Prospects for the measurement of ice cloud particle shape and orientation with elliptically polarized radar signals

A method to estimate cloud particle orientation and shape parameters using a polarization diversity radar is presented. The method is demonstrated for low-reflectivity ice clouds containing crystals that are modeled as prolate and oblate spheroids. The parameters to be estimated are the particle mean canting angle and the axis ratio in the incident wave polarization plane. The scattering matrix concept is used to obtain a relationship between two orthogonally polarized received powers and the parameters of interest. It is shown that the use of an elliptically polarized radar signal diminishes the expected difference between received powers in the two receiving polarization channels. This makes polarization studies of ice clouds with relatively low reflectivities possible; these clouds often are "invisible" in one of the receiving channels when conventional linear or circular polarization is used. An estimation of errors in the retrieved mean canting angle value caused by the spread in particle orientation is also given.