20世纪90年代上海市热环境变化及其社会经济驱动力

Thermal environment change and its socioeconomic drivers in Shanghai City during the 1990s

城市化过程导致地表水分蒸腾减少、径流加速、显热的存储和传输增加以及水质降低等一系列生态环境效应,其中最典型的特征就是城市热岛的出现。城市热环境动态主要驱动力可以概括为两大方面:地表覆被的变化与人类社会经济活动。论文采用Landsat的TM/ETM+为基本数据源,先定量反演了每个像元内的陆地表面温度,以此探讨了20世纪90年代上海市主城区热环境的动态演化和社会经济驱动力。研究结果揭示,20世纪90年代上海市主城区热岛范围显著扩大,但中心城区的热岛强度在下降,空间格局也趋于复杂;通过分析,城市热环境空间格局动态演变是不同尺度上、相互嵌套、相互影响的多种驱动力的综合作用结果。其中,城市建成区的快速扩展是热岛范围不断扩展的最显性驱动力;中心城区人口密度显著下降是热岛中心强度降低的一个综合性驱动因子,而以重化工业为代表的能耗布局改变则是中心城区热岛强度降低的一个主要驱动力;通过增加绿化面积布局等人为措施改变热辐射和存储模式,对缓解城市热环境来说是最有意义的因素。由于多种驱动力相互嵌套、交互作用,因此建立城市热环境演变驱动机制的定量模型还十分困难,但是研究结果对于制定城市热环境改善政策和编制合理的城市规划等都具有一定的借鉴意义。

The urbanization process has significant environmental implications including reduction in evapotranspiration,promotion of more rapid surface runoff,increased storage and transfer of sensible heat,and reduction of air and water quality.The thermal environment is an important factor for the urban eco-environment.There are two main aspects of drivers for urban thermal environment dynamic,land cover change and human socioeconomic activities.This paper first retrieves the urban land surface temperature of Shanghai city using Landsat imagery data（TM/ETM＋） on a pixel-by-pixel basis,then discusses the urban thermal environment dynamic and its drivers in Shanghai city during the 1990s.The results reveal the characters of the urban heat island effect.The extent of the heat island expands distinctly and the thermal environment worsens,however,the strength of heat island in the center of the urban area decreases and its spatial pattern becomes more complex.There are many different scales of socioeconomic drivers and synthesis interactions for the thermal environment dynamic.The rapid sprawling of the urban built-up area is the apparent driver of the expanding heat island.To improve the thermal environment in the urban center,decreasing population density is a synthesis driver,but the change of energy consumption patterns represented by industry is the key driver.Man-made countermeasures are the most effective means to change the pattern of thermal radiation and storage by increasing green vegetation cover and decreasing impervious surfaces.