The Research Of Urban Eco-environmental Quality Under The Influence Of Heat Island Factor

This paper aims to analyze the spatial heterogeneity of urban heat islands and explore the relationship between urban heat islands and the quality of the eco-environment.Chongqing City,which has obvious urban heat island effect,was selected as the study area,and Landsat8 remote sensing images were used as the experimental data.Firstly,the spatial heterogeneity of urban heat islands and the driving causes of this spatial heterogeneity were quantitatively analyzed by the semi-variogram.Secondly,based on the semi-variogram,least square method and geographically weighted regression model,the relationship between urban heat islands and the quality of the ecological environment and the scale effect were explored from three aspects:the spatial structure,global correlation,and local correlation.Finally,based on the analysis results of various parts,suggestions were made to alleviate urban heat islands and improve the quality of the eco-environment.The specific research content and main conclusions are as follows:1.The surface temperature and thermal field variance were retrieved by using the radiative transfer equation method,and describing the distribution characteristics of the heat islands macroscopically.Then calculate the semi-variance function and fractal dimension in the eight directions(0o,22.5o,45o,67.5o,90o,112.5o,135oand 157.5o)and the omnidirectional semi-variation function on the three range scale scales(large,medium,and small(division according to the geographical elements cotained in the region))to in-depth analysis the spatial heterogeneity of urban heat island and the driving causes of this spatial heterogeneity.The results showed as follows:(1)The heat islands are mainly concentrated in the densely building areas of the middle of the three mountains,and are distributed approximately in the direction of 22.5o.(2)The spatial structure of the heat island exhibits obvious anisotropy,and due to the obstruction of the mountain range to the spatial distribution of urban heat islands,the variation complexity is the smallest in the same direction of 0o-22.5oas the direction of the extension of the mountain range,the most complex variation is seen in the vertical90o-112.5odirection.(3)Three major geographic factors(mountains,rivers,and urban buildings)have a significant impact on the spatial heterogeneity of heat islands.On the scales of large and medium,the impacts of mountains and rivers are greater and similar.Urban buildings have less impact and more stable,but it needs to be analyzed and described on small scale.2.An index system of environmental quality evaluation was constructed,the weight of each index was determined by means of principal component analysis method,and describing the evaluation results.Then using the semi-variation function to initially compare the spatial structure of urban heat islands and ecological environment quality.on the six scales of the spatial resolution of 30m,60m,120m,240m,480m,and 960m,the least squares and geographically weighted regression models were built,and the relationship and the scale effects between urban heat island and environmental quality were further explored.(1)The environmental quality of the study area is at a good level,and there are significant similarities of the spatial structure between urban heat island and environmental quality.(2)There is a negative correlation between urban heat islands and environmental quality,and both the local coefficients and the local R~2 of the geographically weighted regression models indicate that this relationship exhibited obvious spatial non-stationarity.Moreover,with the increase of the spatial scale,the influence of the heat islands on the environmental quality is gradually increasing.(3)On small scale,the geographically weighted regression model can detect the local details of the relationship between urban heat islands and environment quality,but as the scale increases,the difference of local R~2 gradually decreases,it indicate that the model gradually ignore the local details and reveal the spatial pattern relationship in a broad sense.