Depolarization ratios of single ice particles assuming finite circular cylinders.
Results of the depolarization ratio (delta) of single ice particles in fixed orientations are presented to determine whether discrimination between nonspherical ice crystals (causing depolarization) and spherical water droplets (inducing no depolarization) can be made. A T-matrix method is used to compute delta over a range of particle diameters from 0.13 to 4 microm and aspect ratios chi=d/h (d is the diameter and h the height of the particle) from 0.3 to 3, where ice crystals are assumed to have a circular cylindrical shape. The depolarization ratio is primarily dependent on the orientation of the particle. Some orientations return no depolarization, whereas others generate values reaching almost delta=1. Considering the depolarization averaged over all orientations, a dependence of delta with the particle size is observed where values close to 0.25 are reached. No strong influence of the aspect ratio on the depolarization for a given particle size of 2 mum is evident, as values remain in a range between 0.2 and 0.3.
Nicolet
Mathieu
M
Institute for Atmosphere and Climate, ETH Zurich, 8092 Zurich, Switzerland. mathieu.nicolet@env.ethz.ch
Stetzer
Olaf
O
Lohmann
Ulrike
U