&lt;title&gt;Parameterization of basic optical radiation scattering properties of ice crystal particles&lt;/title&gt;

Alexander G Petrushin

doi:10.1117/12.617512

Abstract

With the use of the expressions obtained by us earlier the extinction efficiency Kex, absorption efficiency Ka, single scattering albedo A and phase scattering function P(θ)/4π for optical radiation of a crystalline cloud medium were calculated. The optical characteristics mentioned are necessary for calculation of crystalline and mixed-phase clouds radiation properties used in different climate models. The crystalline cloud microstructure model included the ice hexagonal plates and columns cna be arbitrarily oriented in space. Two possible cases of ice crystal orientation in space were considered -- a chaotic orientation and an arbitrary orientation of the prisms main axis and the plates maximum surfaces in the horizontal plane. The hexagonal prism shape factor is c = 2a/l (where 2a is prism diameter and l is its length), 0.05 ≤ c ≤ 10.0. Theoretically estimated values of Kex for a crystalline medium microstructure were compared with the experimental values Kex obtained at the IEM. For execution of Ke calculations by hexagonal prisms with a chaotic orientation in space which sizes are comparable with wavelength of incident radiation can be used Mie-Lorentz theory for spherical particles with the same refractive index and effective radius R32. The absorption efficiency Ka by hexagonal prisms with different orientation in space can be calculated using with the suggested expressions for Ka in view effective size R32. For small (diffraction) scattering angles the phase scattering function P(θ)/4π for ice crystals which sizes are more than wavelength with the high precision may be described by the phase scattering function P(θ)/4π for spherical particles with the effective radius R2 the same as the effective size R2 for ice crystals.

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