Surface impacts of the Quasi Biennial Oscillation
Atmospheric Chemistry and Physics Discussions
Teleconnections between the Quasi Biennial Oscillation (QBO) and the Northern Hemisphere zonally-averaged zonal winds, mean sea level pressure (mslp) and tropical precipitation are explored using regression analysis. A novel technique is introduced to separate responses associated with the stratospheric polar vortex from other underlying mechanisms. A previously reported mslp response in January, with a pattern that resembles the positive phase of the North Atlantic Oscillation (NAO) under QBO
... on (NAO) under QBO westerly conditions, is confirmed and found to be primarily associated with a QBO modulation of the stratospheric polar vortex. This mid-winter response is relatively insensitive to the exact height of the maximum QBO westerlies and a maximum response occurs with westerlies over a relatively deep range between 10&ndash;70&thinsp;hPa. Two additional mslp responses are reported, in early winter (December) and late winter (February/March). In contrast to the January response the early and late winter responses show maximum sensitivity to the QBO winds at ~&thinsp;20&thinsp;hPa and ~&thinsp;70&thinsp;hPa but are relatively insensitive to the QBO winds in between (~&thinsp;50&thinsp;hPa). The late winter response is centred over the North Pacific and is associated with QBO influence from the lowermost stratosphere at tropical/subtropical latitudes. The early winter response consists of anomalies over both the North Pacific and Europe, but the mechanism is unclear and requires further investigation. QBO anomalies are found in tropical precipitation amounts and a southward shift of the Inter-tropical Convergence Zone under westerly QBO conditions is also evident.