Le phénomène d'îlot de chaleur urbain engendre de l'inconfort thermique auprès des habitants. Améliorer le microclimat en zone urbaine est donc l'une des préoccupations des aménageurs. La végétalisation des villes s'avère une solution prometteuse, car l'évapotranspiration des plantes etles ombres portées des arbres ont un impact significatif sur le bilan thermique de l'atmosphère alentour. Un défi majeur aujourd'hui est le développement d'un modèle de simulation microclimatique capable de reproduire les conditions climatiques d'une rue, voire d'un quartier urbain végétalisé, dans l'objectif de proposer un outil d'aide à la décision pour l'aménagement des villes durables. L'objectif de cette thèse est d'étudier comment prendre en compte la végétation et plus particulièrement les arbres, dans un modèle microclimatique 30 afin de simuler le microclimat d'un quartier. Deux modèles, LASER/F et RATP sont appliqués à l'échelle d'un arbre et d'un parc urbain pour mener à bien cette étude. / The urban heat island phenomenon causes thermal discomfort to residents. lmproving the microclimate in urban areas is therefore one of the concerns of urban plan ners. The greening of cities (with lawns, trees, green roofs, etc.) is a promising solution, as the transpiration of plants and the shadows of trees have a significant impact on the thermal balance of the surrounding atmosphere. This act must be planned to optimize the benefits of vegetation. A key challenge today is thus the development of a microclimatic simulation model capable of reproducing the climatic conditions of a street, or even a vegetated urban neighborhood, with the aim of proposinga decision support tool for the development of sustainable cities. The aim of this thesis is to study how to consider vegetation and especially trees, in a 30 microclimatic model to simulate the microclimate of a neighborhood. Two models, LASER/F and RATP were applied at the scale of a tree and an urban park to carry out this study.

A Ilha de Calor Urbana no município e Região Metropolitana de São Paulo foi estudada por uma série de autores da Geografia e Meteorologia através da aplicação de metodologias de estudos empíricos na avaliação do fenômeno. A vigente pesquisa apresenta uma nova metodologia na avaliação do campo térmico urbano e o conjunto de variáveis climáticas e antrópicas que o condicionam. Para tal foi realizado o seguinte teste de hipótese: a dinâmica territorial da Ilha de Calor Urbana corresponde às interações entre as condições sinóticas, uso e cobertura do solo e balanço de energia. Além desta, dentre os diversos objetivos específicos, o estudo contou com a avaliação do campo térmico dos parques públicos de lazer. Para tal foram utilizados os métodos descritivo, seguido do comparativo e análise integrada descritiva, aliados a uma simbiose entre aplicações de técnicas de sensoriamento remoto e geoprocessamento. Um total de nove imagens do satélite Landsat-5 sensor TM no período de 2007 a 2011 foram utilizadas na geração de imagens termais, posteriormente estas foram vetorizadas e sobrepostas a padrões oficiais de uso do solo, também foram adotados índice de vegetação, fotografias áreas, cartas e boletins sinóticos e dados de campo referentes à temperatura do ar, umidade relativa, precipitação, direção e velocidade do vento, evaporação e radiação solar global. O modelo SEBAL (Surface Energy Balance Algorithms for Land) foi aplicado a três imagens do mapeador temático Landsat-5 de diferentes datas, através do mesmo foram gerados mapas de albedo da superfície, saldo de radiação à superfície, fluxo de calor sensível e latente. Os resultados demostraram a veracidade da hipótese, a conformação e dinâmica territorial da Ilha de Calor Urbana corresponderam a diferentes condições de tempos sinóticos, os quais determinaram o transporte de umidade do oceano para atmosfera continental e por seguinte transformaram o balanço de energia local. Foram verificados três diferentes padrões territoriais, em todos eles os padrões de uso do solo ligados a comércio e serviços, armazéns e indústrias que apresentaram índice de biomassa vegetal igual zero, obtiveram a melhor correlação espacial com o fenômeno. O cenário chamou atenção para a preservação e expansão do arboreto urbano, parques e unidades de conservação, visto que estes demonstraram ser a fonte para redução da temperatura da superfície urbana. / The Urban heat island in the city and metropolitan region of São Paulo has been studied by several authors in the areas of geography and Meteorology through the application of methodologies of empirical studies on the evaluation of the phenomenon. Our research presents a new methodology in the evaluation of the urban thermal field and the set of climatic and anthropogenic variables that influence it. To this end, the following hypothesis testing was conducted: the territorial dynamics of the urban heat island corresponds to the interactions between synoptic conditions, use and coverage of the soil and energy balance. Additionally, among several other specific objectives, the study was also preoccupied with the evaluation of the thermal field of public parks. For such purpose we applied the descriptive method, followed by the comparative method and descriptive integrated analysis, combined with a symbiosis between applications of remote sensing and GIS techniques. A total of nine satellite images Landsat-5 TM sensor in the period from 2007 to 2011 were used on thermal imaging, these were later vectorized and superimposed on official standards of land use. Other than that, vegetation index, air photographs, letters and synoptic bulletins and field data related to air temperature, relative humidity, precipitation, wind direction and speed, global solar radiation and evaporation were also adopted. The model SEBAL (Surface Energy Balance Algorithms for Land) was applied to three thematic mapper images Landsat-5 from different dates; through these images were generated albedo maps from the surface, the surface radiation balance, sensible and latent heat flux. The results proved the hypothesis true, the conformation and territorial dynamics of the urban heat island corresponded to different conditions of synoptic climates, which determined the humidity transportation from the ocean into continental atmosphere and, consequently, transformed the balance of local energy. Three different territorial patterns were investigated; in all of them the land use patterns linked to trade and services, warehouses and industries that showed the index of plant biomass equal zero obtained the best spatial correlation with the phenomenon. The scenario drew attention to the preservation and expansion of the urban arboretum, parks and protected areas since these proved to be the source for the development of thermal environmental urban quality.

O fenômeno de ilhas de calor urbanas ocorre principalmente nos centros urbanos caracterizados pela grande concentração de edificações, ausência de vegetação e uso de materiais impermeáveis com grande capacidade de armazenar calor. As temperaturas elevadas causam desconforto térmico, problemas de saúde e maior consumo de energia para resfriamento de edificações. O objetivo da pesquisa presente é investigar o impacto da permeabilidade dos revestimentos urbanos horizontais na variação da temperatura do ar e na formação de ilhas de calor urbanas na cidade de São Carlos, SP. Embora São Carlos seja uma cidade de porte médio, o processo da urbanização criou áreas densamente construídas e sem muita vegetação, o que favorece o aquecimento do ar e das superfícies. Para avaliar a variação da temperatura do ar em relação às características urbanas, foram realizadas medições fixas da temperatura e umidade relativa do ar em 37 pontos que representam diferentes tipos de ocupação urbana em quatro estações do ano, durante 15 dias em cada estação. Nos entornos dos pontos de medição foi feito o mapeamento da permeabilidade dos revestimentos horizontais das superfícies. A correlação entre as variáveis climáticas e urbanísticas foi analisada para cada estação separadamente e a seguir fez-se a análise comparativa de todas as estações através da normalização dos dados climáticos obtidos por monitoramento. A partir dos dados normalizados foram elaborados mapas térmicos. Os resultados confirmam o aumento da temperatura e diminuição da umidade em locais onde predominam revestimentos impermeáveis. Desse modo, este estudo fornece subsídios importantes para o planejamento urbano, a fim de criar espaços urbanos termicamente confortáveis na cidade de São Carlos. / The phenomenon of urban heat island occurs principally in urban centers characterized by big concentration of buildings, absence of vegetation and use of impermeable materials with high capacity to store heat. Elevated temperatures cause thermal discomfort, health problems and higher energy consumption for cooling of the buildings. The objective of the present research is to investigate the impact of permeability of horizontal urban coatings on the variation of air temperature and formation of urban heat islands in the city of São Carlos, SP. Although São Carlos is a medium sized city, the process of urbanization created densely built up areas without a lot of vegetation, which benefits the heating of air and surfaces. In order to evaluate the temperature variation in relation to urban characteristics, fixed measurements of air temperature and humidity were be performed in 37 points which represent different types of urban occupation in four season of the year, during 15 days in each season with interval of 30 minutes. In the surroundings of each point of measurement was performed a mapping of permeability of horizontal coatings. The correlation between climatic and urbanistic variables was analyzed for each season separately and following was done a comparative analysis of all the seasons by the use of normalization and extrapolation of climatic data. Based on the normalized data were elaborated temperature maps. The results confirm the increase in temperature and the decrease in humidity in the locations where impermeable coatings dominate. Thus, this study provides important supplies for urban planning, in order to create thermally comfortable urban spaces in the city of São Carlos.

The Earth's climate is changing and cities are facing a warmer future. As the locus of economic activity and concentrated populations on the planet, cities are both a primary driver of greenhouse gas emissions and places where the human health impacts of climate change are directly felt. Cities increase local temperatures through the conversion of natural land covers to urban uses, and exposures to elevated temperatures represent a serious and growing health threat for urban residents. This work is concerned with understanding the interactions of global trends in climate with local influences tied to urban land covers. First, it examines temperatures during an extended period of extreme heat and asks whether changes in land surface temperatures during a heat wave are consistent in space and time across all land cover types. Second, the influences of land covers on temperatures are considered for normal and extreme summer weather to find out which characteristics of the built environment most influence temperatures during periods of extreme heat. Finally, the distribution of health vulnerabilities related to extreme heat in cities are described and examined for spatial patterns. These topics are investigated using meteorology from the summer of 2006 to identify extremely hot days in the cities of Atlanta, Chicago, Philadelphia, and Phoenix and their surrounding metropolitan regions. Remotely sensed temperature data were examined with physical and social characteristics of the urban environment to answer the questions posed above. The findings confirm that urban land covers consistently exhibit higher temperatures than surrounding rural areas and are much more likely to be among the hottest in the region, during a heat wave specifically. In some cities urban thermal anomalies grew between the beginning and end of a heat wave. The importance of previously recognized built environment thermal influences (impervious cover and tree canopy) were present, and in some cases, emphasized during extreme summer weather. Extreme heat health health vulnerability related to environmental factors coincided spatially with risks related to social status. This finding suggests that populations with fewer resources for coping with extreme heat tend to reside in built environments that increase temperatures, and thus they may be experiencing increased thermal exposures. Physical interventions and policies related to the built environment can help to reduce urban temperatures, especially during periods of extremely hot weather which are predicted to become more frequent with global climate change. In portions of the city where populations with limited adaptive capacity are concentrated, modification of the urban landscape to decrease near surface longwave radiation can reduce the chances of adverse health effects related to extreme heat. The specific programs, policies, and design strategies pursued by cities and regions must be tailored with respect to scale, location, and cultural context. This work concludes with suggestions for such strategies.

University of Macau / Faculty of Science and Technology / Department of Civil and Environmental Engineering

University of Macau / Faculty of Science and Technology / Department of Civil and Environmental Engineering

Since the early 1800's, many studies have recognized increased heat in urban areas, known as the urban heat island (UHI) effect, as one of the results of human modification to the natural landscape. UHI is related to differences in land surface temperature (LST) between rural areas and urban areas where factors of the built environment such as the thermodynamic capacities of materials, structural geometry, and heat generating activities cause increased storage and re-radiation of heat to the atmosphere. This thesis examines the correlation between factors of urbanization and differences in land surface temperature (LST) in the subtropical climate of Pinellas County, Florida using remote sensing techniques. It describes the spatial pattern of LST, analyzes its relationship to factors of urbanization relative to NDVI, percentage of impervious surface, and land use land cover in the study area. It also assesses the effectiveness of remote sensing as an efficient method of identifying LST patterns at the local and neighborhood level for mitigation strategies. Landsat TM thermal band imagery for three dates; April 1986, 2001 and 2009 was processed using Qin's mono-window algorithm (MWA) technique to derive LST levels. This data was compared to in-situ readings, then normalized and statistically analyzed for correlation with vegetation ratio (NDVI) and imperviousness percentages derived using linear spectral mixing/unmixing, and also with land use/land cover classification. The resulting LST spatial pattern is a gradient across the peninsular landscape, from cooler water and wetland areas to a generally warmer interior, interspersed with micro-urban heat islands (MUHIs), corresponding to urban structures and "cool-islands" of parkland and lakes. Correspondence between LST pattern and urban structures and land use demonstrates the suitability of medium resolution remote sensing data and techniques for identifying micro-urban heat islands (MUHIs) for possible mitigation. Mitigation could include relatively low-cost measures like replacement of inefficient asphalt roofs with more reflective and emissive "cool roofs," placement of "street trees" to enhance shade, and replacement of impervious pavements by permeable surfaces. The thesis concludes that Landsat TM imagery processed with the MWA provides an efficient, relatively low-cost method for locating MUHIs. Satellite remote sensing, combined with aerial photography can facilitate neighborhood level analysis for the implementation of low-cost mitigation techniques. Previous studies have demonstrated that these are successful ways to mitigate the UHI effect at the micro-scale level; lowering urban heat and saving energy, and also facilitating the reintegration of natural elements into the urban environment.

Στα πλαίσια της έλλειψης της μελέτης του φαινομένου της ΑΘΝ σε περιφερειακές Ελληνικές πόλεις, η παρούσα διδακτορική διατριβή παρουσιάζει και αναλύει τα αποτελέσματα της μελέτης του φαινομένου της ΑΘΝ σε δύο μικρές πόλεις της περιφέρειας, το Αγρίνιο και τα Ιωάννινα. Στόχος της εργασίας είναι να μελετήσει την ύπαρξη της ΑΘΝ, καθώς και να προσδιορίσει την ένταση και τη μορφή της. Για το σκοπό αυτό ένα δίκτυο αισθητήρων θερμοκρασίας σε συνδυασμό με μετεωρολογικούς σταθμούς αναπτύχθηκε στις δύο πόλεις και θερμοκρασιακά δεδομένα συλλέχθηκαν για το σχηματισμό του θερμικού τους προφίλ. Τα αποτελέσματα δείχνουν έντονη παρουσία του φαινομένου κυρίως κατά τις βραδινές ώρες και ένταση θερμικής νησίδας που φτάνει και τη μέση τιμή των 3.8 οC το μήνα Αύγουστο στο Αγρίνιο ενώ στα Ιωάννινα για την ίδια περίοδο το φαινόμενο έχει πιο ήπια μορφή (1.5 οC). Για την αντιμετώπιση του φαινομένου, την εξοικονόμηση ενέργειας καθώς και τη βελτίωση της θερμικής άνεσης των κτιρίων πόλεων που αντιμετωπίζουν πρόβλημα με την ΑΘΝ, μελετήθηκε η περίπτωση χρήσης υδρόφιλων ενεργειακών υλικών ως επικάλυψη οροφών, για μείωση της ροής θερμότητας από την οροφή με εξατμιστικό δροσισμό καθώς και τα δευτερεύοντα ενεργειακά κέρδη από μια πιθανή εγκατάσταση φωτοβολταϊκών οροφής. Η μελέτη περιλάμβανε την ανάπτυξη πειραματικής διάταξης αεροσήραγγας για τη δοκιμή των υλικών, με προσομοίωση των καιρικών συνθηκών της πόλης κατά του καλοκαιρινούς μήνες, όπου και το φαινόμενο της αστικής θερμικής νησίδας είναι πολύ έντονο, καθώς και ανάπτυξη φωτοβολταϊκών σε ταράτσα πανεπιστημιακού κτιρίου. Τα αποτελέσματα δείχνουν ότι ο εξατμιστικός δροσισμός μπορεί να αποτελέσει μια πολλά υποσχόμενη μέθοδο για την αντιμετώπιση της ΑΘΝ, ενώ η εγκατάσταση φωτοβολταϊκών μπορεί να συνεισφέρει επίσης στην εξοικονόμηση ενέργειας για δροσισμό τους καλοκαιρινούς μήνες, επιπλέον της παραγωγής ενέργειας. / Due to the lack of research on the field of the UHI effect in minor Greek cities, this thesis presents and analyzes the results of studying the UHI phenomenon in two small cities of the Greek province, Agrinio and Ioannina. Our aim was to study the existence of the UHI phenomenon as well as to determine its intensity and its type. In order to achieve that, a network of thermal sensors and meteorological stations was set on the two cities and temperature data were collected in order to define their thermal profile. The results point severe presence of the phenomenon especially during the nocturnal hours while the intensity of the phenomenon reaches up to 3.8 οC during August in Agrinio while in Ioannina at the same period the phenomenon is softer (1.5 οC). To mitigate the problem, save energy and improve the thermal capacity of the urban buildings in cities where the UHI occurs, the use of hydrophilic materials as a layer sheathing the roof was developed, in order to control the thermal flow from the roof by evaporative cooling. Furthermore, secondary energy benefits from a possible photovoltaics roof installation were investigated. Our research included the developing of an experimental set-up of a wind tunnel where sample materials were tested, by simulating the weather conditions of the city during the summer months, exactly the period of the high UHI intensity, as well as the installation of photovoltaics on a terrace of the university. The results indicate that evaporative cooling might be a very promising method in the field of the UHI phenomenon confrontation while the installation of photovoltaics can contribute in power saving for cooling during the summer months, in addition to electricity production.

The objective of this work is to study the urban climate, mainly by focusing on urban temperature trends. The specific focus is to understand the reasons of increase in minimum temperature through observational and modelling techniques. For this purpose, the temperatures data from 1950 to 2004 measured on several meteorological stations of Pakistan is studied and analyzed. Daily averaged annual and seasonal minimum (Tmin) and maximum (Tmax) temperature data of 37 meteorological observatories of Pakistan (17 urban, 7 town and 13 rural) from 1950 to 2004 is first homogenized and then analyzed. The results show that after 1980s Tmin and Tmax increase faster than the period before 1980s at urban areas. During 1980-2004, the increase in Tmin at major urban stations is observed higher than the smaller towns and rural stations. To understand, the effect of the size of the city, changing land use and the building height on the evolution of minimum and maximum temperatures in urban areas has been studied by using the FVM (Finite Volume Model) model and the simulations are run for three days starting at 00:00 (GMT) on 19th day of each month and ending at 00:00 (GMT) on 22nd day of each month. For each month, 48 possible combinations of simulation scenarios are run (4*4*3) and in total, 576 simulations (48*12) are run for a year. The main results show that Tmin and Tmax increase when urban fraction u, city size r and building height h increase. But it is noticed that Tmax increases more than the Tmin when u increases, Tmin increases more than the Tmax when r increases and Tmin increases more than the Tmax when h increases. Among all urban factors (urban fraction u, city size r and building's height h), city size is the major factor that mainly contributes to increase the minimum temperature more than the maximum temperature in urban areas.

abstract: The Urban Heat Island (UHI) has been known to have been around from as long as people have been urbanizing. The growth and conglomeration of cities in the past century has caused an increase in the intensity and impact of Urban Heat Island, causing significant changes to the micro-climate and causing imbalances in the temperature patterns of cities. The urban heat island (UHI) is a well established phenomenon and it has been attributed to the reduced heating loads and increased cooling loads, impacting the total energy consumption of affected buildings in all climatic regions. This thesis endeavors to understand the impact of the urban heat island on the typical buildings in the Phoenix Metropolitan region through an annual energy simulation process spanning through the years 1950 to 2005. Phoenix, as a representative city for the hot-arid cooling-dominated region, would be an interesting example to see how the reduction in heating energy consumption offsets the increased demand for cooling energy in the building. The commercial reference building models from the Department of Energy have been used to simulate commercial building stock, while for the residential stock a representative residential model prescribing to IECC 2006 standards will be used. The multiyear simulation process will bring forth the energy consumptions of various building typologies, thus highlighting differing impacts on the various building typologies. A vigorous analysis is performed to see the impact on the cooling loads annually, specifically during summer and summer nights, when the impact of the 'atmospheric canopy layer' - urban heat island (UHI) causes an increase in the summer night time minimum and night time average temperatures. This study also shows the disparity in results of annual simulations run utilizing a typical meteorological year (TMY) weather file, to that of the current recorded weather data. The under prediction due to the use of TMY would translate to higher or lower predicted energy savings in the future years, for changes made to the efficiencies of the cooling or heating systems and thermal performance of the built-forms. The change in energy usage patterns caused by higher cooling energy and lesser heating energy consumptions could influence future policies and energy conservation standards. This study could also be utilized to understand the impacts of the equipment sizing protocols currently adopted, equipment use and longevity and fuel swapping as heating cooling ratios change. / Dissertation/Thesis / M.S. Architecture 2011