一次西南低涡暴雨过程的诊断分析与数值模拟  

Diagnostic Analysis and Numerical Simulation of a Torrential Rainstorm Process Caused Southwestern Low Vortex

作　　者：赵大军[1,2] 江玉华[1,3] 李莹[4] 

机构地区：[1]中国气象科学院灾害天气国家重点实验室 [2]93762部队 [3]重庆市气象台 [4]国家气候中心

出　　处：《高原气象》2011年第5期1158-1169,共12页Plateau Meteorology

基　　金：灾害天气国家重点实验室基金项目(2008LASW-B08);重庆市气象局科技计划项目(zl-200901;zl-201002)共同资助

摘　　要：利用常规观测资料、FY-2C卫星云图、NCEP/NCAR再分析资料,对一次西南低涡暴雨过程进行了诊断分析。结果表明,这次暴雨天气过程的主要影响系统有对流层高层南亚高压、中层低涡、低层切变线(低涡)以及台风"天鹅"。该过程是由3个接连发生的中尺度对流云团直接造成的,发生在西南低涡闭合涡旋范围内的非对称处。利用WRF_ARW(The Advanced Research WRF)中尺度模式进行了数值模拟,结果表明,对流层高层南亚高压脊线附近的强辐散、对流层中层低涡的垂直涡度耦合和对流层低层强劲的东风干冷急流与南风暖湿急流在四川盆地内交汇,促使西南低涡发展、加强。对流层高层的强辐散和低层强辐合相配合,有利于西南低涡的增强、发展。温度场上,发展的西南低涡在300hPa附近出现"暖心"结构,在850hPa以下北冷南暖,冷暖空气交界随着高度的增加向北倾斜。低涡中心南北两侧的次级环流圈上升支在低涡中心附近汇合,出现剧烈的上升运动,促使西南低涡增强。随着高层南亚高压的南移、高空急流的南压,高层辐散减弱,西南低涡也减弱。当中层西风大槽主体移过河套地区,其携带的强冷空气沿高原东侧迅速南下,大量冷空气进入四川盆地,促使西南低涡向南移出盆地,最终减弱、填塞。A case of torrential rainstorm process caused by a southwest vortex（SWV） is diagnosed using the observation data,FY-2C satellite image,and NCEP/NCAR reanalysis data.The result shows that the main influencing systems are South Asia High,lee trough,and shear line from the tropopause to near surface in vertical direction.The tropical storm ＇0907＇（Goni） is another key factor in this case.The torrential rainstorm is directly caused by three mesoscale convective cloud clusters continuously,which occurred asymmetrically in close SWV.The WRF_ARW is used to simulate,the result shows that it prompts the SWV strengthened that strong divergence exists in the vicinity of South Asian High ridge in the upper troposphere,vertical coupling of leeward vortex in the middle troposphere and the strong easterly dry and cold jet and the southward warm and wet jet interaction with each other in the Sichuan Basin in the lower troposphere.There exists a warm core near 300 hPa in developing SWV,this distribution pattern changes to cold in north and warm in south under 850 hPa in the lower troposphere,and the warm and cold air junction section appears northward slope with height increases.The upward motion of secondary circulation on the north and south sides of the low vortex center convergent near vortex center,which results in strong upward motion to enhance the SWV.With the South Asian High and high level jet stream moving to south,high level divergence weakens,causing SWV decay.As main westerly trough moving over the Hetao area,strong cold air behind it rapidly progression southward along the east side of the Plateau,that is a large number of cold air enter into the Sichuan basin to cause SWV moving out Sichuan basin,and it disappears eventually.

关 键 词：西南涡 低空急流 暖心结构 次级环流 

分 类 号：P458.121.2[天文地球—大气科学及气象学]