Urban tree planting has the potential to reduce urban heat island intensity and building energy consumption. However, the heterogeneity of cities makes it difficult to quantitatively assess the ...integrated impacts of tree planting and street layouts. Scaled outdoor experiments were conducted to investigate the influence of tree plantings on wind and thermal environments in two-dimensional (2D) north-south oriented street canyons with various aspect ratios (building height/street width, AR = H/W = 1, 2, 3; H = 1.2 m). The effects of tree species with similar leaf area index (C. kotoense, big crown; C. macrocarpa, small crown), tree planting densities (ρ = 1, 0.5), and arrangements (double-row, single-row) were considered.
Vegetation reduces pedestrian-level wind speed by 29%–70%. For ρ = 1 and single-row arrangement, C. kotoense (big crown) has a better shading effect and decreases wall and air temperature during the daytime by up to 9.4 °C and 1.2 °C, respectively. In contrast, C. macrocarpa (small crown) leads to a temperature increase at the pedestrian level. Moreover, C. kotoense raises the air and wall temperature of the upper urban canopy layer and increases the street albedo during the daytime because of the solar radiation reflected by trees. C. kotoense/C. macrocarpa produces the maximum daytime cooling/warming and nighttime warming of air temperature when H/W = 2 owing to its weaker convective heat transfer. When H/W = 3, the building shade dominates the shading cooling and tree cooling is less significant. When ρ = 1, double-row trees (C. kotoense) reduce wall and air temperatures by up to 10.0 °C and 1.0 °C during the daytime. However, reducing ρ from 1 to 0.5 weakens the capacity of daytime cooling by C. kotoense and the warming effect by C. macrocarpa. Our study quantifies the influence of tree planting and aspect ratios on the thermal environment, which can provide meaningful references for urban tree planting and produce high-quality validation data for numerical modeling.
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•Scaled outdoor experiments are tested for tree impacts in streets (H/W = 1–3, H = 1.2 m).•Tree plantings may reduce the pedestrian-level wind speed by 29%–70%.•Species with big crown get better cooling effect than small one in the daytime.•Tree planting density of ρ = 0.5 (less dense) produces higher T than ρ = 1 (denser).•Trees reduce (raise) air-wall T below (above) them due to solar shading/reflection.
In cities, vegetation temperature is important for quantifying water use, microclimates, and water and energy fluxes, as demonstrated by urban climate models and in situ studies. Remote sensing is ...capable of observing land surface temperatures (LST) across a city; however, its ability to quantify vegetation canopy temperatures is limited because of LST variability resulting from urban surface heterogeneity, differences in vegetation fraction and non-vegetated material, and the coarse resolution of available thermal imagery. This study is a large-scale analysis of urban surface composition and temperature variability across the Los Angeles, USA, metropolitan area (4466 km2). Sub-pixel fractions of two plant functional types (tree and turfgrass) and four urban materials (impervious surface, commercial roof, non-photosynthetic vegetation, and soil) were quantified using hyperspectral imagery (Airborne Visible/Infrared Imaging Spectrometer). Fractional cover gradients of plant types and non-vegetated materials were developed using 1.7 million pixels, from which we modeled LST changes using simultaneously collected thermal imagery (MODIS-ASTER Airborne Simulator). Vegetation LST variability was mapped by subtracting modeled LST from observed LST and investigated relative to building density and vegetation management. Overall, LST varied significantly among plant functional types and urban material types. Across heterogeneous mixtures, LST and vegetation fraction exhibited a negative, linear relationship, with the slopes of LST change showing significant differences between trees and turfgrass. The map of vegetation LST variability had a standard deviation of 3.5 °C, indicating significant variability across Los Angeles independent of vegetation type or fractional cover. Building density was observed to affect tree and turfgrass LST differently, while a negative relationship was observed between vegetation LST and irrigation (R2 = 0.55). Our results show that an LST signal of vegetation function, distinct from that of vegetation fractional cover, can be observed and modeled at city-scales in fractional mixture analysis, indicating potential for improved understanding of urban microclimates.
•We mapped 6 sub-pixel classes, including tree and turf, across Los Angeles (4466 km2).•Tree cover had a smaller effect on surface temperature than did turfgrass cover.•Mixed pixel temperature depended on both vegetation type and non-vegetated material.•City-wide canopy temperature variability was correlated with irrigation and income.•Building density affected tree temperatures more than it affected turf temperatures.
Although the urban heat island (UHI) phenomenon is more commonly studied in summer, its influence is also important in winter. In this study, the authors focused on the winter UHI in Ljubljana ...(Slovenia) and its impact on the urban population, as well as in comparison with a UHI study from 2000. Through a combination of mobile and stationary temperature measurements in different parts of the city, the winter intensity of the UHI in Ljubljana was studied in a dense spatial network of measurements. It was found that the intensity of the winter UHI in Ljubljana decreases as winters become warmer and less snowy. The results showed that the winter UHI in Ljubljana intensifies during the night and reaches the greatest intensity at sunrise. During the winter radiation type of weather, the warmest part of Ljubljana reaches an intensity of 3.5 °C in the evening. In total, 22% of the urban area is in the evening UHI intensity range of 2–4 °C, and 65% of the urban population lives in this range. In the morning, the UHI in Ljubljana has a maximum intensity of 5 °C. The area of >4 °C UHI intensity covers 7% of the urban area, and 28% of the total urban population lives in this area. Higher temperatures in urban centers in winter lead to a longer growing season, fewer snow cover days, lower energy consumption and cold stress, and lower mortality from cold-related diseases compared to the colder periphery.
A cidade de Três Lagoas nos últimos anos teve seu crescimento acelerado com a industrialização e a implantação da silvicultura de eucalipto, intensificando sua urbanização e trazendo os problemas ...ambientais decorrentes desse crescimento. Com base nisso, o presente estudo teve por objetivo a análise de dados climatológicos noturnos de Três Lagoas/MS, nos meses de fevereiro a junho de 2019, embasado na teoria do Sistema Clima Urbano (S.C.U.) de Monteiro (1975), e utilizando-se da classificação da intensidade e magnitude da ilha de calor de Fernández García (1996). Os procedimentos metodológicos adotados, foram a mensuração da temperatura do ar em 2 pontos fixos (centro urbano e rural próximo), no período de 02 de fevereiro a 30 de junho de 2019, nos horários das 20 h às 06 h, e seu posterior tratamento em softwares específicos. Os resultados evidenciaram que durante o período analisado, observou-se a formação de ilhas de calor noturnas em todos os meses, sendo de até 10,7ºC em fevereiro, 5,8°C em março, 6,2ºC em abril, 7,1ºC em maio e 7,7ºC em junho. Tais resultados demonstraram ilhas de calor classificadas como de muito forte magnitude. Deste modo, acredita-se que o presente estudo pode subsidiar ações de planejamento urbano para tornar as cidades e os assentamentos humanos inclusivos, seguros e resilientes. Além disso, frisa-se que medidas de mitigação devem ser adotadas pelo poder público, pois a cidade localiza-se numa posição geográfica que lhe impõe a tropicalidade, ambiente natural de altas temperaturas e a urbanização sem planejamento adequado pode intensificar a sensação de desconforto térmico para a população.
Ces dernières années, la ville de Três Lagoas a connu une croissance accélérée en raison de son industrialisation récente et de la plantation d’eucalyptus, intensifiant alors le processus d’urbanisation et entrainant des problèmes environnementaux. Cette étude a pour objectif d’analyser les données climatologiques nocturnes de Três Lagoas/MS, entre les mois de février et juin 2019, dans la perspective de la théorie du Système Climat Urbain de Monteiro (1975), grâce à la classification de l’intensité et de la magnitude des ilots de chaleur de Fernandez Garcia (1996). La méthodologie adoptée a consisté en des mesures de température de l’air en 2 points fixes (centre urbain et rural proche), du 02 février au 30 juin 2019, de 20h à 6h, suivi de leur traitement au sein de programmes spécifiques. Les résultats ont permis d’identifier la formation d’ilots de chaleur nocturne, sur l’ensemble de la période étudiée, en raison de 10,7°C en février, 5,8°C en mars, 6,2°C en avril, 7,1°C en mai et 7,7°C en juillet. Ces résultats démontrent des ilots de chaleurs de magnitudes élevées. Ainsi, le présent travail peut contribuer à orienter les actions d’aménagement urbain afin de rendre les villes et hameaux plus inclusifs, sûrs et résilients. De plus, des moyens en faveur de la mitigation doivent être engagés par le pouvoir public, de par la localisation géographique même de la ville où la tropicalité y est imposée, contenant des environnements naturels à fortes températures et une urbanisation sans aménagement territorial adapté, pouvant intensifier la sensation d’inconfort thermique de la population.
Três Lagoas, in the state of Mato Grosso do Sul (MS) and like other Brazilian cities, has seen its growth accelerated in recent years with industrialization and the implementation of eucalyptus forestry, intensifying its urbanization and bringing the problems arising from this growth. The present study aims at analyzing daily nocturnal climatological data from Três Lagoas from February 2nd to June 30th, 2019, based on the theory of the Urban Climate System (S.C.U.) by Monteiro (1975). We use the intensity classification from the heat island of Fernández García (1996). The methodological procedures adopted were the daily measurement of air temperature at 2 fixed points (urban center and nearby rural), from 8 pm to 6 am, and its subsequent treatment in specific software. The results show that during the analyzed period, the formation of nocturnal heat islands was observed in all months, being up to 10.7ºC in February, 5.8ºC in March, 6.2ºC in April, 7.1ºC in May and 7.7ºC in June. Such results show the classification of heat islands of very strong magnitudes. Thus, it is believed that the present study can support urban planning actions to make cities and human settlements more inclusive, safer, and more resilient. In addition, it is emphasized that mitigation measures must be adopted by the public authorities. Três Lagoas, which is in a geographical position that imposes tropicality, a natural environment of high temperatures and urbanization. Lacking adequate planning can intensify the feeling of thermal discomfort for a population.
In 2016, the Kuwait Mitribah weather station recorded a scorching 53.9 degrees Celsius, among the highest temperatures ever recorded on earth. Today, temperatures in Kuwait frequently exceed 50 ...degrees Celsius during the summer, accompanied by a host of extreme weather events such as severe droughts, dust storms, and floods. These climate challenges threaten and transform Kuwait’s social and ecological landscape. To address these pressing issues, this paper adopts an urban climate justice framework, emphasizing the right to the city, recognition justice, and advocating for a climate-just city. Through this lens, we examine how climate change disproportionately affects Kuwait’s structurally vulnerable populations, particularly the majority non-citizen groups: the Bidoon (stateless) and low-wage migrant workers. This paper highlights the necessity of including marginalized groups in climate change discussions along with climate adaptation and mitigation policies. By examining the everyday urban lives of Kuwait’s non-citizen residents – including their struggles with access to civil and political rights; poor housing and labor conditions; and inequitable access to basic urban services, such as water, electricity and transport − this paper demonstrates how these factors significantly increase their vulnerability to the detrimental impacts of climate change. In highlighting the vulnerabilities of low-income non-citizens and advocating a shift to a climate-just city approach, this analysis aims to guide decision-makers in Kuwait and beyond. The impact of climate change, we contend, offers an opportunity to re-open debate about the fundamental rights and concepts of citizenship, belonging, community and justice.
Given increasing utility of numerical models to examine urban impacts on meteorology and climate, there exists an urgent need for accurate representation of seasonally and diurnally varying ...anthropogenic heating data, an important component of the urban energy budget for cities across the world. Incorporation of anthropogenic heating data as inputs to existing climate modeling systems has direct societal implications ranging from improved prediction of energy demand to health assessment, but such data are lacking for most cities. To address this deficiency we have applied a standardized procedure to develop a national database of seasonally and diurnally varying anthropogenic heating profiles for 61 of the largest cities in the United Stated (U.S.). Recognizing the importance of spatial scale, the anthropogenic heating database developed includes the city scale and the accompanying greater metropolitan area. Our analysis reveals that a single profile function can adequately represent anthropogenic heating during summer but two profile functions are required in winter, one for warm climate cities and another for cold climate cities. On average, although anthropogenic heating is 40% larger in winter than summer, the electricity sector contribution peaks during summer and is smallest in winter. Because such data are similarly required for international cities where urban climate assessments are also ongoing, we have made a simple adjustment accounting for different international energy consumption rates relative to the U.S. to generate seasonally and diurnally varying anthropogenic heating profiles for a range of global cities. The methodological approach presented here is flexible and straightforwardly applicable to cities not modeled because of presently unavailable data. Because of the anticipated increase in global urban populations for many decades to come, characterizing this fundamental aspect of the urban environment – anthropogenic heating – is an essential element toward continued progress in urban climate assessment.
•City-specific anthropogenic heating profiles are needed for urban climate modeling.•Diurnal and seasonal profiles of anthropogenic heating are developed for 61 US cities.•An extrapolation method for calculating international city profiles is introduced.
The urban context is often simplified or neglected in Building Energy Models (BEMs) due to the difficulties of taking accurately into account all the heat fluxes emanating from the environment. ...Oversimplifying the urban context can impact the accuracy of the BEM predictions. Nevertheless, several approaches can be used to allow for the impact of the urban environment on the dynamic behavior of a building, its heating and cooling demands, and thermal comfort. This state of the art review provides a critical overview of the different methods currently used to take into account the urban microclimate in building design simulations. First, both the microclimate and building models are presented, focusing on their assumptions and capabilities. Second, a few examples of coupling, performed between both modeling scales are analyzed. Last, the discussion highlights the differences obtained between simulations that take the urban context into consideration and those that simplify or neglect urban heat fluxes. The remaining scientific obstacles to a more effective consideration of the urban context impacting the BEMs are indicated.
•The local data produced by a selection of urban climate models (UCMs) are presented.•An analysis of how the urban context is taken into account in building energy models (BEMs) is given.•Several chaining or coupling strategies to link UCMs and BEMs are analyzed and compared.•Using local climate data leads to a noticeable impact on the thermal behavior of buildings.•Recommendations for better consideration of the urban context in BEMs are formulated.
The local climate zone (LCZ) system provides a universal classification mechanism for urban and natural landscapes and plays an increasingly important role in urban climate research. With the rapid ...development of various LCZ mapping methods, a thorough survey of the LCZ mapping literature is urgently needed to better understand current progress, challenges, and future directions. Accordingly, this study provided a comprehensive review of the LCZ mapping literature during 2012–2021, with a detailed analysis on literature statistics, research topics, LCZ cities, and active research groups. Furthermore, remote sensing (RS)-based LCZ mapping methods were elucidated from feature sets, classification units, training areas, classification algorithms, and accuracy assessment; geographic information system (GIS)-based LCZ mapping methods were elaborated from LCZ parameters, basic spatial units, classification algorithms, and accuracy assessment; and their combination methods were summarized from two typical integration strategies. Finally, several challenges and future directions for LCZ mapping were discussed. The topics include exploiting multi-source RS and GIS data, determining appropriate LCZ mapping unit sizes, acquiring high-quality LCZ ground truth data, improving LCZ classification algorithms, optimizing LCZ parameters and subclasses, exploring the transferability of LCZ models, conducting global interannual LCZ mapping, and expanding the application of LCZs. The research community can quickly obtain abundant information on the LCZ mapping literature, understand the frameworks of different LCZ mapping methods, and inspire new directions for future research.
•Progress, challenges, and prospects for LCZ mapping are systematically reviewed.•Frameworks of RS- and GIS-based LCZ mapping methods are elaborated.•Data sources, mapping unit sizes, classification algorithms, and validation strategies are analyzed.•Deep learning models, domain adaption methods, and benchmark datasets improve LCZ mapping.•GEE, deep learning, crowdsourcing, and collaboration facilitate global interannual LCZ mapping.
•LCZ mapping is considered as remote sensing scene classification instead of pixel-based classification to fully exploit the urban environment context.•A convolutional neural network integrating ...residual learning and the Squeeze-and-Excitation block is proposed for LCZ mapping.•Image sizes of 32×32 to 64×64 corresponding to 320×320 to 640×640 m2 areas are found suitable for LCZ mapping depending on the region.•LCZ maps are generated for fifteen cities in China.
China, with the world’s largest population, has gone through rapid development in the last forty years and now has over 800 million urban citizens. Although urbanization leads to great social and economic progress, they may be confronted with other issues, including extra heat and air pollution. Local climate zone (LCZ), a new concept developed for urban heat island research, provides a standard classification system for the urban environment. LCZs are defined by the context of the urban environment; the minimum diameter of an LCZ is expected to be 400–1,000 m so that it can have a valid effect on the urban climate. However, most existing methods (e.g., the WUDAPT method) regard this task as pixel-based classification, neglecting the spatial information. In this study, we argue that LCZ mapping should be considered as a scene classification task to fully exploit the environmental context. Fifteen cities covering 138 million population in three economic regions of China are selected as the study area. Sentinel-2 multispectral data with a 10 m spatial resolution are used to classify LCZs. A deep convolutional neural network composed of residual learning and the Squeeze-and-Excitation block, namely the LCZNet, is proposed. We obtained an overall accuracy of 88.61% by using a large image (48×48 corresponding to 480×480 m2) as the representation of an LCZ, 7.5% higher than that using a small image representation (10×10) and nearly 20% higher than that obtained by the standard WUDAPT method. Image sizes from 32×32 to 64×64 were found suitable for LCZ mapping, while a deeper network achieved better classification with larger inputs. Compared with natural classes, urban classes benefited more from a large input size, as it can exploit the environment context of urban areas. The combined use of the training data from all three regions led to the best classification, but the transfer of LCZ models cannot achieve satisfactory results due to the domain shift. More advanced domain adaptation methods should be applied in this application.
Due to its concave topography, the climate in the Rouen region is affected by the impact of urbanization. The urbanized area occupies the bottom of the Seine Valley and extends onto slopes and ...plateaus. These topographic conditions contribute to the formation of well-differentiated local climates. To better understand the urban heat island, an expeditionary measurement campaign was carried out from 25 June to 11 August 2020. This campaign is based on the knowledge of the spatial distribution of temperatures in the city. These measurements were carried out according to different profiles and a specific programme. During this period, the region was affected by three heatwaves.. In this study, we present the results regarding the air temperatures obtained on 25 June 2020. The study also relies on the analysis of “Landsat 8” channel 11 satellite images, with a spatial resolution of 30 m to define surface temperatures. The results obtained during the measurement campaign show the importance of the differences between vegetated and built spaces. They also highlight hotspots (at traffic intersections and on main transport corridors – boulevards). The results obtained from the processing of satellite images show significant temperature differences between the industrial area and the rest of the city. There is an important thermal contrast between green spaces and asphalt squares in the city centre. There is a thermal lag between the “west” plateau, Cailly Valley, and the rest of the city.
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