关键词: 地表温度, 城市形态, 最小二乘法, 空间滞后模型, 热环境, 天津

Abstract:

In recent years, due to the rapid urbanization process of Tianjin, the number of urban population has increased rapidly, and the intensity of the land development has risen significantly. As the urban environment changes greatly, the effect of urban heat island (UHI) becomes more prominent. At present, it is considered to be a very potential regulation measure to alleviate the heat island effect by optimizing the urban morphology. However, there are few studies on the quantitative expression of urban morphology factors in Tianjin and their comprehensive influence mechanism on surface thermal environment. In this paper, the impact of urban morphology on the surface thermal environment in summer in Tianjin was analyzed by using Landsat8 remote sensing image data and the global 10-meter resolution land cover data developed by Tsinghua University. The central urban area of Tianjin was gridded at first, with each unit side length of 120 meters. Secondly, the average land surface temperature (LST) and key morphology factors for each unit were calculated by remote sensing inversion interpretation and spatial analysis. By comparing the Ordinary Least Squares (OLS) model and the Spatial Lag Model (SLM), the optimal Model was selected to analyze the seasonal variation and comprehensive effects of building density (BD), sky view factor (SVF), floor area ratio (FAR) and greenery density (GD) on land surface temperature, finally. The morphology of the central urban area of Tianjin presented a certain pattern of spatial distribution. The impervious surface percentage (ISP) was mononuclear aggregated. The GD was distributed mainly in point pattern and minorly in line and plane pattern. The high water percentage (WP) appeared in the river network and large reservoirs. The building height (BH)/SVF gradually decreased/increased from the urban to the suburbs. The BD which closely related to the land development intensity, was above 52% in industrial areas, commercial centers and old residential areas. The areas with high FAR were loosely distributed along the triangle zones of Haihe River. Compared with OLS model, SLM model is an effective method to study the mechanism affecting the urban thermal environment for its better performance in explaining the spatial relationship between different geographical objects. The analysis of the composite effects of urban morphology on LST showed that the influence degree of each morphology factor on the LST was significantly different and varied from season to season as different factors being combined. The contribution of WP, GD and BH to the LST was negative, on the contrary, it was positive for ISP, SVF and BD, while FAR presented a two-way regulation on the LST. The above results can provide reference basis for community building layout, urban development planning and improvement of urban ecological environment.

Key words: land surface temperature (LST), urban morphology, ordinary least squares (OLS), spatial lag model (SLM), thermal environment, Tianjin