Solar radiative transfer in cirrus clouds. Part I: single-scattering and optical properties of hexagonal ice crystals

Abstract

We have developed an efficient light scattering and polarization program, based on a ray-tracing technique, for hexagonal ice crystals randomly and horizontally oriented in space. Computations of the scattering phase matrix are made from the observed ice crystal size distributions for four typical cirrus clouds. The results for single-scattering parameters, including the phase function, single-scattering albedo, extinction cross section, and asymmetry factor for five solar wavelengths, are presented and discussed. Light scattering computations are made for horizontally oriented columns and plates of various sizes. Results are used to interpret the optical phenomena produced by cirrus clouds. The present light scattering program for hexagonal columns and plates identifies the positions of halos and arcs, as well as providing relative intensities for these optical features. -from Authors