Microclimate Effect Of Urban Green Space And Its Influence On Human Comfort

Urban heat island effect as the most prominent symbol of urban climate change caused by urbanization,has been widely concerned by scholars all around the worl.Scientific mitigation of urban heat island effect has great significance to the construction of livable environment of cities.The green space can effectively alleviate urban heat island effect.In recent years,it has become an important trend for the development of microclimate research to use the numerical simulation platform to study the influence mechanism of green space microclimate.This study combined numerical simulation and field measurement to analyze on the micro scale the microclimate characteristics of different land cover types of park green space in spring,summer and autumn,and quantitatively analyzed the correlation between land cover composition and the microclimate effect and human comfort of green space.The field observation method was used to study on the block scale the cooling and humidifying influence pattern of urban green space on the surrounding urban open space,and the numerical simulation method was used to study the influence of internal factors of block scale urban open space on the microclimate effect and human comfort.The research results will provide theoretical basis and data support for urban green space to maximize the mitigation of urban heat island effect,provide practical guidance for urban green space planning and design,and contribute to the construction of comfortable residential thermal environment.The main conclusions are as follows:(1)On micro scale,there were significant differences in microclimate effect and human comfort level between different land cover types,and different land cover types had different effects on microclimate and human comfort.Land cover had extremely significant influence on its microclimate effect in spring,and extremely significant influence on its air temperature and cooling effect in summer and significant influence in autumn.Land cover had no significant influence on its relative humidity and humidifying effect in summer and autumn.The cooling and humidifying effect in three seasons of woodland was the best,and building was the worst.Land cover type had extremely significant influence on its human comfort in spring and summer,and significant influence in autumn.The human comforr of woodland was the best,and building was the worst.In general,the cooling and humidifying effect and human comfort improvement effect of woodland were prominent,followed by water body,and building was the weakest.Moreover,the microclimate characteristics of woodland and other land cover types were significantly different.The woodland proportion in green space was positively correlated with the effect of cooling and humidifying and the improvement of human comfort.The higher the woodland proportion was,the better the cooling and humidifying effect of green space was,and the higher the human comfort level was.(2)On micro scale,Green space inside every 5%increased in woodland area and reduced the corresponding area of the paving,the temperature decreased 0.26?,humidity increased 1.27%-1.30%,the human comfort in thermal humidity index decreased by 0.02-0.03.The cooling and humidifying effect of the woodland was better than that of the lawn.In the rate of green space in a certain situation,per 5%of the woodland replaced with lawn in green space could reduce the average air temperature 0.29 ? the average relative humidity could be increased with 1.18%,the human comfort level increased by 0.06.(3)On block scale,the green space had an obvious cooling and humidifying effect on the surrounding cities environment within 1km.The distance attenuation effect of cooling and humidifying effect of green space on different urban open space was different.The cooling effect of green space on open green space had extremely significant distance attenuation effect.When 250m distance increased,average air temperature of open green space increased by 1.29?.The humidifying effect of green space on waterfront green space had significant distance attenuation effect.When 250m distance increased,average relative humidity of waterfront green space decreased by 2.1%.The human comfort improvement effect of green space on open green space had extremely significant distance attenuation effect.When 250m distance increased,human comfort of open green space decreased by 0.62.The results showed that the closer open green space to the large park had the lower the air temperature and the better human comfort level,and the closer waterfront green space to the large park had the higher the relative humidity and park green space had the weakest effect on the square on the air temperature and humidity.The open space typs had an extremely significant influence on its cooling and humidifying intensity.The cooling intensity from high to low was open green space>waterfront green space>square,and the humidifying intensity from high to low was waterfront green space>open green space>square.It had an extremely significant influence on the improvement effect of human comfort.The effect from high to low was waterfront green space>open green space>square.Among all kinds of urban open space,open green space had the best cooling effect,and waterfront green space had the best humidifying effect and human comfort improvement effect.(4)On block scale,the compositons of land cover type could affect the microclimate and human comfort at the block scale.After 8%lawn replaced with woodland in the research area,regional air temperature reduced 0.05?,and relative humidity increased 0.09%,and the human comfort increased 0.39 ?.8%paving replaced with woodland on the basis of this situation,regional air temperature reduced 0.08 ?,and relative humidity increased 0.12%,and the human comfort increased 0.84?.The layout of green space had an important influence on the local cooling and humidifying effect.Under the condition of a certain proportion of each cover land area,increasing the area of woodland down the dominant wind direction outside the building played a positive role in adjusting the microclimate environment outside the building,improving the effect of regional cooling and humidification,and improving its comfort level.