9.2
Tropical-Extratropical Interactions Between Inertially Unstable Regions and the Aleutian High
John A. Knox, University of Georgia, Athens, GA; and V. L. Harvey
Recent climatological and case-study work has revealed that regions of inertial instability in the deep tropical stratosphere are temporally and spatially collocated with low- and negative-PV "channels" at higher latitudes. This raises the possibility that inertial instability may play a role in the dynamics of the Aleutian High, a prominent low-PV feature of the high-latitude middle atmosphere. If true, this would be the ultimate tropical-extratropical dynamical interaction, extending from the equator to near the North Pole.
In this presentation we use dynamical and tracer data to examine episodes of low-latitude Rossby wave breaking episodes that lead to extrusions of negative-PV tropical air into the extratropics, which through mixing are "diluted" into filaments of low-PV air and are eventually entrained into the Aleutian High. Climatological "phase-locking" of Rossby wave breaking in certain longitude bands in winter constricts the region of inertial instability to a narrow poleward-eastward region, from which these filaments are drawn into higher latitudes. Dynamical interactions between the deep tropics and the high latitudes appear to be relatively tightly confined in space as well as in time. How these pulses of low-PV air from the tropics modulate the Aleutian High, and how they may relate to Aleutian High-related phenomena such as stratospheric sudden warmings, will also be examined.
Session 9, Planetary Waves and Tropical-Extratropical Interaction
Wednesday, 11 June 2003, 10:00 AM-11:00 AM
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