城市不透水面时空演变及其热环境效应的分形研究

Urbanization has become the most significant human activity process since the 20th century, which changes land cover types from permeable land to anthropogenic urban impervious surfaces (UIS). UIS has been found to reveal significant information about built-up areas, and can be utilized to quantify urban development and monitor urban growth. Besides this, the increase of UIS, in turn, can have negative effects on urban ecological environment. A well-documented consequence of the growth in UIS area due to urbanization is the formation of an urban heat island (UHI) that is a major component of urban climate. With the development of airborne or satellite thermal infrared remote sensing, the UIS can be estimated by remote sensing technology, and the surface UHI is typically characterized as urban land surface temperature (LST), the spatio-temporal patterns of UIS and its thermal environment effect has then become increasing important as the UIS continue to increase and attracted great attention from scholars at home and abroad. In the existing studies, however, description, comparison and traditional statistical methods have been the most widely used, which is not sufficient for quantitative measurement of UIS pattern and its thermal effect. The spatio-temporal patterns of UIS and its thermal effect are complex problem. Fractal theory is one of the main means of understanding complexity. This research aims to examine and compare the fractal characteristic of UIS pattern and its thermal effect using six Landsat TM /ETM+ images, acquired from 1987-2013. Taking Xiamen, China as a study area, this research includes: ① the multifractal, two-dimension fractal, and long-range autocorrelation of UIS pattern; ② the long-range cross-correlations between the spatial patterns of UIS and LST; and ③ the geographical and ecological significance of fractal dimensions by examining the driving mechanism of UIS spatio-temporal patterns. The research provides a new perspective for the study of UIS and its environment effects and contributes to a better understanding of UIS pattern and its thermal mechanisms. It has important theoretical significance application value to mitigate UHI effects.

城市是人类高强度利用土地驱动环境变化最突出的标志，城市不透水面增长引发的热环境效应是城市化与环境变化作用机理研究的关键内容，已经受到全世界的广泛关注。城市不透水面时空演变及其热环境效应是复杂性问题，分形是复杂性研究的有效手段之一。本项目旨在从地理复杂性理论视角出发，以快速城市化地区厦门市为例，开展城市不透水面时空演变及其热环境效应的分形研究，包括：①城市不透水面空间分布的多重分形、二维分形和长程自相关性质及其随城市化在时间维的演化规律；②将去趋势波动分析扩展到两个维度，即城市不透水面与地表温度，研究二者间关系的自相似特征及复杂程度；③通过城市不透水面时空演变模式探寻城市化的地域推进过程，揭示城市不透水面时空演化的驱动机制，探讨分维数与自然、生态及经济社会因素的关系，阐明其地理学、生态学意义。研究成果将有助于深入认识城市不透水面分布与热环境的相互作用机制，对有效缓解城市热岛效应提供理论依据。

城市不透水面时空演变及其热环境效应是复杂性问题，分形是复杂性研究的重要方法。本项目从地理复杂性理论视角出发，以快速城市化地区厦门市为例，重点围绕城市不透水面时空演变的分形特征、城市不透水面与地表温度的长程互相关性和分维数的意义三个方面开展研究。首先，基于1994-2015年Landsat TM/OLI影像估算了厦门市不透水面和地表温度空间分布。其次，建立了不透水面分布的二维分形和多重分形模型，结果表明不透水面分布是具有无标度性的分形结构，具有多重分形性；将二维去趋势波动分析和多重分形二维去趋势波动分析引入城市不透水面分布研究中，计算了城市不透水面分布的多重分形去趋势波动指数，分析了不透水面分布的长程自相关特征。接下来，项目对地表温度时空分布的研究进行了扩展，计算了历年来地表温度分布的二维分形维数和多重分形维数，建立了多重分形二维去趋势波动分析模型，剖析了地表温度分布的复杂性和长程自相关特征。然后，提取了每个研究年份的厦门市28条主要交通干道的不透水面盖度和地表温度，建立了多重分形去趋势长程互相关分析模型，分析了城市不透水面与地表温度间的长程互相关特征。最后，在每个研究年份的影像上分别选取了若干个子区域，分别对子区域的分形维数与统计量进行分析，探讨了分维数的意义。本项目为为城市LUCC及其环境效应研究提供一种可以参考和借鉴的思路，并可在减缓城市热岛方面为城市规划与管理提供科学依据。本项目研究成果包括，厦门市不透水面和地表温度时空演变的二维分形、多重分形规律及长程自相关特征、不透水面与地表温度分布的长程互相关特征、分维数的意义，提交年度报告2份及结题报告1份，发表论文7篇（其中SCI期刊论文2篇，EI 会议1篇，中文核心4篇）。