Remote Sensing-Based Analysis of the Mitigating Effect of Urban Green Space on Heat Island Effect: A Case Study of Changsha City

Under the dual background of urbanisation and global warming, Urban Heat Island(UHI) effect is becoming more and more significant, and has become a key issue restricting the sustainable development of cities. It is of great practical significance to explore the regulating effect of urban green space on the surface thermal environment to optimise the spatial layout of urban green space and alleviate the heat island effect. In this study, taking the main urban area of Changsha City as an example, the surface temperature (LST) was inverted and the normalised vegetation index (NDVI) was extracted based on Landsat 8 images in 2013, 2016 and 2019. The spatial regulation of the thermal environment by green space was systematically explored through Pearson's correlation coefficient, global Moran's index and cold hotspot analysis. The results showed that the LST showed a gradient distribution of ‘high in the centre and low in the periphery’, with a significant positive spatial correlation; the NDVI always had a stable negative correlation with the LST, and the temperature was significantly lower in the area covered by high green space; the cold hotspot analysis further revealed that the hot zone was concentrated in the high-density built-up area, while the cold zone corresponded to the area where the green space was concentrated. This study can provide data support and methodological reference for the optimisation of green space allocation to mitigate UHI.