On the relationship between direct and anisotropic diffuse radiation

•Relationship between the direct and anisotropic diffuse radiation.•A summation of a series of the solution for direct radiation.•2N-stream discrete ordinates method.

The relationship between the direct and anisotropic diffuse radiation for discrete ordinates method (DOM) is analyzed. The solution of anisotropic diffuse radiation can be expressed as a summation of a series of the solution for direct radiation in multi-stream DOM. A wide range of accuracy checks for anisotropic diffuse radiation of a homogeneous layer is performed with respect to the “exact” results computed from the δδ-128-stream scheme for radiative transfer. In addition, the results indicate that the increasing number of streams produces a decrease in error of reflection/transmission.