Urban geometry as a climate adaptation strategy for enhancing outdoor thermal comfort in a hot desert climate

Abstract

This study aimed to assess the impact of varying street canyon geometries on outdoor thermal comfort in two Egyptian cities with distinct climates: Aswan, located in the southern desert region, and Alexandria, on the northern coast. The design of urban street canyons in Egypt often neglects the country's diverse climatic regions. The investigation focused on four height-to-width aspect ratios and four principal street orientations in the two cities. Field data, ENVI-met microclimate software, and RayMan were utilized to analyze the impact of hypothesized scenarios on heat stress in the studied street canyons. Outdoor thermal comfort was evaluated using the physiologically equivalent temperature (PET). The findings demonstrated the effectiveness of aspect ratio and orientation in the respective cities. In Aswan, the aspect ratio had a greater influence on comfort, with aspect ratio of 2.5 providing the most favorable conditions and a ratio of 1 resulting in the least comfortable conditions. Conversely, in Alexandria, the street canyon orientation proved more advantageous, where a northwest-southeast orientation produced a significant decrease (10 K) in PET compared to the least favorable orientation. These results highlight the importance of considering local climatic factors in the design of urban street canyons to effectively mitigate outdoor heat stress.