Observed connection between the Madden–Julian oscillation and the upper tropospheric biennial oscillation

Abstract It has been found that the quasi-biennial oscillation (QBO) in the stratosphere have an important impact on the Madden Julian oscillation (MJO). In this study, we show that there is an obvious biennial oscillation in the tropical upper troposphere, which may be an unnoticed component of the known tropospheric biennial oscillation (TBO). More interestingly, similar to the QBO-MJO connection, the upper TBO is also significant correlated with MJO during boreal winter and summer. The responses of the amplitude and occurrence frequency of the eight MJO phases are broadly stronger and higher during the weak TBO when compared to the strong TBO. Our findings imply a previously underestimated multifaceted stratosphere-troposphere coupling in the tropics through MJO dynamics. The causality and mechanism of the TBO-MJO connection need further discussion in the future.