A dynamical diagnosis of the stratospheric polar vortex in 2003-2004 northern winters viewed in an isentropic

In this paper the Northern Hemisphere stratospheric polar vortex oscillation in a new semiLagrangian θ-PVLAT coordinate constructed using the daily ECMWF 60level data during 20032004 winters is diagnosed. From the EOF analysis of the potential vorticity anomalies in this new coordinate, we get the polar vortex oscillation (PVO) index on which the lead/lag regression analyses of the zonal wind and temperature are completed with the characteristics of stratospheric and tropospheric circulations during PVO progress obtained. The main results show that (1) The θ-PVLAT coordinate has nice materiality and does well in describing the variation of mass transport, particularly the variation of atmospheric circulation in the North Hemispheric high latitudes; (2) there are a pair of propagating modes that are pole-ward and down-ward in the stratosphere along which the zonal wind and temperature anomalies with opposite signs propagate and an equator ward propagating mode in the troposphere; (3) there exists a certain temporal relation between these two propagating modes: the starting time of the equator ward propagating in the lower atmosphere is nearly the same as the arrival time in the polar zone of the pole-ward and down-ward propagating in the stratosphere; (4) we can explain the variance of polar vortex by a meridional mass circulation driven by both the diabatic heating and baroclinic waves. This mass circulation leads to the exchange between warm air in the low latitude areas and cold air in the polar areas by the process of Stratospheric and Tropospheric Exchange (STE), and thus reconstructs the dynamical and thermal patterns of the whole atmosphere.