East African Monsoon as a Drawbridge for the Circumnavigation of Madden–Julian Oscillation Events

The seasonality of circumnavigation Madden–Julian Oscillation (MJO) events is examined using 42 years observations, reanalysis, and global model simulations. MJO are most likely to propagate across the Atlantic Ocean, Africa back equatorial Indian Ocean relatively unweakened during March–April–May a lesser extent September–October–November. During these seasons, referred as “long-rain” “short-rain” periods East African Monsoon (EAM), precipitation near equator extends farthest east toward Ocean. Moisture budget analysis circumnavigating event under real hypothetical seasonally varying background conditions indicates that seasonal zonal movement component circulation regulates moistening crossing from Eastern Ensembles Energy Exascale Earth System Model simulations idealized state confirm observed drawbridge-like role EAM in propagation MJO.