Rossby waves and zonal momentum redistribution induced by localised forcing in the rotating shallow-water model
File(s)
Accepted version
Author(s)
Haigh, Michael
Berloff, Pavel
Type
Journal Article
Abstract
The aim of this study is to understand the dynamics of Rossby waves induced by a localised and periodic ‘plunger’ forcing – imposed on a background flow – which is intended as an elementary representation of transient mesoscale eddy forcing in the ocean. We consider linearised dynamics and its quasi-nonlinear extension, and focus on the rotating shallow-water model. The plunger induces a spectrum of Rossby waves that drive zonal momentum flux convergence at the forced latitudes. This behaviour has a robust and significant dependence on the background flow, which we treat as zonal and uniform. We systematically analyse this dependence using two methods. First, we use the eddy geometry formulation, in which Reynolds stresses are expressed in terms of eddy elongation and eddy tilt parameters, and consider the relationship between eddy geometry and zonal momentum redistribution. Second, we implement decompositions of flow responses into linear dynamical eigenmodes and compare with expectations from linear Rossby wave theory. Both methods compliment each other and aid the understanding of zonal momentum redistribution and its dependence on uniform background flow. We find that this dependence is determined by two factors: (i) dispersion-constrained resonance with the plunger forcing and (ii) efficiency of nonlinear eddy self-interactions. These results significantly improve our understanding of shallow-water Rossby waves, and may also be applied towards the development of parameterisations of oceanic mesoscale eddies.
Date Issued
2020-02-25
Date Acceptance
2019-12-06
Citation
Journal of Fluid Mechanics, 2020, 885, pp.A43-1-A43-26
ISSN
0022-1120
Publisher
Cambridge University Press (CUP)
Start Page
A43-1
End Page
A43-26
Journal / Book Title
Journal of Fluid Mechanics
Volume
885
Copyright Statement
© The Author(s), 2020. Published by Cambridge University Press. This paper has been accepted for publication and will appear in a revised form, subsequent to peer-review and/or editorial input by Cambridge University Press.
Identifier
http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000505829000001&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=1ba7043ffcc86c417c072aa74d649202
Subjects
Science & Technology
Technology
Physical Sciences
Mechanics
Physics, Fluids & Plasmas
Physics
shallow water flows
waves in rotating fluids
SPECTRAL-ANALYSIS
EDDY
DRIVEN
PROPAGATION
RADIATION
Publication Status
Published
Article Number
ARTN A43
Date Publish Online
2020-01-07