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    Rossby wave instability and apparent phase speeds in large ocean basins

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    jpo3054%2E1.pdf (1.875Mb)
    Date
    2007-05
    Author
    Isachsen, P. E.  Concept link
    LaCasce, Joseph H.  Concept link
    Pedlosky, Joseph  Concept link
    Metadata
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    Citable URI
    https://hdl.handle.net/1912/4147
    As published
    https://doi.org/10.1175/jpo3054.1
    DOI
    10.1175/jpo3054.1
    Keyword
     Rossby waves; Ocean models; Barotropic flows; Baroclinic flows 
    Abstract
    The stability of baroclinic Rossby waves in large ocean basins is examined, and the quasigeostrophic (QG) results of LaCasce and Pedlosky are generalized. First, stability equations are derived for perturbations on large-scale waves, using the two-layer shallow-water system. These equations resemble the QG stability equations, except that they retain the variation of the internal deformation radius with latitude. The equations are solved numerically for different initial conditions through eigenmode calculations and time stepping. The fastest-growing eigenmodes are intensified at high latitudes, and the slower-growing modes are intensified at lower latitudes. All of the modes have meridional scales and growth times that are comparable to the deformation radius in the latitude range where the eigenmode is intensified. This is what one would expect if one had applied QG theory in latitude bands. The evolution of large-scale waves was then simulated using the Regional Ocean Modeling System primitive equation model. The results are consistent with the theoretical predictions, with deformation-scale perturbations growing at rates inversely proportional to the local deformation radius. The waves succumb to the perturbations at the mid- to high latitudes, but are able to cross the basin at low latitudes before doing so. Also, the barotropic waves produced by the instability propagate faster than the baroclinic long-wave speed, which may explain the discrepancy in speeds noted by Chelton and Schlax.
    Description
    Author Posting. © American Meteorological Society, 2007. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 37 (2007): 1177-1191, doi:10.1175/jpo3054.1.
    Collections
    • Physical Oceanography (PO)
    Suggested Citation
    Journal of Physical Oceanography 37 (2007): 1177-1191
     

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