Computer Science
Scientific paper
Jun 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001phdt........19s&link_type=abstract
Thesis (PhD). THE UNIVERSITY OF CHICAGO, Source DAI-B 61/12, p. 6517, Jun 2001, 198 pages.
Computer Science
Scientific paper
This thesis concerns the earth's extratropical tropopause and the related dynamics of baroclinic instability. The premise of the study is baroclinic adjustment: eddies attempt to relax potential vorticity (PV) and potential temperature (PT) of the flow to a baroclinically neutral state. The neutrality condition thus imposes constraint on the observed tropopause height and the geometry of jet. First, the shortcomings of the extant adjustment theories are addressed by studying the neutrality condition for a 2D nonseparable Eady problem. The relative roles of the meridional width of jet, surface baroclinicity, and the tropopause morphology are investigated. It is found that the essential ingredient for the equilibration of a monochromatic baroclinic wave is the asymmetric horizontal mixing of PT at the surface and on the tropopause. Even though the partial mixing of PT does not completely neutralize the flow in the sense of Chamey, Stern, and Pedlosky, the range of unstable zonal scale shifts up, stabilizing certain initially unstable wavenumbers through shortwave cutoff. The partial mixing of PT gives rise to barotropic jet and enhances static stability, consistent with classical lifecycle experiments. This picture does not require horizontal shear as the ``cause'' of equilibration: in fact, shear is a product of mixing. This represents a significant departure from the ``barotropic governor'' hypothesis. A local analysis of the observed Southern Hemisphere flow provides a circumstantial evidence for the above adjustment. Next, using a 2D (longitude-height) model, I investigate the role of baroclinic eddies in the formation and of extratropical tropopause and the maintenance of tropospheric PV and lapse rate. It is shown that mixing associated with baroclinic eddies successfully concentrates PV gradients at the top of the ``cat's eye,'' thereby creating a ``tropopause.'' The tropospheric PV and static stability equilibrate at values significantly higher than the basic state, despite radiative relaxation. However, the height of the emerging tropopause is dictated by the wave with the largest zonal scale, which can lead to an unrealistically high tropopause. The lack of scale limiting mechanism in this 2D model prompts further studies using a full-blown general circulation models (GCM).
No associations
LandOfFree
A study of the extratropical tropopause and baroclinic adjustment does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with A study of the extratropical tropopause and baroclinic adjustment, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and A study of the extratropical tropopause and baroclinic adjustment will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-796027