Multi-model assessment of the late-winter stratospheric response to El Niño and La Niña

Abstract The impact of El Niño-Southern Oscillation (ENSO) on the late-winter extra-tropical stratosphere (January–March) is assessed in a multi-model framework. Three state-of-the-art atmospheric models are run with prescribed SST anomalies representative strong ENSO event, symmetric patterns for Niño and La Niña. well-known temperature perturbation lower during captured by two models, which anomalous warming at polar latitudes accompanied positive geopotential height anomaly that extends over cap. In third model, shows lack pole, anticyclone confined Canada does not expand to This center action emerges from large-scale tropospheric Rossby wave train forced ENSO, shrinking/stretching around vortex invoked link it response. No disagreement across found Niña, whose teleconnection opposite sign but weaker. middle-upper (above 50 hPa) project wavenumber-1 (WN1) pattern both and, more weakly, show westward tilt up stratopause. It suggested this WN1 arises high-latitude lower-stratospheric anomalies, can be interpreted terms upward propagation stationary quasi-geostrophic balance, instead breaking.