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Frictional coastal trapped waves in a two-layered ocean

Published online by Cambridge University Press:  21 April 2006

Humio Mitsudera  and
Kimio Hanawa
Humio Mitsudera
Affiliation:
School of Mathematics, University of NSW, P.O. Box 1, Kensington, NSW 2033, Australia
Kimio Hanawa
Affiliation:
Department of Geophysics, Faculty of Science, Tohoku University, Sendai 980, Japan
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Abstract

The effects of bottom friction on coastal trapped waves were investigated using an f-plane, two-layer model including shelf-slope topography. At a change-over latitude where the phase speeds of the internal Kelvin wave and the continental-shelf wave coincide, there are two types of behaviour of the ‘frictional’ eigenvalue (the phase speed and the damping rate) and the eigenfunctions, in terms of the inertial frequency f: if the frequency ω is large, wave characteristics change from one wave to another with f (Case II); while if ω is small enough, the wave characteristics do not change (Case II). In actual environments, it is predicted that the weather-band phenomena (period 2 days to 2 weeks) correspond to Case I, and very low-frequency (VLF) phenomena such as signals of El Niño along the American Continent correspond to Case II. Further, for baroclinic VLF waves, it is found that bottom friction retards the lower-layer velocity, which causes a decrease in damping. Therefore, the VLF signals caused by El Niño can travel far from their origin, overcoming the effect of bottom friction. A bottom-intensified structure in barotropic VLF waves, due to bottom friction, has also been found.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 198 , January 1989 , pp. 453 - 469
Copyright
1989 Cambridge University Press

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