Symmetric Baroclinic Instability of Modified Hadley-Cell Models

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A numerical investigation is made of symmetric instability of baroclinic flows in a finite domain of horizontal fluid layer. A modified rotating Hadley-cell flow configuration is designed to achieve Ri&gne0 (1) by constructing two models, i.e., in Model I, ΔT_v=0; and in Model II, the free-slip and thermally-insulated upper boundary is adopted. A finite-volume numerical procedure is utilized to integrate the fully-nonlinear time-dependent Navier-Stokes equations over broad parameter ranges, i.e., the thermal Rossby number 1.0&gneRo&gne40.0,and the Richardson number 0.2&gneRi&gne2.0. The Ro-Ri diagram illustrates three flow regimes : (1) the stable flow regime with respect to the symmetric baroclinic instability, (2) the steady symmetric baroclinic wave regime, and (3) the vacillating symmetric baroclinic wave regime. The critical Richardson number for stability is determined and overall energetics of finite amplitude symmetric baroclinic waves are illustrated. The large-time behavior of wave generation is examined, and a plausible physical interpretation is offered. Both the time-dependent characteristics and the energetics of the vacillating symmetric baroclinic waves are scrutinized. Discussions are given on the impact of the nonlinear effects of symmetric baroclinic waves on the basic-state flow field.
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