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Wave–vortex decomposition of one-dimensional ship-track data

Bühler, Oliver and Callies, Jörn and Ferrari, Raffaele (2014) Wave–vortex decomposition of one-dimensional ship-track data. Journal of Fluid Mechanics, 756 . pp. 1007-1026. ISSN 0022-1120. https://resolver.caltech.edu/CaltechAUTHORS:20180112-100115650

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Abstract

We present a simple two-step method by which one-dimensional spectra of horizontal velocity and buoyancy measured along a ship track can be decomposed into a wave component consisting of inertia–gravity waves and a vortex component consisting of a horizontal flow in geostrophic balance. The method requires certain assumptions for the data regarding stationarity, homogeneity, and horizontal isotropy. In the first step an exact Helmholtz decomposition of the horizontal velocity spectra into rotational and divergent components is performed and in the second step an energy equipartition property of hydrostatic inertia–gravity waves is exploited that allows a diagnosis of the wave energy spectrum solely from the observed horizontal velocities. The observed buoyancy spectrum can then be used to compute the residual vortex energy spectrum. Further wave–vortex decompositions of the observed fields are possible if additional information about the frequency content of the waves is available. We illustrate the method on two recent oceanic data sets from the North Pacific and the Gulf Stream. Notably, both steps in our new method might be of broader use in the theoretical and observational study of atmosphere and ocean fluid dynamics.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1017/jfm.2014.488DOIArticle
ORCID:
AuthorORCID
Callies, Jörn0000-0002-6815-1230
Ferrari, Raffaele0000-0003-1895-4294
Additional Information:© 2014 Cambridge University Press. (Received 22 May 2014; revised 29 July 2014; accepted 19 August 2014; first published online 9 September 2014) O.B. thanks M. Holmes-Cerfon for interesting discussions and gratefully acknowledges financial support under grants CMG-1024180, DMS-1312159, and DMS-1009213 of the United States National Science Foundation. J.C. and R.F. thank G. Flierl for offering useful feedback during the preparation of the manuscript and acknowledge financial support under grants N-00014-09-1-0458 and GMG-1024198. We also thank three anonymous referees for their very helpful comments.
Funders:
Funding AgencyGrant Number
NSFCMG-1024180
NSFDMS-1312159
NSFDMS-1009213
Office of Naval Research (ONR)N-00014-09-1-0458
NSFCMG-1024198
Subject Keywords:internal waves, ocean processes, quasi-geostrophic flows
Record Number:CaltechAUTHORS:20180112-100115650
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20180112-100115650
Official Citation:Bühler, O., Callies, J., & Ferrari, R. (2014). Wave–vortex decomposition of one-dimensional ship-track data. Journal of Fluid Mechanics, 756, 1007-1026. doi:10.1017/jfm.2014.488
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:84295
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:12 Jan 2018 19:32
Last Modified:09 Oct 2019 19:32

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