Study On Cold Island Effect And Spatial Optimization Of Blue And Green Space In Hefei City

In the past 40 years,China's urbanization process has made great progress.However,due to the neglect of urban environment and other factors,some "urban diseases" have appeared in cities,and urban heat island is one of the most important manifestations.The blue and green space of the city can relieve the heat island and reduce the temperature of the surrounding environment,which is the "cold island effect".In order to explore the cold island effect of urban blue-green space,the main urban area of Hefei was taken as the research object.Based on the clear urban blue-green space pattern,the intensity pattern of cold island in the study area was calculated by inversion.The influence factors of urban blue and green space on cold island intensity and cold island diffusion were explored,and a model was built to analyze the potential surface of urban cold island.Finally,the paper proposes the optimization strategy of urban blue-green space,in order to provide scientific basis for reducing urban heat island effect and improving human settlement environment.The main research conclusions are as follows:(1)In the blue-green spatial pattern,large and large patches were dominant,medium and small patches were secondary;The proportion of farmland was the highest,and that of wetland was the least.In terms of spatial fragmentation,the study area has a high degree of fragmentation,low degree of anti-interference and easy to be disturbed by human activities.(2)The cold island pattern in the study area presents a wavy pattern with weak inside and strong outside,which is closely related to the cold island in the suburb,and the cold island in the central area is separated.The spatial autocorrelation analysis shows that the H-H area is mainly concentrated in built-up areas,mainly commercial and residential areas and industrial areas;the L-L area is mainly concentrated in blue and green space;while the high contrast area has obvious land conversion in inner and outer circle layer.(3)In terms of urban function,M type land,B type land,A type land and R type land will weaken the intensity of cold island,and M type land has the greatest impact,while R type land is much weaker than the other three.For urban buildings,the average building density will weaken the intensity of cold island.In the land cover,green land and water land will strengthen the intensity of cold island,while impervious land will weaken the intensity of cold island.In terms of the influence index of the diffusion of cold island in urban blue-green space,among the composition types of blue-green space,green space + water >,water > and green space,LSI will strengthen the intensity of cold island,and its peak value will reach around 7.On the blue-green space scale,the increase of blue-green space scale,green space scale and water area scale can enhance the cold island diffusion,and the peak value of cold island diffusion reaches around 150-200 ha.In the external environment,the impervious ground and water weakened the cold island diffusion,while the green area strengthened the cold island diffusion,and reached the peak value at 50-100 ha.The high diffusion range of sampling site 19 is due to the combined effect of its scale,morphological complexity and external green space area,which is much higher than other sampling sites(4)The cold island potential surface of the main urban area of Hefei is constructed,and the secondary cold and hot corridors of the main urban area of Hefei are established.Suggestions for corridor construction were put forward,the width of green space construction for each corridor was defined,suggestions for the renovation of weak potential areas were put forward,and the construction of blue-green space was put forward.Figure [35] table [20] reference [81]...