城市化进程中城市热岛景观格局演变的时空特征——以厦门市为例

Abstract

Cities are centers of political,economic,cultural and social life.It is a symbol of human civilization and development,and urbanization is a common trend in many countries.Nowadays,world urbanization accelerates greatly,especially in developing countries.While providing great economic and social benefits,urbanization has also created some environmental problems,including the Urban Heat Island(UHI) effect.UHI has deep impacts on material cycles and energy transfers within urban ecosystems,and has become an important issue in urban climate and environmental research.Xiamen is one of the special economic zones,and its rapid urbanization induced the UHI becoming much more intense and extensive.To study UHI from a viewpoint of landscape is a new method in urban thermal environment research.Analyzing the dynamics of the urban thermal landscape in the context of urbanization will provide support for environmental protection,energy use policy making,and urban planning and management. This study analyzed the spatiotemporal changes of urban thermal landscape pattern in the main area of Xiamen City.Firstly,Landsat Thematic Mapper(TM) and Enhanced Thematic Mapper Plus(ETM+) thermal images,which were acquired on similar dates in the winter of 1987,1992,1997,2002 and 2007,were used to retrieve brightness temperature.Then a relative brightness temperature(R) was calculated and the thermal patches were classified into 6 grades by temperature difference.Landscape metrics were used here at both landscape and class level to quantify changes in the urban thermal landscape pattern.And they can describe the changes of thermal landscape pattern in 3 aspects,including quantity,shape and structure.Finally,we investigated the distribution of thermal pollution sources in Xiamen. The results showed that: 1) In terms of quantity,with the rapid urbanization of Xiamen City between 1987 and 2007,the thermal landscape became more fragmented,and was more and more dominated by high-grade thermal landscape patches.2) The shape of high-grade thermal patches even the whole landscape tends to complex.3) For structure,each grade of thermal landscape became well-distributed and even.The new high-grade thermal patches were found close to the old ones that induced the proximity index(PROX_MN) of high-grade thermal patches increased;the aggregation index(AI) of the whole landscape decreased while the high-grade thermal patches increased;the contagion index(CONTAG) of the whole landscape also decreased so that dominance of high-grade thermal patches gradually increased.4) The area of thermal patches which converted from low-grade to high-grade is bigger than the area converted from high-grade to low-grade.According to statistical analysis,we found that it is much easier that the high-grade thermal landscape patches converted into the middle-grade thermal landscape than converted among high grades.5) The high-grade thermal patches mainly distributed in the industry area,and they were increased remarkably.All the high-grade thermal patches experienced three kinds of changes(increasing number,expanding area and increasing grade),and grouped into five high temperature zones(Haicang,Xinyang,Xinglin,seaport of Xiamen island and airport),especially in the industrial districts of Xinyang and Xinglin.