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The urban heat island (UHI) effect refers to the phenomenon where central urban areas exhibit higher temperatures than surrounding suburban areas due to concentrated human activities and building structures. This effect significantly impacts urban environments, the quality of life of residents, and energy demands. With the continuous advancement of urbanization, the UHI effect is becoming increasingly severe, making it a focal point in the fields of urban planning and architectural design. However, existing studies often rely on macro-climatic data and lack a thorough analysis of the thermodynamic properties at the urban micro-scale, failing to fully reveal the mechanism behind the impact of architectural layout on the UHI effect. This study begins with a thermodynamic perspective, exploring the changes in thermal stability of the boundary layer in different urban areas under the UHI effect through the heat flux equation. It analyzes the impact of different architectural layouts on the urban thermal environment. The research demonstrates that urban heating disturbances and the average state induced by the UHI effect have distinct regional characteristics in terms of boundary layer thermal stability. Furthermore, by utilizing spatial autocorrelation analysis and the principle of hot and cold spot identification, this paper deeply investigates the spatial autocorrelation and its evolution in urban architectural layouts, assessing the potential of architectural layouts in mitigating the UHI effect. These findings provide new perspectives and tools for urban planning, contributing to the optimization of the urban thermal environment, enhanced energy efficiency, and improved resident comfort. [ABSTRACT FROM AUTHOR]

The outdoor thermal comfort of an urban area gets affected by different aspects, such as the urban materials and urban morphology (building-canopy & trees-canopy). This paper aims to investigate the effect of such different aspects on urban surface thermal performance using in-situ measurements and to predict the same by coupling a simple single-layer urban canopy model (SLUCM) with a surface energy balance model (SEBM). The asphalt road is the hottest (45°C), with a heating rate of 5.26°C/hour during the day. The building canopy shading creates a 2.8°C between the air temperatures. The results indicate the importance of green areas for cooling urban spaces due to their lower warming and surface shading from tree canopy as 7.3°C of the temperature difference between surface and air temperature reduced to 3.2°C. Averaging all the analysis, the model evaluates the surface temperature with R2 = 0.8824, mean bias = 1.86°C, MAE = 2.59°C, and RMSE = 5.13°C. [ABSTRACT FROM AUTHOR]

Increasingly high temperatures in Southern California often result in an unequal experience to heat, with lower-income communities and communities of color disproportionately facing the negative effects of heat. Although public parks offer a prime avenue for heat mitigation, features of parks are not equally distributed. This study focuses on the central Los Angeles neighborhood of Westlake and analyzes its two largest parks: MacArthur and Lafayette park. This study finds these parks are located in areas of relatively low income, with high population density and renter-occupied housing. The project also incorporates how the history of the parks and the features available within the space, such as tree canopy cover, bodies of water, and recreational offerings can potentially impact the parks’ heat-mitigating effects. Through demographic research, archival newspaper photographs, geospatial mapping and analysis, and references to current studies on heat and urban parks, this study aims to produce a narrative on the heat-mitigating effects of these parks within the greater Westlake neighborhood.

Increasing urbanization and climate change challenges are leading to relevant environmental, economic and social pressures on European cities. These include increasing flood hazards and the urban heat island (UHI) effect. Nature-Based Solutions (NBS) are increasingly recognized within strategies to provide multiple ecosystem services to mitigate existing risks and pressures, as well as to make cities more resilient and livable. Although being increasingly addressed within the literature, NBS implementation on the ground still faces many technical and financial barriers. This paper aims to test the potential of selected NBS in mitigating the effects of identified climate change risks, i.e., the UHI effect and urban floods, in the Turin urban area (north-western Italy). Four different intervention NBS-based scenarios are developed. The supply of ecosystem services by NBS in each scenario is assessed using InVEST models and the effectiveness of NBS investments is analyzed by calculating and comparing the associated costs and benefits. Different results in terms of effectiveness and economic viability are observed for each scenario and each NBS. Flood risk mitigation oriented NBS seem to have the most impact, in particular forested green areas and retention ponds. The results are relevant to suggest policy mix strategies to embed NBS in city planning. [ABSTRACT FROM AUTHOR]

With the fast urbanization, urban heat island (UHI) effect is becoming more and more pronounced. Identify and evaluate the temporal-spatial variations and the driving factors that are in urgent need to alleviate a series of problems caused by heat island. Changchun of Jilin province is located in northeast China, using multiperiod satellites images and other ancillary data to invert the surface temperature and acquire the surface land cover classification, then it analyzed the temporal-spatial variation of UHI effect and relation between urban developments. The temporal variations of UHI effects based on air temperature (AT) showed: the UHI was strong at night and weak in daytime; the UHI was strong in autumn and winter and weak in spring and summer; the UHI effect increased rapidly before 2015 and decreased after 2015. The spatial variations of UHI based on land surface temperature (LST) effected: The area of higher temperature zone increased, while the area of other areas declined. The strength order of the UHI effect for different land surface covering types was: building land> grassland> woodland>water area. This meant how to layout urban land use types were important, reasonable urban land planning was necessary for urban sustainable development. This study provided an important basis for counteracting the UHI effect and promoting the construction of an eco-city.

Figuring out the action mechanism of carbon emission trend on the influencing factors of urban thermal environment from the perspective of transportation energy consumption is of great significance for transforming citizens’ means of transportation and promoting sustainable development of urban environment. However, existing studies on urban thermal environment generally focus on the quantification of urban landscape forms, the correlation analysis, or the analysis of relative importance, few of them have concerned about the action mechanism of fluid flow, heat transfer, pollutant diffusion and other process parameters on the Urban Heat Island (UHI) effect with both transportation energy consumption and carbon emission trend taken into consideration. For this reason, this paper gave the spatial structure of urban thermal environment, constructed fluid flow control equation, heat transfer control equation, pollutant diffusion control equation, and turbulence model for the urban thermal environment; then, it quantitatively analyzed the UHI intensity and air pollutant concentration, aiming to alleviate the UHI effect under the influence of transportation energy consumption and carbon emission trend. At last, this paper used experimental results to verify the effectiveness of the constructed model and gave the analysis results of thermal environment in the target city. [ABSTRACT FROM AUTHOR]

In the process of studying the spatiotemporal cause mechanism of urban heat island (UHI) effects, the classification method used will directly affect the robustness of urban surface heat classification. Applying five commonly used standard classification methods, we divided Beijing's urban surface temperatures in the summer of 2020 into five levels. We then compared the reliability of the five classification methods in resolving 12-period data and the seasonal average temperature in UHI patches, based on two indicators: UHI area and UHI intensity. The actual land-use composition of the UHI patches obtained with traditional methods was applied to confirm our results. The mean-standard deviation method and natural breaks (Jenks) method were more robust with regard to UHI classification and 12-period data reliability. For the UHI area index, the mean-standard deviation method produced the smallest total area of UHI patches for summer days and nights. For the UHI intensity index, the quantile method, mean-standard deviation method, and natural breaks (Jenks) method were associated with smaller errors. Considering the composition of land-use types in UHI patches, the mean-standard deviation method, and natural breaks (Jenks) method were more rigorous. Thus, our research results provide guidance for method selection when classifying UHI.

Green buildings are an important constituent part of the urban ecosystem; they act as an adjuster of temperature and humidity of the environment in cities, and can effectively alleviate the Urban Heat Island (UHI) effect. Existing studies on the UHI effect generally ignored the local information in the changes of the UHI effect, and the impact of the optimization of green building distribution on the UHI effect hadn't been taken into consideration. To fill in this research gap, this paper aims to study the optimization of the distribution of green buildings based on the UHI effect. At first, this paper adopted a highprecision radiative transfer model to invert the temperature of earth surface in cities, and accurately calculate the UHI effect. Then, this paper analyzed the changes in the UHI effect caused by the optimization of the distribution of green buildings and the response of human activities, and used the time variation law of the single pixels of green buildings to reflect the spatial variation law of the UHI effect. At last, experimental results gave the optimization results of the distribution of green buildings based on the UHI effect. [ABSTRACT FROM AUTHOR]

Increasing urbanization and climate change challenges are leading to relevant environmental, economic and social pressures on European cities. These include increasing flood hazards and the urban heat island (UHI) effect. Nature-Based Solutions (NBS) are increasingly recognized within strategies to provide multiple ecosystem services to mitigate existing risks and pressures, as well as to make cities more resilient and livable. Although being increasingly addressed within the literature, NBS implementation on the ground still faces many technical and financial barriers. This paper aims to test the potential of selected NBS in mitigating the effects of identified climate change risks, i.e., the UHI effect and urban floods, in the Turin urban area (north-western Italy). Four different intervention NBS-based scenarios are developed. The supply of ecosystem services by NBS in each scenario is assessed using InVEST models and the effectiveness of NBS investments is analyzed by calculating and comparing the associated costs and benefits. Different results in terms of effectiveness and economic viability are observed for each scenario and each NBS. Flood risk mitigation oriented NBS seem to have the most impact, in particular forested green areas and retention ponds. The results are relevant to suggest policy mix strategies to embed NBS in city planning.

Concrete has been extensively used in the development of urban infrastructure works. However, it has the tendency to absorb solar radiations, and these radiations are released back into the air in the form of heat energy. Dense concentration of infrastructures releases more heat, causing urban heat island (UHI) effect in which the ambient temperature of the urban areas rises slightly than the surrounding areas. Tropical countries which have a hot climate throughout the year are more affected by the UHI effect. Therefore, thermal insulating materials need to be introduced in the field of concrete construction. Foamed concrete, which has air voids in its matrix, is a potential thermal insulating material. But due to reduced density, it, however, achieves lower strength. Polypropylene (PP) fibres are used to reinforce the foamed concrete and improve its compressive and tensile strengths. In this study, three different densities, 1400, 1600 and 1800 kg/m3, were cast, and 0.8% PP fibres were added. The thermo-mechanical properties were investigated in terms of thermal conductivity, surface temperature, compressive and tensile strengths with and without the addition of PP fibres. Based on the findings, the addition of PP fibres gained more strength and reduced thermal conductivity in the lower densities of foamed concrete. In contrast, it had an opposite impact on 1800 kg/m3 density. The addition of PP fibres also indicated that it could reduce the surface temperature of higher-density foamed concrete compared to lower densities. [ABSTRACT FROM AUTHOR]

The construction of concentrated infrastructures due to rapid urbanization has given rise to urban heat island (UHI) phenomenon which causes temperature of urban areas to significantly increase compared to its adjacent cooler rural areas. The absorption of heat in the form of solar radiation by infrastructures is the main contributor to UHI, which results in the rise in the ambient temperature at night. This has forced the construction industry to focus on thermal insulating building materials such as foamed concrete. Air voids in the matrix of foamed concrete allow it to reduce the thermal conductivity and dry density; however, due to its reduced density, foamed concrete is prone to microcracking which results in loss of strength. To counteract the development and propagation of microcracks, polypropylene (PP) fibres are used to reinforce the foamed concrete. Therefore, in this study, foamed concrete of density 1600 kg/m3 was reinforced using PP fibres in three percentages, 0.20%, 0.25% and 0.30%. Thermal performance, in terms of thermal conductivity and surface temperature, was conducted as well as the compressive and tensile strength was determined. It was observed that the PP fibres not only enhanced the strength but also significantly lowered the thermal conductivity and absorbed less heat. [ABSTRACT FROM AUTHOR]

In recent decades, urban greening has been conceptualized, and subsequently marketed, as a way of making cities more sustainable. Urban greening has been actualized in large global cities, regional centers, and also in many cities in the Global South, where it has been touted as a potential solution to the urban heat island (UHI) effect and as a way of reducing carbon dioxide (CO2) emissions. This involves planting street trees and installing curbside gardens, bioswales, green walls, green roofs, and the redevelopment of former industrial zones into urban parklands. This paper questions the assumption that this “greening” of the city must necessarily lead to positive environmental impacts. While such infrastructure itself might be constructed with environmental principles in mind, wider questions concerning the production of such landscapes, and the consumption-orientated lifestyles of those who inhabit these urban landscapes, are seldom considered. Moreover, green aesthetics and environmental sustainability are not always as mutually inclusive as the concepts might suggest, as aesthetics are often a dominating influence in the process of planning green urban environments. This review reorients the focus on the way in which the UHI effect and CO2 emissions have been framed by utilizing Foucault's (1980) “regimes of truth,” where environmental issues are contextualized within the “colonised lifeworld” of free-market forces. This review suggests that for sustainability to be achieved in urban contexts, the process of urban greening must move beyond quick techno-fixes through engagement in the co-production of knowledge.

This paper aims to disclose the impact of urban high-speed rail (HSR) construction on the urban heat island (UHI) effect and predict the UHI effect in future. For this purpose, the radiation transmission method was adopted to investigate the UHI effect in south-eastern China's Nanchang city, and forecasted the UHI effect from 2018 to 2025 in Nanchang via longitudinal greyscale simulation. The research results show that: the surface temperature is closely related to the urban HSR construction; the maximum surface temperature increases with the built-up area of the HSR; different factors have different effects on the UHI effect, among which population is the leading influencing factor; the mean temperature in 2018~2025 indicates the HSR construction in Nanchang has a severe HSR effect. The research finding shed new light on the studies of UHI effect and its influencing factors. [ABSTRACT FROM AUTHOR]

• An urban water body evaporation (E) model that considers anthropogenic heat flux is proposed; • E in the main urban area (E u) alleviates the urban heat island (UHI) effect, while E in the suburbs area (E s) aggravates the UHI effect; • The upward trend of E u is higher than E s during 1986–2015, indicating the mitigation capability of E to UHI effect is enhanced with urbanization; • The cooling effect of E to UHI mainly depends on the volume and size of the water body in the main urban area; • The mitigation of the urban UHI effect will benefit more from urban E under the future climate change. The urban heat island (UHI) effect is accelerated with urbanization and climate change, thus threatening human survival. The evaporation from water body (E) takes away energy through heat absorption process, thereby effectively play a role in temperature cooling and UHI effect alleviation. However, the response of UHI effect to urban E is still lacks study in the current UHI research. To address this issue, this work proposes a customized water body evaporation model in urban areas. The newly developed urban E model considers the contribution of anthropogenic heat flux (AHF) to the energy balance in urban areas. Meanwhile, AHF is also used to enhance the simulation of the water heat storage change (G) for urban water body. Validation results in two megacities in China indicate that the developed urban E model which considered AHF in the energy balance equation significantly improves the simulation performance of E in the main urban area (the root mean square error (RMSE) significantly decreased by 26.6 W/m2 compared with the original Penman formula for E in the main urban area (E u) simulation). The consideration of AHF in the G determination improves the simulation performance of E in the deep water body (the RMSE significantly decreased by 33.3 W/m2 compared to the AHF-Penman model that do not considering G for E simulation in deep water body). The developed urban E model is further used to evaluate the response of UHI to the E u and E in the suburban area (E s). It is found that E u effectively alleviates UHI, while E s aggravate UHI. Moreover, the cooling effect of E in the main urban areas (ΔT au) and suburbs (ΔT as) are increased with urbanization. The increasing rate of ΔT au is higher than ΔT as , indicate the contribution of evaporation cooling to the UHI alleviation is increased with urbanization. Further analysis demonstrate the urbanization process can explain approximately 90% of the enhanced ability of E to mitigate the UHI effect. Correlation analysis shows that the mitigation capability of E to UHI effect is mainly controlled by the volume and surface size of water body. Finally, future climate scenario-based urban E forecast confirms that ΔT au and ΔT as will continue to rise with climate change. The average increasing rate are 0.018 °C/year and 0.013 °C/year for ΔT au and ΔT as , respectively, under the three representative concentration pathways. The increasing rate of ΔT au is larger than ΔT as , suggesting the mitigation of the UHI effect will benefit more from urban E under the future climate change. Generally, our findings highlight that the mitigation of the UHI effect mainly benefits from E in the main urban area rather than E in the suburban area. This study gains insight into E in urban areas, including its algorithm, interaction with the UHI effect, and responses to urbanization and climate change. The results of this study provide a good scientific basis for urban landscape water planning. [ABSTRACT FROM AUTHOR]

Beijing has suffered from a rapid development of urbanization in recent years especially since the successful bidding of the 2008 Olympic Games on July 13, 2001 in Moscow. To identify the influence of this paramount sporting event on development of the urban heat island (UHI) effect, this paper examined the spatial expansion of the urban size and UHI effect in Beijing from the years 1999, 2004 to 2008 and 2008 to 2013 using Landsat satellite images. These time spans indicated the process of urbanization in Beijing before and after hosting the 2008 Olympic Games. A new method was proposed to delineate the whole urban boundaries in Beijing governmental area by combining the Remote Sensing (RS) and Geographical information Science (GIS) technologies. The spatial expansion intensity and directions both for urban size and UHI effect were computed and analyzed. By 2013, the urban size of Beijing expanded to more than twice its size in 2008. The sprawl directions for the urban size and the areas with a severe UHI effect were the same, whereas the areas with a severe UHI effect were not enlarged with the increasing urban size. This indicated that the urban development in Beijing after hosting the games was more reasonable which makes the Beijing city be more livable. Statistically, the UHI effect was mitigated when the ratio of areas with water-pervious surfaces to the whole urban region was more than 35%. The urban thermal environment has been improved by increasing the areas of the water-pervious surfaces since hosting the 2008 Beijing Olympic Games. [ABSTRACT FROM AUTHOR]

In recent decades, urban greening has been conceptualized, and subsequently marketed, as a way of making cities more sustainable. Urban greening has been actualized in large global cities, regional centers, and also in many cities in the Global South, where it has been touted as a potential solution to the urban heat island (UHI) effect and as a way of reducing carbon dioxide (CO2) emissions. This involves planting street trees and installing curbside gardens, bioswales, green walls, green roofs, and the redevelopment of former industrial zones into urban parklands. This paper questions the assumption that this "greening" of the city must necessarily lead to positive environmental impacts. While such infrastructure itself might be constructed with environmental principles in mind, wider questions concerning the production of such landscapes, and the consumption-orientated lifestyles of those who inhabit these urban landscapes, are seldom considered. Moreover, green aesthetics and environmental sustainability are not always as mutually inclusive as the concepts might suggest, as aesthetics are often a dominating influence in the process of planning green urban environments. This review reorients the focus on the way in which the UHI effect and CO2 emissions have been framed by utilizing Foucault's (1980) "regimes of truth," where environmental issues are contextualized within the "colonised lifeworld" of free-market forces. This review suggests that for sustainability to be achieved in urban contexts, the process of urban greening must move beyond quick techno-fixes through engagement in the co-production of knowledge. [ABSTRACT FROM AUTHOR]

Abstract: Buildings impact the environment in many ways as a result of both their energy use and material consumption. In urban areas, the emission of greenhouse gases and the creation of microclimates are among their most prominent impacts so the adoption of building design strategies and materials that address both these issues will lead to significant reductions in a building''s overall environmental impact. This report documents the energy savings and surface temperature reduction achieved by replacing an existing commercial building''s flat roof with a more reflective ‘cool roof’ surface material. The research methodology gathered data on-site (surface temperatures and reflectivity) and used this in conjunction with the as-built drawings to construct a building energy simulation model. A 20-year cost benefit analysis (CBA) was conducted to determine the return on investment (ROI) for the new cool roof construction based on the energy simulation results. The results of the EnergyPlus™ simulation modeling revealed that reductions of 1.3–1.9% and 2.6–3.8% of the total monthly electricity consumption can be achieved from the 50% cool roof replacement already implemented and a future 100% roof replacement, respectively. This corresponds to a saving of approximately $22,000 per year in energy costs at current prices and a consequent 9-year payback period for the added cost of installing the 100% cool roof. The environmental benefits associated with these electricity savings, particularly the reductions in environmental damage and peak-time electricity demand, represent the indirect benefits of the cool roof system. [Copyright &y& Elsevier]

• Based on the spatio-temporal LCZ dynamics to analyze the expansion trend of urban regional levels. • Using mean value and standard deviation to examine the spatial differentials of LSTs, and revealed regardless of the temporal variation of the actual LST values. • Using profile analyze of urban spatial morphology gradience to investigate the impacts on the LCZs with LSTs between urban and natural areas. The concept of Local Climate Zone (LCZ) classification scheme is an effective tool for quantifying the Urban Heat Island (UHI) effect. However, previous studies of the thermal environment using LCZs mainly focused on the meso‑ to-micro-scale or a single time, and the changes in the regional thermal environment were less considered. Thus, we selected the Xi'an urban spatial agglomeration and used remote sensing images from 2008, 2013, and 2019 to determine the spatial and temporal variations in the thermal environment for statistical analysis and contrast. The results confirmed that: (1) The proportions of low-rise types decreased significantly, and the land use for agglomerations and compacts shows an upward trend. (2) The built-up LCZs had higher land surface temperatures (LST), LCZ 10 (heavy industry) was the highest in all years. (3) The LCZs with LCZ A (dense trees), and LCZ G (water) were associated with slightly lower LSTs, and they helped to cool the city. (4) The LSTs tended to increase from natural to urban areas, before gradually decreasing with distance from the city center to rural areas. These findings may provide reference values for quantitative studies of LCZ classification maps and analyzing dynamic changes in urban surface thermal environments, thereby facilitating the UHI analysis and climate-adapted urban planning. [ABSTRACT FROM AUTHOR]

• Graphene based cement composite is prepared to improve building environment. • Electrical conductivity of 16.2 Scm−1 is measured with 15 wt% GNP inclusions. • Seebeck coefficient of 34 µVK−1 is measured with 15 wt% GNP inclusions. • Hall measurements show that the composites exhibit p-type semiconducting behavior. • Maximum ZT of 0.44 × 10−3 is obtained with 15 wt% GNP inclusions. Cement based thermoelectric materials can convert the available ambient heat absorbed by the building surfaces in summer into electrical energy. These materials can have an impact on the improvement of indoor climate of buildings, reduction of energy consumption and energy harvesting applications especially in the urban areas. In this paper, the thermoelectric properties of cement based composites with graphene nanoplatelets (GNP) inclusions were reported for the first time. GNP-cement mixtures were prepared by planetary ball milling and compressed subsequently to form bulk composites. We report the maximum electrical conductivity of 16.2 Scm−1 and Seebeck coefficient of +34.0 µVK−1 in this work. Hall measurement was performed to determine the material type and carrier concentration. It was found that all specimen exhibit p-type semiconductor behavior. Thermal diffusivity measurements were carried out using laser flash measurement technique. The highest figure of merit 0.44 × 10−3 was achieved at about 70 °C. Enhanced thermoelectric properties of graphene nanoplatelets cement based composites have a promising prospect in the urban heat island effect alleviation, thus saving electricity consumption and energy harvesting. Image, graphical abstract [ABSTRACT FROM AUTHOR]

This study examines the spatial-temporal changes of land cover and the surface urban heat island (SUHI) effect in the Pearl River Delta (PRD) region from 2000 to 2015. The Local Climate Zone (LCZ) concept is used, given its standard but comprehensive classification scheme designed for urban climate studies. Firstly, historical LCZ maps of the PRD region were generated using the World Urban Database and Access Portal Tools (WUDAPT) protocol. Secondly, summer mean land surface temperature (LST) during daytime and night-time was retrieved from remote sensing data to analyze the SUHI. Thirdly, the correspondence between the spatial-temporal patterns of LCZ and LST were explored. The results show that urbanization in this region comprises transformation from natural land covers to built types and conversion in the built up, in particular densification and vertical enhancement of existing urban types. The LST in the region increased in general but the spatial pattern of LST increase is affected by the land cover change. LCZ 6 (open low-rise) and LCZ 8 (large low-rise) show the greatest increase in LST. LCZ 4 (open high-rise) and LCZ 8 are the two dominant LCZs in high SUHI zone and LCZ 8 keeps growing as the most principal LCZ type. • Land cover changes in the PRD region show that urbanization has substantially transferred natural areas into urban cover. • Urbanization shows conversion from natural cover and vertical enhancement and densification from multi-temporal LCZ maps. • Isolated hot areas over individual cities merged and daytime LST increased faster than night-time LST in the PRD. • The LST changes echo the land cover changes in the PRD region during the study period. • SUHI intensified in this region due to the expansion of LCZ built types and high SUHI zone is dominated by LCZ 4 and LCZ 8. [ABSTRACT FROM AUTHOR]