Investigating the Role of Convectively Coupled Equatorial Waves on the Onset of the Asian Summer Monsoon

Asian Summer Monsoon is a large-scale atmospheric phenomenon related to the seasonal reversal of wind due to differential heating of land and ocean that brings significant precipitation. However, the monsoon onset, rainfall intensity, and active and break phases display intraseasonal, interannual, and regional variabilities, which makes monsoon challenging to predict for current models. To improve the prediction of monsoon rainfall variability, prior studies have examined the roles of intraseasonal and interannual variabilities such as Madden-Julian Oscillation, El-Nino Southern Oscillation, and Indian Ocean Dipole on the monsoon, yet less attention has been given to the role of the Convectively Coupled Equatorial Waves (CCEWs) on monsoon rainfall variability. Therefore, to fill this knowledge gap, this study examines the roles played by CCEWs in monsoon onset, active and break phases, using satellite-based rainfall estimates (IMERG) and reanalysis (MERRA-2) dataset. We hypothesize that CCEWs could interact with the low-level monsoonal wind and moisture over the Indian Ocean and Western Pacific regions, influencing monsoon rainfall variability. In particular, we expect to see an early onset or more intense rainfall period of the monsoon when CCEWs interfere constructively with the low-level monsoonal wind. The result of this study helps to understand the potential mechanism by which the CCEWs interact and modulate monsoon’s onset, active or break phases.