An Investigation of Light Scattering by Irregular Ice Crystals via PSTD

Abstract

We implement the Pseudo-Spectral Time Domain(PSTD) algorithm with Convolutional Perfect Matched Layer(CPML). Comparisons were conducted to test its performance with Mie's method. Results illustrate its good performance. More tests are still needed to determine the validity PSTD with CPML. We propose a random field model for surface irregularities of ice crystals with roughened surfaces. Results using this model show that reflection probability decreases exponentially as the roughness is increased linearly. We also apply a holographic Muller matrix imaging technique for roughened particle characterization within this model. Simulations indicate that even a small perturbation on the surface will result in quite different patterns using this holographic Muller matrix method. This imaging method may be useful for the cloud imaging and particle characterization. We also study the effects of volume irregularities, in the form of air bubbles, on the scattering properties of ice crystals. Results show that such volume inhomogeneity leads to phase functions smoothing and the reduction of backscattering in comparison with homogeneous cases. The distribution of air bubbles in ice crystals also has a significant influence on the phase function of inhomogeneous ice crystals.