The selective absorption is carried through by some elements that form the atmosphere, the main ones and more significant absorvedores of energy are the oxygen, carbonic gas, ozone and vapor d? water. Such elements can not more than absorb or a type of energy wave that is radiated by the Sun, the ozone, for example, inside have an important paper of the atmospheric dynamics, therefore if it concentrates in the stratosphere forming the ozone layer, this layer has vital importance for the beings livings creature, therefore it absorbs the ultraviolet rays that are harmful the health human being. The clouds depending on its thickness, nature and altitude can attenuate the happened solar radiation of the Sun through the absorption or for the reflection. In general, the clouds absorb little energy, however it can reflect up to 90% of the solar rays, this phenomenon is common in days of great cloudiness where the rocking of solar radiation that arrives the terrestrial surface suffers considerable reduction. According to AYOADE (1986), the amount of energy radiated and incident in the top of the atmosphere can vary in elapsing of the year, sazonalmente or daily for intermediary of five determinative factors, being these divided in two groups, thus, in the first group has the period of the year, the latitude and the altitude of the Sun, and in as the group the distribution of the liquid and terrestrial surfaces, as well as, the rise and the aspect of the same ones. During the year the Land carries through an elliptical movement around the Sun with approach duration of 365 days, this movement is known as translation movement. For if dealing with elliptical circular movement, in the distance the ray of the movement enters and the center of reference of the rotation is modified in accordance with eccentricity reached for the body, such detail is basic for amount of radiation received for the Land, therefore, during the moment most eccentric in relation to the Sun (aphelion) the Land will receive minor intensity from energy, while, at the moment where he will be next to the Sun (perihelion) this will receive amount bigger from energy. .