Abstract:

Rapid urbanization is the main cause of increased risk to the thermal environment. Analyzing the spatial structure characteristics of the thermal environment from a network perspective is of great significance for improving the thermal environment, enhancing urban sustainability, and adapting to climate change. First, taking the urban agglomeration in the Yangtze River's middle reaches as an example, this study analyzed the spatiotemporal characteristics of the land surface temperature (LST) and heat island area of urban agglomerations using LST data and built-up area data in 2000, 2010, and 2020. Second, we adopt the morphological spatial pattern analysis (MSPA) model to extract heat island patches and classify their types, including core, islet, perforation, edge, loop, bridge, and branch. On this basis, this study set up thermal environment sources and corridors and used the circuit theory to identify the thermal environment network of urban agglomerations. Third, this study further evaluated the overall connectivity (α-index, β-index, and γ-index) and spatial connectivity (eigenvector centrality and current density) of the thermal environment network based on multiple indicators. The results show that (1) during 2000-2020, the proportion of high-temperature and sub-high-temperature areas in summer in urban agglomerations of the middle reaches of the Yangtze River showed an overall increasing trend, while the proportion of normal-temperature, low-temperature, and sub-low-temperature areas showed an overall decreasing trend. The median LST was highest in core-type heat island patches and lowest in branch-type heat island patches. (2) During 2000-2020, the total area of heat islands in urban agglomerations of the middle reaches of the Yangtze River increased from 2.80×10³ km² to 12.8×10³ km². The proportion of core-type heat island patches increased from 31.1% to 45.9%, gradually clustering in Wuhan, Changsha, and Nanchang. (3) During 2000-2020, the number of thermal environment sources increased from 56 to 215, the number of thermal environment corridors increased from 89 to 378, and the proportion of cities containing thermal environment corridors increased from 77.4% to 100%, which means that a global thermal environment network of urban agglomerations of the middle reaches of the Yangtze River has been initially constructed. (4) During 2000-2020, the overall connectivity of the thermal environment network in urban agglomerations of the middle reaches of the Yangtze River gradually increased. Regarding the distribution of spatial connectivity, it evolved from a spatially heterogeneous pattern of "high in the south and low in the north" to a spatially stable pattern of “high global connectivity”. This study aims to provide insights into the development strategies for climate adaptation at a regional scale.

Key words: thermal environmental networks, heat island patches, connectivity assessment, MSPA, CIRCUIT, urban agglomerations in the middle reaches of the Yangtze River

摘要：

快速城市化是热环境风险加剧的主因，从网络视角分析热环境的空间结构特征，对于改善热环境、增强城市可持续性以适应气候变化具有重要意义。以长江中游城市群为例，基于2000、2010及2020年地表温度数据与建成区面积数据分析城市群地表温度与热岛区域时空特征，采取形态学空间格局分析（MSPA）模型提取并划分热岛斑块类型，包括核心、孤岛、孔隙、边缘、环道、桥接以及支线，在此基础上构建热环境源地与热环境廊道，并利用电路（CIRCUIT）理论对城市群热环境网络进行识别。此外，依据多元指标分别评估城市群热环境网络的总体连通性（α指数、β指数与γ指数）与空间连通性（特征向量中心性与电流密度）。结果表明：（1）2000-2020年期间，长江中游城市群夏季地表温度高温区与次高温区比例整体呈上升趋势，常温区、低温区以及次低温区比例整体呈下降趋势，各类型热岛斑块的地表温度中位数呈现核心型热岛斑块最高而支线型热岛斑块最低的规律；（2）2000-2020年期间，长江中游城市群夏季热岛区域总面积由2.80×10³ km²增至12.8×10³ km²，其中核心型热岛斑块面积占比由31.1%增加至45.9%，在空间上呈现逐渐向武汉、长沙以及南昌等地集聚的趋势；（3）2000-2020年期间，长江中游城市群热环境源地数量由56个增至215个，热环境廊道数量由89条增至378条，包含热环境廊道的城市比例由77.4%增至100%，已初步形成城市群全局热环境网络；（4）2000-2020年期间，长江中游城市群热环境网络的总体连通性呈逐渐增强态势，空间连通性的分布趋势由“南高北低”的空间异质性格局向“全局高连通性”的空间稳定性格局演变。该研究旨在为区域尺度的气候适应发展策略提供启示。

关键词: 热环境网络, 热岛斑块, 连通性评估, 形态学空间格局分析, 电路理论, 长江中游城市群