Nonlinear Effects of the Stratospheric Quasi-Biennial Oscillation and ENSO on the North Atlantic Winter Atmospheric Circulation

Previous studies have shown that both the stratospheric Quasi-Biennial Oscillation (QBO) and the El Niño-South Oscillation (ENSO) can influence the North Atlantic winter circulation. Here we use reanalysis and model output data to show that the QBO and ENSO interact to produce a nonlinear effect on the North Atlantic winter circulation. Specifically, during El Niño winters, the QBO teleconnection mainly takes a subtropical pathway with changes in the North Pacific–Atlantic subtropical jet (STJ); during La Niña winters, the QBO connects with the troposphere predominantly through a polar pathway, that is, stratospheric polar vortex (SPV) changes. Further, the QBO-induced STJ changes in El Niño lead to anomalous Rossby wave propagation toward the North Atlantic, and the QBO-induced SPV during La Niña anomaly exerts a downward effect on the North Atlantic. Hence, the various interactions between ENSO and QBO teleconnections result in nonlinear, and even synergistic, impacts on the North Atlantic circulation.