Other Scholarly Content

 

Narrowband Oscillations in the Upper Equatorial Ocean. Part II: Properties of Shear Instabilities Public Deposited

Downloadable Content

Download PDF
https://ir.library.oregonstate.edu/concern/defaults/47429f98x

Descriptions

Attribute NameValues
Creator
Abstract
  • Narrowband oscillations observed in the upper equatorial Pacific are interpreted in terms of a random ensemble of shear instability events. Linear perturbation analysis is applied to hourly averaged profiles of velocity and density over a 54-day interval, yielding a total of 337 unstable modes. Composite profiles of mean states and eigenfunctions surrounding the critical levels suggest that the standard hyperbolic tangent model of Kelvin–Helmholtz (KH) instability is a reasonable approximation, but the symmetry of the composite perturbation is broken by the stratification and vorticity gradient of the underlying equatorial undercurrent. Unstable modes are found to occupy a range of frequencies with a peak near 1.4 mHz, consistent with the frequency content of the observed oscillations. A probabilistic theory of random instabilities predicts this peak frequency closely. An order of magnitude estimate suggests that the peak frequency is of order N, in accord with the observations. This results not from gravity wave physics but from the balance of shear and stratification that governs shear instability in geophysical flows. More generally, it is concluded that oscillatory signals with frequency bounded by N can result from a process that has nothing to do with gravity waves.
Resource Type
DOI
Date Available
Date Issued
Citation
  • Smyth, W. D., J. N. Moum, J. D. Nash, 2011: Narrowband Oscillations in the Upper Equatorial Ocean. Part II: Properties of Shear Instabilities. Journal of Physical Oceanography, 41, 412–428.
Keyword
Rights Statement
Funding Statement (additional comments about funding)
  • The project was funded by the National Science Foundation via Grants 0424133, 0622922, and 0728375.
Publisher
Peer Reviewed
Replaces
Additional Information
  • Vol. 41 no. 3.
  • description.provenance : Submitted by Deborah Campbell (deborah.campbell@oregonstate.edu) on 2012-02-09T17:47:10Z No. of bitstreams: 1 SmythWD.CEOAS.NarrowbandOscillationsUpperII.pdf: 1783260 bytes, checksum: 304acfa4d63b24736a3de42052411b05 (MD5)
  • description.provenance : Made available in DSpace on 2012-02-09T17:47:10Z (GMT). No. of bitstreams: 1 SmythWD.CEOAS.NarrowbandOscillationsUpperII.pdf: 1783260 bytes, checksum: 304acfa4d63b24736a3de42052411b05 (MD5) Previous issue date: 2011-03
  • Journal of Physical Oceanography

Relationships

Parents:

This work has no parents.

Items