Correlation Properties of Differential Reflectivity and Their Implications for Radar Meteorology

摘要

This final report deals with the theoretical and experimental statistical properties of differential reflectivity, or Z(DR). The latter are based on the time series radar data obtained with the high resolution, 'fast' polarization switching Chilbolton radar system located in Southern England and operated by the Rutherford and Appleton Laboratories. An optimum estimator of Z(DR) is derived and comparisons of theoretically and experimentally obtained standard errors show excellent agreement. An examination of the effects of noise on the accuracy of Z(DR) measurements shows that signal-to-noise ratio of 20dB or greater is required to achieve high accuracy estimate of Z(DR). Time series radar data from England are used to determine the fluctuation spectrum (periodogram) of Z(DR) for the purpose of searching for signatures characteristic of polarization dependent backscattering processes such as drop vibration, canting, etc. A theoretical model of raindrops vibrating at their natural oscillation frequency (with no motion) is developed and the periodogram of Z(DR) is computed for comparison with measured data. (Author)