EVENT DETAILS AND ABSTRACT

Title: An interfacial wave treatment of tropopause dynamics
Speaker: Professor D. Muraki
Speaker Info: Courant Inst. Math.Sci.
Brief Description:
Special Note:
Abstract:

The tropopause is the sharp transition, roughly at an altitude of 10\,km, between the two lowest layers of the atmosphere -- the troposphere and the stratosphere. Vertical disturbances of this internal atmospheric interface propagate as waves in an eastward direction following the midlatitude jetstream.

The basic equations of the atmosphere are those of a density-stratified, rotating and Boussinesq fluid system, which possess a simplified zero Rossby number limit known as {\it quasi-geostrophy}. A highly-successful leading-order asymptotic theory, quasi-geostrophy encompasses many of the important atmospheric behaviors, including the {\it baroclinic instability} of the jetstream to high/low pressure cells, yet does not contain dynamical asymmetries which result in the intensified low pressures characteristic of midlatitude disturbances. Recent work (with NCAR collaborators Snyder \& Rotunno) has produced a systematic asymptotic extension to the theory of quasi-geostrophy in which these asymmetries are captured in the next-order corrected dynamics.

Modelling the tropopause as a dynamical free-boundary between tropospheric and stratospheric domains, it is shown that the next-order corrections to quasi-geostrophy are necessary to produce the enhanced downward displacements that are clearly evident from meteorological observations. These next-order correct solutions again demonstrate an asymmetric bias towards low pressure and cyclonic flow that is consistent with their association as precursors to midlatitude storms (with Greg Hakim, NCAR \& University of Washington).