城市热环境的规划改善策略研究——以武汉市为例

随着城市热环境的恶化，城市中极热现象频率逐步增高。对于在城市尺度下提出的概念性的规划策略，因其缺乏可操作性并不能及时有效的缓解城市热岛现象。然而，在局部尺度下的策略一直难以提出，其中的一个原因便是对现有的关于城市微气候的研究缺少标准。在OKE教授团队提出的局部气候区（LCZ）概念的基础上，以武汉市为例提出一个通过量化的措施在局部尺度改善城市热环境的流程。方法上，利用ArcGIS和envi软件从Landsat-7的ETM+影像数据和武汉市的建筑矢量数据中提取出9个最常用的影响地表温度（LST）的地表指标，进而利用这9个指标通过K均值聚类的方法对武汉市研究区域进行LCZ划分。接着，利用普通最小二乘法（OLS）分析地表指标与LST的关系。以LCZ为框架，结合各地表指标与LST的相关性关系，从改善局部LST过高的角度出发，以分层结构和优先级的思路提出规划缓解策略。研究结果表明，案例中的武汉市研究区域被划分为7个LCZ，同时也定位出各LCZ中温度最高的热点，发现地表指标在不同的LCZ与地表温度有独特的相关性关系，因而针对不同LCZ中的热点提出了具体的地表指标参数值调整建议来改善热点的热环境状况。这可以在一定程度上有目标性的降低局部热岛的温度，同时至少在2个方面有助于城市微气候和规划的研究：(1）减小了城市热环境的研究尺度；(2）从规划角度提出了优化城市热环境的工作流程。

Optimizing the Urban Thermal Environment: A Case Study in Wuhan,China

With the deterioration of urban thermal environment,the frequency of extreme heat events in cities is increasing.The conceptual planning strategy at the city scale cannot alleviate the Urban Heat Island (UHI) effectively due to the lack of practicality.However,the strategy at local scale is difficult to be put forward,sinceone of the significant reasons is lack of a standard framework for urban microclimate study.This research took Wuhan as the case study.Based on the concept of the Local Climate Zone (LCZ) put forward by OKE's team,a workflow was proposed to optimize the urban thermal environment at local scale through quantitative measurements.Technically,we coupled Arcmap and ENVI to extract 9 land surface indicators,which are used most frequently as land surface sensitivity of Land Surface Temperature (LST),from the satellite image products of the Landsat-7 ETM + and the shape file data of buildings in Wuhan.The K-means clustering was applied to classify LCZ based on the 9 indicators.Furthermore,the relationship between the land surface indicators and LST was analyzed using Ordinary Least Squares (OLS).Taking LCZ as the framework,the mitigation process was organized in a manner of hierarchies and priorities combined with the correlation between the land surface indicators and LST.The results show that Wuhan is divided into 7 LCZs and the hotspots with the highest temperature in each LCZ are found out.At the same time,it is discovered that the land surface indicators have unique correlations with LST in different LCZs.And it is necessary and effective to optimize the urban thermal environment of hotspot in its LCZ by adjusting the land surface parameter values.The method in this research can reduce the temperature of local UHI to a certain extent,and the contributions to the study of urban microclimate and planning are at least two aspects:1) the study scale of the urban thermal environment is optimized;and 2) the workflow of adapting urban thermal environment is proposed from the perspective of urban planning.