Cooling And Humidifying Effect Of Green Space In Summer

Under the influence of climate warming and urbanization,urban heat island effect is one of the most prominent environmental problems in cities.Urban heat island effect not only threatens the urban ecological environment and sustainable development,but also endangers the health and thermal comfort of citizens.Urban green space is considered to be one of the most effective measures to mitigate the urban heat island effect.At present,there are few studies on the effects of greenbelt cooling and humidification and the spatial pattern changes of temperature and humidity in Greenbelt patches with different canopy density.Now there is insufficient research on the effects of different canopy density on the cooling and humidification of park green space and the spatial pattern change of temperature and humidity of green patches.Based on this,taking Beijing Olympic Park as an example,this study selected six green patches with different canopy density and three different sizes.By field observation,the effects of greenbelt with different canopy density on temperature and humidity increase and the spatial distribution of greenbelt patches were studied.Combined with the calculation method of human comfort,the improvement effect of greenbelt on human comfort was analyzed.The purpose of this study is to provide reference for the planning and design of park green space.The main conclusions of this study are as follows(1)Temperature and humidity of park green space showed a regular single-peak change trend.The temperature of green space in parks increases first and then decreases,while the relative humidity is on the contrary,and peaks and valleys are reached in the high temperature period of a day(2)The cooling and humidifying effect of park green space with high canopy density is better than that of park green space with low canopy density.Park green space with different canopy density showed significant cooling and humidifying effects,and their cooling and humidifying intensity were different.The order of cooling and humidifying intensity was:canopy closure 69.2%>canopy closure 59.7%>canopy closure 29.9%>canopy closure 20.6%>canopy closure 16%>canopy closure 8%(3)The canopy density of park green space was positively correlated with its cooling and humidifying effects in daytime.The correlation between canopy density and its cooling effect was the strongest at 14 o'clock(R2=0.85),and the strongest at 12 o'clock(R2=0.85).In the high temperature period,the correlation between the canopy density and its cooling effect(R2=0.85)is stronger than its humidification effect(R2=0.83)(4)Temperature and humidity spatial distribution of park green patches is heterogeneous.Generally speaking,the internal temperature and humidity of the park green patches are low,while the surrounding temperature and humidity are high,but the change law is not obvious.Compared with temperature,the humidity heterogeneity of park green patches is weaker.(5)The park green space has obvious cooling and humidifying effect,and the effect of improving human comfort reaches 0.14-2.75,with an average improvement of 1.12.It can reduce the thermal sensation and form a "cold island effect" at the urban scale,providing a comfortable outdoor activity environment for urban residents.