A review of mitigating strategies to improve the thermal environment and thermal comfort in urban outdoor spaces

Effects of microclimate on disease prevalence across an urbanization gradient

Increased temperatures associated with urbanization (the "urban heat island" effect) have been shown to impact a wide range of traits across diverse taxa. At the same time, climatic conditions vary at fine spatial scales within habitats due to factors including shade from shrubs, trees, and built structures. Patches of shade may function as microclimate refugia that allow species to occur in habitats where high temperatures and/or exposure to ultraviolet radiation would otherwise be prohibitive. However, the importance of shaded microhabitats for interactions between species across urbanized landscapes remains poorly understood. Weedy plants and their foliar pathogens are a tractable system for studying how multiple scales of climatic variation influence infection prevalence. Powdery mildew pathogens are particularly well suited to this work, as these fungi can be visibly diagnosed on leaf surfaces. We studied the effects of shaded microclimates on rates of powdery mildew infection on Plantago host species in (1) "pandemic pivot" surveys in which undergraduate students recorded shade and infection status of thousands of plants along road verges in urban and suburban residential neighborhoods, (2) monthly surveys of plant populations in 22 parks along an urbanization gradient, and (3) a manipulative field experiment directly testing the effects of shade on the growth and transmission of powdery mildew. Together, our field survey results show strong positive effects of shade on mildew infection in wild Plantago populations across urban, suburban, and rural habitats. Our experiment suggests that this relationship is causal, where microclimate conditions associated with shade promote pathogen growth. Overall, infection prevalence increased with urbanization despite a negative association between urbanization and tree cover at the landscape scale. These findings highlight the importance of taking microclimate heterogeneity into account when establishing links between macroclimate or land use context and prevalence of disease.

Analysis of the correlation mechanism between geometric parameters and the thermal environment of Xi'an's summer outdoor commercial pedestrian streets

Intensive urban development has resulted in the degradation of the urban thermal environment in most regions. There is a growing consensus on the need to enhance urban thermal comfort through well-designed forms, especially in open spaces like urban canyons. To address this, our study focuses on Xi'an's commercial pedestrian streets, employing K-means clustering analysis to create 32 representative models based on actual scenes, capturing their textural characteristics. Simultaneously, 11 geometric indicators (2D/3D) were chosen to quantify the canyon's geometric form. We assessed the spatial and temporal distribution differences in the thermal environment across these models using Envi-met simulation. Finally, Spearman correlation analysis was employed to examine the correlation and significance of the two sets of indicators, culminating in formulating an ideal model. The findings reveal that (1) wind conditions are predominantly influenced by the canyon's geometric form, followed by solar radiation and temperature, with the lowest relative humidity change amplitude among the assessed thermal parameters. (2) Among the 11 geometric form indicators, 3D indicators correlate more significantly with thermal environment parameters than 2D indicators. Specifically, street orientation significantly impacts the thermal environment, Build-To-Line Rat holds greater significance than interface density, and both building shape coefficient and block surface ratio are significantly correlated with air temperature and wind speed, with a weaker correlation to solar radiation. (3) In the Xi'an region, courtyards oriented north-south demonstrate a more favorable trend in the thermal environment.

Effects of thermal and acoustic environments on human comfort in urban and suburban campuses in the cold region of China

In this study, we investigated the effects of thermal-acoustic environments on human comfort in a cold region by focusing on Xi'an in China as a representative city. Four typical open spaces were identified within two universities, with one located in an urban area and the other in a suburban area. Surveys were conducted using questionnaires and environmental parameters were measured to assess thermal-acoustic perception. The physiological equivalent temperature (PET) and noise sound pressure levels were employed to measure the thermal-acoustic environments in the four open spaces. The results showed that the neutral PET was 19.1 °C in Xi'an from March to May, and the neutral temperature range was 14.9-23.4 °C. The preferred temperature was 20.0 °C. Acoustic sensation votes were lower in suburban areas than urban areas. Respondents in urban areas exhibited significantly higher sensitivity to the thermal and acoustic environments compared with those in suburban areas. Sensitivity to the thermal environment decreased as the environmental noise levels decreased. The temperature perceived as most suitable increased as the sensitivity to the thermal environment decreased. Acoustic comfort evaluations were generally higher in colder and warmer environments. Warmer environments heightened the sensitivity to the acoustic environment and this effect gradually decreased as the sound pressure levels increased. Thus, based on empirical analyses, we compared the effects of outdoor thermal-acoustic parameters on comfort to provide experimental data support for further outdoor thermal comfort research.

Emerging effects of temperature on human cognition, affect, and behaviour

Human body core temperature is tightly regulated within approximately 37 °C. Global near surface temperature has increased by over 1.2 °C between 1850 and 2020. In light of the challenge this poses to human thermoregulation, the present perspective article sought to provide an overview on the effects of varying ambient and body temperature on cognitive, affective, and behavioural domains of functioning. To this end, an overview of observational and experimental studies in healthy individuals and individuals with mental disorders was provided. Within body core temperature at approximately 37 °C, relatively lower ambient and skin temperatures appear to evoke a need for social connection, whereas comparably higher temperatures appear to facilitate notions of other as closer and more sociable. Above-average ambient temperatures are associated with increased conflicts as well as incident psychotic and depressive symptoms, mental disorders, and suicide. With mild hypo- and hyperthermia, paradoxical effects are observed: whereas the acute states are generally characterised by impairments in cognitive performance, anxiety, and irritability, individuals with depression experience longer-term symptom improvements with treatments deliberately inducing these states for brief amounts of time. When taken together, it has thus become clear that temperature is inexorably associated with human cognition, affect, and (potentially) behaviour. Given the projected increase in global warming, further research into the affective and behavioural sequelae of heat and the mechanisms translating it into mental health outcomes is urgently warranted.

Cooling Effect of Green Spaces on Urban Heat Island in a Chinese Megacity: Increasing Coverage versus Optimizing Spatial Distribution

Enhancing the cooling effectiveness of green spaces (GSs) is crucial for improving urban thermal environments in the context of global warming. Increasing GS coverage and optimizing its spatial distribution individually proved to be effective urban cooling measures. However, their comparative cooling effectiveness and potential interaction remain unclear. Here, using the moving window approach and random forest algorithm, we established a robust model (R2 = 0.89 ± 0.01) to explore the relationship between GS and land surface temperature (LST) in the Chinese megacity of Guangzhou. Subsequently, the response of LST to varying GS coverage and its spatial distribution was simulated, both individually and in combination. The results indicate that GS with higher coverage and more equitable spatial distribution is conducive to urban heat mitigation. Increasing GS coverage was found to lower the city's average LST by up to 4.73 °C, while optimizing GS spatial distribution led to a decrease of 1.06 °C. Meanwhile, a synergistic cooling effect was observed when combining both measures, resulting in additional cooling benefits (0.034-0.341 °C). These findings provide valuable insights into the cooling potential of GS and crucial guidance for urban green planning aimed at heat mitigation in cities.

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.

The urban heat island under extreme heat conditions: a case study of Hannover, Germany

Global warming has resulted in higher frequencies of climate extremes, such as drought periods or heat waves. Heat waves are intensified in urban areas due to the urban heat island effect. Studies are inconclusive as to whether the urban heat island effect is intensified during heat waves. Using the city of Hannover, Germany, as a case study, we analysed the intensity of the urban heat island under unprecedented summer heat conditions in the years 2018, 2019 and 2020, which were among the hottest in Germany since weather records began. We compared the intensity of the urban heat island across these years with the non-heat year of 2017. Differences were analysed for various inner-city urban locations and an urban park, while accounting for their distinct land use and land cover characteristics. We identified the urban heat island effect across all years investigated in the study and also found a significant intensified urban heat island effect during the years of unprecedented heat, when night-time temperature minima are considered. The urban heat island was identified on a lower level, however, with maximum daily temperatures when compared to the non-heat year. The lowest intensity of the urban heat island was found for the urban park site, highlighting the need for more city-wide greening strategies, including tree-covered and open green spaces, to provide all residents with the cooling services of green spaces.

Field Measurement of the Dynamic Interaction between Urban Surfaces and Microclimates in Humid Subtropical Climates with Multiple Sensors

Forcing pathways between urban surfaces (impervious and pervious pavers) and near-surface air temperature were measured and investigated with a network of multiple sensors. Utilizing field data measured between April 2021 and May 2022, and assuming that the influential variables follow the basic heat-transfer energy-balance equations, multiple regression-based statistical models were built to predict the surface temperature and near-surface air temperature (0.05 m, 0.5 m, 1 m, 2 m, and 3 m) of one impervious paver site and one pervious paver site in Taipei City, Taiwan. Evaporative cooling was found to be more influential on the pervious paver with a statistically significant influence on the microclimate up to 1.8 m (and up to 0.7 m for the impervious paver), using in situ data with an ambient air temperature higher than 24 °C. The surface temperature is mainly affected by solar shortwave radiation and ambient air temperature. As for near-surface air temperature, ambient air temperature is the most influential factor, followed by surface temperature. The importance of surface temperature indicates the influence of upwelling longwave radiation on the microclimate. The predictive equations show that pervious surfaces can help cities with hot and humid climates fight the changing climate in the future.

Microscale models and urban heat island studies: a systematic review

Urban climate analysis usually uses data from weather stations, traverse, or satellite images. However, this methodology also has its limitations, since the series of data for climate monitoring can be scarce. Another option that has been earning attention in recent years is numeric models, which perform simulations in urban climate. Obtaining climate data is extremely important for climatology, as well as for related areas, such as urban planning, which uses this data to know how to best order the territory according to climate conditions and their projections. Our study aimed to carry out a literature review regarding urban heat island analysis methodologies, with emphasis on the use of models. We evaluated over 200 scientific documents and we used 68 in the results of this work, reporting different types of models. The results indicated that most of the works on urban climate use a more traditional methodological approach, with fieldwork, whereas studies with models have been carried out in a specific way, especially in cities in the northern hemisphere. Among the articles evaluated, the majority were published in Elsevier publisher journals, which have a more interdisciplinary approach. The most studied models were ENVI-met, SOLWEIG, PALM-4U, RayMan, and TEB. In this way, this work pointed out, unlike other works of review in urban climate methodologies, the difficulty in obtaining field data, emphasizing their importance, with regard to studies of urban heat islands and urban planning. We also conclude that the progress and development of the state of the art in numerical models are conditioned to scientific investment in the area.

Influence of landscape interventions on thermal comfort under time-varying building shadow; new Gwanghwamun square case, Seoul, South Korea

This study investigated the cooling effects of landscape interventions and their relative magnitude under hybrid urban context including time-varying building shadow cast. The study focused on the practical design alternatives, rather than experimental scenarios. We conducted outdoor thermal comfort (OTC) simulation using ENVI-met, and spatial-temporal comparison analysis for three green space expansion interventions for new Gwanghwamun square, Seoul, South Korea. In addition, we statistically analyzed the relationship between TCR (tree coverage ratio), GCR (green coverage ratio), WCR (water coverage ratio) and PET (Physiological Equivalent Temperature). The correlation and regression coefficients of the relationships under different building density, building locations and shadow cast conditions were compared. As a result of three interventions comparison, the comfort zone increased almost two times, while the discomfort zone decreased to ≈70% of the current condition in the long-term alternative. As TCR increases 22%, PET decreases up to 2.6 °C in average. Tree coverage ratio showed significant importance among the landscape elements. The influence of trees was slightly different for different contexts; larger cooling effect was found in no building shadow cast and low-density buildings. However, the difference was not noticeable; the influence of trees is still effective under building shadow cast and high-density buildings. Moreover, for high tree density area (TCR>50%), temporal gap of thermal comfort between measured time that mainly caused by building shadow change was greatly reduced compared to low tree density area (TCR<5%), which suggest the important role of tree in providing consistent thermal comfort. This study provides scientific evidence for trees' cooling effect and its relative magnitude under diverse built contexts of N-S oriented urban canyon. This study also contributes to developing an inclusive thermal comfort evaluation method based on both temporal and spatial scales for the effective comparison of real-world design alternatives.

Evaluating planting strategies for outdoor thermal comfort in high-rise residential complexes: a computational fluid dynamics simulation study

This study aims to examine the impact of planting strategies on improving thermal comfort in relation to the existing buildings within real high-rise residential complexes. Using numerical simulation via ENVI-met, we compare six planting scenarios characterized by two locational schemes-open-space planting and building-vicinity planting-and three tree quantities. The results highlight the importance of planting greater numbers of trees, and also of their locations, to moderate the thermal environment. The findings of the study demonstrated that increasing the number of trees in the open space by threefold of the advisory guidelines led to a significant reduction in the average air temperature by 0.87 °C, mean radiant temperature (MRT) by 11.00 °C, physiological equivalent temperature (PET) by 4.50 °C, and wind speed by 0.30 m/s. Planting the minimum number of trees under building-vicinity reduced air temperature by 0.07 °C, MRT by 2.48 °C, and PET by 0.92 °C, while showing a slight increase in wind speed of approximately 0.01 m/s. To achieve improvements in both thermal condition and air flow, we suggest planting rows of trees parallel to the prevailing wind direction in the ventilation corridors at some distance from buildings, to minimize overlap of shade from trees and from buildings. The findings of this study will provide useful guidelines for effective planting design in dense residential areas.

Health and wellbeing implications of adaptation to flood risk

Adaptation strategies to ameliorate the impacts of climate change are increasing in scale and scope around the world, with interventions becoming a part of daily life for many people. Though the implications of climate impacts for health and wellbeing are well documented, to date, adaptations are largely evaluated by financial cost and their effectiveness in reducing risk. Looking across different forms of adaptation to floods, we use existing literature to develop a typology of key domains of impact arising from interventions that are likely to shape health and wellbeing. We suggest that this typology can be used to assess the health consequences of adaptation interventions more generally and argue that such forms of evaluation will better support the development of sustainable adaptation planning.

Combined effects of heatwaves and air pollution, green space and blue space on the incidence of hypertension: A national cohort study

Extreme heat exposure has been associated with hypertension. However, its interactive influences with air pollution, green and blue spaces are unclear. This study aimed to explore the interaction between heatwaves, air pollution, green and blue spaces on hypertension. Cohort data enrolled 6448 Chinese older adults aged 65 years and over were derived from the Chinese Longitudinal Healthy Longevity Survey (CLHLS) between 2008 and 2018. Nine heatwave definitions, combining three heat thresholds (92.5th, 95th, and 97.5th percentiles of daily maximum temperature) and three durations (≥2, 3 and 4 days) were used as time-varying variables in the analysis and were the one-year exposure before survival events. Fine particulate matter (PM ≤2.5 μm in aerodynamic diameter (PM_2.5)), the Normalized Difference Vegetation Index (NDVI) and the average proportion of open water bodies were used to reflect the air pollution, green and blue space exposures, respectively. PM_2.5, green and blue space exposures were time-varying indicators and contemporaneous with heatwaves. Mixed Cox models with time-varying variables were fitted to assess the multiplicative and additive interaction of heatwaves, PM_2.5, and green and blue spaces on hypertension, measured by a traditional product term with the ratio of hazard ratio (HR) and relative risk due to interaction (RERI), respectively. A positive multiplicative (HRs >1) and additive interaction (RERIs >0) between heatwaves and higher PM_2.5 levels was observed. There was a synergistic effect between heatwaves and decreasing greenness levels on hypertension incidence on additive and multiplicative scales. No significant interaction between heatwaves and blue space was observed in the analysis. The combined effects of heatwaves, air pollution, green and blue space exposures on the risk of hypertension varied with age, gender, and educational attainment. This study's findings complemented the existing evidence and revealed synergistic harmful impacts for heatwaves with air pollution and lack of green space on hypertension incidence.

Evidence-based guidance on reflective pavement for urban heat mitigation in Arizona

Urban overheating is an increasing threat to people, infrastructure, and the environment. Common heat mitigation strategies, such as green infrastructure, confront space limitations in current car-centric cities. In 2020, the City of Phoenix, Arizona, piloted a "cool pavement" program using a solar reflective pavement seal on 58 km of residential streets. Comprehensive micrometeorological observations are used to evaluate the cooling potential of the reflective pavement based on three heat exposure metrics-surface, air, and mean radiant temperatures-across three residential reflective pavement-treated and untreated neighborhoods. In addition, the solar reflectivity of reflective pavement is observed over 7 months across eight residential neighborhoods. Results are synthesized with the literature to provide context-based reflective pavement implementation guidelines to mitigate urban overheating where common strategies cannot be applied. The three most important contextual factors to consider for effective implementation include urban location, background climate type, and heat exposure metric of interest.

A Transdisciplinary Framework to Unlock the Potential Benefits of Green Spaces for Urban Communities Under Changing Contexts

New urban models increasingly seek to create more sustainable, livable, and healthier cities by reinvigorating green space. In this article, we highlight and briefly review several main but disconnected areas of study in which the factors that frame human-environment interactions and therefore also influence the potential well-being outcomes of those interactions are studied. We then use the intersection of affordance theory and socio-institutional programming to provide a conceptual framework that ties together these spheres of research, and we discuss some critical keys for enabling different positive green space experiences. Urban communities are not homogeneous, and accounting for the intersection between individual differences and landscape programming opens up more diverse pathways for affording positive human-environment interactions and different well-being outcomes.

Effect of different plant communities on NO2 in an urban road greenbelt in Nanjing, China

As an important part of urban ecosystems, plants can reduce NO₂ concentrations in the air. However, there is little evidence of the effects of different plant communities on NO₂ concentrations in street-scale green spaces. We used a multifunctional lifting environmental detector to investigate the impact of environmental factors and small plant communities on NO₂ concentrations in street green spaces during the summer and winter in Nanjing, China. The results showed that temperature, atmospheric pressure, and noise were significantly (P < 0.05) correlated with seasonal changes, temperature and humidity significantly (P < 0.01) influenced NO₂ concentrations in winter and summer, and the average NO₂ concentration in summer was generally higher than in winter. By comparing NO₂ concentrations in different plant community structures and their internal spaces, we found that the plant community structure with tree-shrub-grass was more effective in reducing pollution. These findings will help predict the impact of plant communities on NO₂ concentrations in urban streets and help city managers and planners effectively reduce NO₂ pollution.

The renew plans of urban thermal environment optimization for traditional districts in Xi'an, China

During the process of the high-speed urbanization in Chinese cities, the social, economic, and political status and the interaction between each factor have been more focused on urban traditional district renewal. However, the effects on urban microclimate and the residential living conditions in traditional districts are not well discussed, which is strongly related to the living comfort and citizens' well-being. In this study, two typical traditional districts in Xi'an are selected. According to the original situation of building functions and the community characteristics, two renewal plans are proposed by adding vegetation in open spaces (V), and adding vegetation combined with building redevelopment (V&B), in order to balance the living convenience and thermal environment. Via ENVI-met simulation, the effects of the district renewal plans on thermal environment including wind speed, air temperature, and mean radiant temperature are evaluated. This study provides method of environmental evaluation for traditional district renewal, which contributes to sustainable urban planning in historical districts, and provides recommendations for related policy development.

Does city-water layout matter? Comparing the cooling effects of water bodies across 34 Chinese megacities

As most cities are located around or near waterbodies, it is essential to assess the thermal effect of these waterbodies. This research focuses on 34 Chinese megacities as case studies to examine the spatial relationship between city-water layout and the thermal effect of waterbodies. Landsat-8 remote-sensing images acquired around noontime in summer were used to retrieve land surface temperatures (LST) and classify land cover. The results show that there are three types of city-water layout. For most cities, waterbodies have a cooling effect, and their mean cooling distance (ΔL_max) ranges from 431 m to 1350 m, with the maximum temperature difference (ΔT_max) ranging from - 2.21 °C to 7.83 °C. The cooling effect of waterbodies is also influenced by their spatial distribution, size, location, and background climate regions. The larger the percentage or area of waterbodies in a city, the shorter ΔL_max and the bigger ΔT_max. Waterbodies have the longest ΔL_max and the smallest ΔT_max when they are dispersed within the city, whereas they have the shortest ΔL_max and the largest ΔT_max when they are flowing through the city. The results suggest that the thermal effects of waterbodies should be seriously considered by urban planners to improve the urban microclimate.

Prediction of Individual Dynamic Thermal Sensation in Subway Commute Using Smart Face Mask

Wearable sensors and machine learning algorithms are widely used for predicting an individual's thermal sensation. However, most of the studies are limited to controlled laboratory experiments with inconvenient wearable sensors without considering the dynamic behavior of ambient conditions. In this study, we focused on predicting individual dynamic thermal sensation based on physiological and psychological data. We designed a smart face mask that can measure skin temperature (SKT) and exhaled breath temperature (EBT) and is powered by a rechargeable battery. Real-time human experiments were performed in a subway cabin with twenty male students under natural conditions. The data were collected using a smartphone application, and we created features using the wavelet decomposition technique. The bagged tree algorithm was selected to train the individual model, which showed an overall accuracy and f-1 score of 98.14% and 96.33%, respectively. An individual's thermal sensation was significantly correlated with SKT, EBT, and associated features.

Dominance of Influencing Factors on Cooling Effect of Urban Parks in Different Climatic Regions

The enhancement of the park cooling effect (PCE) is one method used to alleviate the urban heat island (UHI). The cooling effect is affected by park factors; however, the importance of these factors in the case of the PCE is still unclear. Optimizing or planning urban parks according to the importance of the influencing factors can effectively enhance the PCE. Herein, we selected 502 urban parks in 29 cities in China with three different climatic regions and quantified the PCE based on the park cooling intensity (PCI) and park cooling area (PCA). Subsequently, the relative importance of the influencing factors for the PCE was compared to identify the main factors. Consequently, certain park planning suggestions were proposed to enhance the cooling effect. The results show that: (1) the PCE increased in the order of arid/semi-arid, semi-humid, and humid regions. (2) The main factors of the PCI differed significantly in different climatic regions; however, the waterbody within a park significantly affected the PCI in all three climates. However, for the PCA, park patch characteristics were the dominant factor, contributing approximately 80% in the three climates regions. (3) In arid/semi-arid and semi-humid regions, the optimal area proportion of waterbody and vegetation within the park were approximately 1:2 and 1:1, respectively, and the threshold value of the park area was 16 ha. In contrast, in the humid region, the addition of a waterbody area within the park, to the best extent possible, enhanced the PCI, and the threshold value of the park area was 19 ha. The unique results of this study are expected to function as a guide to future urban park planning on a regional scale to maximize ecological benefits while mitigating the UHI.

Urban outdoor thermal environment and adaptive thermal comfort during the summer

The outdoor thermal environment is an important factor when measuring the livability of a city. Residents will avoid intense heat by reducing their outdoor activities, which decreases the vitality of a city and increases the energy consumed for air conditioning. Outdoor thermal comfort has a great impact on outdoor activities; therefore, we need to evaluate and design the urban outdoor thermal environments in cold regions to improve the outdoor thermal comfort level. In this study, we conducted a questionnaire survey to assess the outdoor thermal comfort and adaptive thermal comfort in four different urban forms in Xi'an during July 2019, and measuring meteorological parameters, such as the temperature, relative humidity, wind speed, and black bulb temperature. The results are showed as follows. (1) In the cold study area, urban residents generally perceived the outdoor climate as relatively hot during the summer. (2) The participants exhibited psychological and physical adaptations in terms of their thermal comfort. In particular, when the PET was 30 °C, the MTCV was about 1.25 points higher in the later summer period than the early summer period. (3) The neutral PET differs among regions, and it is affected by the climate zone and latitude. Comparisons of our results with thermal comfort studies in different regions such as Singapore and Umeå in north Sweden showed that the thermal comfort is correlated with the regional climate and latitude. The neutral PET is higher in tropical regions. Our findings support the theoretical understanding of adaptive thermal comfort in cold regions and they provide a reference for formulating policies related to adaptive thermal comfort.

Spatial differences in thermal comfort in summer in coastal areas: A study on Dalian, China

Thermal comfort is an important indicator for evaluating the environment of urban public space, and appropriate thermal comfort can effectively prolong the duration of outdoor activities. In the existing studies, there is a lack of thermal comfort comparison between hot spots and cold spots. In this study, we selected the coastal city of Dalian in China as our study area and conducted field investigations on the thermal comfort of two landmark resorts, namely, a downtown commercial street and coastal leisure park. The study was conducted on typical summer days and consisted of interviewing several residents to understand their thermal comfort requirements. We investigated the thermal expectations of the interviewees through meteorological measurements and questionnaires. The universal thermal climate index (UTCI) was used to determine the thermal benchmarks of the on-site subjects. The results indicated that (1) globe temperature and air temperature were the most important factors that affected thermal comfort, followed by relative humidity and wind speed in summer daytime. (2) Shaded spaces are more comfortable than open spaces, and tree shade is preferred over artificial shade in coastal park. (3) The neutral UTCI (NUTCI) of the respondents were 24.1°C (coastal park) and 26.0°C (commercial street); the neutral UTCI ranges (NUTCIR) were 20.8-27.4°C (coastal park) and 23.3-28.7°C (commercial street). (4) The upper thermal acceptable range limits of the coastal park and commercial street were 30.2 and 32.1°C, respectively, which were substantially higher than the upper NUTCIR limit, indicating that the residents in Dalian were well-adapted to hot weather. The results can provide a good reference for determining ideal design strategies to optimize the thermal environment of urban outdoor recreation spaces in summers and improve the quality of life in coastal cities.

Urban ventilation corridors and spatiotemporal divergence patterns of urban heat island intensity: a local climate zone perspective

Urban ventilation corridors introduce fresh air into urban interiors and improve urban livability, while mitigating the urban heat island (UHI) effect. However, few studies have assessed the impact of urban ventilation corridors on UHI intensity (UHII) from the perspective of the local climates of different cities. Therefore, this study integrated multisource data to construct ventilation corridors from the perspective of local climate zone (LCZ) and analyzed its impact on UHII. The results showed the following: (1) the average UHII of constructed LCZs was higher than that of natural LCZs, among which the building type LCZ10 (heavy industry) had the highest intensity (5.77 °C); (2) in extracted ventilation corridors, the pixel number of natural LCZs was substantially larger than that of constructed LCZs, among which LCZE (bare soil/paved) was the largest; and (3) for natural LCZs, the average UHII of each LCZ was lower within the ventilated corridors than within the non-ventilated corridors (except for LCZG [water]), with the UHII of LCZB (scattered trees) exhibiting the greatest mitigation effect. Quantitative research on the composition and function of ventilation corridors can not only assess the ability of ventilation corridors to mitigate UHIs, but also provide a reference for urban ventilation corridor planning.

A study of subtropical park thermal comfort and its influential factors during summer

Outdoor thermal comfort is significantly relevant to human's quality of life. Thus, it has been frequently studied by investigators. This study explored people's thermal responses to environments and the subjective factors that might affect thermal comforts with respect to two urban parks in Xindu, a satellite city in the Chengdu Plain (CDP). CDP is located at the southwest of China, which has a subtropical climate. The environment from each of the two parks was studied using current micrometeorology and hoped-for landscape changes (tree canopies, artificial canopies, non-canopying plants, and water surfaces); subjective factors included gender, age, body mass index, clothing isolation, and physical activities. It was found that canopies were the most preferred objective cooling elements, while individual thermal perceptions varied subjectively by age. The highest proportion of volunteers voted for tree canopies as their favourite thermal adjusting element. It was observed that those aged above 55 showed low thermal sensitivity. The remaining group's neutral temperatures (indicated by physiologically equivalent temperature, PET) were close, at approximately 25 °C. This study provides significant direction for future urban planning and landscape design.

Change of Rice Paddy and Its Impact on Human Well-Being from the Perspective of Land Surface Temperature in the Northeastern Sanjiang Plain of China

Large-scale and high-speed paddy land expansion has appeared in Northeast China since the 21st century, causing the change in land surface temperature. The lack of continuous investigation limits the exploration of discoveries in this region. To address this limitation, a collaborative approach that combined human-computer interaction technology, gravity center model and spatial analysis was established. It provided some new findings in spatiotemporal evolution, migration trajectory and surface cooling effect of the paddy field in Northeastern Sanjiang Plain, a center of paddy field planting in China. The results show that: (1) A sustained paddy expansion was monitored, with a total area ranging from 2564.58 km² to 11430.94 km², along with a rate of growth of 345.72% from 2000 to 2020. Correspondingly, its reclamation rate changed to 47.53% from 10.66%, showing the improved planting level of the paddy field. (2) Gravity center of paddy field continued to be revealed northward with a 5-year interval from 2000 to 2020. Migration distance of the straight line reached 23.94 km², with the direction offset of 27.20° from east to north. (3) Throughout the growing season of crops, the land surface temperature of paddy field was 27.73°, 29.38°, 27.01°, 25.62° and 22.97° from May to October; and the cooling temperature effect of paddy field was investigated, with the reduced values of 0.61°, 0.79° and 1.10° in the low-, medium- and high-paddy field density regions from 2000 to 2020, respectively. Overall, these new findings in the cold temperate zone, high latitude region of the Northern Hemisphere, provided the reference for the investigation of paddy field monitoring and its environmental effects in China and other regions.

Improvement Strategies for Microclimate and Thermal Comfort for Urban Squares: A Case of a Cold Climate Area in China

Urban squares are an important part of a city’s overall spatial environment. However, many urban squares lack rational designs, causing the thermal environment to deteriorate. To ensure sustainable urban development, urban square microclimates should be improved. Given that, this study investigates the effects of three coverages of three landscape elements of urban squares through modeling and simulation using the ENVI-met model validated by field measurements. The correlation between physiological equivalent temperature (PET) and different amounts of landscape elements is investigated using Spearman analysis. This study presents a case study of a typical urban square in a cold climate area. Design strategies in the area are proposed. The results show that the microclimate and thermal comfort of the urban square can be improved by expanding water bodies, modest increasing buildings and optimizing vegetation. Vegetation is the most important landscape element affecting thermal comfort in the urban square. The PET can be reduced by about 1.5 °C by increasing the vegetation cover from 40% to 70%. However, the degree of microclimate regulation by vegetation is disturbed by water bodies and buildings (|ρ| ≥ 0.5). Therefore, to achieve a more comfortable thermal environment, a combination of landscape elements should be considered.

Effects of residential building height, density, and floor area ratios on indoor thermal environment in Singapore

Building height, building density, and floor area ratio are the three key parameters in urban planning. However, little is known about their impact on indoor thermal environments as compared with outdoor thermal environments. The study aimed to investigate their impact on indoor air temperatures in Singapore. Singapore's residential buildings were reviewed from the perspective of the three parameters, and the Envi-met model was employed for simulation after its accuracy was confirmed by field experiments. Indoor air temperatures under 18 scenarios were simulated and analyzed. The analytical results revealed that among the three parameters, the building density was the most influential. An increase in building density reduced the indoor temperature. In Singapore, the building density increases from 0.0625 to 0.766, which reduced the mean indoor temperature by 4.7 °C. The indoor temperature decreased slightly with an increase in building height. An increase in building height from 12 to 72 m produced an indoor temperature decrease of approximately 1.7 °C. The influence of floor area ratio on indoor air temperature was the most complex. For a fixed floor area ratio of 2, the indoor temperature first increased and then decreased with an increase in building density, which resulted in an indoor temperature difference of 2.1 °C when the building density increased from 0.141 to 0.766.

Experimental and Numerical Analysis on Effect of Passive Cooling Methods on an Indoor Thermal Environment Having Floor-Level Windows

Natural ventilation is a common passive cooling method for improving air quality and thermal comfort; however, hot temperatures in summer and safety and privacy issues at night often result in its unideal performance. Therefore, we proposed the use of floor-level windows, mainly combined with microclimate improvement, to improve the indoor thermal environment by enhancing the cooling effect of natural ventilation during summer. Our study area was a house in Machida, Tokyo. We evaluated the effectiveness of our method in improving the indoor thermal environment in summer and performed a numerical simulation, while illustrating the detailed horizontal and vertical distribution of airflow in the house through the floor-level windows. The influence of different window types and opening angles of floor-level windows on ventilation and cooling was determined using the simulation. We found that: (a) natural ventilation-based passive cooling methods reduced semi-outdoor and indoor temperature and increased the humidity; (b) the airflow formed an indoor wind path; south-westerly inflow was from western floor-level windows and the skylight, and the outflow was from northern floor-level windows; and (c) the side hung windows (with an opening angle of 60°) were an ideal option to improve indoor airflow. However, there was no improvement in the passive cooling performance, due to the inflow of warmer outside air.

Indoor Temperature and Relative Humidity Dataset of Controlled and Uncontrolled Environments

The large volume of data generated with the increasing development of Internet of Things applications has encouraged the development of a large number of works related to data management, wireless communication technologies, the deployment of sensor networks with limited resources, and energy consumption. Different types of new or well-known algorithms have been used for the processing and analysis of data acquired through sensor networks, algorithms for compression, filtering, calibration, analysis, or variables being common. In some cases, databases available on the network, public government databases, data generated from sensor networks deployed by the authors themselves, or values generated by simulation are used. In the case that the work approach is more related to the algorithm than to the characteristics of the sensor networks, these data source options may have some limitations such as the availability of databases, the time required for data acquisition, the need for the deployment of a real sensors network, and the reliability or characteristics of acquired data. The dataset in this article contains 4,164,267 values of timestamp, indoor temperature, and relative humidity acquired in the months of October and November 2019, with twelve temperature and humidity sensors Xiaomi Mijia at the laboratory of Control Systems and Robotics, and the De La Salle Museum of Natural Sciences, both of the Instituto Tecnológico Metropolitano, Medellín—Colombia. The devices were calibrated in a Metrology Laboratory accredited by the National Accreditation Body of Colombia (Organismo Nacional de Acreditación de Colombia—ONAC). The dataset is available in Mendeley Data repository.

Comparing the effects of sun and wind on outdoor thermal comfort: A case study based on longitudinal subject tests in cold climate region

Sun and wind are important physical factors that influence outdoor thermal comfort. This study compared the impact of sun and wind on outdoor thermal sensation by analyzing 3546 samples of subject test data during a case study in a cold climate city Tianjin, China. The data was collected from subject tests conducted under air temperatures ranging from 3.8 °C to 35.2 °C (mean 20.2 °C), wind from 0 to 4.8 m/s (mean 0.6 m/s), mean radiant temperature 1.8 to 68.9 °C (mean 36.8 °C) in Tianjin, China. In this particular study, the sun was found to be a more significant factor than wind during the test. Standardized linear regression of the pooled dataset revealed that the contributions of air temperature, sun, wind, and humidity to thermal sensation were 56%, 29.4%, 8.8%, and 5.9%, respectively. When compared under different air temperature ranges, the effect of sun was more than two times greater that of wind. When the air temperature was in the range of 5-10 °C, solar exposure increased the thermal sensation by more than 2 units, but a reduction in wind speed had no observable effect on thermal sensation. When the air temperature was as high as 30-35 °C, increasing the wind by up to 2 m/s lowered the thermal sensation in the shade, but not in the sun. A summary of pedestrian level wind measured in real urban spaces in 28 previous studies indicated that urban spaces generally have low wind speeds, with the median value of mean wind speed of 0.8 m/s. The results of this study provide useful information for designs to creating comfortable urban open spaces.

Spatial and temporal analysis of the increasing effects of large-scale infrastructure construction on the surface urban heat island

With the rapid development of China's economy and the continuous improvement of people's living standards, large-scale infrastructure constructions (LSICs) are also increasing rapidly. LSICs with impervious surfaces have increasingly resulted in replacing natural landscapes, altering surface radiation, thermal properties, and humidity in urban areas. To study the environmental thermal changes of Beijing Daxing International Airport before and after its construction and operation, four Landsat-8 images (from the year of 2014, 2017, 2019, and 2021) were used to calculate the land surface temperature (LST). Then the LST values of four images covering the study area were compared and analyzed using the urban heat island ratio index (URI). Results show that the URI value of this area increased from 0.120 of 2014 to 0.185 of 2017 after the construction of Daxing Airport, indicating that the urban surface heat island effect in this area greatly increased. Additionally, the URI value of this area increased from 0.153 of 2019 to 0.206 of 2021 after the operation of Daxing Airport, indicating that the surface urban heat island effect in this area further increased. Therefore, we infer that this effect is closely related to airport construction and operation. Afterward, the random forest classification algorithm is used to classify land types based on pixels, and then the relationship between URI and land classification types was discussed. It is found that before the construction of Daxing Airport, both dark buildings and bare land contribute significantly to the thermal environment of the airport. After the completion of Daxing Airport, the contribution model was changed to high-reflectivity buildings and bright soil. The thermal pollution generated by the airport has a greater impact on the ground objects within the range of 7.5 km, and a relatively smaller impact on the ground objects outside the range of 9.5 km. Our results can provide a valuable reference for the study of the thermal environment caused by human activities.

Study on the Effect of Vegetation Coverage on Urban Cooling and Energy Conservation: A Case Study of a Typical Hilly City, Chenzhou, China

Urban vegetation coverage is a core index in urban planning, which has been confirmed to be an effective indicator for the urban thermal environment. Through the urban thermal environment, this study aims to further quantify the impact of vegetation coverage on urban energy consumption. Chenzhou, a typical hilly city, was selected as the study object for its diversified vegetation coverages. Remote sensing technology and correlation and regression models were employed in this study. Firstly, the data of land surface temperature and vegetation coverage were calculated with remote sensing technology, followed by data analysis with the correlation and regression models. Then, employing the “λ-T” model, a statistical model corresponding to urban temperature and energy, this study clarified the impact of temperature on urban energy consumption. Finally, through urban temperature, this study analyzed the impact of urban greening coverage on urban energy consumption. This study shows that when the temperature ranges from 22 °C to 28.9 °C, every 10% of additional vegetation coverage will reduce the air conditioning energy demands by 5.5%, and when the temperature is between 28.9 °C and 37 °C, every 10% of additional vegetation coverage will reduce the mean air conditioning energy demands by 2.4%.

Spatial Heterogeneity and Attribution Analysis of Urban Thermal Comfort in China from 2000 to 2020

Research on urban thermal environments based on thermal comfort can help formulate effective measures to improve urban thermal and human settlement environments, which is of great significance for improving urban quality, urban climate change adaptation, and sustainable development. Taking 344 municipal administrative districts in China as study areas, the Universal Thermal Climate Index (UTCI) of each city in the last 20 years was calculated to evaluate thermal comfort. We then analyzed the thermal comfort and spatiotemporal heterogeneity of each city during a typical heat wave. Finally, the driving forces of the potential socioeconomic, natural, and landscape factors influencing thermal comfort were analyzed using geographic detectors. The results show that the thermal comfort index had similar spatial patterns and differentiation characteristics in different years, and the interannual variation was not obvious. Cities in the typical heat wave period were mainly distributed in East and Northwest China. The driving factor in the contribution rate of the same index in different years was basically the same and was not affected by the change in years, and the highest contribution rate was the natural factor.

Influence of Vegetation on Outdoor Thermal Comfort in a High-Altitude Tropical Megacity: Climate Change and Variability Scenarios

The objective of this paper is to show a study on the influence of vegetation on the outdoor thermal comfort (OTC) of a high-altitude tropical megacity. The OTC is evaluated by the PET (Physiological Equivalent Temperature) index and by establishing three simulation scenarios: (i) Current OTC, (ii) OTC under RCPs 4.5 and 8.5 (Representative Concentration Pathway), and (iii) OTC under RCPs and ENSO (El Niño–Southern Oscillation). The results show that the hourly variation range of the current OTC in urban areas with vegetation is greater (+3.15 °C) compared to impermeable areas. Outdoor thermal stress due to cold in vegetated areas is 1.29 °C lower compared to impervious areas. The effect of vegetated coverage on the improvement of urban OTC increases as the phenomenon of global warming intensifies. On average, in the current, RCP4.5, and RCP8.5 scenarios for each 10% increase in urban vegetation coverage, an increase of 0.22, 0.24, and 0.28 °C in OTC is obtained, respectively. The hourly variation range of the PET index increases during the ENSO scenario (vegetated areas: +16.7%; impervious areas: +22.7%). In the context of climate change and variability, this study provides a reference point for decision-makers to assess possible planning options for improving OTC in megacities.

Quantifying Interactive Cooling Effects of Morphological Parameters and Vegetation-Related Landscape Features during an Extreme Heat Event

In this study, we apply the ENVI-met model to evaluate the effects of combinations of morphological and vegetation-related landscape features on urban temperatures and thermal comfort. We simulated the thermal conditions of 126 scenarios, varying the aspect ratios of street canyons, vegetation cover and density, surface materials, and orientations toward the prevalent winds under an extreme heat situation. Our results show how the effects of physical and vegetation parameters interact and moderate each other. We also demonstrate how sensitive thermal comfort indices such as temperature and relative humidity are to the built environment parameters during different hours of a day. This study’s findings highlight the necessity of prioritizing heat mitigation interventions based on the site’s physical characteristics and landscape features and avoiding generic strategies for all types of urban environments.

Exploring Adaptive UHI Mitigation Solutions by Spatial Heterogeneity of Land Surface Temperature and Its Relationship to Urban Morphology in Historical Downtown Blocks, Beijing

Heat stress brought on by the intensification of urban heat island (UHI) has caused many negative effects on human beings, which were found to be more severe in highly urbanized old towns. With the inconsistent findings on how urban spatial morphological characteristics influence land surface temperature (LST) and gaps between design practices being found, we chose Beijing Old Town (BOT) as the study area and took the basic planning implementation module “block” as a study to reveal the spatial heterogeneity of LST and its relationship to multiple urban morphological characteristics with higher spatial resolution calculated via WorldView3. Our results have shown that (1) UHI effect was significant and spatially heterogeneous in BOT, and significant hot areas with high LST value and small LST differences were found, as cold areas were the exact opposite. (2) The proportion of vegetated area, water, impervious surface, and urban spatial structure indicators i.e., building coverage ratio, mean height, highest building index, height fluctuation degree, space crowd degree and sky view factor were identified as significantly affecting the LST of blocks in BOT. (3) The effects of GBI components and configuration on LST varied within different block types; generally, blocks with GBI with larger patches that were more complex in shape, more aggregated, and less fragmented were associated with lower LST. Finally, in the context of integrating our study results with relevant planning and design guidelines, a strategy sample of adaptive GBI planning and vegetation design for blocks with different morphological features was provided for urban planners and managers to make a decision on UHI mitigation in the renewal process of BOT.

Quantification of Outdoor Thermal Comfort Levels under Sea Breeze in the Historical City Fabric: The Case of Algiers Casbah

Thermal comfort in cities is an influential factor for citizens’ wellbeing and life quality. Urban microclimate studies have gained popularity following increasing urbanization trends and global climate change in recent years. Urban fabric and morphology in traditional cities represent a unique pattern both spatially and climatically. However, few studies have investigated traditional cities’ urban thermal comfort conditions. Therefore, this study aimed to assess the thermal comfort in different subspaces of Algiers Casbah’s historic urban fabric, which falls in the hot Mediterranean climate (Csa). This research evaluated the human thermal sensation by applying the physiological equivalent temperature (PET) index. The methodology used was a mixed approach, including field measurements, calculations, and a survey questionnaire. The results indicate the presence of a high-stress level during the measurement periods, and notable differences between the subspaces in January (ΔPETMax.Jan = 3.7 °C) and August (ΔPETMax.Aug = 2.2 °C). The highest discomfort was recorded in spaces with collapsed buildings, especially during the hot hours of the day. The findings also highlight a strong impact of the sky view factor on the mean radiant temperature (Tmrt) and the physiological equivalent temperature (PET). The study discusses recommendations and ways to improve the design of outdoor spaces and relieve heat stress in the streets of traditional cities. Finally, this work helps urban managers and heritage conservators in urban rehabilitation policies concerning outdoor microclimate improvement.

Biochar-Based Compost Affects Bacterial Community Structure and Induces a Priming Effect on Soil Organic Carbon Mineralization

Urban forests are key to mitigating the Urban Heat Island Effect, which contributes to temperature increases in urban areas. However, the trees in these forests are usually under stress because urban soil is typically degraded. Biochar/compost amendments help with soil management by improving the physiochemical properties and bacterial communities of soil. Here, we compared the physiochemical properties and bacterial communities before and after (1) biochar-only and (2) biochar-based compost amendments. Our results suggested that biochar-only application did not improve soil properties after 1 year of treatment, whereas in the biochar-based compost treatment, the soil properties and bacterial communities changed after just four months. The increase in potassium and decrease in organic material, calcium, and available phosphorus in the soil of the former treatment indicated that the nutrient uptake of its trees had improved. Although there was no significant variation in the soil’s total nitrogen, the higher abundance of potential nitrogen-fixing bacteria in the biochar-based treatment suggested that the soil contained a supplement to nitrogen. Our results show that biochar-based compost amendment improves soil quality and associated bacterial communities in urban forest management.

Effect of Environmental Planning on Elderly Individual Quality of Life in Severe Cold Regions: A Case Study in Northeastern China

With the development of urbanization and the ageing population, the improvement of the urban environment and the quality of life (QOL) of the elderly in cities with a cold climate have become critical issues to be addressed. However, only a few studies have focused on this aspect. According to a review of the literature, the contents of the built environment (BE) in severe cold regions are defined as thirteen key factors of four categories (density, environmental aesthetics, outdoor environment, and accessibility) and the QOL of old people consists of three aspects (residential, health, and social satisfaction). This study explores how BE variables are associated with the QOL of older adults by using ordered logit and gologit2 models. The data consist of the results of 1945 questionnaires from field surveys in 11 different residential areas, across two cities in northeastern China. The results show: (1) Walkability in winter, distance to a public park of 400–1000 m, outdoor shelters and seating, less than five buses available, and a mixture of evergreen and deciduous trees are five of the most important variables of BE that have a significant positive impact on QOL compared with other climatic regions; (2) “Pocket parks” and pedestrian walkway safety are appropriate approaches to improve wellbeing under local economic conditions. For public transportation, metro and rail transit systems are encouraged, and some rules are needed to reduce the number of buses in harsh weather conditions; (3) Compared with spatial distribution in other climates, the scope of a 15 min city should be less than 1km in severe cold areas. From the findings, we conclude that there are six possible pattern languages to improve the urban environment, and they can provide information for further study on environmental planning in severe cold regions.

Improving Outdoor Thermal Comfort in a Steppe Climate: Effect of Water and Trees in an Urban Park

Excess heat in urban environments is an increasing threat to human health and well-being. Furthermore, the increasingly important phenomenon of the Urban Heat Island (UHI) is exacerbating problems of livability in urban centers. Hence, there should be an increasing effort to assess the impact of heat mitigation strategies (HMSs) on outdoor thermal comfort in cities. This research has investigated how urban areas in steppe climate zones can be more thermally comfortable due to the effects of water bodies and trees, and how this might help to mitigate heat waves. Numerical simulations using the ENVI-met microclimate model have been performed for an urban park in Tabriz, Iran. In-situ measurements of air temperature (Ta) and mean radiant temperature (MRT) have been carried out in the study site and the collected data was used to validate the model (RMSE value 0.98 °C for Ta and 5.85 °C for MRT). Results show that water body evaporation without trees may decrease the air temperature, but on the other hand also increases the humidity, which reduces the positive impact on thermal comfort. However, the combination of water body with trees represents a better performance in the regulation of urban microclimate and thermal comfort.

Effect of Urban fringes green space fragmentation on ecosystem service value

In this study, an urban fringe green space classification system was established to explore the spatiotemporal variation of green space landscape and ecosystem service value (ESV) based on multi-source land-use data of Ganjingzi district from 2000 to 2018. (1) Results show that the total green space area declined from 359.57 to 213.46 km² over the study period. Green space large plaque index (LPI) and class area both gradually declined, whereas the number of plaques (NP) and plaque density (PD) gradually increased, indicating green space landscape fragmentation. (2) Additionally, the value of green space ecosystem services reduced from 397.42 to 124.93 million yuan. The dynamic degree of ESV change in green space increased or decreased moderately, always being < 0 and showing a decreasing trend of ESV. From a spatial variation perspective, dynamic degrees of ESV variation in the western and northern regions with relatively intensive green space were higher than those in the east. Regarding ESV of various green space types, forest land had the highest functional values of ecological regulation and support, whereas arable land provided the highest functional values of production supply. (3) The ecological service function value of green space system is negatively correlated with PD, NP, edge density, landscape shape index, and Shannon’s diversity index, and positively correlated with aggregation index, contagion metrics, and LPI. The correlation coefficient between the climate regulation function of forest and the change of number of plaques is -0.874. The correlation coefficient of the recreation and culture of the wetland to the plaque density change is no less than -0.214.

Cool Surface Strategies with an Emphasis on the Materials Dimension: A Review

The need to tackle the urban heat island effect demands the implementation of cool surfaces as a mitigation strategy. This study comprehensively reviews the evolution of this research field from a materials perspective. It provides a bibliometric analysis of the relevant literature using the SciMAT software processing of bibliographic records from 1995 to 2020, for the evolution of cool surfaces. The results obtained show an increased interest in the field from 2011 to 2020, particularly for roof applications, and present the scientific evolution of reflective materials. According to the materials dimension adopted by the development of the research field, the study is refined from a bibliometric analysis of 982 selected records for the analysis of five themes: (i) Pigments; (ii) Phase change materials; (iii) Retroreflective materials; (iv) Ceramic materials; and (v) Glass. These materials present promising results in terms of their solar reflectance performances in the mitigation of the urban heat island phenomenon. At the end of this review, recommendations for future studies are provided for the creation of economic and environmentally friendly materials based on waste glass recycling. This study represents a valuable contribution that provides a scientific background with regard to cool surfaces from a materials perspective for future investigations.

Numerical Study on Microclimate and Outdoor Thermal Comfort of Street Canyon Typology in Extremely Hot Weather—A Case Study of Busan, South Korea

As cities are extremely vulnerable to the impacts of climate change, they are fundamental in addressing these changes. However, streets, which are external spaces accessed by citizens in daily life, play an important role in improving the urban environment and public health. This study considered Busan in South Korea as a case study to investigate street canyons, including street canyon geometries and tree configurations, of old, present, and new city centers. The influence of morphological factors on the microclimate and outdoor thermal comfort was evaluated using the ENVI-met program for extremely hot weather. Changes in the street width, street orientation, and street canyon aspect ratio had a significantly higher impact on the microclimate and thermal comfort index (p < 0.01). These results indicated that the orientation of the main street should be consistent with the prevailing wind direction of Busan. Further, the shading of adjacent buildings improved the outdoor thermal comfort and reduced the significance of tree configuration in deeper street canyons. In addition, tree height had a more significant impact on street environment than other tree configuration factors, especially when the tree height increased from 9 m to 12 m. We recommended that the thermal comfort level can be improved by dynamically adjusting the relationship between the planting distance and tree height in streets having shallow street canyons.

Microclimatic Landscape Architecture: From Theory to Application

Global climate change and urban heat island intensification are making many cities dangerously hot during heat waves. There is a need for a clear process for applying microclimate information in urban design to create cooler cities. A recent paper points out the gaps in research methodology and suggests the need for implementation-oriented research. It suggests action steps to take research from theory to practice. The framework has five steps, and in our paper, we have addressed four of those steps: (1) understanding the needs of designers; (2) integrated research on urban microclimate factors; (3) development of guidance methods for better design; and (4) developing user-friendly tools. To address the first step, a group of Chinese landscape architects was given a questionnaire and it was found that they perceived principles and guidelines as being the most useful microclimatic design methods. The second step was addressed through a case study with on-site measurements and modeling. In step 3, microclimate information was used to redesign the site. The process that followed addressed the fourth step by illustrating user-friendly tools.

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 (PET_neutral) of 23.75 °C for Mumbai in the winter. PET_neutral 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.

Urbanization Impact on Regional Climate and Extreme Weather: Current Understanding, Uncertainties, and Future Research Directions

Urban environments lie at the confluence of social, cultural, and economic activities and have unique biophysical characteristics due to continued infrastructure development that generally replaces natural landscapes with built-up structures. The vast majority of studies on urban perturbation of local weather and climate have been centered on the urban heat island (UHI) effect, referring to the higher temperature in cities compared to their natural surroundings. Besides the UHI effect and heat waves, urbanization also impacts atmospheric moisture, wind, boundary layer structure, cloud formation, dispersion of air pollutants, precipitation, and storms. In this review article, we first introduce the datasets and methods used in studying urban areas and their impacts through both observation and modeling and then summarize the scientific insights on the impact of urbanization on various aspects of regional climate and extreme weather based on more than 500 studies. We also highlight the major research gaps and challenges in our understanding of the impacts of urbanization and provide our perspective and recommendations for future research priorities and directions.

Effects of Urban Landscape and Sociodemographic Characteristics on Heat-Related Health Using Emergency Medical Service Incidents

It is well known that extremely hot weather causes heat-related health issues. Health problems, especially in urban areas, are becoming increasingly important due to urban heat island effect. Understanding the impact of neighborhood characteristics is important for research into the relationship between thermal environment and human health. The objectives of this study were to explore the urban landscape and sociodemographic characteristics affecting heat-related health and identify spatial inequalities for vulnerable groups. A total of 27,807 heat-related EMS incidents were used at the census block group level (N = 285). We used land cover database and Landsat satellite images for urban landscape variables and used 2019 U.S. Census data for sociodemographic variables. Negative binomial regression was used to identify the neighborhood variables associated with the heat-related EMS incidents in each block group. Heat-related health has been alleviated in block groups with high green areas. However, the negative effects of thermal environments on human health were higher in areas with a high percentage of impervious surface, over 65 years, non-white people, no high school diploma, or unemployment. The results indicate that heat-related health problems can be addressed through prevention strategies for block group variables. Local intervention efforts to solve health issues should be targeted at more vulnerable areas and groups.