A Study On The Influence Of Building Layout On Urban Thermal Environment Under Different Scales Of "urban-street"

Under the background of accelerating urbanization and industrialization,the quality of global climate environment is declining,among which the urban thermal environment problems are more obvious.The increase of tall buildings and high-density buildings in urban has changed the three-dimensional spatial form and land cover type,seriously affected the heat exchange process between solar radiation and urban surface and atmosphere,led to the deterioration of urban thermal environment quality,brought adverse effects on the sustainable development of urban,and reduced the thermal comfort of human body.Therefore,how to improve the urban thermal environment and enhance the thermal comfort of urban residents has become a common concern at present.At present,most studies on the impact of urban building on urban thermal environment are carried out based on the scale of cities or urban agglomerations by means of remote sensing,or by means of numerical simulation to analyze the microclimate of a certain street/community.However,there are limited studies on the impact of building layout on urban thermal environment by combining the two scales.Integrated remote sensing monitoring and numerical simulation can not only achieve a large spatial range of information acquisition,but also achieve higher spatial resolution and time continuity of the fine study.Building height,building density,floor area ratio and sky view factor are the key indicators to describe the spatial distribution of building layout,which have an impact on the spatial distribution of temperature.Therefore,this paper focuses on studying the relationship between the spatial form of building layout and thermal environment.We take the Fifth Ring Road area of Beijing as the research area,which is highly urbanized and has complex building layout.The research is carried out by means of comprehensive remote sensing monitoring,field measurement and numerical simulation,to explore the influence of various indexes of urban building spatial layout on urban thermal environment from the urban and street scale respectively.Firstly,on the urban scale,we extracted building height,building density,floor area ratio,sky view factor quantitatively based on the grid.We established the least square linear regression model(OLS)and geographically weighted regression model(GWR)to analyze the influence of various building layout indicators on LST from global and local perspectives.Secondly,on the street scale,we used the urban microclimate model ENVImet to construct six common building layout models,five building height models,four staggered high and low layout models and four building density models.Then we analyzed the spatial distribution of air temperature in each model scene,and calculated the area proportion of different temperature levels and the outdoor thermal comfort PET.The main results are as follows:(1)At the urban scale,building density is positively correlated with LST in summer and winter,building height and sky view factor are negatively correlated with LST in summer and winter,floor area ratio is not significantly correlated with LST,and the correlation between different indicators and LST has spatial heterogeneity.In this paper,building height,building density and floor area ratio were quantitatively extracted using building vector data,and sky view factor was obtained based on the hemispherical model principle.Landsat-8 data was used to invert summer and winter LST in the study area.The pearson correlation analysis reveals that building density was positively correlated with LST in summer and winter,and the correlation coefficients were 0.444 and 0.278,respectively;building height was negatively correlated with LST,and the correlation coefficients were-0.372 and-0.352;sky view factor was negatively correlated with LST,and the correlation coefficients were-0.313 and-0.201,respectively.There was no significant correlation between floor area ratio and LST.OLS results were consistent with Pearson results.The coefficient of building height and LST in summer was 3.35 and 0.76 in winter;the coefficient of building height and LST in summer was-2.04 and-0.22 in winter;the coefficient of sky view factor and LST in summer was-1.03 and-0.97 in winter.Based on the results of GWR,it is found that the influence of various layout indicators on LST exists spatial heterogeneity.In summer,building height is negatively correlated with LST in about 95%of the regions,and in winter,building height is negatively correlated with LST in about 90%of the regions.About 80%of the regions in summer showed a positive correlation between building density and LST,and about 66%of the regions in winter showed a positive correlation between building density and LST.About 87%of the areas in summer are negatively correlated with sky view factor and LST,and about 65%of the areas in winter are negatively correlated with sky view factor and LST.Moreover,compared with winter,the response of various indicators to LST is more significant in summer.(2)At the street scale,different building layouts have certain effects on the spatial distribution of temperature and PET,among which enclosed layout-L4 has a better performance than other layout models,building height and temperature are not a single negative correlation,the staggered layout of building height has a significant impact on the spatial distribution of temperature and PET,among which M2 has a better performance.When the building density is higher,a lot of shadow will be generated inside the area,resulting in lower temperature values.According to the common layout forms of buildings in Beijing,four experiments were constructed:scene experiment of building layout,scene experiment of consistent building height,staggered layout experiment of buildings high and low,and scene experiment of building density.By comparing the spatial distribution of temperature,the area proportion of different temperature classes and the outdoor thermal comfort were statistically analyzed,it was found that enclosed layout-L4 was better.There is no single negative correlation between building height and temperature.When the building height is lower than 30 meters,the temperature increases with the increase of building height;when the building height is higher than 30 meters,the temperature decreases with the increase of building height.In the experiment of staggered layout of buildings high and low,M2 can provide more low-temperature areas.Compared with the scene with the same building height,the temperature drop can be achieved by 0.5 ℃,showing a better performance.