The final warming of the stratosphere

Abstract

The dramatic changes during spring in the shape of the polar vortex in the stratosphere of the two hemispheres are illustrated using perspective plots of the three-dimensional structure of the isotach and potential vorticity fields. In the southern hemisphere, the vortex shape evolves from a cone, slightly expanding with height and nearly symmetric about the pole, to an inverted cone, distorted and displaced from the pole. At 10 mb, in particular, the flow reverses to easterlies some time after the temperature gradient at high latitudes reverses. In the northern hemisphere, there is much more variability in both the structure of the flow and the time of the breakdown of the westerly vortex. At 10 mb, in particular, the reversal of the flow may precede or follow that of the temperature gradient. -from Author