Spatial Correlation Analysis Between Urban Heat Mitigation Index And Landscape Pattern

The heat island effect is one of the most serious problems among the many urban problems brought about by the accelerating urbanization process.With the extension of the impervious surface,the urban green space water body and other urban landscape patterns are fragmented.These changes further intensify the urban thermal effect and reduce the living experience of human beings.Therefore,the urban heat island effect has attracted widespread attention from all walks of life.This study attempts to quantitatively study the urban heat effect from the perspectives of urban building layout,hardened pavement,green space,and water bodies.Taking Beijing as the research object,the Invest urban cooling model is used to couple the land.Land use,vegetation shadowing,surface evapotranspiration,and albedo simulations are used to evaluate the thermal mitigation index of urban thermal effects,and to quantify the cooling capacity of urban green spaces and water.in addition,GeoDa is used to conduct global and local spatial correlations between the heat mitigation index and the urban landscape pattern index.The main research results are as follows:(1)The heat mitigation index distribution map under 9 cooling distance gradients under the characteristics of vegetation,vegetation&water was calculated by the Urban cooling model,and the surface temperature simulated by the atmospheric correction method was used to verify the results.Under the cooling characteristics,the cooling distance of 100m is the best condition for simulating the heat mitigation index.The heat mitigation index is significantly negatively correlated with the surface temperature,and the linear fitting R~2 is0.519.The R~2 is different under different land use types,and the best fitting conditions are different with different land use types.According to the simulation results,the shortage of model parameter settings and the introduction of more parameter optimization models are proposed in the future.(2)The distribution of landscape pattern indices of various land use types in Beijing was quantified,and the results showed that the area percentage of impervious surfaces in the central area of the city was higher than that in the surrounding areas,and each landscape index also indicated that the diversity of landscape patches in the city centre was higher.And forming a mosaic pattern of multiple land types and highly fragmented landscape patches.In the surrounding areas,it is characterized by low fragmentation and a single landscape pattern with green space as the main body.Overall,the green space in the central area of the city is relatively low.Fragmentation is high and its area percentage increases away from the city center,impervious surfaces show the opposite trend.(3)In order to further study the impact of urban landscape pattern on the thermal mitigation index,the global Moran’s I and local Moran’s I were used to analyze the spatial correlation between the landscape index and the thermal mitigation index at the class level and the landscape level.The results show that:(1)In the global correlation analysis,PLAND and COHESION of class-level have similar characteristics,that is,PLAND,COHESION and HMI of road,building and bare land are negatively correlated;In farmland and water,PLAND,COHESION and HMI were positively correlated;the SPLIT of class-level showed an opposite trend to the above two landscape pattern indices.Landscape-level including COHESION,LPI with HMI were significantly positively correlated,PD,CONTAG,SHDI and SHEI were significantly negatively correlated with HMI.(2)In the local spatial correlation analysis,the correlation analysis of COHESION and PLAND at the class level and HMI are similar,that is,the urban center has lower PLAND and COHESION at building,and has lower PLAND and COHESION at green space,which lead to a severe urban heat island effect in the city center,are reversed around the city;the SPLIT shows the opposite trend with the above two.The local spatial correlation at the landscape level showed that COHESION,LPI,PD,CONTAG,SHDI and SHEI had different aggregation degrees with HMI in different regions.In view of the above,this thesis quantifies the mitigation index of urban green space and water to the urban heat environment through Urban cooling,on the one hand,discusses the optimal parameters of the model for future research.On the other hand,by exploring the spatial correlation between the landscape pattern index and the heat mitigation index in the study area,we found that the impact of urbanization on the heat mitigation index can be mitigated not only by balancing the relative quantities of various land cover features,but also by optimizing their spatial configuration.In order to provide a theoretical basis for future urban planning of impervious surfaces,blue infrastructure(water),green infrastructure(green space),and a way to build a more reasonable urban cooling structure to achieve the purpose of improving the urban living environment.