Study on Sky Radiance Distribution

Part 2, Equation for the Relative Yearly Mean Sky Radiance Distribution

Abstract

A process of composing an equation of sky radiance distribution is shown in this paper. It has been proposed as an equation that expresses the relative yearly mean sky radiance distribution to the zenith radiance. The data gathered at the IDMP station of Kyushu University in 1994 and 1995 were applied. They were carefully inspected many times and refined as the basic data for formulation. After regression analyses were repeated several times, the equation was completed as a function of solar altitude, angular distance from the sun to the sky element and the altitude of the sky element.
The equation is not so complex. The difference between the basic data and the results obtained by the equation is rather small. This equation is considered to be applicable and useful for practical purposes.