| The article focuses on Beijing with specific climate conditions and urban spatial form,focusing on 38 urban parks within the Third Ring Road of high-density urban areas as examples.The influence mechanism of parks landscape composition and configuration on the cooling effect of urban parks are studied.Firstly,based on Landsat 8 remote sensing images,the atmospheric correction method is used to invert surface temperature,and the spatial characteristics of the thermal environment within the Third Ring Road of Beijing are analyzed and summarized.The surface temperature of inside and surrounding buffer zones of the parks are extracted,and the cooling magnitude and cooling scope of the parks are further calculated according to the cooling pattern model to reveal the current characteristics of the cooling effect of the urban parks.Secondly,based on the high-resolution Gaode image map,the parks’ internal substrate is classified into three types of green areas,water bodies and impermeable surfaces using supervised classification and manual visual interpretation.The landscape composition and configuration of urban parks are quantified by selecting the patch area share,landscape shape index,landscape fragmentation index and aggregation index from the level of landscape elements according to the principle of landscape ecology to summarize the landscape composition and configuration of urban parks within the Third Ring Road of Beijing.The current characteristics of the landscape composition and configuration of urban parks in Beijing are summarized.Finally,a classification study is conducted according to the presence or absence of water bodies in the parks.The quantitative indexes of urban parks’ landscape composition and configuration are correlated with the average temperature,cooling magnitude and cooling scope inside the parks,respectively,to deeply explore the mitigation effect of urban parks’ landscape composition and configuration on the thermal environment,and to obtain the factors that have a more significant influence on the cooling effect of the parks in urban parks landscape composition and configuration,and through stepwise regression method to establish a relationship model of the influence of urban parks landscape composition and configuration on the cooling effect of parks,and the following conclusions are drawn:(1)The heat island effect is significant within the Third Ring Road of Beijing,with the highest surface temperature of 46.06°C and an average of 39.64°C.The high-temperature areas are roughly distributed in a block-like concentration,the secondary high-temperature areas are concentrated in the space of urban roads and building sites,and the overall circular gradient gradually decreases from the center to the surroundings.The urban parks distributed among them are essential as "cold islands" breaking the large-scale concentrated heat island patches.(2)Among the 38 urban parks selected for this study,the landscape composition is divided into two types: a dryland park with large green areas and a water park with large water bodies.Significant differences exist in the proportion of landscape elements between the two types of parks.As for the configuration of the parks,the shape complexity of the green space patches is slightly higher than that of the impervious surface,but the shape complexity of both is much higher than that of the water body;the landscape fragmentation of the impervious surface is the highest,followed by the water body,and finally the green space;the aggregation of the green space patches is the highest,followed by the water body,and the aggregation of the impervious surface patches is the lowest.(3)The cooling effect of urban parks has noticeable "spillover",and the regulation effect on the surrounding urban thermal environment gradually decreases with increasing distance;the urban environment in which the parks is located,the area of the parks,and whether the parks contains water bodies all have different degrees of influence on the average temperature,cooling magnitude and cooling scope inside the parks.(4)The correlation between the quantitative indicators of landscape composition and spatial configuration and the average temperature,cooling magnitude and cooling scope is conducted for urban parks with and without water bodies.The cooling effect of parks without water bodies is significantly correlated with the percentage of green area,green landscape shape index,green landscape fragmentation,green patch aggregation,the percentage of impervious surface area,impervious surface landscape shape index,impervious surface landscape fragmentation,and impervious patch aggregation.In addition,by conducting stepwise regression analysis on the above significantly correlated indicators and the cooling effect of the parks,the relationship model of the influence factors on the average temperature,cooling magnitude and cooling scope of urban parks is obtained,which can better reveal the influence mechanism of the cooling effect of the urban parks.This study proposes parks optimization design recommendations for reducing the average internal temperature,enhancing the cooling magnitude and cooling range,respectively,to complement urban parks climate adaptation design theories and provide a favorable reference for the renewal and renovation of parks in the high-density central city of Beijing in response to future climate change in the context of stock planning. |
