街道可视因子对夏季午后城市街道峡谷微气候和热舒适度的影响研究

Influence of Street View Factors on Microclimate and Thermal Comfort of Urban Street Canyons in Summer Afternoon

城市街道作为城市最重要的活动空间,对其进行合理的规划和改造有利于改善城市热环境。揭示街道可视因子对街道峡谷微气候和热舒适度的作用机制,可以作为城市规划设计的理论基础。选取杭州市典型街道峡谷为研究对象,通过实测和数据分析发现,在夏季午后,不同街道峡谷内微气候和热舒适度存在明显差异:各街道峡谷之间空气温度、平均辐射温度和生理等效温度最大值与最小值之差分别达到了2.9、25.3和15.3℃;N-S朝向的街道热环境优于E-W朝向的街道,但街道的开敞程度和植物遮阴会抵消街道朝向的影响。研究也发现,在午后,街道可视因子会对街道峡谷热环境产生不同程度的影响,天空可视因子越高,街道峡谷空间越开敞,街道热环境和热舒适度越差;建筑可视因子与城市街道峡谷微气候和热舒适度相关性不大;而树木可视因子则对街道峡谷热环境具有重要影响,树木可视因子越高,街道树木的遮阴程度越高,街道内热环境和热舒适度越佳,这种现象在E-W朝向的街道峡谷中表现得更为明显。

As the most important activity space of city,urban streets are rationally planned and reconstructed to improve the urban microclimate.Revealing the mechanism of street view factors on the microclimate and thermal comfort of street canyons can be used as the theoretical basis for urban planning and design.This study selects typical street canyons in Hangzhou as the research object.Through actual measurement and data analysis,it is found that there are obvious differences in microclimate and thermal comfort in different street canyons in the summer afternoon.The results show that in the summer afternoon,even in small-scale urban blocks,there are significant difference in microclimate and thermal comfort in each street canyon.The difference between the maximum and minimum values of air temperature,mean radiation temperature and physiological equivalent temperature between the street canyons reached 2.9,25.3,and 15.3℃,respectively.The N-S orientation street canyons’thermal environment tends to be superior to the E-W orientation street canyon,but the openness of the street canyon and tree shading can offset the impact of street orientation.At the same time,the study also find that the street view factors have different influence on the street canyon.The higher the sky view factor,the more open the street canyon space,and the worse the thermal environment and thermal comfort in the street canyon.Building view factor is less relevant to the microclimate and thermal comfort of urban street canyons.The higher the tree view factor,the higher the shade of the trees and the better the thermal environment and thermal comfort in the street.This phenomenon is more pronounced in the E-W orientation street canyons.