November 12, 2009

Chaim Garfinkel

The QBO's Influence on the North Pacific and ENSO Teleconnections

Abstract

Reanalysis and model data are used to study El-Niño Southern Oscillation's (ENSO) teleconnections in the North Pacific during Northern Hemisphere winter. Warm ENSO (WENSO) events have a significantly stronger teleconnection when the Quasi-Biennial Oscillation (QBO) is in its westerly phase relative to its easterly phase at 50hPa in both the reanalysis record and in the Whole Atmosphere Community Climate Model (WACCM). Composites of easterly QBO (EQBO) at 50hPa show an anomalous ridge over the North Pacific, which explains part of the weakening of WENSO teleconnections. Associated with this ridge are easterly anomalies at the climatological jet position and westerly anomalies in the deep tropics. A shallow water model linearized about such anomalies gives a weaker response to a deep tropical vorticity anomaly, adding to our explanation of why WENSO teleconnections are weaker under EQBO.