Energetic processes regulating the strength of MJO circulation over the Maritime Continent during two types of El Niño

AbstractThe zonal shift of SST warming patterns associated with the eastern Pacific (EP) and central Pacific (CP) El Nino leads to a significant contrast in MJO strength over the Maritime Continent. The MJO circulation tends to be stronger over the Maritime Continent during the mature phase (autumn-winter) of CP El Nino than of EP El Nino. Based on a new MJO kinetic energy (KE) budget equation, in which the effects of mean flow and high-frequency disturbances on the MJO are separated, we found that the low-level MJO gains more KE from the background mean flow during CP El Nino events, although at the same time the enhanced MJO transfers more KE to high-frequency eddies. Among the three-dimensional circulation anomalies, the low-level convergence and cyclonic anomalies associated with upward anomalies of the Walker circulation over the Maritime Continent play leading roles in inducing the enhanced barotropic energy conversion from mean flow to MJO during CP El Nino events relative to EP El Nino events. The...