HR: 13:40h
AN: A33H-01 INVITED    [Abstracts]
TI: Transport and mixing of chemical airmasses in idealized baroclinic life cycles
AU: * Polvani, L M
EM: lmp@columbia.edu
AF: Columbia University, Department of Applied Physics & Applied Mathematics, 500 West 120th Street, Room 216, New York, NY 10027,
AU: Esler, J G
AF: University College London, Department of Mathematics, Gower Street, London, WC1E 6BT, United Kingdom
AB: The transport, mixing, and three-dimensional evolution of chemically distinct airmasses within growing baroclinic waves are studied in idealized, high-resolution, life cycle experiments using suitably initialized passive tracers, contrasting the two well-known life cycle paradigms, distinguished by predominantly anticyclonic (LC1) or cyclonic (LC2) flow at upper levels. It is found that stratosphere-troposphere exchange differs significantly between the two life cycles. Specifically, transport from the stratosphere into the troposphere is significantly larger for LC2 (typically by 50%), due to the presence of large and deep cyclonic vortices that create a wider surf zone than for LC1. In contrast, the transport of tropospheric air into the stratosphere is nearly identical between the two life cycles. The mass of boundary layer air uplifted into the free troposphere is similar for both life cycles, but much more is directly injected into the stratosphere in the case of LC1 (fourfold, approximately). However, the total mixing of boundary layer with stratospheric air is larger for LC2, owing to the presence of the deep cyclonic vortices that entrain and mix both boundary layer air from the surface and stratospheric air from the upper levels. For LC1, boundary layer and stratospheric air are brought together by smaller cyclonic structures that develop on the poleward side of the jet in the lower part of the middleworld, resulting in correspondingly weaker mixing. As both the El Nino-Southern Oscillation and the North Atlantic Oscillation are correlated with the relative frequency of life cycle types, corresponding changes in chemical transport and mixing are to be expected.
UR: http://www.columbia.edu/~lmp/pubs.html
DE: 0341 Middle atmosphere: constituent transport and chemistry (3334)
DE: 0368 Troposphere: constituent transport and chemistry
DE: 3334 Middle atmosphere dynamics (0341, 0342)
DE: 3362 Stratosphere/troposphere interactions
DE: 3364 Synoptic-scale meteorology
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting