摘要
利用四维变分同化分析系统模拟和雷达拼图资料分析了2012年5月16日东北冷涡影响下的弱飑线过程。结果表明:较强的地面辐合线是该次过程在较弱稳定条件下被触发的重要原因,也是系统前期快速发展的重要原因;东北冷涡影响下中层不断输送干冷空气到江淮地区,飑线内对流部分由降水拖曳导致的下沉气流遇到夹卷进入下沉气流内的环境干空气,使得其中雨滴蒸发造成空气冷却,下沉到地面形成冷池;冷池形成之后,垂直风切变方向不垂直于系统,且切变值较弱,造成水平涡度不平衡,是该飑线发展相对较弱的主要原因,此外不稳定条件和湿度条件较差也可能是系统没有发展为强飑线的原因。该次飑线过程的重要特点是较强的地面辐合线;较干的环境条件,意味着凝结潜热释放较少,而系统中的垂直运动更多取决于冷池和垂直风切变之间的水平涡度平衡。
Using four-dimensional variational Doppler radar assimilation system(VDRAS)simulation and radar mosaic data,a weak squall line influenced by northeast cold vortex on 16 May 2012 was analyzed.The result showed that strong convergence line on the surface was an important factor causing convective occurrence under the weak hydrostatic instability,and was also an important reason for the quickly developing of the system at the early stage.Cold air was continuously transported to Yangtze-Huaihe River Valley under the control of northeast cold vortex.Because of precipitation dragging by convection within squall line,the dry and cold air was entrained into convection and continuously moved downward,causing strong cold pool as the result of evaporation.The main reason for weak squall line is that after the formation of cool pool,vertical wind shear is not perpendicular to the squall line with weak magnitude,causing imbalance between them.Besides,weak hydrostatic instability and low relative humidity are part of reasons for the weak squall line.The major difference between this case and other squall lines in eastern China is the strong convergence line and relative dry environment,which means less moisture content is delivered to middle level and less latent heating is released.Finally,upward motion is more dependent on balance between cool pool and vertical wind shear.
作者
杨吉
郑媛媛
夏文梅
孙康远
YANG Ji;ZHENG Yuanyuan;XIA Wenmei;SUN Kangyuan(Key Laboratory of Transportation Meteorology,CMA,Nanjing 210009;Jiangsu Institute of Meteorological Sciences,Nanjing 210009;Nanjing Joint Institute for Atmospheric Sciences,Nanjing 210009)
出处
《气象》
CSCD
北大核心
2020年第3期357-366,共10页
Meteorological Monthly
基金
国家重点研发计划(2018YFC1507503)
国家自然科学基金项目(41805025、41575036、41475042)
江苏省社会发展面上项目(BE2015731)
江苏省气象局重点项目(KZ201704)
江苏省气象局面上项目(KM201701)
北极阁开放研究基金(NJCAR2016ZD01)共同资助。
关键词
飑线
东北冷涡
模拟
squall line
northeast cold vortex
simulation
