Environmental Science and Engineering Seminar
What is the origin of the double Intertropical Convergence Zones (ITCZs)? What leads to the eastward propagation of the Madden-Julian Oscillation (MJO)? These are long-term mysteries in tropical meteorology and climate dynamics. In this talk, I will show that both double ITCZs and the MJO can self-emerge over an ocean surface with uniform temperature. This is counterintuitive based on prevailing paradigms that double ITZCs arise from nonuniform external forcing, and that the eastward propagation of the MJO relies on a particular background moisture distribution. To explain the finding, I propose a new theoretical framework that both double ITCZs and the MJO arise due to multi-scale interaction between short-lived atmospheric waves and individual rainstorms. I will present supporting evidence from idealized simulations and observations. This multi-scale view of tropical convection suggests that accurate representation of individual rainstorms is not only important to local weather forecast but also crucial to global climate prediction.