Historical and future projections of southwest monsoon rainfall extremes: a comprehensive study using CMIP6 simulations

The South Asian regions frequently encounter extreme rainfall events (EREs) during the summer monsoon season, causing property damage, environmental harm, and fatalities. Therefore, it is essential to comprehend how these events are evolving and may change in the future, particularly for developing countries like India. This study utilised selected models from the Coupled Model Intercomparison Project Phase 6 (CMIP6) to evaluate the intensity and contribution of EREs to seasonal rainfall during the historical period (1950–2014), as well as to anticipate the variability of extremes in the future period (2015–2100) during the summer monsoon period. Compared to observational rainfall data from the Climatic Research Unit, the selected models showed similar spatial patterns for mean and extreme rainfall in the historical period with regional biases across CMIP6 selected models, mainly in the monsoonal regions such as the west coast, central India, the Himalayas and its foothills, and the northeastern regions. Four EC-Earth models accurately projected mean and extreme rainfall for central India, the southern west coast, and the western Himalayan regions, while NorESM slightly overestimated central India and underestimated) west coast extremes. Moreover, the selected models are not adequate to realistically capture the extremes in northeastern and Myanmar coastal areas. Future scenarios predict significant changes in extreme rainfall over central India and the rain shadow regions of southeast India. The increased ERE in the northern regions of the west coast and southwestern regions of central India could lead to increased vulnerabilities in the area, especially in higher forcing scenarios. Moreover, the zone of extreme rainfall is projected the expansion of the rain shadow regions to the leeward side of the Western Ghats, particularly in the SSP5–8.5 scenario.