Results show that for western Canada, El Niņo events are associated with a significant reduction in the frequency of cold spells, and a significant increase in the frequency of warm spells. During these events, the duration of warm spells increase throughout most of southern Canada, while the number of cold days (warm days) decrease (increase) from British Columbia to the Great Lakes. The high index phase of the AO is related to increases in both the frequency and the duration of winter cold spells in eastern Canada. The coupling between the stratospheric circulation and the climatic extremes are also examined by compositing the number of winter cold and warm days according to the two phases of the QBO. When compared to the westerly phase, the easterly phase of the QBO favors more cold days in western Canada and fewer cold days along the east coast of Canada.
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