Albedo - pure number
For many applications involving terrestrial albedo, the albedo at a particular solar zenith angle θi can reasonably be approximated by the formula presented.
Directional-hemispherical reflectance is sometimes referred to as black-sky albedo and bi-hemispherical reflectance as white-sky albedo. These terms are important because they allow the albedo to be calculated for any given illumination conditions from a knowledge of the intrinsic properties of the surface.
|D||Diffuse illumination (dimensionless)|
|α_θ||Directional-hemispherical reflectance at that solar zenith angle (dimensionless)|
|α2||Bi-hemispherical reflectance (dimensionless)|