Study On Spatiotemporal Expansion And Thermal Environment Of Impervious Surface In Xuzhou City

The acceleration of urbanization has led to a sharp increase in the area of impervious surfaces,and the expansion of impervious surfaces has led to the urban heat island effect.Remote sensing images provide data source guarantee for studying surface coverage and its dynamic changes.It uses remote sensing technology to extract urban impervious surface information.Studying the spatial and temporal dynamic changes of impervious surfaces and their impact on the urban thermal environment has a guiding role in urban development planning.Based on the normalized difference impervious surface index method,this paper fully analyzes the spectral characteristics of different types of surface coverage based on the type of surface coverage in the study area,and proposes a normalized difference impervious surface index method that is more suitable for the correction of the study area.Based on the five-phase Landsat TM and OLI image data from 1995 to 2018 in Xuzhou area,the modified NDISI was used to extract the impervious surface information of the five periods,and then from the overall area according to the knowledge and methods of landscape ecology and geography To the local area system,the spatial and temporal evolution of the impervious surface of Xuzhou City was analyzed.And the single-window algorithm is used to invert the surface temperature of the central city from 1995 to 2018 for five years and four seasons each year,and the correlation between the seasonal change of the surface temperature and the impervious surface is analyzed.The main research contents and conclusions of this article are as follows:(1)According to the spectral characteristic differences of the types of surface coverage in the study area,based on the reflectance data of each band in the sampling point,a normalized difference impervious surface model is supplemented by a linear programming method,and a modified normalized difference impervious surface is proposed Index method.In this method,TIR,Blue and Red bands are selected as enhancement factors of impervious surface,NIR and MIR are selected as factors suppressing non-impervious surface,and then the difference calculation is used to enhance the information of impervious surface.And compared with the biophysical composition index and linear pixel unmixing model,the experiment shows that the modified normalized difference impervious surface index extraction has the highest accuracy.(2)Based on the five-phase Landsat TM and OLI series of image data from 1995 to 2018 in Xuzhou area,the city's impervious surface information was extracted from the five periods using the modified normalized difference impervious surface index.The results show that: The impermeable surface area of the district has increased from 172 km2 in 1995 to 570 km2 in 2018.The impervious surface has increased rapidly,and the impervious surface has strong expansion towards the east and south.Evolution;taking district towns as the statistical unit,the central urban area has the largest area of impervious surface expansion;select the patch density,aggregation index,the proportion of the largest patch to occupy the landscape area and the combination degree to study the change pattern of landscape pattern in Xuzhou City and find out The expansion direction of each research area is centered on the central urban area.The urban landscape is more concentrated,the urban development is more concentrated,and the impervious surface is becoming more and more dominant in all underlying surfaces;from economics,policy,natural geography Analyze the influencing factors of urban impervious surface expansion from three angles and find that impervious surface expansion is closely related to economic and policy factors.(3)Considering that the thermal environment effect mainly occurs in the central city,the central city is used as the research area,and the single-window algorithm is used to invert the surface temperature of the main city from 1995 to 2018 for five years and four seasons each year.It is found that the overall temperature of the impervious surface in Xuzhou is Upward trend;analyze the relationship between the surface temperature and the impervious surface coverage rate in the central urban area.The impervious surface coverage rate and the seasonal change trend of the surface temperature are consistent.The correlation between surface temperature and imperviousness in 1995 is related to seasonal factors.After 2004,the correlation between the two has no relationship with seasonal changes.From 1995 to 2018,the correlation between the two is getting stronger and stronger,which shows that the city Climate change has caused a heat island effect in Xuzhou.