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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
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摘要: 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=1 m/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。Abstract: Measuring rainfall quantitatively is one of the main purposes of dual-linear polarization radar. The rain intensity can be derived from reflectivity ZH, differential reflectivity ZDR and specific differential phase KDP. The measurement accuracy of KDP is very important for deducing rainfall. The measurement accuracy of differential propagation phase shift ΦDP is calculated with various sample pairs M, range average intervals and spectrum widths σV by using theoretical formula. Then, the effect of those factors on the measurement errors of ΦDP is analyzed. Those results show that standard errors of ΦDP gradually decrease when the number of sample pairs M or range average interval increase, but standard errorsΦDP gradually increase withσV increasing (except in the case of σV=1 m/s). Moreover, three methods of obtaining KDP from ΦDP are summarized and the accuracy of those methods is compared. These results show that the errors of KDP produced by the second method are very large; the standard error of KDP can be less than 0.1o/km when using the first method and the third method on some conditions.
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表 1 不同的距离平均区间对σΦDP的影响
表 2 方法一和方法二计算KDP时产生的测量误差
表 3 方法三计算KDP时产生的测量误差
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[1] Sachidananda M, Zrnic D S. Differential propagation phase shift and rainfall rate estimation. Radio Sci., 1985, 20(2): 235～247. [2] Ryzhkov A, Zrnic D S. Assessment of rainfall measurement that uses specific differential phase. J. Appl. Meteor., 1996, 35: 2080～2090. [3] 楚荣忠,徐宝祥,贾伟,等. 双线偏振雷达测量精度的统计分析与降水估测. 高原气象, 1995,14(1): 47～54. http://www.cnki.com.cn/Article/CJFDTOTAL-GYQX501.005.htm [4] 刘黎平,钱永甫,王致君. 双线偏振雷达测量降雨效果的对比分析. 大气科学,1996,20(5):613～619. http://www.cnki.com.cn/Article/CJFDTOTAL-DQXK605.012.htm [5] 刘黎平,钱永甫,王致君.用双线偏振雷达研究云中粒子的相态和大小的空间分布.气象学报,1996,54(5):590-599. http://www.cnki.com.cn/Article/CJFDTOTAL-QXXB605.007.htm [6] Mueller E A. Calculation procedure for differential propagation phase shift. 22nd Conference on Radar Meteorology. Zurich, Switzerland. Boston, U.S.A.: American Meteorological Society, 1984. 397～399. [7] Sachidananda M, Zrnic D S. ZDR measurement considerations for a fast scan capability radar. Radio Sci., 1985, 20(4): 907～922. [8] 刘黎平,徐宝祥. 雨区衰减和雷达取样误差对713型双线偏振雷达测量精度的影响. 高原气象, 1989, 8(2): 181～188. http://www.cnki.com.cn/Article/CJFDTOTAL-GYQX198902013.htm [9] Ray P S, Zrnic D S, Doviak R. Time, angle and range averaging of radar echoes from distributed targets. J. Appl. Meteor., 1980, 19(3): 315～323. [10] Doviak R J, Zrnic D S. Doppler radar and weather observations. San Diego : Academic Press, Inc, 1993.154～155. -
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