Scattering matrices for large ice crystal particles

Abstract

The problem of light scattering by ice crystal particles whose sizes are essentially larger than the incident wavelength is divided into two parts. First, the scattered field is represented as a set of plane-parallel outgoing beams in the near zone of the particle. Then, in the far zone the scattered field is represented as a result of both diffraction and interference of these beams within the framework of physical optics. A proper ray-tracing algorithm for calculation of the amplitude (Jones) scattering matrix is developed and applied. For large particles, a number of reduced Mueller matrices are introduced and discussed, since the pure Mueller matrix obtained from the Jones matrix becomes a rather cumbersome and quickly oscillating value. Backscattering by hexagonal ice crystals, including polarization properties, is considered in detail.

Beam-splitting code for light scattering by ice crystal particles within geometric-optics approximation

“…Then del Guasta [6] developed a code named the facet tracing and applied it to calculate the backscatter by hexagonal ice crystals. Also the analogous codes were developed and used by Romashov [7], by Borovoi and Grishin [8] and by Borovoi et al [9]. Recently, the same beam-splitting code was considered by Bi et al [10] where the case of absorbing crystals was included as well.…”

On the Use of Scattering Kernels to Calculate Ice Cloud Bulk Optical Properties

“…These clouds also pose a challenge to atmospheric radiative transfer and remote sensing studies. As the optical properties of ice crystals are fundamental to quantifying the radiative properties of ice clouds, the atmospheric research community has made a significant effort to investigate the single-scattering properties of ice particles (Takano and Liou 1989a;Macke et al 1996;Yang and Liou 1996;Borovoi and Grishin 2003;Baran et al 2001;Baran 2004;Um and McFarquhar 2007;Zhang et al 2009). For practical applications to atmospheric radiative transfer and remote sensing involving ice clouds, the singlescattering properties (i.e., the phase matrix, singlescattering albedo, asymmetry factor, and extinction cross section) of individual ice crystals need to be integrated over particle size and shape distributions to derive the bulk optical properties (Ebert and Curry 1992;Fu 1996;Key et al 2002;McFarquhar et al 2002;Baum et al 2000Baum et al , 2005.…”

Backscattering reciprocity for large particles

“…In particular, we use the physical-optics approximation [6] to calculate light backscattering by hexagonal ice crystals of cirrus clouds. This reciprocity allows us to estimate a reliability of such calculations.…”

“…For such a large particle with the realvalued, for simplicity, refractive index, the scattered field inside the particle is easy found in geometric optics approximation by drawing ray trajectories. As a result, the scattered light leaves the particle after a number of internal reflections as a set of plane-parallel beams or ray bundles [6]. Every outgoing beam is determined on the particle surface by a number of parameters.…”

“…Then we have to determine light polarization in the j-th beam. It is described by the Jones matrix as the following product [6]:…”