Noel V, Ledanois G, Chepfer H, Flamant P H
Appl Opt. 2001 Aug 20;40(24):4365-75. doi: 10.1364/ao.40.004365.
The computation of the scattering properties of cirrus cloud ice crystals by the ray-tracing approach is described. A light beam is represented by its Stokes quadrivector I, which describes intensity as well as polarization, and the scattering properties of particles (molecules, droplets, or ice crystals) are introduced by means of a 4 x 4 transformation matrix M known as the Mueller matrix, or M matrix. Obtaining such a matrix for each kind of particle gives access to a complete description of the scattering medium. Most computations of the M matrices of cirrus ice crystals have introduced several simplifying hypotheses, by using basic shapes, by assuming a random orientation of the particles, or both. The present study focuses on the calculation of the complete M matrix for a specific shape of particles (i.e., hexagonally based crystals) either with optional oscillation about the horizontal plane or with random orientation. The validity of the computation code is checked against specific well-known cases for randomly oriented particles. For horizontally oscillating particles the computation of this matrix is a new result. Sensitivity of the M matrix to the following variables is studied: refractive index, amplitude of oscillation, particle shape and size, and angle of incidence.
描述了通过光线追踪方法计算卷云冰晶的散射特性。一束光由其斯托克斯四元向量I表示，它描述了光强以及偏振，粒子（分子、液滴或冰晶）的散射特性通过一个称为穆勒矩阵或M矩阵的4×4变换矩阵M来引入。为每种粒子获得这样一个矩阵可以完整描述散射介质。卷云冰晶M矩阵的大多数计算都引入了几个简化假设，例如使用基本形状、假设粒子随机取向或两者皆有。本研究重点在于计算特定形状粒子（即六边形晶体）的完整M矩阵，这些粒子要么在水平面附近有可选振荡，要么随机取向。针对随机取向粒子的特定已知情况检验了计算代码的有效性。对于水平振荡粒子，该矩阵的计算是一个新结果。研究了M矩阵对以下变量的敏感性：折射率、振荡幅度、粒子形状和大小以及入射角。
