Microwave scattering in cirrus

Satellite retrievals of atmospheric parameters at microwave wavelengths require accurate modeling of absorptive and scattering processes. Many current models provide accurate results under the constraint that any scattering sources must be randomly-oriented. This is generally true of the bulk atmosphere, but dynamical simulations suggest that this does not hold for ice crystals in nonturbulent conditions. The Adding-Doubling method is able to account for nonuniform particle orientations, and a model was constructed to analyze cirrus clouds at several frequencies using varied ice crystal types and concentration profiles. These clouds were treated as plane-parallel, with changing particle concentrations, shapes, sizes, and orientations with respect to height. Phase functions for individual ice particles were predicted through the Discrete-Dipole Approximation. Since it is highly unlikely for particles in a cloud to possess identical phase functions, ensembles of various ice particles were considered. The orientation distribution's effect on polarized intensity, flux and brightness temperature measurements was then ascertained. Results are compared with equivalent isotropically-oriented particles using both the Adding-Doubling and Discrete Ordinate methods.