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There is an urgent need for strategies to reduce the negative impacts of a warming climate on human health. Cooling urban neighborhoods by planting trees and vegetation and increasing albedo of roofs, pavements, and walls can mitigate urban heat. We used synoptic climatology to examine how different tree cover and albedo scenarios would affect heat-related morbidity in Los Angeles, CA, USA, as measured by emergency room (ER) visits. We classified daily meteorological data for historical summer heat events into discrete air mass types. We analyzed those classifications against historical ER visit data to determine both heat-related and excess morbidity. We used the Weather Research and Forecasting model to examine the impacts of varied tree cover and albedo scenarios on meteorological outcomes and used these results with standardized morbidity data algorithms to estimate potential reductions in ER visits. We tested three urban modification scenarios of low, medium, and high increases of tree cover and albedo and compared these against baseline conditions. We found that avoiding 25% to 50% of ER visits during heat events would be a common outcome if the urban environment had more tree cover and higher albedo, with the greatest benefits occurring under heat events that are moderate and those that are particularly hot and dry. We conducted these analyses at the county level and compared results to a heat-vulnerable, working-class Los Angeles community with a high concentration of people of color, and found that reductions in the rate of ER visits would be even greater at the community level compared to the county.

In the context of escalating global energy demands, urban areas, specifically the building sector, contribute to the largest energy consumption, with urban overheating exacerbating this issue. Utilizing urban modelling for heat-mitigation and reduction of energy demand is crucial steps towards a sustainable built-environment, complementing onsite energy generation in the design and development of Net-zero Energy (NZE) Settlement, especially in the context of Australian weather conditions. Addressing a significant gap in existing literature, this study offers empirical analysis on the climate and energy efficacy of integrated heat mitigation strategies applied in 14 neighbourhood typologies located in Sydney, Australia. Examining the application of cool materials on roads, pavements, and rooftops, alongside urban vegetation enhancement, the analysis demonstrates scenario effectiveness on heat mitigation that leads to reduce ambient temperature and energy demands along with CO2 emissions within the neighbourhoods. Considering building arrangement, built-area ratio, building height, and locations, ENVI-met and CitySim are utilized to assess the heat-mitigation and the energy demand of neighbourhoods, respectively. Results indicate that mitigation measures can lead up to a 2.71 °C reduction in ambient temperature and over 25% reduction in Cooling Degree Hours, with a 34.34% reduction in cooling energy demand and overall energy savings of up to 12.49%. In addition, the annual energy-saving yields a CO2 reduction of approximately 141.12 tonnes, where additional vegetation further amplifies these reductions by enhancing CO2 absorption. This study showcases the pathway towards achieving NZE goals in climates similar to that of Australia, highlighting significant benefits in heat-mitigation, environmental impact, and energy-savings. [ABSTRACT FROM AUTHOR]

Comprehensive studies comparing impacts of building and street levels interventions on air temperature at metropolitan scales are still lacking despite increased urban heat‐related mortality and morbidity. We therefore model the impact of 9 interventions on air temperatures at 2 m during 2 hot days from the summer 2018 in the Greater London Authority area using the WRF BEP‐BEM climate model. We find that on average cool roofs most effectively reduce temperatures (∼−1.2°C), outperforming green roofs (∼0°C), solar panels (∼−0.5°C) and street level vegetation (∼−0.3°C). Application of air conditioning across London (United Kingdom) increases air temperatures by ∼+0.15°C. A practicable deployment of solar panels could cover its related energetic consumption. Current practicable deployments of green roofs and solar panels are ineffective at large scale reduction of temperatures. We provide a detailed decomposition of the surface energy balance to explain changes in air temperature and guide future decision‐making. Plain Language Summary: Multiple common city scale passive and active interventions exist to reduce urban population's exposure to extreme heat during hot spells. Nonetheless, a proper comparison of the effect that each of these interventions may have on the temperatures experienced within large cities is missing. Additionally, the radiative and thermal mechanisms that lead to outdoor temperature changes are often not detailed and could lead to detrimental effects for local populations, such as indirect increase of water vapor or reflection of solar radiation. Our study, focusing over London, compares several common interventions through a modeling experiment and finds that cool roofs largely outperform other interventions during the two hottest days of the summer 2018. We also find that green roofs are ineffective on average and that solar panels and tree vegetation would only marginally change temperature exposures. Large scale deployment of air conditioning would lead to increased temperature in the core of London. Solar panels could potentially provide sufficient energy for running air conditioning all over London, creating comfortable indoor environments, and green roofs could reduce temperatures during the day. We argue that such inter‐comparisons should guide future decision making. Key Points: City scale deployment of cool roofs leads to the greatest reduction in 2 m air temperatureGreen roofs do not decrease daily average temperature but have a daytime cooling effectSolar photovoltaic panels can reduce temperatures in London by capturing sensible heat flux and generate electrical power [ABSTRACT FROM AUTHOR]

Green infrastructure (GI) offers a promising solution for mitigating the adverse effects of climate change, but evaluating its effectiveness necessitates a comprehensive understanding of how that has been quantified in the literature. This study aims to review the methods (monitoring, remote sensing, and modelling) employed to assess the effectiveness of GI in urban areas for three ecosystem services: heat mitigation (cooling of air temperature), thermal comfort control, and air quality mitigation. The objectives include evaluating the suitability of these approaches across diverse scales, categorising the essential parameters, and identifying the strengths and limitations inherent in each method. Through a literature review, 126 research papers were selected for detailed analysis. Modelling was the dominant method for heat mitigation (45.6 %), thermal comfort (70 %), and air pollution (51.9 %). The main inputs for assessing these three ecosystem services by GI were: meteorological parameters used in monitoring or modelling, morphological parameters (describing vegetation, surface, and built-up area conditions), specified parameters depending on the evaluated benefit such as landscape metrics (for heat mitigation), personal factors (for thermal comfort), pollutant measures (for air pollution), and other parameters (e.g. building and traffic heat emissions). The application scale of each method was dependent on the instruments, satellite data, and simulation tools utilised. Monitoring methods were employed in studies ranging from street-scale to neighbourhood-scale, remote sensing methods covered city-scale to regional-scale assessments, and modelling studies spanned from street-scale to regional-scale analyses. These diverse methods used to assess the GI benefits each have individual strengths and limitations which need to match the context and objectives of the study.

Heat exposure poses health risks that disproportionately burden disadvantaged communities. Trees protect against heat, but significant barriers exist to growing robust urban forests. In drier climates, complex logistics of watering during a multi-year establishment period pose a challenge because street trees are typically unirrigated and funding for maintenance is generally unavailable. This study tested the impacts of varying theory-guided community engagement approaches on beliefs, attitudes, knowledge, and behaviors related to foster street tree stewardship and individual-level heat mitigation actions in 116 households in Los Angeles County, USA. We tested a control intervention against experimental messaging focused on either public health or environmental health, and also segmented participants by the degree of prior household engagement with a local tree planting group. Outcomes measured were soil moisture, tree health, and survey responses indicating benefits and barriers related to tree stewardship. Results indicate that intervention messages had limited effect on these outcomes, and that level of engagement by the tree planting group was a stronger predictor of tree stewardship. We also found that tree stewardship correlated positively to heat protection measures, suggesting that environmental engagement may be an effective portal to reducing heat risk.

Urban vegetation has an essential role in maintaining the hydrological and energy balance. These processes in urban areas have been long overlooked due to the fragmentation and uneven feature of land use and vegetation distribution. Recent advances in remote sensing and the ease of data acquisition have allowed a more precise mapping of vegetation and land cover, making it possible to simulate the above processes at micro scales. This research selects a small typical residential catchment in Japan as the study area and the purpose of this research is to investigate the impact of urban vegetation on mitigating urban runoff and the heat island effect. The remote-sensed Normalized Difference Vegetation Index (NDVI) data were used to represent vegetation spatial distribution and seasonal variation. A single layer canopy model and the Storm Water Management Model were coupled to simulate interception, evapotranspiration, and runoff generation processes. The effects of vegetation amount and landscape patterns on the above processes were also considered. The results showed that the coupled model had a satisfactory performance in the modeling of these processes. When the vegetation amount was set to 1.4 times its original value, the summer total runoff had a 10.7% reduction and the average surface temperature had a 2.5 °C reduction. While the vegetation amount was 0.8 times its original value, the total runoff increased by 6%, and the average surface temperature in summer increased by 1.5 °C. The combination of green roof and dense street trees showed the best mitigation performance among the different landscape patterns. The results of this study could be used as a reference for future green infrastructure development in areas with similar climate and vegetation characteristics. [ABSTRACT FROM AUTHOR]

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 (Tmrt), 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. [ABSTRACT FROM AUTHOR]

Abstract Comprehensive studies comparing impacts of building and street levels interventions on air temperature at metropolitan scales are still lacking despite increased urban heat‐related mortality and morbidity. We therefore model the impact of 9 interventions on air temperatures at 2 m during 2 hot days from the summer 2018 in the Greater London Authority area using the WRF BEP‐BEM climate model. We find that on average cool roofs most effectively reduce temperatures (∼−1.2°C), outperforming green roofs (∼0°C), solar panels (∼−0.5°C) and street level vegetation (∼−0.3°C). Application of air conditioning across London (United Kingdom) increases air temperatures by ∼+0.15°C. A practicable deployment of solar panels could cover its related energetic consumption. Current practicable deployments of green roofs and solar panels are ineffective at large scale reduction of temperatures. We provide a detailed decomposition of the surface energy balance to explain changes in air temperature and guide future decision‐making.

Context: Urban parks are essential for maintaining aesthetics within cities and keeping their its energy balance by helping mitigate the Urban Heat Island (UHI) effect through controlling ambient and land surface temperature (LST). Objectives: To investigate the impact of cooling in terms of distance by variously configured urban parks of a humid subtropical city, using landscape metrics and open-source data. Methods: Land use (LU) was obtained through maximum likelihood classification of 3 m resolution aerial RGB-NIR imagery supported by ground control points and park boundaries collected during field survey. LST at matching resolution was obtained through downscaling of Landsat-8 LST at 30/100m resolution, calculated with the Radiative Transfer Equation (RTE). Landscape metrics for patches of parks were calculated using landscapemetrics R library and related to neighbourhood distances over built-up land use (LU). Results: Urban parks with homogenous cores and less complex shape provide distinctly higher cooling of neighbouring built-up LU of circa 2.55 °C over the distance of 18 m from park boundaries. Four metrics: contiguity index (CONTIG), core area index (CAI), fractal dimension index (FRAC) and perimeter-area ratio (PARA) represent significant relationship between spatial configuration of parks and their cooling distance. No cooling capacity of parks regardless of their shape and core was observed beyond the distance of 18 m, which remained constant with small fluctuations in the range of 0.5 °C up to the distance of 600 m. Conclusions: The study concludes that cooling distance of urban parks in their neighbourhood extends up to 18 m, which is shorter than suggested by other studies. [ABSTRACT FROM AUTHOR]

The combination of urbanization and global warming leads to urban overheating and compounds the frequency and intensity of extreme heat events due to climate change. Yet, the risk of urban overheating can be mitigated by urban green-blue-grey infrastructure (GBGI), such as parks, wetlands, and engineered greening, which have the potential to effectively reduce summer air temperatures. Despite many reviews, the evidence bases on quantified GBGI cooling benefits remains partial and the practical recommendations for implementation are unclear. This systematic literature review synthesizes the evidence base for heat mitigation and related co-benefits, identifies knowledge gaps, and proposes recommendations for their implementation to maximize their benefits. After screening 27,486 papers, 202 were reviewed, based on 51 GBGI types categorized under 10 main divisions. Certain GBGI (green walls, parks, street trees) have been well researched for their urban cooling capabilities. However, several other GBGI have received negligible (zoological garden, golf course, estuary) or minimal (private garden, allotment) attention. The most efficient air cooling was observed in botanical gardens (5.0 ± 3.5°C), wetlands (4.9 ± 3.2°C), green walls (4.1 ± 4.2°C), street trees (3.8 ± 3.1°C), and vegetated balconies (3.8 ± 2.7°C). Under changing climate conditions (2070–2100) with consideration of RCP8.5, there is a shift in climate subtypes, either within the same climate zone (e.g., Dfa to Dfb and Cfb to Cfa) or across other climate zones (e.g., Dfb [continental warm-summer humid] to BSk [dry, cold semi-arid] and Cwa [temperate] to Am [tropical]). These shifts may result in lower efficiency for the current GBGI in the future. Given the importance of multiple services, it is crucial to balance their functionality, cooling performance, and other related co-benefits when planning for the future GBGI. This global GBGI heat mitigation inventory can assist policymakers and urban planners in prioritizing effective interventions to reduce the risk of urban overheating, filling research gaps, and promoting community resilience.

Urban greening is often proposed for urban heat island (UHI) mitigation because vegetation provides shade and increases evapotranspiration. However, vegetation has lower albedo and higher emissivity than the bare soil it often replaces, which increases incoming energy fluxes. Here, we use the Weather Research and Forecasting model to quantify and compare the albedo and non‐albedo effects (i.e., changes in emissivity, surface roughness, and evaporative fluxes) of urban greening in the Los Angeles Basin under policy relevant urban greening scenarios. When albedo‐induced effects were included in the model, daytime surface temperatures in urban areas warmed by 0.70 ± 0.89°C with increases in the sensible heat flux outweighing increases in the latent heat flux from increased evapotranspiration. In contrast, daytime surface temperatures cooled by 0.27 ± 0.72°C when the albedo‐induced effects were ignored. At night, including albedo‐induced effects of urban greening resulted in only half the cooling modeled in the non‐albedo simulations. Near surface air temperatures also had contrasting model results, with nighttime cooling of 0.21 ± 0.47°C outweighing slight daytime warming of 0.04 ± 0.32°C in the non‐albedo simulations and daytime warming of 0.33 ± 0.41°C outweighing slight nighttime cooling of 0.05 ± 0.46°C in the albedo simulations. Our results reveal the critical role that albedo plays in determining the net surface climate effects of urban greening. Reductions in albedo from urban greening should be carefully considered by policy makers and urban planners, especially as high albedo roofs and pavements are simultaneously being deployed for UHI mitigation in many cities. Plain Language Summary: Urban greening initiatives are often proposed to cool cities because vegetation can provide shade and increase evaporative cooling. However, vegetation also has competing warming effects like decreasing albedo, meaning vegetation absorbs a larger fraction of incoming energy than the bare soil it often replaces. In this study, we used the Weather Research and Forecasting model to quantify and compare the effects of reduced albedo from urban greening to non‐albedo effects, which included changes in emissivity, surface roughness, and evaporative fluxes. When reductions in albedo from urban greening were included in our model, daytime surface temperatures warmed by 0.70 ± 0.89°C, indicating that the competing warming effects of urban greening outweighed the increased evaporative cooling from the added vegetation. In contrast, daytime surface temperatures cooled by 0.27 ± 0.72°C when reductions in albedo from urban greening were ignored. Our results reveal the critical role that albedo plays in determining the temperature effects of urban greening. Reductions in albedo from urban greening should be carefully considered by policy makers and urban planners to better optimize urban greening for heat mitigation, especially as cool surfaces like high albedo roofs and pavements are simultaneously being deployed in many cities. Key Points: Increasing urban vegetation can reduce albedo, which increases incoming energy fluxesAlbedo‐induced effects of urban greening increased daytime 2‐m air temperatures and suppressed most of the nighttime cooling signalAlbedo‐induced warming effects of urban greening may outweigh the cooling effects of increased evapotranspiration [ABSTRACT FROM AUTHOR]

The urban heat island effect poses a growing threat to human society, especially in densely populated and developed megacities. With the introduction of the Local Climate Zones (LCZ) framework, new perspectives and findings have been brought to urban heat island studies. This study investigated the cooling effect of vegetation and albedo on the surface urban heat island (SUHI) in the classification system of LCZ during different seasons, using three Chinese megacities as case study areas. Single-factor linear regression and Pearson's correlation coefficient were applied to analyze the seasonal cooling effect of both albedo and the NDVI on the SUHI within different LCZs. The results show that (1) the variability of the SUHI is reflected in its dominance and intensity within certain LCZs in different cities and in the efficiency of cooling factors; (2) the cooling effect of vegetation is dominant in each season, and the cooling effect produced by albedo within specific seasons can be differentiated by LCZs. This study provides valuable information for the mitigation of the SUHI magnitude in specific regions and at specific times of the year. [ABSTRACT FROM AUTHOR]

Global warming is precipitating an amplification of severe meteorological occurrences such as prolonged dry spells and episodes of elevated temperatures. These phenomena are instigating substantial elevations in environmental warmth, with metropolitan regions bearing the brunt of these impacts. Currently, extreme heat is already impacting 30% of the global populace, and forecasts suggest that this figure will escalate to 74% in the forthcoming years. One of the objectives outlined in the United Nations 2030 agenda, specifically within Sustainable Development Goal 11 (SDG11), is the attainment of sustainable urban development. To achieve this, it is imperative to scrutinize and delve into urban environmental conditions in order to understand their dynamics comprehensively. This understanding serves as the foundation for implementing mitigation and resilience strategies against climate change, ultimately enhancing the well-being of city residents. In this context, the field of remote sensing and geographic information systems has made substantial advancements. Notably, the UrbClim model, developed by the European Space Agency, facilitates the assessment of environmental conditions within numerous European urban centers. This research, utilizing data from UrbClim, examines the evolution of the heat stress index (Hi) during extreme heat conditions in Barcelona during the summer of 2017. Leveraging Landsat 8 satellite imagery, we derived the following variables: the normalized difference vegetation index and the normalized building difference index. Our findings reveal that during extreme heat conditions, the Hi index experiences an escalation, with areas characterized by a higher population density and industrial zones displaying lower resistance in contrast to regions with a lower population density and rural areas, which exhibit greater resilience to Hi. This disparity can be attributed to higher vegetation coverage and reduced building density in the latter areas. In this way, Hi increases more quickly and intensely and decreases more slowly when using high temperatures compared to average temperatures. This is of utmost importance for the future planning of new urban developments. [ABSTRACT FROM AUTHOR]

As the global temperature and rapid urbanization continue to rise, urban heat islands (UHIs) also continue to increase across the world. Following the heat equity concept, UHIs disproportionately impact disadvantaged or overburdened communities. Green infrastructure (GI) has been at the forefront of UHI mitigation efforts, including nature-based solutions like parks, pervious open spaces, wooded areas, green roofs, rain gardens, and shade trees. In this paper, we use a heat equity lens to analyze community perceptions of the intersection of climate change, UHI, and GI in Camden, New Jersey—a post-industrial city with a history of environmental injustices. Based on a mixed-methods analysis of survey responses (n = 107), 11 years of relevant X (formerly Twitter) posts (n = 367), and geospatial data, we present community perceptions of and connections between climate change, UHI, and GI and discuss major themes that emerged from the data: perceived heat inequity in Camden triggers negative emotions; a public knowledge gap exists regarding climate change-UHI-GI connections; and perceived inequitable distribution of GI and certain GI planning and maintenance practices may negatively impact UHI mitigation strategies. We argue these themes are useful to urban planners and relevant professionals while planning for heat equity and mitigating UHI effects in disadvantaged urban communities like Camden. [ABSTRACT FROM AUTHOR]

Urban overheating is the most documented phenomenon of climate change impacting humans. This article presents the most recent developments on the magnitude and characteristics of urban overheating and the potential synergies with global climatic change. It analyses the latest qualitative and quantitative data on the impact of higher urban temperatures on buildings' energy supply and demand, heat-related mortality, morbidity and wellbeing, human productivity, survivability of low-income populations, and environmental quality of cities. It describes the state of the art on the development of innovative mitigation materials, advanced urban greenery, heat dissipation, and evaporative techniques as the main mitigation and adaptation technologies to offset the impact of urban overheating. It also analyses the current knowledge on the impact of each mitigation technology on energy, health, environmental quality, urban economy, and survivability. Finally, this article presents the main future challenges related to urban overheating and proposes a specific research agenda to alleviate and counterbalance its impact on human life. [ABSTRACT FROM AUTHOR]

Climate change is creating an increase in temperatures, which is harming the quality of life of people all over the world, particularly those with minimal financial resources. While 30% of the world's population is now vulnerable to extreme heat, estimates show that ratio will rise to 74% in the next 20 years, according to forecasts. Using the UrbClim climate model, this study examines the space-time variability of the heat stress index (HI) in different local climate zones (LCZs), as well as how heat wave conditions might affect this index based on land use and land cover. To that end, Seville, in Southern Spain, was investigated during the summer of 2017, when it had four heat waves. The following indices were considered for each urban sub-area: Normalized Difference Vegetation, Proportion Vegetation, Normalized Difference Built, and Urban Index. The goal is to conduct a statistical analysis of the link between the aforementioned elements and the heat stress index in order to recommend mitigation and resilience techniques. Our findings showed that compact and industrial LCZs (2, 3, and 10) are less resistant to HI than open and rural regions (5, 6, B, D, and G), which are more resistant to HI due to higher vegetation rates. The heat wave condition exacerbates the HI in all LCZs. As a result, initiatives such as enhancing open space, increasing green space, or using green roofs and façades might alleviate heat stress and improve people's quality of life. [ABSTRACT FROM AUTHOR]

The cities of desert climates are anticipated to recognize a synergy of urban heat island (UHI) and severe heat waves during summertime. To improve the urban thermal environment, the present study aims quantitatively explore a strategically designed network of vegetation patches called green infrastructure (GI) in subtropical desert cities such as Dubai. To achieve a more comfortable temperature environment, we built and simulated four GI situations with higher GI fractions, GI25, GI50, GI75, and GI100. Using a mesoscale urban model, the mosaic approach is utilized to test potential thermal improvement and urban climate impact, and a portion of each urban grid cell in the model domain is altered with various species of urban vegetation patches by 25%, 50%, 75%, and 100%. The daily peak reduction in ambient temperature at 17:00LT is similar to 0.0168 °C per unit of GI increase when compared to the untreated scenario; however, the maximum anticipated daytime summer temperature decline for GI25, GI50, GI75, and GI100 is 0.6 °C, 1.1 °C, 1.4 °C, and 1.7 °C, respectively. The associated reduction in nighttime ambient temperature per unit increase in the GI is 0.0432 °C, with a maximum temperature drop of around 2.4 °C for the GI100 scenario. Increased GI reduces the height of the planetary boundary layer (PBL) by up to 468 m, which might lead to greater pollution concentrations. While GI-based cooling has a significant influence on delayed sea breeze and humidity, it may raise the risk of heat discomfort in the indoor building environment. This study adds to our understanding of the potential for GI mitigation as well as the seasonal impact of developing GIs on the desert urban boundary layer. [ABSTRACT FROM AUTHOR]

Increasing heat in urban areas raises heat-related health risks. Green infrastructure and managing surface albedo can reduce the radiation exposure of pedestrians. However, selecting options among various radiant fluxes mitigation strategies is challenging, particularly due to potential interactions among options such as planting vegetation or changing surface albedos. We used a multi-strategies model for determining optimal design combinations for reducing mean radiant temperature (MRT) in urban environments across a range of costs and benefits. The solutions are developed by a non-dominated sorting genetic algorithm II (NSGA II) with a MRT simulator. We selected four MRT reduction strategies: tree planting, grass planting, albedo reduction of building walls, and albedo reduction of sidewalks. Model test results for a simulated street canyon show a wide range of optimal alternative plans considering the combination effects of the four strategies. While previous studies have focused on single options to reduce heat load, we found benefits were higher by using a combination of these strategies, which can provide synergistic benefits. These results provide useful information for decision makers confronting real world problems such as heat related mortality. Thermal-friendly design methods and green infrastructure will help the urban environment become sustainable and improve human health and well-being.

Paralympic athletes may be at increased risk for exertional heat illness (EHI) due to reduced thermoregulatory ability as a consequence of their impairment. This study investigated the occurrence of heat-stress related symptoms and EHI, and the use of heat mitigation strategies in Paralympic athletes, both in relation to the Tokyo 2020 Paralympic Games and previous events. Paralympic athletes competing in Tokyo 2020 were invited to complete an online survey five weeks prior to the Paralympics and up to eight weeks after the Games. 107 athletes (30 [24–38] years, 52% female, 20 nationalities, 21 sports) completed the survey. 57% of respondents had previously experienced heat-stress related symptoms, while 9% had been medically diagnosed with EHI. In Tokyo, 21% experienced at least one heat-stress related symptom, while none reported an EHI. The most common symptom and EHI were, respectively, dizziness and dehydration. In preparation for Tokyo, 58% of respondents used a heat acclimation strategy, most commonly heat acclimatization, which was more than in preparation for previous events (45%; P = 0.007). Cooling strategies were used by 77% of athletes in Tokyo, compared to 66% during past events (P = 0.18). Cold towels and packs were used most commonly. Respondents reported no medically-diagnosed EHIs during the Tokyo 2020 Paralympic Games, despite the hot and humid conditions in the first seven days of competition. Heat acclimation and cooling strategies were used by the majority of athletes, with heat acclimation being adopted more often than for previous competitions. [ABSTRACT FROM AUTHOR]

Compare the effects of ice slurry ingestion at low and normal doses on endurance capacity and exertional heat stress-induced gastrointestinal perturbations. Randomised, cross-over design. Twelve physically active males completed four treadmill running trials, ingesting ice slurry (ICE) or ambient drink (AMB) at 2 g·kg−1 (Normal; N) or 1 g·kg−1 (Low; L) doses every 15-min during exercise and 8 g·kg−1 (N) or 4 g·kg−1 (L) pre- and post-exercise. Pre-, during and post-exercise serum intestinal fatty-acid binding protein ([I-FABP]) and lipopolysaccharide ([LPS]) concentrations were determined. Pre-exercise gastrointestinal temperature (T gi) was lower in L + ICE than L + AMB (p < 0.05), N + ICE than N + AMB (p < 0.001) and N + ICE than L + ICE (p < 0.001). Higher rate of T gi rise (p < 0.05) and lower estimated sweat rate (p < 0.001) were observed in N + ICE than N + AMB. Rate of T gi rise was similar at low dose (p = 0.113) despite a lower estimated sweat rate in L + ICE than L + AMB (p < 0.01). Time-to-exhaustion was longer in L + ICE than L + AMB (p < 0.05), but similar between N + ICE and N + AMB (p = 0.142) and L + ICE and N + ICE (p = 0.766). [I-FABP] and [LPS] were similar (p > 0.05). L + ICE elicited a lower heat dissipation compensatory effect with similar endurance capacity as N + ICE. Ice slurry conferred no protection against exertional heat stress-induced gastrointestinal perturbations. [ABSTRACT FROM AUTHOR]

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Natural infrastructure is essential in reducing thermal discomfort caused by the urban heat island (UHI) effect. Optimizing and planning green and blue spaces can help establish nature-based urban heat mitigation strategies that benefit sustainable urban development. Most current studies on urban heat mitigation have focused on the single heat reduction effect of green space or blue space, while there has been a lack of research on the combined cooling effects of blue and green spaces. Moreover, existing heat mitigation models and methods cannot directly guide the optimization of blue–green spatial patterns at the urban scale. This has led to an unclear relationship between heat mitigation effects and blue–green spatial patterns. Based on land use data, meteorological data, and biophysical information as inputs, this paper utilized the InVEST urban cooling model (UCM) and scenario analysis method to simulate urban heat mitigation patterns by setting up different blue–green space configuration scenarios. The relative contribution of blue–green space changes to the variation of heat mitigation benefits was quantitatively estimated using the difference comparison method, and the relationship between heat reduction effects and urban blue–green spatial patterns was elucidated using spatial analysis methods. The results show that the InVEST UCM captured some of the variability in the surface thermal response of Wuhan and can be applied to the modeling of urban heat mitigation patterns. Furthermore, they show that consideration of the cooling effect of water evaporation can improve the simulation accuracy to some extent. In Wuhan, there were regional differences in heat mitigation patterns and the heat mitigation effect was significantly higher in the suburbs than in the city. Additionally, urban parks, lakes, and mountains with surface or block distribution had noticeable cooling benefits. Finally, the scenario simulation results demonstrate that green space was more efficient at mitigating heat, while blue space was more critical for the geographical partitioning of the UHI. These findings can provide a reference for the planning and optimal management of urban blue and green spaces, as well as for the design of heat reduction policies. [ABSTRACT FROM AUTHOR]

Different heat mitigation technologies have been developed to improve the thermal environment in cities. However, the regional impacts of such technologies, especially in the context of a tropical city, remain unclear. The deployment of heat mitigation technologies at city‐scale can change the radiation balance, advective flow, and energy balance between urban areas and the overlying atmosphere. We used the mesoscale Weather Research and Forecasting model coupled with a physically based single‐layer urban canopy model to assess the impacts of five different heat mitigation technologies on surface energy balance, standard surface meteorological fields, and planetary boundary layer (PBL) dynamics for premonsoon typical hot summer days over a tropical coastal city in the month of April in 2018, 2019, and 2020. Results indicate that the regional impacts of cool materials (CMs), super‐cool broadband radiative coolers, green roofs (GRs), vegetation fraction change, and a combination of CMs and GRs (i.e., "Cool city (CC)") on the lower atmosphere are different at diurnal scale. Results showed that super‐cool materials have the maximum potential of ambient temperature reduction of 1.6°C during peak hour (14:00 LT) compared to other technologies in the study. During the daytime hours, the PBL height was considerably lower than the reference scenario with no implementation of strategies by 700 m for super‐cool materials and 500 m for both CMs and CC cases; however, the green roofing system underwent nominal changes over the urban area. During the nighttime hours, the PBL height increased by CMs and the CC strategies compared to the reference scenario, but minimal changes were evident for super‐cool materials. The changes of temperature on the vertical profile of the heat mitigation implemented city reveal a stable PBL over the urban domain and a reduction of the vertical mixing associated with a pollution dome. This would lead to crossover phenomena above the PBL due to the decrease in vertical wind speed. Therefore, assessing the coupled regional impact of urban heat mitigation over the lower atmosphere at city‐scale is urgent for sustainable urban planning. Plain Language Summary: In this research we evaluated the impact on the city meteorology and on the lower atmosphere due to the use of several heat mitigation technologies. The numerical simulations were carried out during typical summer hot days over an Indian tropical city. The heat mitigation strategies considered include very reflective materials (cool materials (CMs), super‐cool broadband radiative coolers) green roofs (GRs), changes in the vegetation fraction, and a combination of CMs and GRs (i.e., cool city (CC)). In particular, these mitigation strategies and technologies were incorporated in a weather model (the mesoscale weather research and forecasting coupled with a single‐layer urban canopy model) at the city‐scale. Our results showed that surface and rooftop heat mitigation strategies modify the meteorological fields and the dynamics of the lower atmosphere within the city during the hot summer days. The super‐cool broadband radiative coolers are most proficient in decreasing ambient temperature and planetary boundary layer, followed by CMs, CC, GRs, and augmenting vegetation fraction. The super‐cool broadband radiative coolers produced the most efficient strategy. Nevertheless, it has unintended consequences as they modify the temperature vertical profile, enhancing the stability over the urban domain and reducing the air's vertical mixing. The results presented show that the used model can be a valuable instrument to evaluate the implementation effects of heat mitigation technologies in the urban environment for extreme urban heat management, such as the newly developed super‐cool materials. However, careful attention should be paid to unintended consequences. Key Points: weather research and forecasting model is a valuable tool to evaluate the effects of heat mitigation measures in the urban environment for urban heat managementSurface standard meteorological fields and lower atmospheric dynamics within the city are modified by heat mitigation measuresThe super‐cool broadband radiative coolers yielded the most efficient strategy for urban cooling in tropical context [ABSTRACT FROM AUTHOR]

The excessive warming in the built environment, due to urbanization and anthropogenic heat emissions, has adverse effects on building energy consumption. Diverse technology using, e.g., vegetated roofs or innovative roof materials, have been proposed and implemented to ameliorate both indoor and outdoor thermal environments and reduce energy consumption. In this study, we apply a state-of-the-art urban canopy model to simulate the thermal performance of multiple roof technology, viz. the white, green, and hybrid roofs, in the contrasting urban environments of Princeton, NJ and Phoenix, AZ, USA. In addition, we estimate the combined energy-water saving potential for green roofs with five different irrigation schemes. It is found that green roofs can achieve a combined energy-water saving of $9.68 m−2 roof area in Phoenix with moisture-controlled irrigation, and $5.23 m−2 in Princeton without irrigation. These results can help to promote building energy efficiency by adapting to flexible and sustainable roof technology for heat mitigation. • Evaluating diverse roof systems for cooling and building energy performance. • Green roofs with flexible irrigation maximize combined energy-water savings. • The use of hybrid roofs can avoid the heating penalty in cold seasons. • Optimal building energy efficiency depends on background climate conditions. [ABSTRACT FROM AUTHOR]

• The study integrates Local Climate Zone classification with InVEST and CA-Markov models. • The cooling potential of Guangzhou was assessed under three urban development scenarios. • Compact low-rise and heavy industry areas exhibited the lowest cooling benefits. • Blue-green infrastructure contributed a total energy saving of 2.05 × 10¹⁰ kW·h. • The Environmental Protection scenario serves as a reference for sustainable development pathways. Amidst mounting concerns regarding health risks associated with excessive carbon emissions, attention has turned to the heat mitigation ability of blue-green infrastructure (BGI). BGI offers heat mitigation through transpiration cooling, effectively countering the urban heat island (UHI) effect while facilitating energy conservation and carbon reduction. This study adopted the InVEST model to assess the spatial pattern of UHI and heat mitigation service based on the Local Climate Zone (LCZ) classification, along with quantifying the energy savings in Guangzhou for 2019. The results revealed that the UHI effect exhibited greater intensity in the southwest built-up area. Compact Lowrise (LCZ-3) and Heavy Industry (LCZ-10) areas demonstrated higher UHI intensity, while Water (LCZ-G) and Dense Trees (LCZ-A) areas showcased the highest heat mitigation index (HMI) and optimal cooling capacities. Three urban development scenarios were devised to simulate the UHI distribution, heat mitigation capacity, and energy savings by 2025, using the CA-Markov model. In comparison to the Baseline scenario, the Environmental Protection scenario showed a modest 3.67 % decrease in the built-up area, but a noteworthy increase in HMI and energy saving, by 21.2 % and 6.6 % respectively. This scenario can serve as a reference pathway for urban energy conservation and sustainable development. [ABSTRACT FROM AUTHOR]

• The suitability of the LCZ framework is examined in Kabul, Afghanistan. • The current LCZ framework does not reflect the local characteristics of the city. • Four sub-classess related to the LCZs 3, 6, 7, and 9 were identified. • Surface cover, building height, and sky view factor are key drivers of urban heat. • Key heat mitigation measures include increasing albedo and urban greening. To better investigate the Urban Heat Island (UHI) effect, a standardized framework known as Local Climate Zones (LCZ) has been developed and widely applied to numerous cities. However, cities from least-developed countries with heterogeneous typologies are underrepresented in the LCZ literature. This study assesses the applicability of the LCZ framework in the slum-dominant built-up environment of Kabul. Using a combined method involving GIS and remote sensing, we classified natural and built-type LCZs and analyzed LCZ-LST fluctuations. The analysis revealed that four new subclasses cover 23 % of the built type LCZs: LCZ 3 5 (mid/high-rise buildings within compact lowrise layouts) and LCZ 6 5 (midrise buildings among open lowrise areas) have the lowest LSTs at 34.36 °C and 34.42 °C in July, respectively. In contrast, LCZ 7 3 (two/three-story buildings in lightweight configurations), and LCZ 9 F (sparse buildings on bare soil or sand) have higher LSTs at 37.2 °C and 38.6 °C in July, respectively. These subclasses showed distinct zone parameter thresholds compared to standard LCZs. In most built-type LCZs, Average Building Height (ABH) and Pervious Surface Fraction (PSF) negatively influenced LST, while impervious surfaces and Sky View Factor contributed to higher LST. Based on the findings, LCZ-specified strategies (Vegetation, urban form, and using high-albedo materials) for LST mitigation are proposed. Furthermore, we provide planning, design, and policy recommendations aimed at mitigating urban heat, with potential applicability to other cities facing rapid urbanization and growth of informal settlements. The findings can inform action toward urban climate change adaptation. [ABSTRACT FROM AUTHOR]

As the global temperature and rapid urbanization continue to rise, urban heat islands (UHIs) also continue to increase across the world. Following the heat equity concept, UHIs disproportionately impact disadvantaged or overburdened communities. Green infrastructure (GI) has been at the forefront of UHI mitigation efforts, including nature-based solutions like parks, pervious open spaces, wooded areas, green roofs, rain gardens, and shade trees. In this paper, we use a heat equity lens to analyze community perceptions of the intersection of climate change, UHI, and GI in Camden, New Jersey—a post-industrial city with a history of environmental injustices. Based on a mixed-methods analysis of survey responses (n = 107), 11 years of relevant X (formerly Twitter) posts (n = 367), and geospatial data, we present community perceptions of and connections between climate change, UHI, and GI and discuss major themes that emerged from the data: perceived heat inequity in Camden triggers negative emotions; a public knowledge gap exists regarding climate change-UHI-GI connections; and perceived inequitable distribution of GI and certain GI planning and maintenance practices may negatively impact UHI mitigation strategies. We argue these themes are useful to urban planners and relevant professionals while planning for heat equity and mitigating UHI effects in disadvantaged urban communities like Camden.

The urban heat island effect poses a growing threat to human society, especially in densely populated and developed megacities. With the introduction of the Local Climate Zones (LCZ) framework, new perspectives and findings have been brought to urban heat island studies. This study investigated the cooling effect of vegetation and albedo on the surface urban heat island (SUHI) in the classification system of LCZ during different seasons, using three Chinese megacities as case study areas. Single-factor linear regression and Pearson’s correlation coefficient were applied to analyze the seasonal cooling effect of both albedo and the NDVI on the SUHI within different LCZs. The results show that (1) the variability of the SUHI is reflected in its dominance and intensity within certain LCZs in different cities and in the efficiency of cooling factors; (2) the cooling effect of vegetation is dominant in each season, and the cooling effect produced by albedo within specific seasons can be differentiated by LCZs. This study provides valuable information for the mitigation of the SUHI magnitude in specific regions and at specific times of the year.

Urban heat exposure is an increasing health risk among urban dwellers. Many cities are considering accommodating active mobility, especially walking and biking, to reduce greenhouse gas emissions. However, promoting active mobility without proper planning and transportation infrastructure to combat extreme heat exposure may cause more heat-related morbidity and mortality, particularly in future with projected climate change. This study estimated the effectiveness of active trip heat exposure mitigation under built environment and travel behavior change. Simulations of the Phoenix metro region's 624,987 active trips were conducted using the activity-based travel model (ABM), mean radiant temperature (TMRT, net human radiation exposure), transportation network, and local climate zones. Two scenarios were designed to reduce traveler exposure: one that focuses on built environment change (making neighborhoods cooler) and the other on travel behavior (switching from shorter travel time but higher exposure routes to longer travel time but cooler routes) change. Travelers experienced TMRT heat exposure ranging from 29°C to 76°C (84°F to 168°F) without environmental or behavioral change. Active trip TMRT exposures were reduced by an average of 1.2–3.7°C when the built environment was changed from a hotter to cooler design. Behavioral changes cooled up to 10 times more trips than changes in built environment changes. The marginal benefit of cooling decreased as the number of cooled corridors transformed increased. When the most traveled 10 km of corridors were cooled, the marginal benefit affected over 1,000 trips/km. However, cooling all corridors results in marginal benefits as low as 1 trip/km. The results reveal that heavily traveled corridors should be prioritized with limited resources, and the best cooling results come from environment and travel behavior change together. The results show how to surgically invest in travel behavior and built environment change to most effectively protect active travelers.

Current climate change aggravates human health hazards posed by heat stress. Forests can locally mitigate this by acting as strong thermal buffers, yet potential mediation by forest ecological characteristics remains underexplored. We report over 14 months of hourly microclimate data from 131 forest plots across four European countries and compare these to open‐field controls using physiologically equivalent temperature (PET) to reflect human thermal perception. Forests slightly tempered cold extremes, but the strongest buffering occurred under very hot conditions (PET >35°C), where forests reduced strong to extreme heat stress day occurrence by 84.1%. Mature forests cooled the microclimate by 12.1 to 14.5°C PET under, respectively, strong and extreme heat stress conditions. Even young plantations reduced those conditions by 10°C PET. Forest structure strongly modulated the buffering capacity, which was enhanced by increasing stand density, canopy height and canopy closure. Tree species composition had a more modest yet significant influence: that is, strongly shade‐casting, small‐leaved evergreen species amplified cooling. Tree diversity had little direct influences, though indirect effects through stand structure remain possible. Forests in general, both young and mature, are thus strong thermal stress reducers, but their cooling potential can be even further amplified, given targeted (urban) forest management that considers these new insights. [ABSTRACT FROM AUTHOR]

Depleting non-renewable resources and global warming motivated researchers to focus on passive cooling solutions to minimize the internal temperature of buildings. The benefits of using stacked coir mat and perlite in wet and dry conditions are tested for their cooling capacity compared to green roofs are explored in this research work. The benefits are quantified in terms of heat flow and temperature variations in a field experiment, and they are compared to a conventional bare roof in a tropical region in the Indian subcontinent (8.9142oN, 76.632oE). The heat transfer to the inside of the roof for dry coir mat paved, stacked coir mat and perlite bed, stacked wet coir mat and wet perlite bed, and extensive green roof system with coir mat as retaining layer are reduced by 38.43%, 63.21%, 55.3% and 56.97% respectively. This study evaluated the evaporative cooling capacity of wet coir mat and wet perlite, which have given almost near cooling capacity of green roof for 24 h. Considering its low maintenance and low initial cost, the usage of the stacked coir fibre mat with perlite shows a compatible reduction in heat transfer through the roof slab as that of the green roof. The coir insulation with perlite will undoubtedly reduce the energy requirement for heating ventilation and air conditioning (HVAC) systems to a greater extent. [ABSTRACT FROM AUTHOR]

Global warming is precipitating an amplification of severe meteorological occurrences such as prolonged dry spells and episodes of elevated temperatures. These phenomena are instigating substantial elevations in environmental warmth, with metropolitan regions bearing the brunt of these impacts. Currently, extreme heat is already impacting 30% of the global populace, and forecasts suggest that this figure will escalate to 74% in the forthcoming years. One of the objectives outlined in the United Nations 2030 agenda, specifically within Sustainable Development Goal 11 (SDG11), is the attainment of sustainable urban development. To achieve this, it is imperative to scrutinize and delve into urban environmental conditions in order to understand their dynamics comprehensively. This understanding serves as the foundation for implementing mitigation and resilience strategies against climate change, ultimately enhancing the well-being of city residents. In this context, the field of remote sensing and geographic information systems has made substantial advancements. Notably, the UrbClim model, developed by the European Space Agency, facilitates the assessment of environmental conditions within numerous European urban centers. This research, utilizing data from UrbClim, examines the evolution of the heat stress index (Hi) during extreme heat conditions in Barcelona during the summer of 2017. Leveraging Landsat 8 satellite imagery, we derived the following variables: the normalized difference vegetation index and the normalized building difference index. Our findings reveal that during extreme heat conditions, the Hi index experiences an escalation, with areas characterized by a higher population density and industrial zones displaying lower resistance in contrast to regions with a lower population density and rural areas, which exhibit greater resilience to Hi. This disparity can be attributed to higher vegetation coverage and reduced building density in the latter areas. In this way, Hi increases more quickly and intensely and decreases more slowly when using high temperatures compared to average temperatures. This is of utmost importance for the future planning of new urban developments.

The presence of green roofs in urban areas improves the energy efficiency of buildings; contributes to the capture of CO2, decreasing pollution; and improves the appearance of cities, increasing their sustainability. Additionally, green roofs must include plant species with low requirements and maintenance, and thus, succulent species could be useful in Mediterranean semi-arid regions. In this work, the thermal inertia and the effect of different succulent species as thermal barriers on mitigating the increase in temperature inside experimental compartments were studied in comparison to conventional covers used in the Spanish Mediterranean for a whole year. In general, green covers were more efficient than conventional ones for controlling temperature. Thus, temperatures under green covers were up to 8 °C lower than conventional covers and 3–5 °C lower than the ambient temperature at noon on summer days. Furthermore, significant differences were found between green covers. Thus, despite having high thermal inertia, Aptenia cordifolia showed the worst temperature records, while Aeonium arboreum was the most efficient at mitigating temperature changes both on cold winter nights and hot summer days—even better than Sedum spp., a usual succulent used commercially. Our results demonstrate that succulent species are efficient materials to use as green covers to improve thermal conditions in buildings in Mediterranean cities. This also suggests that the mixture of succulent species (i.e., not only made of Sedum spp.) with different colors and textures could beautify green roofs without compromising their energy efficiency. [ABSTRACT FROM AUTHOR]

Local climate zones (LCZs) provide a comprehensive framework to examine surface urban heat islands (SUHIs), but information is lacking on their thermal contributions and spatial effects in different macroclimate cities. A standard framework for distinguishing between the cooling effect and heating effect and spatial effect analysis based on the LCZ scheme was conducted in five distinct macroclimate cities, i.e., Yuanjiang (arid climate), Jinghong (tropical climate), Kunming (subtropical climate), Zhaotong (temperate climate), and Shangri-La (alpine climate). The results indicated that (1) built-up zones presented heating effects in Jinghong and Shangri-La, but opposite results were observed in Yuanjiang and Zhaotong. (2) The thermal contributions of natural zones with dense trees (LCZAs) and waterbodies (LCZGs) showed cooling effects in the five cities regardless of season. (3) The spatial effect of heating LCZs on land surface temperature (LST) was more significant than that of cooling LCZs in Jinghong and Shangri-La, but the opposite results occurred in Yuanjiang and Kunming. Moreover, the spatial effect was lower in Zhaotong than in other cities. (4) Lower LST differences between natural zones and built-up zones in winter than in summer decreased the spatial effects. In summary, the thermal contributions of LCZs and their spatial heating/cooling effects were different among five distinct climate backgrounds, which implies that targeted measures must be used in different macroclimates. [ABSTRACT FROM AUTHOR]

Nature-based solutions (NbS) present an opportunity to reduce rising temperatures and the urban heat island effect. A multi-scale study in Toronto, Ontario, Canada, evaluates the effect of NbS on air and land surface temperature through two field campaigns at the micro and meso scales, using in situ measurements and LANDSAT imagery. This research demonstrates that the application of NbS in the form of green infrastructure has a beneficial impact on urban climate regimes with measurable reductions in air and land surface temperatures. Broad implementation of green infrastructure is a sustainable solution to improve the urban climate, enhance heat and greenspace equity, and increase resilience. [ABSTRACT FROM AUTHOR]

Depleting non-renewable resources and global warming motivated researchers to focus on passive cooling solutions to minimize the internal temperature of buildings. The benefits of using stacked coir mat and perlite in wet and dry conditions are tested for their cooling capacity compared to green roofs are explored in this research work. The benefits are quantified in terms of heat flow and temperature variations in a field experiment, and they are compared to a conventional bare roof in a tropical region in the Indian subcontinent (8.9142o N, 76.632o E). The heat transfer to the inside of the roof for dry coir mat paved, stacked coir mat and perlite bed, stacked wet coir mat and wet perlite bed, and extensive green roof system with coir mat as retaining layer are reduced by 38.43%, 63.21%, 55.3% and 56.97% respectively. This study evaluated the evaporative cooling capacity of wet coir mat and wet perlite, which have given almost near cooling capacity of green roof for 24 h. Considering its low maintenance and low initial cost, the usage of the stacked coir fibre mat with perlite shows a compatible reduction in heat transfer through the roof slab as that of the green roof. The coir insulation with perlite will undoubtedly reduce the energy requirement for heating ventilation and air conditioning (HVAC) systems to a greater extent. [ABSTRACT FROM AUTHOR]

[Display omitted] • Spatial heat accumulation patterns under air-conditioning anthropogenic heat. • Quantifying impacts of vertical temperature distribution on energy consumption. • Quantifying impacts of horizontal temperature distribution on pedestrian comfort. • The maximum disparity of tiered cooling energy consumption was 6.3 W/m2. • Parallel wind and cross arrangement of outdoor units promote heat dissipation. The overheated urban environment has drastically increased air-conditioning (AC) usage, which induces extensive heat emissions from outdoor units. This phenomenon is more adverse in high-density residential areas as the air-conditioning anthropogenic heat (ACAH) would further cause localized heat accumulation in canyons, negatively impacting AC energy consumption and residents' comfort. While previous research has explored the impact of ACAH on urban canyons, there is a lack of studies that systematically investigate the pattern, impacts, and mitigations of ACAH at a refined scale in high-density residential areas. This study aims to investigate the temperature distribution under ACAH and quantify its impact on cooling energy consumption and pedestrian thermal discomfort. High-density residential areas were categorized by different heights of buildings and directions of outdoor unit placement. Numerical simulations were conducted to study ambient temperature distribution. Results showed that the worst heat accumulation was at the windward position of the AC outdoor unit, and the outdoor temperature on the middle floor was 2.3 °C higher than that on the upper floor, resulting in a higher energy consumption of 6.3 W/m2. The worst case with taller windward buildings caused 55 % of the pedestrian areas to be more uncomfortable. Mitigation strategies were also proposed from multiple perspectives, including heat source optimization (e.g., cross-layout of AC outdoor units) and offering subsidies for AC electricity consumption gaps. The study provides a systematic research perspective on spatial heat accumulation patterns in high-density residential areas, which is instructive for mitigating urban warming and promoting sustainable urban development. [ABSTRACT FROM AUTHOR]

Urban heat island (UHI) effect has become a main urban environmental problem in megacities. To express the UHI effects more meaningfully and provide scientific basis for heat mitigation and urban planning, both field measurements and numerical simulations were conducted in Xi'an City, China. Three typical urban local climate zones (LCZs) with close geographical locations—high-rise/low-rise residential areas (LCZ4/6) and urban parks (LCZA)—were chosen to investigate thermal environments in vertical spaces. It was found that U H I L C Z 6 / 4 − L C Z A could reach 1.2/2 °C during the daytime and 0.3/0.7 °C in the night at screen-level height. In particular, temperature inversions were found in residential areas during the daytime, which led to an increase in the UHI intensity at certain heights. To investigate means to improve the thermal environment of residential areas, numerical simulations were carried out to test the influence of cool roofs and cool facades. It was found that the daytime air temperatures could be reduced by 0.2 °C and 0.4 °C after adopting high-reflectance roofs and facades in high-rise residential area at screen-level height, respectively. In addition, the implementation of cool facades also affected the air temperature profiles and atmospheric conditions, leading to the disappearance of temperature inversions and complicated stratification, and providing more evident cooling effects at certain heights. The findings of this study provide new insights into thermal environments of urban zones with different structures and have practical importance for urban UHI mitigation. • Significant UHI exists between different urban LCZs in the same neighborhood. • Temperature inversions occur in residential areas in the daytime at certain height. • The atmosphere in residential areas exhibit complex stratification in the daytime. • Cool roofs and facades are effective to reduce the air temperature. • Cool facades also affect the air temperature profiles and atmospheric conditions. [ABSTRACT FROM AUTHOR]

Exposure to heat is a major health concern to urban populations. Cities aim to reduce outdoor thermal stress by adapting the built environment, but the spatial heterogeneity within cities makes it difficult to establish universal mitigation strategies. We present a methodology that identifies the hottest neighbourhoods in a city and links them to underlying patterns in urban form and function, to derive heat mitigation measures for individual neighbourhoods according to their characteristics, mitigation potential, and average surface temperature. The method applies k -means clustering and is applicable to any city using available datasets on surface cover and building morphology, as well as globally available satellite measurements of surface temperatures. Here, we present a heat-mitigation analysis for the city of Zurich. The clustering differentiates seven neighbourhood types, including two types of residential areas, modern neighbourhoods with high-rise buildings, historical districts, and industrial zones. The hottest temperatures are in neighbourhoods with extensive impervious ground cover such as railway tracks and airport parking. Surface temperatures strongly correlate with impervious surface cover and vegetation cover for all neighbourhoods, with building cover only for non-industrial built neighbourhoods, and with sky-view factor for all neighbourhoods except those with large vegetation cover. Historical, modern, and industrial neighbourhoods are particular heat-prone, and increasing vegetation for evaporative cooling is a suggested mitigation strategy for all. Modern and industrial areas could benefit from shading through increase of tree cover, while historical centres may adapt vertical greening as suitable heat mitigation strategy. • A clustering based on morphology data is used to identify unique neighbourhoods. • These clusters are linked to observed local temperatures. • Applying the method in Zurich results in seven clusters of different neighbourhoods. • Based on these clusters, localised strategies for heat mitigation are derived. [ABSTRACT FROM AUTHOR]