Search Results (907)

Canopy urban heat island (CUHI), defined as the air temperature difference between the urban near-surface atmosphere and surrounding rural areas, exhibits diurnal variability and affects urban thermal environments and well-being. However, the nonlinear effects of urban morphology on daytime and nighttime CUHI remain insufficiently understood. Taking the Yangtze River Delta (YRD) as the study area, this study integrates remote sensing, building morphology, and ground-based meteorological data to characterize urban morphology and canopy urban heat island intensity (CUHII). Extreme Gradient Boosting (XGBoost), SHapley Additive exPlanations (SHAP), and dependence plots were used to quantify and interpret nonlinear morphology–CUHII relationships. The models showed moderate explanatory ability, indicating that the selected morphology indicators explained only part of CUHII variability. Nighttime CUHII was stronger than daytime CUHII, with average values of 0.848 °C and 0.431 °C, respectively, and high-value areas concentrated in Shanghai, northern Zhejiang, and southern Jiangsu. During the daytime, the Aggregation Index (AI) was the most important selected morphology variable and was positively associated with CUHII, suggesting that compact built-up patterns may enhance heat accumulation by increasing heat absorption and limiting ventilation. At night, the Splitting Index (SPLIT) ranked first, with higher values generally associated with weaker CUHII, possibly reflecting greater spatial openness and reduced continuity of built-up surfaces. The nonlinear transition ranges of AI and SPLIT further reveal diurnal asymmetry in morphology–CUHII relationships. These findings support time-specific urban heat mitigation while avoiding attribution of overall CUHII variability solely to urban morphology. Full article

The study investigates the efficacy of various Urban Heat Island (UHI) mitigation measures within the United Nations Educational, Scientific and Cultural Organization UNESCO-listed historical center of Florence. Increasingly frequent and severe heatwaves during the summer season represent significant challenges for urban sustainability and public health in the outdoor urban environment. Using ENVI-met as a simulation tool, the research assesses the current microclimate conditions of a district within a historical center and simulates alternative mitigation scenarios. It quantifies the benefits in terms of microclimate characteristics (Potential Air Temperature-Ta and Mean Radiant Temperature-MRT) and human comfort indexes (Physiological Equivalent Temperature-PET and Universal Thermal Climate Index-UTCI). The proposed interventions include blue and green infrastructures as well as shading systems installed across the district. Current climate conditions are characterized by an average Ta of approximately 32 °C and MRT exceeding 59 °C; consequently, the analyzed area falls into the very strong heat stress category for both the calculated comfort indexes. All evaluated mitigation measures result in improving microclimate conditions as well as enhancing human thermal wellbeing within the outdoor environment. The most effective district-level intervention is the installation of shading fabrics, which reduces average Ta by 0.2 °C and MRT by up to 14 °C compared to the current scenario. Interventions tailored for the main square significantly reduce both UTCI and PET values, shifting the thermal stress from very strong to strong or even moderate. These findings highlight the potential of localized and tailored interventions to successfully integrate climate mitigation strategies within sensitive historic urban districts. Full article

Urban green infrastructure (UGI) serves as a core pillar of sustainable urban development, delivering multiple benefits including urban heat island mitigation, stormwater regulation, and health promotion. However, allergenic pollen released by urban vegetation represents a typical ecosystem disservice, creating a prominent sustainability trade-off between greening benefits and residents’ allergy risk. For a long time, research in this field has evolved along two largely independent lines: vegetation allergenic hazard assessment and atmospheric pollen exposure analysis. Marked disconnections persist in indicator systems, spatial scales, and outcome translation, and an integrated spatial assessment framework remains lacking. Based on a systematic review of 127 publications from the Web of Science Core Collection (2000~2025) using framework synthesis methods, this study constructs a hazard–exposure–risk–planning (HERP) framework for the spatial assessment of allergenic pollen risk in UGI. This paper systematically synthesizes the core indicators, technical approaches and inherent limitations of each framework layer and identifies five key barriers: inconsistent indicator definitions, lack of cross-validation between surface vegetation and atmospheric pollen data, missing population vulnerability layer, insufficient multi-scale coupling, and weak translation of research into planning practice. The proposed framework provides a potential comparable and reproducible standardized pathway for cross-regional allergenic risk assessment and offers methodological support for healthy urban planning that balances ecosystem services and residents’ respiratory health. Full article

High-solar-reflectivity cladding materials are widely promoted to reduce cooling demand and mitigate urban heat island effects. However, in cold and mixed climates, their overall energy and carbon performance remains uncertain due to potential winter heating penalties and embodied carbon trade-offs. This study presents a comparative evaluation of energy use, annual operational carbon emissions, and material-level embodied carbon for high-reflectivity cladding applied to commercial buildings across representative Canadian climate zones. Dynamic simulations were conducted in EnergyPlus using a standardized warehouse archetype in Montreal, Toronto, and Vancouver, representing cold continental, mixed continental, and marine climates. Roof and wall solar reflectivity (albedo) was varied from 0.2 (baseline) to 0.8 (high reflectivity), while other envelope properties remained constant. Increasing reflectivity reduced annual cooling demand by approximately 15% in Montreal and Toronto and 20% in Vancouver, with the largest reductions during peak summer periods. However, reduced winter solar heat gains produced heating penalties, increasing total annual energy use by 1% in Montreal, 0.5% in Toronto, and less than 0.5% in Vancouver. Operational greenhouse gas emissions were calculated by converting simulated annual electricity and natural gas use into CO₂-equivalent emissions using provincial grid emission factors and combustion factors consistent with Environment and Climate Change Canada reporting. The results demonstrate the strong influence of regional energy supply on operational carbon outcomes. A cradle-to-gate (A1–A3) life cycle assessment quantified embodied carbon of representative cladding materials using Environmental Product Declarations and North American databases. Embodied carbon varied considerably: product-specific steel cladding manufactured in low-carbon electricity regions showed global warming potential as low as 1.76 kg CO₂e/kg, compared with industry averages exceeding 2.4 kg CO₂e/kg. Rather than performing a complete whole-life carbon assessment, this study comparatively evaluates annual operational carbon emissions and material-level embodied carbon to improve understanding of the energy and carbon implications of high-solar-reflectivity cladding materials in representative Canadian climates. The results demonstrate that climate conditions, envelope thermal performance, regional energy supply, and manufacturing pathways influence the environmental performance of cool envelope strategies. Full article

Urban climate risks, particularly extreme heat and flooding, increasingly threaten public infrastructure in rapidly urbanizing regions. Public schools represent critical community assets, yet their spatial planning often overlooks the role of natural capital in mitigating environmental risks. This study examines the intersection of natural capital and urban design through a case study of public schools in the Mount Vernon District of Fairfax County, Virginia. Using cartographic modeling and spatial analysis, the study assesses school-site exposure to urban heat island effects and localized flood risks by integrating geospatial data on land cover, surface temperature, and hydrological conditions. Results indicate that all analyzed school sites exhibit notable vulnerability to both heat exposure and flooding. The findings highlight the importance of incorporating natural capital—such as expanded tree canopy, green infrastructure, and permeable surfaces—into school site planning to enhance climate resilience and environmental quality. Full article

High-precision urban vegetation mapping is essential for assessing carbon sink capacities, mitigating the urban heat island effect, and supporting sustainable development. Although deep learning and high-resolution remote sensing have advanced automated vegetation monitoring, existing models still face challenges when a common segmentation architecture is evaluated under different imaging geometries. In this study, Cityscapes and ISPRS Vaihingen are treated as two independent benchmarks representing perspective street-level imagery and orthographic aerial imagery, rather than as simultaneous cross-view inputs. “Background dominance” caused by perspective distortion and the “gridding artifacts” inherent in orthographic textures severely constrain segmentation accuracy across varying vegetation scales, particularly for small targets. To address these limitations, we propose a Scale-Aware Mixture of Experts (SA-MoE) architecture for fine-grained vegetation segmentation under two distinct imaging views, together with a scene-specific optimization strategy. The core SA-MoE framework consists of two main components. First, the spatial gating network uses a temperature polarization mechanism with τ = 0.5 to adjust the initial logit maps, sharpening expert-weight differences while preserving stable gradient propagation. Second, we use a heterogeneous expert group with five parallel branches: a pixel-level expert, three spatial experts with different dilation rates, and a global average-pooling expert. A dynamic pixel-level weighted fusion mechanism is then applied, decoupling feature extraction from receptive-field allocation. Furthermore, to address the heterogeneity of “hard samples” and “label noise” across the two benchmark settings, we introduce a scene-specific optimization strategy. Our findings show that the Focal-Dice (FD) loss is more suitable for perspective scenes with severe target imbalance and hard-to-classify vegetation targets, whereas the Cross-Entropy (CE) loss is more robust to boundary jitter in orthographic imagery. Comparative experiments on the Cityscapes (perspective view) and ISPRS Vaihingen (orthographic view) datasets reveal that SA-MoE achieves a highly competitive balance between computational efficiency and fine-grained segmentation, particularly in micro-target recall. Notably, the recall for extra-small (XS) scale targets in the aerial dataset improved by 3.21 percentage points compared to the second-best model. For the street-level dataset, our model achieved competitive global performance in terms of Overall Accuracy (OA), Precision, and F1-Score. However, we also observed a performance trade-off, where Transformer-based models maintained an advantage in preserving fine boundary details for these extra-small targets. In the routing analysis, we observed a pattern that we refer to as “receptive field inversion”, in which the model assigns lower weights to large-dilation experts for large canopy regions in orthophotos. We interpret this pattern as a plausible routing hypothesis. Overall, SA-MoE offers an efficient and adaptive solution for urban vegetation mapping under two imaging views. Full article

Urbanisation and climate change have intensified the Urban Heat Island (UHI) effect in European cities, increasing thermal stress and health risks, especially for vulnerable people. Nature-based Solutions (NbS), such as green infrastructures (GI), offer effective mitigation strategies. A notable example is the Horizon 2020 URBAN GreenUP project in Valladolid, Spain, where a green shade shelter infrastructure was installed and monitored between 2019 and 2022 to evaluate its cooling performance and its effects on temperature-based urban heat indicators through the use of Key Performance Indicators (KPIs). Local thermal conditions were monitored across two adjacent narrow streets—one with the green shade shelter and one as a control. The installation of the green shade shelter in Valladolid produced measurable thermal benefits. During summer peaks, it reduced ambient temperatures by approximately 0.9 °C, with daily maximum temperatures decreasing by 1.0–3.0 °C. In winter, daily minimum temperatures dropped by around 1.0 °C, while autumn saw an increase of 0.7 °C. Summer minimum temperatures varied, ranging from a 0.2 °C decrease in early summer to a 0.7 °C increase in late summer, with a 0.3 °C rise during peak summer in mid-July. The intervention also reduced the frequency and delayed the onset of days exceeding 35 °C and nights above 20 °C, although the delay in peak tropical nights was limited to seven days. These findings indicate that green shade shelters can contribute to improving street-level thermal conditions and reducing temperature-based heat exposure indicators in dense urban environments. Full article

To mitigate the health and environmental risks of urbanisation and the urban heat island effect, urban planning is shifting towards promoting active mobility. The success of these efforts largely depends on understanding people’s thermal comfort on the move, driving research towards the investigation of the complex interdependencies between microclimatic conditions and the real-time experiences of pedestrians and cyclists. This literature review aims to present the state of the art of research at the neighbourhood and street levels by analysing the methodological frameworks employed and the outcomes achieved. The paper adopts a thematic clustering approach, grouping the articles on the basis of their research objectives, methodologies and the relationships between active mobility and comfort. The literature review highlights a shift from static to dynamic comfort assessments and a focus on active travel as a continuous experience rather than the sum of stationary moments. The primary findings include the consolidation of the thermal walk methodology and the emergence of cumulative stress indices. Evidence from heat stress contexts suggests that pedestrians prefer thermal diversity, which causes thermal alliesthesia, over monotonous conditions. The research highlights the role of heat stress as a barrier to walkability in hot and temperate climates, causing route deviations and lower walking speeds, with the opposite pattern in severely cold settings. This review identifies several research gaps, including a lack of standardised dynamic assessment methods, low generalisability and transferability of the results, and insufficient investigation of cyclists’ dynamic comfort compared with that of pedestrians. Full article

Urban Heat Island (UHI) effects are increasingly acknowledged as a critical urban climate challenge with far-reaching consequences for human health and overall well-being. However, the conceptual structure, temporal evolution, and intellectual landscape of studies examining the relationships between UHI and human well-being remain fragmented, thereby constraining the development of integrated knowledge frameworks needed to guide future research, urban adaptation strategies, and evidence-based policy interventions. To this end, a total of 4857 studies were retrieved from the Scopus and Web of Science databases and screened following the PRISMA guidelines. These studies were then analyzed using Bibliometrix and VOSviewer. The results reveal a rapid and exponential growth in scientific output, particularly after 2010, with the output reaching its highest level in recent years. These outputs were shaped mostly in China and the United States with a well-established international collaboration network, while the Global South remain significantly underrepresented in scientific productions. We also found that studies are primarily structured around four dominant research clusters: urban heat island, thermal comfort, land surface temperature, and climate change. Furthermore, early studies predominantly focused on urban surface properties and built-environment characteristics, while recent research has increasingly shifted toward human health impacts, thermal stress, heat vulnerability, and well-being. Emerging research directions further highlight growing interest in nature-based solutions for mitigating UHI effects, alongside the application of advanced technologies such as machine learning and remote sensing for high-resolution urban climate assessment. Overall, our findings indicate a transition toward a more integrated urban climate–health–well-being research framework, while simultaneously revealing persistent geographical and conceptual gaps, particularly across the Global South. We therefore advocate for increased empirical research, stronger international collaboration, and context-specific urban adaptation strategies to better safeguard human well-being under intensifying urban heat conditions. Full article

Green façade applications are among the visible strategies to mitigate Canopy Urban Heat Islands (CUHIs) and improve thermal comfort, particularly in hot arid climates. However, their combined effectiveness at the urban scale, particularly with respect to urban canyon geometry, remains underexplored. This study evaluates the cooling efficiency of green façades and their relationship with height-to-width (H/W) ratios in the hot arid climate of Tehran, Iran. Urban canyons with varying geometries and façade conditions are simulated using ENVI-met 5.1 to assess impacts on air temperature and the Universal Thermal Climate Index (UTCI). Results indicate that urban canyon geometry, particularly higher H/W ratios, plays a dominant role in reducing CUHI intensity and improving outdoor thermal comfort, especially during summer, when deeper canyons show lower air temperature and UTCI values. The addition of green façades further enhances this cooling effect, most significantly in deeper canyon configurations. In contrast, winter conditions show minimal sensitivity to both geometry and façade greening, with only minor variations observed. Overall, the study highlights the importance of integrating urban form and vegetation strategies, demonstrating that the effectiveness of green façades is strongly influenced by canyon geometry and seasonal conditions, providing insights for climate-responsive, geometry-sensitive urban design. Full article

Rising global temperatures and more frequent heat waves pose a growing threat to public health, particularly among older adults. Age-related declines in thermoregulatory capacity such as reduced sweating, impaired vasodilation, and diminished hypothalamic responsiveness make it more difficult to cope with elevated nighttime temperatures. These thermal challenges disrupt sleep by prolonging sleep onset, fragmenting slow-wave and REM sleep, and suppressing melatonin secretion. Importantly, sex-related differences in thermoregulatory aging—particularly menopause-associated vasomotor instability in women and testosterone-related autonomic changes in men—further modulate individual vulnerability to heat-induced sleep disruption. Beyond sleep, heat-induced stress affects metabolic, cardiovascular, and immune systems, promoting insulin resistance, endothelial dysfunction, sympathetic overactivation, and chronic inflammation. Socioeconomic disparities, urban heat island exposure, and differential access to cooling infrastructure function as critical environmental modifiers that amplify biological vulnerability, particularly in disadvantaged older populations. This narrative review aims to synthesize current knowledge on the specific thermoregulatory mechanisms of sleep disruption induced by heat stress in older adults. Understanding these interactions is crucial for developing effective interventions, including environmental cooling, circadian-aligned behaviors, and targeted public health strategies, to mitigate the compounded risks of heat exposure and preserve healthy sleep in aging populations. However, many proposed mechanistic pathways are primarily derived from animal models, and controlled human studies specifically targeting heat-exposed older adults remain scarce. Full article

Rapid urbanization has significantly altered urban landscape composition and configuration, making it a key driver exacerbating the urban heat island (UHI) effect. As a rapidly expanding inland city in Central China, Zhengzhou is highly sensitive to changes in landscape composition and spatial configuration. Therefore, clarifying the nonlinear relationship between landscape patterns and the urban thermal environment is of great significance for sustainable urban planning and thermal environment regulation. Taking the main urban area of Zhengzhou as the study area, this paper retrieves land surface temperature (LST) using the radiative transfer equation method based on Landsat 8 remote sensing images from August 2015 to August 2024, and constructs the surface urban heat island intensity (SUHII) index. By integrating multi-dimensional landscape pattern indices, the XGBoost machine learning model, and the SHAP interpretability method, this study systematically analyzes the nonlinear response mechanisms of landscape composition and configuration to SUHII, key regulatory thresholds, and their changes between 2015 and 2024. The results show that: (1) The SUHII in Zhengzhou was substantially higher in 2024 than in 2015. The area proportions of strong and extremely strong heat islands were higher in 2024 (26.16% and 2.34%) than in 2015 (2.22% and 0.12%), and the thermal environment differed between 2015 and 2024, shifting from a localized patch pattern to a more continuously expanding pattern. (2) Landscape area-related indices are the key factors. The areas of green space and water bodies, along with the landscape diversity index, show significant negative correlations, while built-up area and aggregation index show significant positive correlations. (3) SHAP feature importance indicates that water body area is the primary cooling factor, whereas built-up area is the primary warming factor, jointly dominating the spatial pattern of the thermal environment in Zhengzhou. (4) Landscape composition and configuration exhibit significant nonlinear responses to SUHII with region-specific thresholds, and these thresholds were higher/lower in 2024 than in 2015, suggesting a possible association with urban expansion. Specifically, stable cooling effects occurred when the water body area exceeded 3.5 km² in 2015, with the threshold rising to 4.2 km² in 2024. The warming threshold for built-up area decreased from 18.8 km² to 8.5 km², suggesting a higher sensitivity of the thermal environment to built-up area expansion in 2024 compared to 2015, characterized by a regulation pattern of “dominant scale effect and weakened configuration effect”. This study identifies thresholds specific to Zhengzhou’s main urban area at two time points (2015 and 2024), providing quantitative support and scientific basis for blue–green space optimization, precise heat island mitigation, and territorial spatial planning in Zhengzhou. These findings are based on a comparison of two time points (2015 and 2024) and do not directly capture continuous temporal dynamics. Full article

Against the backdrop of rapid urbanization and climate warming, the urban heat island (UHI) effect has severely affected ecological security and public health. Existing studies have often focused on single-city analyses or large-sample averages, with insufficient attention to the nonlinear driving mechanisms of UHI under different hydrothermal contexts. This study selects Wuhan and Xi’an as representative cities, constructing an explainable machine learning framework to interpret and compare UHI intensity across feature importance, nonlinear responses, factor interactions, and spatial differentiation. The results show that, in Wuhan, the top five factors contribute 62.4%, reflecting a composite dominance of ecology, spatial morphology, location, and human activities. In Xi’an, the top five factors contribute 72.0%, indicating a more concentrated dominant structure. Nonlinear responses reveal that key factors like NDVI have distinct effect thresholds and mechanisms in the two cities. Spatially, Wuhan displays a continuous gradient pattern characterized by center-promoting and peripheral-suppressing effects, whereas Xi’an presents a block-like mosaic structure composed of multiple juxtaposed districts. These differences suggest that UHI mitigation should move beyond a uniform control model and instead adopt climate-sensitive strategies that account for the dominant factor combinations, response thresholds, and spatial organization of each city. The proposed framework and findings provide scientific support for understanding UHI mechanisms under different hydrothermal contexts and offer targeted implications for thermal environment regulation and spatial planning in cities with similar climatic and environmental characteristics. Full article

Land-intensive high-density residential development often comes at the cost of compromised natural ventilation efficiency and reduced capacity for urban heat island mitigation, and such trade-offs are particularly pronounced in valley cities due to topographical constraints. Taking Lanzhou Yineng Huanghe Jiayuan as a case study, this research constructs a “Source-Flow-Sink” landscape ventilation efficiency measurement framework based on circuit theory and CFD numerical simulation. Combined with correlation analysis and multiple linear regression, the coupling mechanism between spatial morphology and ventilation efficiency is examined. The results indicate that: (1) The study area exhibits a ventilation pattern characterized by “Source” in the north, “Flow” in the middle, and “Sink” in the south; (2) The wind speed ratio in the residential area shows a highly significant negative correlation with vegetation coverage, and a significant negative correlation with building dispersion and average building height; (3) Based on three configuration modes of “Source-Flow-Sink”, differentiated micro-renewal strategies that do not alter the core indicators of land intensification are proposed, providing a scientific basis for climate-adaptive design of intensive residential areas in valley cities. Full article

This paper focuses on the analysis of long-term land surface temperature (LST) dynamics and land-use changes in the city of Košice, Slovakia, during the period 1985–2025. The analysis is based on multi-temporal Landsat satellite imagery processed within a geographic information system (GIS) environment. Non-parametric statistical methods, including the Mann–Kendall trend test and the Theil–Sen slope estimator, were applied at the pixel level to identify the direction, magnitude, and statistical significance of long-term trends. Land-use changes were evaluated using CORINE Land Cover data together with the NDVI and NDBI spectral indices. The results revealed a statistically significant increase in land surface temperature across almost the entire urban area, with the mean LST increasing by 5.83 °C between 1985 and 2025. The analysis also confirmed a strong positive correlation between built-up areas and LST values, whereas vegetation cover exhibited a significant cooling effect represented by a strong negative correlation with surface temperature. Spatial analysis identified pronounced warming hotspots concentrated mainly in industrial and newly urbanized areas, while vegetation-stabilized zones showed lower warming intensity or localized cooling trends. The findings highlight the dominant influence of urbanization processes on the city’s thermal regime and emphasize the importance of urban vegetation as a key adaptation element for mitigating the surface urban heat island effect. The study also illustrates the added value of integrating remote sensing data, GIS tools, and pixel-based trend analysis in the assessment of long-term changes in the urban thermal environment of medium-sized Central European cities. The results provide a spatial basis for climate adaptation planning and future assessments of urban thermal comfort and environmental quality. Full article