Assessing the Impact of Urban Canyon Geometry on Outdoor Thermal Comfort: A Case Study in Marrakech, Morocco

The rapid urbanization of cities, combined with the challenges of climate change, has made managing outdoor thermal comfort a priority in urban planning. As cities experience rising temperatures, strategies to mitigate the Urban Heat Island (UHI) effect and enhance outdoor thermal comfort are becoming essential for enhancing the quality of life and promoting sustainable, healthy urban environments. This study investigates the impact of urban form features on UHI intensity and outdoor thermal comfort in Marrakech, Morocco. The UHI effect and thermal comfort, quantified using the Universal Thermal Climate Index (UTCI), were simulated across various urban canyon design scenarios using the Urban Weather Generator and Ladybug Tools. Five simulation experiments analyzed the effects of altering street aspect ratios, building heights, and street orientations within urban canyon geometry. The results show that compact urban canyons can increase air temperature by up to 6°C but offer significant benefits for thermal comfort during winter nights and spring and summer days. Street orientation had the greatest impact on thermal comfort, with UTCI variations reaching up to 15°C. The northeast-southwest orientation proved optimal across all seasons and building heights had a limited effect, except during winter. This study highlights the importance of urban design in mitigating UHI and enhancing outdoor thermal comfort, providing key insights for sustainable urban planning in hot climates. Overall, a compact urban canyon with a northeast-southwest street orientation is identified as the most effective design for improving outdoor thermal comfort in Marrakech.