Study On Characteristic Of Southwest Vortex Moving And Its Mechanism

Here we improve the statistical method of southwest vortex by using the NCEP/NCAR reanalysis data of the geopotential height and wind for 1951-2005, to separate independent process of southwest vortex building, developing and moving, and statistic times of vortex moving eastward each year and its daily variation. On the base of the statistic, we research the characteristic of southwest vortex moving and its mechanism.By contrast of moving outside vortex and not moving outside vortex, we found that there are quite differences in geopotential height and vorticity advection field in the middle troposphere of atmosphere above the source region of southwest vortex, temperature advection and divergence field in the low troposphere of atmosphere, coupling of high-jet and low-jet, East Asian summer monsoon and Qinghai-Tibet plateau's heating, in which East Asian summer monsoon and Qinghai-Tibet plateau's heating have also effect on interannual and decadal variation of vortex moving eastward.In regard to its daily variation, the main reason vortex moving outside at night is far more frequently than in day is the daily variation of latitudinal thermodynamic circulation producing in the east of Qinghai-Tibet plateau, which would be proved in the time series of plateau's atmosphere heat source, the number of vortex moving outside at night and in day.