Investigation of phase matrices of cirrus containing ensembles of oriented ice particles

Abstract

Experimental results of polarization laser sensing of cirrus with anomalous backscattering are presented. The technique of determining the optical and geometrical characteristics of clouds is described. Experimental data are compared with the meteorological conditions at altitudes of cirrus above the lidar location and with the results of numerical modeling of phase matrices in the approximation of physical optics. The recurrence frequency of meteorological characteristics of "mirror" cirrus is estimated.

Scanning polarization lidar LOSA-M3: opportunity for research of crystalline particle orientation in the ice clouds

“…The task of observations in lidar networks is to monitor the optical and microphysical properties of aerosol, which requires restoring not only the backscattering coefficient but also the lidar ratio and attenuation. Therefore, a large number of lidars are designed as aerosol-Raman (Althausen et al, 2000;Whiteman et al, 2007;Reichardt et al, 2012;Groß et al, 2015; Haarig et al, 2017;Madonna et al, 2018) or multiwave highspectral-resolution lidars (HSRLs; Eloranta, 2005;Burton et al, 2015). Most of these lidars use dichroic beam splitters as wavelength dividers, and polarizing elements (film po-larizers) are installed after the beam splitters and deflecting mirrors (Nott et al, 2012;McCullough et al, 2018).…”

“…In this case, the photodetectors change places with respect to the polarization components. Turning by 90 • can be carried out physically by rotating the entire photodetector unit (Yoshida et al, 2010;Strawbridge, 2013) or by rotating the half-wave phase plate, which can be installed both in the transmitter channel (Spinhirne et al, 1982) and the receiver (McGill et al, 2002;Reichardt et al, 2012). In previous lidars of the LOSA series (Balin et al, 2009), mechanical rotation of the photodetector unit by 90 • was used.…”

“…Starting from the works of Sassen (1977) and Platt et al (1978), numerous observations show that with a vertical orientation of the lidar, the horizontally oriented particles cause a specular reflection, manifested in the absence of depolarization and increased backscattering (Platt, 1978;Thomas et al, 1990;Sassen, 1991;Sassen and Benson, 2001). Data analysis of the polarization lidar in the CALIPSO experiment (Cho et al, 2008;Noel and Chepfer, 2010;Yoshida et al, 2010) shows that a significant fraction of horizontally oriented particles in the midlatitudes is observed in the temperature range from −35 to −5 • C. Deviation of the lidar from the vertical position eliminates the effect of mirror reflection.…”

“…It is obvious that the direction of preferential orientation is connected with the direction of action of these forces. The basis for such a conclusion is the observed non-invariance of the BSPM with respect to rotation of the coordinate system (Kaul, 2000;Kaul et al, 2004;Hayman et al, 2014;Samokhvalov et al, 2014). If we use linear polarized radiation and rotate the lidar around a vertical axis, signal energy depends on the angle of lidar rotation relative to the plane of preferential orientation of the particles if m 12 = 0 (Kokha-nenko et al, 2018).…”