Impact of newly constructed parks on urban thermal environment: A comparative analysis of 20 parks before-and-after construction.

The urban heat island (UHI), exacerbated by urbanization and warming, poses a threat to urban residents' health. While urban parks are key to UHI mitigation, their cooling effects and dynamics of newly constructed parks remain poorly understood. In this study, 20 new parks in Hangzhou were selected to investigate the characteristics of urban land surface temperatures (LST) alterations before-and-after park construction by using the single-window inversion on three years of Landsat 8 satellite imagery. Correlation analysis and Random Forest model were utilized to explore the influence of park attributes and surrounding landscapes on their cooling impact. The results indicate that newly constructed parks significantly reduce urban LST: by 0.31 °C inside the park and 0.64 °C in its surroundings, reaching 0.84 °C and 1.08 °C as parks mature. From 2022 to 2023, average park cooling distance (PCD) increased from 104.40 m to 147.50 m, park cooling area (PCA) expanded from 14.11ha to 17.88ha, park cooling intensity (PCI) rose from 0.64 °C to 1.08 °C, and park cooling efficiency (PCE) increased from 4.66 to 7.30. Correlation analysis and Random Forest model reveal that PCA is mainly affected by park area, while PCD, PCE, and PCI are mainly affected by landscape structure of surrounding building patches. These findings deepen understanding of park cooling dynamics, offering a clearer direction for maximizing park cooling benefits.