Influence of Indian Ocean Dipole on boreal summer intraseasonal oscillations in a coupled general circulation model

The role of Indian Ocean Dipole (IOD) on poleward propagation of boreal summer intraseasonal oscillations (BSISO) is examined using long simulation of a coupled ocean-atmosphere general circulation model. The model (SINTEX-F1) simulates the salient features of BSISO realistically. It is found that coherent ( incoherent) poleward propagation of precipitation anomalies from 5 degrees S to 25 degrees N are observed during negative ( positive) IOD years. The probable mechanisms behind such an anomaly in poleward propagation of BSISO in contrasting IOD years are identified. We find that the mean structure of meridional specific humidity distribution undergoes cardinal changes in contrasting IOD years, which in turn influences the meridional propagation of BSISO. Enhanced ( decreased) air-sea interaction in negative ( positive) IOD years also supports coherent ( incoherent) poleward propagation of BSISO anomalies. This study has important implications, considering the critical role of BSISO in modulating the seasonal mean summer monsoon rainfall.