Research of the City Expansion and Thermal Environment in Guangzhou
|Keywords||Urban Expansion Geo-information TUPU Thermal Environment Rail Transit Guangzhou|
Guangzhou, situated at the center of the Pearl River Delta, is the capital of Guangdong Province. Since the implementation of the Reform and Opening up Policy, it has experienced unprecedented a fast economic and population growth. Urbanization development in a high speed can greatly impact the land cover and transportation network. Unchecked urban expansion has brought heavy pressure on ecological environment that can be reflected by the urban thermal environment. The urban sustainable development issue have caused wide concern, and the ecological problem is a critical issue for the urban planning researchers and policy-makers to thoroughly study.Based on the TM/ETM+remote sensing images in 1990,1995,2002,2008 as well as the social, economical and meteorological statistics, this paper takes Guangzhou as an example to conduct a remote sensing dynamic monitor and integrated analysis for the urban expansion and thermal environment variation from 1990 to 2008. First, this paper concludes the urban expansion characteristic of Guangzhou by analyzing the land cover changing Geo-information TUPU. It steps forward by analyzing the interaction mechanism of transportation development and land use changing, where metro, a typical transportation method in Guangzhou, serves as a typical example. Second, this paper provides the inverse of the surface temperature and the extraction of build-up area from TM/ETM+thermal infrared band. The contribution rate to heat environment can be calculated based on the comparison between the extraction built-up area and the build-up area according to the traditional classification. By this integrated research method, we can not only analyze the urban expansion of Guangzhou, but also establish a land cover monitoring system to evaluate the outcome of environmental protection.This research shows that:A. The characteristics of the urban expansion process from 1990 to 2008 in Guangzhou can be concluded as followed:a.The process of urban expansion in Guangzhou can be apparently divided into different phases. b. At the initial stage, it appears that a radiation style urban expansion originated from the urban area. The trend of urban expansion along the transportation network is significant. The changing of traffic mode is affecting the process of urbanization. There is a closely dependent spatial relationship between urban expanding and metro line. Urban area tends to expand to areas that closed to traffic lines, because of its transportation advantage.B. According to the urban heat environment inversion, a tendency can be identified that:a. The area of heat islands is getting more and more annually, evolving from sporadical distribution to linear distribution to area distribution. b. The center heat islands are becoming hotter according to the temperature classification map. c. The heat islands in Guangzhou present a "sporadical-linear" distribution, which is different from other cities.C. When comparing with land use type, it shows that area with extreme high temperature and high temperature is consistent with urban construction land, area with lower-high temperature is consistent with residential land and un-utilized land, medium and lower-medium temperature area is consistent with green land and water body, relatively low and low temperature area is consistent with forest land. From the above, a conclusion can be drawn that we should protect the wetland and forest, along with reasonable planning, in order to improve the heat environment in Guangzhou.In general, urbanization is further developing as urban population, land demand, transportation demand keep increasing. Reasonably control the development of each factor is critical for a urban to achieve sustainable development. At the same time, urban thermal environment indicates only part of the whole ecological environment. Thoroughly and systematically studying the relations between urban expansion and ecological environment in order to build a sustainable urban should be the ultimate goal of urban planning.