LAUSR

AbstractStratospheric sudden warming (SSW) events exhibit pronounced interannual variability. Based on zonal wind reversals at 60°N and 10 hPa, it has been suggested that SSW events occur more preferentially during El Nino–Southern Oscillation (ENSO) winters (both El Nino and La Nina winters) than during ENSO-neutral winters. This relationship is reevaluated here by considering seven different SSW definitions. For all definitions, SSW events are detected more frequently during El Nino winters than during ENSO-neutral winters, in agreement with a strengthened planetary-scale wave activity. However, such a systematic relationship is not found during La Nina winters. While three SSW definitions, including the wind-reversal definition, show a higher SSW frequency during La Nina winters than during ENSO-neutral winters, other definitions show no difference or even lower SSW frequency during La Nina winters. This result, which is qualitatively insensitive to the choice of reanalysis datasets, ENSO indices, and ...