Geospatial assessment of early summer heatwaves, droughts, and their relationship with vegetation and soil moisture in the arid region of Southern Punjab, Pakistan

Abstract

This study focuses on the spatiotemporal analysis of early summer heatwaves, droughts, and their relationship with vegetation and soil moisture from 2013 to 2022 in South Punjab, Pakistan. The study uses a unique approach of utilizing a combination of meteorological-based maximum air temperature Tmax derived from Modern-Era Retrospective analysis for Research and Applications V.2 (MERRA-2) and remotely sensed land surface temperature (LST) to calculate heatwave metrics. Station-based precipitation (P) and remote sensing-based temperature condition index (TCI) are utilized to calculate droughts. The normalized difference vegetation index (NDVI) and the normalized difference water index (NDWI) are used to analyze the relationship between extreme events with vegetation and soil moisture. The results reveal a significant rise in the region's heatwave frequency, duration, and intensity. Spatiotemporal analysis of the SPI and TCI shows the occurrence of droughts in more heatwave years. Negative Pearson correlation R = 0.5–0.9 and coefficient of determination R2 of 0.76–0.86 of the NDVI and NDWI with drought and heatwave metrics represents a significant (<0.01) relationship and direct response of vegetation and soil moisture towards extreme events. The study affirms the hydrological vulnerability of arid regions due to extreme events and marks the attention to appropriate mitigation and adaptation strategies in the future.