蓝绿空间冷岛效应时空变化及其影响因素--以苏州市为例

Spatial-temporal Characteristics of the Cooling Island for Blue-Green Space and Its Driving Factors in Suzhou, China

水体和植被组成的"蓝绿空间"能够有效减缓城市热岛效应,探究其时空变化特征和影响因素对于改善城市环境和促进区域绿色低碳发展具有重要意义。以2004、2010和2014年三期Landsat遥感影像为数据源反演地表温度表征热环境,构建冷岛效应强度和冷岛指数定量分析苏州市蓝绿空间降温作用的时空变化特征,利用分类统计、剖面趋势法和线性拟合等方法分析蓝绿空间面积、土地利用变化和其它社会经济因素对冷岛效应的时空影响,结论如下:(1)2004~2014年苏州市冷岛效应面积不断减小,减少比例高达24.04%;空间上看,苏州北部和东部冷岛区域减少尤为明显,南部湖泊为主的地区变化相对较小。(2)从冷岛强度数值大小看,蓝绿空间的降温能力不断增强,2004、2010和2014年的冷岛强度分别为6.3℃、7.1℃和9.6℃;但考虑到其面积变化,苏州市蓝绿空间冷岛效应对于热环境的调节作用呈现出减弱趋势。(3)水体构成的"蓝色空间"降温能力(10.5℃)远大于植被"绿色空间"的冷岛强度(4.8℃);流动河渠的冷岛强度要明显高于静止的湖泊。(4)土地利用变化:尤其城市扩张侵占大量水田为影响苏州市冷岛效应时空变化的重要驱动因素,反观苏州市湖泊总面积在研究时间范围内有小幅增长,推断出政府决策者对于蓝绿空间类型的优先保护程度。

The blue-green space, consisting of water and vegetation, can effectively mitigate the negative influence produced by urban heat island, which will help improve the urban thermal environment and promote the sustainable development. In this study, Landsat images collected from 2004, 2010 and 2014 were used to retrieve land surface temperature to characterize the thermal environment. The cooling island intensity and index were constructed to explore the spatial-temporal characteristics of the cooling island produced by blue-green space. The profile analysis and statistic method were employed to study the impact of the total area of blue green space, land use and land cover changes and social economy factors on the cooling island. The results showed that: from 2004 to 2014, the area of cooling island zone had decreased by 24.04%, which were mainly located at the north and east part in Suzhou. However, the cooling island intensity of the blue-green space were 6.3℃,7.1℃, and 9.6℃ in 2004, 2010 and 2014, respectively, which showed an increasing trend. However, when taking the area changes of blue green space into account, the cooling effect produced by blue and green space has decreased because of urbanization. The cooling effect of blue space(10.5℃) consisting of water was much higher than that of green space(4.8℃) which was consisted of vegetation, and the cooling effect of flowing river was stronger than still lakes. The changes of land use and land cover could make big differences on the spatial pattern of the cooling island. The loss of paddy land was the dominant factor for the expansion of urban area, resulting in the loss of cooling island zone at the same time. However, the total area of lakes in Suzhou has increased a little during 2004 to 2010, which reflected the choice of protection for different blue and green spaces by decision makers.