The energy of solar radiation reaching the upper boundary of the earth's atmosphere is called the amount of astronomical solar radiation. When the earth is located at the average distance between the sun and the earth, the total energy of solar radiation received by the unit area of the earth's upper boundary perpendicular to the sun's rays per unit time is called the solar constant. The common unit of solar constant is watts/meter². Due to different observation methods and techniques, the obtained solar constant values are different. The solar constant value is 1368 watts/meter 2. Solar radiation is a type of short-wave radiation.
The distribution of global annual total radiation reaching the surface is basically band-shaped, and is only destroyed in low latitudes. In the equatorial region, due to cloudy conditions, the total annual radiation is not the highest. In the subtropical high belt of the northern and southern hemispheres, especially in the desert regions of the mainland, the total annual radiation is relatively large, and the maximum value is in northeastern Africa. The distribution of solar radiation in the upper atmosphere is determined by the astronomical position of the earth, and is called astronomical radiation. The climate determined by astronomical radiation is called astronomical climate. The astronomical climate reflects the basic profile of the spatial distribution and temporal change of the global climate.
