The Environmental Fields Analysis of Sustained Departure Tibetan Plateau Vortex Accompanying with Induced South-west low Vortex

By using NCEP/NCAR FNL reanalysis data, historical weather graphs and Tibetan Plateau vortex and shear line year books, based on synoptic and statistical methods, the 2 days or more sustained departure Tibetan Plateau Vortexes ( SDTPVs ) accompanying with influenced South-west vortex( SWV ) activities during 1998 to 2013 is analyzed. Furthermore, the different SWV original positions induced by SDTPV is analyzed by synoptic and diagnosis methods. The new environmental fields understandings and new observational facts of SDTPV accompanying with induced SWV are gained. The results show that: In the joint active processes of SDTPV and SWV, the same moving direction of SDTPV and induced SWV is mainly and their main moving direction is to east or north-east. The SWV induced by SDTPV generated under the South-west air flow in the southeastern portion of the SDTPV Circulation, on 500hPa there is weaker air flow along longitude direction in east Asia and cold air influences the SDTPV. The SWV accompanying with the SDTPV will be stronger when SDTPV is stronger and be influenced a lot by the SDTPV, its environmental fields change consistently with the SDTPV conditions. The SWV accompanying with the SDTPV generated in shear air field of South-west air flow of Bengal gulf and its north high pressure on 700hPa, it will be stronger with the influencing weather systems on 700hPa. The positive vorticity area in the southeastern portion of the SDTPV Circulation, stronger ascending air flow are the advantageous conditions for the SDTPV and will induce to the generation of the SWV. This is also the important condition of the two vortexes to move together. The strong ascending air flow and large area of positive vorticity region on 700hPa are the important condition for the SWV to be strong and sustained.

Key words: Tiebtan plateau vortex, China South-west vortex, accompanying moving, environmental field