Simulation of Heatwave Days over India Using High-Resolution ICON Climate Model: Evaluation against ERA5 and IMDAA Reanalysis Datasets

Heatwaves are among the most hazardous climate extremes affecting India, with increasing frequency, duration, and intensity under ongoing global warming. This study investigates the spatial and temporal variability of heatwave days (HWDs) over India using high-resolution simulations from the Icosahedral Nonhydrostatic (ICON) climate model and compares the simulations against the ERA5 and Indian Monsoon Data Assimilation and Analysis (IMDAA) reanalysis datasets. Simulations were conducted for three representative heatwave years: 2010, 2016, and 2022. Heatwave days were identified using a fixed threshold approach based on daily maximum temperature exceeding 40°C during the March–August (MAMJJA) season. The analysis reveals that northwest India and north-central India consistently represent the primary heatwave hotspots across all datasets. ICON successfully reproduces the large-scale spatial distribution and seasonal evolution of heatwave activity, including the intensified heatwave conditions during 2016 and 2022. However, the model systematically overestimates heatwave persistence and spatial extent, particularly over southern peninsular and southeastern coastal regions. Compared to ERA5, IMDAA captures stronger regional gradients and localized heatwave structures, highlighting the importance of high-resolution regional reanalysis for evaluating climate extremes over India. Despite existing biases, the ICON simulations demonstrate substantial skill in representing regional heatwave variability and provide valuable insight into the role of land–atmosphere interactions and mesoscale processes in shaping Indian heatwave characteristics.