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Robert O. Reid

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Robert O. Reid
and
Ou Wang

Abstract

The well-known Rhines theory of bottom-trapped topographic Rossby waves (TRW) in a uniformly stratified ocean over a sloping seabed, and its dispersion relation between wave frequency and wavenumber components, have served a very useful purpose in prompting recognition of the existence of TRW in the ocean and in motivating the search for sources of such disturbances. However, in quantitative studies of backward ray tracing of bottom-trapped Rossby waves for source search purposes, a realistic profile of the buoyancy frequency N(z) within the water column ought to be taken into account. Toward this goal an analytic solution for linear, quasigeostrophic, topographic Rossby waves for an ocean having regionally distinct exponential profiles of buoyancy frequency is offered.

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Artemio Gallegos-Garcia
,
William J. Emery
,
Robert O. Reid
, and
Lorenz Magaard

Abstract

Frequency-wavenumber spectra of sea surface temperature and wind-stress curl are computed from 11 years of surface marine observations taken in the eastern North Pacific. These data were averaged by month and 2° quadrangles to yield spectra with periods from 2 to 48 months and zonal wavelengths from 400 to 4000 km. Spectra were computed for all 2° zonal bands between 16 and 40°N using data from the area between 120 and 160°W. Missing monthly values led to the computation of these spectra using a least-squares Fourier expansion which eliminated the need for temporal interpolation. Frequency spectra computed with this technique compare well with spectra using standard Fourier methods.

The resulting spectra were found to separate naturally into two regions; one between 29 and 40°N and the second between 15 and 29°N. Even within these zonal bands there were some important north–south changes. The annual signal was found to dominate the spectra of sea surface temperature at almost all wavelengths. The semiannual and 2-year periods were often also significant in sea surface temperature spectra. The annual peak dominated many of the wind-stress curl spectra at the longest wavelengths (∼2000–4000 km). Most of the energetic peaks in all spectra were symmetric with respect to east–west wavenumber. There were, however, some asymmetries suggesting both east and westward phase propagation. Generally, wind-stress curl spectra were white in frequency and red in wavenumber while sea surface temperature spectra were red in wavenumber but dominated by the 2-year, annual and semiannual periods in frequency.

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James H. Saylor
,
Joseph C. K. Huang
, and
Robert O. Reid

Abstract

Current velocities and water temperatures were observed in southern Lake Michigan with an array of AMF vector-averaging current meters during late spring, summer and fall 1976. Analyses of the recorded current data have revealed that persistent oscillations of nearly 4 days in period were at least as energetic as inertial oscillations in the kinetic energy spectra and current hodographs. The 4-day oscillations were present at all stations, including a very clear signal at stations near the center of the lake basin. This lake-wide oscillation was present during both stratified and unstratified seasons and current vectors rotated cyclonically near the center of the lake and anticyclonically elsewhere. The observed rotational oscillations closely fit the characteristics of barotropic second-class motions of a basin with variable depth first described by Lamb (1932). While such topographic vortex modes are of the same class as low-frequency shelf waves, their kinematic properties and natural period are governed by the lake shape as well as the bathymetry. Moreover, the gravest mode is unique among these waves in having nonzero velocity at the lake center. The present observations give clear evidence for the existence of the gravest mode of such oscillations in southern Lake Michigan.

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Richard A. Craig
,
Chester W. Newton
,
R. Robert Rapp
, and
Robert O. Reid

Abstract

No abstract available.

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