Coupling outdoor air quality with thermal comfort in the presence of street trees:a pilot investigation in Shenyang,Northeast China

Together,the heat island eff ect and air pollution pose a threat to human health and well-being in urban settings.Nature-based solutions such as planting trees are a mitigation strategy to improve outdoor temperatures(thermal comfort)and enhance air quality in urban areas.In this study,outdoor thermal comfort,and particulate matter levels were compared between treeless and treed areas to provide a better understanding of how street trees improve thermal comfort and air quality.Street trees decreased the physiological equivalent temperature from 46.3 to 44.2℃in summer but increased it from 36.4 to 37.5℃in autumn.Air temperature and relative humidity contributed more in summer while wind speed contributed more in autumn.Particulate matter concentrations were negatively correlated with physiological equivalent temperature in summer but not in autumn.The presence of trees decreased concentrations of fi ne particulate matter in hot summer conditions but increased in hot autumn conditions.The presence of trees increased coarse particulate matter in very hot summer conditions in summer and in hot autumn conditions.Overall,the layout of trees in urban street canyons should consider the trade-off between outdoor thermal comfort and air quality improvement.

Research on Thermal Comfort of Outdoor Space in Summer Urban Park: Take Mianyang Urban Park as an Example

One of the factors for the evaluation of the space environment is the comfort of outdoor activities spaces in urban parks. The space composed of different landscape elements has different microclimate environment. In this paper, in order to evaluate the role of thermal comfort in influencing resident’s assessment of the outdoor space and activities of the park, a thermal comfort survey was conducted on the outdoor open space of Mianyang Urban Park in summer. In this article, meteorological surveys, questionnaire surveys and observation of park attendance are selected to collect data. The physiological equivalent temperature (PET) assessment was selected as the index to evaluate resident’s thermal comfort level, and the comprehensive evaluation and analysis of the spatial thermal environment of different outdoor landscape elements in the park. The overall comfort of current visitors is mainly influenced by their subjective heat perception voting (TSV). In this article, we focus on providing microclimate adjustment considerations for urban park landscape design, and may help people understand the outdoor thermal comfort of Mianyang in summer, increase the using time of outdoor activities, and promote the use of outdoor space.

Effects of mask wearing duration and relative humidity on thermal perception in the summer outdoor built environment

During the pandemic,face masks are one of the most significant self-protection necessities,but they also cause heat stress.By using the ERA5(ECMWF Reanalysis 5th Generation)database and the local weather bureau data,the effect of mask wearing on outdoor thermal sensation has been investigated by a survey conducted in the hot summer and cold winter region of eastern China in the summer of 2020.Results show that wearing a face mask for a longer period result in a higher level of discomfort,and the primary source of discomfort is hot and stuffy feelings.The effect of relative humidity is crucial for mask wearers in warm-biased thermal environments,as mean thermal sensation vote(TSV)peaks when environmental relative humidity reaches the range of 70%to 80%and decreases after this range due to the evaporation within the microclimate created by a face mask.Meanwhile,prolonged mask wearing increases participants’hot feelings,especially in warm environments.Specifically,participants wearing face masks for less than 30 min feel hot at a physiological equivalent temperature(PET)value of 34.4℃,but those who wear them for over 60 min express hot feelings even at a PET value of 24.7℃.The participants who wear a face mask while walking slowly outdoors have similar thermal sensations to those who do not wear a mask,but are in a higher activity level.The findings demonstrate that mask wearing has a crucial impact on outdoor thermal comfort assessment in a warm-biased outdoor thermal environment.