Global Survey of the MJO and Extreme Precipitation

Abstract

This study examines the modulation of land-based extreme precipitation around the globe by the Madden-Julian Oscillation (MJO). The upper-level convergent phase of the MJO inhibits extreme events over most regions but enhancement in other phases falls in three categories. Over Brazil, Southeast Asia, and Australia, 2-year rainfall events are most common near the core of the upper-level divergence as expected. For most other regions in the tropics and subtropics, the extreme events occur along the periphery of the MJO's envelope. Previous regional studies suggest these extremes are driven by the MJO's low-level circulation either advecting moisture or interacting with orography rather than directly increasing the vertical convection. Finally, extratropical extreme events are more likely associated with the MJO's impact on extratropical wave trains or tropical cyclones. Given the increasing skill of numerical models for predicting the MJO, these results could lead to subseasonal forecasts of extreme events.