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- Heat stress mitigation by exploring UTCI hotspots and enhancing thermal comfort through street treesPublication . Silva, Tiago; Matias, Márcia; Girotti, Carolina; Vasconcelos, João; Lopes, AntónioHeat 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.
- Tourism and climate in Lisbon: an assessment based on weather typesPublication . Machete, Raquel; Lopes, António; Gómez-Martín, Mª Belén; Fraga, HelderAlthough climate is perceived as an essential part of tourism, influencing touristic regional and seasonal distribution patterns, ideal climate conditions for tourism are often assumed, rather than demonstrated. After reviewing the distinct tools that have been applied in order to evaluate climate potential for tourism, as well as tourists’ preferences, Besancenots’ weather-types method was chosen. This model was adapted and applied to Lisbon, evaluating the suitability of the summer season for tourism activities. The resulting weather type pattern was then crossed with the seasonal tourist demands (visitation statistics), allowing to conclude that even when the weather is categorized as extremely hot (type 7) or unfavourable for tourism (type 8) it does not reflect in the room occupation rates of the city of Lisbon, reinforcing recent advances in tourism climatology, that defy expert based thresholds of thermal preferences and comfort. A reformulation of the weather type model with our findings can be a useful tool for future assessments of tourist potential under projected climate changes.
- An original approach combining CFD, linearized models, and deformation of trees for urban wind power assessmentPublication . Konopka, Jan; Lopes, António; Matzarakis, AndreasWind energy is relevant to self-sufficiency in urban areas, but the accuracy of wind assessment is a barrier to allowing wind energy development. The aim of this work is to test the performance of the Griggs-Putnam Index of Deformity of trees (G-PID) over urban areas as an alternative method for assessing wind conditions. G-PID has been widely used in open terrains, but this work is the first attempt to apply it in urban areas. The results were compared with CFD simulations (ENVI-met), and finally, with the linear model WAsP to inspect if deformed trees can offer acceptable wind power assessments. WAsP (meso-) and ENVI-met (micrometeorological model) showed similar results in a test area inside the University of Lisbon Campus. All trees showed a deformation with the wind direction (S and SE). The mean G-PID wind speed for all trees was 5.9 m/s. Comparing this to the ENVI-met simulations results (mean speed for all trees was 4.25 m/s) made it necessary to adapt the index to urban terrains by reducing each Index Deformation class by about ~2 m/s. Nevertheless, more investigation is needed, since this study is just a first approach to this integrated methodology. Also, tree species and characteristics were not taken into account. These questions should be addressed in future studies, because the deformation of trees depends also on the tree species and phytosanitary conditions.
- Evaluating the cooling potential of urban green spaces to tackle urban climate change in LisbonPublication . Reis, Cláudia; Lopes, AntónioThe increase and optimization of urban vegetation has been considered an e ective mitigation measure of an urban heat island (UHI), with positive e ects on human thermal comfort. In this study, the cooling potential of all green spaces in Lisbon was estimated. For that, several mobile measurements of air temperature data were made in a single park (Gulbenkian’s Garden). These measurements were used for the interpolation of air temperature. Furthermore, urban biomass was estimated using remote sensing products, namely Landsat satellite images. Ultimately, a linear regression model was built from the relation between vegetation density and air temperature. Results regarding the estimation of biomass (AGB) in the city of Lisbon were higher in winter than in summer. The urban green spaces cooling potential model showed that for every decrease of 1 C in air temperature between a measuring point and a reference station we need to increase the area covered by vegetation by 50 m2 (planar measure). This methodology can be applied in other urban areas for the quantification of the cooling e ect provided by vegetation in order to improve urban climate thermal conditions and human well-being and, consequently, to mitigate some consequences of future climate change.
- Heat fluxes from landsat images: a contribuition to Lisbon urban planningPublication . Lopes, António; Vieira, HugoThe urban structure is a modeller of wind fields and an active modifier of radiation conditions, trapping, reflecting and shadowing much more than the rural areas. In a smaller scale the different albedos and the heat capacity of the materials are also able to modify the thermal patterns. The main purposes of this work are to create a land use/urban structure map for climatic purposes and to estimate heat fluxes with numerical modelling and Landsat images are. We also want to contribute to Lisbon's urban planning by creating several cartographic documents as part of the project: “Prescription of climatic principles in urban planning. Application to Lisbon".
- Modeling the influence of summer sea and estuarine breezes on heat stress in Lisbon (Portugal) using GRAMM-SCIPublication . Reis, Cláudia; Oettl, Dietmar; Lopes, António; Nouri, A. Santos; Vasconcelos, JoãoIn this study, the influence of the Tagus river and Atlantic Ocean breezes in a Mediterranean city (Lisbon) on outdoor thermal comfort was analyzed during the thermal summer days. Hourly wind fields were modeled using the GRAMM-SCI software, initialized with ERA5 reanalysis data. The Universal Thermal Climate Index (UTCI) was calculated for 80 weather stations across the city. Additionally, the UTCI anomalies (ΔUTCI) relative to a reference site (the airport weather station) were calculated during breeze and non-breeze events (typically N/NW winds). Results showed that sea breezes can reduce UTCI levels by up to 2,2◦ C during typical breeze days and up to 5,1◦ C during heatwave breeze events. The effect of these breezes on heat stress conditions is felt up to 4 km from the Tagus river, but especially on the areas up to 500 m. However, in 50 % of the cases where no thermal stress was recorded at the airport during breeze events, Lisbon’s riverfront can be more uncomfortable (moderate heat stress) than the northern part of the city (from 2 to 8 km). Additionally, cooling effect of the breezes is only significant enough to cause a transition to a more comfortable UTCI class (especially from very strong to strong heat stress and from strong to moderate heat stress) during heatwaves (strong to very strong heat stress) and on areas up to 1,5 km from the estuary. The promotion of wind corridors is, therefore, crucial to insuring the progression of sea breezes in urban areas and to reduce heat stress.
- Unveiling the Thermo‐Hygrometric Influence of Summer Sea and Estuarine Breezes (SEBs) in Lisbon (Portugal)Publication . Reis, Cláudia; Lopes, António; Nouri, A. Santos; Vasconcelos, JoãoLocal wind, such as sea breezes, play a crucial role in cooling coastal cities. This study presents new insights about the thermo-hygrometric influence of the Tagus and Atlantic Ocean breezes(sea and estuarine breezes [SEBs]) in Lisbon’s urban climate (Portugal). SEB events were identified in the summer of 2022 according to a wind rotation criterion: the interruption of prevailing North and Northwest (Nortada) winds during the morning, the wind shift to Northeast/East/Southeast and, sometimes, to further South/Southwest/West (rotation between 22.6° and 292.5°) and the return of the regional flow at late afternoon. Additionally, air temperature and absolute humidity anomalies (ΔT/Haurb) were calculated according to the distance to the riverfront area. Results show that SEB occurred on 37 (31%) out of 120 days, mainly in July (43%) and August (32%), between, on average, 10:00 AM and 4:00 PM, and average wind speeds of 3.4 m/s. According to the daily thermo-hygrometric cycle, the areas up to 4 km of the Tagus estuary were, on average, cooler than northern Lisbon during SEB events, especially the areas up to 500 m (average ΔTurb reached −1.7°C). Additionally, there was a significant increase in the moisture content during SEB hours across the city but especially close to the riverfront area: the areas up to 500 m registered, on average, ΔHaurb of 4.2 g/m3 on SEB events (12:00 PM) against 2.1 g/m3 during typical Nortada days. This research is a starting point for a future delimitation and preservation of SEB penetration zones in Lisbon to address outdoor thermal discomfort during summer.
- Lisbon Urban Heat Island Updated: new Highlights about the Relationships between Thermal Patterns and Wind RegimesPublication . Lopes, António; Alves, Elis; Alcoforado, Maria Joao; Machete, RaquelUrban growth implies significant modifications in the urban climate. To understand the influence of the city of Lisbon on the urban boundary layer, a mesoscalemeteorological network was installed in 2004. The main goals of the present study are to update the results of the research published in 2007 and to bring more precise information about the relationship between the Urban Heat Island (UHI) and the regional and local wind systems. The highest frequencies of the UHI were found in the city centre (Restauradores). In the green park ofMonsanto, the highest frequency occurred between −2 and0∘C.During the summer, the effect of the breezes was observed in Bel´em, lowering the temperature.The“strong” UHI (intensity >4∘C) occurredmore often during the summer, with median values of 2∘C by night and 1.8∘C by day.The highest frequencies of UHI occurred for winds between 2 and 6m/s and were not associated with atmospheric calm, as pointed out in the literature.Winds above 8m/s inhibit the occurrence of strong UHI in Lisbon. Summer nighttime strong UHI should be further investigated, due to the heat stress consequences on the population and probable increase of energy consumption.
- Tourists’ perceptions on climate change in Lisbon RegionPublication . Clemente, Filomena; Lopes, António; Ambrósio, VitorThe interface between climate change and tourism is multifaceted and complex. This research aims to understand the relationship established between the tourists’ concerns regarding the impacts of climate change and the risks that may arise and the willingness to pay (WTP) a supplementary fee, and what its value should be, in the tourist packages for environmental sustainability. The empirical phase of this research is presented in the form of a problem: “Will tourists be willing to pay a supplementary fee on tourist packages for environmental sustainability?”. To answer this question, a methodology was implemented in which a questionnaire was given to tourists, and the results were elaborated with several descriptive and multivariate statistics were elaborated. The results show that most tourists are not yet willing to pay a supplementary fee on tourist packages for environmental sustainability, but that this value increases with increasing concern about the risks associated with climate change. This research is intended to contribute to the development of more effective policies, in a bottom-up approach, to manage the risks related to climate change, facilitating successful adaptation.
- Local Weather Types by thermal periods: deepening the knowledge about Lisbon’s urban climatePublication . Reis, Cláudia; Lopes, António; Correia, Ezequiel; Fragoso, MarceloUrbanized hot spots incorporate a great diversity of microclimates dependent, among other factors, on local meteorological conditions. Until today, detailed analysis of the combination of climatic variables at local scale are very scarce in urban areas. Thus, there is an urgent need to produce a LocalWeather Type (LWT) classification that allows to exhaustively distinguish di erent urban thermal patterns. In this study, hourly data from air temperature, wind speed and direction, accumulated precipitation, cloud cover and specific humidity (2009–2018) were integrated in a cluster analysis (K-means) in order to produce a LWT classification for Lisbon’s urban area. This dataset was divided by daytime and nighttime and thermal periods, which were generated considering the annual cycle of air temperatures. Therefore, eight LWT sets were generated. Results show that N and NW LWT are quite frequent throughout the year, with a moderate speed (daily average of 4–6 m/s). In contrast, the frequency of rainy LWT is considerably lower, especially in summer (below 10%). Moreover, during this season the moisture content of the air masses is higher, particularly at night. This methodology will allow deepening the knowledge about the multiple Urban Heat Island (UHI) patterns in Lisbon.