大气科学2017，Vol.41Issue(4)：713-726,14.DOI:10.3878/j.issn.1006-9895.1611.16179
一次高原低涡与高原切变线演变过程与机理分析
Evolution and Mechanism Analysis of a Plateau Vortex and Plateau Shear Line
摘要
Abstract
The genesis mechanism and evolution of a plateau shear line are analyzed.This process involved the weakening of an eastward moving plateau vortex and the formation of a plateau shear line,which moved southeastward later under the favorable background circulation and caused heavy rain in Sichuan and Chongqing.The Okubo-Weiss (OW) parameter (Vow) is introduced first.The OW parameter is frequently used in tropical cyclone study to measure the relative amount of rotation and deformation in vortex and shear flow,and has a good potential for identifying the location of plateau shear line formation and development.The results show that,at 500 hPa the Vow value changed from positive to negative and Vow negative belt had a good potential for identifying the location of plateau shear line formation at the genesis stage of plateau shear line.The intensity of negative Vow value and plateau shear line had a good correlation.The plateau shear line was dominated by negative Vow centers,but positive center also existed,indicating that cyclonic vorticity also occurred in the shear line.This plateau shear line was dominated by stretching deformation and located along the stretching axis orientation in this case.The dynamic mechanism of plateau vortex weakening and plateau shear line formation is then further analyzed by using the vorticity equation and the total deformation equation.The results show that the weakening and disappearance of the plateau vortex were mainly affected by the divergence term.The temporal evolution analysis indicates that this system transformed from plateau vortex with strong cyclonic vorticity to plateau shear line with strong convergence.The twisting term in the total deformation equation made the largest contribution to the formation of the plateau shear line,followed by the horizontal pressure gradient term,and the divergence term made the minimum contribution.When the plateau shear line was dominated by stretching deformation,it restrained the development of plateau vortex.The shear line could be the background flow field that affected the vortex development.关键词
高原低涡/高原切变线/演变过程/机理分析Key words
Plateau vortex/Plateau shear line/Evolution process/Mechanism analysis分类
天文与地球科学引用本文复制引用
李山山,李国平..一次高原低涡与高原切变线演变过程与机理分析[J].大气科学,2017,41(4):713-726,14.基金项目
公益性行业(气象)科研专项GYHY201206042,国家自然科学基金41675057、 91337215 Special Fund for Meteorological Research in the Public Interest (Grant GYHY201206042),National Natural Science Foundation of China (Grants 41675057 and 91337215) （气象）
