相似廓线法在星载雷达陆面衰减订正中的应用

Application of Similar Profile Method in Attenuation Correction of Single-Frequency Satellite-Borne Radar over Land

针对星载雷达陆面衰减订正存在的困难,提出相似廓线订正方法。利用洋面雷达测得的雷达等效反射率因子廓线(简称降水廓线) Zm和经表面参考技术(SRT)订正后的降水廓线Ze建立相似廓线库,通过匹配雷达在洋面和陆面测得的降水廓线,对陆面降水廓线的地表路径积分总衰减(PIAs)进行估值。借助2018年GPMCO2A-Ku数据产品中洋面降水资料进行检验,结果表明相似廓线法与SRT技术的订正结果具有较好的一致性,对于容许相对偏差40%的相似廓线库,匹配成功的降水廓线中,两种方法的PIAs相对偏差小于40%的廓线比例依次为对流云降水88.8%,无亮带层状云降水98.9%,含亮带层状云降水98.9%,显示该方法有效。借助2014-2018年GPM-CO2A-Ku数据产品中陆面降水资料进行对比,结果表明相似廓线法的陆面应用效果与洋面差异较大,与陆面SRT技术应用效果差的结论相一致。

In view of the difficulty in estimating the path-integrated attenuation(PIA) of rain attenuation over land using GPM-CO Ku data, we propose similar profile method. Using the radar profiles of rainfall over sea and the SRT-corrected radar profiles of rainfall, the profiles database is established with a certain precision to estimate the PIA over land by means of matching profiles over land with those in the database. Applications of the method to measurements for 2018 from the DPR of Ku band suggest that it performs well over the ocean. With 40% margin of error, the percentage of successful applications for convective rain is 88.8%, and it is 98.9% for both stratiform rain with and in the absence of a detectable bright band. In terms of rainfall from 2014 to 2018 over land, the result of using the similarity profile method is different from the rainfall over ocean, which is consistent with the poor performance of the SRT-corrected mothed over land.