The impact of tree species and planting location on outdoor thermal comfort of a semi-outdoor space

The impact of urban parks on the thermal environment of built-up areas and an optimization method

Rapid urbanization, while transforming people's living environments, also brings a series of urban issues such as the urban heat island effect. The urban park is an effective means to alleviate the urban heat island effect in summer. How to make better use of the cold island effect formed by urban parks to improve the urban outdoor thermal environment is an important topic. This manuscript takes Xi'an as the research area, using remote sensing data as the data source and combining field surveys, to explore the cooling characteristics of the cold island effect in the urban built-up area. It is demonstrated that, the influencing factors of the cooling effect of urban park cold islands are summarized: the area and perimeter of the park, the area and perimeter of water bodies, and the area of trees are all positively correlated with the cooling effect. The surrounding building density and building plot ratio are also positively correlated with the cooling effect of the green space. A comprehensive scoring model for each influencing factor is established, and the principal component analysis method is used to determine the weight of each indicator on the cooling effect of park design elements, among which the area of green space parks has the greatest influence weight. The demand space for cold islands in Xi'an's parks is analyzed, and optimization strategies and suggestions for improving the urban thermal environment are put forward from both inside and outside the park.

Approach for the vertical wind speed profile implemented in the UTCI basics blocks UTCI applications at the urban pedestrian level

The applicability of the Universal Thermal Climate Index (UTCI) at the urban pedestrian level is analysed in relation to the approach for the vertical wind speed profile (VWSP) used in the UTCI basics. As the UTCI refers to the human-biometeorological reference height (zh-b) of 1.1 m above ground level (agl), all meteorological input variables for UTCI calculations should also be originated from zh-b. Since the development of the UTCI considered meteorological conventions for stations routinely operated by national weather services, the wind speed (v) as one of four meteorological input variables is initially required at 10 m agl (v10 m). In order to calculate v at zh-b from v10 m, the logarithmic law for the VWSP is implemented in the UTCI basics, but only for neutral atmospheric stability and a roughness length (z0) for short-cut grassland (z0 = 0.01 m). This methodological approach cannot be changed in the UTCI basics so far. The UTCI developers also recommend the application of the same logarithmic law, if v values at lower heights have to be extrapolated to 10 m agl. However, the use of this VWSP approach disregards basic air flow findings and principles in the urban canopy layer (UCL). If the UTCI is nevertheless applied at the urban pedestrian level, inaccuracies in the UTCI values will occur. With reference to z0 = 0.80 m, which is more typical for the UCL, they can be up to 7 K, as shown in the example of three different climate zones.

Effects of tree species and planting forms on the thermal comfort of campsites in hot and humid areas of China

Camping has become a popular outdoor activity in China. However, the long and scorching summers in China's hot and humid regions pose challenges for campsites in maintaining thermal comfort. Therefore, we explored the impact of tree species and planting methods on the thermal comfort of urban campsites in hot and humid areas using the ENVI-met model to simulate the conditions of the study area. The reliability of the model was validated by comparing the simulated values of air temperature (Ta) and relative humidity (RH) with field measurements. We conducted an in-depth analysis of common trees in hot and humid areas and analyzed the effects of five tree species and four tree planting forms on the microclimate of campsites in such areas, using the physiological equivalent temperature (PET) as the evaluation index of thermal comfort. The results indicated that: (1) trees with larger crown widths were most effective in improving outdoor thermal comfort. The ability of trees to regulate microclimate was more influenced by crown width than by leaf area index (LAI), and (2) trees planted in patches provided the highest level of thermal comfort, whereas single trees provided the lowest. However, relying solely on tree planting made it difficult to significantly reduce outdoor heat stress. Therefore, other methods such as increasing ventilation or mist spray should be adopted to modify camping area. This study provides a reference for the planting design of outdoor campsites in hot and humid regions of China.

How outdoor horticultural activities affect elderly adults' thermal, physiological and psychological responses: a field study

We recruited 162 healthy elderly adults to determine the thermal, physiological, and psychological effects of horticultural activities (flower arranging, transplanting, and rubble masonry) in outdoor open spaces. We linked these to local climate conditions, physiology, and comfort through a questionnaire survey. The results showed that: (1) the neutral physiological equivalent temperature (NPET) before the horticultural activities were 22.18 ℃ for flower arranging, 23.67 ℃ for transplanting, and 20.78 ℃ for rubble masonry, while the NPET decreased to 18.53 ℃, 20.73 ℃ and 18.04 ℃ (respectively) after activities. (2) The heart rate and blood oxygen saturation changed significantly (p < 0.05) only after rubble masonry. (3) The average positive affect (PA) scores increased after flower arranging by 4.83, transplanting by 3.30, and rubble masonry by 4.00. (4) After activities, the thermal sensation vote was mainly influenced by globe temperature (41.36%), air temperature (33.47%), and wind speed (25.17%). Thermal comfort vote could be promoted because of 37.35% of an increasing positive and 21.20% of decreasing negative emotion.

The effects of different landscape strategies on outdoor thermal comfort in village squares: a case study in Dayuwan village in Wuhan City

Appropriate landscape configurations significantly mitigate rural thermal degradation. However, limited research exists on seasonal thermal comfort and the interconnections among landscape elements. Using ENVI-met software and field measurements, this study analyzed the microclimate of Dayuwan Village Square in Wuhan City. Fifteen design scenarios, including tree planting, building greening, albedo adjustment, and expanded tree coverage, were quantitatively evaluated to assess their impact on outdoor thermal comfort. Additionally, synergistic interactions between mitigation strategies were explored. The study found that increasing evergreen tree coverage by 50% has minimal impact on comfort during winter and spring. However, it significantly reduces temperatures in summer and autumn, resulting in average predicted mean vote (PMV) decreases of 0.315 and 0.643, respectively. Additionally, this strategy optimizes PMV values at 18:00 on extreme days, with a 0.102 decrease in summer and a 0.002 increase in winter. This research offers practical and sustainable guidance to designers for enhancing mitigation effects through optimal landscape configuration, providing a technical framework for rural environmental improvements.