Evaluating Vegetation and Surface Treatments for Urban Heat Island Mitigation in Hot Desert Campuses: A Microclimatic Study of Najran University

Urban Heat Islands (UHIs) intensify thermal stress in rapidly expanding campuses across hot desert regions, yet empirical micro-scale data from Saudi university environments remain limited. This study investigates the cooling performance of green spaces and surface treatments at Najran University, located in the arid southern region of Saudi Arabia. To enhance the reliability of satellite-derived land surface temperature analysis and support microclimate simulation inputs, field measurements were undertaken under existing campus conditions. Environmental sensors and handheld instruments were deployed at selected sites representing diverse surface types, including conventional paved areas, reflective-coated pavements, cemented zones, and shaded vegetated areas. Temperature and humidity sensors were elevated to ensure unobstructed ambient data capture, while infrared thermometers recorded surface temperatures through targeted
spot readings. Data loggers continuously collected ambient temperature and relative humidity during representative daytime periods. The results demonstrate clear thermal gradients across the assessed surface categories. Vegetated zones exhibited the lowest temperatures, ranging from 6.5 °C in the morning to 29.1 °C at noon, attributable to shading and evapotranspiration. Unpainted pavements showed the highest heat retention, with temperatures between 9.5 °C and 42.7 °C, whereas reflective-painted pavements consistently reduced surface temperatures relative to untreated surfaces.
Spatial analysis further confirmed an inverse relationship between vegetation density and
surface temperature distribution across the campus. Overall, the findings highlight that the strategic expansion of green infrastructure, combined with the targeted application of reflective materials, can significantly mitigate localized UHI intensity in arid institutional settings. Such measures support climate-sensitive campus design and advance broader sustainability objectives.