Raindrop Size Distribution Retrieval From Dual-Frequency and Dual-Polarization Radar

Differential reflectivity from dual-polarization radars at frequencies such as S- and C-bands has been used to estimate the median drop diameter. Similarly, the dual-frequency ratio (DFR) can also be used to estimate median drop diameter. This paper presents an algorithm for estimating the raindrop size distribution parameters of median drop diameter (D₀) and equivalent intercept parameter (Nw) using a dual-polarization dual-frequency ground radar operating at Ku- and Ka-bands. The retrieval philosophy is based on combining attributes of the DFR, historically used in spaceborne radar systems and dual-polarization approaches used in ground radar algorithms. The estimator of D₀ as well as Nw (in the logarithmic scale) are evaluated using simulated radar observations in the presence of different error sources. It is shown that normalized bias and standard error for two estimators are both within ±2% and 16% when system noise is added. The situation when Ka-band observations are extinct during heavy precipitation is also considered.