Abstract: Mitigating urban heat island effect by sponge city construction has become one of the important issues in the research area of global climate change. Jiaxing is among one of the earliest members of national pilot sponge cities of China. With the land surface temperature of Jiaxing retrieved from Landsat 8 images in 2013, 2015, 2017 and 2018, we evaluated the mitigation effect of sponge city construction on the urban heat island of Jiaxing. The relationship between structural indicators of sponge city construction and relative heat island intensity at small andmedium scales was analyzed by Pearson correlation analysis, regression analysis and grey comprehensive correlation analysis. The results showed that the construction of sponge city obviously alleviated heat island effect of Jiaxing, with enhanced mitigation effect following the improvement of sponge city construction. The effects of structural indicators for sponge city construction from largest to the least were in the order of proportion of effective impervious area, proportion of sinking green belt, proportion of green area and proportion of permeable pavement. Considering the effectiveness of urban heat island mitigation and the economy of the project, there were differences in the thresholds of different indicators. The proportion of effective impervious area should be lower than 0.45. The proportion of green area should be higher than 0.35. The proportion of permeable pavement should be controlled at about 0.4. The application proportion of the sinking green space should be as large as possible. Based on those results, we put forward some suggestions to mitigate the urban heat island effect.

Key words: intensity normalization, airborne LiDAR, laser beam splitting, leaf area index (LAI), single laser penetration index.