ABSTRACT
Solar radiation incident on vertical and inclined surfaces consists of beam, sky-diffuse and ground-reflected components. The ground-reflected component may be significant, particularly in the northern latitudes due to low elevations of the sun and, at times, due to the presence of highly-reflecting snow cover. Accurate estimation of ground-reflected radiation would require knowledge of the foreground type and geometry, its reflectivity, degree of isotropy, the details of the surrounding skyline and the condition of the sky. Little information is available on the interaction of these parameters. The usual approach is to take a constant value of ground reflectance of 0.2 for temperate and humid tropical localities and 0.5 for dry tropical localities (CIBSE, 1982). This is despite the fact that the reflectivity of snow-covered ground could be as high as 0.9.
