Baroclinic instability of a flow with a constant vertical shear in a zonal channel has been studied. The maximally truncated SQG model was used to describe the dynamics of flow disturbances. A dynamic system describing nonlinear interactions between unstable counter‐propagating Rossby waves with one zonal wave number and a neutral mode independent of zonal coordinate has been formulated within the framework of this model. Both analytical and numerical solutions of the system show that exponentially increasing disturbances at the linear stage of instability development give way to nonlinear oscillations (vacillations). The occurrence of such oscillations is caused by the law of conservation of surface potential energy. According to numerical estimates, the period of oscillations is of the order of a month, which is in agreement with measurement data obtained for the winter atmosphere.

中文翻译：

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截断SQG模型中的斜压不稳定性和非线性振荡

已经研究了带状通道中具有恒定垂直剪切力的斜压不稳定性。最大截断的SQG模型用于描述流动扰动的动力学。在该模型的框架内，已经建立了一个动力学系统，该动力学系统描述了具有一个带状波数的不稳定反向传播的Rossby波与独立于带状坐标的中性模之间的非线性相互作用。该系统的解析解和数值解均表明，在不稳定发展的线性阶段，呈指数级增长的扰动被非线性振荡（波动）所取代。这种振荡的发生是由表面势能守恒定律引起的。根据数值估算，振荡周期约为一个月，