Naoko Sakaeda

Previous studies have found that Madden‐Julian Oscillation (MJO) amplitude depends on the Quasi‐Biennial Oscillation (QBO) during boreal winter. This MJO‐QBO relationship is important to realizing subseasonal‐to‐seasonal prediction skills, but the underlying mechanism remains unclear. It is often thought that this relationship arises through the modulation of the upper‐troposphere and lower‐stratosphere lapse rate by the QBO, but this mechanism assumes the one‐way impact of the QBO onto the MJO. Alternatively, the MJO can be hypothesized to influence the QBO by modulating stratospheric wave activity that is known to be critical to QBO dynamics. Therefore, using satellite and reanalysis data, this study examines whether MJO monthly activity can impact stratospheric wave activity and QBO downward propagation speed. The results depicted a lack of such impacts, suggesting this observed MJO‐QBO relationship cannot be driven by the MJO modulation of stratospheric wave forcing.