Unraveling the mystery of Indian monsoon failure during El Nino

The 132-year historical rainfall record reveals that severe droughts in India have always been accompanied by El Nino events. Yet El Nino events have not always produced severe droughts. We show that El Nino events with the warmest sea surface temperature (SST) anomalies in the central equatorial Pacific are more effective in focusing drought-producing subsidence over India than events with the warmest SSTs in the eastern equatorial Pacific. The physical basis for such different impacts is established using atmospheric general circulation model experiments forced with idealized tropical Pacific warmings. These findings have important implications for Indian monsoon forecasting.