Spatio-temporal Evolution Of Urban Impervious Surface In Arid Areas And Its Impact On Surface Temperature

In recent years,domestic and overseas scholars have done a lot of research on the impact of impervious surfaces on urban surface temperature.Most of the research focuses on the method of extracting impervious information and the correlation between impervious surface coverage and surface temperature,and does not concentrate on the expansion research on the quantitative estimation of urban warming.Meanwhile,the existing research is mainly focused on first-tier cities rather than cities in the arid regions of the northwest.As one of the representative cities in the arid area,Xining City is driven by the western development strategy.The impervious surface of the city is expanding rapidly,and the thermal environment of the city is deteriorating significantly.The influence of the spatio-temporal changes of the impervious surface on the urban surface temperature is optimized.The living environment and the improvement of urban quality are of great significance.For the above reasons,based on the Landsat TM/OLI image data of Xining City in 2001,2009,and 2017,this thesis analyzes the spatial and temporal pattern evolution of impervious surface in Xining city in recent 20 years,using the enhanced normalized difference impervious surface index to extract impervious surface information by combining the change of annual growth rate of impervious surface area,the circle layer theory and landscape pattern index.Based on Landsat TM/OLI thermal infrared data,the surface temperature information of the Xining city in 2001,2009 and 2017 is retrieved by using radiative transfer equation,And the spatial and temporal distribution characteristics of the surface temperature in Xining city are analyzed by grading the inversion results of the surface temperature.Based on the thematic information of the impervious surface and the inversion results of the surface temperature,combined with the linear regression model and the comparative analysis method,the influence of the spatiotemporal variation of the impervious surface on the surface temperature is analyzed.The research shows:(1)From 2001 to 2017,the impervious surface of Xining expanded significantly,and the total area increase from 41.58 km~2to 96.23 km~2,with an average annual growth rate of 8.22%;the impervious surface is mainly distributed in the area 14 km~2 away from the city center,and the impervious surface expands significantly from the city center to the surrounding area.The farther away from the city center,the faster the growth rate of?impervious surface area;The highest growth rate of impervious surface in the city is located in the north area,with the lowest growth rate in the middle area of the city;The inner patch of the impervious surface is becoming more intergrated,and regular devolopment.The proportion of the largest patch(LPI)is increasing,and the degree of dominance is increasing.The interference of human activities on its spatial characteristics is strengthening.(2)The thermal environment of Xining City deteriorated significantly.During the research period,the temperature distribution of the underlying surface of the impervious surface was mainly in the middle temperature zone,sub-high temperature zone,and high temperature zone,and the proportion of the middle temperature zone and sub-high temperature zone decrease,while the proportion of the high temperature zone continued to rise.The area of high temperature areas increased from 5.36 km~2 in 2001 to 37.91 km~2 in2017,with an average annual growth rate of 12.8%;the growth of high temperature areas in the western,central and eastern parts of the city is mainly concentrated in the early stage,while the high temperature areas in the northern part show a significant growth trend throughout the study period.(3)The proportion of impervious surface coverage is positively related to the surface temperature.For every 0.1 increase of impervious surface,the surface temperature increases by 0.7-1.0?.The increase of the urban impervious surface has obvious effect on the increase of the surface temperature and the deterioration of the urban thermal environment.There are differences in the effect of urban impervious surface warming.The warming effect is the strongest in the north of the city,and the warming effect is the weakest in the central and western regions.By studying the spatio-temporal evolution of the impervious surface of Xining city and its impact on the surface temperature,it is helpful for the remote sensing dynamic monitoring of the urbanization level in the region.At the same time,it is helpful to deepen the understanding of the relationship between the impervious surface and the surface temperature in the process of urbanization,which is of great significance for alleviating the urban thermal environment and promoting the healthy development of the city.