Purpose of Review

While the influence of climate change on mid-latitude atmospheric circulation remains uncertain, hypotheses based on linear waveguide dynamics have been proposed suggesting amplification of circumglobal quasi-stationary Rossby wave events, which may have led to persistent and high-impact extremes in recent boreal summers. It is thus useful to synthesize these hypotheses and to discuss limitations of this simplified dynamical framework for explaining observed features.

Recent Findings

The hypothesis that climate change can alter the basic circulation state and thereby enhance circumglobal waveguide teleconnections by increasing their resonance has been proposed but has not yet been verified with models. Furthermore, there is no convincing evidence that the variability of disturbances within the waveguide will increase in future climates projected by the CMIP5 models. On the other hand, recent research indicates that enhanced diabatic heating, particularly that associated with increasing aridity in the mid-latitude, can stimulate the jet stream waveguides, thus suggesting an alternative mechanism which, if properly modeled, could lead to more high-amplitude circumglobal planetary wave events.

Summary

There could be circumstances that lead to resonant amplification of waveguide Rossby waves in the boreal summer, but an alternative mechanism that involves changes in the forcing rather than the mean state deserves closer attention.

中文翻译：

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北半球夏季波导遥相关的放大

审查目的

虽然气候变化对中纬度大气环流的影响仍然不确定，但基于线性波导动力学的假设已经提出，表明环全球准稳态罗斯贝波事件的放大，这可能导致最近北半球夏季持续且高影响的极端事件。因此，综合这些假设并讨论这种简化的动力学框架对于解释观察到的特征的局限性是有用的。

最近的发现

气候变化可以改变基本环流状态，从而通过增加共振来增强环波导遥相关的假设已经被提出，但尚未得到模型的验证。此外，没有令人信服的证据表明波导内扰动的变异性会在 CMIP5 模型预测的未来气候中增加。另一方面，最近的研究表明，增强的非绝热加热，特别是与中纬度地区日益干旱相关的非绝热加热，可以刺激急流波导，从而提出了一种替代机制，如果正确建模，可能会导致更高的振幅环全球行星波事件。

概括

在北半球夏季，可能存在导致波导罗斯贝波共振放大的情况，但涉及强迫而不是平均状态变化的替代机制值得密切关注。