Impacts of the Urban Heat Island on Areas of Dense Human Activity— A Study Based on Blue-Green Space, Land Surface Temperature, and Weibo Activity Hotspots in Hangzhou
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Keywords
urban heat island effect; land surface temperature; blue-green space; Weibo; activity hotspots; Hangzhou
Abstract
The urban heat island is not a uniformly high-temperature zone: areas with higher temperatures are not necessarily those with the most intensive human activity, and relatively cool zones do not necessarily encompass activity hotspots. Taking Hangzhou’s contiguous built-up area as the study area, this study retrieved and processed 18 Landsat 8 Collection 2 Level-2 images, of which 15 provided valid pixels within Hangzhou. A composite land surface temperature map for the summer of 2020 was then generated. Water bodies, green space, buildings, roads, and 244,718 geotagged summer Weibo posts were aggregated into 2,332 500-meter grids. Using descriptive statistics, Spearman rank-order correlation, and multiple linear regression, this paper analyzes the spatial relationships between the urban environment and land surface temperature. Upper-quartile thresholds were used to identify high-temperature and high-activity grids. The median grid-level land surface temperature was 45.9 °C. Water-body proportion was negatively correlated with land surface temperature (ρ = −0.21) and maintained a strong negative association after controlling for other variables (standardized β = −0.33). Building-coverage ratio was the strongest positive predictor (β = 0.43). The independent association of green-space proportion was not significant (β = 0.01, p = 0.674). The 189 high-temperature-high-activity grids contained 29.7 % of summer Weibo posts; among them, 106 grids with a blue-green-space proportion below the regional median contained 20.1 % of total posts. This study moves forward the classic “where is it hot?” heat-island question toward a spatial question: “Which activity sites deserve priority attention?”
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