The Quasi-Biennial Oscillation (QBO) and Madden-Julian Oscillation (MJO) are central components of our climate system in the tropical stratosphere and troposphere, respectively. Individually, they are major sources of tropical weather variability and subseasonal predictability. Despite occurring at very different altitudes and timescales, the two are somehow linked: during winter, easterly QBO winds are associated with stronger, more persistent MJO convection. The physical mechanisms connecting stratospheric winds to tropical convection remain poorly understood, and climate models struggle to reproduce the observed relationship.

This talk introduces the dynamics of both oscillations and their importance for subseasonal prediction, before examining proposed coupling mechanisms involving static stability, wave propagation and cloud-radiative feedback. We discuss the key aspects of the QBO-MJO connection that can and cannot be explained by these theories. Finally, we explore recent work using idealised aquaplanet experiments that isolates the roles of QBO wind and temperature anomalies in modifying tropical convection.