FLOW DYNAMICS IN THE 'SLICED CONE' MODEL OF WIND-DRIVEN OCEAN CIRCULATION

摘要

The 'sliced cone' laboratory model was introduced by Griffiths and Veronis (1997) (hereafter, GV97) to investigate the effect of sloping sidewalls on homogeneous wind-driven flow on a β-plane. This model is a variant of the 'sliced cylinder' model of Pedlosky and Greenspan (1967) in which the vertical sidewalls have been replaced by an azimuthally uniform slope around the perimeter of the basin. This modification has the twin effects of closing the basin's geostrophic contours and of largely removing the lateral dissipation of vorticity at the boundaries, leaving Ekman friction as the dominant dissipation mechanism. The laboratory flows observed by GV97 showed a dramatic difference in stability depending on the sign of the simulated wind stress curl. Flows produced by anticyclonic forcing were unsteady even for very weak forcing, and displayed eddy-shedding instabilities under stronger forcing. In contrast, the flow driven by cyclonic forcing was stable and steady under all conditions investigated. This paper presents results of a numerical study of this system, which clarifies the dynamics of the observed flows and offers an explanation for the dependence of stability on the sign of the wind stress curl.