85th AMS Annual Meeting

Wednesday, 12 January 2005
A study of coherent tropopause disturbances within the Northern Hemispheric circumpolar vortex
Joseph R. Kravitz, University at Albany/SUNY, New York, NY; and L. F. Bosart, D. Keyser, and A. R. Aiyyer
Poster PDF (527.6 kB)
Mesoscale tropopause-based coherent disturbances (CTDs) embedded within the Northern Hemispheric (NH) large-scale circumpolar vortex (CPV) are characterized by closed potential temperature and/or pressure contours on maps of the dynamic tropopause (DT). Most commonly of arctic origin, CTDs frequently rotate through the bases of troughs at the southern extent of the CPV, corresponding to the northern margins of the most prominent jet streams in the Northern Hemisphere. The interaction of these disturbances with the jet stream, particularly over North America, as well as mergers with extratropical middle-latitude disturbances, can sometimes result in unusually intense cyclones. CTDs are of scientific interest for several reasons. Given their polar location, observational data limitations can complicate investigations of the thermodynamical and dynamical processes that govern the origin, structure and life cycles of CTDs embedded within the CPV. Predictability is also a challenge due to numerical weather prediction model initialization and physics limitations.

The purpose of this presentation is to describe and categorize the behavior of CTDs from a climatological and case study perspective. This research expands upon previous work by utilizing high–resolution data (NCEP GFS initialized gridded datasets obtained from NCAR) for the extended cool season of September through May (1999–2004). Subjective tracking of the disturbances on the DT for the 2002–2003 season provides a basis for selecting case studies as well as setting a standard for comparison with a more comprehensive, objectively generated climatology for 1999–2004. Preferred regions of genesis, lysis and tracks of CTDs will be presented. In addition, categorization of CTD behavior will be described based upon track, as well as interaction with the western Atlantic and western Pacific jet streams. This study expands upon prior work in describing the effect of interaction of these disturbances with jet streaks and the potential for intense cyclone development. Preliminary findings indicate several categories of CTD behavior ranging from short-lived disturbances with origins along the southern periphery of the CPV, to long-lived (3–6 weeks) disturbances with polar origins that eventually migrate to the southern periphery of the CPV, frequently invigorating the adjacent jet stream. Three main regions of origin are: 1) Northern Hudson Bay extending to the adjacent Elizabeth Islands and Arctic Ocean; 2) Siberia and the adjacent Arctic Ocean; and 3) Sea of Okhotsk (north of Japan) extending to Eastern Mongolia. The main regions of CTD lysis are over the northwestern Atlantic and Pacific Oceans.

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