Effects of cloud and tree shading on surface temperature of different pavement materials for urban sidewalks.

Abstract

The surface color and materials of sidewalk pavements exhibit different albedo characteristics, leading to varied surface urban heat island effects in subtropical regions. To quantify the effect of pavement surface color and material on SUHI, Prefabricated Concrete Structure brick (PCB), Granite brick (GB) and Dutch brick (DB) totaling 14 pavement samples in Hangzhou were placed under unshaded, cloud shaded and tree shaded conditions. CIELAB (International Commission on Illumination L*a*b*) color data, short-wave radiation (incoming and outgoing) and surface temperature were measured. Results showed that L*( lightness) value played a dominant role in the albedo of the pavement surface, and there was a positive correlation in summer and winter. The lower the L* value, the greater the cooling effect of the pavement under cloud and tree shaded conditions. Compared to unshaded condition, tree shade provided the highest cooling benefit of 32.2 °C in summer. Among the 3 types of pavement materials, DB had the lowest average surface temperature in summer and the highest in winter. Therefore, in cities with cold winter and hot summer, it is advised that DB with a high surface L* value be employed. The use of pavement with a low L* value should be accompanied by continuous shading measures to cool the surface temperature. These findings provide a basis for selecting low-energy embodied pavement materials for urban streets and offer important technical support for mitigating the urban heat island effect.