A multiple-level trajectory analysis of vortex filaments

Simultaneous, multiple-level contour advection and reverse domain-filling simulations of the polar vortex are performed to examine the three-dimensional structure of filaments. The evolution of a contour near the vortex edge over three northern hemisphere winters is examined. The results show that filaments forming at the edge have a fairly coherent vertical structure often over the whole stratosphere. The filaments linked together form vertically aligned material sheets which tend to tilt outward with height. Three specific examples of vortex edge evolution over 10-day periods are shown; two of these examples appear to be somewhat similar to the ''remote'' and ''local'' wave-breaking cases studied by Dritschel and Savaranan [1994]. The third example, a final warming, is a combination of the two other cases. Using the change in the vortex edge contour length to compute the Liapunov coefficient, we show the variation in that quantity, the geopotential height variance, and the eddy diffusion coefficient K-yy for the three winters. The changes in Liapunov coefficient roughly correlate with the changes in the other two quantities.