Some solar radiation ratios and their interpretations with regards to radiation transfer in the atmospher

Abstract

Ratios of some radiation fluxes such as global (total) solar radiation, H, direct solar radiation, H_b, diffuse solar radiation, H_d, and extraterrestrial radiation, H_o were proposed to define radiation coefficients related to radiation transfer in the atmosphere and solar radiation measurement on the ground surface. The irradiative transfer interpretations and applications in radiation measurement of the ratios were explained. Examples of such ratios are H/H_o and H_d/H. These are used to define the “clearness index” and “cloudiness index” of the atmosphere respectively, and are already in common knowledge and use. H/H_o and H_d/H for example, were found, from experimentation, to add up practically to unity, i.e. H/H_o + H_d/H =1. Based on this result, an empirical expression for predicting the direct solar radiation was developed in a previous work. Other ratios are H_b/H, H_b/H_o, H_d/H_o, Hr/H_o and sub>a/H_o. They were proposed to define relevant radiation coefficients, and were used to develop equations for estimating the reflection of the earth's surface and the absorption of the earth's atmosphere.

Keywords: solar radiation, radiation transfer, clearness index

Nigeria Journal of Pure and Applied Physics Vol. 4(1) 2005: 41-45