城市水体对热岛的缓冲性能沿河岸距离的变化规律

城市水体包括城区内的自然水体和人工水体两大类。作为城市生态系统的重要组成部分,水体在缓解城市热岛效应(Urban Heat Island, UHI)上具有重要作用。研究城市热岛效应的现状,探讨水体对城市热岛的缓冲效应,为改善城市热岛效应和生态环境,并对城市进行合理的改造和规划提供理论依据。以长沙市中心城区为研究区域,以南北向贯穿长沙市的湘江河道作为主要研究对象,基于长沙市2016年7月Landsat 8 TIRS遥感影像采用大气校正法反演地表温度(Land Surface Temperature, LST),利用监督分类法获取其同步的城市化进程和土地利用类型,分析市区内地表温度及热岛效应的空间分布特征。同时,通过在湘江两侧建立多个尺度的缓冲区,并将其与地表温度分布及土地利用类型叠置,分析湘江为主的水体对长沙市热环境及各缓冲区的缓冲效应,结果表明:(1)长沙市城市建设格局与热岛效应空间分布基本相似,建筑用地热岛效应更高,极端地表温度达到53.8℃;水体、绿地和裸地的热岛效应相对较低,最低地表温度为16.0℃;(2)湘江对长沙市热岛效应具有缓冲作用,对长沙市热岛效应的平均缓冲距离为400 m;(3)湘江对热岛效应的缓冲能力与水体周边土地利用类型有关,对河东区的缓冲作用小于河西区,对沿江休闲区的缓冲效应大于沿江住宅区。综上所述,长沙市热岛效应强度与用地类型相关,建筑用地热岛效应严重;水体对热岛的缓冲效应显著,但不同缓冲区内缓冲距离存在差异,因此对城市生态格局进行小规模改造可增强水体缓冲作用,缓解城市热岛效应。

The variation of buffer performance of water bodies on urban heat island along riverbank distance

Urban water bodies are mainly classified into natural water and artificial water. As an important part of urban ecosystem, it plays an important role in relieving Urban Heat Island (UHI) effect. It is important to study the current status of urban heat island effect, explore the buffer effect of water body on urban heat island, and provide theoretical basis for urban transformation and planning rational for improving urban heat island effect and ecological environment. The area considered in this study was the north-south direction of Changsha''s Xiangjiang River, located in Changsha downtown. Based on Landsat 8 TIRS remote sensing image of Changsha City in July 2016, the land surface temperature (LST) was retrieved by atmospheric correction method. The synchronous urbanization process and land use types were obtained by supervised classification method, and the spatial distribution characteristics of surface temperature and heat island effect in urban areas were analyzed. At the same time, the buffer effects of Xiangjiang River on the thermal environment and various buffer zones in Changsha City were analyzed by building multi-scale buffer zones on both sides of Xiangjiang River and overlapping them with land surface temperature and land use types. The results showed that: (1) the spatial distribution of urban construction pattern in Changsha City was basically similar to that of heat island effect. The heat island effect of built-land was higher, and the extreme surface temperature reached 53.8 C. The heat island effect of water, green space and bare land was relatively low, and the lowest surface temperature was 16.0 C. (2) The Xiangjiang River had a buffer effect on the heat island effect in Changsha, and the average buffer distance for the heat island effect in Changsha was 400 m. (3) The buffer capacity of the Xiangjiang River to the heat island effect was related to the type of land cover around the water body. The buffer effect to the east of the river was less than that to the west of the river, and the buffer effect to the leisure area along the river was greater than that of the residential area along the river. In summary, the intensity of heat island effect in Changsha city is related to land use type, moreover, the heat island effect of construction land is serious. The buffer effect of water body on heat island is significant, but there are differences among different buffer zones. Therefore, small-scale urban ecological pattern transformation can enhance the buffer effect of water body and alleviate the urban heat Island effect.