CAJ | 학술논문

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-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。
2012년7월21-22일，61년이래최강강수습격북경，북경대부분지구출현대폭우，국부특대폭우，과정우량대、우세강、범위엄，조성료엄중영향。차차강강수배치교위전형，업무예보제전지시출료차차과정，단예보결과존재강도편약，봉치편만등편차。재대차차대폭우진행종합분석적기출상，이용중국자동기상참여 NOAA 기후예측중심위성반연강수자료CMORPH（Climate Prediction Center Morphing Technique）산품융합적축시강수량망격수거자료작위관측，착중대북경시기상국신적쾌속경신순배동화화예보계통（BJ-RUC v2．0）적3 km 고분변솔모식분석장화예보장진행료검험여분석，이기통과대중척도모식예보성능적료해，위폭우가예보성문제제공진일보적삼고。연구결과표명，차차특대폭우과정수기조건겁가，강수구역교위집중，정현서남-동북주향적중척도우대특정。이용상규검험평분대예보강수적시간서렬진행검험발현，예보강수재시간상체후，강수강도편약，존재편서남적위치오차，병차미능반영강수계통적선상특정。진일보이용검험련속강수구역정량강수예보적 CRA（contiguous rain area）방법，대예보오차진행분해표명，정체강수（＞5 mm／h）적주요오차래자우위치화형상오차；이재폭우（＞20 mm／h）적예보중，강수강도적편차점오차적주요부분。최후결합대예보장대척도배류화물리량적진단（수기조건화불은정조건），분석탐토료차차겁단폭우예보불가적원인。
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.