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Responses to topographical forcing

Published online by Cambridge University Press:  26 April 2006

Wolfgang Fennel  and
Martin Schmidt
Wolfgang Fennel
Affiliation:
Academy of Sciences of GDR, Institute of Marine Research, Rostock-Warnemünde, DDR-2530
Martin Schmidt
Affiliation:
Academy of Sciences of GDR, Institute of Marine Research, Rostock-Warnemünde, DDR-2530
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Abstract

The influence of small topographic features on the dynamic responses of an inviscid, stratified, f-plane ocean to a time-dependent upstream flow is studied. Based on the quasi-geostrophic vorticity equation we analyse a quasi-nonlinear approach, in which the horizontal currents in the advection terms are replaced by the upstream flow. It appears that the quasi-nonlinear theory is susceptible to analytical treatment and contains the essential dynamics to give a sufficient description of the response scenario. As examples, infinitely long ridges and a right-circular cylinder are considered. In the case of an infinitely long top-hat ridge closed-form expressions can be derived. In the case of a cylindrical obstable the theory gives explicit indications of which term corresponds to which of the processes involved, such as topographic waves, which are generated in the starting phase and move clockwise round the obstacle, vortex shedding, and formation of a vortex over the cylinder in the final steady state.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 223 , February 1991 , pp. 209 - 240
Copyright
© 1991 Cambridge University Press

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