Study On The Coupling Of Urban Public Space Landscape Characteristics And Wind-thermal Environment

The acceleration of urbanization highlights the urban heat island effect.The wind-thermal environment of urban public space deteriorates further due to high intensity artificial disturbance activities.Urban public space as a leisure place for daily activities of citizens,the environment comfort is very important.Understanding the coupling relationship between landscape characteristics of urban public space and wind-thermal environment can provide scientific basis for improving urban thermal environment.From the perspective of landscape characteristics,this paper selects 9 typical urban public space samples of 3 types in the Wuyi Road area of Changsha city center.Using ArcGIS data processing,the combination of actual measurement and ENVI-met simulation,SPSS coupling analysis and other methods,this paper studies the characteristics of landscape elements and wind-thermal environment change rules of urban public space.By summarizing the coupling relationship between the two,the optimization strategy of urban public space is put forward.The main conclusions are as follows:(1)Urban public space landscape feature index system.Based on the microclimate perspective,the landscape characteristics of urban public space were described by 17 indicators from three aspects:spatial environment,underlying surface and plant structure characteristics.The indicators were calculated from two aspects:the overall landscape characteristics of public space types and the specific landscape characteristics of each measuring point,and the characteristics of urban public space were quantified.Among them,the spatial environment index includes six indicators:average building height,building density,windward density,building sprawl,floor area ratio,and sky openness;while the underlying surface index includes four indicators:water area,hard pavement area,impervious water rate,and grass proportion.The index of plant structure includes seven indexes:tree crown width,tree height,tree branch height,shrub height,shrub crown width,three-dimensional green amount and canopy density.(2)Spatio-temporal characteristics of three typical spatial types of wind-thermal environment.In terms of time,the air temperature increases first and then decreases throughout the day,reaching the highest at 14:00.The relative humidity decreases first and then increases throughout the day,with the lowest value at 14:00.Wind speed has no obvious regularity.Spatial,air temperature:square>street>park,relative humidity:park>square>street,wind speed:street>square>park.The wind-thermal environment of urban park is generally better than that of city square and street,and the wind-thermal environment of measuring points with plant distribution is generally better than that of hard pavement measuring points.(3)Coupling law of landscape characteristic index and wind-thermal environment.Correlation analysis was carried out from the whole level,three typical spatial types and 52 measurement points.Spatial environment indexes and plant structure indexes mainly affect wind speed,while underlying surface indexes have different effects on temperature,humidity and wind speed.Landscape characteristic index factors affecting wind-thermal environment are different in three typical spatial types:Factors of sky openness,building sprawl,impervious water surface rate,height under tree branches and shrub crown width in city square;factors of average building height,windward density of buildings,floor area ratio,proportion of grassland,canopy density,height under tree branches and shrub height in city park;In urban streets,windward density,hard pavement area,impervious water ratio,grassland proportion,canopy density and three-dimensional green quantity have significant effects on wind-thermal environment.(4)Proposed optimization strategy and scheme verification.Urban squares can reduce the sky openness,increase the architectural scatter,and improve the height under trees;urban parks can improve the windward density of buildings,increase the proportion of grass,improve canopy density,and improve the height under trees;urban streets can improve canopy density,strengthen the shading effect of plants and improve the microclimate.Three samples were selected to design optimization schemes.By comparing the summer monsoon thermal environment data before and after optimization,it was found that the air temperature decreased and the relative humidity increased,which verified the feasibility of the optimization strategy.The optimization strategy can guide urban planning and design and improve the wind-thermal environment of urban public space.