24.10.2022: Ocean Circulation and Climate Dynamics Colloquium

Dr. Tobias Bayr, GEOMAR Helmholtz Centre for Ocean Research, Kiel: "Variability of ENSO Amplitude and Asymmetry in the instrumental period and their Relation to Mean-state Changes"

Hybrid Colloquium: Hörsaal, Düsternbrooker Weg 20, Kiel

When?     Monday, October 24th 2022 at 11 am
Where?    ZOOM meeting room: https://geomar-de.zoom.us/j/84836421931?pwd=OU1KUWhEamxNN2JVR2o2VzNIekZKQT09

Meeting-ID: 848 3642 1931
Kenncode: 125468


Tobias Bayr, Joke Lübbecke and Mojib Latif:
ENSO amplitude varied considerably over the last 140 year, for which we have relative reliable SST observations over the tropical Pacific. Further, the asymmetry of ENSO, i.e. that El Niño is stronger and more in the east than La Niña, covaries with ENSO amplitude in observations, indicating that the number of strong East Pacific (EP) El Niño’s is important for both ENSO amplitude and asymmetry variations. We find similar relations in a large ensemble of the CESM1-CAM5-BCG model, that can simulate the ENSO asymmetry quite realistically. Further, we find a strong relation between the ENSO amplitude and the tropical Pacific mean state, as a warmer eastern equatorial Pacific favors more EP El Niños due to a lower convective threshold in that area. Finally, we investigate if there is a self-modulating effect of ENSO asymmetry on the mean state by non-linear feedbacks in the atmosphere or ocean, that can explain the variability of ENSO amplitude and asymmetry.


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