Urban Impervious Surface and its Effects on Thermal Environments in Xiamen:An Analysis Based on Remote Sensing Technology

The fast expansion of urban space has led to the substitution of natural vegetation and water dominated landscapes by impervious materials,imposing significant impacts on ecosystems at local and global scales. This study measured the development of impervious surface in Xiamen,a coastal area in subtropical China, and investigated its impacts on regional thermal environment. The Normalized Difference Impervious Surface Index( NDISI) was used to extract impervious surface features of the study area from Landsat Thematic Mapper images of 1989,1996, and 2009, respectively. The results revealed that the area of impervious surface in Xiamen increased rapidly from 31. 78 km2to246. 54 km2during the 20-year period,with an average annual growth rate of 10. 74%. This expansion mainly took the place of vegetation lands( amounting to 77. 29%) and sea side areas( amounting to 20. 27%). Further quantitative analysis on the relationship between impervious surface and other components of the urban ecosystem suggested that the urban impervious surface area had a strong positive exponential relationship with the land surface temperature( LST) rather than a simple linear relationship. Multivariate statistics has proved that the expansion of urban impervious surface area was the most important factor contributing to the rise of urban LST,while vegetation and water worked inversely.