降水回波谱参数估算雨滴谱参数的算法研究

Research of Retrieving Gamma parameters in Precipitation Cloud from Data Obtained of Vertical Radar

地基遥感雷达反演云中降水参数有助于认识降水云微物理过程,本文提出一种直接由垂直指向雷达回波谱参数估算雨滴谱参数的方法;当雨滴谱满足Gamma函数分布时,联合雷达气象方程、雨滴下降末速度与雨滴直径关系,建立雷达降水回波谱参数反演雨滴谱参数的方程组,采用隐函数显化和级数展开进行方程求解,得到雨滴谱参数估算结果。用正演方法建立检验数据库,使用平均相对误差平均值对近似求解的雨滴谱参数精度进行检验,截距参数为0.83%、斜率参数为3.04%、形状参数为13.60%。对2012年7月22-23日云南腾冲的1320 M Hz雷达垂直波束探测降水回波谱参数进行了雨滴谱参数估算,并与地面激光雨滴谱仪获取的雨滴谱参数进行了比较,两者的平均粒径基本相同。使用风廓线雷达等垂直探测雷达回波谱参数估算雨滴谱参数的方法适用于稳定层状降水云。

The data obtained from vertical radar can give better understanding of the microphysical processes inside precipitation cloud. A direct method of precipitation echo spectrum parameters estimate raindrop parameters is presented. Assumed the raindrop distribution is Gamma distribution,via radar meteorological equation,the relationship of raindrop terminal velocity and the diameter,exported the relationship of radar precipitation echo spectrum parameters and raindrop parameters. Using implicit functions explicit and series expansions to solve the equation,obtained approximate solution of the precipitation echo spectrum parameters estimate the raindrop parameters. Using forward method to establish testing database,verify the accuracy of approximate solution intercept parameter mean average relative error is 0. 83%,slope parameter mean average relative error is 3. 04%,and shape parameter mean average relative error is 13. 60%. Test results showthat the estimation method is feasible.Radar data of a precipitation event in Tengchong,Yunnan Province on 22- 23 July 2012 is used to estimate the raindrop size parameters,and compared with terrestrial laser spectrometer obtained average diameter of the results,the results relatively consistency. This method of retrieving Gamma parameters is suit for straitiform precipitation cloud.