Modeling Interannual Climate Variability of the Winter Stratosphere

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The Southern Oscillation (SO) and the equatorial quasi- biennial oscillation (QBO) are related to significant interannual variability in the extratropical winter troposphere and especially, stratosphere. This research will examine the relative roles of the QBO and SO in crating winter-season climate anomalies on interannual timescales. A "deep" 26-level climate version of the NCAR general circulation model (Community climate Model) will be used to examine the trosphere-stratosphere system with the object of providing a unified view of interannual wintertime climate variability and its relation to the SO or QBO. The SO and QBO are viewed as interannually varying external forcing agents for the extratropical winter hemisphere. Since winter-season interannual variability is grater in the stratosphere than the troposphere, the research will concentrate on the stratospheric climate anomalies. By using a general circulation model, it is intended to isolate mechanisms capable of communicating the tropical forcing anomalies, SO or QBO, to the extratropical winter atmosphere, and two such mechanisms are proposed. Separate winter season integrations under opposite extremes of the SO or QBO will be performed to determine the atmospheric responses to the SO and QBO. Such information is especially important in the stratosphere where it has not been possible to distinguish clearly between the effects of the SO and the QBO in the observational climate record.