Article Type:
Research Article

Effect of Sea Surface Temperature–Wind Stress Coupling on Baroclinic Instability in the Ocean

Michael A. Spall Department of Physical Oceanography, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts

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Print Publication:
01 Apr 2007
DOI:
https://doi.org/10.1175/JPO3045.1
Page(s):
1092–1097
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Abstract

The impact of the observed relationship between sea surface temperature and surface wind stress on baroclinic instability in the ocean is explored using linear theory and a nonlinear model. A simple parameterization of the influence of sea surface temperature on wind stress is used to derive a surface boundary condition for the vertical velocity at the base of the oceanic Ekman layer. This boundary condition is applied to the classic linear, quasigeostrophic stability problem for a uniformly sheared flow originally studied by Eady in the 1940s. The results demonstrate that for a wind directed from warm water toward cold water, the coupling acts to enhance the growth rate, and increase the wavelength, of the most unstable wave. Winds in the opposite sense reduce the growth rate and decrease the wavelength of the most unstable wave. For representative coupling strengths, the change in growth rate can be as large as ±O(50%). This effect is largest for shallow, strongly stratified, low-latitude flows.

Corresponding author address: Michael A. Spall, Department of Physical Oceanography, Woods Hole Oceanographic Institution, Woods Hole, MA 02543. Email: mspall@whoi.edu

Abstract

The impact of the observed relationship between sea surface temperature and surface wind stress on baroclinic instability in the ocean is explored using linear theory and a nonlinear model. A simple parameterization of the influence of sea surface temperature on wind stress is used to derive a surface boundary condition for the vertical velocity at the base of the oceanic Ekman layer. This boundary condition is applied to the classic linear, quasigeostrophic stability problem for a uniformly sheared flow originally studied by Eady in the 1940s. The results demonstrate that for a wind directed from warm water toward cold water, the coupling acts to enhance the growth rate, and increase the wavelength, of the most unstable wave. Winds in the opposite sense reduce the growth rate and decrease the wavelength of the most unstable wave. For representative coupling strengths, the change in growth rate can be as large as ±O(50%). This effect is largest for shallow, strongly stratified, low-latitude flows.

Corresponding author address: Michael A. Spall, Department of Physical Oceanography, Woods Hole Oceanographic Institution, Woods Hole, MA 02543. Email: mspall@whoi.edu

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  • Blumsack, S. L., and P. J. Gierasch, 1972: Mars: The effects of topography on baroclinic instability. J. Atmos. Sci., 29 , 1081–1089.

  • Chelton, D. B., and Coauthors, 2001: Observations of coupling between surface wind stress and sea surface temperature in the eastern tropical Pacific. J. Climate, 14 , 1479–1498.

    • Search Google Scholar
    • Export Citation

  • Chelton, D. B., M. G. Schlax, M. H. Freilich, and R. F. Milliff, 2004: Satellite measurements reveal persistent small-scale features in ocean winds. Science, 303 , 978–983.

    • Search Google Scholar
    • Export Citation

  • Eady, E. T., 1949: Long waves and cyclone waves. Tellus, 1 , 33–52.

  • Linder, C. A., and G. Gawarkiewicz, 1998: A climatology of the shelfbreak front in the Middle Atlantic Bight. J. Geophys. Res., 103 , 18405–18424.

    • Search Google Scholar
    • Export Citation

  • Lindzen, R. S., and S. Nigam, 1987: On the role of sea surface temperature gradients in forcing low-level winds and convergence in the Tropics. J. Atmos. Sci., 44 , 2418–2436.

    • Search Google Scholar
    • Export Citation

  • Liu, W. T., X. Xie, P. S. Polito, S-P. Xie, and H. Hashizume, 2000: Atmospheric manifestation of tropical instability wave observed by QuikSCAT and Tropical Rain Measuring Mission. Geophys. Res. Lett., 27 , 2545–2548.

    • Search Google Scholar
    • Export Citation

  • O’Neill, L. W., D. B. Chelton, S. K. Esbensen, and F. J. Wentz, 2005: High-resolution satellite measurements of the atmospheric boundary layer response to SST variations along the Agulhas return current. J. Climate, 18 , 2706–2723.

    • Search Google Scholar
    • Export Citation

  • Pezzi, L. P., J. Vialard, K. J. Richards, C. Menkes, and D. Anderson, 2004: Influence of ocean–atmosphere coupling on the properties of tropical instability waves. Geophys. Res. Lett., 31 .L16306, doi:10.1029/2004GL019995.

    • Search Google Scholar
    • Export Citation

  • Samelson, R. M., E. D. Skyllingstad, D. B. Chelton, S. K. Esbensen, L. W. O’Neill, and N. Thum, 2006: On the coupling of wind stress and sea surface temperature. J. Climate, 19 , 1557–1566.

    • Search Google Scholar
    • Export Citation

  • Shchepetkin, A. F., and J. C. McWilliams, 2005: The Regional Oceanic Modeling System (ROMS): A split-explicit, free-surface, topography-following coordinate ocean model. Ocean Modell., 9 , 347–404.

    • Search Google Scholar
    • Export Citation

  • Small, R. J., S-P. Xie, and Y. Wang, 2003: Numerical simulation of atmospheric response to Pacific tropical instability waves. J. Climate, 16 , 3723–3741.

    • Search Google Scholar
    • Export Citation

  • Sweet, W., R. Fett, J. Kerling, and P. La Violette, 1981: Air-sea interaction effects in the lower troposphere across the north wall of the Gulf Stream. Mon. Wea. Rev., 109 , 1042–1052.

    • Search Google Scholar
    • Export Citation

  • Wai, M., and S. Stage, 1989: Dynamical analyses of marine atmospheric boundary layer structure near the Gulf Stream oceanic front. Quart. J. Roy. Meteor. Soc., 115 , 29–44.

    • Search Google Scholar
    • Export Citation

  • Wallace, J. M., T. P. Mitchell, and C. Deser, 1989: The influence of sea-surface temperature on surface wind in the eastern equatorial Pacific: Seasonal and interannual variability. J. Climate, 2 , 1492–1499.

    • Search Google Scholar
    • Export Citation

  • Xie, S-P., 2004: Satellite observations of cool ocean–atmosphere interaction. Bull. Amer. Meteor. Soc., 85 , 195–208.

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