Search Results (36)

The urban heat island (UHI) significantly compromises outdoor thermal comfort and public health in hot climates. While urban vegetation is a recognized mitigation strategy, its performance variability across different urban fabrics remains a critical knowledge gap. This research quantitatively evaluates the microclimatic impact of vegetation strategies by comparing two districts with distinct urban morphologies: low-density and high-density. Using the Envi-met software, we simulated a reference case and four vegetation scenarios with constant 50% grass coverage and incrementally increasing tree percentages (0% to 75%). Thermal performance was assessed through key metrics, including air temperature (T_a), relative humidity (RH), mean radiant temperature (T_mrt), and Physiologically Equivalent Temperature (PET). The results reveal that vegetation’s effectiveness is directly correlated with urban density. The most comprehensive strategy (Scenario-D: 50% grass, 75% trees) reduced peak PET by up to 7.5 °C in the low-density El Khazzan, a reduction nearly three times greater than the 2.7 °C achieved in the high-density El Akkad. Similarly, this scenario achieved a maximum daytime T_a reduction of 0.92 K in El Khazzan, compared to only 0.4 K in the high-density district. The study also identifies a critical trade-off: high-density tree scenarios increased nighttime temperatures by up to 0.4 K due to disrupted airflow, whereas the grass-only scenario maintained thermal stability. These findings underscore that a one-size-fits-all approach to urban greening is insufficient. For practical implications, urban planners must abandon generic strategies and integrate a nuanced understanding of local morphology to maximize the thermal benefits of vegetation, particularly in hot, arid environments. Full article

The rapid urbanization in developing countries has resulted in altered land-use patterns, surface energy imbalances, and heightened urban heat stress, exacerbating the urban heat island effect and vulnerability to heatwaves. The abandonment of agricultural lands, while a global challenge, presents cities with a unique opportunity to meet tree cover targets and improve resilience to these climatic challenges. Building on prior studies, this research employs the combined use of ENVI-met 4.4.6 and Ray-Man 3.1 simulation models to assess the efficacy of nature-based solutions in revegetating abandoned urban agricultural lands with the aim of enhancing outdoor thermal comfort. As a vital component of urban ecosystem services, thermal comfort, particularly through microclimate cooling, is essential for improving public health and livability in cities. This investigation focuses on the integration of broadleaf, evergreen, and edible woody species as bioclimatic interventions to mitigate urban heat stress. Simulation results showed that species such as Quercus spp. (broadleaf) and Cupressus arizonica (evergreen) substantially reduced the Mean Radiant Temperature (Tmrt) index by up to 26.76 °C, primarily due to their shading effects and large canopies. Combining these vegetation types with crops emerged as the most effective strategy to mitigate heat stress and optimize land-use. This study demonstrates how cities can incorporate nature-based solutions to adapt and mitigate the health risks posed by climate change while fostering resilience. These findings offer valuable knowledge for other developing countries facing similar challenges, highlighting the importance of revegetating abandoned urban agricultural lands for thermal comfort and ecosystem service provision, with the advantages of reducing mortality and morbidity during heatwaves. Consequently, these results should inform urban climate policies aimed at promoting resilience, public health, and ecological sustainability in a changing climate. Full article

The growing urban population has made densification a key focus of urban development. It is crucial to create an urban planning strategy that understands the environmental, social, and economic effects of densification at both the district and city levels. In Switzerland, densification is a legally binding aim to foster housing and jobs within urban boundaries. The challenge is to accommodate population growth while maintaining a high quality of life. Zurich exemplifies this situation, necessitating the accommodation of approximately 25% of the anticipated increase in both the resident population and associated workplaces, as of 2016. This study examined the effects of urban densification on urban forms and microclimates in the Altstetten–Albisrieden district. It developed five densification scenarios based on current urban initiatives and assessed their impacts. Results showed that the current Building and Zoning Plan provides sufficient capacity to accommodate growth. Strategies such as densifying parcels older than fifty years and adding floors to newer buildings were found to minimally impact existing urban forms. Using the SOLWEIG model in the Urban Multi-scale Environmental Predictor (UMEP), this study simulated mean radiant temperature (Tmrt) in the selected urban areas. The results demonstrated that densification reduced daytime average temperatures by 0.60 °C and diurnal averages by 0.23 °C, but increased average nighttime temperatures by 0.38 °C. This highlights the importance of addressing warm nights. The study concludes that well-planned densification can significantly contribute to urban liveability, emphasising the need for thoughtful building design to improve outdoor thermal comfort. Full article

College student military training is an organized, high-intensity, short-term militarized activity in China; this study aims to explore the differences in thermal perception between different intensities of military training. Questionnaires and microclimate measurements were conducted during summer military training in cold regions, including the Protective and Rescue Training and Assessment (PRTA), Formation Training (FT), the Shooting and Tactical Training and Assessment (STTA), the Route March (RM), and Dagger Practice (DP). The results indicated that (1) there was no significant correlation between the intensity of the activity and votes on thermal perception. The strongest thermal sensations, the lowest comfort, and the lowest thermal acceptability were experienced during FT, with a lower activity intensity. (2) Air temperature (T_a), globe temperature (T_g), relative humidity (RH), mean radiant temperature (T_mrt), and solar radiation (G) had significant effects on the TSV. (3) FT involved the lowest neutral temperatures (NUTCI/NPET), while DP and RM training had the highest NUTCI and NPET values, respectively. The neutral temperature range during military training was narrower compared to that in other aerobic activities. This study reveals, for the first time, the non-traditional correlation between military training intensity and thermal perception, confirming the specificity of thermal sensations in mandatory training and providing a theoretical basis for optimizing military training arrangements and developing thermal protection strategies. Full article

Like other mega cities in China, Beijing is undergoing a large-scale urban renewal process. However, in the context of global warming and the goal of promoting human health and well-being, urban renewal should follow the principle of minimal intervention, draw inspiration from the condition of the climate and environment itself, and pursue the goal of common health and development between humans and non-human beings. This study takes the Panjiayuan Antique Market as the research object. Unlike previous studies that focused on the behavior patterns of vendors and buyers, this study focuses on the increase in users’ expectation on environmental thermal comfort when the Panjiayuan Antique Market transforms from a conventional commercial market into an urban public space. This study aimed to find a minimal intervention strategy suitable for urban public space renewal from the perspective of the microclimate, encouraging people to use outdoor public spaces more, thereby promoting physical and mental health, as well as social well-being. We used a mixed-methods approach comprising microclimate measurements, questionnaires (n = 254), and field measurements. Our results show that the mean radiant temperature (T_mrt) is the key factor that affects thermal comfort, and it is a comprehensive concept that is associated with other microclimate factors. Linking the quantitative sun-related factors, such as the solar position angle (SAA), the shadow area ratio (SAR), and direct sun hours (DSHs), we also found that the correlation between the T_mrt and physical spatial characteristics, such as the ratio of the visible sky (SVF), the aspect ratio (H/W), and orientation of the building layout, helped us to generate design strategies oriented by regulating microclimate, such as controlling thermal mass/radiant heating, solar radiation, and air convection. One of the significances of this study is its development of a design method that minimizes intervention in urban public spaces from the perspective of regulating the microclimate. In addition, this study proposes a new perspective of promoting people’s health and well-being by improving outdoor thermal comfort. Full article

Climate change amplifies heat wave effects on outdoor thermal comfort by increasing their frequency, duration, and intensity. The urban heat island effect worsens heat risks in cities and impacts resilience. Nature-based solution (NBS) with tree plantation was reported as an effective mitigation measure. This simulation study, by the well-validated ENVI-met model, aimed to investigate the impact of different tree planting strategies and building parameters on urban heat risk mitigation and microclimate during a typical hot summer day. Hypothetical skyscrapers and super high-rise buildings were assumed in the study site located in southern China. Adopting meteorological inputs from a typical year, the simulation results revealed that both mean radiant temperature (T_mrt) and physiological equivalent temperature (PET) were elevated (T_mrt > 60 °C and PET > 50 °C) in early afternoon in sunlit areas. Three mitigation approaches with different tree planting locations were investigated. While all approaches demonstrated effective cooling (PET down to <35 °C) in the proximity of trees, a superior approach for mitigating the heat risks was not evident. Within the building array, the shade of bulky structures also lowered T_mrt and PET to a thermally comfortable level in the late afternoon. Combining open-space tree planting with optimized building designs is recommended to mitigate heat risks and enhance urban resilience while promoting outdoor activities and their health benefits. Full article

This study examines the thermal impacts of green and blue infrastructure in Hilalkent Neighborhood, Elazığ City, in Turkey, using ENVI-met 5.6.1 software. Six design scenarios were proposed and their impact on air temperature, relative humidity, mean radiant temperature (Tmrt), physiological equivalent temperature (PET), and wind speed during August and January was analyzed. The simulation results were verified via field measurements using the Lutron AM-4247SD Weather Forecast Station at a height of 2.0 m above the ground. Data were collected in August 2023 and January 2024. The findings of this study indicate that existing vegetation in the study area provides a cooling effect of 0.8 °C during August. The addition of 10% grass coverage further reduced air temperature by 0.3 °C, while a 20% increase in tree density led to a 0.6 °C temperature reduction. The inclusion of a 10% water surface resulted in a 0.4 °C decrease in air temperature, and the implementation of extensive roof gardens contributed to an additional 0.2 °C reduction during the August period. The combined implementation of blue–green infrastructure in the study area achieved a total cooling effect of 1.5 °C during August. During January, the proposed scenarios led to a reduction in average temperatures by 0.1 °C to 0.4 °C compared to the base scenario, which may not be favorable for thermal comfort in colder conditions. Relative humidity values decreased during the August and Tmrt values were directly proportional to air temperature changes in both August and January. The results of this study provide valuable insights for urban planners and policymakers, demonstrating the effectiveness of blue–green infrastructure in mitigating the urban heat island (UHI) effect. These findings highlight the importance of integrating climate-responsive design strategies into urban planning to enhance thermal comfort and environmental sustainability in cities. Full article

As global climate change intensifies, the frequency and severity of extreme weather events continue to rise. However, research on semi-outdoor and transitional spaces remains limited, and transportation stations are typically not fully enclosed. Therefore, it is crucial to gain a deeper understanding of the environmental needs of users in these spaces. This study employs machine learning (ML) algorithms and the SHAP (SHapley Additive exPlanations) methodology to identify and rank the critical factors influencing outdoor thermal comfort at tram stations. We collected microclimatic data from tram stations in Guangzhou, along with passenger comfort feedback, to construct a comprehensive dataset encompassing environmental parameters, individual perceptions, and design characteristics. A variety of ML models, including Extreme Gradient Boosting (XGB), Light Gradient Boosting Machine (LightGBM), Categorical Boosting (CatBoost), Random Forest (RF), and K-Nearest Neighbors (KNNs), were trained and validated, with SHAP analysis facilitating the ranking of significant factors. The results indicate that the LightGBM and CatBoost models performed exceptionally well, identifying key determinants such as relative humidity (RH), outdoor air temperature (Ta), mean radiant temperature (Tmrt), clothing insulation (Clo), gender, age, body mass index (BMI), and the location of the space occupied in the past 20 min prior to waiting (SOP20). Notably, the significance of physical parameters surpassed that of physiological and behavioral factors. This research provides clear strategic guidance for urban planners, public transport managers, and designers to enhance thermal comfort at tram stations while offering a data-driven approach to optimizing outdoor spaces and promoting sustainable urban development. Full article

Urban streets are critical public spaces that significantly influence the thermal comfort of city dwellers. However, the issue of summer thermal discomfort in severely cold regions has been largely overlooked. This study focuses on Youth Street in Shenyang, a city in a severely cold region, to explore the impact of various street spaces and vegetation layouts on the thermal environment and comfort using ENVI-met modeling and correlation analysis. The study varied the aspect ratio (AR) of the street, street tree species, and plant spacing across 60 scenarios and simulated thermal comfort over a 10-h period on a typical summer day. Results show that air temperature (Ta), mean radiant temperature (Tmrt) and sky view factor (SVF) are positively correlated with physiologically equivalent temperature (PET). Street trees effectively reduce Ta, increase RH and lower wind speed (WS), but plant spacing has minimal impact on WS. Higher AR values lead to greater improvements in pedestrian thermal comfort. Specifically, the highest heat mitigation rate (HMR) is observed at low AR (9.87% at AR = 0.5 and 9.94% at AR = 1.0), while it is lower at high AR (8.16% at AR = 2.0). Conversely, larger plant spacing of street trees diminishes the effectiveness of thermal comfort improvements. The improvement effect of plant spacing is more pronounced in street spaces with smaller AR. In these spaces, closer plant spacing significantly enhances thermal comfort by providing more shade and reducing Ta and Tmrt. However, in street spaces with higher AR, overly dense plant configurations can reduce WS and limit the cooling effect of ventilation, thereby diminishing overall heat mitigation ability. Conclusions suggest that urban planners should consider both street space and vegetation layouts to optimize thermal comfort. For urban main streets in severely cold regions, an AR of 1:1 with deciduous broadleaf trees and hedges planted at 6 m spacing is recommended. In high-AR streets, dense plant configurations should be avoided. This study provides valuable insights for improving the thermal comfort and sustainable design of urban street spaces, supporting new construction and development in similar climate environments. Full article

With the popularization of informal learning styles in universities, building overheads in hot and humid regions of China has become one of the main spaces for informal learning among college students in the region due to their improved thermal environmental conditions relative to outdoor spaces. However, the effects of thermal environmental changes on students’ learning performance on the overhead floors are not yet clear. Therefore, we recruited volunteers to conduct several tests, including the Stroop test, the Go/No-go test, the 2-back test, and the 3-back test, in the overhead space of a building in September and October. This was followed by a questionnaire survey, which yielded a total of 500 samples. Learning performance was quantified as a total of accuracy, response time, and final performance metrics. The results show that in hot and humid regions of China, the thermal perception of college students in the overhead was mainly related to Ta and Tmrt, and the relationship with Va was not significant; the maximum acceptable physiological equivalent temperature of college students in the overhead space was 30.3 °C; the change in the thermal environment had an effect on the learning performance of the four tests, and under neutral to slightly warm temperature (22.1–31.2 °C physiological equivalent temperature), the learning performance of the perceptually oriented and short-term memory task types increased by 2.5% and 1.1%, and the relationship between thermal environment and learning performance was not significant when the short-term memory task became more difficult. Attention-oriented learning had a relationship between the spatial thermal environment and learning performance in overhead spaces in hot and humid regions and suggests a basis for future overhead retrofitting. Full article

This study investigates the role of vegetation in enhancing thermal comfort and achieving energy savings in educational building courtyards located in hot, arid climates. The research focuses on an educational building courtyard in New Aswan City, Egypt, and employs a combination of field monitoring and numerical simulations to evaluate the thermal performance of the space. The study utilized the ENVI-met V5.5.1 model for thermal assessment and the Design-Builder software version 6.1.3.007 to quantify the potential energy savings. Nine different vegetation scenarios were proposed and analyzed to identify the most effective strategies for improving the courtyard’s thermal conditions. The results demonstrate that a 60% coverage of the courtyard with Cassia Nodosa vegetation produced the most significant improvements. This scenario led to a decrease of over 25.4 °C in physiological equivalent temperature (PET) and a reduction of more than 31.3 °C in mean radiant temperature (T_mrt). Moreover, the energy savings achieved were approximately 19.2%. Interestingly, the study also observed an unexpected decrease in the temperature mitigation efficacy of Ficus nitida when vegetation coverage was increased from 40% to 60%. This phenomenon can be attributed to the complex interplay between the inherent characteristics of the Ficus nitida species and the microclimatic factors within the courtyard environment. These findings provide valuable insights for designers and architects to integrate effective vegetation strategies into the design of educational building courtyards in hot, arid climates. By enhancing thermal comfort and reducing energy consumption, this approach can contribute to the creation of more sustainable and comfortable learning environments. Full article

To investigate the impact of landscape characteristics on microclimate and thermal comfort in summer urban parks in Xinjiang, we focused on Mingzhu Park in Shihezi City. We collected microclimatic data through field measurements and analyzed the correlations among these factors, the physiological equivalent temperature (PET), and the landscape features. ENVI-met was utilized for microclimate simulations to assess the optimization effects. The results revealed that different landscape features significantly influenced the microclimate and thermal comfort. Trees and grass effectively lowered the temperature, increased humidity, reduced wind speeds, blocked solar radiation, and decreased the PET. Water bodies exposed to sunlight and without shade have a low reflectivity, leading to significant temperature increases. While evaporation can lower the surrounding temperatures, the water surface temperature remains higher than in shaded areas, raising temperatures there. The temperature, humidity, wind speed, and mean radiant temperature show significant correlations. The correlation ranking is as follows: mean radiant temperature (T_mrt) > air temperature (T_a) > relative humidity (RH) > wind speed (V_a). After increasing the tree cover and designing dispersed water bodies, the average PET decreased by up to 0.67 °C, with the park experiencing the largest reduction of 1.86 °C. The PET in the eastern built-up area was reduced by 0.35 °C, and in the western built-up area, by only 0.13 °C. Full article

In hot, arid regions, outdoor spaces suffer from intense heat. This study explores how vegetation can improve outdoor thermal performance for pedestrians in low-density residential areas. Specifically, it seeks to identify the best combination of grass and trees for optimal comfort. Four scenarios were simulated using ENVI-met software, varying the proportions of grass and three tree types: 50% grass, 50% grass with 25% trees, 50% grass with 50% trees, and 50% grass with 75% trees. A reference scenario with no vegetation was also investigated. The simulated outputs encompassed air temperature (Ta), mean radiant temperature (T_mrt), relative humidity (RH), and physiologically equivalent temperature (PET). The findings show that scenarios with a higher percentage of trees exhibited the best reduction in air temperature, ranging from 0.2 k to 0.92 k. Additionally, the inclusion of trees and grass in the scenarios resulted in a substantial improvement in thermal performance, with an average reduction of 7.5 degrees in PET. Among the evaluated scenarios, the one comprising 75% trees and 50% grass exhibits the most noteworthy enhancement. This study underscores the significance of strategically positioning vegetation to coincide with prevailing wind patterns, thereby enhancing convective cooling mechanisms and improving overall thermal comfort levels. These insights offer valuable implications for urban planning and the development of sustainable design strategies. Full article

After two phases of on-site construction and testing (2010–2013 and 2013–2017), the Shanghai Tianma Radio Telescope (TMRT) can work well, with efficiencies better than 50% from 1.3 to 50.0 GHz, mainly benefiting from its low-noise cryogenic receivers and active surface system. Pulsars were chosen as important targets of research at the TMRT because of their important scientific and applied values. To meet the demands of pulsar-related observations, TMRT is equipped with some necessary backends, including a digital backend system (DIBAS) supporting normal pulsar observation modes, a real-time fast-radio-burst-monitoring backend, and baseband backends for very-long-baseline interferometry (VLBI) observations. Utilizing its high sensitivity and simultaneous dual-frequency observation capacity, a sequence of pulsar research endeavors has been undertaken, such as long-term pulsar timing, magnetar monitoring, multi-frequency (or high-frequency) observations, interstellar scintillation, pulsar VLBI, etc. In this paper, we give a short introduction about pulsar observation systems at the TMRT and briefly review the results obtained by these pulsar research projects. Full article

The residential block is the cognitive unit for residents to constitute urban imagery. As one of the most frequently used urban outdoor public spaces by residents, the thermal comfort of street canyons is an essential indicator for assessing sustainable and livable cities. The problem of the uncomfortable summer climate in the warm temperate zone of China has not been adequately studied. The study aims to analyze the influence of the building layout form of residential block units and block configuration on the outdoor summer thermal comfort of street canyons. Outdoor air temperature (T_a), mean radiant temperature (T_mrt), wind speed (V_a), and physiological equivalent temperature (PET) were simulated using ENVI-met. A new index, PET_ws, was introduced based on a statistical analysis of the PET index to assess the overall street canyon thermal comfort of the block. The results indicate that the number of rows of buildings in the building row layout has a more significant effect on the summer thermal comfort PET of street canyons than the number of columns in the warm temperate zone, especially on N–S-oriented streets. Reducing the number of rows can increase the overall thermal comfort PET_ws of street canyons by a maximum of 2.2%. The best choice for the number of building columns is two columns. Adopting different block configurations can increase the thermal comfort PET_ws of street canyons by up to 2.5%. An optimal block form has been created to improve the overall street canyon summer thermal comfort of the block. Full article