Theoretical investigation of the extinction and absorption coefficients of a system of oriented ice plates in optical plane range

Abstract

The report presents a theoretical and numerical investigation of extinction and absorption coefficients as well as the single scattering albedo for polydispersed ensemble of plate-shaped crystals. We analyze a value of the efficiency factor for optical radiation in large crystals. It is shown that in the IR range only for crystals with the plane faces, inclined to each other at an angle more than 10 to 12 degrees, the efficiency factor can be assumed to be equal to 2. Analytical expressions for the coefficients of optical radiation extinction and absorption for ice plates are derived in the approximation of physical optics. The formula for extinction explains both the neutral spectral behavior of the extinction coefficient in the visible range and its wavelength dependence in IR range. Computed wavelength dependence of extinction coefficient has a fine structure and carries certain indicators of the ice plate size. The presented formula for calculating of the absorption coefficient estimates optical radiation intensity being absorbed by atmospheric crystals of any shapes. It is shown that spectral absorption dependence in the IR range has the same features as the dependence of absorption index for ice and ranges up to values comparable to those typical of scattering coefficients. Single scattering albedo is shown to be equal to unity in the visible range, while in the IR range it varies from 0.5 to 0.8.