QBO variability and its effect on the extratropical circulation in a GCM

The influence of the QBO on the extratropical stratospheric circulation during Northern Hemisphere winter is investigated using a GCM, the Canadian Middle Atmosphere Model (CMAM). Observations have suggested that the correlation between tropical winds and polar temperatures may be modulated by the 11 year solar cycle. Our model, which achieves a spontaneous QBO-like oscillation due to enhancements in both vertical resolution as well as forcing due to parameterized gravity waves, exhibits long-timescale variations in QBO phase durations and in the timing of phase transitions with respect to the seasonal cycle. These variations are found to affect the strength and timing of tropical-extratropical correlations. As our model does not contain an 11-year solar cycle, or interannually varying SSTs, this effect is an internal mode of variability of our GCM.