Spatial-temperal Involution Characteristics Of Impervious Surface Area And Its Thermal Effect In Recent 30 Years Of Nanjing

Urban impervious surface area(Impervious Surface Area,ISA)is originating from urbanization progression,at the same time,because of its physical properties of soil water infiltration and encroachment on natural ground cover,it can affect the ecological environment.The most significant and the most directly perception of human is its effect on urban thermal environment.The deterioration of thermal environment caused by the expansion of ISA directly influenced the human and other species's living and welfare,today,in the context of globle urbanniztion and globle warming,it's a challenge of the whole word to manage and control the expansion of ISA and the deterioration of urban thermal environment.Efficient management must depend on comprehensive recognition and grasp about the ISA's evolutionary process and its effect on thermal environment.With the development and completion of spatial information technology and spatial statistics,which make it possible to abtain a comprehensive and systematic recognization of urban long time series evolutionary characteristics and mechanism,and accurately grasp it' s thermal effect to provide data support for the management of ISA's expansion and the govern of urban thermal environment,which will promote the city' s healthy and greening development.This study's main study area is the central Nanjing metropolitan circle which has a high urbanization level.Exploring the long time-periods ISA's spatial-temporal change mechanism,analyzing the different characteristics of urban thermal environment and change feature in multiple periods,additionally,analyzing the ISA's thermal effect based on grid-based large sample data in different time periods,further analyzing and discussing the main impact factors,utilizing the newest urban ISA dataset,Landsat TM and Landsat OLI satellite images,combining with spatial statistic technology,landscape ecology theory and remote sensing technology.The main content and conclusions are shown below:(1)Analyzing the study area's long time-series(1985-2018)ISA's spatialtemporal involvement from multi-perspectives:Study found that the study area's ISA increased significantly in recent 30 years,which more than 8 times from beginning to the end,the growing dynamic degree was more stable,but the increments of each year had some differences.In the increasing process,the increasing directivity was weaken over time,and there had certain increasing law in different districts,the inner city revealed a saturation phenomenon,the outer city increased gradually.Finally,using the landscape ecology theory to study the annual spatial pattern of ISA,and found all the metrics showed a obvious variational trend,which also demonstrated the ISA had a significant dynamic variation process.So the increasing process was summarized as:the directivity is weaken and the increment is more balanced,spatial expanding with spatial densification.(2)Studying the spatial-temporal involvement of multi-periods urban thermal environment:Based on the retrieval land surface temperature of study area,the statistic and spatial analysis results showed that the urban thermal environment got worse gradually,although the degradation rate was decreased in recent period,the whole land surface temperature was increased continually,and the thermal environment showed a higher heterogeneity,which still need pay much closer attention on.Additionally,the area of region which have higher land surface temperature than medium were showing a persistent increasing trend,and the heat island intensity was also in sustained growth,the heat island intensity of recent period was 3 times than the origin.Much amount medium land surface temperature region was transformed to higher regions.Finally,Moran'? was utilized for quantitative describing the spatial auto-correlation of ISA and thermal environment,which demonstrated both of their distribution were highly spatial auto-correlated.(3)Exploring the ISA's effect on thermal environment through quantitative methods step by step,analyzing the key pattern parameter and describing its mechanism and progression of the effect:There have significant difference between the land surface temperature of ISA and no ISA,and it varied with time periods,but the ISA has the high temperature effect in totally.Fitting the land surface temperature by ISA's spatial pattern metrics through spatial grids,OLS model of multi-factor analysis performed well under the large sample data,the coefficients,however,is not stable,the reason of which may caused by the relative low correlation of partial index,from the results of OLS single factor analysis and Pearson correlation analysis between indicators of impervious surface area pattern index and land surface temperature,the coefficients of the indicators varied obviously under different ISA coverage.Based on the overall analysis,PLAND was demonstrated as the most crucial parameters of ISA on urban thermal effect,which has the highest correlation and as the most stable interact relationship under the framework of spatial-grid research.So this study explored the spatial influence of this key parameter utilizing GWR model,finding that the interpret ability of PLAND on the land surface temperature was high(R2>0.5),which was most obvious in main urban region.The results of multi-periods showed that this parameter had a growing impact on urban thermal environment as time went by,which need pay close attention on.Additionally,the expansion of ISA with PLAND value increasing strengthen the leading role on thermal environment,and which will have higher interpret ability on urban thermal environment,so targeted policy need be made to manage the thermal environment.