Contrasting the energy recharge-discharge cycle between propagating and eastward-decaying Madden–Julian Oscillation events

In this study, we contrast the distinct energy recharge-discharge cycle between propagating and eastward-decaying Madden–Julian Oscillation (MJO) events during the boreal winter season (November–April) from 1979 to 2018 using the moist static energy (MSE) budget and gross moist stability (GMS) plane analyses. A total of 41 MJO events are selected during the 40-year period, including 16 strong propagating (SP), 13 weak propagating (WP) and 12 eastward-decaying (ED) types of MJOs. The column-integrated MSE budget shows that, depending on the phases, vertical and horizontal advection terms take turns leading the role in discharging or recharging the MSE. In the phase when the net flux heating reaches the maximum, vertical advection plays the lead role in discharging the MSE. In the subsequent phases when the net flux heating gradually weakens, horizontal advection becomes the dominant factor in discharging the MSE. A similar situation occurs during the recharge phases to balance the net flux cooling. The SP MJO exhibits a stronger energy recharge-discharge cycle compared to the WP and ED MJOs, and the contrast significantly enlarges from the Indian Ocean to the Maritime Continent. The GMS plane analysis further reveals that four different types of convection attribute to the recharge-discharge process. During the wet phases, the top-heavy ascending motion and negative shallow convection jointly stabilize the atmosphere by exporting the MSE; while during the dry phases, the top-heavy descending motion and the positive shallow convection together destabilize the atmosphere through importing the MSE. Moreover, the recharge (discharge) phase leads the amplifying (decaying) phase by a quarter cycle is essential to maintain a robust energy recharge-discharge cycle to drive the eastward propagating MJOs.