Spatial-temporal Variation Characteristics And Influencing Factors Of Urban Heat Island In Yunlong Demonstration Zone Of Zhuzhou

Rapid urbanization has led to the intensification of the urban heat island effect,which adversely affects the urban ecological environment and residents’ health.How to scientifically and effectively formulate mitigation strategies for urban heat island effect has become an urgent ecological and environmental problem to be solved in urban sustainable development.Changes in urban land cover types and landscape patterns are the main factors affecting urban heat islands.Therefore,in-depth analysis of urban landscape characteristics and clarifying the impact of landscape pattern on the urban heat island effect can provide an important scientific basis for optimizing the landscape pattern in urban planning to alleviate the urban heat island effect.This article chose Zhuzhou Yunlong Demonstration Zone as the research object,through quantitative inversion of remote sensing data,supervised classification,spatial analysis and other technical means,guided by landscape ecology,based on the "source-sink"landscape theory,systematically analyzes the temporal and spatial evolution of urban heat island,discusses the impact of land cover types and the composition and configuration of urban heat "source" and "sink" landscape on urban heat island,and proposes specific strategies for urban heat island mitigation from the level of urban heat island network.The main findings of the study include:(1)From 2007 to 2018,the urban heat island intensity of Yunlong Demonstration Zone shows an increasing trend,the urban heat island ratio index increased from 0.239 in 2007 to 0256 in 2013 and 0.245 in 2018,the intensity of urban heat island is controlled in the later stage of the study.The heat island distribution area is mainly concentrated in the construction-intensive areas such as science and education,commercial land in the southern main urban area,and recreation land in the north.Compared with the initial stage of the study,the center of heat island in the north is newly added.(2)The thermal environment characteristics exhibited by different land cover types are quite different.Built-up land and bare land are the types with the highest average surface temperature in the study area,and become the main areas occupied by urban heat islands;farm land and forest covered by vegetation show lower temperatures;the lowest temperature mainly occurs in water types.The vegetation and building coverage information of the underlying surface is extracted,and the research is carried out until 2018.The results show that for every 0.1 increase in the normalized difference vegetation index(NDVI)value,the land surface temperature decreased by about 0.39℃;for every 0.1 increase in the normalized difference building index(NDBI)value,the land surface temperature increases by about 0.81℃.It is suggested that while enhancing greening construction and ecological area protection,more attention should be paid to controlling the disorderly expansion of construction land.(3)Based on the "source-sink" landscape theory,in terms of landscape components,the combination of heat source and heat sink landscape takes 8.75km away from the main urban area as a turning point,and changes from enhancing the heat island effect to reducing the heat island effect.And the influence of the area ratio of heat source and heat sink landscape on urban heat island is specifically studied.The results show that when the area ratio of heat source and heat sink landscape is less than 1.30,it is conducive to the mitigation of urban heat island in the study area.It is suggested that the above-mentioned distance red line and area ratio should be comprehensively considered in regional planning to formulate corresponding construction plans.In terms of landscape configuration,when the heat sink landscape patches are more concentrated,the patch area is larger,the edge shape is more complex,and the landscape fragmentation degree is smaller,the more favorable it is to alleviate the urban heat island effect,while the heat source landscape results are opposite.It is suggested that government decision-making departments should pay more attention to the optimization of urban landscape configuration when it is temporarily difficult to change the composition of urban landscape.(4)On the basis of morphological spatial pattern analysis(MSPA),it is concluded that from 2007 to 2018,the most critical patches for the formation of the urban heat island network are mainly distributed in the southern urban area of the Yunlong Demonstration Zone,and these key patches became more and more important in the entire heat island network.It shows that to control and alleviate urban heat island,the transformation of these key heat island patches is more and more necessary.It is suggested to improve and optimize land cover type structure and landscape pattern of source and sink in these important patches based on previous analysis results of influencing factors of heat island.In this way,the connection between the heat island patches will be weakened,which can effectively alleviate the urban heat island.This study discusses the mitigation measures of urban heat island from the perspective of network,which provides a new idea and method for the governance of urban thermal environment.