| Urban heat island(UHI),caused by the rapid increase of urban population and large-scale development and construction,has become a major environmental problem affecting the ecological environment and sustainable development.Combined with the national “13th five year plan” key R&D program and other projects,from the view of urban space,this paper aims to construct the framework of urban thermal environment optimization,reveal the adjusting mechanisim of urban thermal environment optimization,and put forward the planning methods of urban thermal environment optimization.This study forms an urban thermal environment optimization technical framework of “size(city size)-pattern(landscape pattern)-function(land function)-morphology(spatial morphology)”.Taking Xiamen,Zhangzhou,Quanzhou in southern Fujian as the study area,this study explores the spatial relationship between city size,landscape pattern,land function,spatial morphology and urban thermal environment.And based on the spatial relationship,this study put forward strategies for optimizing urban thermal environment.Firstly,based on urban spatial heterogeneity,through methods of the urban space classification and hierarchical space structure,the urban space is classified in different levels on the basis of the process of spatial resolution variation from low to high.According to the spatial classification in different levels,combined with the thought that urban thermal environment optimization is a process of gradual concretization from whole area to local area,the elements of urban thermal environment optimization are divided into four types: city size(size),landscape pattern(pattern),land function(function)and spatial morphology(morphology).In this way,the research framework of urban thermal environment optimization based on “sizepattern-function-morphology” is constructed,and the strategy system of urban thermal environment optimization is formed,which lays a theoretical foundation for the empirical research and the optimization strategies.Secondly,based on the multi-source data such as Landsat remote sensing data,nighttime light data,POI interest point data,building census data of Xiamen,Zhangzhou,Quanzhou in southern Fujian,this paper applies RS,GIS technology and a variety of quantitative analysis methods to explore the spatial relationship between city size,landscape pattern,land function,spatial morphology and urban thermal environment of the three cities in Southern Fujian,and discusses the similarities and differences of spatial correlation in the three cities.(1)In the city size level,on the one hand,nighttime light(NTL)is used to represent urban development,as a comprehensive indicator of city scale that reflects the urban land area and population size in a unit area.This study applies the bivariate spatial autocorrelation to discuss the spatio-temporal relationship between the urban development and land surface temperature(LST).The results show that: there is a positively correlation between NTL and LST.Compared with Zhangzhou and Quanzhou,NTL has a more significant influence on the LST on Xiamen.On the other hand,this study reveals the driving mechanism of urban built-up patch area and population density on thermal environment.The results show that: when the urban built-up patch area is larger than 2km2,there is a significant positive logarithmic correlation between urban built-up patch area and relative land surface temperature.There is a significant positive logarithmic correlation between population density and relative land surface temperature.(2)In the landscape pattern level,by using the method of moving window analysis and spatial autoregression model,this study analyzes the spatial relationship between urban thermal environment and the spatial pattern characteristics of various landscape.The results show that: fragmented greenspace is not as effective as continuously concentrated greenspace in alleviating urban heat island effect,while aggregated construction land will aggravate urban heat island effect.Greenspace landscape pattern has the more significant influence on LST for Zhangzhou and Quanzhou,than is the case for Xiamen.Construction land landscape pattern has the more significant influence on the LST for Xiamen,than is the case for Zhangzhou and Quanzhou.(3)In the land function level,this study applies multiple ring buffer analysis and logistic regression model to reveal the spatial relationship between urban thermal environment and the functional types such as residential,industrial,commercial,greenspace and so on.The results show that: area of greenspace and water are positively correlated with their cooling effect,the cooling effect could be at “saturation” as area increase.The cooling effect of greenspace in Xiamen is the most prominent,Quanzhou is the second,and Zhangzhou is the weakest.The formation of urban heat island areas is strongly related to the functions of commercial and services,industry,and warehouse.(4)In the spatial morphology level,the concept of Local Climate Zone(LCZ)and spatial autoregressive model are applied to quantitatively analyze the influence mechanism of spatial morphology indices on urban thermal environment.The results show that: the spatial morphology of Xiamen,Zhangzhou and Quanzhou has a similar relationship with the thermal environment.Vegetation index,water index show a negative correlation with urban heat island intensity(UHII),while building density and proportion of impervious water surface show a positive correlation with UHII.However,the correlation between building volume density,average building height,building height difference,sky view factor and UHII is not consistent in various LCZs.Finally,according to the spatial relationship between city scale,landscape pattern,land use function,spatial morphology and urban thermal environment of the three cities in Southern Fujian,combined with the common law and differentiation of spatial relationship of the three cities,this paper puts forward the optimization strategy of urban thermal environment for the three cities in Southern Fujian based on “scale-pattern-function-morphology”.It is expected to provide reference for the practice of urban thermal environment optimization.Specifically,it includes:(1)City size optimization: city size control based on city size influence;(2)Landscape pattern optimization: landscape pattern reconstruction based on landscape pattern influence;(3)Land function optimization: function layout based on land function influence;(4)Spatial morphology optimization: spatial morphology design based on the spatial morphology influence.Some innovations are presented in the following aspects:(1)Taking the urban spatial heterogeneity as the starting point,a technical framework of urban thermal environment optimization based on “scale-pattern-function-morphology” is constructed,which realizes the multi-dimensional linkage between urban space and urban thermal environment optimization,and enriches the theoretical system of urban thermal environment optimization;(2)A variety of spatial statistical analysis methods are used to reveal the spatial response rules of urban thermal environment to relevant influencing factors,so as to form a composite research system of multi-disciplinary,multi-source data processing and multi-technology application,which provides technical and methodological support for the scientific research of urban thermal environment optimization.(3)From the perspective of urban spatial heterogeneity,the spatial correlations of city scale,landscape pattern,land function,spatial morphology and urban thermal environment in the three cities of southern Fujian are revealed,and the common rules and differentiation characteristics of spatial correlations of the three cities are clarified.On this basis,an urban thermal environment optimization strategy system and planning and design pattern language based on “scale-pattern-functionmorphology” are formed. |
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