多普勒雷达资料动态定量估测台风小时降水量的研究

在充分考虑传统的最优化方法和概率配对法优缺点的基础上,使用一种改进的最佳窗概率配对法计算Z-I关系中的系数A和b,得到了雷达测得的基本反射率因子Z和雨量计实时测到的小时降水量I的动态关系.利用温州多普勒雷达体扫资料和浙江省自动雨量站资料,使用该方法对"海棠"(Haitang)和"麦莎"(Matsa)两个台风分别进行了动态计算,得到了不同系数的Z-I关系,进而对两个台风的小时降水量进行了定量估测.使用变分技术对估测的小时降水量进行了校准.结果表明,不同台风Z-I关系的系数差别较大,因而造成台风小时降水量的很大不同.使用雷达基本反射率来估测台风小时降水量,能够清楚表现出台风的螺旋雨带和其中的中小尺度雨团,估测的台风小时降水量与实况基本接近.经过变分校准的估测降水量可以较好地表现出台风雨带与地面中尺度流场动力结构的对应关系.误差统计分析表明,变分校准后的估测台风小时降水量要明显好于变分校准前的估测台风小时降水量.变分校准法既保留了雷达估测台风小时降水量的分布特征,又使估测的台风小时降水雨量与实况的误差明显减小.

A STUDY ON VARIABLE QUANTITATIVE PRECIPITATION ESTIMATION USING DOPPLER RADAR DATA

With the pros and cons of the traditional optimization and probability pairing methods considered,an improved optimal pairing window probability technique is developed using a dynamic relationship typhoons.Such estimations are calibrated by variational techniques.The results show that there exist significant differences in Z-I relationships for different typhoons,leading to different typhoon precipitation efficiencies.The estimated typhoon precipitation by applying radar base reflectivity is capable of exhibiting evidently the spiral rain belts and mesoscale cells,and well matches the observed rainfall.Error statistical analyses indicate that the estimated typhoon precipitation calibrated is better than the one without variational between the base reflectivity Z observed by radar and real time precipitation I by rain-gauge.Then,the Doppler Radar observations of base reflectivity for typhoons Haitang and Matsa in Wenzhou are employed to establish variable Z-I relationship which is subsequently used to estimate hourly precipitation of the two calibration.The variational calibration technique is able to maintain the characteristics of distribution of radar estimated typhoon precipitation,and to significantly reduce the error of the estimated precipitation in comparison with the observed rainfall.