Quantifying the cooling potential of green infrastructure in arid urban environments

Urban overheating, intensified by climate change and rapid urbanization, poses a major challenge to livability in arid environments. Green infrastructure (GI) and cool materials are increasingly being implemented to reduce urban heat. However, quantifying the cooling performance of these urban heat-mitigation strategies remains challenging because of complex interactions among vegetation, surfaces, buildings, and the atmosphere. This study used ENVI-met V5.7.1, a high-resolution computational fluid dynamics model, to simulate microscale plant-surface-atmosphere interactions on the King Abdullah University of Science and Technology (KAUST) campus in Saudi Arabia. The approximately 800,000 m 2 study area contains 1270 trees and shrubs representing 14 plant families and 78 species. The model used representative digital tree representations for each plant family to quantify the cooling contribution of existing campus GI and to examine the effects of the two most abundant families, Arecaceae and Fabaceae. The study also evaluated a cool pavement intervention that increased walkway albedo from 0.5 to 0.7. During a heatwave event, existing GI reduced localized peak air temperature by up to 3.72 °C compared to the case with no trees. The modeled Fabaceae and Arecaceae plant configurations reduced temperature by up to 2.33 °C and 1.13 °C, respectively, demonstrating the importance of canopy characteristics in determining cooling effectiveness. Increasing the walkway albedo provided more spatially widespread cooling, reducing air temperature by up to 1.53 °C relative to the base case. To assess the impact of outdoor thermal comfort on pedestrians, Universal Thermal Climate Index (UTCI) was calculated. At 14:00, much of the study area experienced very strong to extreme heat stress. However, existing vegetation reduced localized heat stress, demonstrating the importance of shade for outdoor thermal comfort. These findings show the value of site-specific heat mitigation strategies for reducing heat exposure and guiding climate-resilient design on the KAUST campus and in similar arid urban environments.