A RAPID RADIATIVE-TRANSFER MODEL FOR REFLECTION OF SOLAR-RADIATION

A rapid analytical radiative transfer model for reflection of solar ra diation in plane-parallel atmospheres is developed based on the Sobole v approach and the delta function transformation technique. A distinct advantage of this model over alternative two-stream solutions is that in addition to yielding the irradiance components, which turn out to be mathematically equivalent to the delta-Eddington approximation, the radiance field can also be expanded in a mathematically consistent fa shion. Tests with the model against a more precise multistream discret e ordinate model over a wide range of input parameters demonstrate tha t the new approximate method typically produces average radiance diffe rences of less than 5%, with worst average differences of approximatel y 10%-15%. By the same token, the computational speed of the new model is some tens to thousands times faster than that of the more precise model when its stream resolution is set to generate precise calculatio ns.