Diagnosing the role of atmospheric variability on the extreme summer monsoon precipitation events over India

Abstract

The study focused on the impact of atmospheric dynamics and thermodynamics on precipitation intensity during four extreme precipitation events (EPEs) in different locations across India from June to September 2019-2022. The magnitude and extent of precipitation observed in IMD and ERA5 varied during these EPEs. However, the occurrence of EPEs was strongly associated with enhanced convective potential energy, suppressed convective inhibition, low-level convergence, and high-level divergence, which favoured convection. EPEs were also linked to higher vorticity and a saturated atmosphere with relative humidity exceeding 80% in the upper layers. All EPEs experienced a strong low-level westerly flow and mid-tropospheric northerlies. While negative vertical velocity favours warm, moist air uplift during EPEs, positive vertical velocities (subsidence) with reduced relative humidity below 60% were observed in the upper atmosphere after EPEs. A better understanding of EPEs can be achieved by including the enhanced view of thermodynamic components, such as the horizontal transport of water vapour and moist static energy, which have shown significant increases in magnitude during an EPE occurrence.