Study On The Response Law Of Imperious Surface Cohesion Density And Urban Thermal Environment

Aiming at many urban heat island effects had been studied based on administrative boundaries,and lack of research on impervious surface aggregation density and the response pattern of urban thermal environment,this paper uses Jinan as an example,based on Landsat 8and NPP-VIIRS nighttime lighting data,combined with the ecological landscape pattern index.Investigate the spatial and temporal distribution pattern of urban thermal environment,discuss the aggregate density of impervious surface and the law of urban thermal environment,and provide scientific basis for the prevention and control of urban heat island effect.The main research contents of this article include:(1)Impervious surface cohesion density method,supervised classification method and threshold method were used to extract the main built-up areas and suburban areas of Jinan.(2)Using the suburban temperature difference method to calculate the urban heat island intensity,and the spatial distribution characteristics of heat island intensity grades were studied.Select patch density(PD),percentage of landscape(PLAND),largest patch index(LPI),and clumpy index(CLUMPY)to study the evolution law of multiple spatial and temporal scales of heat island intensity in main built-up areas of cities.(3)Study the law of response of the impervious surface cohesion density and urban thermal environment,and explore the critical point of its response,and provide a scientific basis for the reasonable prevention and control of the heat island effect in Jinan.The results show that:(1)Based on the impervious surface cohesion density method,supervised classification method and threshold method,the main urban construction areas in Jinan were extracted.Supervised classification extraction accuracy as high as 89.82%.The outline of the boundaries of the built-up area of Jinan City with impervious surface cohesion density and threshold method of NPP-VIIRS nighttime lighting data extraction is generally similar.Relatively speaking,theboundary of the built-up area extracted by the impermeable cohesion density is higher than that of the built-up area extracted by the nighttime light data,but the NPP-VIIRS nighttime lighting data extraction is more convenient and quicker for the main urban construction area,especially for the large-scale area.(2)On the temporal scales,using the heat island intensity calculation formula,we know that the heat island intensity in 2013 and 2017 were 1.17°C and 2.75°C,respectively,an increase of1.58°C.The results of the four landscape indices of PD,PLAND,LPI,and CLUMPY show that the intensity of urban heat islands is increasing,and the study area presents a multi-center urban heat island pattern with large areas and concentrated distribution.(3)On the spatial scale,through the transfer matrix model,it is known that the information transfer between different spatial scales of the heat island level landscape index is analyzed.It can be seen that landscape indices of different heat islands levels are significantly affected by spatial scale changes.According to the change law of landscape index on different spatial scales,they can be roughly divided into three categories: increased,reduced and fluctuations.There are obvious “scale effects” in the landscape pattern indices PD and CLUMPY,while the PLAND and LPI indices have alternating patterns between the heat island levels.(4)The land surface temperature increases with the increase of the impervious surface cohesion density and has a very significant correlation.The correlation coefficients between Huaiyin,Lixia,Shizhong and Tianqiao are: 0.80,0.75,0.73,and 0.81 respectively.(5)The land surface temperature changes with the growth of impervious a surface cohesion density,which has a clear "critical point",can be roughly divided into three types of intense,slow and stable.The land surface temperature varies from 0 to 10% with the density of t the impervious surface cohesion density;the land surface temperature between 10% and 40% varies slowly with the impervious surface cohesion density;the surface temperature is impermeable with water after 40%.The change in aggregation density is relatively stable.(6)According to the inflection point in the process of surface temperature change with the increase of aggregate density on impervious surface,the aggregation density of impervious surface in Jinan City is divided into three levels: low aggregation density area,middle aggregation density area and high aggregation density area.Both the impervious surface cohesion density and the land surface temperature grade show a tendency of focusing on the high-densityaccumulation area and the high-temperature area and gradually spreading outwards.There is a good agreement between the impervious surface cohesion density and the land surface temperature grade.