高原涡移出高原后持续的对流层高层环流特征

Circulation Features of Sustained Departure Qinghai-Xizang Plateau Vortex at Upper Tropospheric Level

利用NCEP/NCAR再分析资料、历史天气图与青藏高原低涡切变线年鉴,继高原涡移出高原后持续的对流层中层环流特征分析基础上,依据持续强影响高原涡的分类,对1998-2012年持续强影响高原涡不同类型在生成、移出高原、持续强盛与将减弱消失时的对流层上部多种物理场进行了合成与对比分析。结果表明:持续强影响高原涡持续的对流层高层共同的环流特征是,南亚高压脊线在25°N-28°N,东伸到100°E以东;低涡附近或以北的200 h Pa上空有≥32 m·s-1急流核区的西风急流,和300 h Pa上空有≥20 m·s-1中心区的较强偏西风气流,影响低涡活动的500 h Pa天气系统与低涡的上空200 h Pa有辐散区。反映了高空辐散、高空锋区分别对低涡起了利于低涡辐合加强、高位涡下传引起低涡涡度增加的作用。研究分析还揭示了各类高原涡移出高原后持续的对流层高层的环流特征的主要差异和物理图象。

By using NCEP / NCAR reanalysis data,historic weather graphs and Qinghai-Xizang Plateau vortex and shear line yearbooks,on basis of circulation features analysis on middle tropospheric level,according to the former sorted types of sustained departure Plateau Vortex with strong influence（ SISDPV）,the various physical fields on upper tropospheric level of different types of SISDPV are studied by composite and comparison methods in formation phase,departure phase,sustained strong phase and weak and varnishing phase from 1998 to 2012.The results showthat the same circulation features on upper tropospheric level of various types of SISDPV are as follows： The South Asian High ridge line is within 25°N-28°N latitude and extend easterly out of the 100°E longitude. There is west wind jet core region with speed more than 32 m ·s-1around or at north side of the SISDPV on 200 h Pa and there is strong leaning west direction wind flowwith speed more than 20 m ·s-1too. There are divergence regions on 200 h Pa,just over the 500 h Pa weather systems,which influence the SISDPV activities.This reflects that the divergence on upper level,frontal zone on upper level benefit to stronger convergence of SISDPV and pass down the high potential vorticity,which will strengthen the SISDPV vorticity field. The study also gained the main differences of circulation features and the physical images of various types of SISDPV on upper tropospheric level.