高原东侧突发性大暴雨过程中螺旋度的诊断分析  

Diagnostic analysis of the helicity for a heavy rainfall in the east of Plateau

作　　者：慕建利[1,2] 李泽椿 寿绍文[1] 杜继稳[2] 

机构地区：[1]南京信息工程大学大气科学学院,南京210044 [2]陕西省气象局,西安710014 [3]国家气象中心,北京100081

出　　处：《气象科学》2009年第2期181-186,共6页Journal of the Meteorological Sciences

基　　金：国家自然科学基金项目(40875025,40875030,40775033,40505010)和IAM200709

摘　　要：利用MM5模式模拟输出结果,对2002年6月8—9日发生在陕西省和四川北部的一次突发性大暴雨过程进行了螺旋度诊断分析。结果表明:暴雨区附近总存在一对紧邻的大小(低层)或正负(中层)螺旋度中心,低层螺旋度正值区强度远大于中高层螺旋度正负值区,对流层中层正负中心的轴线随高度呈逆时针旋转,相应的垂直结构是一对正负相伴的螺旋度柱。当暴雨区东侧正螺旋度突然向高层伸展,西侧伴有负螺旋度发展,且两中心间等值线变密集时,暴雨开始,大小(正负)螺旋度最强及其间等值线最紧密时,暴雨达到最强盛时期,而且暴雨就发生在两螺旋度之间偏大值中心的等值线密集区。进一步分析表明:螺旋度发生发展的主要贡献者是水平速度和水平速度的垂直切变。Using the results of MM5 mesoscale non-hydrostatic model,the helicity of a heavy rainfall occurring in the east of plateau from June 8 to June 9,2002 was diagnosed and analysed. The results showed that there was a pair of centers of positive and negative helicity in the neighbouhood of torrential rain areas. The intensity of positive helicity at the lower level of troposphere was more higher than the positive or negative helicity at the middle and high level of troposphere. The axes of positive and negative helicity circumrotated counterclockwise with elevation and the vertical structure was a pair of columns of intercomparing helicity with opposite signs at the middle-level of troposphere. The evolution and areas of heavy rainfall had a closed relation with the development of helicity at the middle and lower level of troposphere. The torrential rain occurrs when the positive helicity in the eastern part of the heavy rainfall extends suddenly to upper level, having the negative helicity in the western part of the torrentail rain and close isolines in the two centers of helicity. The heavy rainfall happened in the dense area of the isolines. Furthermore, horizontal velocity and its vertical shear were main contribution to the evolution of helicity, which mean the development of lower-level jet and vertical vorticity. Namely the increase of helicity led to the development of unstable energy and vertical velocity, promoting the evolution of convectional system,which indicated that the development of helicity was one of the rainstorm-forming mechanisms.

关 键 词：突发性大暴雨 螺旋度 诊断分析 

分 类 号：P458.121.1[天文地球—大气科学及气象学]