FLASH DROUGHT IN INDIA AND ITS LINKAGE WITH HEATWAVES

Abstract

This dissertation investigates the occurrence of flash droughts in India and their relationship with heatwaves. Flash droughts are rapid-onset drought events that have significant implications for agriculture and ecosystems, and heatwaves exacerbate their impacts. The primary objective of this study is to explore the occurrence of flash droughts and their linkages to heatwaves in order to improve our understanding of these events. To achieve this objective, reanalysis-based ERA5 datasets are utilized to analyse flash droughts in India. These datasets provide comprehensive evapotranspiration and potential evapotranspiration data covering the entire country. The standardized evaporative stress ratio (SESR) methodology is employed to quantify and identify flash droughts based on specific criteria. The findings of this study reveal that flash droughts occurred in approximately 35% of the years in India, with the western and central-eastern regions experiencing the highest frequencies. The characteristics of flash droughts, including their duration and intensity, are further examined using the SESR methodology. Moreover, the spatial analysis identifies subbasins that are particularly prone to frequent flash drought occurrences. In addition to analysing flash droughts, this dissertation investigates the connection between flash droughts and heatwaves through a detailed case study focusing on the Saurashtra and Kachh regions. The case study highlights the temporal relationship between these events, indicating that flash droughts typically occur from March 10th to April 26th, followed by the onset of heatwave conditions characterized by above-normal temperatures and high vapour pressure deficits.