Outdoor thermal comfort studies have mainly examined the perception of local residents, and there has been little work on how those conditions are perceived differently by tourists, especially ...tourists of diverse origins. This issue is important because it will improve the application of thermal indices in predicting the thermal perception of tourists. This study aims to compare the differences in thermal perception and preferences between local and overseas visitors to the Royal Botanic Garden (RBG) in Melbourne during summer. An 8-day survey was conducted in February 2014 at four sites in the garden (
n
= 2198), including 2 days with maximum temperature exceeding 40 °C. The survey results were compared with data from four weather stations adjacent to the survey locations. One survey location, ‘Fern Gully’, has a misting system and visitors perceived the Fern Gully to be cooler than other survey locations. As the apparent temperature exceeded 32.4 °C, visitors perceived the environment as being ‘warm’ or ‘hot’. At ‘hot’ conditions, 36.8 % of European visitors voted for no change to the thermal conditions, which is considerably higher than the response from Australian visitors (12.2 %) and Chinese visitors (7.5 %). Study results suggest that overseas tourists have different comfort perception and preferences compared to local Australians in hot weather based at least in part on expectations. Understanding the differences in visitors’ thermal perception is important to improve the garden design. It can also lead to better tour planning and marketing to potential visitors from different countries.
Validated by wind tunnel data, this study numerically investigates the integrated impacts of wind and thermal buoyancy on urban turbulence, ventilation and pollutant dispersion in full-scale 2D deep ...street canyons (aspect ratio AR = H/W = 3 and 5, W = 24 m). Isothermal urban airflows for such deep street canyons can be Reynolds-number-independent when reference Reynolds number (Re) exceeds the critical Re (Rec~106,107 when AR = 3, 5), i.e. AR = 5 experiences two main vortices and one-order smaller NEV* (~10−3, the normalized net escape velocity) than AR = 3 with a single main vortex (NEV*~10−2).
With sufficiently large Re (Re > Rec) and the same air-wall temperature difference (Ri = 2.62, 4.36 when AR = 3, 5), four uniform wall heating patterns were considered, including leeward-wall heating (L-H), windward-wall heating (W–H), ground heating (G-H), and all-wall heating (A-H). Various indicators were adopted to evaluate street ventilation and pollutant dilution capacity (e.g. age of air (τ,s), NEV*, pollutant transport rates (PTR)). Full-scale wall heating produces a strong upward near-wall buoyancy force, which significantly influences flow patterns and improves street ventilation for most cases. When AR = 3, L-H strengthens the single-vortex airflow. When AR = 5, L-H converts the isothermal double vortices into a single-clockwise vortex. For both ARs, W–H reverses the main clockwise vortex to an enhanced counterclockwise one, moreover G-H and A-H cause a more complicated multi-vortex pattern than isothermal cases. Overall, when AR = 3, L-H and W–H increase NEV* by 68% and 40% than the isothermal case. When AR = 5, four wall heating patterns all raise NEV* considerably (by 150%–556%). For both ARs, the L-H, W–H and A-H amplify the contribution of mean flows on removing pollutants but reduce that by turbulent diffusion compared with isothermal cases.
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•We use CFD to study how wall heating affects ventilation in deep street as Ri~2,4.•2D canyon flow is Re-independent as Re exceeds Rec (~106, ~107 as H/W = 3, 5).•Leeward, windward, ground and all wall heating greatly alter street flow pattern.•Ventilation improves with lateral wall heating as AR = 3 and all four types as AR = 5.•Lateral/all-wall heating raise contribution of mean flows on pollutant removal.
The Universal Thermal Climate Index (UTCI) is an index for assessing outdoor thermal environment which aims to be applicable universally to different climates. However, the scale of UTCI thermal ...stress classification can be interpreted depending on the context. Previous studies validated the UTCI in individual cities, but comparative studies between different cities are scarce. This study examines the differences in thermal perception and clothing choices between residents from two climate zones over similar UTCI ranges in summer. We compared summer thermal comfort survey data from Melbourne (
n
= 2162, January–February 2014) and Hong Kong (
n
= 414, July–August 2007). We calculated the UTCI from outdoor weather station data and used
t
tests to compare the differences in thermal sensation and clothing between Hong Kong and Melbourne residents. When the UTCI was between 23.0 and 45.9 °C, Melbourne residents wore significantly more clothing (0.1 clo) than Hong Kong residents. Hong Kong residents reported neutral to warm sensation at a higher UTCI range compared with the dynamic thermal sensation (DTS) model. Moreover, Melbourne residents reported warm and hot sensation at a higher UTCI range than the DTS model. Respondents in Melbourne also exhibited different responses to the mean radiant temperature under shaded and sunny conditions, while such a trend was not observed in Hong Kong. It would be advisable to define different thermal sensation thresholds for the UTCI scale according to different climate zones for better prediction of the outdoor thermal comfort of different urban populations.
People are exposed to multiple stimuli in urban environments, but most studies have investigated the unimodal effect of thermal and visual conditions on human comfort perception. It remains unclear ...whether the cross-modal effect found in indoor multisensory studies applies to outdoor environments. To understand the cross-modal effect of thermal and visual conditions on outdoor comfort perception, we conducted a thermal comfort survey (n = 4304) in Guangzhou and Zhuhai (September 2018). We used the Universal Thermal Climate Index (UTCI) heat stress classification and sky conditions to stratify our results. The thermal sensation vote was positively correlated with sun sensation vote. There was a significant interaction between UTCI heat stress conditions and sunlight preference vote on thermal comfort vote. The sun sensation (brightness) and sunlight preference vote had a cross-modal effect on thermal sensation and thermal comfort vote under various UTCI heat stress conditions. Under extreme heat stress, respondents’ thermal sensation did not differ significantly between different sun sensation and sunlight preference groups. Thermal sensation, preference and comfort vote had a cross-modal effect on sun sensation and sunlight preference under different sky conditions. Under partly cloudy conditions, sun sensation did not differ significantly between certain thermal sensation and preference groups. A theoretical framework is provided to explain the cross-modal effect between thermal and visual perception. Our findings suggest outdoor thermal discomfort can be alleviated by improving visual comfort and vice versa. Therefore, urban design should consider the combined effect of visual-thermal stimulants in optimizing overall pedestrian comfort and promoting urban liveability.
•Outdoor thermal sensation is positively correlated with sun sensation.•Cross-modal effect exists between outdoor thermal and visual comfort.•Significant association is found between thermal perception and sunlight preference.•Interaction between UTCI and sunlight preference on thermal comfort is significant.•Provide theoretical framework to explain cross-modal effects in comfort perception.
Home environment is suggested to be an essential influencing factor for asthma development or asthma exacerbation. However, the association between home environment and childhood asthma among ...preschool children in the hot humid subtropical region in South China is unclear. We investigated doctor-diagnosed asthma in preschool children due to the parental perception of odors in homes. A total of 1946 children aged from 3 to 6 years from 22 kindergartens in Foshan were randomly recruited for this study in May 2016. The associations among childhood asthma, indoor environment and parental perceptions of odors were examined by using logistic regression model in terms of odds ratio (OR) and 95% confidence interval (CI). Parental atopy had the highest risk for childhood asthma with odds ratio = 6.007 (95% CI: 2.369–15.231). Parental perception of dry air significantly increased asthma with odds ratio = 1.284 (95% CI: 1.027–1.606). The parental perceptions of odors were strongly related with new furniture at home. We conclude that parental perception of dry air is a risk factor for the increase of childhood asthma in the present study. Hence, our study indicates a need to control the household humidity level and reduce the usage of new furniture, in order to reduce the risk of childhood asthma in South China.
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•We addressed the indoor environmental health effect in subtropical South China.•Parental perception of dry air significantly associated with childhood asthma.•We found high correlation between parental perceptions of dry air and new furniture.•Prevalence of asthma in Foshan is lower than most cities in China.
Internal migration from rural to urban areas is prevalent in China. Past studies demonstrated that thermal adaptation differed among people from various climate regions. However, the outdoor thermal ...comfort of exercising people with a diverse climatic background remains largely unexplored. This study examines the relationship between short-term physiological and psychological thermal adaptation and outdoor thermal comfort of exercising people from different climate zones in China. We recruited first-year students (n = 145) who engaged in outdoor training between 3 and September 14, 2018 in Guangzhou, China. Physiological parameters include heart rate (HR) from fitness trackers and skin temperature (Tskin) from iButtons. These students were surveyed regarding their thermal comfort and psychological state over the study period (n = 968). Physiological Equivalent Temperature (PET) was calculated from weather station data at the training sites. T-tests reveal differences in HR and thermal perception between local and non-local students, but not Tskin. Under similar PET conditions, non-local students reported a higher thermal sensation and greater thermal discomfort than local students during the first week of training. Logistic regression indicates that HR and metabolic rate predict the thermal sensation of non-local students, but not local students. Wind sensation, pleasantness level, fatigue, and perceived suitability for outdoor activities are significant predictors of local and non-local students' thermal comfort. Our research highlights both physiological and psychological factors (including emotion and fatigue) are necessary to understand acclimatized and non-acclimatized people's thermal perception. Addressing thermal discomfort at an early stage can prevent more severe heat-related illnesses.
•Wearable sensors and surveys assess physiological and psychological adaptation.•Physiological adaptation is shown by changes in heart rate and metabolic rate.•Psychological adaptation is shown by lower thermal sensation at similar PET.•BMI, heart rate and metabolic rate predict non-local students' thermal sensation.•Emotion and fatigue predict outdoor thermal comfort of local and non-local students.
Changes in urban geometry significantly alters the urban microclimate. Suitable urban geometrical layouts can effectively improve the urban thermal environment to achieve a more sustainable and ...healthier city. A quantitative assessment of the relationship between the urban geometry and thermal environment is essential to provide scientific guidance for better urban and building design. Hence, we performed a scaled outdoor measurement to investigate the diurnal variations in air, and west and east wall temperatures within two-dimensional (2D) street canyons. We adopted the daily average temperature T‾, daily temperature range DTR, and hottest time tmax to describe the diurnal temperature characteristics. The influence of aspect ratios was considered (building height/street width, H/W = 0.5, H = 0.5 m, and H/W = 1, 2, 3, 6, H = 1.2 m). Canyon air experienced a smaller T‾ and DTR compared with the east and west walls. With an increase in the aspect ratio, no significant difference was observed in the T‾ of canyon air. The east and west walls of H/W = 2, 3, and 6 experienced lower T‾ (26.1–26.9 °C) and smaller DTR (11.7–18.4 °C) than those of H/W = 0.5, 1 (T‾=26.7–28.7 °C and DTR = 16.0–26.1 °C). A higher phase lag of tmax occurred between H/W = 0.5, and H/W = 6. As the aspect ratio increased, the differences in T‾, DTR, and tmax between the east and west walls decreased. This study improves our understanding of how urban morphology influences urban thermal environment and provides meaningful references for urban planning. Such high-quality experimental data can be used to validate and further improve numerical simulations and theoretical models.
•Diurnal temperature variations within 2D street canyons are studied in SOMUCH.•Impact of aspect ratios (H/W = 0.5, H = 0.5 m; H/W = 1, 2, 3, 6, H = 1.2 m) is evaluated.•FFT is applied to obtain more generalized daily temperature characteristics.•Wider street exhibits larger daily temperature range (DTR) and earlier hottest time.•Not all diurnal temperature characteristics vary linearly with the aspect ratio.
Previous indoor studies found that lighting intensity and visual comfort can affect human thermal comfort. However, it is unclear whether this relationship applies in outdoor environments. This study ...examines the impact of solar radiation intensity on outdoor thermal comfort in sites with different shading levels. This study used meteorological measurement to calculate the Universal Thermal Climate Index (UTCI), and compared it with thermal comfort survey data (n = 2198) in the Royal Botanic Garden Melbourne in February 2014. It was found that when UTCI was 25.0 °C – 36.9 °C, visitors to Fern Gully (a highly shaded site) felt significantly hotter at higher incoming solar radiation intensities (> 900 w/m2). However, there was no significant difference in people’s thermal sensations between different levels of solar radiation in less shaded sites. The hypothesis was that visual comfort brought by shading could affect how people perceive thermal comfort in outdoor environments.
Variations in human thermal perception have been described on timescales from minutes to seasons. However, the effect of weather-related thermal extremes on inter-daily changes to outdoor thermal ...perception has not been well characterised. This study used human thermal comfort data from an outdoor botanic garden in sub-urban Melbourne, Australia as a case study. We examined inter-daily variations in local visitors’ thermal perception before (11–12 January 2014) and after (18–19 January 2014) a severe heatwave from 14 to 17 January 2014, when daily maximum temperature exceeded 41 °C for 4 consecutive days. We compared thermal comfort survey results (pre-heatwave:
n
= 342, post-heatwave:
n
= 294) with air temperature and the Universal Thermal Climate Index (UTCI) measurements. Even though the days preceding and following the heatwave had a similar range in temperature (19–25 °C) and UTCI (26–32 °C), the visitors felt cooler in the days following the heatwave (i.e. lower thermal sensation votes). In the 2 days following the heatwave, visitors also wore less clothing compared with before the heatwave. Our results show that the thermal perception of visitors changed significantly following their exposure to the heatwave, even after controlling for changes in clothing choices and the ages of survey participants. Psychological adaptation to heat (such as thermal history and expectation) might be one of the possible explanations for this inter-daily variability of local visitors’ thermal perception.
Outdoor thermal comfort could significantly affect the usage and success of urban places. Accordingly, it is recommended to be considered in both urban design and planning projects. Urbanisation has ...been recognised as a major factor in elevated daily temperature values in Australia. This study aims to investigate the past and current position of outdoor thermal comfort studies in the Australian context. A critical review is conducted to examine the quality of thermal comfort assessment in Australia's cities. Twenty-five studies were reviewed to give a precise overview of past thermal comfort studies. The review scrutinises the focus of research, methodologies applied, data collection methods and results. This review helps main stakeholders in urban development better understand the evolution of outdoor thermal comfort with respect to liveability. In this line, where possible, the shortcomings are identified, certain solutions are provided and the need for further research is highlighted. In particular, future studies are necessary to cover missing geographical regions and ethnicities that are not considered in the existing literature. Furthermore, more psychological thermal adaptation studies are necessary, especially in transient thermal conditions. Qualitative analysis is also recommended to be incorporated in further studies in addition to considering the perceived environmental quality. The study serves as a reference to researchers, urban designers and planners to enhance their knowledge for achieving outdoor thermal comfort and understanding the gaps that need to be addressed in further studies.
•Intra-urban difference in outdoor thermal comfort depends on site characteristics.•Further studies required to cover missing geographical regions and ethnicities.•Psychological thermal adaptation studies needed, including transient conditions.•Qualitative approach can evaluate urban space types and thermal adaptation.•Perceived environmental quality can be considered to assess outdoor thermal comfort.
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