A Technique to Improve Copolar Correlation Coefficient Estimation

Copolar correlation coefficient is one of the essential polarimetric variables because it enhances the ability of weather radars to discriminate among different hydrometeor types as well as nonmeteorological scatterers. Theoretical values of the copolar correlation coefficient (|ρ hv (0)|) are between zero and one, but due to statistical errors, estimates of |ρ hv (0)| can take values that are outside this interval, in which case the estimates are deemed unusable. Additionally, even if a |ρ hv (0)| estimate is valid, it can introduce errors in echo classification if not sufficiently accurate. Therefore, it is imperative to keep the number of invalid estimates at a minimum while maintaining the acceptable accuracy and precision of measurements. Herein, a technique to improve copolar correlation coefficient estimation is presented. The technique produces estimates with reduced bias which results in an increased number of valid estimates as well as improved accuracy of |ρ hv (0)| fields. This is achieved through a combination of previously proposed |ρ hv (0)| estimators with several novel estimators presented in this paper.