Although the solar radiation energy received by the earth is only 1/2.2 billion of the total radiation energy emitted by the sun into space, it is the earthAtmospheric motionThe main source of energy is also the main source of light and heat of the earth.
The solar radiation energy reaching the upper boundary of the earth's atmosphere is called astronomical solar radiation.On EarthAverage distance between the sun and the earthThe total energy of the full spectrum of solar radiation received by the unit area of the upper boundary of the earth's atmosphere perpendicular to the solar rays in unit time is calledSolar constant。The common unit of solar constant is watt/meter ².Due to different observation methods and techniques, the solar constant values obtained are different.The solar constant is 1368 W/m2.Solar radiation is a kind ofShortwave radiation。
The distribution of global annual total radiation reaching the surface is basically zonal, onlyLow latitudeThe area was damaged.In the equatorial region, the annual total radiation is not the highest due to cloudy weather.In the Northern and Southern HemispheresSubtropical high beltEspecially in the desert areas of the continent, the annual total radiation is relatively large, and the maximum value is in northeast Africa.
The distribution of solar radiation in the upper boundary of the atmosphere is determined by theAstronomical positionDetermined, calledAstronomical radiation。The climate determined by astronomical radiation is calledAstronomical climate。Astronomical climate reflectsglobal climateThe basic outline of spatial distribution and temporal change.
Detailed introduction
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Daily astronomy
world meteorological organization(WMO) published the solar constant value of 1368 W/m2 in 1981.More than 99% of the solar radiation spectrum in the upper boundary of the earth's atmosphere is between 0.15 and 4.0 microns in wavelength.About 50% of the solar radiation energyVisible spectrum7% is in the ultraviolet spectral region (wavelength<0.4 μ m), 43% is in the infrared spectral region (wavelength>0.76 μ m), and the maximum energy is at the wavelength 0.475 μ m.
Since the wavelength of solar radiation is higher than that of ground andAtmospheric radiationThe wavelength (about 3-120 μ m) is much smaller, so it is also called shortwave radiation, ground and atmospheric radiationLong wave radiation。Solar activity andSun earth distanceThe change of solar radiation energy in the upper boundary of the earth's atmosphere will be caused by the change of solar radiation energy.
Strong solar radiation storm
Solar radiation passes through the atmosphere and some reaches the ground, which is called direct solar radiation;The other part is absorption, scattering and reflection of atmospheric molecules, dust and water vapor in the atmosphere.One part of the scattered solar radiation returns to the space, and the other part reaches the ground. The part that reaches the ground is called the scattered solar radiation.The sum of scattered solar radiation and direct solar radiation reaching the ground is called total radiation.
When solar radiation passes through the atmosphere, its intensity and spectral energy distribution change.The solar radiation energy reaching the ground is much smaller than the upper boundary of the atmosphereSolar spectrumThe upper energy distribution is almost extinct in the ultraviolet spectral regionVisible spectrumThe area is reduced to 40% and increased to 60% in the infrared spectrum area.
In the upper boundary of the earth's atmosphere, the Northern Hemispherethe summer solsticeThe total daily radiation is the largest, and the distribution is relatively uniform from the pole to the equator;At the winter solstice, the total daily radiation in the Northern Hemisphere is the smallest, zero in the polar circle, and the difference between north and south is the largest.The opposite is true in the southern hemisphere.At the spring and autumn equinoxes, the distribution of the total daily radiation is proportional to the cosine of latitude.In the area between the Tropic of Cancer and the Tropic of Capricorn, the total daily radiation is the largest twice a year, with a small annual change.The higher the latitude, the greater the change of the total daily radiation.
The distribution of global annual total radiation reaching the surface is basically zonal, and only in low latitude areas is damaged.stayequatorIn the region, the annual total radiation is not the highest due to cloudy weather.In the subtropical high belt of the northern and southern hemispheres, especially in the continental desert area, the annual total radiation is large, and the maximum value is in northeast Africa.
influence factor
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The intensity of solar radiation refers to the intensity of solar radiation reaching the ground.The absorption, reflection and scattering of solar radiation by the atmosphere greatly weaken the solar radiation reaching the ground.However, there are still many factors that affect the intensity of solar radiation, making the amount of solar radiation reaching different regions different.There are four main factors affecting the intensity of solar radiation.[3]
1. Latitude position
If the latitude is low, the noonday solar altitude angle is large, the distance of solar radiation passing through the atmosphere is short, it is less weakened by the atmosphere, and the solar radiation reaching the ground is more;On the contrary, less.This is the main reason why the solar radiation decreases from low latitude to high latitude.[3]The earth revolves around the sunThe orbit of is elliptical, and the sun is at one of the two focal points.
Therefore, the distance between the sun and the earth is changing at all times.Every January 2-5 passes through perihelion, and July 3-4 passes through aphelion.The intensity of solar radiation received by the earth is inversely proportional to the square of the distance between the sun and the earth.Solar ray and ground planeincluded anglebe calledSolar altitude angleIt changes day by day and year by year.If the solar altitude angle is large, the solar radiation is strong.
2. Weather conditions
In sunny weather, due to the few and thin clouds, the weakening effect of the atmosphere on solar radiation is weak, and the solar radiation reaching the ground is strong;In rainy weather, due to the thick and numerous clouds, the weakening effect of the atmosphere on the solar radiation is strong, and the solar radiation reaching the ground is weak.For example, the equatorial region is controlled by the equatorial low pressure zone, with more convective rain, while the subtropical region is controlled by the subtropical high, with more sunny weather, so the solar radiation in the equatorial region is weaker than that in the subtropical region.[3]
3. Altitude
The altitude is high, the air is thin, the weakening effect of the atmosphere on the solar radiation is weak, and the solar radiation reaching the ground is strong;On the contrary, it is weak.This is the main reason why the Qinghai Tibet Plateau has become the region with the strongest solar radiation in China.This is the main reason why the Qinghai Tibet Plateau has become the region with the strongest solar radiation in China.[3]
4. Length of sunshine
Long sunshine duration, obtaining strong solar radiation;The sunshine time is short and the solar radiation is weak.For example, there is high temperature in the south and north of China in summer, and the temperature difference is not large, because the higher the latitude, the longer the day time, which makes up for the energy loss due to the low solar altitude angle.[3]The length of day is the length of time between sunrise and sunset.
The length of day in the four seasons above the equator is 12 hours. The length of day outside the equator changes in the four seasons. SpringAutumnal equinox12 hour day, summer solsticeWinter SolsticeThe day length is 14 hours and 51 minutes and 9 hours and 09 minutes respectively, and polar day and night phenomena occur at latitude 66 ° 33 '.The winter and summer seasons in the northern and southern hemispheres are opposite.
Solar constant
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Day and night are due toearth rotationThe seasons are caused by an angle of 23 ° 27 'between the rotation axis of the earth and the rotation axis of the earth's orbit around the sun.The earth rotates from west to east every day around the "axis" that passes through its south and north poles.Every revolution is a day and night, so the earth rotates 15 ° every hour.In addition to its rotation, the earth moves around the sun once a year in an elliptical orbit with a small eccentricity.The Earth's Rotation Axis and Orbital PlanenormalIt is always 23.5 °.
When the earth revolves, the direction of its rotation axis remains unchanged and always points to the north pole of the earth.So when the earth is in different positions of its orbit,sunlightThe direction of projection on the earth is also different, thus forming the four seasons on the earth.At noon every day, the sun is always the highest.In the tropical low latitude area (that is, the area between the north and south latitude of the equator 23 ° 27 '), the sun has two vertical incidences in a year. In the higher latitude area, the sun is always close to the equator.In the Arctic and Antarctic regions (more than 90 °~23 ° 27 ′ in the northern and southern hemispheres), the sun stays below the horizon for a long time in winter, and stays above the horizon for a long time in summer.
Since the earth moves around the sun in an elliptical orbit, the distance between the sun and the earth is not a constant, and the distance between the sun and the earth is different every day in a year.As we all know, the radiation intensity and distance at a certain pointradiation sourceIs inversely proportional to the square of the distance, which means thatSolar radiation intensityIt will vary with the distance between the sun and the earth.However, due to the large distance between the sun and the earth (the average distance is 1.5 × 10 ^ 8km)atmosphereThe external solar radiation intensity is almost a constant.Therefore, people use the so-called "solar constant" to describe the solar radiation intensity above the earth's atmosphere.It refers to the averageSun earth distanceThe accepted sun on the unit surface area perpendicular to the solar radiation at the upper boundary of the earth's atmosphereradiant energy。The standard value of the solar constant measured by various advanced means is 1353 W/m ².The change of solar radiation intensity caused by the change of the distance between the sun and the earth in a year does not exceed 3.4%.
Change characteristics
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Astronomical radiation
Spatiotemporal variation characteristics of astronomical radiation
① Throughout the year, the equator receives the most radiation and the polar region receives the least radiation.This uneven distribution of heat will inevitably lead to temperature differences in different latitudes of the earth's surfaceCold Climate ；
② Astronomical radiation is larger in summer and smaller in winter, which leads to higher temperature in summer and lower temperature in winter.The weakening effect of the atmosphere on solar radiation includes the absorption, scattering and reflection of solar radiation by the atmosphere.When the solar radiation passes through the whole atmosphere, the ultraviolet light below 0.29 μ m is almost absorbedvisible lightThe atmospheric absorption of the area is very little.There is a strong absorption band in the infrared region.
The substances in the atmosphere that absorb solar radiation mainly include oxygen, ozone, water vapor and liquid water, followed by carbon dioxide, methane, nitrous oxide and dust.Clouds can strongly absorb and scatter solar radiation, and also strongly absorb solar radiation reflected from the ground.The average reflectivity of clouds is 0.50~0.55.
Ground radiation
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Wavelength of solar energy
While absorbing solar radiation, the earth's surface transmits most of its energy to the atmosphere in the form of radiation.The way that the ground surface radiates outward day and night with its own heat is calledGround radiation。becauseSurface temperatureIt is much lower than the sun (the average temperature of the ground surface is about 300K). Therefore, the main energy of the ground radiation is concentrated between 1 and 30 microns. The average wavelength of the maximum radiation is 10 microns, which belongs to the infrared region. Compared with the solar short wave radiation, it is called the ground long wave radiation.
The radiation capacity of the ground mainly depends on the temperature of the ground itself.As the radiation capacity increases with the temperature of the radiator,Ground temperatureHigh, strong ground radiation;At night, the ground temperature is low and the ground radiation is weak.The radiation on the ground is long wave radiation, which is absorbed by water vapor and carbon dioxide in the atmosphere, especially by water vapor.Therefore, the atmosphere, especially the atmosphere in the troposphere, is mainly heated by absorbing ground radiation.
According to the relationship between radiation intensity, when the ground temperature increases, the ground radiation increases. If other conditions (temperature, cloud conditions, etc.) remain unchanged, the effective ground radiation increases.air temperature At high altitude, the atmospheric inverse radiation increases, and if other conditions remain unchanged, the effective ground radiation decreases.
The air contains more water vapor and water vapor condensate, so the ability of water vapor to radiate long wave radiation is relatively strong, which increases the atmospheric reverse radiation, and thus weakens the effective radiation on the ground.There are clouds in the sky, especially dense low clouds. The atmospheric reverse radiation is stronger, which weakens the effective radiation on the ground more.Therefore, a cloudy night is usually warmer than a cloudless night.This function of the cloud cover is also called the heat preservation effect of the cloud cover.The reason why the artificial smoke screen can prevent frost lies in this.
The higher the temperature of objects in nature, the shorter the wavelength of their radiation waves. Because the temperature of the sun's surface is very high, about 6000K, the solar radiation is dominated by short waves, and the energy is huge.The sun loses 4 million tons of mass per second and turns into energy that shoots into space. Although the energy that the earth can capture is only 1/2.2 billion of it, it can still get the heat equivalent to 400 million tons of bituminous coal per minute. Therefore, the impact of solar radiation on the earth and human beings is very great. The sun only consumes 0.03% of its mass in a long time of 5 billion years,The sun we see is in a stable and vigorous middle age. Don't worry about the life span of the sun. The rumor that the earth is going to be destroyed is obviously a fallacy.
Solar irradiation
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The radiation or "solar radiation" that the sun shines on the ground plane consists of two parts - direct solar radiation and diffuse solar radiation.When solar radiation passes through the atmosphere and reaches the ground, the absorption, reflection andscatteringIt not only weakens the radiation intensity, but also changes the direction and spectral distribution of radiation.
Therefore, the solar radiation actually reaching the ground is usually composed of direct and diffuse radiation.Direct radiation refers to radiation directly from the sun whose radiation direction does not change;Diffuse is caused byAtmospheric reflectionAnd solar radiation whose direction has changed after scattering, which is composed of three parts: scattering around the sun (bright sky light around the sun surface),Horizon circleScattering (bright or dark sky around the horizon), and other sky scattered radiation.In addition, the non horizontal plane also receivesReflected radiation。
The sum of direct solar radiation, diffuse solar radiation and reflected solar radiation is the total solar radiation or global solar radiation.A lens or reflector can be used to focus direct sunlight.If the concentration rate is high, highenergy density , but the diffuse solar radiation is lost.If the concentration rate is low, you can also focus on some diffuse sunlight around the sun.
Diffuse solar radiation varies widely. When the sky is clear and cloudless, the diffuse solar radiation is 10% of the total solar radiation.However, when the sky is covered with dark clouds and the sun cannot be seen, the total solar radiation is equal to diffuse solar radiation.Therefore, the energy collected by the collective collector is usually much less than that collected by the non collective collector.The reflected solar radiation is generally weak, but when the ground is covered with ice and snow, the reflected solar radiation on the vertical plane can reach 40% of the total solar radiation.
The solar radiation reaching the ground is mainly affected by the thickness of the atmosphere.The thicker the atmosphere, the more serious the absorption, reflection and scattering of solar radiation, and the less solar radiation reaching the ground.In addition, the condition and quality of the atmosphere also affect the solar radiation reaching the ground.Obviously, the path length of solar radiation through the atmosphere is related to the direction of solar radiation.
A is a point on the earth's sea level. When the sun is at the zenith position S, the path of solar radiation through the atmosphere to point A is OA.When Chengyang is at point S, its path through the atmosphere to point A is 0A.O. The ratio of A to OA is calledAir quality。It represents the ratio of the path of solar radiation passing through the earth's atmosphere to the path of the sun when it is vertically incident at the zenith, usually expressed by the symbol m, and sets the atmospheric mass m=1 when the sun is vertically incident at the sea level at the standard atmospheric pressure and 0 ℃.In the formula, h is the height angle of the sun.Obviously, the intensity of solar radiation reaching the ground is different in different regions, seasons and meteorological conditions on the earth.
Generally, according to the geographical and meteorological conditions of various places, the solar radiation intensity reaching the ground has been made into various charts for engineering use. They are not only important data for the use of solar energy, but also for the heating and air-conditioning design of buildings.
Wavelength distribution
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The wavelength distribution of solar energy can be simulated by a blackbody radiation with a temperature of 5800K.Solar energy wavelength distributionultraviolet, visible light andinfrared lightband。These bands are subject toAtmospheric attenuationThe degree of influence varies.Visible radiationMost of the ozone can reach the ground, but the ozone in the upper atmosphere absorbs most of the ultraviolet radiation.
Cosmic microwave background radiation
becauseozone layerThin, especially in the Antarctic and Arctic regions, more and more ultraviolet radiation reaches the ground.Some of the incident infrared radiation is absorbed by carbon dioxide, water vapor and other gases, while most of the longer wavelength infrared radiation from the earth's surface at night is transmitted to outer space.
The accumulation of these greenhouse gases in the upper atmosphere may increase the absorption capacity of the atmosphere, leading to global warming and cloudy weather.Although ozone reduction has an impact onSolar collectorHas little impact, butgreenhouse effectIt may increase the scattered radiation and may seriously affect the function of the solar collector.
radiation intensity
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Influence of infrared radiation
Indicating the intensity of solar radiationphysical quantity, called solar radiation intensity.The unit is joule/cm2 · min, that is, the solar radiation energy vertically projected onto the unit area in unit time.
The solar radiation intensity of the upper boundary of the atmosphere depends on the altitude angle of the sunSun earth distanceandSunshine time。The greater the solar altitude angle, the greater the solar radiation intensity.Because when the same beam of light is directly irradiated, the area of exposure is the smallest, and the solar radiation obtained per unit area is more;On the contrary, when the beam is oblique, the radiation area is large,unit area Less solar radiation is obtained on the.
The solar altitude angle varies from time to time and from place to place.In a day,Solar altitude angleNoon is greater than morning and evening;Summer is greater than winter;The low latitude area is larger than the high latitude area.The distance between the sun and the earth means that when the earth revolves around the sun, the distance between the sun and the earth changes constantly because the orbit is elliptical.
The intensity of solar radiation obtained on the earth is inversely proportional to the square of the distance between the sun and the earth.When the earth is at perihelion, the solar radiation obtained is greater than that at aphelion.
According to research, when the earth passed through perihelion in early January, the solar radiation obtained on the unit area of the surface was 7% more than that when it passed through aphelion in early July.
The intensity of solar radiation is proportional to the duration of sunshine.The duration of sunshine varies with latitude and season.
Atmospheric inverse radiation
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Cosmic microwave background radiation
The atmosphere absorbs the groundLong wave radiationAt the same time, it radiates energy outward in the form of radiation.This way of radiating energy from the atmosphere is calledAtmospheric radiation。Because the temperature of the atmosphere itself is low, the wavelength of the radiated energy is longer, so it is also calledAtmospheric long waveRadiation.
The direction of atmospheric radiation is both upward and downward.The downward part of the atmospheric radiation is just opposite to the direction of the ground radiation, so it is calledAtmospheric inverse radiation。The atmospheric inverse radiation is an important source of ground heat.
Due to the existence of atmospheric reverse radiation, the actual heat loss on the ground is less than the heat released by the long wave radiation on the ground. This heat preservation effect of the atmosphere is called the greenhouse effect of the atmosphere.The heat preservation effect of the atmosphere has increased the temperature near the surface by about 18 ℃.The moon has no atmosphere like the earth, so its surface temperatureDiurnal variationSevere, daytimesurface temperature It can reach 127 ℃ and drop to - 183 ℃ at night.
Effective radiation
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Influence of infrared radiation
solar radiation
The heat exchange between the ground and the atmosphere is carried out in the form of long wave radiation, and the atmosphere plays a heat preservation role on the ground.This function is availableEffective ground radiation(F0) means: F0=Fg - δ EA The ground effective radiation is the difference between the ground radiation and the atmospheric reverse radiation (δ EA) absorbed by the ground.Generally, the ground temperature is higher than the atmospheric temperature, so the ground radiation is stronger than the atmospheric reverse radiation.
The intensity of ground effective radiation varies with ground temperature, air temperature, air humidity and cloud conditions.
Energy source
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The energy of radiation comes from hydrogen nuclear fusion.At high temperature and high pressure, 4hydrogen atomThrough a series ofFusion reactionIt becomes a helium nucleus and releases a lot of heat.Such continuous fusion continuously provides energy for the sun.
Energy action
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To the Earth
The solar radiation energy reaching the earth is only a small part of the total solar radiation energy, but its role is quite large[4]yesSurface of the earthThe main source of energy.
First, the impact on the geographical environment.For example, the rock is weathered due to the direct effect of temperature change.Indirect effect: the atmosphere, water and living things on the earth are geographical environment elements, and their own development and changes as well as the interrelationship between various elements are mostly completed in the process of driving by the sun.The earth's surface is divided into five zones.Why divide five belts?Because the latitude of different places on the earth's surface is different, the solar heat obtained in different latitude areas is different.For example, in the tropics, the sun can shine directly and get the most heat in a year;The altitude of the cold zone sun is very low, and there are long polar nights, so the heat obtained is the least.That is, because of the latitude difference of solar radiation, the heat obtained by different regions is different.But in places with heat surplus, such as the equator, the temperature is not getting higher and higher;Heat loss places, such asBipolarThe temperature is not getting lower and lower, but remains relatively stable.For the whole surface, the heat should be balanced, so heat transfer will occur where the heat is surplus or insufficient.
Second, solar radiation provides energy for our production and life.People's most direct feeling of solar radiation is that it is the main energy for people's production and life.For example, the growth of plants needs light and heat, and the drying of clothes needs sunshine. The coal, oil and other fossil fuels used in large quantities in industry are converted from solar energy, which is called "stored solar energy".And the solar cookersolar heater, solar dryer, solar house, solar power generation, solar cell, etc.In addition to direct use of solar energyHydroenergy、Wind energyIt also comes from the sun.Lhasa, the capital of Tibet, has another nickname:“Sunlight City”。Why is it called this name?Because Tibet Autonomous Region is located inQinghai Tibet PlateauThe terrain is high, the distance from sunlight to the surface is short, the air is thin, and there are few clouds in the sky, so the solar radiation is strong,sunshineIt is called "Sunshine City" for a long time.Chongqing, a municipality directly under the Central Government, has a nickname, "Fog City" of China.Why is this place foggy in a year?This place has a low altitude and is affected by the terrain,Sichuan Basin It makes it difficult for water vapor to accumulate and increaseSouthwest monsoonIt's impossible to crossQinling Mountains；It can only affect the Sichuan Basin, so it brings a lot of water vapor and is close to the sea. Therefore, it is cloudy and rainy in a year, and the sky is often overcast, so there is less light and solar radiation is poor.So people often use "Shugou barking at the sun" to describe the climate characteristics of Sichuan Basin.
For the solar system
In addition, the force of light acting on the object is called radiation pressure.The pressure of solar radiation can blow something out of the solar system, and can also make something fall onto the sun.Let's study a particle near the sun.The pressure of solar radiation on the particle is proportional to the cross-sectional area of the particle.The gravity acting on the particle is proportional to its mass, and the mass is proportional to its volume.
If the particle's linearity is X, its cross-sectional area is proportional to X ^ 2, and its volume is proportional to X ^ 3;So as long as the particles are small enough, the ratio of X ^ 2 to X ^ 3 can be arbitrarily large.When X=1 unit, X ^ 2=1 unit ^ 2, X ^ 3=1 unit ^ 3;When X=0.1 unit, X2=0.01 unit ^ 2, X3=0.001 unit ^ 3.So when X is small enough, the solar radiation pressure can exceed gravity, which is why the tail of comets always faces away from the sun.
Assuming that gravity is greater than the pressure of radiation, the particles are bound in the solar system. When the particles move around the sun, the sunlight will sprinkle on the particles like rain.(If the orbit is circular, the direction of sunlight is perpendicular to the direction of particle movement).But from the point of view of particles, for a moving particle, sunlight is radiated from the front (astronomers call itAberration）。
Therefore, the radiation pressure has a component opposite to the direction of motion of the particle orbit.Although the effect is small, it is continuous. The particle's orbital speed decreases, causing it to spiral down to the sun.This is the Poincare Robertson effect.
And it plays the role of vacuum cleaner in the solar system.This makes the mass of the solar system certain and will not decrease or increase.
Relationship between particle linearity and volume surface area
Other relevant knowledge
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Direct solar radiation andScattered radiationThe sum is calledTotal solar radiation。On the global average, the total solar radiation only accounts for 45% of the solar radiation reaching the upper boundary of the atmosphere.The total radiation decreases with latitude and increases with altitude.The maximum value is around noon and 0 at night in a day;Summer is big and winter is small in a year.
The solar radiation energy accounts for 50%, 43% and 7% of the visible light (0.4 ～ 0.76 μ m), infrared (>0.76 μ m) and ultraviolet (<0.4 μ m) respectively, that is, concentrated in the short wave band, so the solar radiation is called short wave radiation.
Solar radiation testIt is to evaluate the ability of outdoor unshielded equipment to withstand solar radiation heat and optical effects.
Solar radiation test standard:
GJB 150.7-86 Environmental Test Methods for Military Equipment Solar Radiation Test
GB 4797.4-1989 Natural Environmental Conditions for Electric and Electronic Products Solar Radiation and Temperature
At the beginning of this century, there are very few laboratories that can carry out solar radiation test. Beijing has an environmental reliability and electromagnetic compatibility test service center, and there are one in Shanghai and one in Guangzhou.
