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Seeking a mechanistic understanding of the linear interference effect in stratosphere-troposphere coupling

Interactions between the stratosphere and troposphere can influence the evolution of extra-tropical weather during the Northern Hemisphere winter. For example, it has been shown that under certain conditions, knowledge of the state of the stratosphere can increase seasonal-timescale predictability at the surface. However, the precise mechanisms of this stratosphere-troposphere coupling are not fully understood. I aim to gain a better dynamical understanding of the linear interference effect, which is the observation that the relative phasing between a perturbation anomaly and the background stationary wave pattern explains a large part of the subsequent forcing on the stratosphere.

In this talk, I will introduce some basic ideas of stratosphere-troposphere coupling, and in particular the linear interference effect. I will explain how the wavenumber-frequency spectral decomposition can be used to separate disturbances into standing and travelling waves. Applying this technique to reanalysis data and a number of general circulation model simulations, I will show that there is a consistent relationship between the phase of the stationary wave pattern and the phase of the predominant standing waves. This may have implications for better understanding the linear interference effect.