Outdoor thermal comfort models are predominant in guiding urban design and outdoor space usage. Both the heat balance of the human body and thermal adaptations significantly affect outdoor thermal ...comfort. This study proposes adaptive-rational outdoor thermal comfort models to account for the heat balance and thermal adaptations simultaneously. Two widely used rational thermal indices of outdoor thermal comfort, i.e., Physiological Equivalent Temperature (PET) and Universal Thermal Climate Index (UTCI), are implemented to account for the heat balance. The adaptive and extension methods are implemented based on the rational thermal indices to develop the adaptive-rational outdoor thermal comfort models. The validation results show that compared with the PET-based rational model, the PET-based adaptive-rational models with adaptive and extension methods improve the accuracy and robustness by up to 83% and 86% respectively. Compared with the UTCI-based rational model, the UTCI-based adaptive-rational models with adaptive and extension methods improve the accuracy and robustness by up to 87% and 87% respectively. The proposed adaptive-rational outdoor thermal comfort models contribute to developing livable urban environments.
•PET-based and UTCI-based adaptive-rational outdoor thermal comfort models are developed.•Adaptive and extension methods are employed to develop adaptive-rational outdoor thermal comfort models.•Proposed models are validated by field data of different climate types, thermal sensation scales, and metabolic rates.•Proposed models improve accuracy and robustness by up to 87%.
Cities are becoming hotter day-by-day because heat is trapped near the earth's surface due to a decrease in green cover, rapid urbanization, energy-intensity activities, and concrete structures. The ...four major metropolitan cities of India, i.e. Kolkata, Chennai, Delhi and Mumbai, have experienced heat waves and heat stress frequently during the summer season. This study analyses heat wave and heat stress patterns in these cities using 30 years of data from 1990 to 2019 during the summer season. We used daily maximum temperature, relative humidity, wind speed and solar radiation datasets for the above mentioned period in this study. To understand the episode of a heat wave, we have used the 95th percentile method. Furthermore, we have also used Humidity Index (HD) to evaluate the degree of discomfort and the Universal Thermal Climate Index (UTCI) to categorize the level of heat stress. The analysis indicates that the number of heat wave events in the Delhi region is 26.31%, 31.58% and 63.16% higher than Kolkata, Chennai, and Mumbai regions respectively. It is also seen that the risks of extreme heat stress and dangerous-heat stroke events in the Chennai region during heat wave periods are higher than that experienced in other metropolitan cities because of high temperature with higher values of relative humidity. The risk of extreme heat stress is less in Delhi because of lower relative humidity compared to other metropolitan cities although temperature is higher in this region. However, the risk of extreme heat stress is lower in Mumbai region because of relatively lower temperature than Chennai during summer season. The likelihood of experiencing great discomfort during heat wave periods in Kolkata city is higher than that experienced in other metropolitan cities in India, however, during non-heat wave periods the probability of extreme discomfort is higher in Chennai.
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•Number of heat wave events in the Delhi region is higher than Kolkata, Chennai, and Mumbai.•The risks of extreme heat stress and dangerous-heat strokes in the Chennai region is higher than other metropolitan cities.•The great/extreme discomfort level during heat/non-heat wave period is higher in Kolkata/Chennai than other cities in India.
Due to limits to standard methods for surveying outdoor thermal comfort (OTC), it is difficult to compare thermal benchmarks and thermal index calibrations among studies and climatic regions. Using ...uniform standard meteorological measurements and questionnaire surveys, our study conducted an OTC study in urban parks in Beijing, Xi'an and Hami; representative of cities in China's cold regions. The Universal Thermal Climate Index (UTCI) was used as the thermal comfort index, and differences in residents' thermal perceptions and outdoor thermal benchmarks among these cities were compared. Results showed that: 1) air temperature (Ta) and globe temperature (Tg) were two primary factors affecting residents' thermal sensations in the three cities during winter. Residents' thermal sensation in Beijing and Hami was negatively correlated with wind speed (Va). Residents in Xi'an and Hami preferred a higher relative humidity (RH). Residents in Beijing and Hami preferred a lower Va to improve OTC related to local climatic characteristics. 2) Xi'an residents had the highest neutral UTCI (NUTCI) (17.3 °C), followed by Beijing (17.0 °C) and Hami (6.4 °C). Xi'an residents had slightly wider neutral UTCI range (NUTCIR) (7.9–26.7 °C) compared to Beijing (8.7–25.4 °C), while Hami residents had the narrowest NUTCIR (1.5–11.3 °C). The “no thermal stress” range in the three cities was 6.1–26.0 °C in Beijing, 6.7–25.5 °C in Xi'an, and −2.2–12.2 °C in Hami. 3) Calibrated thermal indices, based on the ASHRAE 7–point scale, were gained to judge the thermal qualities of an environment for all three cities.
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•A comparative study on OTC in China's cold regions was conducted.•Ta and Tg were the primary factors affecting human thermal sensation during winter.•NUTCI: Xi'an > Beijing > Hami. NUTCIR: 7.9–26.7 °C (Xi'an), 8.7–25.4 °C (Beijing), 1.5–11.3 °C (Hami).•The “no thermal stress” ranges were 6.1–26.0 °C (Beijing), 6.7–25.5 °C (Xi'an) and −2.2–12.2 °C (Hami).•Calibrated thermal indices were gained to predict thermal comfort in the three cities.
The extreme thermal environment driven by climate change disrupts thermoregulation in pregnant women and may threaten the survival of the developing fetus.
To investigate the acute effect of maternal ...exposure to thermophysiological stress (measured with Universal Thermal Climate Index, UTCI) on the risk of stillbirth and modification of this effect by sociodemographic disparities.
We conducted a space-time-stratified case-crossover analysis of daily UTCI and 2835 singleton stillbirths between 1st January 2000 and 31st December 2015 across multiple small areas in Western Australia. Distributed lag non-linear models were combined with conditional quasi-Poisson regression to investigate the effects of the UTCI exposure from the preceding 6 days to the day of stillbirth. We also explored effect modification by fetal and maternal sociodemographic factors.
The median UTCI was 13.9 °C (representing no thermal stress) while the 1st and 99th percentiles were 0.7 °C (slight cold stress) and 31.7 °C (moderate heat stress), respectively. Relative to median UTCI, we found positive associations between acute maternal cold and heat stresses and higher risks of stillbirth, increasing with the intensity and duration of the thermal stress episodes. The cumulative risk from the preceding 6 days to the day of stillbirth was stronger in the 99th percentile (RR = 1.19, 95% CI: 1.17, 1.21) than the 1st percentile (RR = 1.14, 95% CI: 1.12, 1.15), relative to the median UTCI. The risks were disproportionately higher in term and male stillborn fetuses, smoking, unmarried, ≤19 years old, non-Caucasian, and low socioeconomic status mothers.
Acute maternal exposure to both cold and heat stresses may contribute to the risk of stillbirth and be exacerbated by sociodemographic disparities. The findings suggest public health attention, especially for the identified higher-risk groups. Future studies should consider the use of a human thermophysiological index, rather than surrogates such as ambient temperature.
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•We conducted a space-time-stratified case-crossover analysis.•Stillbirth risk increased with the intensity and duration of thermal stress episodes.•Both acute cold and heat stresses positively associated with stillbirth.•The risk of stillbirth was stronger with heat than cold stress.•Stillbirth risk varied substantially by fetal and maternal sociodemographic factors.
This study aims to identify outdoor thermal benchmarks of shaded spaces in an urban park in Xi'an (China). Meteorological measurements were conducted during winter and summer accompanied by a ...subjective thermal sensation questionnaire. The Universal Thermal Climate Index (UTCI) was applied to quantitatively analyze the thermal comfort range in Xi'an, and then variations in outdoor thermal benchmarks between Xi'an and other climatic zones were compared. Results demonstrated that: (1) Air temperature and globe temperature were the dominant physical factors affecting outdoor thermal comfort (OTC) in Xi'an. (2) Pavilion shade effectively lowered thermal stress, decreasing UTCI by 15.5 and 10.1 °C during winter and summer. (3) Deciduous tree shade was the optimal shading design measure and could meet demands for thermally comfortable environments. (4) The neutral UTCI in Xi'an was found to be 23.1 °C, and the acceptable UTCI ranged from 18.0 to 29.1 °C, and (5) a thermal comfort calendar for shaded spaces demonstrated that “strong cold stress” or higher occurred after 16:00h in winter. Pavilion and deciduous tree shades were “neutral thermal stress” for 24h in summer. The results identify thermal benchmarks that could help urban designers create thermally comfortable outdoor spaces in urban parks within the cold region of China.
•Thermal comfort conditions of shaded spaces in Xi'an, China were investigated.•Ta and Tg were the dominant physical factors affecting OTC in Xi'an.•UTCI satisfactorily predicted OTC with neutral value of 23.1 °C.•The range of acceptable neutral UTCI stretched from 18.0 °C to 29.1 °C.•A thermal comfort calendar was proposed for leisure and recreational activities.
Changes of thermal environment can lead to unfavorable impacts such as a decrease of thermal stratification, increase of energy consumption, and increase of thermal health risk. Investigating changes ...in outdoor thermal environments can provide meaningful information for addressing economic and social issues and related challenges. In this study, thermal environment changes in South Korea were investigated using a nonstationary two-component Gaussian mixture model (NSGMM) for air temperature and two thermal comfort indices. For this, the perceived temperature (PT) and universal thermal climate index (UTCI) were employed as the thermal comfort index. Thermal comfort indices were computed using observed meteorological data at 26 weather stations for 37 years in South Korea. Meanwhile, trends of thermal comforts in the warm and cool seasons were simultaneously modeled by the NSGMM. The results indicate significant increasing trends in thermal comfort indices for South Korea. The increasing trends in thermal comfort indices both the warm and cool seasons were detected while the magnitudes of the trends are significantly different. This difference between the magnitude of trends led to an increase in mean and inter-annual variability of thermal comfort indices based on PT, while an increase of mean and decrease of inter-annual variability were observed based on the UTCI. Moreover, the annual proportion of the category referring to days in comfort based on the results of PT has decreased due to the different trends of thermal comfort indices in the warm and cool seasons. This decrease may lead to an increase of thermal health risk that is larger than what would be expected from the results considering the increasing trend of the annual mean temperature in South Korea. From this result, it can be inferred that the thermal health risk in South Korea may be more adverse than what we originally expected from the current temperature trend.
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•Trends of thermal comforts in warm and cool seasons were simultaneously modeled.•Mean trends of thermal comfort index have increased in South Korea.•Different trends of cool and warm seasons increase variability of thermal comfort.•Increase trend in heat stress and decrease in no and cold stresses are observed.•Future thermal health risk may be more adverse than that assuming mean change.
The optimized design of outdoor environment is of utmost importance due to its impact on human health, urban livability and energy consumption inside buildings. The outdoor thermal comfort and its ...spatiotemporal variations were assessed using Universal Thermal Climate Index (UTCI). Annual and seasonal UTCI were calculated using the daily dataset collected from 591 stations in China between 1966 and 2016. A REOF-cluster-EOF hybrid model was developed to optimize regionalization and assess regional-scale variations for UTCI. The results showed the following: (1) UTCI values decreased due to the increase of the latitude in China except for the Qinghai-Tibet Plateau. 69.5% of the total area of China experienced “no thermal stress” conditions in summer, whereas it was only 7.7% in winter. Additionally, the outdoor environment in summer had a wider “thermal comfort zone” than that in other seasons. (2) China was divided into a small number of regions with coherent UTCI changes using REOF analysis and K-means clustering algorithm. Eight homogeneous regions were obtained for annual UTCI. From spring to winter, the numbers of homogeneous regions were eight, nine, ten and seven, respectively. (3) Using EOF analysis, dominant patterns of UTCI in each region were extracted by the first two EOF modes, which accounted for >60% of the total variance. In the first mode, the significant upward trends of UTCI were detected in each region, suggesting the stronger outdoor heat stress. In the second mode, UTCI showed fluctuation between the cold and warm periods with different turning points between regions. Overall, the outdoor thermal comfort seemed to be improved more in high-latitude regions than that in low-latitude regions.
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•A REOF-cluster-EOF hybrid model was proposed to examine regional-scale variations.•The thermal comfort zone was the largest in summer and the smallest in winter.•Annual and seasonal UTCI exhibited the significant warming trend in each region.•UTCI fluctuated between cold and warm periods with different turning points.•The outdoor thermal comfort seemed to be improved more in high-latitude regions.
The aim of this research is to propose a novel methodology that exploits Earth Observation (EO) data to accurately produce high-resolution bioclimatic maps at large spatiotemporal scales. This method ...directly links EO products (i.e., land surface temperature - LST and Normalized Difference Vegetation Index - NDVI) to air temperature (Tair) and such thermal indices as the Universal Thermal Climate Index (UTCI), and the Physiologically Equivalent Temperature (PET) to produce large-scale high-quality bioclimatic maps at a spatial resolution of 100 m. The proposed methodology is based on Artificial Neural Networks (ANNs), and the bioclimatic maps are developed with the use of Geographical Information Systems. High-resolution LST maps are produced from the spatial downscaling of EO images and the application of the methodology in the case of the island of Cyprus highlights the ability of EO parameters to estimate accurately Tair as well as the above mentioned thermal indices. The results are validated for different conditions and the overall Mean Absolute Error for each case ranges from 1.9 °C for Tair to 2.8 °C for PET and UTCI. The trained ANNs could be used in near real-time for estimating the spatial distribution of outdoor thermal conditions and for assessing the relationship between human health and the outdoor thermal environment. On the basis of the developed bioclimatic maps, high-risk areas were identified. Furthermore, the study examines the relationship between land cover and Tair, UTCI, and PET, and the results provide evidence of the suitability of the method to monitor the dynamics of the urban environment and the effectiveness of urban nature-based solutions. Studies on bioclimate analysis monitor thermal environment, raise awareness and enhance the capacity of national public health systems to respond to thermally-induced health risks.
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•Novel Earth Observation methodology for producing high-resolution bioclimatic maps•Neural networks can be used in real time for estimating outdoor thermal conditions.•Earth observation data are used for estimating air temperature, UTCI, and PET.•High thermal risk areas are identified in the bioclimatic maps.
We investigate the heat stress mitigation potential of greening strategies in Prague using a configuration of the PALM-4U model that has been rigorously evaluated with measurements. Three greening ...scenarios were evaluated using the Universal Thermal Climate Index (UTCI). The UTCI reduction effect of broad-leaf or coniferous trees in a complex urban environment was found to be strongly local, with minor domain-average UTCI reductions; −4.1K under tree crowns and −0.6K on average in the neighbourhood as a day-time average, peaking at about twice these values near midday. During daytime the UTCI reduction potential of trees increases with the intensity and duration of solar exposure; −15.1K is the spatial maximum across all scenarios. For trees fully shaded by buildings, UTCI reduction was low (−0.5K as maximum). Tree planting reduces air temperature by more than 5K in some locations under trees, and reduces neighbourhood-average air temperature by up to 0.3K, with cooling peaking in the early evening about 8 h after the corresponding peak in UTCI reduction. Results emphasize the highly localized microclimate effects of trees for pedestrian thermal exposure reduction. The combination of green walls and roofs yielded negligible results in terms of UTCI reduction and only small air temperature effects.
•UTCI reduction effect of broad-leaf or coniferous trees was −4.1K under tree crowns.•In the neighbourhood was day-time average UTCI reduction effect −0.6K•Trees fully shaded by buildings reduce UTCI about −0.5K as maximum.•Microclimate effects of trees for thermal exposure reduction are highly localized.•The combination of green walls and roofs yielded negligible results of UTCI reduction.
The assessment of the impact of meteorological factors on the epidemiology of various diseases and on human pathophysiology and physiology requires a comprehensive approach and new tools independent ...of currently occurring climate change. The thermal comfort index, i.e., Universal Climate Thermal Index (UTCI), is gaining more and more recognition from researchers interested in such assessments. This index facilitates the evaluation of the impact of cold stress and heat stress on the human organism and the assessment of the incidence of weather-related diseases. This work aims at identifying those areas of medical science for which the UTCI was applied for scientific research as well as its popularization among clinicians, epidemiologists, and specialists in public health management. This is a systematic review of literature found in Pubmed, Sciencedirect and Web of Science databases from which, consistent with PRISMA guidelines, original papers employing the UTCI in studies related to health, physiological parameters, and epidemiologic applications were extracted.
Out of the total number of 367 papers identified in the databases, 33 original works were included in the analysis. The selected publications were analyzed in terms of determining the areas of medical science in which the UTCI was applied. The majority of studies were devoted to the broadly understood mortality, cardiac events, and emergency medicine. A significant disproportion between publications discussing heat stress and those utilizing the UTCI for its assessment was revealed.
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•Climate change requires searching for universal methods and tools to monitor relationships between humans and climate.•The UTCI is a universal tool describing the impact of thermal stress on the human body.•The review shows the usefulness of UTCI in medical research.
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