| Urbanization, an artificial process that turning the natural land cover into impervioussurface area, is tremendously affecting environment and bio-geochemical cycles atlocal, regional, and global scales. During the process of rapid urbanization, due to theabsence of rationalized planning, the dramatic change of land use and energyconsumption structure will break the balance of urban ecosystem, triggering a seriesof urban environmental problems. As a typical characteristic of urbanization, urbanheat island effect can reflect city underlying surface and local atmosphericenvironment, and affect the process of global climate change to some extent. Analysison the pattern and driving force of urban heat island effect will help to understand thechanging trend of urban thermal environment under urbanization and of greatsignificance in mitigating heat island and risk aversion.The study area focus on Guangzhou City, combining the of3S technology, the urbanthermal environmental patterns in1989and2009are studied to explore the differentthermal environments in different stages of urbanization; grid quantitative analysis method and path analysis method are used to compare the contribution rate ofdifferent influential factors on urban heat island, and so to determine the driving forceof Guangzhou urban heat island effect; heat island prediction model is established toprovide scientific advices for urban development planning, industrial structureoptimizing and, urban greenery construction. The main study results are as following:1. Guangzhou urban heat island effect was significant, the changing trend of landsurface temperature and heat island intensity was rising, but the distribution pattern ofthermal field had different characteristics in different development stages ofurbanization. In1989, the Guangzhou urban heat island was multi-center distributed,concentrating in Zengcheng and Panyu district towns. And its heat island intensitywas higher than the downtown area. This phenomenon was related to the constructionof Town Industrial Park in1980s, the rise of a large number of highenergy-consuming industrial plants had greatly increased the emissions of waste heat,and contributed to the urban heat island formation in this period. In2009, with therapid expansion of urban built-up area, the high temperature zone had spread; Theairport and harbor areas also became extreme heat island zone because of theeconomic development; The town industrial heat island phenomenon was eased due tothe changing from high energy consumption industry to clean and efficient production.Socio-economic factors played a significant role in the changing pattern of urbanthermal environment.2. The landscape patterns of Guangzhou’s thermal fields tended to be more diversifiedand in fragmentation. The large area of continuous natural surface which was inmiddle temperature zone had cutting up by high temperature surface, which loweredthe dominance of middle temperature zone. During these20years, differenttemperature intensity levels had changed not only by quantity but also by location.The standard Kappa coefficient was only0.844. Due to the rapid urbanization, thebuilt-up area increased and human activities became more frequently, which graduallyled to the transformation from middle temperature zone to sub-high temperature zoneand high temperature zone. At the same time, the restoration of the forest and construction of urban greenery had change the middle temperature zone to lowtemperature zone because of the cooling effect. The result of Markov Predict Modelshowed that, under the same develop pattern, Guangzhou urban heat island effect willbe more significant in2029, with extreme high temperature zone2.80times as in2009and high temperature zone3.26times as in2009.3. Vegetation can take away surface heat flux through evaporation effect. Underdifferent developing stage of Guangzhou, the different overall vegetation coverageand different greenery patterns had different cooling effects. In1989, the city wasunder the early stage of construction and lack of vegetation coverage. The correlationship between vegetation and LST was too low to indicate the vegetation cooling effect.In2009, the NDVI and LST showed a significant negative correlation, the mostrelevant scale was in12000m*12000m grids with a correlation confidence of0.71.The vegetation overage should be e improved and the urban greenery pattern shouldbe optimized in order to achieve the purpose of mitigation the Guangzhou heat islandeffect.4. The urban heat island effect is affected by natural and socioeconomic factors. Usingpath analysis model to estimate the UHI driving factors, such like NDVI, populationdensity, GDP(per capita), GIOV(per capita) and SRG(per capita). The result explained71.2%of the formation and transformation of Guangzhou’s heat island effect. TheNDVI and GIOV was the direct effected factor with the determination coefficient of0.78and0.20. As a commercial city, the SRG, which indicated the businessdevelopment level, had a tremendous indirect influence to Guangzhou’s urban heatisland. However, in industrial areas, the waste heat emission from factoriescontributed more to the LST rising than the underlying surface radiation warmingeffect. Determine different driving factors of urban heat island in different regions,different development stages and different types of city will help to city planning andaverse the risk of urban heat island. |
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