RADAR QUANTITATIVE PRECIPITATION ESTIMATION TECHNIQUES AND EFFECT EVALUATION
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摘要: 为提高雷达定量估测降水的精度,利用广东省6部新一代多普勒天气雷达(CINRAD/SA)回波资料和雨量计降水量观测资料,采用概率配对法(PFT,Probability-fitting technique)建立Z-I关系进行单部雷达降水估测,并采用最优插值法(OI,Optimum Interpolation)对降水估计进行订正;为扩大降水估测的范围,对多部雷达的降水估计进行拼接,采取重叠区域以各部雷达的均方根误差平方的倒数作为权重系数(tu)进行加权平均,并分别分析比较上述方法得到的降水估计与单纯OI雨量计及与雷达拼图回波强度得到的降水估计的优劣。以上各环节误差分析表明,对于单部雷达,雨量计降水强度与其上空9点平均的雷达回波强度关系最为密切;6部相同型号的雷达估测降水精度各异。交叉检验表明,OI雷达法对单部和多部雷达估测降水均可取得较好的校准效果;对于多部雷达的降水估测,单部雷达先分别进行OI订正后拼接,然后对重叠区再次OI订正的结果比直接对未订正的单部雷达降水估计拼接后统一做一次OI订正的效果好。多部雷达降水估计拼接时,前期对于单部雷达降水估计的订正尤为重要;多部雷达降水估计的拼接值精度要明显高于OI雨量计,而相比由雷达拼图回波强度得到的降水估计而言,前者也优于后者。因此,多部雷达降水估计的拼接方法,对雷达资料的应用有较好的参考价值,在业务上也有一定的应用前景。Abstract: This research work is aimed at improving the radar QPE (Quantitative Precipitation Estimation) techniques. Based on CINRAD/SA dataset of volume scan reflectivity and rain gauge data in the Guangdong area, the probability-fitting technique (PFT), which is adopted to localize the relationship between Z and I, and the OI (Optimum Interpolation) method, which is used to correct the radar precipitation estimation, have been used. In order to estimate large scale precipitation, multi-radar QPE was combined by weighting each radar by square multiplicative inverse (tu)of its RMSE (root mean square error). Error statistical analyses indicated that station gauge rain is most closely related to the average of nine point's reflectivity above. Additionally, it was verified that the QPE precision of each single-Doppler radar with the same model is different; As for the multi-radar QPE,the result of OI combination of corrected value of single-radar precipitation estimation is better than that of OI combination of single-radar precipitation estimation. Trough cross-validation, some conclusions were obtained that the OI correction method can minimize the precipitation estimation errors to a certain extent and correcting single radar precipitation estimation in advance is important. It was also shown that the method of multi-radar QPE combination is better than gauge's OI. Against the radar composite image hybrid reflectivity QPE, the precision of the former is higher than the latter. So, multi-radar QPE combination techniques have some reference value for application of radar data and have application prospective in operational weather services.
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