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Long extratropical planetary wave propagation in the presence of slowly varying mean flow and bottom topography. Part I: the local problem

Long extratropical planetary wave propagation in the presence of slowly varying mean flow and bottom topography. Part I: the local problem
Long extratropical planetary wave propagation in the presence of slowly varying mean flow and bottom topography. Part I: the local problem
One of the most successful theories to date to explain why observed
planetary waves propagate westwards faster than linear flat-bottom
theory predicts has been to include the effect of background baroclinic
mean flow, which modifies the potential vorticity waveguide in which
the waves propagate. (Barotropic flows are almost everywhere too small to explain the observed differences.) That theory accounted for most, but not all, of the observed wave speeds. A later attempt to examine the effect of the sloping bottom on these waves (without the mean flow effect) did not find any overall speed-up. This paper combines these two effects, assuming long (geostrophic) waves and slowly varying mean flow and topography, and computes group velocities at each point in the global ocean. These velocities turn out to be largely independent of the orientation of the wavevector. A second speed-up of the waves is found (over that for mean flow only). Almost no eastward-oriented group velocities are found, so that features which appear to propagate in the same sense as a subtropical gyre would have to be coupled with the atmosphere or be density-compensated in some manner.
planetary waves, ocean circulation
0022-3670
784-801
Killworth, P.D.
9fc0c4a0-e1fb-4073-8997-436b59c74bf2
Blundell, J.R.
88114f32-6b76-46b2-b2d8-d6ef64a82b0d
Killworth, P.D.
9fc0c4a0-e1fb-4073-8997-436b59c74bf2
Blundell, J.R.
88114f32-6b76-46b2-b2d8-d6ef64a82b0d

Killworth, P.D. and Blundell, J.R. (2003) Long extratropical planetary wave propagation in the presence of slowly varying mean flow and bottom topography. Part I: the local problem. Journal of Physical Oceanography, 33 (4), 784-801. (doi:10.1175/1520-0485(2003)33<784:LEPWPI>2.0.CO;2).

Record type: Article

Abstract

One of the most successful theories to date to explain why observed
planetary waves propagate westwards faster than linear flat-bottom
theory predicts has been to include the effect of background baroclinic
mean flow, which modifies the potential vorticity waveguide in which
the waves propagate. (Barotropic flows are almost everywhere too small to explain the observed differences.) That theory accounted for most, but not all, of the observed wave speeds. A later attempt to examine the effect of the sloping bottom on these waves (without the mean flow effect) did not find any overall speed-up. This paper combines these two effects, assuming long (geostrophic) waves and slowly varying mean flow and topography, and computes group velocities at each point in the global ocean. These velocities turn out to be largely independent of the orientation of the wavevector. A second speed-up of the waves is found (over that for mean flow only). Almost no eastward-oriented group velocities are found, so that features which appear to propagate in the same sense as a subtropical gyre would have to be coupled with the atmosphere or be density-compensated in some manner.

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Published date: April 2003
Keywords: planetary waves, ocean circulation

Identifiers

Local EPrints ID: 130
URI: http://eprints.soton.ac.uk/id/eprint/130
ISSN: 0022-3670
PURE UUID: ca3845eb-371d-452e-b9fa-11b9f0fc6796

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Date deposited: 22 Oct 2003
Last modified: 15 Mar 2024 04:36

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Contributors

Author: P.D. Killworth
Author: J.R. Blundell

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