双低空急流对“21·7”河南极端暴雨的影响  

Impact of Double Low-Level Jets on the Extreme Rainstorm in Henan Province in July 2021

作　　者：马长健 李艳[1] 徐邦琪 MA Changjian;LI Yan;XU Bangqi(Key Laboratory of Meteorological Disaster of Ministry of Education(KLME)/Joint International Research Laboratory of Climate and Environment Change(ILCEC)/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters(CIC-FEMD),Nanjing University of Information Science&Technology,Nanjing 210044;State Key Laboratory of Severe Weather,Chinese Academy of Meteorological Sciences,Beijing 100081)

机构地区：[1]南京信息工程大学气象灾害教育部重点实验室(KLME)/气象与环境联合研究中心(ILCEC)/气象灾害预报预警与评估省部共建协同创新中心(CIC-FEMD),南京210044 [2]中国气象科学研究院灾害天气国家重点实验室,北京100081

出　　处：《大气科学》2023年第5期1611-1625,共15页Chinese Journal of Atmospheric Sciences

基　　金：灾害天气国家重点实验室开放课题2021LASW-A19;国家自然科学基金项目42375005。

摘　　要：利用全国自动气象站降水观测资料和欧洲中期预报中心(ECMWF)的ERA-5再分析资料,分析了2021年7月19~22日河南极端暴雨过程中双低空急流对降水的影响。结果表明,此次降水过程中,天气尺度低空急流(SLLJ)随低涡的发展自西南向东北移动,风向由东南风转为偏南风;边界层急流(BLJ)存在偏东向东南风的偏转,且其强度具有夜间强白天弱的日变化特征。降水过程存在两类耦合方式,第一阶段[19日20时(北京时,下同)至20日18时]为偏东风BLJ(E-BLJ)与东南风SLLJ(SE-SLLJ)的耦合形势,第二阶段(20日18时至22日08时)为东南风BLJ(SE-BLJ)与偏南风SLLJ(S-SLLJ)的耦合形势,降水均发生在BLJ的出口区和SLLJ的入口区。E-BLJ与SE-SLLJ耦合时,E-BLJ出口处的强辐合叠加山脉的动力抬升作用使降水区域对流层低层大气辐合,SLLJ入口区和天气尺度低涡系统使对流层中层大气辐散,为中尺度对流的发展提供了强有力的抬升触发机制。由于E-BLJ的范围较小、强度较弱,因此E-BLJ和SE-SLLJ的耦合作用相对较弱,降水主要受SLLJ的显著影响。SE-BLJ与S-SLLJ耦合时,SE-BLJ出口区的辐合与SLLJ入口区的辐散增强了对流层低层的上升运动,对流层中层的中尺度辐合与高空急流入口区右侧的辐散进一步增强了对流层中高层的上升运动。受双低空急流的共同影响,中尺度对流系统的强度和高度强烈发展,促进了强降水的发生。两种耦合方式下,双低空急流的水汽输送对强降水均具有重要作用,第一阶段SLLJ的水汽输送作用明显,而第二阶段BLJ的作用更加显著。The impact of the double low-level jets on the extreme rainstorm in Henan Province during 19–22 July 2021 is analyzed using precipitation data from the national automatic weather station of China and the ERA-5 reanalysis data from the European Centre for Medium-Range Weather Forecasts(ECMWF).The analysis shows that the SLLJ(synopticsystem-related low-level jet)moved from the southwest to the northeast with the development of the vortex,with the wind direction changing from southeast to southerly.The direction of the BLJ(boundary layer jet)changed from easterly to southeast and had a diurnal variation characterized by strong night-time and weak daytime intensities.There were two types of coupling modes during the precipitation process.During the first stage(from 2000 BJT 19 July to 1800 BJT 20 July),the coupling mode was that of the E-BLJ(easterly BLJ)and the SE-SLLJ(southeast SLLJ).During the second stage(from 1800 BJT 20 July to 0800 BJT 22 July),the coupling mode was that of the SE-BLJ(southeast BLJ)and the SSLLJ(southerly SLLJ).The precipitation occurred in the outlet of BLJ and the inlet of SLLJ.When E-BLJ and SE-SLLJ were coupled,the dynamic uplift of the strong convergence superimposed mountains at the outlet of E-BLJ converging with the lower troposphere in the precipitation zone,and the inlet of SLLJ and synoptic scale vortex system diverged the middle troposphere,providing a strong uplift trigger mechanism for the development of mesoscale convection.Owing to the small range and weak intensity of E-BLJ,the coupling between E-BLJ and SE-SLLJ was relatively weak,and the precipitation was significantly affected by SLLJ.When SE-BLJ and S-SLLJ were coupled,the convergence of the outlet of SE-BLJ and the divergence of the inlet of S-SLLJ enhanced the ascending motion of the lower troposphere,while the convergence of mesoscale in the middle troposphere and the divergence on the right side of the inlet of upper-level jet enhanced the ascending motion of the upper troposphere.Under the joint influence of the dou

关 键 词：极端暴雨 天气尺度低空急流 边界层急流 双低空急流耦合 

分 类 号：P442[天文地球—大气科学及气象学]