Influences of Oceanic Processes Between the Indian and Pacific Basins on the Eastward Propagation of MJO Events Crossing the Maritime Continent

Tropical intraseasonal Madden-Julian oscillation (MJO) is one of the dominant products of ocean-atmosphere interactions. The relationship between its eastward propagation and atmospheric boundary layer processes has been emphasized. Using the Climate Forecast System Reanalysis (CFSR) daily data, the eastward propagating MJO events are divided into the MJO_C events which pass through the Maritime Continent (MC) and MJO_N that cannot. In further research, the path from Lombok Strait to Timor Sea across the south of MC is identified as the critical movement path of MJO (MJO_SC) events. The differences in the oceanic processes and lower atmospheric fields are then revealed between the MJO_SC and MJO_N events along this critical path. The MJO_SC (MJO_N) events triggered in the eastern (western) side of the tropical Indian Ocean lead to the thermocline deepening (shallowing) and warm (cold) upper ocean in the Lombok Strait-Timor sea. Subsequently, MJO_N events propagate northeastward over the land of MC and die out. However, MJO_SC events are pulled toward the Timor Sea. During the eastward propagation of the MJO_SC events, an eastward anomalous subsurface warm current is discovered in the Timor Sea, which is prior to the atmospheric convection center. This advective heat transport in the upper ocean dominates the sea surface warming under the MJO atmospheric convection center and its eastern flank. The followed outward turbulent heat flux and vapor cause an increase in moisture and instability in the lower atmosphere east of the MJO convection center, which promotes the growth and continued eastward propagation of the MJO.