Abstract The role of planetary-scale zonally-asymmetric thermal forcing on large-scale atmospheric dynamics is crucial for understanding low-frequency phenomena in the atmosphere. Despite its paramount importance, good theoretical foundation for the understanding is still lacking. Here, we address this issue by providing a general framework for including planetary-scale thermal forcing in large-scale atmospheric dynamics studies. This is accomplished by identifying two distinct geostrophic motions of horizontal length scale L in terms of the external Rossby deformation length scale LD : i) and ii) where ϵ is the Rossby number. In addition, via multi-scale analysis, we show that the large-scale atmospheric dynamics can be described by mutual interaction between the two scales. The analysis results in planetary geostrophic equations with large-scale thermal forcing that provide the basic balanced states for processes such as the growth of synoptic waves. In the long-time limit, the continuous growth and decay of synoptic waves provide the convergence of horizontal heat and vorticity fluxes, which contributes to the energy flux balance in the planetary geostrophic scale with planetary-scale advection and thermal forcing.

中文翻译：

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与准地转动力学的行星尺度运动一致的平衡状态

摘要 行星尺度纬向不对称热强迫对大尺度大气动力学的作用对​​于理解大气中的低频现象至关重要。尽管它非常重要，但仍然缺乏良好的理解理论基础。在这里，我们通过提供将行星尺度热强迫纳入大规模大气动力学研究的一般框架来解决这个问题。这是通过根据外部罗斯比变形长度尺度 LD 确定水平长度尺度 L 的两个不同地转运动来实现的：i) 和 ii) 其中 ϵ 是罗斯比数。此外，通过多尺度分析，我们表明大尺度大气动力学可以通过两个尺度之间的相互作用来描述。分析产生了具有大规模热强迫的行星地转方程，为天气波的增长等过程提供了基本的平衡状态。在长时间范围内，天气波的不断增长和衰减提供了水平热量和涡量通量的汇聚，这有助于行星尺度平流和热强迫在行星地转尺度上的能量通量平衡。