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Global Patterns of Low-Mode Internal-Wave Propagation. Part II: Group Velocity

Global Patterns of Low-Mode Internal-Wave Propagation. Part II: Group Velocity Using a set of 80 globally distributed time series of near-inertial and semidiurnal energy E and energy flux F computed from historical moorings, the group velocity ĉ g ≡ F E −1 is estimated. For a single free wave, observed group speed | ĉ g | should equal that expected from linear wave theory. For comparison, the latitude dependence of perceived group speed for perfectly standing waves is also derived. The latitudinal dependence of observed semidiurnal | ĉ g | closely follows that expected for free waves at all latitudes, implying that 1) low-mode internal tides obey linear theory and 2) standing internal-tidal waves are rare in the deep ocean for latitudes equatorward of about 35°. At higher latitudes, standing waves cannot be easily distinguished from free waves using this method because their expected group speeds are similar. Near-inertial waves exhibit scattered | ĉ g | values consistent with the passage of events generated at various latitudes, with implied frequencies ω ≈ 1.05–1.25 × f , as typically observed in frequency spectra. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Physical Oceanography American Meteorological Society

Global Patterns of Low-Mode Internal-Wave Propagation. Part II: Group Velocity

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Publisher
American Meteorological Society
Copyright
Copyright © 2006 American Meteorological Society
ISSN
1520-0485
DOI
10.1175/JPO3086.1
Publisher site
See Article on Publisher Site

Abstract

Using a set of 80 globally distributed time series of near-inertial and semidiurnal energy E and energy flux F computed from historical moorings, the group velocity ĉ g ≡ F E −1 is estimated. For a single free wave, observed group speed | ĉ g | should equal that expected from linear wave theory. For comparison, the latitude dependence of perceived group speed for perfectly standing waves is also derived. The latitudinal dependence of observed semidiurnal | ĉ g | closely follows that expected for free waves at all latitudes, implying that 1) low-mode internal tides obey linear theory and 2) standing internal-tidal waves are rare in the deep ocean for latitudes equatorward of about 35°. At higher latitudes, standing waves cannot be easily distinguished from free waves using this method because their expected group speeds are similar. Near-inertial waves exhibit scattered | ĉ g | values consistent with the passage of events generated at various latitudes, with implied frequencies ω ≈ 1.05–1.25 × f , as typically observed in frequency spectra.

Journal

Journal of Physical OceanographyAmerican Meteorological Society

Published: Feb 6, 2006

References