ENSO-QBO Correlations: A Robust Dynamical Coupling or a Coincidence Due to the Short Record?

Host: Dave Randall

Presenter: Kirstin Koepnick

Location: ATS West 121

There is a long history of studies of potential interactions between the El Niño–Southern Oscillation (ENSO) and the quasi-biennial oscillation (QBO). Some suggested that ENSO may modulate QBO phase transitions or amplitude, although identifying a straightforward correlation of the two variability modes has been elusive. Recent studies showed some interesting connections between the surface composites of the two modes, sea surface temperature in particular. However, the observed record is short and noisy, raising the question whether such patterns reflect a robust dynamical coupling or a statistical artifact. In this talk, I will show the observed patterns from ERA5 show and therefore imply. Additionally, I will then discuss how the various high-top CMIP6 models produce (or do not produce) the observed signal. Finally, I will conclude with on-going work on using a simplified mechanistic model of the QBO, forced by a simplified model of ENSO, to evaluate whether observed ENSO–QBO relationships can emerge purely from chance in a short record. By comparing model output with observations, we assess the extent to which apparent correlations are reproducible by this physical mechanism or can be identified as an artifact.