The Indian summer monsoon rainfall and ENSO

Abstract

The El Niño-Southern Oscillation (ENSO) is deemed as the most important driver of the Indian summer monsoon variability. In this paper we make an effort to document the research so far on the impacts of ENSO on the Indian summer monsoon and the various mechanisms that have been proposed to explain the tele-connection from the tropical Pacific to the monsoon region. We also briefly discuss about the distinctions between impacts of canonical El Niño and El Niño Modoki. We believe that the recent apparent weakening of the ENSO impact on the monsoon may simply be due to a combination of several inter-annual to decadal processes, as evidence by the deficit monsoon conditions during 2015 which co-occurred with an extreme El Niño.