武汉市夏季城市热岛与不透水面增温强度时空分布

城市化的不断发展使自然地表不断被不透水面所取代,城市地表温度高于乡村,形成了显著的热岛效应。城市热岛给城市生态发展与人类健康带来了严重的负面影响,对其空间模式与背后形成机制的研究意义重大。本文以武汉市为例,基于2001、2007和2016年夏季Landsat系列影像使用辐射传导方程法反演了城市地表温度,并采用MOD11A1数据进行了验证;同时,计算了不同时期的城市温度等级和热岛比例指数,分析了城市热岛的时空变化。此外,为了探究热岛效应形成的主要原因,即不透水面与热环境的关系,全局角度使用多元线性回归分析对比了其增温效果与植被水体降温效果的强弱,空间局部角度采用地理加权回归结合地形数据得到了其增温强度的时空变化。结果表明：① 辐射传导方程法适用于实验中研究区的反演;武汉市城市热岛比例指数先增后减,但温度等级高的地区仍在不断扩张;② 多元线性回归可以准确地反映不同地表覆盖对地表温度的影响,R^2值为0.910,总体上武汉市不透水面的增温效果强于植被的降温效果,并弱于水体的降温效果; ③ 2001-2016年不透水面增温强度较高区域的分布呈现“单中心”到“多中心”的变化趋势,由单一集中于中心城区变为了分散集中于三环线附近的汉阳沌口工业区、青山工业区、阳逻开发区和东西湖区等地区。综上所述,武汉市夏季热环境问题仍然较为严重,城市外部地区的不透水面增温强度正在逐渐增大,规划治理应当给予这些地区更多的关注。

Spatial-temporal Distribution of Urban Heat Island and the Heating Effect of Impervious Surface in Summer in Wuhan

With the advancement of urbanization, natural land cover has been continuously replaced by impervious surface which resulted in the phenomenon of Urban Heat Island (UHI). UHI can lead to serious negative effects on urban ecology and residents' health, so is of great significance to study the corresponding spatial pattern and dynamic change. Based on 3 summer Landsat images acquired in 2001, 2007 and 2016 of Wuhan, this paper retrieved Land Surface Temperature (LST) using Radiative Transfer Function (RTF) method and verified the results by MOD11A1 which is the daily LST product of MODIS. Furthermore, LST grade and UHI ratio index (URI) were calculated to analyze the corresponding spatial-temporal variation. We also explored the relationship between LST and impervious surface. Globally, the multiple linear regression method was applied to compare the heating effect of impervious surface with the cooling effect of vegetation and water. Locally, we used Geographically Weighted Regression (GWR) to analyze the spatial-temporal variation of the heating effect of impervious surface combined with topographic data. The results indicated that: ① RTF method is suitable for retrieving LST in the study area. URI of Wuhan ascended from 0.42 in 2001 to 0.54 in 2007, and then descended to 0.51 in 2016. However, the areas with high temperature are still expanding; ② The multiple linear regression achieved a desirable fitting accuracy with R^2 being 0.910 because it covered the impact of 3 land cover types on LST simultaneously. Overall, the heating effect caused by impervious surface in Wuhan is stronger than the cooling effect caused by vegetation, but weaker than the cooling effect caused by water; ③ From 2001 to 2016, the distribution of areas with high heating effect of impervious surface showed a trend from "single center" to "multi-center". The original single center which is located in the center of city expanded to multiple center areas covering the districts near the Third Ring Road such as Hanyang Zhuankou Industrial Area, Qingshan Industrial Area, Yangluo Open Economic Zone and Dongxihu District. Therefore, the UHI phenomenon in Wuhan is still serious in summer. The heating effect of impervious surface is intensifying in suburb areas. So urban planners should pay more attention to these areas to mitigate the heat stress.