Assessing the Cooling Benefits of Tree Canopies for Outdoor Thermal Comfort in Arid Climates

Rising extreme temperatures challenge outdoor activities, limiting urban mobility and reducing recreational opportunities in parks and public spaces. Climate change-driven heat stress increasingly affects urban livability, necessitating adaptation strategies to enhance outdoor thermal comfort. Green infrastructure, particularly urban trees, offers cooling benefits through evapotranspiration and shade. This study evaluates the cooling performance of four tree species from different plant families—Arecaceae, Fabaceae, Moraceae, and Tamaricaceae—at the King Abdullah University of Science and Technology (KAUST) campus in Saudi Arabia. Tree canopy characteristics are analyzed using the Leaf Area Index (LAI) for foliage density, Leaf Area Intensity for distribution, and Sky View Factor (SVF) for open sky exposure. Microclimate variations under the tree canopies are recorded using meteorological data, including air temperature, wind speed, relative humidity, and globe temperature. Additionally, physiological responses are assessed through skin temperature measurements, while psychological thermal comfort perceptions are gathered through surveys. Preliminary findings indicate that tree shade significantly enhances thermal comfort. The Universal Thermal Climate Index (UTCI), recorded in October, showed strong heat stress under shading (35.9°C) compared to very strong heat stress in direct sunlight (44.9°C). These results highlight the crucial role of tree canopies in mitigating outdoor heat stress. This study provides evidence-based recommendations for policymakers and urban planners to enhance urban resilience and outdoor thermal comfort through strategic tree planting in arid regions.