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An experimental and numerical study of the secular spin-up of a thermally stratified rotating fluid

Published online by Cambridge University Press:  19 April 2006

Robert C. Beardsley
Affiliation:
Woods Hole Oceanographic Institution, Woods Hole, Mass. 02543
Kim D. Saunders
Affiliation:
Department of Meteorology, Massachusetts Institute of Technology, Cambridge, Mass. 02139 Present affiliation: NORDA (Code 331), NSTL Building 1100, Bay St Louis, Miss. 39529.
Alex C. Warn-Varnas
Affiliation:
Naval Ocean Research and Development Activity, NSTL, Bay St Louis, Miss. 39529
John M. Harding
Affiliation:
Naval Ocean Research and Development Activity, NSTL, Bay St Louis, Miss. 39529

Abstract

Laboratory and numerical experiments have been conducted to study the secular spin-up of both a homogeneous and a thermally stratified rotating fluid in a right cylinder. In these experiments, the angular velocity of the container increases linearly in time from some initial rotation rate at t = 0. A simple quasi-geostrophic model is developed to describe the adjustment of the fluid over the characteristic spin-up time scale to the constant angular acceleration of the basin. Good agreement is found between the observed interior temperature and azimuthal velocity fields and the theory in both the homogeneous and stratified secular experiments. This result is in contrast to the much faster adjustment observed in stratified instantaneous spin-up experiments reported earlier. The main difference between these experimental cases is the inability of secular forcing to excite energetic inertial–gravity-wave transients during the initial phases of secular spin-up. Thus, the asymptotic theory which has filtered out these initial higher-frequency transients is accurate even though the inertial period is not much smaller than the characteristic spin-up time scale.

Type
Research Article
Copyright
© 1979 Cambridge University Press

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