Evaluating the effect of urban built-up expansion on the heat exposure in an Indian metropolitan city during 2000 - 2020

Urban heat exposure is a prevalent micro-climatic phenomenon in rapidly urbanizing regions; however, regionspecific thermal models integrating climatic, land use and socio-economic variables remain limited, particularly for tropical metropolitan cities. The present study provides a comprehensive multi-temporal assessment of urban heat exposure (UHE) dynamics in Bengaluru, India, for the years 2000, 2010, and 2020 using Landsat and MODIS datasets. The analysis integrates land use land cover (LULC), land surface temperature (LST), urban heat island (UHI), urban thermal field variance index (UTFVI), and urban heat exposure zones (UHEZ) to evaluate the impacts of rapid urban expansion on seasonal thermal environments. The results indicate substantial urban growth, with built-up area increasing from 1090 km2 (15.59%) in 2000 to 2054 km2 (29.36%) in 2020. The summer diurnal LST increased from 38.7 ◦C in 2000 to 41.5 ◦C in 2020, while nocturnal LST increased from 25.8◦C to 28.1 ◦C during the same period. The UHE assessment further revealed substantial growth in heat-sensitive zones, expanding from approximately 849.4 km2 in 2000 to 2892.6 km2 in 2020. Multiple regression analysis confirmed that service sector density (β = 0.61), built-up density (β = 0.42), and population density (β = 0.29) exert significant positive influences on UHE, whereas vegetation and agricultural land exhibited cooling effects. Spatial overlay analysis between UHI and UHEZ revealed that the spatial agreement between high UHI and high UHE areas increased from 52.7% in 2000 to 68.4% in 2020, indicating stronger coupling between thermal intensity and human exposure due to rapid urbanization. The findings highlight that Bengaluru’s thermal environment is increasingly shaped by the interaction between urban morphology, surface energy balance, monsoondriven climatic variability, and socio-economic concentration. The study emphasizes the importance of integrated climate-resilient urban planning strategies incorporating green–blue infrastructure, urban ventilation corridors, and localized heat mitigation measures to reduce future thermal stress in rapidly urbanizing tropical cities.