The asymptotic theory of the generation of long-wave structures in critical layers of weakly dissipative jet flows |
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| Authors: | S V Shagalov V P Reutov G V Rybushkina |
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| Institution: | 1.Institute of Applied Physics,Russian Academy of Sciences,Nizhni Novgorod,Russia |
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| Abstract: | The mechanisms of the large-scale vortex structures formation in zonal jet flows (atmospheric blockings, cyclonic, and anticyclonic
vortices) is investigated. Nonlinear perturbations formed during the onset of barotropic instability of a long-wave mode in
weakly-dissipative and weakly supercritical jet flows with a symmetric velocity profile are considered in the β-plane approximation.
This analysis is performed within the framework of the asymptotic theory based on the concept of a nonlinear critical layer.
The equations describing the interaction of a wave with vorticity perturbations in a critical layer are derived. The regimes
of a quasi-stationary and nonstationary nonlinear critical layer are considered separately. Combined equations of evolution
covering the principle regimes of instability development are proposed. The existence of autowave-type structures characterized
by a balance between the energy receipt to the wave and its dissipation are obtained within the framework of a numerical simulation.
The dependence of the parameters of generated autowave structures on the shape of the zonal jet profile and the flow supercriticality
level is studied. |
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