The Study On The Influence Of Urban Expansion On Urban Thermal Environment In Hefei From 1992 To 2018

Urban thermal environment is an important symbol of urban environment.It is a comprehensive summary and embodiment of urban ecological environment condition,which is influenced by physical characteristics of the surface and human social and economic activities.Different thermal environment patterns have far-reaching influence on urban microclimate,ecological environment and human settlement environment.Therefore,the study of urban thermal environment change has important guiding significance for protecting ecological environment and building livable cities.This paper combines the single-window algorithm and the spatial downscaling HUTS algorithm to obtain the 30 m spatial resolution of Hefei City District on July 23,1992,July11,2002,July 17,2007,July 19,2013 and 2018.Surface temperature images of 5 time phases on July 15 th.On this basis,the mean-standard deviation method was used to divide the land surface temperature into five grades: low temperature area,low temperature area,medium temperature area,low temperature area and high temperature area.The temporal and spatial changes of the thermal environment were analyzed qualitatively and quantitatively,and the correlation index of urban heat island gravity center was further introduced.The heat island gravity center transfer in Hefei urban area and the contribution rate of heat island gravity center transfer in each district were analyzed from 1992 to 2018,and the heat island gravity center,high temperature gravity center and built-up area gravity center transfer path were compared.At the same time,the coupling characteristic model is used to analyze the dynamic change of coupling state between construction land expansion and urban heat island expansion in the process of urbanization.This paper mainly draws the following conclusions:(1)From 1992 to 2018,the area of built-up area and heat island area in Hefei urban area showed an increasing trend all the time,with different growth rates in different directions,mainly centered on the downtown area and expanding to the southwest.(2)From 1992 to 2018,the center of gravity of the overall heat island in Hefei urban area moved from the city center to the government affairs district,and the center of gravity transfer path is quite different from the built-up area;the four districts of Yaohai District,Shushan District,Luyang District and Baohe District moved to its industrial The district and development zone move in the direction,and among them,the Shushan District has the largest contribution rate to the shift of the urban heat island's center of gravity;(3)From the perspective of the overall coupling situation,the center of gravity of construction land and urban heat island migrated to the southwest as a whole.In 2018,the two centers of gravity were the closest,showing a more obvious coupling relationship;from the perspective of spatial coupling characteristics,the expansion of construction land and the expansion of urban heat island The coupling types are mainly coupled and lightly uncoupled.