双线偏振多普勒雷达测量精度的理论分析

THEORETICAL ANALYSIS OF MEASUREMENT ACCURENCY OF DUAL LINEAR POLARIZATION DOPPLER RADAR

双线偏振雷达的主要任务之一是定量测量降水 ,反射率因子ZH、差反射率因子ZDR、差相移率常数KDP都可以用来反演降雨强度 ,而KDP的测量误差大小是影响反演降雨强度效果的关键。本文从理论公式出发 ,计算和分析了不同方位平均、距离平均、不同谱宽σV等因素对差传播相移ΦDP测量精度的影响。理论计算结果表明 :ΦDP的测量误差随着样本对数M、距离平均区间的增大而减小 ,随σV 的增大而增大 (σV=1m/s时例外 ) ,此外 ,还总结了 3种由ΦDP计算KDP的方法 ,并对这 3种方法的测量误差进行了比较 ,发现方法二的测量误差很大 ,方法一和方法三在一定的条件下都能使KDP测量精度达到 0 .1°/km。

Measuring rainfall quantitatively is one of the main purposes of dual linear polarization radar. The rain intensity can be derived from reflectivity Z H , differential reflectivity Z DR and specific differential phase K DP . The measurement accuracy of K DP is very important for deducing rainfall. The measurement accuracy of differential propagation phase shift Φ DP is calculated with various sample pairs M , range average intervals and spectrum widths σ V by using theoretical formula. Then,the effect of those factors on the measurement errors of Φ DP is analyzed. Those results show that standard errors of Φ DP gradually decrease when the number of sample pairs M or range average interval increase,but standard errors of Φ DP gradually increase with σ V increasing (except in the case of σ V=1 m/s). Moreover,three methods of obtaining K DP from Φ DP are summarized and the accuracy of those methods is compared. These results show that the errors of K DP produced by the second method are very large; the standard error of K DP can be less than 0.1°/km when using the first method and the third method on some conditions.