Physiologically Equivalent Temperature Values Research Articles

The predicted effectiveness of thermal condition mitigation strategies for a climate-resilient archaeological park

The study aims to predict the effectiveness of three mitigation strategies in improving the thermal comfort of the visitor area at the Prambanan Temple Tourism Park formulated in the previous research, namely: cooling effects of a park surrounding the visitor area, cool transparent coating on the temple stones, and the placement of potted tree clusters (green parasols) based on strolling comfort distance. This study used validated ENVI-met microclimate models to predict the effectiveness measured by reducing the mean Physiologically Equivalent Temperature (PET) value in the visitor area on the hottest day and during hottest hours caused by the implementation of each strategy. The simulation results show the role of shading created by green parasols in decreasing the PET value in the visitor area, i.e. 2.53 °C. Meanwhile, The PET values decrease by 1.75 °C due to the cool transparent coating and only by 0.23 °C due to the park surrounding the visitor area. The most significant reduction in the PET value by the park with 5 m high trees and a sparse grid layout compared to 10 park variants is found more related to the layout density.

Factors influencing resident and tourist outdoor thermal comfort: A comparative study in China's cold region

Thermal comfort and environmental health in scenic open spaces, a communication bridge between tourists and their environment, are prerequisites for tourism activities. In this study, scenic open spaces in an urban area of Xi'an, China were selected. Thermal perception (thermal sensation, comfort and acceptability) of residents and tourists were investigated through meteorological measurement and questionnaire survey. Physiological equivalent temperature (PET) was used to determine thermal benchmarks of all visitors to the site. Variables that influence individual thermal perception assessment (physical, individual, society and psychology) were measured and compared. Finally, a series of strategies and suggestions were proposed based on meteorological characteristics and influencing factors of thermal perception from perspectives of designers and scenic spot managers. Results show that: 1) Neutral PET (NPET) of respondents were 17.3 °C (residents) and 15.5 °C (tourists). Neutral PET ranges (NPETR) were 8.9–25.8 °C (residents) and 7.2–23.8 °C (tourists). Preferred PET values were 20.1 °C (residents) and 19.7 °C (tourists). Thermal acceptability ranges (TAR) were 6.3–37.8 °C (residents) and 0.5–39.9 °C (tourists). 2) In winter, physical factors were primary influencers of residents' thermal perception, followed by social factors, while tourists' thermal perception was mainly influenced by physical factors. In spring, physical factors were still the primary influencers for residents, followed by individual factors. Physical factors were also dominant for tourists, followed by psychological. In summer, physical factors were the major influencing factors for residents and tourists' thermal perceptions.

Thermal comfort analysis through development of artificial neural network models: An experimental study in Cwa climate

This work presents the development of artificial neural network (ANN) models to predict outdoor thermal comfort using the Physiological Equivalent Temperature (PET) index for a college campus in Cwa climate (dry winter humid subtropical climate as per Köppen Climate Classification). Thermal modeling of the study area is exercised using ENVI-met. Twelve different ANN models were developed and tested to evaluate the effectiveness of ANN in predicting the thermal comfort index for the summer and winter months. Two network models were developed using all major meteorological variables. Ten network models were developed using only air temperature, relative humidity, solar radiation, mean radiant temperature, and wind speed respectively. ANN models with all major meteorological variables proved to be effective in estimating close PET values for both summer (R2 = 0.99) and winter (R2 = 0.99). For cases when only one variable is available, network models featuring only air temperature proved effective for both summer (R2 = 0.93) and winter (R2 = 0.92).

Physiological Equivalent Temperature (PET) index and cardiovascular hospital admissions in Ahvaz, southwest of Iran

Evidence shows that climate change may have adverse effects on human health. The purpose of this study was to investigate the relation between Physiologically Equivalent Temperature (PET) and cardiovascular hospital admissions in Ahvaz. Distributed Lag Non-linear Models (DLNM) combined with quasi-Poisson regression models were used to investigate the effect of PET on hospital admissions. Low PET values (6.4 °C, 9.9 °C and 16.9 °C) in all lags, except lag 0-30, significantly decreased the risk of hospital admissions for total cardiovascular diseases, hypertension, ischemic heart diseases, and cardiovascular admissions in men, women and ≤65 years. But, low PET (6.4 °C) in lags 0 and 0-2 significantly increased the risk of hospital admissions for cerebrovascular diseases; and high PET values increased the risk of ischemic heart diseases and in men. Both cold and hot stress are involved in cardiovascular hospital admissions.

Assessing the influence of street configurations on human thermal conditions in open balconies in the Mediterranean climate

Heat stress in the built environment has become a serious health and comfort issue, given the increases in Urban Heat Island effects, and augmenting impacts associated to climate change. This study deals with the potential correlations between human thermal conditions, the encircling microclimate, and the physical structure of the city. Through long-term numerical simulations, the disclosed study analyses the influence of the urban street configurations on the thermal bioclimate within urban canyons, specifically upon open balconies in the most populated district of Barcelona: The Eixample. The simulated thermal conditions were carried out in the human biometeorological RayMan Pro model using local climatic data, to determine the Physiologically Equivalent Temperature (PET) within four generated scenarios, with similar morphological properties of the Eixample district.The findings reveal that streets with axes oriented NS and SE-NW provide the best thermal conditions for balconies, achieving acceptable PET values (18 °C < PET <29 °C) on both façades. On the other hand, EW streets presented high thermal stress conditions (over 43,4% of the time) for those balconies located in the north side of the canyon. Open balconies at heights below 12 metres are the most comfortable ones during summer daytime, with acceptable thermal conditions that range between 50,4% and 82,5% of the time. The highest frequencies of acceptable thermal conditions were found on balconies located at 6 metres and 9 metres high on the east, south and southeast façades of the NS, EW and NE-SW oriented streets respectively (from 77% to 83% of the time). These configurations provide the most suitable thermal conditions during the studied summer periods by having frequencies of heat stress below 20%.Our results and recommendations contribute to bridge the gap between human biometeorology, public health, and architectural and urban planning. Some areas of its direct application are the use of balconies in periods of confinement; decision-making on the sale or rental of apartments; and the promotion of bioclimatic retrofit projects at an urban and architectural scale supported by local governments.

Physiological equivalent temperature (PET) and non-accidental, cardiovascular and respiratory disease mortality in Ahvaz, Iran.

Climate change may be associated with human morbidity and mortality through direct and indirect effects. Ahvaz is one of the hottest cities in the world. The aim of this study was to investigate the relation between physiological Equivalent Temperature (PET) and non-accidental, cardiovascular and respiratory disease mortality in Ahvaz, Iran. Distributed Lag Non-linear Models (DLNM) combined with quasi-Poisson regression were used to investigate the effect of PET on death. The effect of time trend, air pollutants (NO2, SO2 and PM10), and weekdays were adjusted.The results showed that in cold stress [1st percentile of PET (2.7°C) relative to 25th percentile (11.9°C)] the risk of total respiratory mortality, respiratory mortality in men, and mortality in people under 65year olds, significantly decreased in the cumulative lags of 0-2, 0-6 and 0-13; but the risk of respiratory mortality increased in the elderly and in the final lags. In contrast, heat stress [99th percentile of PET (44.9°C) relative to 75th percentile (43.4°C)] significantly increased the risk of total cardiovascular mortality (CVD), cardiovascular mortality in men, ischemic heart disease and cerebrovascular disease mortality in lags 0 and 0-2. It seems that high PET values increase the risk of cardiovascular mortality, while low PET values increase respiratory mortality only among the elderly in Ahvaz.

Human Thermal Comfort Conditions during Heat Wave Events in Kyiv, Ukraine

Assessment of the big cities bioclimate during heat wave (HW) events is a highly topical issue and a focus point for many researchers. Reliable results of the assessment of heat stress (HS) intensity during HWs form the basis for the development and implementation of heat adaptation measures. In Ukraine, first HW studies started only a few years ago, and the thermal comfort conditions during these atmospheric phenomena have not been explored yet. The purpose of this article is to assess characteristic features of thermal bioclimate in Kyiv during heat wave events. The assessment is based on the thermal index – physiologically equivalent temperature (PET). The RayMan model was used to simulate PET values. As shown in the study, during the period of 1961–2020, 24 heat wave events were observed in Kyiv. Those HWs were characterized by different duration (from 6 to 18 days) and intensity (with the maximum value of cumulative Ta,MAX 108.6°C). Thermal comfort conditions registered during heat waves were characterized by heat stress varying from slight (23.7°C) to extreme (47.0°C). To assess the impact of HWs on the human, a classification based on mean PET values during a single heat wave and its duration was proposed. According to this classification, heat waves belong to three following grades: HWs with moderate, strong, and extreme HS. Analysis of HW events in Kyiv for the research period demonstrates four (4) heat waves with moderate heat stress, nineteen (19) with strong stress, and one (1) with extreme stress (specifically, the heat wave in late July–first half of August 2010). The daily PET values at 12 UTC during this HW varied from 37°C to 47°C and were much higher than mean PET values for these days during 2005 and 2014.

Assessing local heat stress and air quality with the use of remote sensing and pedestrian perception in urban microclimate simulations

Cities are increasingly confronted with multiple environmental and climatic stressors. Especially during heatwaves, street canyons are both producers and sufferers of air pollution and urban heat island (UHI) effects, with severe risks on public health. To better design mitigation measures, it is important to consider both the microclimate behaviors as well as the perceptions of the local population. Therefore, this study examined pedestrian perceptions and microclimate modelings to understand outdoor thermal comfort conditions and air pollution dispersion in the case study neighborhood of Dortmund Marten, Germany. A field survey with measurement points at two street canyons for climatic variables and questionnaires on subjective thermal comfort and air pollution was conducted on a hot day during the heatwave period in August 2020. As a cost-effective method for modeling input generation, we extracted spatial and spectral data like albedo, roof materials and tree locations out of remote sensing imageries. Finally, we compared the modeling results of the physiological equivalent temperature (PET) index, particulate matter concentrations and air temperatures with empirical field measurement data and the questionnaire responses. Results indicate that during hot summer days with light winds from the east, the north-south orientated street canyon with tree arrangements tends to act as a tunnel for particulate matter accumulation. Coincidently, pedestrians show less thermal discomfort than calculated PET values in that particular area during morning and daytime, which underlines the dichotomy of such places. On the other hand, the low rise east-west orientated street canyon shows higher PET votes than predicted by the model. However, particulate matter concentrations were considerably underestimated by the model, while air temperature predictions provided meaningful results. The proposed workflow shows the potential to accelerate future preparations of input data for microclimate modelings, while the results can enhance wind-sensitive planning procedures and heat stress resilience in mid-latitude urban neighborhoods.

The Street Walkability and Thermal Comfort Index (SWTCI): A new assessment tool combining street design measurements and thermal comfort

In recent years, walkability is increasingly integrated into sustainability strategies, considering its many health and environmental benefits. Besides, thermal comfort also has been progressively promoted as a critical measure for pedestrian comfort and wellbeing. Despite the relevance of the two concepts, few studies combined them in a comprehensive model. This study considers thermal comfort in assessing walkability by developing a new measurement tool, the Street Walkability and Thermal Comfort Index (SWTCI), which focuses on comfort facilities and Physiological Equivalent Temperature (PET), at the street scale. The applied point system method requires combining a questionnaire survey, observations, and in situ measurements (air temperature, wind velocity, and relative humidity). The questionnaire survey (330 responders) measured 21 street design indicators' importance, using a five-point Likert scale ranging from 1 (least important) to 5 (very important). The observation technique seeks to evaluate every pedestrian comfort indicator score (Sis). The in situ measurements permit Envi-met's calibrated data validation and getting the mean radian temperature (Tmrt). Those were considered in the PET's calculation using Rayman software. Three distinct streets have been chosen in Annaba city, Algeria, within the Mediterranean climate (Csa). The results show that the SWTCI achieves its highest score on the three streets when the thermal perception is neutral (20 < PET <26), and its lowest score, with a warm thermal sensation (28 < PET < 31). Despite the divergence in PET values, the highest score of SWTCI was 33%, reflecting a low comfort quality and minimal pedestrian facilities. Applying the SWTCI method can transform uncomfortable streets into an ideal walkable and pleasant path by finding the problems and proposing improvements.

Engineered bioclimatic responses in ancient settlements: a case study.

The Mandya district of Karnataka, India, houses a unique Jain settlement constructed about 1000 years ago. Recent excavations by the Archaeological Survey of India (ASI) indicate a high degree of engineering skills among the builders of this settlement. Adapting to heat-stresses in a region where the Monsoons often failed was and is still a matter of concern. Ingenious methods were adopted to modulate bioclimatic responses to maintain thermal comfort indices. The Aretippurians used composite building fabrics which modulated heat transfer to the interiors. Indeed, the thermal transmittances for these composite fabrics were low to moderate for both the temple complexes as well as the dormitories; these were 0.27 Wm-1K-1 and 0.23 Wm-1K-1, respectively. A site visit revealed that a unique and engineered micro-climate was also made to prevail on this hilltop settlement housing several hundred Jain settlers. A granite skirted reservoir was indeed the pièce-de-résistance promoting hydraulic air-conditioning for eight months of the year around the premises with copious winds blowing over a large and exposed rain-fed reservoir. This fanned chilled air across the open plan temples, courtyards, and lived-in areas. This paper explores bioclimatic responses for around 120 residents to the prevailing indoor settings modulated by an engineered microclimate. This was possible because of the staggered layout, unique building forms, use of mixed building fabric, and carefully chosen glazing ratios which yielded salubrious settings. Clearly, this entailed a complex interplay between the intercepted solar insolation, structure-driven turbulence, and the transfer of heat across the original composite walls within and around the complex, requiring a systematic experimental as well as modelling study. The experimental part of the project involved the calculation of the thermal transmittivity across the walls made up of fired bricks, granite, and limestone, and the theoretical part involved the use of appropriate software to reconstruct air flow and heat distribution across floors, walls, and ceilings to proxy the original flow pattern yielding the comfortable PMV (predicted mean vote) and PET (physiological equivalent temperature) values within these premises. This exercise may well lead to further explorations on indoor comfort adaptations in tropical settings with the use of many edifying vernacular idioms in ancient settlements which prevail even in modern layouts.

Physiological equivalent temperature (PET) index and respiratory hospital admissions in Ahvaz, southwest of Iran.

Although Ahvaz is considered as one of the warmest cities around the world, few epidemiological studies have been conducted on the adverse effects of temperature on human health using thermal indices in this city. This study investigates the relation between physiologically equivalent temperature (PET) and respiratory hospital admissions in Ahvaz. Distributed lag non-linear models (DLNMs) combined with quasi-Poisson regression models were used to investigate the relation between PET and respiratory disease hospital admissions, adjusted for the effect of time trend, air pollutants (NO2, SO2, and PM10), and weekdays. The analysis was performed by utilizing R software. Low PET values significantly decreased the risk of hospital admissions for total respiratory diseases, respiratory diseases in men and women, chronic obstructive pulmonary diseases (COPD), and bronchiectasis. However, low PET (16.9°C) in all lags except lag 0-30 significantly increased the risk of hospital admissions for asthma. The results indicate that in Ahvaz, which has a warm climate, cold weather decreased overall respiratory hospital admissions, except for asthma.

A regression-based three-phase approach to assess outdoor thermal comfort in informal micro-entrepreneurial settings in tropical Mumbai.

Urban heat poses a public health risk to the residents of megacities in developing countries because the population spends a significant amount of time outdoors to work and socialize with limited cooling resources. Understanding the drivers of outdoor comfort and heat stress in informal work settings is important to design climate-sensitive outdoor spaces and reduce heat vulnerability. We present outdoor thermal comfort perceptions (OTCPs) of people engaged in outdoor micro entrepreneurial activities in Mumbai using seasonal surveys and biometeorological observations. We propose a three-phase approach to analyze the relative importance of climatic and non-climatic variables for OTCPs. The first phase evaluates the seasonal and intra-neighborhood variation of thermal sensation votes (TSV) with respect to physiological equivalent temperature (PET) and air temperature. Second, we include physiological parameters to evaluate the seasonal and intra-neighborhood variation of overall sensation votes (OSV). Third, we consider aggregated survey responses and include behavioral and perceptual variables to determine their relative significance. We employ three linear modeling techniques to assess model performance in explaining the variability of OTCP using OSV as dependent variable. Results reveal that microclimatic parameters alone are unable to explain the variability of OTCP. Our results yield a neutral PET value (PETneutral) of 23.75 °C for Mumbai in the winter. PETneutral was higher for activities at the clothing market compared to other micro entrepreneurial activities. Acclimatization significantly improved comfort in the summer, while evaporative cooling was beneficial in the winter. Further, an ANCOVA and ordinal logistic regressions demonstrate the importance of behavioral attributes (presence in the location, expectation, beverage intake) in explaining the variance in OTCP. Our study also reveals that wind speed and humidity play an important role in shaping overall comfort in the Mumbai neighborhoods.

Study of the relationship between the spatial structure and thermal comfort of a pure forest with four distinct seasons at the microscale level

The local thermal environment of forest green space has a great influence on users' experience and health. Thus, it is of great value to systematically study the relationship between forest spatial structure and thermal comfort at the microscale. This study examined the relationship between the spatial structure and thermal comfort of bamboo forest using a case study of "Zhu Hai Dong Tian" Park in Dujiangyan city, Sichuan Province, China. We selected 20 in-forest study sites and three out-of-forest control sites and measured 13 spatial structure parameters and five climatic parameters (air temperature, relative humidity, wind velocity, surface temperature and global radiation) at the 23 sites for three representative days in each season. Then, the five climate parameters, human body parameters (sex, age, height, weight, clothing, and activity), and sky view factor (SVF) were input into Rayman software to calculate the physiological equivalent temperature (PET) value of each site in each season. PET is the physiological temperature value of the equivalent thermal environment based on energy balance. In this study, PET values between 15 and 22 °C indicated that the thermal environment was comfortable. The results showed that the PET values of the 20 study sites in the bamboo forest were mostly at a comfortable level in spring and autumn but had various degrees of heat stress and cold stress in summer and winter, respectively. The relationship between microstructure parameters and PET in four seasons was expressed by four models. In the spring and summer models, CPR (cover plant ratio) and CDW (canopy diameter width) were positively correlated with PET and had the greatest influence. In the autumn and winter models, DFS (degree of facing the sun's trajectory vertically) and CPR were positively correlated with PET and had the greatest influence. In addition, DBH (diameter at breast height), DB (density of bamboo forest), S (slope), CPH (cover plant height), ST (slope of the trunk), SP (spacing), H (height of the space), and IL (internodal length) were included in the models of all four seasons. The research results provide useful information for improving the thermal comfort of microscale pure forest space by modifying the forest structure. The results can be used to guide forest management to further create forest space that integrates climate comfort, landscape, and service.

Analysis of outdoor thermal comfort and air pollution under the ınfluence of urban morphology in cold-climate cities: Erzurum/Turkey.

The increase in population in urban areas has increased the demand for housing. In cities that could not adapt to the population increase, the attempt to fit more houses in a unit area has emerged. This situation caused the application of created designs ignoring the natural and microclimate data of the cities. Since Erzurum is located on the high plain surrounded by mountains, it is one of the coldest cities in Turkey with its long-term annual mean temperature of 5.7 °C. The aim of this research is to reveal the effects of the urban morphology on thermal comfort and its relationship with air pollution in Erzurum. Steps of the research methodology can be summarized as determination of measurement areas, physiologically equivalent temperature (PET) analysis, air pollution analysis, and mapping. The city center is located at an altitude of 1850 m from the sea level, and the open rural area has the lowest altitude of 1650 m from the sea level with respect to the surrounding mountainous terrain. The microclimate data of the meteorological stations in the three study areas and government monitoring station and air pollution data have been recorded hourly in 2018. The recorded data was analyzed with the RayMan pro 2.1 model, which is a widely used simple index PET for obtaining outdoor thermal comfort. According to the research results, the highest PET value of Erzurum was obtained in the city center as 11.4 °C and then the urban transformation district as 6.3 °C, and the lowest PET was obtained from the open rural area as 4.5 °C. In the areas that have low PET values and cold stress issues, it was observed that the air pollution data are low. The city center was detected to have the highest air pollution parameters. It was determined that urban morphology, air pollution, and thermal comfort had significant correlations.

Utilizing thermal comfort and walking facilities to propose a comfort walkability index (CWI) at the neighbourhood level

Many walkability indices have been developed by considering a range of specific indicators. However, comfort indicators at the neighbourhood scale and the effects of thermal comfort have generally not been accounted for in such research. To this end, we propose the comfort walkability index (CWI) at the neighbourhood micro-scale. The proposed tool is based on two questionnaires, 330 respondents answered the first questionnaire, to evaluate the relative coefficient for each indicator (Cis). The second questionnaire based on 282 respondents using a simple random sampling technique to assess the scores of the selected factors (Sis). We tested the CWI in two areas in the city centre of Annaba, Algeria, and calculated the physiological Equivalent temperature (PET) using RayMan software on two average summer days from 7 a.m. to 8 p.m. when heat and humidity peaks are observed. The results show that over 95% of the suggested indicators were estimated as being very important and necessary. The CWI scores were dependent on PET values and thermal perception. The highest scores of CWI were 40.95% and 25.23% in Colonial centre and Old town respectively, correlated with neutral thermal sensation (20°C–26 °C). CWI in the Colonial centre was changing from rarely acceptable comfort quality to uncomfortable level depending on PET scores, however, CWI in Old Town defined a low comfort quality despite the variability of PET scores. This paper highlights the importance of assessing pedestrian comfort facilities at the neighbourhood microscale and heeding the importance of thermal comfort in promoting a satisfying walking experience.

Human-biometeorological assessment of Kharkiv (Ukraine) in the summer season

The objective of this research is to assess the bioclimate of the city of Kharkiv in the summer season using the human thermal index of physiologically equivalent temperature (PET). The RayMan model has been used to obtain PET values. The results suggest that most days in Kharkiv during the summer are characterized by heat stress of various intensity 65.7% in June, 84.6% in July, 77.1% in August. The average frequency of comfortable weather is very low, varying from 12.6 to 25%. During heat waves, the frequency of days in Kharkiv with heat stress increases significantly, amounting to 96.3%. The results of the Kharkiv bioclimate assessment using PET may be used to create measures for heat adaptation and develop infrastructure for recreation and tourism in the city during hot periods.

Approaching environmental human thermophysiological thresholds for the case of Ankara, Turkey

The disclosed study undertook a ‘human centred-approach’ that ascertained and categorised environmental human thermophysiological risk factors by relating them to the human biometeorological system through the use of three widely utilised energy balance model (EBM) indices, the physiologically equivalent temperature (PET), the modified PET, and the universal thermal climate index (UTCI). The disclosed assessment was carried out over the past decade (i.e., 2010–2019) with a 3-h temporal resolution for the case of Ankara through two WMO meteorological stations to compare both local urban and peri-urban environmental conditions. The study recognised extreme annual variability of human physiological stress (PS) during the different seasons as a result of the biometeorological processing of the singular variables, which in the case of average PET for both stations, varied by up to 75 °C between the winter and summer for the same annual dataset (2012). In addition, all EBMs indicated higher heat stress within the city centre that were conducive of both urban extreme heatwaves and very hot days during the summer months, with extreme heat stress levels lasting for longer than a week with PET values reaching a maximum of 48 °C. Similar cold extremes were found for the winter months, with PET values reaching − 30 °C, and average PS levels varying lower in the case of the peri-urban station.Graphical abstract

The physiological equivalent temperature (PET) Index and non-accidental and cardiovascular respiratory disease mortality in Ahvaz, Iran

Background: Climate change may be associated with human morbidity and mortality through direct and indirect effects. Ahvaz is one of the hottest cities in the world. The aim of this study was to investigate the relation between Physiologically Equivalent Temperature (PET) and non-accidental, cardiovascular and respiratory disease mortality in Ahvaz, Iran. Methods: Distributed Lag Non-linear Models (DLNM) combined with quasi-Poisson regression were used to investigate the effect of PET on deaths. In this study the effect of time trend, air pollutants (NO2, SO2 and PM10), and weekdays were adjusted. Results: The results showed that in cold stress (the PET index, 1st percentile (2.7 CO) relative to 25th percentile (11.9 CO)) the risk of non-accidental mortality in men and the 65-74 year olds; and also total respiratory mortality, respiratory mortality in men, in people under 65 and the 65-74 year olds; significantly decreased in the cumulative lags of 0, 0-2, 0-6 and 0-13. In contrast, heat stress (the PET index, 99th percentile (44.9 CO) relative to 75th percentile (43.4 CO)) significantly increased the risk of total cardiovascular mortality (CVD), cardiovascular mortality in men and the elderly, ischemic heart disease and cerebrovascular disease mortality in lags 0 and 0-2. Conclusions: It seems that high PET values increase the risk of cardiovascular mortality, while low PET values have a protective effect on mortality, especially respiratory mortality in Ahvaz.

Physiological Equivalent Temperature (PET) Index and cardiovascular and respiratory hospital admissions in Ahvaz, southwest of Iran

Physiological Equivalent Temperature (PET) Index and cardiovascular and respiratory hospital admissions in Ahvaz, southwest of IranBackground: Evidence has shown that climate change may have adverse effects on human health.Although Ahvaz is one of the hottest cities in the world, there have been no studies on the effect of ambient heat on hospital admission rates.The purpose of this study was to investigate the relation between Physiologically Equivalent Temperature (PET) and cardiovascular and respiratory hospital admissions in Ahvaz.Methods: Distributed Lag Non-linear Models (DLNM) combined with quasi-Poisson regression were used to investigate the effect of PET on hospital admissions. In this study the effect of time trend, air pollutants (NO2, SO2 and PM10), and weekdays were adjusted.Results: The results demonstrated that low PET values (6.4°C, 9.9°C and 16.9°C) in lags 0, 0-2, 0-6, 0-13 and 0-20,significantly decreasedthe risk ofhospital admissionsfortotalcardiovascular diseases,hypertension, ischemic heart diseases, cardiovascular admissionsin men, women and less than 65 year olds. Also, low PET values significantly decreased the riskof hospital admissions for total respiratory diseases, respiratory diseases in men and women, chronic obstructive pulmonary disease (COPD) and bronchiectasis. In contrast, low PET values in all lags except lag 0-30significantlyincreased the risk of hospital admissionsforasthma and strokes. High PET values (43.6°C and 45.4°C) increased the risk of cardiovascular and ischemic heart diseases in men.Conclusions: The results indicate that in Ahvaz which has a warm climate, cold stressesare more involved in cardiovascular and respiratory hospital admissions; and cold stress decreased overall cardiovascular and respiratory hospital admissions, except for asthma and stroke.

Comparing impact of multi-factor planning layouts in residential areas on summer thermal comfort based on orthogonal design of experiments (ODOE)

The previous studies of outdoor thermal comfort mainly focused on the micro-climate changes caused by urban morphological factors such as street aspect ratio, plot ratio, sky view factor (SVF) et al. As an essential routine to mitigate urban heat island (UHI), vegetation was also discussed by researchers to explore the optimal distribution. However, under the same determined quantity, there is still a blank of the study in how significant each layout factor is to thermal comfort, including the building layout, the pavement layout, and the vegetation layout. This paper followed an orthogonal design of experiment (ODEO) to create various multi-factor layouts in the case of northern China, thoroughly analyzing simulated results based on Physiological Equivalent Temperature (PET) to explain the internal mechanism. Results show that in high-rise residential areas, the layout significance ranking affecting thermal comfort in summer is: buildings, vegetation, pavement. The optimal arrangement is a layout combination of the scattered-form buildings, the grid-form pavement, and the southern vegetation, which can reduce PET of 6.3% maximally during the day. We also found that wind maps are highly consistent with PET maps due to its heat dissipation capability. Another reason for the high PET value is the solar radiation trapping effect, which should be considered with building shade when discussing the relationship between multi-layouts and thermal comfort. The arrangement method can provide a new research direction of urban micro-climate in the future and thus can be employed by decision-makers in the early planning stage.