Cooling intensity of hybrid landscapes in a metropolitan area: Relative contribution and marginal effect

Abstract

• Cooling intensity variance in hybrid landscapes was explored at the regional scale. • 5 indicators were chosen to cluster 8 hybrid landscapes using the K-medoids method. • FCD and PSSA are the indicators with a high impact on regional thermal environment. • Holding the forest canopy density around 0.4 is the optimal solution for cooling. • The economically optimal size of the shade is around 60% of the unit area. Rapid urbanization has exacerbated the urban heat islands (UHIs) effect. In the wind and thermal environment of integrated city-regions, UHIs and green infrastructure (GI) interact with each other. Cooling islands, formed mainly by GI with various landscape elements, can effectively reduce land surface temperature (LST) and promote local air circulation. The landscape elements hybridize and are jointly influenced by climate, distribution, and topography. However, little is known about the pattern of hybrid landscapes that have a sufficient cooling intensity to effectively mitigate the UHI effect. As such, this study selected the Taiyuan metropolitan area and constructed a research framework that clusters hybrid landscapes and quantifies the range of indicators of the optimal cooling intensity. The results were as follows: (1) Maintaining the forest canopy density above 0.4 is an effective measure to regulate the regional thermal environment; (2) In regions with complex topography, the shaded areas of vegetation and shaded slopes (over 60%) provide a stronger effect in reducing LST; and (3) The effect of landscape heterogeneity on LST needs to be considered. Finding more effective cooling methods in hybrid landscapes is still a question that needs to be explored in future research.