Pacific Ocean origin for the 2009 Indian summer monsoon failure

The Indian subcontinent suffered from a severe drought during the summer monsoon season of 2009 when El Niño-like conditions evolved in the Pacific. The warm sea surface temperature (SST) anomalies in this season were seen throughout the tropical Pacific and over subtropical northwest Pacific. Since the atmospheric heat sources were perturbed somewhat differently in this abnormal El Niño year, we have carried out three different sensitivity experiments using an Atmospheric General Circulation Model (AGCM) to understand the associated teleconnection. Experiments are carried out by specifying observed daily SST anomalies over the central Pacific, the eastern Pacific and the subtropical Pacific while prescribing the climatological SST elsewhere. The model results have shown that the warming in the central Pacific, resembling the recently identified El Niño Modoki condition, modified the regional Walker circulation over the tropical and subtropical Pacific so as to cause subsidence over the Indian subcontinent.