Evaluating the Indian Summer Monsoon Variability During the End of the 21st Century Using CMIP6 Projections

Abstract

The state of the ISM during the warm period is of concern from India's agriculture and economy perspective. Large uncertainties exist in the Indian Summer Monsoon (ISM) rainfall projections in a warming climate scenarios by the end of 21st century. In this study, we aim to evaluate ISM state by the end of 21st century and a comparison of ISM mean state has been examined between past (mid-Pliocene with respect to pre-industrial) and future(SSP5-8.5 with respect to historical) using an ensemble mean of CMIP6 models. From our analysis, it is found that the spatial averaged JJAS precipitation change over the Indian region between past and future is similar. It shows theanalogous behaviour of ISM between past and future with similar global surface air temperature changes in both periods. Further, we have examined the changes and similarities between the two periods through thermo dynamical anddynamical factors. The large-scale analysis shows that low-level wind circulation changes are slightly higher in the past than the future climate by the end of 21st century. In addition, the regional circulation over India shows thatconvection was much stronger in the past than the future. Further, the moisture budget analysis concluded that during the past warm climate (mid-Pliocene) dynamic over both large scale and regional scale plays a dominant role forintensified ISM conditions, however in the future SSP5-8.5 scenario of 21st century ISM is majorly dependent on the thermodynamic part which is based on regional warming.