基于SWAN系统的降水临近预报算法改进和应用评估  

Improving a precipitation nowcasting algorithm based on the SWAN system and related application assessment

作　　者：韩丰 唐文苑 周楚炫 盛杰 张小雯 HAN Feng;TANG Wenyuan;ZHOU Chuxuan;SHENG Jie;ZHANG Xiaowen(National Meteorolgical Centre,Beijing 100081,China)

机构地区：[1]国家气象中心,北京100081

出　　处：《气象学报》2023年第2期304-315,共12页Acta Meteorologica Sinica

基　　金：国家自然科学基金面上项目(42175001);中国气象局重点创新团队项目(CMA2022ZD07)。

摘　　要：为提升现有业务系统的降水临近预报(0—2 h)能力,以业务应用为目标,基于中国气象局强对流天气短时临近预报系统—SWAN(Severe Weather Automatic Nowcasting)开展降水临近预报算法改进和应用评估研究。首先使用分钟雨量数据,采用分雨团的雷达-雨量站降水订正技术,提高降水的实况订正频率,提升定量降水估计格点场的准确率;再通过基于光流法的回波运动矢量反演技术优化改进回波运动矢量;最终将改进后的定量降水估计格点场和外推矢量相结合进行降水临近预报。通过对2021年7月全国1 km分辨率回波和降水临近预报检验评估和个例分析发现:(1)改进的基于光流法的回波运动矢量反演技术可以捕捉不同天气尺度下的回波运动规律,反演结果具有较好的一致性和平滑性,可以提高外推的准确率。(2)新的降水临近预报子系统和现有SWAN系统相比,在0—1 h预报中,TS评分相对提高50%以上,Bias更趋近于1。在1—2 h预报中,除了20 mm/h的强降水以外,TS评分相对提升约20%,Bias下降1—3。新的降水临近预报子系统基于SWAN算法标准开发接口实现,运行效率满足业务需求,预报性能得到明显提升,具备业务应用的潜力。In order to improve the capability of precipitation nowcasting of the SWAN(Severe Weather Automatic Nowcasting)operational system,research on the improvement and evaluation of precipitation nowcasting algorithms is carried out,and a new QPF(Quantitative Precipitation Forecast)module is implemented.Firstly,minute rainfall observations are used to increase the frequency of QPE(Quantitative Precipitation Estimation)correction and a correction technology based on rain clusters is proposed to improve the rainfall field.The echo motion vector is then optimized by DIS(Dense Inverse Search)optical flow technology.Finally,precipitation nowcasting is produced by both the improved rainfall field and the optimized echo extrapolation vector.Through the national 1 km resolution echo and precipitation nowcasting test evaluation and case analysis in July 2021,it is found that:(1)The optimized echo motion vector based on DIS optical flow technology can capture different scales of echo motion.The results have better consistency and smoothness,which leads to an improvement of extrapolation.(2)Compared with the SWAN operational system,the TS score of the new QPF module is relatively improved by more than 50%in the 0—1 h forecast,and the bias is much closer to 1;in the 1—2 h forecast,except for heavy rainfall like that of 20 mm/h,the TS score increases by about 20%,and the bias decreases by 1—3.In summary,the proposed QPF module based on the SWAN algorithm development kit has significantly improved the forecast skill compared to the SWAN in both 0—1 h and 1—2 h leading time,and can be applied to operational nowcasting directly.

关 键 词：降水临近预报 分钟雨量 分雨团降水订正 光流法 

分 类 号：P435[天文地球—大气科学及气象学]