A role of the monsoon-Indian Ocean interactions in the In-Phase Transition of the Indian-to-Australian Summer Monsoon

We examine a role of the Indian Ocean in the in-phase transition from the Indian summer monsoon (ISM) to the Australian summer monsoon (ASM) using an idealized coupled model experiment. Because in-phase transition from the ISM to the ASM occurs in non-ENSO years, previous studies have argued that the Indian Ocean may play a role in the in-phase ISM-to-ASM transitions. To examine this issue, we use a long terms simulation of a hybrid coupled model where the atmospheric general circulation model is coupled into a slab ocean model in the Indian Ocean only and the climatological sea surface temperature is specified outside the Indian Ocean. Therefore, air-sea interactions are allowed over the Indian Ocean only during the model integration. Preliminary results show that the in-phase ISM to ASM transition is induced by monsoon-Indian Ocean interactions without ENSO. Cold (warm) sea surface temperature anomalies over the Indian Ocean are induced by the strong (weak) ISM. As time progresses, strong (weak) ASM results from a meteorological condition due to the ISM-Indian Ocean interactions.