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| Titel |
Eddy-driven jets and vortices in convectively forced geostrophic turbulence on a topographic beta-plane |
| VerfasserIn |
Peter L. Read, Tom Jacoby, Peter Rogberg, Yasuhiro Yamazaki, Kuniko Miki-Yamazaki, Robin Wordsworth, Roland Young, Joel Sommeria, Henri Didelle, Samuel Viboud |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250037497
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| Zusammenfassung |
| We present here new results from large-scale laboratory experiments on forced-dissipative
geostrophic turbulence in a large rotating tank. In an earlier series of experiments, small-scale
convection was driven by a steady flux of dense salty water onto the top surface of a rotating
water tank. In the new work, convection was driven by continuous direct heating of the lower
boundary. The whole tank rotates at constant angular velocity Ω and dynamical effects
equivalent to the spherical curvature of a planetary atmosphere are emulated by use of a
radially-sloping bottom. The experiments were carried out on the 13 m diameter rotating
Coriolis platform in Grenoble, France. Results demonstrate the formation of multiple,
undulating, parallel, barotropic zonal jets, in which u′v′ fluxes maintain the jets
against viscous (Ekman) dissipation. In the new experiments, use of widely different
rotation rates of the tank confirms the dual role of planetary vorticity gradients
(β) and bottom friction in governing the jet separation scale, approximated by the
well-known Rhines scale (LR = Ï(2U-β)1-2) under certain conditions. The jets formed
are also frequently found robustly to violate the Rayleigh-Kuo barotropic stability
criterion, leading to formation of larger-scale waves and eddies and influencing the
kinetic energy spectrum. These experiments serve to elucidate mechanisms for jet
formation and saturation that may apply to gas giant planet atmospheres and, more
controversially, the terrestrial oceans, and suggest a number of new diagnostics to be
investigated in observations and models of both Jovian and terrestrial ocean circulations. |
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