The dynamical influence of the stratospheric polar vortex on the atmospheric global circulation

The stratospheric vortex is far more than an ordinary circumpolar current that reacts passively to forcing from the troposphere. It is a vigorously active circulation whose dynamics dominates the winter stratosphere and extends all the way down to the troposphere. Transient distortions and off-polar displacements of this vortex structure lead to planetary scale potential vorticity (PV) anomalies in the polar stratosphere. These PV perturbations in turn generate globally extensive circulation anomalies whose scale and magnitude can be determined by the method of PV inversion.;Results of PV inversion show that the anomalous circulations induced by these stratospheric PV anomalies are vertically and laterally extensive enough to influence the tropopause and the subtropical stratosphere. The vertical impact is of a planetary scale and is strongest directly below the vortex edge at high latitudes, extending substantially down into the midlatitude tropopause. Contour advection (CA) calculations also indicate a significant stratospheric influence on the horizontal transport of middle and high latitude tropopause air. Only those vortex PV anomalies from the lower to middle stratosphere are found to be important for tropopause dynamics. The lateral impact of these vortex perturbations is likewise extensive, tunneling through the midlatitude surf zone into the subtropical stratosphere. Combined PV inversion and CA calculations demonstrate the sheer dominance of the vortex in bringing about the poleward entrainment of subtropical tongues of air during wave events in the polar stratosphere. This vortex influence is clearly non-local, so that even wave distortion events that leave the vortex well confined within the middle latitudes are observed to excite subtropical waves. The poleward migration of these planetary scale tongues of subtropical air also generates anomalous circulations that influence their own movement.;This extensive dynamical impact of the stratospheric vortex has important implications for our current understanding of the atmospheric global circulation. Aside from affecting a central climate regulation mechanism such as the meridional mixing of radiatively important tracers, this stratospheric influence may also be crucial to the dynamics of planetary waves and how these waves modulate the large scale circulation of our atmosphere.