Urban Heat Island Effect Research Papers (original) (raw)

The cities are responsible up to 75% of energy consumptions and 80% of CO2 emissions. The European Performance of Buildings Directives and the urban regulations are going towards the reduction of the energy consumptions and the minimization of the land’s use. In this scenario the innovative methodology, IMM® (Integrated Modification Methodology), has been applied in order to achieve the energy standards of net zero energy districts of four Eixample courtyards in Barcelona. The city is considered as a complex system composed by heterogeneous parts influenced each other. The multi-criteria process aims to transform a consolidated urban context into a more efficient and sustainable one. The opmization of solar potential and the design of new green areas give relevant benefits in terms of energy efficiency and quality of urban environment.

- by Danilo Palazzo
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- ESP, Energy efficiency, Sustainable Urban Design, Urban Heat Island Effect

O clima de Viçosa começou a ser investigado, a partir da investigação doutoral desenvolvida
por Fialho (2009), cujo objetivo era analisar o campo termohigrométrico na relação cidade
e campo cidade, de acordo com os diferentes tipos de usos da terra, visando diagnosticar
a ocorrência do fenômeno ilha de calor ao longo das estações do ano. Corroborando a
ideia, o presente trabalho faz uma análise da área central e periférica do centro comercial da
cidade, a partir da coleta de dados da temperatura média do ar (TmºC ) e umidade média
relativa do ar (URm%) de 10 pontos instalados nestas áreas durante 26 dias no outono
e 26 dias no inverno de 2014. Devido ao elevado número de dados, optou-se pelo uso
de médias. Foram obtidas fotografi as hemisféricas dos pontos para o cálculo do Fator de
Visão do Céu (FVC) ou Sky View Factor (SVF). De posse dos índices de TmºC e URm%
foram feitas correlações entre eles e o valor do FVC de cada ponto por turno e horária,
a fi m de, estabelecer o quanto o campo térmico é infl uenciado pela geometria urbana.
Observa-se que o período do inverno apresentou melhor correlação entre TmºC e FCV,
porém há uma heterogeneidade em relação aos dados, o que impossibilita predizer se a
geometria urbana é responsável pelo aquecimento e/ou resfriamento da área estudada
e reforça a ideia de que o sítio tem um papel importante na confi guração do campo
termohigrométrico de Viçosa-MG.
Palavras-chave: Clima Urbano. Fator de Visão do Céu. Sazonalidade. Viçosa-MG.

- by Edson Fialho
- •
- Climate Change, Urban Climate, Urban Heat Island Effect

Abstrak Alun-alun merupakan fasilitas publik yang berfungsi sebagai ruang terbuka sekaligus ruang sosial. Memahami permasalahan alun-alun merupakan prasyarat sebelum meningkatkan kualitasnya. Pene-litian ini bertujuan ingin mengetahui permasalahan alun-alunyang dipersepsi oleh masyarakat dan identifikasi pertimbangan pengunjung dalam pemilihan tempat di alun-alun. Selain itu penelitian ini juga mengungkap hubungan antara permasalahan di alun-alun dengan pemilihan tempat dari sudut pandang pengunjung. Untuk mencapai tujuan, dilakukan penelitian dengan metode kualitatif. Data diperoleh dari kuesioner yang disebarkan secara online dan dianalisis menggunakan content analysis. Hasil penelitian menunjukkan bahwa panas merupakan permasalahan utama di alun-alun, masalah lain yaitu kotor dan pengelolaan yang kurang baik. Tempat yang paling banyak dipilih adalah tempat yang teduh, tempat untuk duduk, dan fasilitas umum. Permasalahan yang dirasakan pengunjung memiliki korespondensi terhadap pemilihan tempat di alun-alun.

- by Azzahra M Firdausah
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- Public Space, Urban Heat Island Effect, Themal Comfort

Contemporary cities experience poor urban environment conditions. High densities have resulted in the genesis of the Heat Island effect that under the undeniable climate change will only get intensified. Reducing the ambient temperatures and improving the microclimate inside the urban fabric appears to be urgent. This paper examines the parameters affecting the urban microclimate. Through the analysis of a typical urban block and the process of fieldwork in the city centre of Thessaloniki, urban geometrical characteristics and environmental conditions are identified. Possible design guidelines aiming to rehabilitate the urban block are also evaluated.

In order to achieve the ambitious Sustainable Development Goal #11 (Sustainable Cities and Communities), an integrative approach is necessary. Complex outcomes such as sustainable cities are the product of a range of policies and drivers that are sometimes at odds with each other. Yet, traditional policy assessments often focus on specific ambitions such as housing, green spaces, etc., and are blind to the consequences of policy interactions. This research proposes the use of remote sensing technologies to monitor and analyse the resultant effects of opposing urban policies. In particular, we will look at the conflicting policy goals in Amsterdam between the policy to densify, on the one hand, and, on the other hand, goals of protecting and improving urban green space. We conducted an analysis to detect changes in land-uses within the urban core of Amsterdam, using satellite images from 2003 and 2016. The results indeed show a decrease of green space and an increase in the built-up environment. In addition, we reveal strong fragmentation of green space, indicating that green space is increasingly available in smaller patches. These results illustrate that the urban green space policies of the municipality appear insufficient to mitigate the negative outcomes of the city's densification on urban green space. Additionally, we demonstrate how remote sensing can be a valuable instrument in investigating the net consequences of policies and urban developments that would be difficult to monitor through traditional policy assessments.

- by Mendel Giezen and +2
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- Remote Sensing, Environmental Sustainability, Urban Heat Island Effect, Urban Densification
- by Nasrin Aghamohammadi
- •
- Geography, Urban Studies, Air Pollution and Health Effects, Urban Climate

The modelling of the urban microclimate, in particular the phenomenon of the Urban Heat Island (UHI), is becoming increasingly essential for city planning and urban design. The phenomenon analysis is henceforth possible thanks to the increase in computational power, the link between simulation tools and urban databases, which allow to represent explicitly the characteristics of the urban microclimate and to better understand its effects, through the analysis and evaluation of the different impacts of the urban climatic or anthropogenic contributors. However, the choice of the scale of the study depends on the accuracy of the modelling approaches, the capacities of calculation and the availability and reliability of the data. The contribution aims to highlight the phenomenon of the UHI based on a bibliographic study of the latest research on this topic in Maghreb cities and the different strategies for adapting them to climate change and for improving their resilience.

While urban form affects building energy consumption, the pathways, direction and magnitude of the effect are disputed in the literature. This paper uses a unique dataset to examine the effect of urban form on residential electricity consumption in Ningbo, China. Using survey and utility bill data of 534 households in 46 neighborhoods in the city, we model the electricity use of households using a multi-level regression model. We find that neighborhood street configuration and tree shade are important in controlling residential electricity consumption and, consequently, greenhouse gas emissions. Our results suggest that seasonality and dwelling type condition the effect of neighborhood densities on electricity consumption. Neighborhood density is associated with household electricity consumption in summer months, while there is no such association in winter months. As neighborhood density increases, households in slab and tower apartments in dense urban neighborhoods consume more electricity in summer months, which can be partly explained by exacerbated heat island effect. Interestingly, the neighborhood density is negatively associated with summer electricity consumption for single-family houses, suggesting that the effect of neighborhood density is different for different types of dwelling units.

- by Chaosu Li
- •
- Urban Planning, Energy efficiency, Multilevel modelling, Urban Heat Island Effect

The urban heat island (UHI) phenomenon is a significant worldwide problem caused by rapid population growth and associated urbanization. The UHI effect exacerbates heat waves during the summer, increases energy and water consumption, and causes the high risk of heat-related morbidity and mortality. UHI mitigation efforts have increasingly relied on wisely designing the urban residential environment such as using high albedo rooftops, green rooftops, and planting trees and shrubs to provide canopy coverage and shading. Thus, strategically designed residential rooftops and their surrounding landscaping have the potential to translate into significant energy, long-term cost savings, and health benefits. Rooftop albedo, material, color, area, slope, height, aspect and nearby landscaping are factors that potentially contribute. To extract, derive, and analyze these rooftop parameters and outdoor landscaping information, high resolution optical satellite imagery, LIDAR (light detection and ranging) point clouds and thermal imagery are necessary. Using data from the City of Tempe AZ (a 2010 population of 160,000 people), we extracted residential rooftop footprints and rooftop configuration parameters from airborne LIDAR point clouds and QuickBird satellite imagery (2.4 m spatial resolution imagery). Those parameters were analyzed against surface temperature data from the MODIS/ASTER airborne simulator (MASTER). MASTER images provided fine resolution (7 m) surface temperature data for residential areas during daytime and night time. Utilizing these data, ordinary least squares (OLS) regression was used to evaluate the relationships between residential building rooftops and their surface temperature in urban environment. The results showed that daytime rooftop temperature was closely related to rooftop spectral attributes, aspect, slope, and surrounding trees. Night time temperature was only influenced by rooftop spectral attributes and slope.

- by Qunshan Zhao and +1
- •
- Sustainable Urban Environments, LiDAR, Urban Heat Island Effect, Landscaping

Vertical greenery systems (VGSs) are becoming a common architectural element in urban environments. In addition to the aesthetics of VGSs, impacts on building's energy demand and heat island mitigation in cities has been identified. In the present study, experimental results of thermal response and properties of VGSs with vertical leaf area index (LAIV) equal to 6.1 and 7.2 are presented. Experimental results show that VGSs can impact up to 34 K lower surface temperatures of a façade, while maintaining air temperatures in the VGSs' canopies close to ambient temperatures. Properties of the VGSs were used as a basis as well as an input for a detailed mathematical model of the thermal response of a building envelope with a VGS. The validated mathematical model was used for parametrical analysis of the impact of thermal resistance of a building envelope on the cooling potential of the VGSs. The results show that the cooling effect is more significant for less insulated façades, and that a VGS can be modelled as an independent urban cooling element. Finally, a parametrical model of the latent heat flux of a VGS was developed and can be used as a boundary condition in urban heat island studies.

Keynote presentation based on my most recent book, "Street Art and the Environment".

- by Peter Bengtsen
- •
- History, Cultural History, Sociology, Political Sociology

... Laura Kleerekoper a , Corresponding Author Contact Information , E-mail The Corresponding Author , Marjolein van Esch a , E-mail The Corresponding Author , Tadeo Baldiri Salcedo b , E-mail The Corresponding ... It forms a transit area... more

- by Laura Kleerekoper
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- Architecture, Urban Design, Urban Heat Island Effect, Human Thermal Comfort

Cool roof is a simple yet powerful technology used for temperature control of buildings and urban areas. To understand the effectiveness of cool roof application in Indian cities and to understand the existing policies, codes and practices being carried out in India, a review of the existing conditions is done. This paper also studies various best practices from around the world and suggests the lessons India can learn from these global examples. There have been several studies done to prove the applicability and effectiveness of cool roofs in Indian conditions. In line with the country's National Cooling Policy, there are a few state and city level initiatives for the wider application of cool roof technology. Several green rating systems in India highlight cool roof as an energy saving strategy. There is a code specific to energy conservation in buildings with cool roofs requirement. However, at this point this code is not mandatory for majority of the Indian states. As learnt from the global examples, mandatory codes, policies, incentives, tax credits, and other such similar measures have a higher outreach for this technology adoption. India would benefit greatly from updating the existing policy framework to include cool roof related interventions, supporting focused research in the area and maximizing ground implementation through short and long term strategies. A consortium of scientific partners, industry partners, policy makers, along with the NGOs and volunteers working towards a common goal will make wider adoption and visible reduction in Urban Heat Island a reality.

- by Janmejoy Gupta and +1
- •
- Urban Geography, Urban Planning, Urban Heat Island Effect, Urban heat island

In recent years, several studies have examined the Lisbon urban climate. A central conclusion is the existence of a nocturnal urban heat island (mean ΔTu−r = 2.5 °C). The aim of this paper is to summarise several attempts carried out in the last decade to interpolate nocturnal air temperatures across Lisbon, in order to be able to draw thermal maps as accurately as possible. This study refers only to clear nights. Stepwise multiple regression and a Geographic Information System were used to model the relation between air temperature and parameters related to land-use and topography. The different regression models (coefficients of determination between 0.68 and 0.92) show that canopy layer air temperature depends on sky-view factor, building height and percentage of built-up area, but also to a great extend on mesoclimatic geographic factors such as altitude, topography and distance from the Tagus River. Examples of four frequently encountered nocturnal air temperature patterns are presented, each corresponds to a different weather type. This method employed could prove useful in drawing climatic maps that may be of use in master plans of urban municipalities.

A growing majority of the global population now resides in urban areas. In 2014 urban populations made up approximately 54 % of the world’s population and by 2050 this urban proportion was expected to rise to over 66 %. Rapid urbanization leads to changes in the absorption and reflection of solar radiation, and thus the surface energy balance. Urban heat island (UHI) describes the phenomenon that temperatures are higher in urban areas compared to surrounding rural areas. UHI effect means that air temperatures in urban areas are on average 2–5◦C higher, and in some cases more than 10 ◦C higher, than those in surrounding non-urban areas. Increasing temperatures in the urban area may lead to significant ecological and social consequences. Trees and green spaces contribute considerably to the improvement of the urban climate and to the UHI mitigation. These spaces have been proposed as one of the most important approach to mitigate negative consequences of increased temperatures resulting from UHI. In this study we review the benefits of plants in urban spaces affect thermal comfort such as solar radiation, temperature of exterior surfaces, air temperature, air humidity and wind speed for to destroy the urban heat island.

- by Ahmet Akay
- •
- Landscape Ecology, Geography, Landscape Architecture, Environmental Sustainability

Abstract The concept of the sustainable development has been used in diverse field at different levels. But there are varied opinion about the measurability and possible applications. Thus the study is carried out to have an insight into the concept of sustainable development and its application in the urban context with the help of measurability. Various measurement tools and indicators are studied to know the available approaches, protocol and framework at different levels based on the three pillars of sustainability - environmental, social and economical dimensions. The paper classifies the methods of measurement in three categories a) concept level (broad); b) advanced (which requires detail database) and; c) context (application specific). It was observed that most of the research work on measurability is done in developed nations. So, at the end the paper tries to understand the problems in the Indian context for applying the theory of sustainability into practice.

Land Surface Temperature (LST) is one of the key environmental parameters affected by land cover change. Lagos State has been experiencing an increase in surface temperature due to growing areas of impervious surfaces caused by anthropogenic urban sprawl. While the change in LST has been established, its continuous monitoring and relationship with continuing Land Cover (LC) changes have become imperative for appropriate management and policy actions. This study investigated the effect of land cover change on LST in the rapidly urbanising Lagos metropolis. Using spatio-temporal Landsat imageries with their thermal bands and ancillary data, land cover and LST changes were assessed from 1984 - 2015. The spatial patterns of LST and LC were derived to examine the response of LST to urban growth. Findings confirmed urban sprawl in previously rural areas northward of the metropolis in LGAs such as Ikorodu, Kosofe and those fringing the state’s border with Ogun State. This also confirmed new growth areas as occurring west of the metropolis in Amuwo-Odofin LGA. The results further showed that the rapid urbanisation in Lagos metropolis has altered the surface thermal environment as indicated by increased LST. Built-up area and bare land accounted for the highest increase in LST (as high as 1.5℃ in some areas) while wetlands and other vegetated areas played a vital role in moderating the surface temperature in areas they still occupy. This provides reasonable evidence for the appropriate authorities to institute requisite policies and actions towards moderating urban sprawl while ramping up the development of urban green infrastructure to counter global warming.

Şehirler yapıları gereği doğal çevreden daha farklı ısınma ve soğuma karakterine sahip olmaktadır. Bu farklılık sonucunda ortaya çıkan yapıya Şehir Isı Adası(ŞIA) denilmektedir. ŞIA'lar meteorolojik verilerin analizi sonucunda ortaya koyulabilmektedir. Bu analizlerin yapılması için şehir içi istasyonlar ve kırsal istasyonlar arasında kıyas yapılması teorik olarak yeterlidir. Akademik araştırmalar sonucunda şehirlerin ısınma ve soğuma karakterini tanımlamak için Yüzey Isı Adası(YIA) kavramı da ortaya çıkmıştır. YIA ve ŞIA kavramları arasındaki temel fark gözetilmeden bazı yayınlarda YIA kavramı ŞIA kavramı yerine de kullanışmış ve bu kullanımdan dolayı hatalı sonuçlar elde edilmiştir. Bu iki kavram arasındaki nüansların belirlenmesi amacıyla her iki kavramın da İstanbul örneğindeki sonuçları araştırılmış ve bu sonuçlar üzerinden farklar ortaya koyulmuştur. Bu amaç doğrultusunda İstanbul İli'nin Meteorolojik kayıtları ile Landsat 8 uydusundan elde edilen görüntüle açık kaynak kodlu Coğrafi Bilgi Sistemleri(CBS) kullanılarak analizler yapılmıştır. Analizler sırasında PostgreSQL veri tabanı, QGis 3.4 ve 2.18 CBS uygulaması ve çeşitli uzaktan algılama yazılımları kullanılmıştır.

- by Mustafa Kağan Özbilge
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- Geography, Physical Geography, Environmental Science, Remote Sensing

Noah LSM/UCM/WRF Putrajaya Land use and land cover change Urban heat islands 2 m surface temperature a b s t r a c t Land use and land cover changes, urban warming and changes in urban climate variables of a given location are some of the profound signatures of urbanisation. Putrajaya is a planned city built from a formerly vegetated farm and agricultural lands to a modern urban city. This study aims to investigate the chronological local urban climate changes that have taken place over a decade (1999–2011) of urbanisation using the NCAR Weather and Research Forecasting (WRF) model coupled to a numerically proven land surface and urban canopy model (NOAH LSM/UCM). Up-to-date and accurate land cover dataset of the region implemented for each year is derived from LANDSAT images. Model results are evaluated against a network of observational studies in the region. 2-m air temperature, wind speed, relative humidity, planetary boundary layer height and urban warming of the area in each of the considered years are carefully examined. Solar radiation, urban surface induced variations in the urban surface energy balance components, and variations of the study area urban climatic variables are also investigated. Model results demonstrate good correlation and agreements with the observed data, with 2-m air temperature performance observed to be better relative to other variables evaluated. Results show that 2-m temperature of the area is increasing at the rate of 1.66 °C per decade, while the prevailing urban heat island intensity (UHII) of the area is $2.1 °C. The urban climate prognostic and diagnostic variables show good correlations with the urban surface modifications of the area from the original natural surfaces, except for wind speed which shows less variability to urbanisa-tion. Furthermore, formation of urban cool islands is also noticed for 1999, 2007, and 2011. Near-uniform net all-waves radiations of the different years experimented conform to tropical city low climatic variability. Finally, the thermal conditions of the area exhibit spatial and temporal variations heavily induced by urbanisation.

- by Kenobi Morris and +1
- •
- Urbanisation, Urban Heat Island Effect, Urban Climatology, Tropical Urbanism

Urban heat island (UHI) is significantly increasing in the urban cities of underdeveloped countries. Its rapid growth in past decades is due to the fast-growing population, and unplanned settlements. This study is conducted to understand the UHI using multispectral satellite images
in the summer and winter period of 2014-2019 as a case study in Kathmandu and Bhaktapur city. Land surface temperatures (LST), Urban Heat Island (UHI), Normalized Vegetation Index (NDVI), Normalized Difference Built-up Index (NDBI) were determined using thermal remote
sensing technique along with multispectral thermal imagery. The UHI values depicted in Kathmandu and Bhaktapur show a significant increase in the year 2019 as compared to 2014.
It signifies these cities need to concern about urban heat and must aware of communities and decision-makers to implement action to minimize this effect.

- by Pawan Thapa
- •
- Urban Heat Island Effect

With rapid urbanization, Dhaka, the capital of Bangladesh, is progressively falling short of sustaining outdoor life due to the Urban Heat Island (UHI) effects, which is one of the most documented phenomena of urban climate change. The UHI intensity inside and around Dhaka varies from 2.5°C to 7.5°C, which leads to additional demand on the urban energy resources for cooling. It is reported that 75% power consumption of the city is occurring to achieve comfortable thermal conditions. While currently, 34.3% of Bangladesh's population lives in urban areas, it is projected to increase to 56% by 2050, which will eventually worsen the UHI phenomenon. Dhaka possesses only 0.12 acres of greenery and open areas per one thousand people, while according to a recommendation from the National Recreation and Park Association between 6.25 and 10.5 acres of total open space per thousand is needed. Since the consequences of UHI are significant, the severity of the problem should be carefully examined and reported. Therefore, this study emphasizes a critical investigation of the features and factors of UHI affecting the outdoor thermal comfort of Dhaka city. Published scientific papers, governmental reports, and other national publications have been explored to conduct a systematic review to identify the major contributing factors of the UHI in the context of Dhaka. This paper identifies that rapid population migration to Dhaka, reduction of percentages of vegetation and green spaces in the land cover, and the unplanned dense urban development by altering the natural surfaces to impervious surfaces are some of the major contributing factors to the formation of the UHI phenomenon in Dhaka.

- by Tasneem Tariq
- •
- Green Infrastructure, Bangladesh, Tropics, Urban Heat Island Effect

The rapid urbanization and land-use/land-cover (LU/LC) changes have resulted in the unplanned and unsustainable growth of the Indian cities. This has resulted in a number of environmental issues such as escalating the urban heat island (UHI) intensity over the cities. Therefore, this study was designed to model and quantify the UHI dynamics of Mumbai city in response to the LU/LC change during 1991-2018 using temporal Landsat datasets. The result shows a significant decline in vegetation cover from 215.8 to 129.27 km 2 , while the built-up areas have almost doubled, i.e., from 173.09 to 346.02 km 2 in the Mumbai city during 1991-2018. As a consequence of this, a significant increase in the LST has been noticed in both urban heat island (UHI) and non-UHI zones. Although the areas under UHI zones have not increased significantly, the land surface temperature (LST) gap (difference between minimum and maximum LST) has declined in the Mumbai city from 30.04°C in 1991 to 20.7°C in 2018. Further, the minimum and mean LST over each LU/LC classes have also shown a significant increase. On the other hand, the regression analysis shows that the association between UHI and normalized difference built-up index (NDBI) has increased in the city, while the association of vegetation density (NDVI) and normalized difference bareness index (NDBaI) has declined in the city. The study can provide useful insights into the process of urban planning and policy makings for urban spatial planning and UHI mitigation strategies. Keywords Land-use/land-cover change Á Land surface temperature Á Urban heat island Á Vegetation and built-up density Á Mumbai city

تتناول الدراسة شدة الجزيرة الحرارية لمدينة المنصورة وتباينها الداخلي على المستوى المكاني والزمني، وعلاقة ذلك بالقصور الحراري وخصائصه. وقد اعتمدت الدراسة على الاستشعار من بعد بشكل رئيسي لمعالجة وتحليل المرئيات الفضائية بهدف استخلاص العمران الحضري آليا، والتعرف على أنماط الأسطح الأرضية بالمدينة وظهيرها، وحساب درجات الحرارة والألبيدو السطحي، واستخدام النماذج الرياضية المتقدمة لحساب القصور الحراري. وقد أظهرت الدراسة أن المواد والأسطح الحضرية في المنصورة تتسم بقصور حراري مرتفع عن الظهير الزراعي بنحو 7.3٪ في المتوسط بسبب السعة الحرارية العالية وقدرتها على توصيل الحرارة، وهو ما يساهم بشكل فعال في تحديد سرعة استجابة المدينة للتسخين خلال النهار بفعل الإشعاع الشمسي، كما ينظم عملية بث الإشعاع الأرضي على مدار اليوم. وقد تبين أيضا أن القصور الحراري يحدد ملامح عدة للجزيرة الحرارية ويفسر كثيرا من خصائصها، مثل تباين شدة الجزيرة الحرارية بين النهار والليل، وظاهرة الهبوط الحراري الصباحي Morning Heat Sink، والتباين الحراري داخل المدينة. لذا تُوصي الدراسة بإجراء المزيد من البحوث التفصيلية التي تتناول القصور الحراري كعامل رئيسي يساهم في فهم المناخ التفصيلي للمدن المصرية، كما تُوصي بأن يُؤخذ في الاعتبار عند وضع أي استراتيجيات أو إجراءات تنفيذية تستهدف تحسين البيئة الحضرية أو التغلب على المشكلات الناجمة عن جزيرتها الحرارية.

- by Waleed Abbas
- •
- Urban Heat Island Effect, Thermal Inertia, Thermal Conductivity, ASTER

Increasing awareness of the urban heat island (UHI) effect has raised attention about the outdoor thermal comfort in cities worldwide. Several studies in the last decades have revealed how critical the UHI effect can be in a cold climate, such as in Canadian cities. As a result, in Toronto, one of the cities experiencing the highest rate of building development in developed countries, UHI mitigation strategies are currently the object of extensive debates. This study evaluates different UHI mitigation strategies in different urban neighbours of Toronto, selected according to their building density. The effects of cool surfaces (on the roofs, on the street pavements or as vegetation areas) are evaluated
through numerical simulations using the software ENVI-met. Having obtained the surface temperature, outdoor air temperature, mean radiant temperature, and physiologically equivalent temperature, this study compares the possible mitigation of net surface radiation and thermal radiative power. The results demonstrate that the duration of direct sun and the mean radiant temperature, which are strongly influenced by the urban form, play a significant role in urban thermal comfort. Finally, this research supports new policies for promoting sustainable urban development in Toronto, and suggests design strategies for a more resilient urban planning.

- by Umberto Berardi
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- Simulation, Cities, Toronto, Urban Heat Island Effect
- by Thilini Kasthuri
- •
- Climate Change, Urban Heat Island Effect

Urbanisation and development over the past 3-4 decades have reduced the amount of pristine rainforest cover in Brunei Darussalam to less than 50% of the country’s land area. Low-density urban sprawl is most pronounced in the Brunei-Muara District, where commercial shop blocks, housing estates and infrastructure are built at rapid rates. By-products of this process include increasing number of decaying, dilapidated urban spots and bare areas (exposed rock and soil) created by abandoned or stalled projects, which quickly become bad lands. The drastic change in land cover is expected to have a significant impact on the local climatic regime as the heat and water absorption and distribution capacities of rainforest differ significantly from that of bare ground, landscaped green spaces, built features, and even secondary forest. While carbon dioxide emission has dominated the discourse on climate change, land cover/land use change is increasing being recognised as a major contributor to global climate change. This is particularly pronounced in developing regions, where the original land cover in the recent past was pristine natural vegetation. This paper aims to assess the potential impact of urbanisation in Brunei Darussalam on climate change by measuring the change in relative heat distribution pattern (as exemplified by urban heat islands) and vegetation indices, using multi-year satellite imagery, in particular, Landsat thermal and near-infrared bands. The remote sensing study is augmented by ground measurements of ambient heat profiles in selected land cover types, particularly in different categories of green spaces. It is hoped that the study will be beneficial to land use and urban planning and its management, particularly in the refinement and enforcement of green space requirements.

- by Wenfeng Zhan
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- Urban Heat Island Effect

The dilemma of devising a theme that can convincingly and collectively express the cultural identity of a nation usually surfaces at the time of planning for the reconstruction and rehabilitation of devastated sites of significance. Particularly following civil wars, both the planning phase and procedures for rehabilitation often exhibit an extension of the civil conflict over the issues of identity and cultural ideology. The 15-year Lebanese civil war (1975–1991) left Beirut severely damaged. After almost two decades after the end of the war, the city center rehabilitation is in its final stages and presents an explicit paradigm of urban governance and management in a severely damaged urban setting claimed by a community of multilayered culture stratums. The construction and reconstruction effort has aspired to resurrect the prewar cosmopolitan Beirut, and has represented not only the rehabilitation of the infrastructure and devastated structures, but equally, an attempt to reinterpret Lebanon's tumultuous past and to create a new collective memory for the nation. For many, most of this effort was in vain for multiple reasons, but more notably, it fueled an endless cultural conflict in the historical city overlooking the sea. The objective of this article is to develop a better understanding of the specific socio-political dynamics and attributes influencing the rehabilitation process of the historic Beirut city center. The article examines the capacity of the chosen rehabilitation approach which was meant to crystallize the intangible meanings of Lebanese cultural identity. In addition to the site visits and observation which took place upon settling in Beirut for the last 6 years, the conclusion is underpinned by a review of culturally-diverse literature and interviews with multiple stakeholders, in particular urban officials, local professionals, visitors , and affected residents of the city center, and represents the groundwork for similar rehabilitation initiatives.

For the first time, a systematic review was conducted on mist spraying systems used for outdoor cooling by perusing twenty years of publications from 12 countries and 7 climatic zones. The twofold aim was to emphasize both the potential against local overheating in a variety of climatic contexts and the extreme heterogeneity in terms of investigation techniques and performance metrics that hinder the construction of a cohesive body of knowledge. In addition to statistics and patterns, data were screened to outline theoretical and methodological trends and gaps and to detect geographic biases and climate dependencies. Indeed, each study was thoroughly described and comparatively discussed according to (i) the investigational method (purely experimental studies, purely numerical studies and those combining field tests with simulations), (ii) the results in terms of cooling, humidification and comfort, also in relation to the adopted performance metrics (iii) the design novelty. Most relevant approaches and findings were discussed and compared to identify governing variables, optimized configurations, unchartered solutions and criticalities. Overall, the collected data qualify water spraying as a cost-effective, versatile and high-impact blue mitigator. Opportunities and challenges towards an informed use emerged and will help delineating appropriate guidelines for practitioners involved in town development, to deliver strategies and precautions.

Keywords: Assessment urban built up area Air temperature Urban heat island Thermal comfort condition Physiologically equivalent temperature Mean radiant temperature Putrajaya city a b s t r a c t The urban heat island (UHI) phenomenon and the outdoor thermal comfort in a planned city need to be reviewed and studied as a climatic issue in the design process. Increasing the temperature and discomfort conditions would be unjustified and not acceptable, unlike the temperature and the discomfort outdoors in a non-planned city that is natural. This study aimed to investigate the UHI phenomenon and outdoor thermal comfort on a micro-scale of the different areas in a planned city. A mobile survey and fixed station measurements were performed to investigate the intra-urban air temperature within the city. The thermal comfort condition of the different hot spots of the urban area in the city was investigated by using Envi-met V4 Beta software. The results indicate that the maximum UHI occurred during the afternoon and reached 3 • C in low-rise residential buildings. The high-rise residential buildings and the Boulevard street are 4 • C lower than low-rise buildings and 1 • C lower than nearby suburban areas. The city's human thermal comfort exceeds the natural range of 30 • C. However, the high-rise residential buildings and the Boulevard street are thermally comfortable most of the daytime hours, while low-rise buildings suffer from a long period of heat stress. The diffuse, reflected solar radiation and the surface temperature have an influence on increasing the Physiologically Equivalent Temperature (PET) thermal index within the city, while the wind velocity and building height are the essential variables reducing the PET thermal index.

- by ADEB QAID
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- Environmental Science, Urban Design, Urban Heat Island Effect, Outdoor Thermal Comfort

Numerous studies have shown that densely developed and populated urban areas experience significant anthropogenic heat flux and elevated concentrations of air pollutants and CO 2 , with consequences for human health, thermal comfort, and well-being. This may also affect the atmospheric composition and circulation patterns within the urban boundary layer, with consequences for local, regional, and global climate. One of the resulting local implications is the increase in urban air temperature. In this context, the present contribution explores urban fabric development and mitigation strategies for two locations in the city of Vienna, Austria. Toward this end, the potential of specific planning and mitigation strategies regarding urban overheating was assessed using a state-of-the-art CFD-based (computational fluid dynamics) numeric simulation environment. The results display different levels of effectiveness for selected design and mitigation measures under a wide range of boundary conditions.

This paper focuses on the benefits on the local microclimate and the building energy saving resulting from green roof retrofits. The research investigates a case study located in a university campus in Toronto, Canada. After completing a detailed energy audit of the building, an assessment of the benefits resulting from the installation of an extensive green roof was performed. A virtual model validated using multiyear data of a local network of different weather stations was used to simulate the effects of the green roof retrofit over the outdoor microclimate. Then, a building energy model was used to compare the energy saving of several green roof designs. Results indicate that increasing the leaf area index (LAI) would lead to an increased cooling effect of the air temperature up to 0.4 • C during the day at pedestrian level, while a more significant temperature reduction would be obtained only at the rooftop level. This confirms the potential of green roofs as urban heat island mitigation strategy. The adoption of a green roof retrofit resulted in a building energy demand reduction by 3%, and in significantly improved indoor comfort levels in the floor below the green roof. Finally, the parametric analysis of different green roof options showed that for building energy savings, increasing the soil depth is more important than increasing the LAI.

Studies on urban heat island (UHI) have been more than a century after the phenomenon was first discovered in the early 1800s. UHI emerges as the source of many urban environmental problems and exacerbates the living environment in cities. Under the challenges of increasing urbanization and future climate changes, there is a pressing need for sustainable adaptation/mitigation strategies for UHI effects, one popular option being the use of reflective materials. While it is introduced as an effective method to reduce temperature and energy consumption in cities, its impacts on environmental sustainability and large-scale non-local effect are inadequately explored. This paper provides a synthetic overview of potential environmental impacts of reflective materials at a variety of scales, ranging from energy load on a single building to regional hydroclimate. The review shows that mitigation potential of reflective materials depends on a set of factors, including building characteristics, urban environment, meteor- ological and geographical conditions, to name a few. Precaution needs to be exercised by city planners and policy makers for large-scale deployment of reflective materials before their environmental impacts, especially on regional hydroclimates, are better understood. In general, it is recommended that optimal strategy for UHI needs to be determined on a city-by-city basis, rather than adopting a “one-solution- fits-all” strategy.

- by Zhihua Wang
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- Urban Planning, Energy Efficiency Buildings, Urban Heat Island Effect, Cool Roofs

Urban Heat Island (UHI) phenomenon has become a regional issue for Greater Kuala Lumpur (GKL) as a number of studies reported an elevated air temperature in highly dense urban areas compared to the rural peripheries. An initial literature survey of UHI studies in GKL revealed an insufficiency and paucity of field measurements for more than one decade (since 1991) before gaining its momentum again after 2004. Despite a very limited number of studies in GKL, many studies used a vague set of site classification, operational definitions of Urban Heat Island Intensity (UHII) derived from such vague classification, uncontrolled and old set of data, limited coverage of weather station network and limited number of weather parameters in data collection. Therefore, this paper attempts to provide an overview of UHI studies in GKL by highlighting the major methodological shortcomings that hamper the reliability of previous measurements and by providing vital suggestions for an improved UHI quantification in future. The findings of most of the studies disclose an increasing trend in the UHII which is associated to the reduction in vegetation cover and land use changes. Eventually, this open up new opportunities for the upcoming studies to investigate the sensitivity of UHI to other unexplored factors in the local context. Besides focusing on the role of vegetation on urban temperature reduction, future studies need to focus more on examining the feasibility of other remediation technologies. This paper also suggests that rigorous attention should be given to a systematic site characterization, controlled and synchronous measurements, broader weather station network as well as incorporation of real-time data to elucidate the current UHII status. In addition, local studies could significantly benefit from the utilization of advanced modelling and simulation technologies as a basis for a more informed decision-making in line with the aspiration of GKL to achieve a world class sustainable metropolis by 2020 (GKL Initiative under the National Key Economic Area). Lastly, the incorporation of UHI phenomena in local policies is also essential to mitigate its deleterious impacts via more urban climate-friendly practices by various stakeholders.

- by Logaraj Ramakreshnan and +1
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- Urban Studies, Air Pollution and Health Effects, Urban Climate, Urban Heat Island Effect

For many centuries the Japanese people have learned to live with their climate by developing adaptive behaviours and sustainable architectural features. During their cold winters, they warm small amount of spaces to avoid energy losses and in the warm humid seasons they largely open the envelope and partitions to maximise the air flow. This vernacular architecture is well known by western designers and touists from the world.
With the last century’s conflicts and following rapid economic growth, those principles have been replaced by energy consuming constructions and maintenance systems, reflected by high fossil fuel imports, the pre-2011 nuclear power dependence and the state-of-the-art technology industry. The massive use of air-conditioning and its resulting waste heat is the one of the main cause of the urban heat island effect. This effect have increased Tokyo’s temperature by 3 degrees Celsius since the last hundred years, and is not only responsible for human discomfort and health issues, but also for increasing cooling loads and climatic disruptions.
This naturally leads into the global interest of dealing with the urban heat island effect and building cooling strategies, but unequal considerations are given within the office building sector. Implemented in the small scale building typology, passive strategies such as natural ventilation inspired by the vernacular traditions and tolerant adaptive opportunities could help in greatly reducing microclimatic anomalies, as well as giving a stronger identity to the Japanese built environment.

It has long been recognised that cities exhibit their own microclimate and are typically warmer than the surrounding rural areas. This ‘mesoscale’ influence is known as the urban heat island (UHI) effect and results largely from modification of surface properties leading to greater absorption of solar radiation, reduced convective cooling and lower water evaporation rates. Cities typically contain less vegetation and bodies of water than rural areas, and existing green and bluespace is often under threat from increasing population densities. This paper presents a meta-analysis of the key ways in which green and bluespace affect both urban canopy- and boundary-layer temperatures, examined from the perspectives of city-planning, urban climatology and climate science. The analysis suggests that the evapotranspiration-based cooling influence of both green and bluespace is primarily relevant for urban canopy-layer conditions, and that tree-dominated greenspace offers the greatest heat stress relief when it is most needed. However, the magnitude and transport of cooling experienced depends on size, spread, and geometry of greenspaces, with some solitary large parks found to offer minimal boundary-layer cooling. Contribution to cooling at the scale of the urban boundary-layer climate is attributed mainly to greenspace increasing surface roughness and thereby improving convection efficiency rather than evaporation. Although bluespace cooling and transport during the day can be substantial, nocturnal warming is highlighted as likely when conditions are most oppressive. However, when both features are employed together they can offer many synergistic ecosystem benefits including cooling. The ways in which green and bluespace infrastructure is applied in future urban growth strategies, particularly in countries expected to experience rapid urbanisation, warrants greater consideration in urban planning policy to mitigate the adverse effects of the UHI and enhance climate resilience.

- by Kan-chane Gunawardena and +1
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- Limnology, Water, Green Infrastructure, Sustainable Building Design

[Published in 2014]
Urban Heat Island (UHI) is considered as one of the major problems in the 21st century as a consequence of urbanisation and industrialisation of human civilisation. The main source of UHI is the large amount of heat produced from urban structures, as they absorb and re-radiate solar radiations. Therefore, Urban Heat Islands develop in areas with a high percentage of non-reflective, water-resistant surfaces and a low percentage of vegetation. Specifically, a lack of vegetation reduces heat lost due to evapotranspiration. Vegetation, particularly in the presence of high moisture levels, plays a vital role in the regulation of surface temperatures, even more than may non- reflective or low-albedo surfaces. There are different ways of reducing the effects of UHI. However, a common measure to mitigate Urban Heat Island is to increase urban green spaces such as parks, street trees and green roofs. This paper discusses the current literature and knowledge about the impacts of green spaces on mitigating UHI. Studies conducted on the influence of greenery on mitigating UHI have indicated that all green spaces help urban areas adapt to the impact of UHI regardless of whether they are parks, street trees or green roofs.

Global climate change, rapid urbanization and population explosion in major cities of Southeast Asia (SEA) are negatively impacting the well-being and liveability of the public in terms of deteriorating outdoor thermal comfort (OTC) levels. However, the available scholarly studies on OTC in the tropical region are insufficient. There is great potential for OTC studies to be used as indicators to measure the sustainable liveability of contemporary cities. As such, there is an immense need for more studies to be conducted in the tropical regions. However, the assessment approaches undertaken in the last decades clearly indicate that there is a need for improvisation. By considering this, this paper provides an overview of published studies that evaluated thermal comfort conditions in the outdoor setting in the tropical context of SEA. Methodological discrepancies and shortcomings are highlighted and discussed to propose a holistic approach for future OTC studies in SEA. The implementation of the proposed holistic approach in the upcoming studies will be beneficial for the improved reliability and integration of findings from studies conducted in various outdoor settings and localities within SEA.

- by Logaraj Ramakreshnan and +1
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- Urban Studies, Tropical Climate Variability, Sustainable Livelihoods, Urban Heat Island Effect

Neighborhood has always been of significant interest to built environment stockholders as a basic planning unit. However, any discussion in these concerns, without drawing attention to sustainable microclimate approaches, would still in a mess at a time of increasing population and climate change. Emergence of the sustainable development concept at the mid-20th century and its emphasis led to increasing crucial role that the urban green infrastructure along with reflective materials can play in mitigating neighborhood microclimate's symptoms of climate change. Considering the lack of studies for urban heat island (UHI) in hot arid regions, particularly in Egypt and the limited number of studies concerning the numerical simulation of all mitigation strategies incorporated, this research studies the mitigation of UHI phenomenon in a case study in Cairo in present and future (2020, 2050 and 2080) through applying the criteria of tree lines, green roofs, high albedo pavements and shading structures within the neighborhood sustainability assessment tool (Leadership in Energy and Environmental Design for Neighborhood; LEED-ND). The microclimatic numerical CFD simulations of ENVI-met 4.0 was used following the measurement of LAI and Albedo of selected Egyptian trees to assess UHI through air and radiant temperature differences before and after applying mitigation strategies. Results demonstrate a considerable ability to acclimatize the microclimate in terms of better conditions in present and future.

The City of Phoenix, Arizona is currently in the midst of a planning exercise to “sustainably” revise its zoning ordinances. The goal is to promote a downtown that is more “lively, inviting and comfortable”. The new zoning code seeks to optimize building and street proportions, street shading, open space, air movement and building materials relative to thermal comfort and Urban Heat Island mitigation. This paper discusses the detailed simulation process to quantify, assess and optimize the urban geometry, urban block proportions, use of materials, shading, landscaping, air flow and various other strategies that would create a more thermally comfortable environment in downtown Phoenix.

The administrative capital of Malaysia, Putrajaya, is one of those cities built on the garden-city concept, however, few studies have been devoted to confirm the validity of the concept. Numerical mesoscale Weather Research and Forecasting (WRF) Model was coupled with Noah land surface model and a single layer urban canopy model (UCM) to investigate the existence and distribution of UHI, and the behaviour of urban canopy layer (2-m) temperature of Putrajaya city. Suitability of the model WRF employed in studying UHI phenomenon in the tropical city of Putrajaya, Malaysia was determined. Precincts in Putra-jaya city were classified into local climate zones (LCZs) and the contribution of urban fabrics on the spatial and temporal variations of UHI was also investigated. Results of the model were verified with in situ studies of the area, and observational data from Alam Sekitar Malaysia Sdn Bhd (ASMA). Comparison with ASMA observational and in situ data reveals a satisfactory performance of the model. UHI intensity of Putrajaya exhibits a diurnal profile; increasing during the night to a peak value and then diminishing in the morning with a negligible value during midday. During the night hours, the UHII ranges from 1.9 • C to 3.1 • C in some of the precincts (LCZs) considered. Overall, average daily intensity of 0.79 • C heating was noted in Putrajaya for the study duration. The overall effect of urbanized LCZs heating of Putrajaya was normalized by the total amount of area reserved for vegetation.

- by Kenobi Morris and +1
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- Meteorology, and Tropical Dynamics, Urban meteorology, Agrometeorology and agroclimatology, Urban Heat Island Effect