Spatial Shift of Heatwave Hotspots in India: Unraveling the Roles of Aerosols

It is crucial to understand the drivers of extreme heat in India, as heatwave intensifies under a warming climate. This study examines the spatiotemporal evolution of heatwave hotspots across India and evaluates how aerosols and atmospheric dynamics loading influence their formation. A long-term archive of heatwave events from 1981 to 2020 is constructed using reanalysis-based daily maximum temperatures (Tmax). The results indicate a substantial rise in Tmax, with all-India warming of ~0.8 ± 0.30 °C between 1981–2000 and 2001–2020. We further examine how different large-scale conditions shape hotspot evolution by comparing periods with El Niño and non-El Niño periods. El Niño contributed to the rise of +0.68 °C in average Tmax, compared to +0.18 °C in non-El Niño years. Furthermore, heatwaves are identified using a percentile-based framework. A Heatwave Hotspot Index (HHI) is developed to quantify regional variations in heatwave-prone zones by integrating five key attributes: heatwave frequency, duration, intensity, Tmax anomaly, and number of hot days. Decadal assessments reveal a marked expansion and intensification of hotspots, especially in western, central and Peninsular India, suggesting an emerging southward shift in recent decades. Further, to assess aerosol influences, we analyze MODIS AOD, CALIPSO aerosol extinction profiles and aerosol types, and CERES radiative fluxes (2008–2020). The findings underscore contrasting aerosol–radiation interactions. Enhanced AOD and increased absorbing aerosol loading intensify surface warming across western and central India. In contrast, regions exhibiting relative cooling show elevated aerosol layers that enhance atmospheric absorption while reducing the amount of solar radiation reaching the surface. During heatwaves, large-scale phenomena like El Niño, along with aerosol radiative forcing patterns, explain how the aerosol buildup during extreme heat events exacerbates atmospheric heating. These findings show the importance of aerosol-radiation interaction in determining the severity and spatial patterns of heat extremes in India.