Yu Zhaowu, Yao Yawen, Yang Gaoyuan, Wang Xiangrong, Vejre Henrik
Department of Geosciences and Natural Resource Management, Faculty of Science, University of Copenhagen, Copenhagen 1958, Denmark.
Department of Environment Science and Engineering, Fudan University, Shanghai 2005, China.
Sci Total Environ. 2019 Jul 15;674:242-254. doi: 10.1016/j.scitotenv.2019.04.088. Epub 2019 Apr 11.
Urban agglomeration has become the most salient feature of global urbanization in recent decades, while spatiotemporal patterns and evolution remain poorly understood in urban agglomerations, which limit the decision-makers to make more informed decisions to improve the regional environment. Here we selected one of the most rapidly urbanized regions in the world - Pearl River Delta Metropolitan Region (PRDR), located in southern China, as the case. Landsat images spanning from 1995 to 2015 were used to retrieve land surface temperature (LST). Four types of regional heat island (RHI) degree were defined for further analysis. Then multi-scale spatiotemporal patterns and characteristics of RHI were identified with the help of cloud-based computing, spatial and landscape analysis. We found that (1) traditional urban heat island (UHI) appears as an RHI on an urban agglomeration scale. In PRDR, we found RHI expended with increasing connectivity, especially in the estuary areas where isolated UHI gradually merged during the rapid urbanization. (2) The contribution of main cities in PRDR to RHI and the evolutionary trends and pattern, which is changed from a west-east to a southwest-northeast gradient, have been revealed. (3) Considering the scale effect and different RHI categories, we revealed that during the urbanization, the aggregation of the RHI is significant on a larger-scale, and the area of 4 °C ≤ Relative LST ≤ 8 °C is the stable and high-risk area, which provide scientific bases for the governance of the thermal environment on the regional scale. (4) The study also indicates the cooling effect of forests and water is better than that of grassland, while the cooling effect of grassland is uncertain. The methods and results of this study not only have implications on environmental planning and management in the PRDR but also provide useful insights into the thermal environment research and practice in other urban agglomerations.
近几十年来，城市群已成为全球城市化最显著的特征，然而人们对城市群的时空格局和演变仍知之甚少，这限制了决策者做出更明智的决策来改善区域环境。在此，我们选取了世界上城市化速度最快的地区之一——位于中国南方的珠江三角洲都市圈（PRDR）作为案例。利用1995年至2015年的陆地卫星图像反演地表温度（LST）。定义了四种区域热岛（RHI）程度用于进一步分析。然后借助云计算、空间和景观分析确定了RHI的多尺度时空格局和特征。我们发现：（1）传统城市热岛（UHI）在城市群尺度上表现为RHI。在PRDR，我们发现RHI随着连通性的增加而扩大，特别是在河口地区，孤立的UHI在快速城市化过程中逐渐合并。（2）揭示了PRDR主要城市对RHI的贡献以及演变趋势和格局，其从西向东梯度转变为西南向东北梯度。（3）考虑到尺度效应和不同的RHI类别，我们发现城市化过程中，RHI在较大尺度上的聚集显著，4°C≤相对LST≤8°C的区域是稳定且高风险区域，这为区域尺度的热环境治理提供了科学依据。（4）研究还表明森林和水体的降温效果优于草地，而草地的降温效果不确定。本研究的方法和结果不仅对PRDR的环境规划和管理具有启示意义，也为其他城市群的热环境研究与实践提供了有益的见解。
