Extinction Matrix of Atmospheric Ice Crystals with Their Preferred Spatial Orientation for the Visible and IR Regions
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The extinction matrix for an ensemble of hexagonal ice plates and columns is presented. The extinction matrix for droxtal and bullet crystals has been estimated. The calculations have been carried out for particles with characteristic dimensions from 10 to 100 μm and wavelengths from 0.3 to 10 μm assuming a gamma distribution of particle size with a width parameter μ < 4. It has been found that the extinction matrix of an ensemble of atmospheric ice crystals in the visible wavelength region is a unit matrix with a coefficient equal to the doubled area of the particle projection. The error of this representation does not exceed tenths of a percent and does not depend on the type of crystals and their spatial orientation. It has also been found that such a representation of the extinction matrix in the IR region is possible only for hexagonal columns, bullets, and similar crystals with a characteristic size greater than 20 μm for wavelengths less than 8 μm.
Keywords:extinction coefficient extinction matrix cirrus clouds physical optics light scattering ice crystals
This work was supported by the Russian Foundation for Basic Research (project nos. 16-35-60 089, 18‑05-00568, and 18-55-53 046), President of the Russian Federation (grant no. MK-2495.2017.5), and Mendeleev Foundation of Tomsk State University. Calculations of the quasi-horizontally oriented column were supported by the Russian Science Foundation (agreement no. 18-77-10 035).
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