A parameterization and generalization of backscatter functions for two-stream approximations

There has been a resurgence of interest regarding the climatic importance of aerosols. To assess the importance of aerosols, general circulation models (GCMs) should use the most appropriate two-stream solutions of the solar radiative transfer equation. For typical aerosol optical conditions, these solutions require exact backscatter functions which are computationally demanding. For this reason, they have been avoided by GCM modellers. In response to this, this note presents an efficient and accurate parameterization of the Henyey-Greenstein phase function's mono-directional backscatter function. In addition, a formula is supplied for the generalized backscatter function which bridges the gap between the mono-directional and the isotropic backscatter functions. (Author)