Role of local air-sea interaction on south Asian monsoon in a changing climate

Diagnosis of CMIP3 integrations indicate that in a warmer planet the south Asian summer monsoon circulation weakens while rainfall over continental India increases. An analysis of mixed-layer heat budget suggests that the weakened monsoon circulation promotes SST warming over the Arabian Sea via : (i) reduced upwelling off Somalia, and (ii) deepening of the thermocline over the western Indian Ocean. Subsequently, evaporation increases over the northern Indian Ocean leading to enhanced rainfall over India.

In a warming planet, compared to basin-wide warming of about 3-4 C over the equatorial Pacific what is the importance of ~ 0.5-1.5 C warming over the tropical Indian Ocean on the mean monsoon evolution? To answer this question, a 30-member ensemble simulation of 90-days duration with GFDL_AM2.1 was performed. The model results suggest that without the local warming, the monsoon circulation collapses. The processes responsible for the collapse will be discussed.