Microwave backscattering by nonspherical ice particles at 5.6 GHz using second-order perturbation series

Scattering of microwaves by an ensemble of nonspherical ice particles is st udied using a scattering model based on a second-order perturbation series at 5.6 GHz (C-band). Particle shapes are defined using a Gaussian random sp here geometry. Particle inhomogeneity is taken into account using three dif ferent effective-medium approximations: Maxwell-Garnett, Bruggeman, and Coh erent Potential mixing rules, By systematically varying particle size, liqu id water content, Gaussian shape parameters, and internal structure, it is found that liquid water content is the most important factor for the co-pol arized backscattering; the shape is relatively unimportant, For depolarized backscattering, the shape is of fundamental importance, although the other factors are significant too. Surprisingly, the type of nonsphericity is fo und to be important for depolarization even for scatterers that are in the Rayleigh region: elongated targets depolarize clearly stronger than more ir regular shapes. This finding seems not to be strongly size dependent, at le ast for size parameters from 0.0059 to 0.47, and indicates that the accurat e modeling of shape is important for polarization quantities even in the Ra yleigh region. (C) 2001 Elsevier Science Ltd. All rights reserved.