Multi-decadal remote sensing assessment of Urban heat Island intensification and biophysical transformation in Al Taif, Saudi Arabia

Abstract Urban environments in arid regions face escalating environmental pressures from rapid development and climate change, making systematic monitoring of their thermal and biophysical dynamics essential for sustainable planning. This study quantifies two decades of land-surface transformation in Al Taif City, Saudi Arabia, using multi-epoch analysis of Landsat imagery (2003, 2010, 2017, 2023) processed in Google Earth Engine, with Random Forest classification achieving accuracies of 92.1 to 97.1%. Built-up areas expanded by 597% (62.1 to 433.0 km²), accompanied by reductions in water bodies (66%), vegetation cover (49%), and mountainous terrain (7%). The thermal analysis reveals a characteristic UHI-intensification signature that would have been concealed by any single statistic: scene-mean land-surface temperature changed by only − 1.6 °C (50.0 to 48.4 °C, within measurement uncertainty), whereas maximum LST rose by 3.1 °C (61.9 to 65.0 °C) and the overall thermal range widened by 9.4 °C, indicating that heat is concentrating in specific urban zones rather than warming the city uniformly. Together, correlation and principal component analyses identify vegetation- and water-related biophysical indicators as accounting for 61.9% of the thermal variance, with NDVI showing the strongest cooling association ( r = − 0.6), while built-up and bare-soil indicators show the strongest warming associations. These findings support a zone-specific planning framework calibrated to hot-arid, water-scarce contexts: the central urban core requires cool-material and shading interventions; transitional peripheries require compact growth management and passive, water-sensitive urban design; and existing natural thermal refugia require formal preservation. The methodological framework presented here offers a transferable approach for characterizing UHI intensification in rapidly expanding hot-arid cities across the Middle East, North Africa, and comparable regions, where hydrologically realistic mitigation strategies, including drought-tolerant greening, treated-wastewater irrigation, and cool-material interventions, are more feasible than generic citywide greening prescriptions.