Extratropical teleconnections in an ensemble of models nudged towards the observed equatorial QBO

The Quasi-Biennial Oscillation (QBO) is the leading natural model of interannual variability of the zonal mean wind in the equatorial stratosphere, consisting of alternating regions of easterly and westerly zonal wind that descend through the equatorial stratosphere with a mean period of approximately 28 months. Its dominant influence on the dynamical structure of the equatorial stratosphere raises the prospect of teleconnections to the extratropical atmosphere. For example, the QBO has been linked to variability in the Northern Hemisphere winter stratospheric polar vortex, the timing and frequency of sudden stratospheric warmings, the phase of the North Atlantic Oscillation, and the modulation of tropospheric mid-latitude waves in the Pacific region. However, the reproduction of these extratropical teleconnections in free-running models relies upon on a quantitatively realistic internally-generated QBO, and the ability of the model dynamics to respond to this QBO. To isolate the dynamical response, a new experiment protocol, defined by the Atmospheric Processes and their Role in Climate (APARC) Quasi-Biennial Oscillation initiative (QBOi), describes how the observed equatorial stratospheric zonal winds can be imposed in model experiments. This allows the dynamical response across different models with similar and realistic QBOs to be analysed. Using a multi-model ensemble generated by QBOi modelling centres, we present an assessment of the extratropical teleconnections in comparison with observations.