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Potential vorticity dynamics of a tropopause polar vortex
Steven M. Cavallo, Univ. of Washington, Seattle, WA; and G. J. Hakim
Tropopause polar vortices (TPVs) are ubiquitous features of the high latitude tropopause, having typical diameters of about 1000 km and lifetimes that may last more than a month. Little is known about the physical mechanisms that control the intensity of TPVs. Here we examine the dynamics of TPVs through an Ertel Potential Vorticity (EPV) perspective, by assessing diabatic and frictional processes that produce vortex intensity changes.
To better understand the growth and decay processes governing TPVs, the hypothesis that diabatic mechanisms play a non-trivial role is examined through a diagnostic partitioning of the EPV tendency equation. From a case study of one TPV we will show that radiation plays an integral role in the life cycle. In particular, cloud-top radiational cooling acts to intensify the tropopause cyclone. Further investigation of the significance and feedbacks between radiation and latent heating will be examined in the evolution of an idealized vortex.
Session 1, PV and Vorticity Dynamics
Monday, 25 June 2007, 8:45 AM-10:15 AM, Ballroom South
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