城市公园的冷岛效应研究——以常州市为例

在长江三角洲地区快速城市化的常州市内研究公园组成与冷岛效应的量化关系.基于Landsat 8TIRS和天地图高分辨率遥感影像提取公园指标以及冷岛效应指标.使用辐射传输方程法反演研究区的地表温度，使用ArcGIS的缓冲区分析和分段回归的方法研究每个公园的地表温度、降温范围和降温幅度作为冷岛效应指标；提取公园的周长、面积，并计算融合指数作为公园组成指标，在天地图高清遥感影像中提取公园的绿地覆盖率、水体覆盖率、不透水面覆盖率以及乔木覆盖率作为公园地表覆盖指标.通过相关性分析和回归模型研究，发现公园的面积为26hm²、周长阈值为3600m，公园的面积和周长在阈值范围内能够发挥较强的降温效率，超过阈值则降温效率下降.公园的融合指数与冷岛效应呈线性相关关系，融合指数较小的公园能获得较大的降温幅度.公园的乔木覆盖率、水体覆盖率与公园内部的地表温度呈显著相关关系，不透水面覆盖率、绿地覆盖率与公园内部的地表温度相关性不显著.公园规划设计需要结合公园的面积、周长阈值，融合指数的数值以及乔木、水体的覆盖率，充分发挥公园的冷岛效应.

Study on the cooling effect of urban parks base on the case of Changzhou,Jiangsu, China

This research selected parks in Changzhou, a rapidly urbanizing city in the Yangtze River Delta, to study the relationship between the composition of parks and their cooling effect. The park composition indicators and cooling effect indicators were extracted from high-spatial-resolution images created by Landsat 8TIRS and Tianditu. Land surface temperatures of the researched area were retrieved by the radiation transfer equation, and buffer analysis of ArcGIS, piecewise regression were used to analyze cooling effect indicators of each surveyed park, including the land surface temperature, the temperature drop range and the temperature drop amplitude. The perimeter, area and integration index of the parks were measured as their composition indicators. Afterwards, park land cover indicators, namely, the green coverage, water coverage, impervious surface coverage, and tree coverage were extracted from high-definition remote sensing images of Tianditu. Correlation analysis and the regression model between the park indicators and the cooling effect revealed that the temperature drop amplitude was nonlinearly related to the area and perimeter of a park, and the threshold were 26hm² and 3600m respectively, which means that a park has a strong cooling effect with its area and perimeter within the threshold, while the cooling effect decreases with its area and perimeter exceeding the threshold. A second finding was that the integration index of a park had a linear correlation with the cooling rate, meaning greater cooling effect for parks with a lower integration index. The third finding was that the tree coverage and water coverage of a park were strongly correlated with the surface temperature inside the park, while the impervious surface coverage rate and green space coverage rate showed no significant correlation with the land surface temperature inside the park. Based on the three findings, it was concluded that to give full play to an urban park's cooling effect, planners and designers need give a thorough consideration of its area and perimeter thresholds, integration index value, and tree and water coverage.