Unstably stratified geophysical fluid dynamics |
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Authors: | Jun-Ichi Yano ,Joë l Sommeria |
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Affiliation: | aNCAR, P.O. Box 3000, Boulder, CO 80307-3000, USA;bLaboratoire de Physique (C.N.R.S. URA 1325), Ecole Normale Supérieure de Lyon, 46, al. d'Italie, Lyon Cedex 69364, France |
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Abstract: | The linear dynamics of the unstably stratified geophysical flows is investigated with a two-layer formulation. A ‘convective’ deformation radius classifies the dynamics into three regimes: 1. 1. the scales smaller than the deformation radius: the dynamics characterized by unstable inertial-gravity modes; | 2. 2. the scales larger than the deformation radius: a quasi-geostrophic regime; | 3. 3. the scales close to the deformation radius, where the dynamics transits from the inertial-gravity regime to the quasi-geostrophic regime. | The Rossby wave can propagate eastward in the unstably stratified quasi-geostrophic regime. The baroclinic instabilities are basically realized as a larger-scale extent of the inertial-gravity instabilities, but the former can be isolated from the latter in a limit of small β-effect, with a very deep lower layer. The results suggest that the convectively unstable Jovian atmospheric dynamics can be well described as a quasi-geostrophic system. |
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