Enhancing outdoor thermal comfort in a historical marketplace of a hot arid climate through integrated heat mitigation strategies

Abstract

Souq Waqif, a historical marketplace in Doha, Qatar, faces severe outdoor thermal discomfort during the prolonged and extreme summer season typical of hot arid climates. This study evaluates the effectiveness of various urban heat mitigation strategies to enhance outdoor thermal comfort (OTC) under both current and future climate conditions. A high-resolution ENVI-met V5.7.1 microclimate model of the marketplace was developed and validated with field measurements. Twelve individual heat mitigation scenarios were simulated for mid-July days, based on five mitigation strategies: (1) green infrastructure (green roofs, green facades, trees addition); (2) cool materials (cool roofs and pavements); (3) blue infrastructure (water misting systems, fountain); (4) urban morphology (increasing H/W ratio); and (5) shading structures. Results show that while some scenarios (trees addition, blue infrastructure, and taller buildings) achieved substantial localized air temperature reductions reaching up to 11 °C, area-averaged reductions in physiological equivalent temperature (PET) were modest. Consequently, based on the most effective scenarios, three integrated strategies were developed and evaluated. The optimal strategy integrated green roofs and facades, enhanced tree coverage, H/W ratio of 1.5, and 50% pathway shading, reduced peak air temperature and PET as much as 8.9 °C and 19.4 °C, respectively, at the peak hour. Future climate simulations for 2050 and 2080 projected significant OTC worsening in the base case but maintained substantial improvements with the optimal strategy. Furthermore, dynamic thermal comfort simulations based on a virtual walk showed greatly reduced extreme heat stress duration. The findings highlight effective approaches for enhancing OTC in historical areas of hot arid cities.