What are the effects of various substances in the Earth’s atmosphere on solar radiation?


Oxygen, ozone, water, carbon dioxide and dust in the atmosphere have different absorption effects on solar radiation. Among them: the content of oxygen in the atmosphere is about 21%, and it mainly absorbs the solar radiation band with a wavelength less than 0.2um, especially for the radiation band of 0.1554m, which has the strongest absorption ability, so it is difficult to find solar radiation less than 0.24m in the lower atmosphere; ozone mainly absorbs ultraviolet rays, and the energy it absorbs accounts for about 21% of the total solar radiation energy; if there is more water vapor in the atmosphere and the position of the sun is not too high, water vapor can absorb 20% of the total solar radiation energy, and liquid water absorbs more solar radiation energy; carbon dioxide and dust absorb less solar radiation energy.

Large particles such as water molecules, small water droplets and dust in the atmosphere reflect solar radiation. Their reflective power accounts for about 7% of the average solar constant. Clouds are especially reflective. However, the reflectivity of clouds is related to cloud amount, cloud shape and cloud thickness. The 3000m thick altocumulus cloud has a reflective ability of 72%, and the cumulus layer has a reflective ability of 52%. According to calculations, based on the average cloud cover of the earth is 54%, about 1/4 of the solar radiation energy is reflected back to the universe by the clouds.

When the solar radiation hits the earth’s atmosphere as a parallel beam, it encounters the blocking of air molecules, dust and clouds and other particles to produce scattering. This kind of scattering is different from absorption. It does not convert the solar radiation energy into the internal energy of each particle, but can only change the direction of the solar radiation, so that the solar radiation transmits energy in all directions on the particle, so that part of the solar radiation becomes the reverse radiation of the atmosphere, which is emitted outside the earth’s atmosphere and cannot reach the earth’s surface. This is an important reason for the weakening of solar radiation energy.

Due to the existence and influence of the atmosphere, the solar radiation energy reaching the earth’s surface can be divided into two parts, one part is called direct radiation, the other part is called scattered radiation, and the sum of these two parts is called total radiation. The part of the sun’s rays that hits the ground directly is called direct radiation. It is not directly projected on the ground, but the part of the sun’s light that reaches the ground through scattering in different directions by the atmosphere, clouds, fog, water droplets, dust and other objects is called scattered radiation. The energies of these two types of radiation are very different. Generally speaking, direct radiation accounts for the majority of the total radiation during the clear day, scattered radiation accounts for the majority of the total radiation on cloudy and rainy days, and completely scattered radiation at night. The use of solar energy is actually the use of the total radiation of the sun. However, for most solar equipment, it is mainly the direct radiation part of the solar radiation energy.

In short, the total radiant energy emitted by the sun is about 3.75×1026W, which is incomparable energy.

But only one in 2.2 billion reaches Earth. The total solar radiation energy reaching the earth is about 173×104 billion kilowatts. Among them: the solar radiation energy absorbed by the atmosphere is about 40 × 104 billion kilowatts, accounting for 23% of the total solar radiation energy reaching the earth; the solar radiation energy reflected back to space by atmospheric molecules and dust particles is about 52×104 billion kilowatts, accounting for 30%; the solar radiation energy reaching the earth’s surface through the atmosphere is about 81×104 billion kilowatts, accounting for 47%; among the solar radiation energy reaching the earth’s surface, the one reaching the earth’s land surface is about 17×104 billion kilowatts, accounting for about 10% of the total solar radiation energy reaching the earth. What is the magnitude of the 17×104 billion kilowatts reaching the earth’s land surface? Figuratively speaking, it is equivalent to more than 35,000 times the total energy produced by various energy sources consumed in the world in one year.