标题： 热带气旋模型中的斜压定常波 显示英文标题

标题： Baroclinic stationary waves in aquaplanet models

摘要： 使用一个水行星模型来研究在由纬向对称边界条件强迫的模型中观测到的高持续性低频波的性质。 通过哈亚希（Hayashi）对中纬度波动的谱分析，我们发现准静止（QS）波五属于一个遵循明确色散关系并具有向东群速度的波包。 色散关系的k>5成分会将涡旋可用位能转化为涡旋动能，而k<5的成分则为斜压中性。 与格林（Green）的斜压不稳定性模型一致，波五是弱不稳定的，之前被认为是对这类波动的主要强迫的反向能量级联，仅在其主要斜压能量学中起到正反馈作用。 准静止波通过与热带对流中的类似模式相位锁定得到增强，这进一步放大了该波。 我们还发现，Pedlosky对不稳定波相速的限制为解释能量转换的纬度结构提供了指导，该结构被证明在纬向西风表面风较弱的地方更为增强。 随后，波能被截留在高层对流层急流形成的波导中。 与格林理论一致，随着赤道至极地海表温度差异的减小，准静止的临界稳定成分向更高波数移动，而波五则变为中性并向西传播。 在水行星准静止波的一些特性与萨尔比（Salby）（1982年）在南半球冬季（DJF）观测到的低频波有趣地一致，因此，这种对低频变化的视角除了在基础地球物理流体力学方面的价值外，对于研究地球大气也具有特殊意义。 显示英文摘要

摘要： An aquaplanet model is used to study the nature of the highly persistent low frequency waves that have been observed in models forced by zonally symmetric boundary conditions. Using the Hayashi spectral analysis of the extratropical waves, we find that a quasi-stationary (QS) wave five belongs to a wave packet obeying a well defined dispersion relation with eastward group velocity. The components of the dispersion relation with k>5 baroclinically convert eddy available potential energy into eddy kinetic energy, while those with k<5 are baroclinically neutral. In agreement with the Green's model of baroclinic instability, the wave five is weakly unstable, and the inverse energy cascade, which had been previously proposed as a main forcing for this type of waves, only acts as a positive feedback on its predominantly baroclinic energetics. The QS wave is reinforced by a phase lock to an analogous pattern in the tropical convection, which provides further amplification to the wave. We also find that the Pedlosky bounds on the phase speed of unstable waves provide guidance in explaining the latitudinal structure of the energy conversion, which is shown to be more enhanced where the zonal westerly surface wind is weaker. The wave energy is then trapped in the wave guide created by the upper tropospheric jet stream. In agreement with Green's theory, as the equator to pole SST difference is reduced the stationary marginally stable component shifts toward higher wavenumbers, while the wave five becomes neutral and westward propagating. Some properties of the aquaplanet QS waves are found in interesting agreement with a low frequency wave observed by Salby (1982) in the southern hemisphere DJF, so that this perspective on low frequency variability might be, apart from its value in terms of basic geophysical fluid dynamics, of specific interest for studying the Earth's atmosphere.