Linear normal mode analysis of baroclinic instability in a meridional channel
Citable URI
https://hdl.handle.net/1912/3046DOI
10.1575/1912/3046Keyword
BaroclinicityAbstract
Numerical solutions of the unstable, growing modes are found for the two-layer inviscid
quasigeostrophic equations in a meridional channel. A steady mean flow in
the N-S direction is imposed in the upper layer, and it is assumed that changes in
planetary vorticity following this mean flow are balanced by the input of vorticity
from an imposed wind stress curl. Thus in the two-layer system, the vertical shear, in
thermal wind balance, is associated with an interface slope which provides a gradient
of potential vorticity (PV) in the x-direction, of equal magnitude and opposite sign
in the two layers. In the y-direction the PV gradient has the value of planetary beta,
β in both layers.
The unstable modes of this system exhibit a boundary-layer structure across the
channel. They are intensified in the west. The growth rates of the unstable modes are
of the same order as the zonal case, however the range of wavenumber and shear for
which instability is possible is larger. Established cutoff criteria for the equal-layer
zonal case are not applicable, and no analogous criteria has yet been found. Growing
modes are found even for very weakly sheared flows, and this suggests that baroclinic
instability may represent a more significant source of mid-ocean eddy energy than
previously believed.
Description
Submitted in partial fulfillment of the requirements for the degree of Master of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution March 2001
Collections
Suggested Citation
Thesis: Walker, Alison, "Linear normal mode analysis of baroclinic instability in a meridional channel", 2001-03, DOI:10.1575/1912/3046, https://hdl.handle.net/1912/3046Related items
Showing items related by title, author, creator and subject.
-
Baroclinic instability of a meridionally varying basic state
Meacham, Stephen P. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1984-06)Several problems are addressed herein. They are loosely connected by the theme of resonant triad interactions. The main topic is the finite amplitude evolution of weakly unstable, linear eigenmodes in a meridionally ... -
Generation of mid-ocean eddies : the local baroclinic instability hypothesis
Arbic, Brian K. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2000-08)The plausibility of local baroclinic instability as a generation mechanism for midocean mesoscale eddies is examined with a two-layer, quasi-geostrophic (QG) model forced by an imposed, horizontally homogeneous, vertically ... -
Instabilities and radiation of thin, baroclinic jets
Talley, Lynne D. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1982-06)Oceanic fluctuations are dependent on geographical location. Near intense currents, the eddy field is highly energetic and has broad meridional extent. It is likely that the energy arises from instabilities of the intense ...