Cities are rapidly expanding, and global warming is intensified in urban environments due to the urban heat island effect. Therefore, urban animals may be particularly susceptible to warming associated with ongoing climate change. Thus, I used a comparative and manipulative approach to test three related hypotheses about the determinants of heat tolerance or critical thermal maximum (CTmax) in urban ants—specifically, that (1) body size, (2) hydration status, and (3) preferred micro-environments influence CTmax. I further tested a fourth hypothesis that native species are particularly physiologically vulnerable in urban environments. I manipulated water access and determined CTmax for 11 species common to cities in California's Central Valley that exhibit nearly 300-fold variation in body mass. Inter- (but not intra-) specific variation in body size influenced CTmax where larger species had higher CTmax. The sensitivity of ants’ CTmax to water availability exhibited species-specific thresholds where short-term water limitation (8 h) reduced CTmax in some species while longer-term water limitation (32 h) was required to reduce CTmax in other species. However, CTmax was not influenced by the preferred foraging temperatures of ants. Further, I did not find support for my fourth hypothesis because native species did not exhibit reduced thermal safety margins, or exhibit CTmax values that were more sensitive to water limitation relative to non-native species. In sum, understanding the links between heat tolerance and water availability will become critically important in an increasingly warm, dry, and urbanized world that may be selecting for smaller (not larger) body size.

No description available.

The severity of extreme heat events paired with the urban heat island effect cannot be overstated, as the impacts are substantial and widespread, affecting peak energy demands, transport systems, air and water quality, and most notably causing heat-related illnesses and death. These consequences make evident the importance of reducing heat in urban areas and ensuring that urban populations are safe during extreme heat events. In order to both reduce the urban heat island effect and prepare cities for a hotter future, it is critical to building our understanding of the cities at risk and the relationship between heat and the urban environment. This thesis applies urban morphology theory and remote sensing techniques to explore how urban typologies in Metro Boston perform during an extreme heat event. Included within the thesis is a literature review exploring urban heat methodologies and urban morphology, a desktop review examining a set of cities’ climate action reports, and a remote sensing-based analysis to determine the feasibility of uniting land surface temperature and public weather station data. The desktop review of cities determined that while each city has begun to implement numerous socially driven initiatives and large-scale green infrastructure plans, there is little work incorporating urban form within these strategies. Additionally, while the land surface temperature and weather station maps from the remote sensing analysis were deemed insufficient, several valuable questions and findings arose through the process. The case study analysis of Metro Boston identified three predominant urban forms in the study area and 12 sites were studied in relation to their heat performance in the morning, afternoon, and evening. The heat maps applied were developed through Heat Watch Report, a collaboration between the National Oceanic and Atmospheric Administration, the municipalities of Boston, Brookline, and Cambridge, and CAPA Strategies. The analysis revealed there is a universal change in temperature among all forms throughout the day, with peak temperatures occurring in the late afternoon period. The study also concluded that while temperature between forms was not significant, variation between sites of the same form was observed, with internal vegetation composition (NDVI) and neighboring landcover and urban form becoming key factors in increasing or reducing experienced heat. / Svårighetsgraden av extrema värmehändelser i kombination med stadens värmeöeffekt kan inte överskattas eftersom dessa effekter är betydande och utbredda, vilket påverkar energibehov, transportsystem, luft- och vattenkvalitet och framför allt orsakar värmerelaterade sjukdomar och dödsfall. Dessa konsekvenser visar tydligt vikten av att minska värmen i stadsområden samt se till att stadsbefolkningarna är säkra under extrema värmehändelser. För att både minska stadens värmeöeffekt och förbereda städer för en varmare framtid är det avgörande att fördjupa vår förståelse för städer i riskzon och förhållandet mellan värme och stadsmiljö.  Denna avhandling tillämpar urban morfologiteori och fjärranalys tekniker för att utforska hur urbana typologier i Metro Boston presterar under en extrem värmehändelse. I avhandlingen ingår en litteraturöversikt som utforskar stadsvärmemetoder och stadsmorfologi, en undersökning av en uppsättning av städers klimatinsatsrapporter och en fjärravkänningsbaserad analys för att undersöka genomförbarheten att förena markytstemperaturen och offentliga väderstationsdata. Undersökningen av stadsklimatrapporterna visade att även om varje stad har börjat genomföra många socialt drivna initiativ och storskaliga gröna infrastrukturplaner, finns det i dagsläget lite arbete kring integrerande av stadsform i dessa strategier. Även om markytstemperaturen och väderstationskartan från fjärranalysanalysen ansågs otillräckliga uppstod flera värdefulla frågor och fynd genom processen.  Fallstudieanalysen av Metro Boston identifierade tre dominerande urbana former i studieområdet och 12 platser studerades i förhållande till deras värmeprestanda på morgonen, eftermiddagen och kvällen. De värmekartor som tillämpades utvecklades genom Heat Watch Report, ett samarbete mellan National Oceanic and Atmospheric Administration, kommunerna Boston, Brookline och Cambridge och CAPA Strategies. Analysen avslöjade en universell temperaturförändring bland alla former under dagen, med topptemperaturer som inträffar under sen eftermiddagsperiod. Studien visar också att medan temperaturskillnaderna mellan formerna inte var signifikanta, observerades variation mellan platser med samma form, med intern vegetationssammansättning och angränsande marktäkning och urban form som nyckelfaktorer för en ökad eller minskad upplevd värme.

Human interference with the Earth’s climate, through the release of greenhouse gasses (GHGs), is estimated to have already increased average statewide temperatures in California by 1.7° Fahrenheit (F), with a further 2.7°F of warming expected by mid-century. The negative impacts of increased temperatures may be especially acute in mid-latitude cities that currently enjoy a mild climate, such as Los Angeles (LA), which are projected to warm to a point that will significantly affect human health and well being. The built environment increases urban temperatures through building materials that readily absorb heat from the sun, a lack of vegetation, a lack of pervious surface area, and anthropogenic heat. Local governments can take action to help their cities adapt to future temperatures through changes to building materials, urban design and infrastructure. This study evaluates six urban design strategies for reducing temperatures and therefore adapting to increased heat in LA: cool roofs, cool pavements, solar panels, tree planting, structural shading and green roofs. The methods used in this analysis include a cost-effectiveness analysis, key stakeholder interviews, and case studies from other cities in the US. Findings indicate that cool roofs are the most cost-effective strategy for urban heat island mitigation, with cool pavements and tree planting also cost-effective. Findings from stakeholder interviews indicate that political feasibility is high for all strategies except structural shading, which was thought to be costly and difficult to implement. However, significant political barriers were also identified for tree planting and green roofs. Findings from four case studies indicate that climate adaptation policies should emphasize co-benefits, include flexible design standards, and provide financial or performance-based incentives for property owners or developers. Specific recommendations for implementing climate adaptation measures are provided for urban planners, policy makers, urban designers and architects in Los Angeles.

No description available.

This thesis investigates the impact of Green Infrastructure (GI) and Local Climate Zones (LCZs) on air temperature at 2 meters above the ground (T2m) in Norrköping and Linköping, Sweden, with a focus on urban planning and climate resilience strategies. Two concepts of LCZ and the newly developed “3-30-300” GI rule are applied. Two concepts are evaluated under summer 2018 strong heatwave conditions and project future scenarios with a 3°C rise in global temperatures during extreme heatwaves. The results show an increase in mean temperature of about 2.9 °C and an extended duration of heatwaves in 17 days from the summer of 2018 to the possible future. Findings indicate that urban areas adhering to 30% tree canopy coverage and within 300 meters or less of a park show a 0.7°C reduction in median T2m during heatwaves. LCZs with more natural environments and less paved surfaces, such as open low-rise, sparsely built, and open midrise, exhibit lower air temperatures, while densely built areas (compact high-rise) show higher temperatures at night, and wide-open paved areas (large low-rise, heavy industry) show higher temperatures during days. The study underscores the necessity of increasing GI coverage and parks in both cities, highlighting the challenges of equitable GI distribution. Recommendations for future research include selecting cooling-effective indigenous tree species and expanding the scope to additional climate variables. This work provides crucial insights for urban areas in Nordic countries and similar climates, contributing to sustainable urban planning and enhanced climate resilience.

published_or_final_version / abstract / Architecture / Doctoral / Doctor of Philosophy

In 2005, Hurricane Katrina’s diverse impacts on the Greater New Orleans area included damaged and destroyed trees, and other despoiled vegetation, which also increased the exposure of artificial and bare surfaces, known factors that contribute to the climatic phenomenon known as the urban heat island (UHI). This is an investigation of UHI in the aftermath of Hurricane Katrina, which entails the analysis of pre and post-hurricane Katrina thermal imagery of the study area, including changes to surface heat patterns and vegetative cover. Imagery from Landsat TM was used to show changes to the pattern and intensity of the UHI effect, caused by an extreme weather event. Using remote sensing visualization methods, field data, and local knowledge, the author found there was a measurable change in the pattern and intensity of the New Orleans UHI effect, as well as concomitant changes to vegetative land cover. This finding may be relevant for urban planners and citizens, especially in the context of recovery from a large-scale disaster of a coastal city, regarding future weather events, and other natural and human impacts.

O objeto deste trabalho é o desempenho térmico da produção recente de edifícios residenciais multifamiliares em São Paulo, lançados entre 2005 e 2014, considerando o contexto urbano e climático em transição, visando às condições de conforto térmico. O objetivo é quantificar, por meio de estudos paramétricos com simulações computacionais termodinâmicas, o efeito de elementos, tanto intrínsecos quanto externos, aos edifícios sobre as condições de conforto térmico no clima atual e, em um segundo momento, no futuro (cerca de 50 anos à frente) identificando as melhores estratégias de projeto e operação para o conforto térmico. A hipótese é de que algumas práticas de projeto e operação correntes nos edifícios residenciais multifamiliares, que incluem o uso da varanda como ambiente interno da unidade e a vedação envidraçada de maiores proporções, tudo isso conjugado com as pequenas dimensões das unidades e os decorrentes prejuízos à ventilação natural, fazem com que esse estoque edificado, operando em modo naturalmente ventilado, apresente um desempenho térmico insatisfatório para o conforto térmico, e que isso vai ocorrer em uma parcela considerável do tempo de uso. No entanto, a varanda, valorizada nos edifícios residenciais multifamiliares verticais recentes, quando usada de fato como elemento de transição, consegue ser o vetor de melhoria do conforto térmico interno através da promoção de diferentes possibilidades de operação, incluindo sombreamento e ventilação. O estudo parte de uma leitura de grandes temas relacionados, passa por estudos de casos reais de apartamentos residenciais e estudos de clima urbano e realiza simulações computacionais termodinâmicas de desempenho térmico de uma unidade residencial considerada representativa da produção recente do mercado imobiliário de edifícios verticais multifamiliares. O método é indutivo, por meio de levantamentos de dados e elaboração de um modelo representativo (Ap Base) para as simulações computacionais, e dedutivo, por meio de comparações entre os diversos resultados obtidos pelas simulações computacionais nas diferentes configurações propostas. Dos estudos de simulação computacional depreende-se que, para os padrões construtivos de unidades residenciais em edifícios verticais praticados pelo mercado, alcançar o conforto ambiental em modo de operação naturalmente ventilado será um desafio de maiores dimensões nos cenários de aquecimento global e urbano vislumbrados. A diminuição de massa térmica aliada ao aumento das superfícies envidraçadas não sombreadas e reduzidas possibilidades de ventilação nos ambientes são os principais fatores que contribuem para o aquecimento em edificações. A presença da varanda, por sua vez, é positiva quando ela assume diversas possibilidades de configuração, atuando e sendo ocupada como um ambiente de transição de fato e não como um dos cômodos internos à residência; deste modo ela pode ser vetor das melhores práticas de operação na busca do conforto térmico. Portanto, os resultados comprovam a hipótese inicial, destacando-se que elementos que possibilitem a operação das aberturas, em especial aquelas ligadas à varanda, a saber, envidraçamento externo, porta entre varanda e estar e elemento sombreador externo, precisam estar disponíveis para serem operados pelo usuário, que deve estar apto a perceber as melhores possibilidades de operação e realizá-las. / The objective of this work is the thermal performance of the recent multifamily residential building production in São Paulo, launched between 2005 and 2014, considering the urban and the transition climate contexts aiming at the thermal comfort conditions. The objective is to quantify, through parametric studies using thermodynamic computational simulations, the effect of both intrinsic and external elements on the thermal comfort conditions in the current climate and, in a second moment, in the future about 50 years ahead, identifying the best design and operation strategies for the thermal comfort. The hypothesis is that some current design and operation practices in multifamily residential buildings, which include the use of the balcony as an interior environment and the large glass enclosures combined with the apartment\'s small area and the insufficient natural ventilation possibilities, result in poor thermal comfort performance of this free running building stock in a considerable part of its lifespan. However, the balcony, valued in the recent multi-family residential buildings, when in fact used as a transition space, can be the vector of internal thermal comfort improvements by promoting different operation possibilities, including shading and ventilation. This study starts from a broader context, observing real residential apartments\' study cases, going into urban climate studies and performing thermodynamic simulations of a residential apartment considered representative of the recent vertical multifamily building production of the local real estate market. The method is inductive, through data surveys and elaboration of a representative model (Ap Base) for the simulations, and deductive, through comparisons between the several results obtained by the simulations in the different configurations proposed. From the simulation studies, it can be concluded that, for the building standards of residential apartments in vertical buildings practiced by the market, achieving thermal comfort in free running mode will be a major challenge in the envisioned global and urban heating scenarios. The decrease of the thermal mass coupled with the unshaded large glazed surface area and reduced ventilation possibilities are the main factors for the building heating. The balcony, in turn, is positive when it assumes several configuration possibilities, acting and being occupied as a transitional environment in fact and not as an interior room; in this way it can be a vector of the best operating practices in the search for thermal comfort. Therefore, the results confirm the initial hypothesis, emphasizing that elements allowing the opening operation, especially the ones connected to the balcony, namely external glazing, door between balcony and living room and external shade element, must be available to be operated by the user, who must be able to perceive the best possible operation and perform it.

Le phénomène d’ilot de chaleur urbain « ICU » souvent observé dans les villes à forte densité urbaine, provoque des impacts négatifs surtout sur le confort thermique extérieur et sur la consommation énergétique des bâtiments. D’où l’importance d’intégrer des dispositifs d’atténuation de ce phénomène dans la conception des projets et des espaces urbains. Cette thèse vise à étudier les effets des différentes stratégies de limitation d’ICU sur les paramètres microclimatiques sous climat méditerranéen. Le cas étudié est un quartier compact de la ville libanaise Beyrouth qui est classifié comme un territoire artificialisé. Jusqu’à présent, peu de recherches microclimatiques ont été réalisées pour le cas Libanais et il y absence des codes et des mesures d’adaptation luttant contre l’ICU. Des simulations numériques sont réalisées à l’aide d’un outil microclimatique « ENVI-met », permettant d’identifier le potentiel rafraichissant de chaque stratégie proposée. Ces stratégies sont basées sur l’augmentation de l’albédo des revêtements du sol et de l’enveloppe des bâtiments, l’augmentation des espaces verts et des surfaces végétalisées, ainsi que sur la mise en place des sources d’eau comme les fontaines et les brumisateurs. Les charges de climatisation relatives à chaque mesure d’atténuation ont été évaluées à l’aide du couplage des données extraites avec ENVI-met avec le logiciel Hourly Analysis Program. Le travail de cette thèse a présenté la capacité des scenarios proposés à modifier les charges de climatisation sensibles ainsi que celles latentes. Le confort du piéton est aussi étudié en analysant l’indice de confort PET. / The urban heat island "UHI" phenomenon, frequently detected in cities with high urban density, leads to negative impacts especially on outdoor thermal comfort and buildings energy consumption. Accordingly, it is important to integrate mitigation measures into the design of projects and urban spaces. This thesis aims to study the effects of different UHI limitation strategies on microclimatic parameters in Mediterranean climate. The case of study is a com pact district of the Lebanese city Beirut which is classified as an artificial territory. Little microclimatic researches have been done for the Lebanese case and there is a lack of codes and adaptation measures to mitigate the effect of UHI. Numerical simulations are realized using "ENVI-met" software, to identify the cooling potential of each proposed strategy. These strategies are based on increasing the albedo of urban surfaces and buildings facades and roofs, increasing green spaces and vegetation surfaces, as well as the implementation of water sources such as fountains and water sprays. The cooling loads for each mitigation strategy were evaluated by linking ENVI-met results to the “Hourly Analysis Program” software. This thesis presented the capacity of the proposed scenarios to modify the sensible and latent cooling loads. The pedestrian comfort is also studied by analyzing the index of comfort PET.