西安市夏季热环境时空格局及公园减热效应

Spatial-temporal Pattern of Thermal Environment and Cooling Effect of Parks in Summer of Xi'an

以Landsat TM、OLI和TIRS遥感影像为基础,采用单窗算法和分裂窗算法,反演和分析了西安市中心城区相应时间点上的热场温度;采用分型网络算法提取城市热岛范围,分析了西安中心城区1988-2014年间热岛效应空间分布及其动态变化特征;利用混合光谱分解的方法提取不同下垫面分量,研究了城市地表温度与不同下垫面因素之间的关系,并以西安市中心城区内10个公园为例,分析了公园下垫面类型对周边地区温度的定量影响。结果表明:1988-2006年,西安中心城区高温与最高温区所占比例增大,2006-2014年所占比例减小。26 a间,热岛区和次热岛区的面积增加,冷岛区与次冷岛区的面积减少,面积变化的绝对值依次为:冷岛区>中间区>次热岛区>次冷岛区>热岛区。中心城区地表植被覆盖度与地表温度呈对数负相关,不透水面与地表温度呈对数正相关关系。公园内部温度与公园的周长、面积呈显著负相关关系,与周长面积比呈显著正相关;公园平均降温范围与公园形状指数呈现较强的正相关关系,降温幅度与公园水域面积和形状指数呈较低的正相关。

Based on the remote sensing image data of Landsat TM/OLI/TIRS, this paper studied the spatial-temporal pattern and dynamic characteristics of heat island landscape in Xi＇ an central urban area from 1988 to 2014, by using mono-window algorithm and split window algorithm. Object-oriented fractal net evolution approach is employed to extract the range of urban heat island. The spectral unmxing model is adopted to disclose the different underlying surface components of Xi＇an. The relationship between different underlying surface factors and the urban land surface temperature is explored. Ten parks are selected as typical examples to illuminate the relationship between the internal surface temperature and characteristics of patches in those parks as well as the cooling range of those parks. Results indicate that in 1988-2006, the proportion of areas in high and relatively high temperature in Xi＇an central urban area rises while in 2006-2914 me proportion of areas in high and the highest temperature goes down. During 26 years, the area of heat island regions increases, while the area of cold island regions reduces. The absolute value of area change is： cold island area 〉 the middle zone〉 secondary heat island 〉 secondary cold island 〉 heat island. The vegetation coverage of Xi＇an central urban area is logarithmically negatively related with the surface temperature, while the impervious surface and the surface temperature positively logarithmically correlate with each other. The internal temperature of a park has a significantly negative correlation with the perimeter and the area of the park, and a significantly positive correlation with the perimeter-to-area ratio.The park average temperature reducer range has a strong positive correlation between the park area and shape index of park. The extent of reducer average temperature showed a lower level of positive correlation between the water area and shape index.