Propagating diurnal disturbances embedded in the Madden-Julian Oscillation

Fine structure of large-scale intraseasonal disturbance associated with the Madden-Julian Oscillation ( MJO) was analyzed using the 3-hourly ( 3B42) TRMM rainfall data. Over the Maritime Continent, diurnal cycle becomes pronounced during the passage of MJO, and the eastward propagating diurnal disturbances ( PDDs) dominate as an internal structure of large-scale convection system of MJO. Importantly, fast PDDs that penetrate through the islands are observed within the slowly propagating MJO system. This eastward penetration of PDDs through the islands result in a sudden shift of the convection center from the western part of the islands to the east, causing an overall propagation of the MJO from the Indian Ocean to the Pacific. Our results demonstrate that the diurnal cycle of convection over and around the major islands thus plays an active role in the propagation of the MJO over the Maritime Continent.