11.3
Seasonally coherent recoveries from stratospheric sudden warmings

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Thursday, 27 January 2011: 2:00 PM
Seasonally coherent recoveries from stratospheric sudden warmings
3B (Washington State Convention Center)
Peter Hitchcock, Univ. of Toronto, Toronto, ON, Canada; and T. G. Shepherd

The variability of the Arctic polar vortex has been described in terms of a variety of indices and events, including stratospheric sudden warmings, vortex intensifications, and the polar jet oscillation, which emphasize different dynamics and time scales. We present a tool for visualizing the daily evolution of the zonal mean, vertical structure of the vortex over several decades, which proves useful for understanding the relationships between these descriptions. For instance, more than half of the observed major sudden warming events lead to a coherent, robust super-recovery of the mid- and upper-stratospheric jet over several months following the initial burst of wave activity, while the zonal-mean recovery of the remainder of the events does not appear to follow any robust or consistent evolution on time-scales of longer than a week. The seasonally coherent events, in the reanalyzed record, more commonly follow vortex-split type events than they do vortex-displacements, and are responsible for a significant fraction of vortex intensifications. These statistics are compared to those simulated by the Canadian Middle Atmosphere Model, a chemistry-climate model.