We first introduce Wilfried Brutsaert’s contributions to atmospheric radiation in terms of his original work on deriving a simplified broadband emissivity for calculating downwelling long-wave radiation at the ground. This is followed by a discussion of sorting atmospheric absorption lines based on the concept of the correlated k-distribution approach, which can effectively be coupled with the multiple scattering processes of cloud and aerosol particles for spectral radiative flux calculations. Subsequently, a number of unsolved and challenging problems in radiative transfer are discussed, leading to the presentation of three-dimensional radiative transfer over inhomogeneous mountains/snow in conjunction with surface energy budget and within the context of absorbing aerosols and mountain/snow albedo feedback in a regional climate system.