Search Results (2,246)

Urban parks are “cool islands” for mitigating urban heat, yet most snapshot-based assessments overlook intraday cooling dynamics and divergent mechanisms across park typologies. This study examines 52 parks in Wuhan, a humid city with routine park irrigation, using thermal data from Landsat 9 and ECOSTRESS across morning, noon, and nightfall. Through stepwise analysis and blue–green classification, we quantify diurnal cooling dynamics and their drivers. While previous studies have examined diurnal (within-day) cooling, multidimensional indicators, or scale effects separately, our contribution lies in establishing a multi-temporal assessment framework that integrates temporal dynamics with blue, green, and grey park typologies to reveal how cooling patterns diverge across blue, green, and grey parks throughout the day. Results show park cooling intensity (PCI) and gradient (PCG) peak at noon, while cooling area (PCA) remains stable. Elevated cooling efficiency (PCE) at nightfall is driven not by ecological cooling, but by the rapid thermal response of impervious surfaces with low thermal inertia. Area, greenspace proportion, and building height are primary drivers, shifting from scale dominance in the morning to vegetation and building at noon, with a preliminary transition range of approximately 14–16 hm² identified for this regime shift, though this finding warrants further validation with larger samples. Based on blue–green composition, parks are categorised as blue, green, or grey, with divergent cooling dynamics due to thermophysical properties. Blue parks cool steadily all day, green parks peak at noon, while grey parks’ elevated PCE at nightfall is an apparent thermal response, not ecological cooling. Typological heterogeneity weakens models that pool all parks together, as water storage, vegetation evapotranspiration, and impervious thermal response vary across types and cancel out when pooled. Findings show that single-time-phase or full averaging insufficiently captures park cooling dynamics, underscoring the value of considering both diurnal and typological variations in climate-adaptive planning for dense cities. Full article

Climate change and rapid urbanisation are intensifying the urban heat island effect, increasing thermal stress, degrading air quality, and leading to rising energy demand. Monitoring neighbourhood-scale heat requires Land Surface Temperature (LST) observations at fine spatial and temporal resolutions, yet satellite thermal products are limited by revisit frequency, acquisition time, and cloud cover. This study developed a novel approach integrating satellite-derived land cover characteristics with continuous contact-based temperature measurements from low-cost LoRaWAN sensors and geostatistical modelling to generate hourly LST maps at 10 m resolution. The technique provides communities with simpler, affordable methods for measuring heat islands and supporting mitigation strategies. Observations from 52 locations across Curtin University’s Bentley campus in Perth, Western Australia, were combined with land cover indices. Empirical Bayesian Kriging captured spatial and temporal urban heat patterns with a root mean square error of approximately 3 °C, representing a bias of near 1 °C. Predictions were consistent with Landsat-derived LST, revealing persistent heat retention over asphalt and cooler conditions associated with vegetation. Integrating satellite-derived predictors with ground measurements provides continuous fine-scale information to identify local heat hotspots and inform targeted mitigation. Unlike satellite data, these low-cost ground measurements could be collected with the help of urban practitioners, developers, and academic institutions. Full article

Makkah faces substantial heat-stress challenges associated with extreme temperatures, dense urban form, and the large numbers of pilgrims present during Hajj and Umrah, creating important public health concerns. Recent heat-related fatalities highlight the need for complementary strategies that address outdoor as well as indoor heat exposure, alongside conventional cooling approaches such as air conditioning. This article examines the potential role of nature-based and complementary engineered interventions in mitigating urban heat stress in Makkah, focusing on afforestation, urban greening, and the possible use of artificial water bodies, contingent on sustainable water management. Drawing on case studies and published evidence from arid and heat-prone regions, including China, Pakistan, Saudi Arabia, and the wider Middle East, we summarize reported cooling effects, implementation experience, and feasibility considerations and assess their potential relevance to Makkah. The perspective highlights critical challenges related to water scarcity, spatial constraints, ecological impacts, and governance, while proposing phased implementation pathways that could be evaluated incrementally. If carefully designed and integrated with urban planning and climate-adaptation strategies, nature-based and complementary interventions could potentially reduce human heat stress, reduce cooling demand, and strengthen climate resilience in Makkah. However, their effectiveness, water requirements, environmental impacts, and scalability require evaluation under Makkah-specific environmental and operational conditions. Full article

Rapid urbanization and increasing land surface temperatures (LSTs) have intensified urban heat stress in rapidly growing tropical megacities such as Dhaka. However, the coarse spatial resolution of conventional thermal satellite imagery limits the identification of fine-scale urban thermal variability required for climate-sensitive urban planning. This study develops a multi-sensor LST downscaling framework by integrating Landsat 8 thermal imagery with Sentinel-2-derived spectral indices within the Google Earth Engine (GEE) platform. A random forest regression model was developed using the normalized difference vegetation index, normalized difference built-up index, and modified normalized difference water index as predictors for statistical downscaling from the 30 m Landsat grid to a nominal 10 m grid. To preserve localized thermal heterogeneity and improve radiometric consistency, a bicubic residual correction approach was incorporated into the downscaling workflow. The resulting statistically downscaled LST estimate on a nominal 10 m grid was subsequently used to classify Urban Thermal Zones (UTZs) across Dhaka City. The results showed that LST was negatively associated with vegetation and water-related indices and positively associated with the built-up index. The statistically downscaled product provided a more spatially detailed representation of the Landsat-derived thermal field and delineated relative surface-temperature hotspots and cooler zones across the study area. High-temperature zones were primarily concentrated within densely built-up commercial and industrial areas, whereas comparatively lower temperatures were observed in vegetated and water-dominated regions. The proposed framework demonstrates a computationally efficient approach to spatially refining Landsat-derived LST in a data-constrained tropical megacity. The findings provide valuable spatial information for urban climate adaptation, heat mitigation planning, and climate-resilient urban development. Full article

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

Urban heat islands in densely built cities pose growing risks to public health and energy demand. Urban parks are key nature-based solutions, yet empirical evidence on park cool island (PCI) effects intensity and extent in compact cities remains limited. This study evaluated PCI for 12 pocket-to-medium/large urban parks in central Taipei, Taiwan. Land surface temperature (LST), mean radiant temperature (MRT), and effective temperature (ET) were measured along transects from park interiors into surrounding areas and linked to local environmental conditions. Parks showed PCI intensity in LST with an average cooling of 4.23 °C and an average cooling of 0.3 °C in ET; MRT cooling was weaker and spatially inconsistent. The cooling of LST extended to about 60 m beyond the park’s edges, while the cooling of ET reached approximately 150 m. In addition, the results show that shade and relative humidity are significant factors affecting PCI, and pervious pavement and wind speed also contribute to cooling LST and ET. The field observations provide evidence that urban parks contribute cooling effects and might reduce the risk of heat hazards. Full article

Waste from the aggregate processing industry has the potential to be used for value-added products. Its plastic properties and sinterability allow for the production of lightweight aggregates. This process can yield materials with high open porosity at various scales. This article presents the possibilities of obtaining lightweight aggregates from clay–silt fractions obtained by washing crushed dolomite aggregates. Aggregate formation was achieved using selected mechanical processing methods, such as dynamic granulation, sedimentation, crushing, and classification. Biomass was added to increase the aggregate’s porosity. The following instrumental techniques were used to assess the aggregate’s parameters: X-ray fluorescence (XRF) to obtain detailed information on the oxide composition of the tested raw materials; high-temperature microscopy (HSM) to determine the specific sintering temperature; and pH and conductivity meters to examine filtration solutions in direct contact with the aggregate. A key issue was to examine the microstructure of the produced aggregates after firing using scanning electron microscopy (SEM), Brunauer–Emmett–Teller method for measuring material surface area (BET), and X-ray diffraction (XRD) technique. The obtained results will allow for further research into developing a concept for the production of lightweight alkaline aggregates. The aggregates produced exhibit high water absorption (approximately 50%), a low bulk density of 0.82 g/cm³, and meso- (approximately 30–100 µm) and bioporosity (approximately 100–500 µm), which is beneficial for the proper development of plant roots and the absorption and release of water. This research contributes to the identification of resources that can be transformed into lightweight aggregates for urban greening, which is consistent with circular economy strategies and environmental protection. The specific mechanisms through which this research supports sustainable development are the reduction in landfill sites and the protection of natural resources. Furthermore, the aggregates produced can form part of blue-green urban infrastructure, which aims to manage rainwater and reduce the urban heat island effect. Full article

Surface urban heat island (SUHI) behavior in dryland cities can reverse sign when hot, bare peripheral surfaces exceed urban-core temperatures, yet long monthly records across contrasting climates remain scarce. This study reconstructs land surface temperature (LST) and standardized urban-core–periphery thermal contrasts for five Moroccan cities from 1995 to 2024 using Landsat, ERA5-Land, NDVI, and the annual MODIS MCD12Q1 land-cover product. The diagnostic analysis of SUHI and Urban Heat Sink (UHS) occurrence is explicitly separated from the forecasting component: SARIMA, Random Forest, XGBoost, and LSTM models predict monthly LST rather than UHI intensity. Tangier exhibits a persistent positive SUHI (mean: 4.6 °C; UHS frequency: 3.0%), whereas Béni Mellal, Ifrane, Laayoune, and Taza have negative mean contrasts of −1.4, −2.4, −1.0, and −0.7 °C, respectively; Ifrane records the highest UHS frequency (90.5%). No city shows a statistically significant monotonic UHI trend, and Sen’s slopes remain close to zero. Forecasting skill is city-dependent: SARIMA performs best in Ifrane and Tangier (R² = 0.94 and 0.93), while Random Forest performs best in Taza and Laayoune (R² = 0.90 and 0.79). Approximate 95% empirical uncertainty half-widths derived from held-out RMSE range from ±3.78 to ±15.48 °C, indicating substantial model- and city-specific uncertainty. The results support the hypothesis that local climate and peripheral land-cover context can outweigh urban fraction as controls on SUHI sign and amplitude. Generalization is limited by fixed reference distances, possible urbanization of the outer ring, clear-sky satellite sampling, the distinction between LST and air temperature, and the 36-month recursive forecasting chain used to display the 2026–2027 outlook. Full article

Urban blue and green spaces can alleviate extreme heat stress induced by global warming and urban heat islands, yet existing findings on their integrated cooling effects remain inconsistent. This study examined how the integrated cooling effects and relative cooling effectiveness of blue and green spaces differ with vegetation types and diurnal periods, based upon field measurements of two waterfront parks in subtropical Nanjing, China. Hourly air temperature was monitored at 15 sites with distinct blue–green–gray compositions within the two parks over 22 consecutive summer days. Results showed that both parks exhibited a cooling effect relative to the urban reference site (cooling frequency: 90.5% and 95.3%, respectively), whereas nocturnal warming emerged when the suburban meteorological station was used as the reference (warming frequency: 48.3% and 67.0%, respectively). The daytime air temperature was positively associated with gray-space proportions within 25–200 m buffers, whereas the nighttime air temperature was negatively correlated with green-space proportions within 200–500 m buffers. The integrated effect of blue–green spaces in the two parks was highly context-dependent: the tree-covered waterfronts provided sustained daytime cooling, whereas the grass-covered waterfronts cooled mainly at night; water proximity may suppress tree cooling during daytime, with no consistent influences observed for grasses. These observed patterns may offer preliminary empirical reference for climate-adaptive designs in similar subtropical waterfront settings. 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

Cities create their own local climate, and numerical weather models can reproduce it if given an accurate picture of the urban surface. The local climate zone (LCZ) framework classifies neighborhoods by building height, density, and materials and provides this information to fine-scale weather models. This approach has mostly been evaluated in warm seasons, leaving open how it performs in the cold, air-stagnant winters of high-latitude cities like Ulaanbaatar, Mongolia. We ran nine model versions over one cold week (22–29 February 2024) across three nested domains (12.5, 2.5, and 0.5 km) with LCZ data resolved to 100 m. Run 8 achieved the highest aggregate validation skill, whereas Run 9 was retained as the configuration most suitable for the LCZ-based analysis rather than as the best model overall. Run 9 reproduced near-surface temperature at the urban Bayanzurkh station (R = 0.89) and gave the smallest wind-speed error (1.5 m s⁻¹), while uniquely resolving the inter-class morphological contrasts required here. The dense urban core proved warmer than the non-urban area by 4.1 °C on average and up to 9.3 °C at night in the compact high-rise zone. Yet this warming barely relieves cold stress: the Universal Thermal Climate Index (UTCI) averaged −15.5 °C across the LCZ classes, within the strong-cold-stress range, with only the compact high-rise zone reaching a milder category. In the low-rise “ger districts”, wind speed rather than air temperature governs perceived cold, and compact high-rise form offers the strongest wind shelter. These findings provide a baseline for future scenario testing of winter thermal exposure in Ulaanbaatar. 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 heat islands (UHI) intensify as cities expand, exposing residents to elevated thermal stress and complicating urban climate adaptation planning. Existing satellite-based approaches to detecting surface urban heat islands (SUHI) typically rely on a single class of data and narrow temporal windows, limiting their ability to capture the full range of processes driving surface overheating. This study develops and evaluates a random forest model for SUHI detection in Warsaw, Poland, integrating two classical spectral indices (NDVI, NDBI) derived from Landsat 8/9 Collection 2 imagery with three land-cover probability layers (built-up, tree, water) from the Dynamic World deep-learning product, processed in Google Earth Engine. Both a multi-year summer median composite (2020–2025) and individual annual summer composites were used, the latter enabling a leave-one-year-out temporal validation. Heat island pixels were defined as those whose land surface temperature anomaly exceeded +3 °C relative to the study area mean, a local criterion rather than a city-versus-rural contrast. The model achieved high and stable performance (accuracy = 0.831, AUC = 0.910 on the test set; AUC = 0.907 ± 0.004 in five-fold cross-validation and 0.905 ± 0.018 in leave-one-year-out validation). An ablation analysis showed that combining the probability layers with the spectral indices clearly outperformed the indices alone (AUC = 0.852 vs. 0.905), whereas the additional gain over the Dynamic World layers alone remained within uncertainty. Vegetation-related predictors (NDVI and tree probability) contributed more to classification than built-up indicators. These results indicate that vegetation deficit, rather than built-up presence alone, is the primary driver of surface overheating in Warsaw and that the proposed open-data workflow offers municipalities a low-cost screening tool for identifying priority areas for climate adaptation and, thanks to its reliance solely on open data, can be adapted to other cities, subject to further validation. Full article

Warsaw experiences significant urban heat island (UHI) effects driven by low-albedo surfaces and urban geometry, which pose ongoing challenges for public health and climate adaptation. This study evaluates daytime SUHI intensity at satellite acquisition time across the entire city to provide a comparison of two acquisition dates during heatwaves. Utilizing Landsat 7 and Landsat 9 satellite imagery from July 2015 and July 2022, the research compares six distinct SUHII calculation methods, including spectral indices, statistical normalizations, and area-based temperature differences, as minimum SUHII values differed significantly between the two observations (shifting from approximately −13.8 °C to −7.7 °C). This indicates that suburban areas can become thermally similar to the city due to rapid land conversion and decreased evaporative cooling of vegetation during severe heat. Average intensities calculated via the SUHII 4 method reached 5.80 °C in 2015 and 2.07 °C in 2022. Under the criteria considered in this case study—interpretability, explicit physical units, treatment of water bodies, data requirements, and spatial consistency—SUHII 4 was the most suitable of the six tested formulations for the Warsaw analysis. Conversely, dimensionless spectral indices and purely statistical approaches are not recommended due to interpretative limitations. Full article