Modulation of Southern Oscillation-Northern Hemisphere Mid-Winter Climate Relationships by the QBO

Abstract

A possible relationship between the phase of the Quasi-Biennial Oscillation (QBO) and the effect of the Southern Oscillation (SO) on the January-February climate in the Northern Hemisphere is examined. Findings suggest a preference for the tropical/Northern Hemisphere (TNH) circulation pattern in response to anomalies in the SO in east QBO phase years, and for the Pacific/North American (PNA) pattern in west QBO phase years. This extends previous findings relating the strength of the TNH pattern to tropical Pacific sea surface temperature during ENSO episodes. This differentiation has fairly clear-cut implications for the January-February United States surface temperature anomaly pattern when a low (high) SO episode is in progress. The TNH emphasizes warmth (cold) in the Great Lakes/western Midwest; whereas the PNA induces a generally higher amplitude pattern, emphasizing cold (warmth) in the Southeast and warmth (cold) in the western third of the country. The SO-climate relationships appear approximately linear for each of the two QBO phases. A hypothetical physical mechanism through which this process might operate is briefly mentioned.