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The evolution of superharmonics excited by internal tides in non-uniform stratification

Published online by Cambridge University Press:  20 March 2020

Lois E. Baker Open the ORCID record for Lois E. Baker [Opens in a new window]  and
Bruce R. Sutherland Open the ORCID record for Bruce R. Sutherland [Opens in a new window]
Lois E. Baker*
Affiliation:
Department of Civil and Environmental Engineering, Imperial College London, LondonSW7 2AZ, UK
Bruce R. Sutherland
Affiliation:
Departments of Physics and of Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB T6G 2E1, Canada
*
† Email address for correspondence: leb18@ic.ac.uk
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Abstract

A weakly nonlinear time-dependent theory for the evolution of superharmonics generated by the nonlinear self-interaction of a mode-1 internal tide in non-uniform stratification is developed and compared to numerical simulations. The forcing by the internal tide is found to excite near-pure mode-1 superharmonics whose natural frequency is moderately different from twice the internal tide frequency. Consequently, the superharmonics undergo a slow periodic growth and decay that is comparable to an acoustic ‘beat’. At low latitudes the beat frequency is smaller and the superharmonics can grow to larger amplitude, allowing for the possibility of a superharmonic cascade.

JFM classification

Geophysical and Geological Flows: Internal waves Geophysical and Geological Flows: Waves in rotating fluids
Type
JFM Rapids
Information
Journal of Fluid Mechanics , Volume 891 , 25 May 2020 , R1
Copyright
© The Author(s), 2020. Published by Cambridge University Press

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