EFFECTS OF AEROSOLS ON THE WAVELENGTH DEPENDENCE OF ATMOSPHERIC TRANSMISSION IN THE ULTRAVIOLET AND VISIBLE - 1 - A SINGLE-SCATTERING-SEPARATE DELTA-EDDINGTON MODEL

A modification to the conventional delta-Eddington radiative transfer scheme was implemented in order to create a simple and efficient model particularly suitable for handling the highly anisotropic scattering properties exhibited by cloud drops and aerosol particles in the atmos phere. The modification includes separating out the singly scattered r adiation and applying the conventional Eddington approximation to the multiply scattered radiation alone. The singly scattered irradiance is computed analytically without approximation, preserving more of the a ngular dependence in the radiance than conventional two-stream style s olutions. The single-scattering-separate delta-Eddington model was fou nd to handle strong absorption in the stratosphere and the anisotropic scattering within optically thin cloud layers better than both the si mple two-stream and conventional Eddington models, and to produce resu lts similar to a 22-stream discrete ordinates model.