Cooling and Humidification Effects of Blue-Green Spaces on Built Environments in Hot and Humid Regions: A Case Study of Changsha, China

This study selected Changsha, a typical “Mountain-river-sandbar-urban” area, to explore built environments along blue-green spaces during hot summer. Air temperature (Ta) and relative humidity (RH) were collected through mobile measurements. Kriging spatial interpolation method was used to obtain the spatio-temporal distributions of Ta and RH, and their changing trends were analyzed. The results indicate significant spatio-temporal heterogeneity in Ta and RH. The maximum cooling and humidification distances of a single water body to the surrounding built-up area are about 290–320 m and 400 m, with cooling and humidification amplitudes of about 0.6–2.1 °C and 2–6%, respectively. The cooling distance of the mountain is about 400 m with a cooling amplitude of 0.2–1.6 °C, and the humidification distance is about 320–360 m with a humidification amplitude of about 6%. The combined effect of mountains and rivers on the cooling effect of the surrounding built-up area is 1.6 °C, which is higher than that of a single water body. The cooling effect of water bodies is stronger than that of mountains, and the humidification effect of mountains is more pronounced. The results would provide theoretical support for urban renewal and transformation by optimizing and regulating the thermal environment.