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Meridional trapping and zonal propagation of inertial waves in a rotating fluid shell

Published online by Cambridge University Press:  24 July 2013

Anna Rabitti  and
Leo R. M. Maas
Anna Rabitti*
Affiliation:
Department of Physical Oceanography, NIOZ Royal Netherlands Institute for Sea Research, PO Box 59, 1790 AB Texel, The Netherlands
Leo R. M. Maas
Affiliation:
Department of Physical Oceanography, NIOZ Royal Netherlands Institute for Sea Research, PO Box 59, 1790 AB Texel, The Netherlands
*
†Email address for correspondence: [email protected]
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Abstract

Inertial waves propagate in homogeneous rotating fluids, and constitute a challenging and simplified case study for the broader class of inertio-gravity waves, present in all geophysical and astrophysical media, and responsible for energetically costly processes such as diapycnal and angular momentum mixing. However, a complete analytical description and understanding of internal waves in arbitrarily shaped enclosed domains, such as the ocean or a planet liquid core, is still missing. In this work, the inviscid, linear inertial wave field is investigated by means of three-dimensional ray tracing in spherical shell domains, having in mind possible oceanographic applications. Rays are here classically interpreted as representative of energy paths, but in contrast to previous studies, they are now launched with a non-zero initial zonal component allowing for a more realistic, localized forcing and the development of azimuthal inhomogeneities. We find that meridional planes generally act in the shell geometry as attractors for ray trajectories. In addition, the existence of trajectories that are not subject to meridional trapping is here observed for the first time. Their dynamics was not captured by the previous purely meridional studies and unveils a new class of possible solutions for inertial motion in the spherical shell. Both observed behaviours shed some new light on possible mechanisms of energy localization, a key process that still deserves further investigation in our ocean, as well as in other stratified, rotating media.

JFM classification

Geophysical and Geological Flows: Geophysical and Geological Flows Geophysical and Geological Flows: Internal waves Geophysical and Geological Flows: Waves in rotating fluids
Type
Papers
Information
Journal of Fluid Mechanics , Volume 729 , 25 August 2013 , pp. 445 - 470
Copyright
©2013 Cambridge University Press 

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