Thermal Comfort Evaluation And Human Thermophysiological Response Of Green Space In City Park

With the rapid urbanization all over the world,the emission of large amount of greenhouse gases has caused the aggravation of urban heat island effect(UHI),which not only affects the sustainable development of cities,but even poses a great threat to life and health.How to mitigate UHI and cooling the urban thermal environment has become a common concern for scholars in various fields.Urban parks not only provide outdoor green space for activities,but also have certain UHI mitigation and thermal comfort improvement effects which bring benefits to urban residents.In this study,we reviewed the related research progress at home and abroad,and found thatthe currently applied cooling effect evaluation indexes are mostly focused on the maximum perspective,and the evaluation of thermal comfort is mainly subjective and has not yet incorporated objective physiological indicators.At the same time,there is still a lack of coastal city cases and a lack of analysis of microclimate effects of multiple factor combinations.Therefore,this paper conducted a study on the cooling effect of urban parks in the main city zoo of Qingdao,the microclimate characteristics of green spaces and the evaluation of thermal comfort and human thermal physiological response of green spaces in urban parks.The main study contents and findings are as follows:(1)Based on Landsat-8 OLI/TIRS remote sensing images of Qingdao city,the cooling effect of 50 urban parks in the main city zoo of Qingdao was evaluated from both the maximum and accumulation perspectives.We found that the interior LST of50 urban parks was lower than the surrounding LST,with a meanΔT=2.36°C,indicating that urban parks in coastal cities have significant cooling effect.In addition,to take full advantage of the cooling effect,it is appropriate to design the parks without water within medium size(4-10hm~2)and parks containing water within large size(10-50hm~2)under the situation of land constraint.At the same time,the influence of the surrounding environment on the cooling effect of parks is huge.Urban parks established in densely populated areas have a significantly larger temperature difference(ΔT)between the inside and outside than those established in ecologically sound areas or emerging urban areas,and can cooling a wider range of urban environments with higher cooling intensity.Therefore,when doing urban planning,we should give priority to designing parks in medium and high density urban areas.(2)The microclimate of 36 typical outdoor green spaces in urban parks was measured by mobile measurements during the summer.The results show that the microclimate effect of 36 green space measurement points is significant.The average daily reduction in Air temperature(Ta)reached 3.26°C,the average daily reduction in Solar radiation(Sr)reached 619.10W/m2,the average daily increase in Relative humidity(Rh)reached 10.01%,and the average daily reduction in Physiologically equivalent temperature(PET)reached 15.14°C at the measurement points with good microclimate conditions.Whether near water,floor type and shade type have significant effects on the microclimate and thermal comfort of green space.The thermal comfort of measurement points close to water is better than that of measurement points far from water in the noon time,and the thermal comfort of the measurement points close to water decreases in the evening.In addition,building shade combined with surrounding plants can best improve the thermal comfort of green spaces.(3)In summer,microclimate measurements were conducted in seven green spaces with significantly different and representative spatial characteristics,and 52volunteers were organized to conduct subjective thermal comfort questionnaires and measurements of thermal physiological indicators.We found that,evaluation of thermal comfort by PET is applicable in Qingdao(R~2=0.843),and changes in physiological parameters caused by thermoregulatory activity can reflect the thermal comfort of the human body.Skin temperature(SKT),Heart rate variability(HRV(LF/HF)),Oxygen saturation(Sa O2)and Heart rate(HR)have high correlation with thermal comfort,and can be used as objective evaluation indexes of thermal comfort.SKT is proved to be an excellent objective indicator of thermal comfort with high reliability(R~2=0.803),moreover the measurement and calculation process is relatively simple.LF/HF and HR are influenced by individual differences and suitable for longitudinal comparisons of participants’thermal comfort in different microclimate environment.In this study,the UHI mitigation and thermal comfort improvement effects of urban parks in the context of global warming have been comprehensively revealed from different scales by remote sensing and field measurements.On the basis of the thermal comfort evaluation of typical green spaces,the human thermal physiological response regulation is further explored.This research results can provide scientific reference and data support for urban park planning and green space design.