Remembering negative experiences with extreme heat may promote future protective actions and provide insight to improve heat risk awareness and communication practices. This two-part thesis found 1) that experiencing heat-related health symptoms predicted what Americans would do to protect themselves and others during subsequent heat waves; and 2) that Utah professionals regard heat-related experience as an important factor in how they responded to extreme heat events. In the first study, a US national survey showed that personal experience with heat-related health symptoms was related to the tendency to say that one engaged in different protective behaviors, while other factors like risk perception and temperature were less related to self-reported behaviors. Sociodemographic factors such as age, race, and gender were related to Americans’ reported efforts to check on other people during a heat wave—with African-Americans, women, and older adults being more likely to do so— but did not have much relationship with how people personally protect themselves. The second study found that heat experience was an important factor in how public officials and media broadcasters manage extreme heat situations. Interviews of professionals in Utah revealed that experience with heat impacts influenced public forecasters, practitioners, and media members alike in their heat risk decisions and messaging practices even though official heat risk communication products in Utah were somewhat unfamiliar. This study also found that public forecasters recently changed how they measure extreme heat to better communicate the dangers of dry heat in the Intermountain West. This change will likely cause more official heat alerts to be issued in this region.

This thesis evaluated physiological responses of young and older adults during extreme heat events and the extent to which commonly recommended heat-health guidelines (indoor temperature limits) and heat mitigation strategies (cooling centres) are effective at limiting hyperthermia and cardiovascular burden. A multidisciplinary narrative review and three experimental studies were conducted. In the review, the mechanisms by which aging impairs the regulation of body temperature and hemodynamic stability, and how they may contribute to the increased risk of heat-related mortality and morbidity in older adults, were summarized. A lack of ecologically minded study designs in previous research evaluating the physiological responses supporting homeostasis and health during heat stress (i.e., body temperature regulation and cardiovascular stability) was also identified. The three experiments were therefore designed as day-long (8-9 hour) extreme heat simulations to 1) evaluate age-related alterations in thermoregulatory and cardiovascular function during peak heat conditions; 2) assess how these responses translate to indoor environments; and 3) quantify the effectiveness of cooling centers, a widely recommended heat mitigation strategy, for limiting hyperthermia and cardiovascular burden. In the first study, healthy older adults (age: 64-78 years; n=19) stored 87 kJ [95% confidence limits: 33, 141] more heat than their younger (age: 19-31 years; n=20) counterparts (328 [71] kJ vs. 241 [SD: 87]; P<0.001) during the first three hours of a 9-hour exposure to extreme heat (40°C and 15% relative humidity). This resulted in a 0.4°C [0.2, 0.6] greater increase in body core temperature in the older adults that was maintained throughout exposure (1.0 [0.3] vs 0.6 [0.3]°C; P<0.001). These findings were extended in the second study, wherein it was demonstrated that healthy older adults (age: 66-78 years, n=8) exhibit progressive elevations in body temperatures (P<0.001) and attenuations in cardiovascular autonomic function (P<0.001) during 8 hours of rest in conditions representative of those experienced indoors during extreme heat events. These ranged from an actively cooled environment (22°C), through indoor temperature thresholds recommended by Toronto Public Health (26°C) and the World Health Organization (31°C), to poorly insulated and ventilated homes and/or dwellings without access to air conditioning (36°C; 45% relative humidity in all conditions). In the third study, it was shown that short-term exposure to a cool environment midway through (hours 5-6) a day-long (9 hour) simulated heat event reduced core temperature in a group of healthy older adults (age: 67-78 years; n=8) by 0.8°C [0.6, 1.0] compared to an age-matched group not removed from the heat (from study 1). Despite this, core temperature rose rapidly upon return to the heat and was statistically equivalent in both groups by the end of exposure (37.8 [0.3] vs 37.9 [0.3]°C; P=0.011). The findings of this thesis indicate that even healthy older adults experience sustained elevations in body temperature and cardiovascular burden during extreme heat events and that commonly recommended heat-health guidelines (indoor temperature limits) and mitigation strategies (cooling centres) may not provide adequate protection. Collectively, this work represents a considerable advance in our understanding of the physiological burden experienced by older adults during hot weather and extreme heat events.

As a result of climate change and urbanization, rising temperatures are causing increasing concern about extreme heat in cities worldwide. Urban extreme heat like other climate-related phenomena is a complex problem that requires expertise from a range of disciplines and multi-faceted solutions. Therefore, this study aims to develop a comprehensive understanding of urban heat issue by taking a multi-level approach that integrates science, technology, and policy. Throughout the three main papers of this dissertation, a variety of quantitative and qualitative methods, such as microclimate modeling, machine learning, statistical analysis, and policy content analysis, are used to analyze urban heat from different perspectives. The first paper of this dissertation focuses on the street canyon scale, aiming to identify the physical and vegetation parameters that have the greatest impact on changing thermal conditions in urban environments and to understand how these parameters interact with each other. Moving towards identifying applicable heat-related data and measurement techniques, the second paper assesses whether lower-resolution temperature data and novel sources of vulnerability indicators can effectively explain intra-urban heat variations. Lastly, the third paper of this dissertation reviews heat-related plans and policies at the Planning Districts level in Virginia, providing insights into how extreme heat is framed and addressed at the regional and local levels. This analysis is particularly important for states such as Virginia, which historically have not experienced multiple days of extreme heat during summers, as is common in southern and southwestern states of the United States. The results of this study provide insights into the contributing and mitigating factors associated with extreme heat exposure, novel heat-related data and measurement techniques, and the types of analysis and information that should be included in local climate-related plans to better address extreme heat. This dissertation explores new avenues for measuring, understanding, and planning extreme heat in cities, thereby contributing to the advancement of knowledge in this field. / Doctor of Philosophy / Due to climate change and fast city growth, temperatures are rising, and extreme heat is becoming a big worry in cities worldwide. Urban extreme heat is a challenging problem that needs expertise from different majors and diverse solutions. This dissertation aims to understand urban heat better by integrating science, technology, and policy. The three main research papers of this dissertation use various methods like modeling, statistics, and policy analysis to study urban heat from different angles. The first paper focuses on city streets and how certain physical features and vegetation affect citizens' thermal comfort. The second paper explores new ways to measure heat in urban areas, including using new sources of data and the application of lower-resolution data. Finally, the third paper reviews heat-related plans and policies in Virginia, helping us understand how extreme heat is addressed in areas that might not be accustomed to high temperatures. This dissertation's findings provide useful insights into why the severity of extreme heat is not the same in different parts of cities, present new ways to measure this difference and find solutions to lessen the negative impacts of exposure to heat. It also shows what information needs to be included in plans and policies to better deal with extreme hot weather at the local level such as in towns and cities. By exploring new ways to understand and handle extreme heat in cities, this research helps make progress in this important field. The goal of this research is to help cities prepare for and cope with urban extreme heat, keeping people safe and creating sustainable cities for the future.

abstract: This dissertation explores vulnerability to extreme heat hazards in the Maricopa County, Arizona metropolitan region. By engaging an interdisciplinary approach, I uncover the epidemiological, historical-geographical, and mitigation dimensions of human vulnerability to extreme heat in a rapidly urbanizing region characterized by an intense urban heat island and summertime heat waves. I first frame the overall research within global climate change and hazards vulnerability research literature, and then present three case studies. I conclude with a synthesis of the findings and lessons learned from my interdisciplinary approach using an urban political ecology framework. In the first case study I construct and map a predictive index of sensitivity to heat health risks for neighborhoods, compare predicted neighborhood sensitivity to heat-related hospitalization rates, and estimate relative risk of hospitalizations for neighborhoods. In the second case study, I unpack the history and geography of land use/land cover change, urban development and marginalization of minorities that created the metropolitan region's urban heat island and consequently, the present conditions of extreme heat exposure and vulnerability in the urban core. The third study uses computational microclimate modeling to evaluate the potential of a vegetation-based intervention for mitigating extreme heat in an urban core neighborhood. Several findings relevant to extreme heat vulnerability emerge from the case studies. First, two main socio-demographic groups are found to be at higher risk for heat illness: low-income minorities in sparsely-vegetated neighborhoods in the urban core, and the elderly and socially-isolated in the expansive suburban fringe of Maricopa County. The second case study reveals that current conditions of heat exposure in the region's urban heat island are the legacy of historical marginalization of minorities and large-scale land-use/land cover transformations of natural desert land covers into heat-retaining urban surfaces of the built environment. Third, summertime air temperature reductions in the range 0.9-1.9 °C and of up to 8.4 °C in surface temperatures in the urban core can be achieved through desert-adapted canopied vegetation, suggesting that, at the microscale, the urban heat island can be mitigated by creating vegetated park cool islands. A synthesis of the three case studies using the urban political ecology framework argues that climate changed-induced heat hazards in cities must be problematized within the socio-ecological transformations that produce and reproduce urban landscapes of risk. The interdisciplinary approach to heat hazards in this dissertation advances understanding of the social and ecological drivers of extreme heat by drawing on multiple theories and methods from sociology, urban and Marxist geography, microclimatology, spatial epidemiology, environmental history, political economy and urban political ecology. / Dissertation/Thesis / Ph.D. Environmental Social Science 2013

abstract: Environmental hazards and disaster researchers have demonstrated strong associations between sociodemographic indicators, such as age and socio-economic status (SES), and hazard exposures and health outcomes for individuals and in certain communities. At the same time, behavioral health and risk communications research has examined how individual psychology influences adaptive strategies and behaviors in the face of hazards. However, at present, we do not understand the explanatory mechanisms that explain relationships between larger scale social structure, individual psychology, and specific behaviors that may attenuate or amplify risk. Extreme heat presents growing risks in a rapidly warming and urbanizing world. This dissertation examines the social and behavioral mechanisms that may explain inequitable health outcomes from exposure to concurrent extreme heat and electrical power failure in Phoenix, AZ and extreme heat in Detroit, MI. Exploratory analysis of 163 surveys in Phoenix, AZ showed that age, gender, and respondent’s racialized group identity did not relate to thermal discomfort and self-reported heat illness, which were only predicted by SES (StdB = -0.52, p < 0.01). Of the explanatory mechanisms tested in the study, only relative air conditioning intensity and thermal discomfort explained self-reported heat illness. Thermal discomfort was tested as both a mechanism and outcome measure. Content analysis of 40 semi-structured interviews in Phoenix, AZ revealed that social vulnerability was associated with an increase in perceived hazard severity (StdB = 0.44, p < 0.01), a decrease in perceived adaptation efficacy (StdB = -0.38, p = 0.02), and an indirect increase (through adaptive efficacy) in maladaptive intentions (StdB = 0.18, p = 0.01). Structural equation modeling of 244 surveys in Phoenix, AZ and Detroit, MI revealed that relationships between previous heat illness experience, perceived heat risk, and adaptive intentions were significantly moderated by adaptive capacity: high adaptive capacity households were more likely to undertake adaptive behaviors, and those decisions were more heavily influenced by risk perceptions and previous experiences. However, high adaptive capacity households had lower risk perceptions and fewer heat illness experiences than low adaptive capacity households. A better understanding of the mechanisms that produce social vulnerability can facilitate more salient risk messaging and more targeted public health interventions. For example, public health risk messaging that provides information on the efficacy of specific adaptations may be more likely to motivate self-protective action, and ultimately protect populations. / Dissertation/Thesis / Doctoral Dissertation Environmental Social Science 2019

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.

The Earth's climate is changing and cities are facing a warmer future. As the locus of economic activity and concentrated populations on the planet, cities are both a primary driver of greenhouse gas emissions and places where the human health impacts of climate change are directly felt. Cities increase local temperatures through the conversion of natural land covers to urban uses, and exposures to elevated temperatures represent a serious and growing health threat for urban residents. This work is concerned with understanding the interactions of global trends in climate with local influences tied to urban land covers. First, it examines temperatures during an extended period of extreme heat and asks whether changes in land surface temperatures during a heat wave are consistent in space and time across all land cover types. Second, the influences of land covers on temperatures are considered for normal and extreme summer weather to find out which characteristics of the built environment most influence temperatures during periods of extreme heat. Finally, the distribution of health vulnerabilities related to extreme heat in cities are described and examined for spatial patterns. These topics are investigated using meteorology from the summer of 2006 to identify extremely hot days in the cities of Atlanta, Chicago, Philadelphia, and Phoenix and their surrounding metropolitan regions. Remotely sensed temperature data were examined with physical and social characteristics of the urban environment to answer the questions posed above. The findings confirm that urban land covers consistently exhibit higher temperatures than surrounding rural areas and are much more likely to be among the hottest in the region, during a heat wave specifically. In some cities urban thermal anomalies grew between the beginning and end of a heat wave. The importance of previously recognized built environment thermal influences (impervious cover and tree canopy) were present, and in some cases, emphasized during extreme summer weather. Extreme heat health health vulnerability related to environmental factors coincided spatially with risks related to social status. This finding suggests that populations with fewer resources for coping with extreme heat tend to reside in built environments that increase temperatures, and thus they may be experiencing increased thermal exposures. Physical interventions and policies related to the built environment can help to reduce urban temperatures, especially during periods of extremely hot weather which are predicted to become more frequent with global climate change. In portions of the city where populations with limited adaptive capacity are concentrated, modification of the urban landscape to decrease near surface longwave radiation can reduce the chances of adverse health effects related to extreme heat. The specific programs, policies, and design strategies pursued by cities and regions must be tailored with respect to scale, location, and cultural context. This work concludes with suggestions for such strategies.

No description available.

Indiana University-Purdue University Indianapolis (IUPUI) / Extreme Heat Events are the leading cause of weather-related mortalities in the continental United States. Recent publications have suggested that vulnerability to extreme heat is impacted by variations in environmental and socioeconomic conditions, even across small spatial units. This study evaluated the usefulness of socioeconomic variables and satellite-derived environmental measurements as predictors of heat-related vulnerability during the July 14-17, 1995 heat wave in Chicago, IL. Geospatial analysis and statistical processes were implemented to identify and rank characteristics of vulnerable populations. Results suggest population density, educational attainment, age, and financial indicators are among the best predictors of heat vulnerability. Proximity to and intensity of Urban Heat Islands also appears to influence neighborhood vulnerability levels. Identification and mapping of vulnerability variables can distinguish locations of increased vulnerability during extreme weather conditions. These vulnerability maps could be utilized by city officials to plan and implement aid programs to specific high risk neighborhoods before an extreme heat event, and resulting health implications, occur. Continued study and implementation of these variables could also assist in identifying vulnerable populations in other urban environments, improve utilization of location-specific heat warning systems and impact new building policies to decrease vulnerability variables across the country.

<div><br></div><div>Extreme heat is one of the deadliest health hazards that is projected to increase in intensity and persistence in the near future. Temperatures are further exacerbated in the urban areas due to the Urban Heat Island (UHI) effect resulting in increased heat-related mortality and morbidity. However, the spatial distribution of urban temperatures is highly heterogeneous. As a result, metrics such as UHI Intensity that quantify the difference between the average urban and non-urban air temperatures, often fail to characterize this spatial and temporal heterogeneity. My objective in this thesis is to understand and characterize the spatio-temporal dynamics of UHI for cities across the world. This has several applications, such as targeted heat mitigation, energy load estimation, and neighborhood-level vulnerability estimation.</div><div><br></div><div>Towards this end, I have developed a novel multi-scale framework of identifying emerging heat clusters at various percentile-based thermal thresholds T_thr and refer to them collectively as <i>intra-Urban Heat Islets</i>. Using the Land Surface Temperatures from Landsat for 78 cities representative of the global diversity, I have showed that the heat islets have a fractal spatial structure. They display properties analogous to that of a percolating system as T_thr varies. At the percolation threshold, the size distribution of these islets in all cities follows a power-law, with a scaling exponent = 1.88 and an aggregated Area-Perimeter Fractal Dimension =1.33. This commonality indicates that despite the diversity in urban form and function across the world, the urban temperature patterns are different realizations with the same aggregated statistical properties. In addition, analogous to the UHI Intensity, the mean islet intensity, i.e., the difference between mean islet temperature and thermal threshold, is estimated for each islet, and their distribution follows an exponential curve. This allows for a single metric (exponential rate parameter) to serve as a comprehensive measure of thermal heterogeneity and improve upon the traditional UHI Intensity as a bulk metric.</div><div><br></div><div><br></div><div>To study the impact of urban form on the heat islet characteristics, I have introduced a novel lacunarity-based metric, which quantifies the degree of compactness of the heat islets. I have shown that while the UHIs have similar fractal structure at their respective percolation threshold, differences across cities emerge when we shift the focus to the hottest islets (T_thr = 90^th percentile). Analysis of heat islets' size distribution demonstrates the emergence of two classes where the dense cities maintain a power law, whereas the sprawling cities show an exponential deviation at higher thresholds. This indicates a significantly reduced probability of encountering large heat islets for sprawling cities. In contrast, analysis of heat islet intensity distributions indicates that while a sprawling configuration is favorable for reducing the mean Surface UHI Intensity of a city, for the same mean, it also results in higher local thermal extremes. </div><div><br></div><div>Lastly, I have examined the impact of external forcings such as heatwaves (HW) on the heat islet characteristics. As a case study, the European heatwave of 2018 is simulated using the Weather Research Forecast model with a focus on Paris. My results indicate that the UHI Intensity under this HW reduces during night time by 1^oC on average. A surface energy budget analysis reveals that this is due to drier and hotter rural background temperatures during the HW period.</div><div>To analyze the response of heat islets at every spatial scale, power spectral density analysis is done. The results show that large contiguous heat islets (city-scale) persist throughout the day during a HW, whereas the smaller islets (neighborhood-scale) display a diurnal variability that is the same as non-HW conditions. </div><div><br></div><div>In conclusion, I have presented a new viewpoint of the UHI as an archipelago of intra-urban heat islets. Along the way, I have introduced several properties that enable a seamless comparison of thermal heterogeneity across diverse cities as well as under diverse climatic conditions. This thesis is a step towards a comprehensive characterization of heat from the spatial scales of an urban block to a megalopolis.</div><div><br></div>