Simulating November DYNAMO MJO Event with a Couple Regional Model: Comparisons between the Indian Ocean and Maritime Continent

The Ocean-Atmosphere-Wave-Sediment Transport (COAWST) model is a fully coupled modeling system including the Weather Research and Forecasting (WRF) model, the Regional Ocean Modeling System (ROMS) and the Simulating Wave Nearshore (SWAN) model. A single ocean domain with nested atmosphere domains is used here to study the DYNAMO MJO event in November 2011. Two model cases, one with the inner domain located within the Indian Ocean, and the other with the inner domain over the Maritime Continent, are carried out. Simulations with and without coupled ocean showed large sensitivities in surface rainfall, where coupled model produced higher and more realistic rainfall compared with TRMM observations. Sensitivity tests with WRF only simulation showed that this was due to warmer SST and stronger surface fluxes simulated by the coupled model, even though it produced a weaker SST diurnal cycle. Comparisons between the earlier time when the MJO was located in the Indian Ocean, and later time when it moved over the Maritime Continent, are also carried out with emphasis on propagations of clouds and precipitation, and their relationship to surface fluxes and diurnal cycle within the single MJO event.