Tales of the QBO, effects on the wintertime tropospheric flow and stratospheric-tropospheric dynamical coupling.

The Quasi-Biennial Oscillation (QBO) is one of the most consistent modes of climate variability, made up of a quasi-periodic oscillation between downward propagating easterlies and westerlies in the equatorial stratosphere. Yet, its influence on global climate variability is uncertain, and it is still poorly represented in high-top climate models that attempt to include a prognostic QBO.

I will provide an overview of recent work by my research group and collaborators on the effect of the QBO on atmospheric teleconnections and the mechanisms of this effect, going beyond the stratosphere-only centric view. In particular, based on our analysis of the effect of the QBO in reanalysis data, we hypothesize that the QBO modulates the midlatitude tropospheric flow making it more or less conducive to vertical Rossby-wave propagation into the stratosphere where stratospheric processes come into play leading to stratospheric-tropospheric dynamical coupling.

I will report on long perturbation experiments with the Specified Chemistry Whole Atmosphere Community Climate Model (SC-WACCM) with a prescribed QBO and where we use nudging to control the flow in certain regions in order to isolate processes.