Fluctuations of Differential Phase and Radar Measurements of Precipitation

Abstract

The specific differential polarization phase shift KDP has been suggested as a possible estimator of rainfall as well as a rain-hail discriminator in several recent studies. Here, the complex multivariate Gaussian model, used widely in communication theory and statistics optics, is applied for modeling KDP caused by precipitation. Specifically, the width of the marginal phase probability density function is used to estimate ?DP (cumulative differential phase) fluctuations. This results in suboptimal but simple expressions, which highlight the dependence of ?DP fluctuations on the magnitude of the HV (horizontal?vertical) cross-correlation coefficient |?HV|. Statistical arguments are separated from the effects of radar wavelength and Doppler spread. Implications of ?DP fluctuations on accuracy of rainfall and snow/hail radar measurements are also discussed and the author comments on the feasibility of using cross-polarized differential phase measurements.