一次冷涡减弱阶段产生的飑线过程分析

Analysis of a Squall Line Occurred with a Subdued Cold Vortex

冷涡背景下常常会产生强对流天气,分析发现在冷涡的不同发展阶段均会产生飑线过程,甚至在冷涡的减弱阶段也会产生,给预报带来很大的不确定性。为加深对冷涡减弱阶段产生的飑线过程的认识,提高此类飑线过程的预报能力,应用常规和非常规气象观测资料、雷达和卫星监测资料、NCEP/NCAR 1°×1°再分析资料、欧洲中心ERA-Interim再分析等资料对2009年7月23日冷涡减弱阶段发生在京津冀的一次长生命史飑线过程进行分析。重点分析了过程的大尺度系统配置、不稳定能量积累、中尺度演变特征,并探讨了对流的触发与飑线的组织化等。结果表明:在冷涡的减弱阶段,随着冷涡的南移,冷涡后部西北气流中活跃的短波槽东移引导冷空气侵入京津冀地区,配合低层暖湿舌形成良好的不稳定层结,入侵的冷空气伴随着西北风与西南气流相遇,在河北西北部地区形成地面辐合线,配合低层的高温高湿条件触发初始对流,随着925~500 hPa的垂直风切变的增强,对流逐渐组织化形成飑线。在高空西北气流引导飑线向东南方向移动,配合低层较好的水汽条件和热动力条件。在京津冀地区形成了不同类型的强对流天气。

Under the background of cold vortex,severe convection weather often occurs.It is found that the squall line process will occur in different development stages of cold vortex,and even in the weakening stage of cold vortex,which brings great uncertainty to the forecast.In order to deepen the understanding of squall line processes in the cold vortex weakening stage and improve the prediction ability of such squall line processes,basedon conventional and unconventional weather observation data,radar and satellite monitoring data,1°×1°NCEP/NCAR reanalysis data,the European center ERA-Interim reanalysis data,etc.This paperanalyzesthe data on July 23,2009 cold eddy weakening stage occurred in Beijing-Tianjin-Hebei process of a long history of squall line.The characteristics of large-scale system configuration,unstable energy accumulation and mesoscale evolution were analyzed,and the triggering of convection and the organization of squall line were discussed.The results show that in the weakening phase of the cold vortex,as the cold vortex moves to the south,the active short-wave trough in the northwest airflow behind the cold vortex moves to the east and leads the cold air to invade the Beijing-Tianjin-Hebei region.The invading cold air meets the southwest airflow with the northwest wind,and forms the surface convergence line in the northwest of Hebei province.With high temperature and humidity conditions,Initial convection has occurred.As the vertical wind shear of 925-500 hpa increased,the convection gradually organized into squall lines.In the upper northwest airstream guided the squall line to move southeast.With the lower level better water vapor conditions and thermodynamic conditions.There are different types of severe convective weather in the Beijing-Tianjin-Hebei region.