A meteorological model for rain-induced cross polarization

After a brief summary of the existing theory on microwave attenuation and cross polarization by rain and of the supporting experimental evidence, the paper gives a physical explanation of raindrop canting. It is shown that vertical wind gradients are a cause of canting. A model for the dependence of wind speed on height is employed to calculate actual values of canting angle and to investigate the dependence on wind gradients, height above terrain, and type of terrain. A generalization of the expressions for cross polarization as a function of raindrop canting angle is given which allows actual cross-polarization calculations to be made with the model. Results for sample cases on horizontal and slant paths are given to show the relative importance of various parameters.