Wave Spectra during the Unexpected Qbo Disruption

An unexpected disruption of the quasi-iennial oscillation (QBO) is observed in early 2016. During this event, easterlies formed within the westerlies in the lower stratosphere, and an apparent ascending of wind anomalies is observed. Previous studies have attributed the cause of this event to the strong momentum flux from nothern mid-latitudes (Osprey et al. 2016, Newman et al. 2016). However, seasonal forecast models cannot reproduce the QBO disruption, and the dynamical details are still unclear. Here, we perform a spece-time spectra analysis on the eddy fluxes using reanalysis data, aiming to identify the characteristics of waves that are responsible for the QBO disruption. Preliminary results show that the eddy momentum flux reaching equator during early 2016 are from waves with unusually strong westerward phase speed. Strong equatorial Kelvin waves that occurred concurrently may also help the propagation of these extratropical waves into the tropics.