A Prototype Quantitative Precipitation Estimation Algorithm for Operational S-Band Polarimetric Radar Utilizing Specific Attenuation and Specific Differential Phase. Part I: Algorithm Description

摘要

A prototype quantitative precipitation estimate (QPE) algorithm that utilizes specific attenuation A and specific differential phase K-DP was developed for inclusion into the Multi-Radar Multi-Sensor (MRMS) system and the Weather Surveillance Radar-1988 Doppler (WSR-88D) network. Special attention is given to the optimization of the factor alpha used for computation of a path-integrated attenuation from a total span of differential phase along the propagation path in rain. It is suggested to estimate alpha from a slope of the Z(DR) dependence on Z in rain. The use of real-time adjusted alpha allows us to capture the variations of the drop size distributions, and therefore improve the QPE accuracy. It is demonstrated that the factor alpha is generally higher for tropical rain type compared to continental rain. Since the R(A) approach is only valid for pure rainfall, the R(K-DP) relation is suggested as a complement in areas of hail contamination. The paper contains a description of the basic version of the R(A) and R(K-DP) algorithm and recommendations for its further optimization.