双线偏振多普勒天气雷达遥测降水强度和液态含水量的方法和精度研究

A Study of Method and Accuracy of Rainfall Rate and Liquid Water Content Measurements by Dual Linear Polarization Doppler Radar

利用雨滴谱的Γ分布和散射计算模式,研究了C波段双线偏振多普勒天气雷达遥测降水强度、液态含水量和识别降水粒子相态的方法,给出了利用反射率因子ZH、差分反射率因子ZDR、差传播相移KDP反演降水强度和液态含水量的三种公式以及这三个物理量的关系公式,并从雨滴谱的变化和雷达测量误差两方面比较了几种方法的测雨精度。结果表明:雨滴谱在很大范围变化时,利用ZDR和KDP可以很好地反演出降水强度和液态含水量,它受滴谱分布的影响不大,它的探测精度优于（ZH,ZDR）方法。单参数KDP方法优于传统的Z-R关系方法。同时给出的ZH与ZDR和KDP关系公式也基本不受雨滴谱变化的影响,它可以用于降水粒子相态的识别。双参数方法的测量误差主要来源于雷达测量ZDR和KDP的误差,特别是KDP的误差,改善KDP的测量误差是发挥双线偏振多普勒雷达探测降水强度或液态含水量潜力的关键。

The method and accuracy of rainfall rate (R) and liquid water content (M) measurements by dual linear polarization radar are analyzed by using aΓ drop size distribution (DSD) simulation and scattering calculation mode at 5.6 cm wavelength. Three estimators of rainfall rate and liquid water content with reflectivity ZH , differential reflectivity ZDR and specific differential phase KDP are presented,and the effects of variations of DSD and radar measurement errors on rainfall rate and liquid water content measurement are also analyzed. The results show that the estimators that use combined measurement ZDR and KDP are superior to the estimators of R and M obtained from ZH and ZDR, and the KDP method is better than conventional Z- R relationship method. The relationship between ZH and ZDR, and KDP is not sensitive to the variations of DSD, which could be used in distinguishing the solid precipitation from rain. Errors of dual-parameters estimators of R and M are mainly due to the measurement errors of ZDR and KDP. Improvement of KDP measurement is the key factor for the potential application of dual linear polarization radar.