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Air pollution Dynamics: the role of meteorological factors in PM10 concentration patterns across urban areas
Publication . Girotti, Carolina; Fernando Kowalski, Luiz; Silva, Tiago; Correia, Ezequiel; Shimomura, Alessandra R. Prata; Akira Kurokawa, Fernando; Lopes, António
Air pollution is a major health problem in urban areas, influenced by traffic and atmospheric conditions. This
study investigates the relationship between meteorological factors—wind direction, wind speed, boundary layer
height, and atmospheric stability conditions —street trees, and PM10 concentration in three urban canyons:
Avenida da Liberdade and Estrada de Benfica in Lisbon, and Marginal Tietˆe in S˜
ao Paulo. Five years of hourly
meteorological data and PM10 concentrations were analysed. Despite differences in scale and traffic volume, the
results show that PM10 concentration patterns were similar in both Lisbon study areas. These areas also indi
cated a significant influence of atmospheric variables such as wind speed, boundary layer height, and atmo
spheric stability conditions. Tietˆe, with a higher vehicle density and different atmospheric conditions (lower
wind speeds and greater atmospheric stability), presents higher PM10 peaks. Seasonal analysis revealed distinct
patterns influenced by atmospheric instability, wind speed, and direction. In winter, areas with dense street tree
cover had reduced PM10 levels, while those without showed higher concentrations due to increased stability.
Wind direction played a crucial role, favouring the pollutant dispersal in canyons with parallel winds. The
Factorial Analysis of Mixed Data method identified qualitative variables linked to the seasons, wind direction,
and presence of trees. PM10 levels below the were associated with the summer and autumn period, parallel
winds, and street trees, while levels above the limit were linked to winter period and areas without street trees.
By integrating big data analytics with environmental monitoring, this research underscores the importance of
considering the local atmospheric conditions and environmental variables in the urban air quality management.
Thus, it demonstrates that the traffic volume alone does not determine PM10 concentrations; instead, the
interplay of multiple factors, including meteorological conditions and urban planning, played a crucial role. This
study provides valuable insights for developing effective strategies to mitigate urban air pollution and protect
public health.
Thermal preference and pleasantness of a students’ population in a coastal urban area during summer
Publication . Silva, Tiago; Lopes, António; Vasconcelos, João; Morgado, Paulo
In thermal comfort research, two main domains are identified: objective and subjective. This study focusses on the latter, examining various aspects of preference, sensation, and pleasantness. It also clearly distinguishes each concept and sets the groundwork for their standardised use in urban planning and urban climate studies. Additionally, this study emphasises the often-overlooked geographical perspective, aiming to address previous gaps in this research area. Environmental conditions were found to be the main determinants influencing pedestrians' thermal sensation, preference, and pleasure. Key factors include air temperature, solar radiation, and wind speed, which exhibit strong correlations with pleasure responses. Additionally, urban density, clothing type and colour, shading, sex, and weather type significantly impact thermal sensation and reported pleasantness. It was observed that people who overdressed for the season, wore dark or warmer clothes, experienced air temperature and solar radiation more intensely. Similarly, those in high-density urban areas, without shade, or when weak continental wind conditions were observed, reported stronger thermal sensations. Women generally sensed air temperature and solar radiation as more intense compared to men. These factors influence thermal pleasantness, varying in importance, spatial distribution, and statistical relationship. Higher wind speeds, particularly from an Atlantic direction, were found to enhance thermal pleasantness by balancing conditions and reducing thermal sensation votes for air temperature and solar radiation. Green areas also increased thermal pleasantness by lowering air temperature and solar radiation sensations and promoting a sense of happiness among pedestrians.
Thermal stress and comfort assessment in urban areas using Copernicus Climate Change Service Era 5 reanalysis and collected microclimatic data
Publication . Silva, Tiago; Lopes, António; Vasconcelos, João; Chokhachian, Ata; Wagenfeld, Malte; Santucci, Daniele
In this initial study of a research project, this paper seeks to understand the thermal conditions in the cities of Lisbon and
Munich, specifcally focusing on Urban Heat Island intensity and on thermal comfort using the Universal Thermal Climate
Index modeling data at the Local Climate Zone scale. Based on these datasets, Munich has exhibited more unfavourable
thermal conditions than Lisbon. In terms of UHII, both cities have shown that low, medium, and high rise compact urban
areas and bare rock or paved areas have the highest values, while sparsely built areas have the lowest. These results difer
from the UTCI, which indicates that in Lisbon and Munich, these sparsely built areas as well as areas with low plants and
vegetation are the most uncomfortable. In Munich, the population was exposed to very strong heat stress, while Lisbon
experienced strong heat stress conditions. Conversely, low, medium, and high rise compact urban areas and densely wooded
areas in Munich, and scattered trees areas and large low-rise urban areas in Lisbon, have demonstrated the lowest monthly
mean and average maximum values. These results will be further explored in future studies in the city of Lisbon and crosschecked with data obtained from roving missions. This will enable a more detailed temporal and local analysis.
A micro-scale look into pedestrian thermophysiological comfort in an urban environment
Publication . Silva, Tiago; Lopes, António; Vasconcelos, João
Different spatial scales enable the analysis of thermophysiological conditions of pedestrians in an urban environment. A higher resolution hotspot analysis was conceived using GIS technology in some areas of Lisbon with different morphological conditions. Eleven hotspots were found across six study areas, located in high to moderate urban density conditions and in different types of urban spaces. So, six hotspots were found in avenues (high urban density conditions), three in streets, and two in general open spaces (moderate urban density conditions). These spaces are characterized by being busy areas with high anthropogenic influence, with high-absorbing and reflective materials, and with very poor green infrastructure. Environmental conditions, namely, radiation, mean radiant temperature, and air temperature, were the main cause of hotspot existence, and the main propellers for UTCI intensification. The urban density variable was also found to be important, especially in avenues and open spaces. In these areas, the adjusted component for environmental and urban density conditions can increase 0.60 to 1.35 °C in open spaces and 0.30 to 0.60 °C in avenues, each time there is a one-unit increase in the component. Trees, either in the street or in parks, have generally been found to decrease the UTCI.
Heat stress mitigation by exploring UTCI hotspots and enhancing thermal comfort through street trees
Publication . Silva, Tiago; Matias, Márcia; Girotti, Carolina; Vasconcelos, João; Lopes, António
Heat stress mitigation actions must be carefully planned in order to achieve efective outcomes. By integrating urban planning guidelines with urban climate knowledge, substantial benefts can be achieved for the community. In Lisbon, the study area, urban planning guidelines are strict in relation to the tree species which should be used for planting. This study examined these species environmental contributions to the community, especially in regard to heat stress mitigation in two urban canyons previously found as UTCI hotspots. For this, microclimatic Envi-met simulations were run which allowed recalculation of the UTCI hotspot analysis and to assess individual species contribution to possible mitigation eforts.
Results demonstrated the ability of these trees to lower air temperature and the Universal Thermal Climate Index (UTCI). By reducing UTCI temperatures between 3.19 °C and 6.27 °C on a hot summer’s day, these trees were also able to transform an identifed UTCI hotspot into a coldspot. From the studied species, Pyrus calleryana was found to be the most efective species for mitigating thermal stress, although all three species performed well. Regarding community services, according to the iTree tool, Cercis siliquastrum had the greatest overall impact. These results give to the municipal urban planning which tree species should be prioritized in terms of climate action, as well as a methodological framework to assess at local scale which areas should be intervened.
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Fundação para a Ciência e a Tecnologia
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UI/BD/152225/2021