ENSO teleconnections to the Indian summer monsoon under changing climate

摘要

The teleconnection between the El Nino-Southern Oscillation (ENSO) and Indian summer monsoon rainfall is analysed in CMIP5 simulations in both historical and future scenario. A subset of models is selected, based on their ability to simulate mean rainfall and the ENSO teleconnection in the historical simulations, and those are used to examine future predictions in the central northeast region of India. For canonical and mixed canonical Modoki ENSO events, the rainfall teleconnection is spatially extended over most of India in the future. For pure Modoki ENSO events, the teleconnection disappears, and practically no influence is detected in any parts of India. Analysis of zonal wind at 200 mb indicates that for the Modoki events, there is a larger spread of changes across the models, while for canonical events there is more inter-model consistency. A rainfall decomposition technique reveals a battle between changes in circulation which act to weaken the rainfall teleconnection and changes in moisture change which act to strengthen it. The picture is most consistent in the sub-ensemble of models in the central northeast region but less consistent in regions covering southern India.