Field measurements were conducted in a semioutdoor underground shopping street in a southern Chinese city (Nanning, China) with a hot and humid climate to quantify summer microclimatic conditions and identify drivers of thermal discomfort. Air temperatures and surface temperatures were monitored on summer sunny days across three zones in a semioutdoor underground space with a 4.5-m × 8.2-m top opening: Zone A (with long-term insolation), Zone B (without insolation), and Zone C (with transient insolation). Peak mean radiant temperature (MRT) reached 36.2°C at noon in Zone A, 5.5°C above the shaded Zone B, while ground surface temperatures peaked at 44°C. Pedestrian-level air velocity remained below 0.3 m/s, only 16% of the outdoor reference, and was misaligned by 30°–45° from the prevailing south-westerly flow, yielding a ventilation effectiveness coefficient of nearly 0.1. The MRT–air temperature difference exceeded 3.8°C at midday, surpassing the 2°C discomfort threshold for hot-humid climates. A shading–ventilation–evaporation retrofit strategy was proposed to reduce the peak MRT by 2°C and 3°C and ground temperatures by 4°C and 5°C, offering an energy-efficient approach to improve thermal comfort without full mechanical cooling. This study is the first to introduce a radiation-zoning paradigm (long-/transient-/zero-insolation) for semioutdoor underground shopping streets in hot–humid climates. By coupling high-resolution field diagnostics with a purpose-built shading–ventilation–evaporation retrofit package, we quantify microclimatic heterogeneity at the submeter scale and demonstrate an energy-efficient, nonmechanical path to thermal compliance. The work delivers an open-access field data set and a replicable zoning protocol that urban designers, facility managers, and energy modelers can adopt to benchmark and retrofit subtropical underground retail without resorting to full HVAC. By integrating micrometeorology, urban physics, and performance-based design, the findings of this study advance climate-resilient underground urbanism and support low-carbon policy targets for rapidly densifying cities in hot–humid regions.
Wang et al. (Wed,) studied this question.