Impact of local environment on cooling island effect of water body: Case study of Changsha, China

The deterioration of the urban thermal environment poses multiple threats to residents’ health and the ecological environment. The impact of the local environment on the water cooling island (WCI) effect is complex and non-negligible. In this study, 21 water bodies in Changsha, China, were selected to reveal the impact of the local environment on the WCI effect. The results showed that the average cooling distance (WCI_D), cooling magnitude (WCI_M), and cooling gradient (WCI_G) of the water bodies are approximately 0.31 km, 2.36 ℃, and 7.61 °C/km, respectively. The WCI effect changes with the type of land cover surrounding the water body: the greatest WCI effect occurs when the water body is surrounded by built-up land, followed by bare land, forest, and cropland. Shannon’s diversity index (SHDI) was the factor with the greatest effect on WCI_D and WCI_G, while the landscape shape index (LSI) had the greatest effect on WCI_M. The wind direction has a significant impact on WCI_D and WCI_M. The influence of the wind direction on the WCI effect is obvious, e.g., the impact of prevailing wind in the downwind direction on the WCI effect is larger than that in the upwind direction, where WCI_D and WCI_M in the downwind direction were 0.15 km and 0.24 ℃ larger than those in the upwind direction, respectively.