The Indian summer monsoon and Indian Ocean Dipole connection in the IITM Earth System Model (IITM-ESM)

Abstract

The Indian Ocean Dipole (IOD) is recognised as an important driver of interannual climate variability over different regions of the globe, including the regional monsoon systems. In particular, positive (negative) phases of IOD tend to be associated with above-normal (below-normal) monsoon rainfall over the Indian subcontinent. Realistic simulation of the IOD and Indian summer monsoon connection, however, remains a challenge in many of the state-of-the-art climate models. This study presents an analysis of IOD and its links to the Indian monsoon based on the historical simulations from the IITM Earth System Model (IITM-ESM) and other models that participated in the 6th phase of Coupled Model Intercomparison Project (CMIP6). Our findings indicate that the IITM-ESM provides not only a fairly realistic simulation of the ocean–atmosphere coupled interactions and the Bjerknes feedback processes associated with IOD events but also better captures the summer monsoon precipitation response over the Indian subcontinent during IOD events, as compared to several CMIP6 models. The physical mechanisms contributing to the improved simulation of IOD and its monsoon connection in the IITM-ESM are evaluated in this study.