华北“7·19”暴雨中低涡系统演变及多尺度相互作用机制研究  

A STUDY ON THE EVOLUTION OF VORTEX SYSTEM AND MULTI-SCALE INTERACTION MECHANISM DURING THE“7·19”RAINSTORM IN NORTH CHINA

作　　者：陈碧莹 闵锦忠[1,2] CHEN Bi-ying;MIN Jin-zhong(Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters,Nanjing University of Information Science&Technology,Nanjing 210044,China;Key Laboratory of Meteorological Disaster,Ministry of Education,Nanjing University of Information Science&Technology,Nanjing 210044,China;Hebei Meteorological Observatory,Shijiazhuang 050021,China)

机构地区：[1]南京信息工程大学气象灾害预报预警与评估协同创新中心,江苏南京210044 [2]南京信息工程大学气象灾害教育部重点实验室,江苏南京210044 [3]河北省气象台,河北石家庄050021

出　　处：《热带气象学报》2020年第1期85-96,共12页Journal of Tropical Meteorology

基　　金：国家重点基础研究发展计划项目(2017YFC1502103);国家自然科学基金重点项目(41430427);江苏省高校自然科学重大基础研究项目(11KJA170001)共同资助。

摘　　要：为探究华北暴雨的维持及中尺度系统演变机制,利用NCEP/NCAR的GFS资料、地面自动站观测资料等,借助数值模拟、涡度收支分析和尺度分离等方法,对2016年7月19日前后一次华北暴雨过程进行了观测分析和模拟研究。(1)本次极端降水过程与东移低槽切断形成的深厚低涡密切相关。低涡与副高脊线形成“东高西低”形势且雨区始终处于高层辐散低层辐合的动力配置下,有利于对流维持。涡旋与低空急流的配合使来自西南侧和东侧的水汽在华北辐合,并使雨区处于能量锋区,对流层中低层形成深厚逆温层,为暴雨维持提供水汽和能量保障。(2)低涡系统总体呈增强趋势,中心涡度最高达55×10-5 s-1以上。成熟阶段呈现贯穿对流层的直立正涡度柱,但涡度变化集中在500 hPa以下,中心维持在850 hPa附近。涡度增长主要受正涡度区与辐合中心重合产生的拉伸效应以及干侵入等因素的促进作用。(3)低层辐合中心由三种不同尺度系统叠加而成,其中中尺度系统对中心的强度和位置影响最大,而大中尺度风场间的辐合也使辐合区更大、强度更强。低层涡旋增长与风场辐合加强之间形成正反馈调节,有利于低涡和降水的维持。In order to explore the maintenance mechanism and mesoscale system characteristics of rainstorm in north China,a diagnostic analysis and simulation study on the torrential rain in north China around July 19,2016 has been carried out,using NCEP reanalysis data,regional observation data,etc.,and by means of numerical simulation,vorticity analysis and scale separation.The results are as follows.(1)This extreme precipitation is directly related to the deep vortex formed by the eastward moving trough.With the impact of both vortex and low-level jet,the water vapor from the southwest and east sides is converged in north China,the rain zone is near the energy front,and the deep inversion layer is formed in the lower troposphere,which provides water vapor and energy for the rainstorm.(2)The low vortex generally shows an increasing trend,and the central vorticity is up to 55×10-5 s-1.At the peak stage,it presents an upright positive vorticity column through the troposphere,but the vorticity changes are concentrated below 500 hPa and the center is maintained near 850 hPa.The vorticity increase is mainly affected by the stretching effect and the dry intrusion.(3)The low-level convergence center is a superposition of three scale systems.The mesoscale system has the greatest influence on the strength and position of the center,and the convergence between the large-scale and mesoscale wind also makes the convergence range larger and stronger.The positive feedback adjustment between the vortex growth and convergence enhancement is of great significance to the maintenance of the vortex system and precipitation.

关 键 词：特大暴雨 低涡结构 尺度分离 涡度收支 华北 

分 类 号：P426.62[天文地球—大气科学及气象学]