Unprecedented Quasi-Biennial Oscillation (QBO) disruption in 2015-2016: Implications for tropical waves and ozone

During the Northern Hemisphere (NH) winter of 2015/16, quasi-biennial oscillation (QBO) exhibited a significant disruption that was unprecedented in the observational record. It was characterized by an upward displacement of the westerly wind anomalies. Since traveling wave activity induces the QBO and in turn affects the ozone distribution, it is worth understanding how this anomalous change affects tropical waves activity (including Kelvin and MRG waves) and ozone. This study used assimilated ozone product from the Modern-Era Retrospective Analysis version 2 (MERRA2). The results showed that Kelvin and MRG wave activities are appreciably strong during this period. The strengthening of Kelvin wave activity is consistent with a persistent westerly background flow, favoring upward propagation of Kelvin waves into the stratosphere. On the other hand, the significant strengthening of MRG wave activity may be associated with enhanced equatorward propagation of extratropical Rossby waves due to strong El-Nino event. Furthermore, the results also indicated that the anomalous change in the QBO leads to increasing temperature and ozone concentration in the tropical lower stratosphere. Based on ozone budget analysis, we showed that the increase in total ozone tendency is largely attributable to the increase in dynamical ozone transport, being consistent with the QBO-induced residual circulation between the mid and low latitude, in the lower stratosphere.