Unveiling thermal diversity in urban coolspots through microclimate mobile-measurements.

Abstract

Urban environments amplify the effects of global warming, increasing thermal stress and endangering public health and social life. Among heat adaptation strategies, "urban coolspots" have emerged as an urban design practice that integrates adaptive comfort behaviours with spatial features. This study evaluates the impact of coolspots on pedestrians' thermal environments using high-resolution in-situ microclimate mobile-measurements from four sites in Nantes and Paris, France. A pedestrian-carried human-biometeorological station was employed across the study areas to record at 0.5 Hz the variables of air temperature, relative humidity, wind speed, and shortwave and longwave radiation. The findings highlight the influence of coolspots' spatial features, such as shading and flooring materials, on measured variables and relative thermal metrics. Results show that coolspots provide localized cooling effects within warmer environments, enhancing thermal diversity. Measurements spatial variability is particularly high (> 50%) in short distances in wind speed and radiative variables (shortwave and longwave radiation) but remains very low in air temperature and humidity. Radiative variables emerge as the primary drivers of thermal environments, with mean radiant temperature reductions of up to -20.0 °C in some coolspots areas. Ultimately, this study provides a spatiotemporal perspective on the role of coolspots in the public space, highlighting their contribution to thermal diversity and challenging the "one-size-fits-all" approach in urban design guidelines. Furthermore, it underscores the significance of designing thermal sequences to foster a more human-centric and adaptive approach to urban design.