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The information borne by the characteristics of reflected optical radiation in the cases of single- or double-ended lidar is studied within the framework of a crystal cloud model as a system of oriented crystal plates. It is shown that the variation of the absolute and relative values of the scattering coefficient obtained at small-angle scanning carries the information about the size spectrum of crystal plates and their flutter in atmospheric formations with inhomogeneous composition.

The large potential opportunities in study of the top and average atmosphere can be realized at remote sensing through a use of the bistatic polarization scanning lidar. In the report, a process of scattering of polarization radiation by crystalline cloud to bistatic technique of sensing is investigated. The translucent plate crystal, as an object of study of scattered radiation on a separate particle is considered. The choice of such model is caused in the report. There are obtained the expressions for scattering cross sections within the physical optics formalism. As a result of the numerical analysis the regular dependences of depolarization ratio and ratios of parameters of Stokes vector on the orientation angle of plate with respect to the sensing direction, the orientation of the polarization plane, the refractive index of plate have been established. It is arrived the obviously expressed dependence of scattering cross section from plate radii.

The crystal clouds extend above a mostly surface of the Earth. Their structure is submitted by a huge variety of forms and sizes ofparticles. According to conditions of crystal growth, one or other kind of particles prevails in a cloud'. The particles of the extended form such as polyhedrons, needles, plates were observed in all atmospheric formations essentially. The character of movement of particles in quiet layers of an atmosphere is caused by their aerodynamic properties and gravitational forces. Plate crystals are more tolerant on position in space among the extended formed particles. A behaviour of atmospheric particles depends on character of movement of airflow. The reorientation of each crystal will be determined by a difference of vectors of speed of its fall and speed of movement of a wind. All powerful fields influence on a circulation of airflow. A deep heterogeneity of the Earth, a breaks of geological structures, a fluctuation in magneticsphere, a electrical field influence on formation of atmospheric structure. As a rule, the presence of a powerful field is favourable to a steady position of particles in space. The numerous investigations have shown, that the ice clouds in the greater part consist of systems of particles of some primary orientation. The mechanism of light scattering on such crystals differs appreciably from scattering on spheres or chaotic oriented particles. Feature of light scattering by nonspherical particles is obviosly expressed anisotropy. It is possible to observe a anomalous optical phenomena in an atmosphere, as a consequence of radiation scattering on preferred oriented crystals.

A polarization backscattering phase matrix for oriented semitransparent plates is given in the present paper. The matrix elements have been numerically investigated. Regular dependences have been established of the matrix elements on the orientation angle of particles with respect to the sensing direction, the orientation angle of the polarization plane, and the refractive index of particles. An algorithm has been developed for determining the refractive index and the orientation angle of ice plates from the data of polarization lidar sensing for two-angle sensing geometry. A formula has been derived that relates the main parameters of the medium with the backscattering coefficient that can be used for interpretation of highly intense lidar return signal.

An approximate analytic expression for the coefficient of optical extinction by a polydisperse plate crystal system is derived within the framework of physical optics. Numerical investigations of the extinction coefficient of a system of oriented ice plates in optical plane range is represented in the paper. Each wavelength dependence of extinction has a certain specific feature, which may be used to estimate the average size of the ice plates. It is shown that oriented ice plates can cause a noticeable wavelength dependence of the extinction coefficient of a crystal cloud.

An attempt to interpret backscattering phase matrices of cirrus clouds measured with a ground-based lidar is undertaken in this paper based on a theoretical model of interaction between optical radiation and an ensemble of flaked crystals. Deviations of the diagonal elements from unity indicated that partides orientation differed from the horizontal one and the crystals had a prefered orientation at some angle with respect to the direction of sounding. Keywords: backscattering phase matrices, cirrus douds, lidar

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.