The relation between the orientation of particles in ice-crystal clouds and backscattering phase matrices (BSPMs) is considered. Parameters characterizing the predominant orientation of particles in the azimuthal direction and in the horizontal position are presented. The parameters are expressed through BSPM elements. A technique for measuring BSPM elements with lidar is described. Examples of some measurements are presented along with a statistical generalization of the results from more than 400 BSPM measurements. It is found that the orientation of coarse particles with large diameters in an azimuthal direction and in a horizontal position is more probable than in a random direction. However, the orientation of large particles is often masked by small particles that are not subject to the effect of orienting factors. Thus the mean parameters characterizing the state of orientation of particles in clouds as a whole correspond to weak orientation. It is supposed that the orientation of particles in the azimuthal direction is caused by wind-velocity pulsations.

In this paper we present results of investigation of the main optical properties of East Asian clouds with a ground-based polarization lidar placed in Daejeon, Republic of Korea. Asian dust is located in elevated layers of the atmosphere in spring, travels long distances, and causes significant damage to ecology. We present backscattering matrices of clouds obtained from polarimetric remote measurements which comprise information on the scattering and absorption properties of cloud particles, their morphology, and spatial orientation. Theory of our applied lidar polarization experiment is presented in terms of the instrumental vectors of a transmitter and a receiver. Methods of solving linear and nonlinear systems of equations comprising echo signals are considered. Some numerical and measurement results are presented to illustrate the efficiency and versatility of the method of estimating the cloud parameters.

The operation of an airborne lidar intended for the detection of fish schools is numerically simulated by the Monte Carlo method. The calculations are performed for schools located at small depths in order to study the regularities in the shaping of the lidar return accurately. Three models of the phase function of scattering of laser radiation in sea water are used. The signals reflected from surface waters that contain a school of fish are determined as a function of the lidar parameters, light scattering and absorption coefficients in the water, stratification of light scattering layers, and fish-school depth. The results obtained can be used for interpreting the signals of the fish-detection lidar.

Scattered light polarization serves as an indicator and a characteristic of various processes in the atmosphere. The polarization measurements of all scattering matrix elements provide an adequate description of the optical and morphological parameters and orientation of particles in clouds. In this article, we consider the problem of the calibration of matrix polarization lidar (MPL) parameters. Calibration by air is an effective alternative to the technique for correcting optical element parameters and among the calibration parameters of the MPL optical path are the relative transmission coefficient of a two-channel receiver, the angular positions of the transmission axes of the optical elements of the transmitter and receiver units, including the polarizers and wave plates, and the retardance of wave plates. For the first time, the method of calibration by air was partially implemented in the MPL to study Asian dust in the atmosphere. We considered the calibration problem more generally and this was due to the need to calibrate different MPL modifications from stationary to mobile ones. The calibration equations have been derived in terms of instrumental vectors, and the method of their solution by the generalized least squares method has been proposed. The method has been verified on a numerical MPL model and validated using MPL measurements in Daejeon, Republic of Korea.