Numerical evaluations in radiative transfer

Abstract

We compare different methods of calculating the monochromatic mean intensity and flux divergence for different dependences of the source function on the optical depth. We consider a semi-infinite plane-parallel atmosphere and a plane-parallel symmetric slab. We show that in some cases the methods commonly used are quite inaccurate, and propose another which gives consistent values for both the flux divergence and the mean intensity, even in extreme cases of high and small optical depths.