Sources of Inter-Model Diversity in the Strength of the Relationship Between the Indian Summer Monsoon Rainfall and El Niño-Southern Oscillation

Using 51 models of the AMIP and historical experiments of CMIP6, we investigate the inter-model diversity of atmospheric and coupled models in the strength of the Indian Summer Monsoon Rainfall (ISMR)–El Niño-Southern Oscillation (ENSO) relationship. In atmospheric models, the Walker Circulation (WC) intensity associated with the western Pacific convective activity is most responsible for the inter-model diversity. Models with strong WC have a strong ISMR–ENSO relationship via enhancing ENSO-induced anomalies of the WC and monsoon circulation. The secondary source is the monsoon circulation differences associated with meridional rainfall contrast over the Indian monsoon region. In coupled models, the primary (secondary) source is the ENSO amplitude (WC intensity). In observation, the decadal variation of WC can also explain the changes in the ISMR–ENSO relationship. This study provides a basis for improving the model performance and advances our understanding of the observed ISMR–ENSO relationship changes.