terrestrial radiation and often brings it to zero. Here we can say that the atmosphere, together with the clouds, is a good “blanket” that protects the Earth from excessive cooling. Parts of the atmosphere, like areas of the earth's surface, emit energy according to their temperature. This energy is called atmospheric radiation. The intensity of atmospheric radiation depends on the temperature of the radiating part of the atmosphere, as well as on the amount of water vapor and carbon dioxide contained in the air.

Atmospheric radiation belongs to the long-wave group. It spreads in the atmosphere in all directions; a certain amount of it reaches the earth's surface and is absorbed by it, the other part goes into interplanetary space. ABOUT

the arrival and consumption of solar energy on Earth. cm 2 The earth's surface, on the one hand, receives solar energy in the form of direct and diffuse radiation, and on the other hand, loses part of this energy in the form of terrestrial radiation. As a result of the arrival and consumption of solar energy, some result is obtained. In some cases, this result can be positive, in others negative. Let us give examples of both. feces January 8. The day is cloudless. On 1 feces earth's surface received in 20 days direct solar radiation and 12 scattered radiation; in total, this gives 32 cal. During the same time, due to radiation 1 direct solar radiation and 12 cm? feces earth's surface lost 202

As a result, in accounting language, the balance sheet has a loss of 170 (negative balance). from scattered radiation 46 direct solar radiation and 12 In total, therefore, the earth's surface received 1 cm 2 676 direct solar radiation and 12 173 lost through terrestrial radiation direct solar radiation and 12 The balance sheet shows a profit of 503 feces(balance is positive).

From the examples given, among other things, it is completely clear why temperate latitudes are cold in winter and warm in summer.

Use of solar radiation for technical and domestic purposes. Solar radiation is an inexhaustible natural source of energy. The amount of solar energy on Earth can be judged by this example: if, for example, we use the heat of solar radiation falling on only 1/10 of the area of ​​the USSR, then we can obtain energy equal to the work of 30 thousand Dnieper hydroelectric power plants.

People have long sought to use the free energy of solar radiation for their needs. To date, many different solar power plants have been created that operate using solar radiation and are widely used in industry and to meet the domestic needs of the population. In the southern regions of the USSR, solar water heaters, boilers, salt water desalination plants, solar dryers (for drying fruits), kitchens, bathhouses, greenhouses, and devices for medicinal purposes operate on the basis of the widespread use of solar radiation in industry and public utilities. Solar radiation is widely used in resorts to treat and improve people's health.

Dazhbog among the Slavs, Apollo among the ancient Greeks, Mithra among the Indo-Iranians, Amon Ra among the ancient Egyptians, Tonatiuh among the Aztecs - in ancient pantheism people called the Sun God with these names.

Since ancient times, people have understood how important the Sun is for life on Earth and deified it.

The luminosity of the Sun is enormous and amounts to 3.85x10 23 kW. Solar energy acting on an area of ​​just 1 m 2 is capable of charging a 1.4 kW engine.

The source of energy is the thermonuclear reaction taking place in the core of the star.

The 4 He formed in this case constitutes almost (0.01%) all the helium of the earth.

The star of our system emits electromagnetic and corpuscular radiation. From the outside of the Sun's corona, the solar wind, consisting of protons, electrons and α-particles, “blows” into outer space. With the solar wind, 2-3x10 -14 masses of the star are lost annually. Magnetic storms and aurora are associated with corpuscular radiation.

Electromagnetic radiation (solar radiation) reaches the surface of our planet in the form of direct and scattered rays. Its spectral range is:

• ultraviolet radiation;
• X-rays;
• γ-rays.

The short-wave part accounts for only 7% of the energy. Visible light makes up 48% of the sun's radiation energy. It is mainly composed of blue-green radiation spectrum, 45% is infrared radiation and only a small part is represented by radio radiation.

Ultraviolet radiation, depending on the wavelength, is divided into:

Most of the long wavelength ultraviolet radiation reaches the earth's surface. The amount of UV-B energy reaching the surface of the planet depends on the state of the ozone layer. UV-C is almost completely absorbed by the ozone layer and atmospheric gases. Back in 1994, WHO and WMO proposed introducing an ultraviolet index (UV, W/m2).

The visible part of the light is not absorbed by the atmosphere, but waves of some spectrum are scattered. Infrared color or mid-wave thermal energy is mainly absorbed by water vapor and carbon dioxide. The source of the long-wave spectrum is the earth's surface.

All of the above ranges are of great importance for life on Earth. A significant portion of solar radiation does not reach the Earth's surface. The following types of radiation are recorded at the surface of the planet:

• 1% ultraviolet;
• 40% optical;
• 59% infrared.

The intensity of solar radiation depends on:

• latitude;
• season;
• time of day;
• atmospheric conditions;
• features and relief of the earth's surface.

In different parts of the Earth, solar radiation affects living organisms differently.

Photobiological processes occurring under the influence of light energy, depending on their role, can be divided into the following groups:

• synthesis of biologically active substances (photosynthesis);
• photobiological processes that help navigate in space and help obtain information (phototaxis, vision, photoperiodism);
• damaging effects (mutations, carcinogenic processes, destructive effects on bioactive substances).

Light radiation has a stimulating effect on photobiological processes in the body - the synthesis of vitamins, pigments, cellular photostimulation. The sensitizing effect of sunlight is currently being studied.

Ultraviolet radiation, affecting the skin of the human body, stimulates the synthesis of vitamins D, B4 and proteins, which are regulators of many physiological processes. Ultraviolet radiation affects:

• metabolic processes;
• immune system;
• nervous system;
• endocrine system.

The sensitizing effect of ultraviolet radiation depends on the wavelength:

The stimulating effect of sunlight is expressed in increasing specific and nonspecific immunity. For example, in children who are exposed to moderate natural UV radiation, the number of colds is reduced by 1/3. At the same time, the effectiveness of treatment increases, there are no complications, and the period of the disease is shortened.

The bactericidal properties of short-wave UV radiation are used in medicine, the food industry, and pharmaceutical production for the disinfection of environments, air, and products. Ultraviolet radiation destroys the tuberculosis bacillus within a few minutes, staphylococcus in 25 minutes, and the causative agent of typhoid fever in 60 minutes.

Nonspecific immunity, in response to ultraviolet irradiation, responds with an increase in compliment titers and agglutination, and an increase in the activity of phagocytes. But increased UV radiation causes pathological changes in the body:

• skin cancer;
• solar erythema;
• damage to the immune system, which is expressed in the appearance of freckles, nevi, solar lentigines.

Visible sunlight:

• makes it possible to obtain 80% of the information using a visual analyzer;
• accelerates metabolic processes;
• improves mood and overall well-being;
• warms;
• affects the state of the central nervous system;
• determines circadian rhythms.

The degree of exposure to infrared radiation depends on the wavelength:

• long-wave - has weak penetrating ability and is largely absorbed by the surface of the skin, causing erythema;
• short-wave – penetrates deep into the body, providing a vasodilator, analgesic, and anti-inflammatory effect.

In addition to its impact on living organisms, solar radiation is of great importance in shaping the Earth's climate.

The importance of solar radiation for climate

The sun is the main source of heat that shapes the earth's climate. In the early stages of the Earth's development, the Sun emitted 30% less heat than it does now. But thanks to the saturation of the atmosphere with gases and volcanic dust, the climate on Earth was humid and warm.

There is a cyclicity in the intensity of insolation, which causes warming and cooling of the climate. Cyclicity explains the Little Ice Age, which began in the 14th-19th centuries. and climate warming observed in the period 1900-1950.

In the history of the planet, there is a periodicity of changes in the inclination of the axis and the eccentricity of the orbit, which changes the redistribution of solar radiation on the surface and affects the climate. For example, these changes are reflected in the increase and decrease in the area of ​​the Sahara Desert.

Interglacial periods last about 10,000 years. The Earth is currently in an interglacial period called the Heliocene. Thanks to early human agricultural activities, this period lasted longer than expected.

Scientists have described 35-45 year cycles of climate change, during which a dry and warm climate changes to a cool and humid one. They affect the filling of inland water bodies, the level of the World Ocean, and changes in glaciation in the Arctic.

Solar radiation is distributed differently. For example, in the middle latitudes in the period from 1984 to 2008, there was an increase in total and direct solar radiation and a decrease in scattered radiation. Changes in intensity are also observed throughout the year. Thus, the peak occurs in May-August, and the minimum occurs in the winter.

Since the height of the Sun and the duration of daylight hours in summer are greater, this period accounts for up to 50% of the total annual radiation. And in the period from November to February - only 5%.

The amount of solar radiation falling on a certain surface of the Earth affects important climatic indicators:

• temperature;
• humidity;
• Atmosphere pressure;
• cloudiness;
• precipitation;
• wind speed.

An increase in solar radiation increases temperature and atmospheric pressure; other characteristics are in the opposite ratio. Scientists have found that the levels of total and direct radiation from the Sun have the greatest impact on climate.

Solar protection measures

Solar radiation has a sensitizing and damaging effect on humans in the form of heat and sunstroke, and the negative effects of radiation on the skin. Nowadays, a large number of celebrities have joined the anti-tanning movement.

Angelina Jolie, for example, says that she does not want to sacrifice several years of her life for two weeks of tanning.

To protect yourself from solar radiation, you must:

1. sunbathing in the morning and evening hours is the safest time;
2. use sunglasses;
3. during the period of active sun:

• cover the head and open areas of the body;
• use sunscreen with a UV filter;
• purchase special clothing;
• protect yourself with a wide-brimmed hat or sun umbrella;
• observe drinking regime;
• avoid intense physical activity.

When used wisely, solar radiation has a beneficial effect on the human body.

SOLAR RADIATION