Percorrer por autor "Ornelas, Gabriela"
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- Impact of urban and peri-urban landscape on local climate conditions – the case study of the city of Bragança (Portugal) - 2012-2016Publication . Gonçalves, Artur; Ornelas, Gabriela; Ribeiro, A.C.; Feliciano, ManuelIn cities, buildings and paved surfaces change local climate conditions, generating the so called urban climate (Oke, 2004). Urban climate is also influenced by local orography and regional climate. One of the most important urban effects on climate is known as the urban heat island effect (UHI), measured as the difference in temperature between the urban context and the rural surroundings. Research on city/climate interactions can be an important contribution for urban planning, helping to address the negative effects of urbanization (Oke, 2004; Ren et al., 2010) Starting in 2011, as part of a transnational project BIOURB (INTERREG-POCTEP), a study is being carried out aiming at analysing the urban climate of Bragança (Portugal) (Gonçalves et al., 2014), a city located in a mountain area with a complex terrain. This presentation focuses on demonstrating the local influence of the urban and periurban landscape on local climate and evaluating possible planning options that can help improving urban climate. The research consists on a cross-evaluation between meteorological data, gathered from a local network of sensors (23 temperature andhumidity sensors, three wind speed and direction sensors and one automatic weather station) and a GIS analysis of the urban and topographical elements. This network covers seven local climate zones, including urban, peri-urban and rural sites. Results show that despite the small size of the city of Bragança (aprox. 25.000 hab. and 12 sq. km2) there is a mean UHI that reached 3 ºC in the summer with extremes of up to 6º C. Such results are related with the characteristics of the monitored sites and, as expected, UHI is more intense in densely urbanized areas. Other local effects include the presence of an altitude gradient (corrected for UHI analysis) and dynamical processes, such as the nocturnal drainage of cold air. Reduced UHI intensity was achieved in Urban Green Spaces, more effective during summer periods, mostly motivated by the presence of deciduous trees. Despite these positive effects, the studied green spaces are still under the influence of the UHI, being warmer than peri-urban locations. The complex mountain terrain was responsible for differences related to landscape attributes which should be taken into consideration in planning. Therefore recommendations are presented, including the role of the urban green infrastructure as a tool to improve the local climate conditions in the city (summer cooling and attenuated cold temperature effects). Gonçalves, A., Ribeiro, A. C., Maia, F., & Feliciano, M. (2014). Clima Urbano de Bragança. In A. Gonçalves (Ed.): Instituto Politécnico de Bragança. Oke, T. R. (2004). Initial guidance to obtain representative meteorological observations at urban sites: World Meteorological Organization Geneva. Ren, C., Ng, E. Y.-y., & Katzschner, L. (2010). Urban climatic map studies: a review. International Journal of Climatology, n/a-n/a. doi: 10.1002/joc.2237
- The role of urban green spaces in the urban climate – the case study of the city of Bragança (Portugal)Publication . Gonçalves, Artur; Ribeiro, A.C.; Ornelas, Gabriela; Feliciano, ManuelUrban 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.
- Urban cold and Heat Island in the City of Bragança (Portugal)Publication . Gonçalves, Artur; Ornelas, Gabriela; Ribeiro, A.C.; Maia, Filipe; Rocha, Alfredo; Feliciano, ManuelThe thermal environment is an important aspect of the urban environment because it affects the quality of life of urban residents and the energy use in buildings. Urban Heat Island (UHI) and Urban Cold Island (UCI) are complementary effects that are the consequence of cities’ structures interference with the local climate. This article presents results from five years of urban climate monitoring (2012–2016) in a small Portuguese city (Bragança) using a dense meteorological network of 23 locations covering a wide array of Local Climate Zones (LCZ), from urban areas to nearby rural areas. Results show the presence of both the UHI effect, from mid-afternoon until sunrise, andtheUCIaftersunrise,both being more intense under the dense midrise urban context and during the summer. Urban Green Spaces had an impact on both UHI and UCI, with an important role in cooling areas of the city during daytime in the summer. Other LCZs had less impact on local thermal conditions. Despite the small size of this city, both effects (UHI and UCI) had a relevant intensity with an impact on local climate conditions. Both effects tend to decrease in intensity with increasing wind speed and precipitation.