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首页> 外文期刊>Journal of the Atmospheric Sciences >Baroclinic instability in an Euler equations-based column model: The coexistence of a deep synoptic-scale mode and shallow subsynoptic-scale modes
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Baroclinic instability in an Euler equations-based column model: The coexistence of a deep synoptic-scale mode and shallow subsynoptic-scale modes

机译：基于欧拉方程的圆柱模型中的斜压不稳定性：深天气尺度模式和浅亚天气尺度模式并存

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The authors provide a detailed analysis of a shallow mode of subsynoptic-scale baroclinic instability by analyzing a one-dimensional column model in which the assumption of balance is applied to the basic-state flow but in which nongeostrophic unbalanced effects are retained in the description of the evolution of the perturbation under the Boussinesq approximation. This model is employed to analyze the stability of a meridionally confined mean state that is based upon hydrodynamic fields extracted from the central columns of a tropospheric cross section of the midlatitude jet stream. Numerical solutions are obtained at very high resolution through application of a sparse matrix method for solution of the corresponding cubic eigenvalue problem. Thereby the existence of a deep synoptic-scale mode and boundary-confined subsynoptic-scale modes is confirmed. The spatial scale and phase speed of these modes agree with those previously obtained on the basis of both nonseparable stability analysis and solution of the associated initial value problem in the companion paper by Yamazaki and Peltier. Both one-dimensional and nonseparable shallow modes share the property that they are characterized by the presence of an inertial critical layer, and the lack of a short-wave cutoff of the subsynoptic-scale modes suggested by analyses of the nonseparable models is more clearly shown in the column model. However, the growth rate of the shallow mode in the column model is approximately 1 order of magnitude smaller than those of the structures delivered by the nonseparable analyses, and the vertical structure and the energy budget of these modes vary dramatically depending on the sign of the meridional wavenumber that determines the direction of meridional propagation. [References: 20]
机译：作者通过分析一维圆柱模型来对亚天气尺度斜压不稳定的浅层模式进行详细分析，在该模型中，平衡的假设适用于基态流动，但在描述中保留了非地转不平衡效应。 Boussinesq近似下摄动的演化。该模型用于分析子午受限平均状态的稳定性，该状态基于从中纬度射流对流层横截面的中心列提取的流体动力场。通过应用稀疏矩阵方法求解相应的三次特征值问题，可以以很高的分辨率获得数值解。从而证实了深天气尺度模式和边界约束的亚天气尺度模式的存在。这些模式的空间尺度和相速度与先前在Yamazaki和Peltier的同伴论文中基于不可分的稳定性分析和相关的初值问题的解决方案所获得的那些相符。一维模式和不可分离的浅模式都具有以下特性：惯性临界层的存在，更清楚地显示了不可分离模型的分析所暗示的亚天气尺度模式的短波截止在列模型中。但是，柱模型中的浅模式的增长率比不可分分析所传递的结构的增长率小大约1个数量级，并且这些模式的垂直结构和能量收支会根据结构的符号而显着变化。确定子午线传播方向的子午波数。 [参考：20]

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