ABSTRACT
Radiant energy emitted by the sun supplies virtually all the energy for natural processes on the surface of the Earth and its atmosphere. Since atmospheric properties vary with height in a quasi-regular manner, it is convenient to describe the atmosphere in terms of a series of geocentric layers or shells, which, of course display both geographic and seasonal variabilities. Principal properties used to define these layers are temperature, pressure, and atmospheric composition. Upon entry into the Earth's atmosphere, the constant extraterrestrial solar radiation undergoes absorption and scattering interactions with atmospheric components. Atmospheric ozone does not rival the domination of nitrogen, oxygen, and aerosols in atmospheric scattering and absorption in the visible wavelength region of the electromagnetic spectrum. However, play a major role as a screening agent for the biologically-pernicious ultraviolet wavelength region of the solar spectrum. Since the incident irradiance is a composite of direct solar and diffuse sky irradiances, however, care must be exercised in treating them separately.
