摘要
2012年7月21-22日,61年以来最强降水袭击北京,北京大部分地区出现大暴雨,局部特大暴雨,过程雨量大、雨势强、范围广,造成了严重影响。此次强降水配置较为典型,业务预报提前指示出了此次过程,但预报结果存在强度偏弱,峰值偏晚等偏差。在对此次大暴雨进行综合分析的基础上,利用中国自动气象站与NOAA气候预测中心卫星反演降水资料CMORPH(Climate Prediction Center Morphing Technique)产品融合的逐时降水量网格数据资料作为观测,着重对北京市气象局新的快速更新循环同化和预报系统(BJ-RUC v2.0)的3 km高分辨率模式分析场和预报场进行了检验与分析,以期通过对中尺度模式预报性能的了解,为暴雨可预报性问题提供进一步的参考。研究结果表明,此次特大暴雨过程水汽条件极佳,降水区域较为集中,呈现西南一东北走向的中尺度雨带特征。利用常规检验评分对预报降水的时间序列进行检验发现,预报降水在时间上滞后,降水强度偏弱,存在偏西南的位置误差,并且未能反映降水系统的线状特征。进一步利用检验连续降水区域定量降水预报的CRA(contiguous rain area)方法,对预报误差进行分解表明,整体降水(>5 mm/h)的主要误差来自于位置和形状误差;而在暴雨(>20 mm/h)的预报中,降水强度的偏差占误差的主要部分。最后结合对预报场大尺度环流和物理量的诊断(水汽条件和不稳定条件),分析探讨了此次极端暴雨预报不佳的原因。
The heaviest rainfall over 61 years hit Beijing on 21-22 July 2012.Characterized by its great rainfall amount and in-tensity,wide range,and high impact,this record-breaking severe rainfall caused dozens of deaths and extensive damage.De-spite seeming typical in terms of synoptic conditions,the operational forecasts underestimated the precipitation amount and were later as to predicting the rainfall start time.To gain a better understanding of the performance of mesoscale models,veri-fication of high-resolution forecasts and analyses from the WRF-based BJ-RUC v2.0 model with a horizontal grid spacing of 3 km is carried out.The results show that in this case water vapor is very rich and a quasi-linear precipitation system produces a rather concentrated rain area.Moreover,the model forecasts are first verified by using statistically the Equitable Threat Score （ETS）and BIAS score.The BJ-RUC v2.0 forecasts under-predict the rainfall with a southwestward displacement error and time delay of the extreme precipitation.Further quantitative analysis of the contiguous rain area （CRA）method indicates that major forecast errors for total precipitation （〉5 mm/h）are due to inaccurate precipitation location and pattern,while forecast errors for severe rain （〉20 mm/h）mainly come from precipitation intensity forecasts.Finally,the possible causes for the poor performance are discussed through diagnosing large-scale circulation and physical parameters （water vapor condition and insta-bility conditions）based on the BJ-RUC v2.0 model outputs.
出处
《气象学报》
CAS
CSCD
北大核心
2014年第2期207-219,共13页
Acta Meteorologica Sinica
基金
国家重点研究发展计划973项目(2013CB430106)
公益性行业(气象)科研专项(GYHY201206005)
国家自然科学基金项目(41175087)
国家人才培养基金(J1103410)
关键词
特大暴雨
降水检验
中尺度模式
暴雨预报
Excessive rainfall, Precipitation verification, Mesoscale model, Torrential rain forecast
