Estudos de conforto térmico nos espaços verdes da cidade de Bragança

O projecto GREENURBE visa avaliar o impacte dos espaços verdes na qualidade do ambiente urbano abarcando aspectos como o uso social, a qualidade do ar, o ruído e o conforto térmico, e tendo como referência a cidade de Bragança. O presente poster retrata os estudos de microescala desenvolvidos, e a desenvolver, no sentido de identificar as relações existentes entre os espaços verdes e o conforto térmico. Estes resultados serão futuramente interpretados num contexto climático alargado à escala urbana, desenvolvendo-se uma metodologia pela qual se procurará estabelecer relações entre as características climáticas prevalecentes e o seu potencial para propiciar condições de conforto térmico, identificando-se estratégias que possam contribuir para a melhoria da qualidade térmica do ambiente urbano.FCT-MCTE

Benefits of urban green spaces in noise, air quality and thermal comfort: the case study of Bragança

Urban green areas provide multiple environmental services, contributing to high‐quality environments in our cities. With the purpose of evaluating the influence of urban green spaces in air quality, noise and thermal comfort, a research was developed throughout the last 4 years in the city of Bragança, Portugal. All these aspects were approached from physical and social perspectives. The physical approach involved several studies at urban and green space scales. Field experiments covered such areas as measurements of air pollutants concentrations (ozone, nitrogen dioxide, volatile organic compounds and PM10), sound pressure levels, meteorological and other parameters related to thermal comfort. The social approach consisted in assessing perceptions of citizens over green spaces and their influence on the environment, alongside with the assessment of their attitudes towards those spaces, by means of specific questionnaires applied to a representative sample of local inhabitants. Results showed the relevance of the green spaces in contributing to ameliorate air quality, create more pleasant soundscapes and provide better thermal comfort conditions, especially in spring and summer. Relations between benefits of green spaces and their size, their physical and biological diversity, and their location were found. These characteristics were also identified by respondents as key factors in a moment of selecting a green space to pass the time and to enjoy part or all services it can provide. In the opinion of the respondents, those factors are crucial in maximizing many environmental and social functions of urban green spaces

Green space influence on thermal confort: structured studies in the city of Bragança (Portugal)

Green Spaces are regarded as elements that can provide thermal comfort in cities. A research on green spaces contribution to thermal comfort was carried out, with the purpose of identifying essential principles that can help urban designers to enhance the social use of open spaces. These studies were developed in summer and early fall conditions, by means of structured experiments. These experiments took place in three occasions between June 2008 and September 2009, in a total of 432 thermal sensations questionnaires. The methodology consisted in placing different individuals, organized in uniform age groups and equal numbered in gender, under different thermal environments (shadow versus sun exposure, wind versus wind shield, grass versus artificial pavement) and asking them to express their thermal sensations (using a seven levels scale), while collecting meteorological data. A multinomial logistic regression was used to study the influence of both meteorological variables and personal attributes in thermal sensations. Significant results were found relating differences in thermal comfort with the radiation, air temperature and wind speed. Gender was also found to have a significant influence in human thermal sensations. Results show that differences in green spaces layout can significantly change the thermal environment, thus influencing thermal perceptions

The role of urban green spaces in the urban climate – the case study of the city of Bragança (Portugal)

Urban Green Spaces (UGS) are known to change microclimate conditions, improving thermal comfort and reducing urban heat island effect (UHI). The research of the city-climate interactions can be an important contribution for urban planning, providing inputs for the definition of a climate relevant green infrastructure. Starting in 2011, a study is being carried out aiming at the analysis of the urban climate of Bragança (Portugal), a city located in a mountain area with a complex terrain. This presentation focuses on presenting local evidences of the UGS influence on urban climate and the potential role of the local green infrastructure in urban climate improvement. The research consists on a cross-evaluation between meteorological data, gathered from a network of sensors (23 temperature and RH sensors, three wind speed and direction sensors and one automatic weather station) and a GIS analysis of urban and topographical elements. This network covers seven local climate zones, including UGS (4 sensors). Results show that despite the small size of this city (aprox. 30.000 hab) there is an UHI that can be close to 3 º C in summer with extremes of up to 6º C. Such results are related with the characteristics of the monitored sites showing that UHI is more intense in densely urbanized areas. Other local effects include: an early morning urban cold island effect, the presence of an altitude gradient and of dynamic processes, such as the nocturnal drainage of cold air. Regarding the different UGS in the network, their effects are variable, as reduced UHI intensity is more effective during the summer, mostly motivated by the presence of deciduous trees. UGS are still under the influence of the UHI gradient, thus being mostly warmer than peri-urban locations. Finally, the role of the local urban green infrastructure in Urban Climate Planning is discussed.info:eu-repo/semantics/publishedVersio

Estudo da ilha de calor urbano de Bragança

O constante crescimento das cidades tem levantado diversos problemas ambientais nos espaços urbanos. A construção em altura e o uso de materiais artificiais altera o escoamento atmosférico e o balanço energético, causando o conhecido Efeito de Ilha de Calor Urbano (EICU). Com o objetivo de avaliar o EICU na cidade de Bragança foi instalada uma rede de medição de temperatura e de humidade do ar, com 23 termo-higrómetros colocados em diferentes locais da cidade e no espaço rural, complementada com um estação meteorológica automática. Os resultados evidenciam a existência do EICU. No período de inverno, a intensidade do EICU atinge em média os 2ºC, embora tenham sido registados máximos na ordem dos 5ºC. Tal como seria de esperar, é na época de verão que se verificaram as maiores diferenças entre zonas urbanas e zonas rurais, sendo que a média sobe para os 3ºC nas zonas mais urbanizadas, onde se registam máximos na ordem dos 6ºC. Em ambos os casos, os picos de intensidade observaram-se predominantemente uma a duas horas antes do nascer do sol, em particular em dias de vento fraco. Este estudo aplicou ainda Funções Ortogonais Empíricas (FOE), de forma a identificar os principais padrões de variabilidade dos dados. A partir dos dados horários de todo o ano, o padrão espacial da primeira componente indica claramente a presença de anomalias positivas nas zonas urbanas e negativas nos pontos envolventes, esta componente contém cerca de 38% da variabilidade de todos os dados. A mesma análise baseada nas médias horárias, por época sazonal, evidencia o mesmo padrão espacial, sendo que no verão a série temporal da primeira componente apresenta valores de maior intensidade e cuja variabilidade representa 53.7 %. Estes resultados permitem afirmar que o primeiro modo de variabilidade corresponde ao EICU da cidade de Bragança.info:eu-repo/semantics/publishedVersio

Urban climate studies: addressing the role of urban green spaces

Cities present a wide range of climate transformations resulting from changes induced by buildings and other artificial structures, including such effects as the urban heat island (UHI) and the changes in the ventilation patterns. Under these conditions, urban climate analysis is increasingly considered as a necessary activity that should be part of the urban planning practice. Although there has been a wide development of climate studies across different countries, further improvement is needed to address a wider diversity of geographic locations and conditions (Ren et al., 2010). Stewart and Oke (2012) defined a set of Local Climate Zones (LCZ) as a way to address such a complex reality, including both urban and periurban locations. As part of the European funded project BIOURB, a study is taking place in Bragança (Portugal) aiming at studying local urban climate, while establishing a basic methodology that can be used as a reference for cities located in the regions of the North of Portugal and Castilla-León (Spain). The methodology can be described as consisting on the integration of urban climate monitoring with the interpretation of major factors influencing local climate (topography, land use and artificial structures), allowing for the interpretation of major climate transformations, with the ultimate goal of providing urban design strategies. Urban climate monitoring is being carried out with a combination of twenty three temperature and relative humidity sensors, five wind anemometers and three weather stations. The location of these equipment addresses different LCZs and the potential rural to urban gradient, including several green spaces within the urban limits. Results from a full year campaign, show that while addressing a small, though complex, urban reality and despite the proximity to rural surroundings, the Urban Heat Island effect reaches intensity values over 5oC during the hot summer nights, thus showing the contrast between the higher temperatures resulting from the effects of artificial surfaces, anthropogenic heat and heat retention by buildings, and the lower temperatures observed in green spaces both within and outside the town. As urban climate study is still being carried out, preliminary results suggest green spaces are relevant assets in climate intervention by both diminishing thermal load, relevant under warm summer conditions and to potentially being associated to topographic dynamic processes such cold air drainage (valleys), wind reduction (woodlands) or wind enhancing (grasslands)

Mapeamento climático urbano, aplicações à cidade de Bragança

Esta comunicação descreve o processo de mapeamento climático da cidade de Bragança, como parte do Projecto POCTEP - BIOURB. Este processo partiu da definição de um conjunto de camadas de informação, trabalhadas em Sistemas de Informação Geográfica (SIG), com as quais se definiram características territoriais (morfológicas) e urbanas, com influência sobre o clima local. Estes elementos foram posteriormente classificados em função do seu contributo potencial para dois processos complementares: carga térmica potencial e dinâmica potencia

Green space influence on thermal comfort contrasting approaches in the assessment of conditions in Bragança (Portugal)

Green Spaces are regarded as elements that can help to provide thermal comfort inside cities. To evaluate this influence both climate and personal variables must be investigated and evaluated taking into account different spatial layouts. Trying to address this complex reality, two different approaches were developed, using green spaces at the city of Bragança (Portugal) as case studies: green spaces surveys, addressing users, and structured experiments, controlling both individual and climatic variables. Field surveys proven to identify a narrow range of thermal sensations, thus limiting the analysis. Data from a structured experiment, conducted in early fall conditions, show the influence of different green space locations on both meteorological variables and thermal sensations. Amongst the evaluated variables, global radiation proves to be the most relevant variable influencing the perceived thermal sensations.POCTI - FC

Avaliação da Ilha de calor de Bragança

O presente estudo, realizado no âmbito do projeto transfronteiriço POCTEP - BIOURB, tem por objetivo avaliar o efeito de ilha de calor urbana (ICU) na cidade de Bragança. Para o efeito, foi instalada uma rede de medição de temperatura e de humidade do ar, com vinte e três termo-higrómetros colocados em diferentes locais da cidade e no espaço rural, complementada com um estação meteorológica automática. Os resultados evidenciam a existência do efeito de ICU. Este efeito tem relevância nos pontos com uma urbanização mais densa e decresce nos pontos de menor densidade de edifícios. No período de inverno, a intensidade do efeito de ICU atinge em média os 2ºC, embora tenham sido registados máximos na ordem dos 5ºC. Tal como seria de esperar, é na época de verão que se verificaram as maiores diferenças entre zonas urbanas e zonas rurais, sendo que a média sobe para os 3ºC nas zonas mais urbanizadas, onde se registam máximos na ordem dos 6ºC. Em ambos os casos, os picos de intensidade observaram-se predominantemente uma a duas horas antes do nascer do sol, em particular em dias de vento fraco. Ao início da manhã registou-se ainda um efeito de ilha de frio

Green space influence on thermal comfort: contrasting approaches in the assessment of conditions in Bragança (Portugal)

Urban greening has been widely recognised as a key factor to mitigate the adverse effects of urbanisation in a sustainable manner [1]. Green spaces characteristics include trees, soft surfaces and wind shelters that can influence thermal sensations by inducing changes in such variables as solar radiation, temperatures of surrounding surfaces, air temperature, humidity and wind speed [2,3]. As part of the ongoing research entitled GreenUrbe (PPCDT/AMB/59174/2004), both users surveys and structured experiments are being developed, trying to establish relation between green spaces characteristics and thermal comfort. The city of Bragança is located in north-eastern Portugal. Local climate is characterised by a cold rainy winter and relatively short (June to September) hot and dry summer.FCT-MCTE