Quantitative valuation of green roofs? cooling effects under different urban spatial forms in high-density urban areas

In the context of global climate change, the increasing urban heat island (UHI) effect is a serious challenge to sustainable urban development. The construction of green roofs is an important means to optimize the urban thermal environment, especially in high-density urban areas. However, the cooling effect of green roofs in different urban spatial forms varies. Thus, the quantitative evaluation of the cooling effect of green roofs is significant for the scientific and effective mitigation of the UHI effect. This study took the central district of Chengdu City as a typical area, clearly classified urban spatial form types based on the LCZ theory, and quantified the relative land surface temperature (RLST) difference between before (2014) and after (2018) the implementation of green roofs based on Landsat 8 remote sensing image retrieval. Numerical analysis methods were used to statistically evaluate the cooling effect of green roofs under different urban spatial form types by GIS. The results showed that (1) the cooling effect of green roofs varied significantly among different urban spatial form types; (2) the best performance of the cooling effect of green roofs was in Compact Highrise (LCZ1), which could reduce RLST by 0.94 degrees C, while the worst was in Lightweight Lowrise (LCZ7). Based on the above performance of the cooling effect of green roofs, the construction of green roofs can be prioritized and zoned, and the design strategies of green roofs under different urban spatial form types can be proposed. Our study will provide a basis for developing design guidance for green roofs and scientific support for mitigating the urban thermal environment.