The effect of sloping boundaries on baroclinic instability in two related internally heated, rotating fluid systems

Journal article

Results have been obtained from two internally heated, rotating fluid systems with differing aspect ratios, in which a β-effect (variation in Coriolis parameter with latitude) has been simulated by the inclusion of oppositely sloping endwalls. The boundaries are arranged so that the fluid depth (D) can either increase with radius (partial differential D/partial differential r > 0) or decrease with radius (partial differential D/partial differential r < 0). In both systems, stable eddy features are observed over a wide range of rotation rates for each endwall arrangement. While a large number of different azimuthal wavenumber (m) modes are seen in the regular wave regime of the partial differential D/partial differential r > 0 endwall experiments, only the gravest mode (m = 1) is seen in the regular wave regime of the partial differential D/partial differential r < 0 endwall experiments. Within the former experimental arrangement, the radial scale of the eddy features is shown to be approximately that of the Rhines scale [equation], while in the partial differential D/partial differential r < 0 endwall experiments the eddy kinetic energy is seen to penetrate the L(β) scale and accumulate at the largest domain-filling scales. This remarkable difference in the flow structure of the two endwall arrangements may find a partial explanation in terms of established results on the instability of finite amplitude barotropic Rossby waves, where partial differential D/partial differential r < 0 endwalls remove the stability thresholds on wave amplitudes for all but the gravest mode.

Authors: Bastin, M; Read, P

• Publication status: Published
• Journal: PHYSICS AND CHEMISTRY OF THE EARTH PART B-HYDROLOGY OCEANS AND ATMOSPHERE
• Volume: 24
• Issue: 5
• Pages: 481-486
• Publication date: 1999-01-01
• DOI: 10.1016/S1464-1909(99)00033-7
• ISSN: 1464-1909
• Language: English