Understanding the Changes in Moisture Budget of Extreme Wet Indian Summer Monsoon Precipitation in CMIP6

Abstract

Climate change is expected to have a considerable impact on precipitation leading to more intense and frequent extreme events. Considering the different driving mechanisms of precipitation extreme is essential to understand the changes in response to climate change. In this study, we decompose the intensity of extreme wet month precipitation (EWMP) during the Indian summer monsoon (ISM) into atmospheric dynamic, thermodynamic and non-linear components by using moisture budget estimation. The data from 19 Coupled Model Intercomparison Project phase-6 (CMIP6) models are used for historical, intermediate (SSP2-4.5), and high-emission (SSP5-8.5) scenarios and the changes are estimated for near (2021–2040), mid (2041–2060), and far-future (2081–2100) relative to the historical (1995–2014) period for different monsoon sub-domains. The findings reveal a significant increase in the intensity of EWMP in the ISM, projecting 2%–12% in SSP2-4.5 and 8%–25% in SSP5-8.5 for the far-future. The enhanced vertical ascent of moisture (V-Dyn) is found to be a dominant factor contributing more than 70% to EWMP in most sub-domains. However, regardless of enhancement in intensity of precipitation, the models simulate a reduction in impact of the V-Dyn by 10%–35% from the near to far-future period, particularly in high emission scenarios. Vertical thermodynamic and non-linear moisture advection components also play minor roles (<5% in historical), with their influence gradually increasing with future warming (>15% in SSP5-8.5). The responses also vary regionally for components such as horizontal dynamic term, where it leads to precipitation offset in the northern regions, but causes enhanced precipitation in southern regions. The study highlights the spatial and temporal variability of moisture budgets of extreme wet Indian summer monsoon precipitation in a warming environment.