Thesis (M. Sc. (Statistics)) -- University of Limpopo, 2020 / The main purpose of modelling rare events such as heavy rainfall, heat waves, wind speed, interest rate and many other rare events is to try and mitigate the risk that might arise from these events. Heavy rainfall and floods are still troubling many countries. Almost every incident of heavy rainfall or floods might result in loss of lives, damages to infrastructure and roads, and also financial losses. In this dissertation, the interest was in modelling average monthly rainfall for South Africa using extreme value theory (EVT). EVT is made up mainly of two approaches: the block maxima and peaks-over thresh old (POT). This leads to the generalised extreme value and the generalised Pareto distributions, respectively. The unknown parameters of these distri butions were estimated using the method of maximum likelihood estimators in this dissertation. According to goodness-of-fit test, the distribution in the Weibull domain of attraction, Gumbel domain and generalised Pareto distri butions were appropriate distributions to model the average monthly rainfall for South Africa. When modelling using the POT approach, the point process model suggested that some areas within South Africa might experience high rainfall in the coming years, whereas the GPD model suggested otherwise. The block maxima approach using the GEVD and GEVD for r-largest order statistics also revealed similar findings to that of the GPD. The study recommend that for future research on average monthly rainfall for South Africa the findings might be improved if we can invite the Bayesian approach and multivariate extremes. Furthermore, on the POT approach, time-varying covariates and thresholds are also recommended. / National Research Foundation (NRF) and South African Weather Service (SAWS)

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.

No description available.

Humans’ ability to combat heat stress through sweat-based evaporative cooling is modulated by air temperature and humidity, rendering human health highly sensitive to humid heat extremes. While the field of climate science has studied extreme dry bulb temperatures for decades, exploration of the physical drivers producing extreme humid heat is nascent in comparison. Two major areas of development for the evolving field are: 1) improving understanding of the local drivers of extreme humid heat, and 2) collating a set of universal physical mechanisms which generate humid heat extremes across the planet. The four chapters of this dissertation together advance each of these goals. Chapter 1 relates the occurrence of extreme humid heat in the Persian Gulf and South Asia to two related modes of intraseasonal climate variability, namely the Madden–Julian oscillation (MJO) and the boreal summer intraseasonal oscillation (BSISO). Wet bulb temperatures (Tw) sufficiently high to impact human health are found to be almost twice as likely during certain oscillation phases than in others. Humid heat anomalies in each region are driven by distinct local circulation patterns and variations in moisture. Chapter 2 evaluates the influence of monsoon onset and subseasonal precipitation variability on the occurrence of extreme Tw across South Asia. Extreme Tw events often occur on rainy days during the monsoon season. However, the influence of precipitation on Tw varies with the background specific humidity climatology. In climatologically drier areas, positive Tw anomalies tend to occur when precipitation increases due to either early onset or wet spells during the monsoon. In contrast, in climatologically humid areas, positive Tw anomalies occur during periods of suppressed precipitation, including delayed onset and dry spells during the monsoon. Chapter 3 analyzes the dynamics of the record-breaking extreme heat event in Rio de Janeiro in November 2023. The heatwave was associated with persistent atmospheric blocking, potentially linked to developing El Niño conditions. Temperatures were intensified by declining soil moisture and elevated local sea surface temperatures, and the event was finally terminated due to the onset of precipitation. This chapter also evaluates the influence of climate change on the frequency of heat extremes, finding a significant increase in the frequency of high heat days throughout Brazil over the past four decades. Further, the frequency of spring heat extremes is expected to increase in the future, though highly dependent upon our future emissions pathway. Chapter 4 explores the combinations of temperature and humidity contributing to humid heat experienced across the globe. In addition to using traditional metrics, this chapter derives a novel variable named “stickiness,” which quantifies the relative contributions of temperature and specific humidity to a given Tw. Consistent across metrics, high magnitudes of Tw tend to occur in the presence of anomalously high moisture, with temperature anomalies of secondary importance. Nonetheless, there is a broad range of stickiness observed for a given Tw across moderate-to-high Tw thresholds relevant to socioeconomic impacts.

As ondas de calor constituem sequências extremas de elevadas temperaturas que podem causar prejuízos biológicos, econômicos e sociais, desta forma demandando discussões em planejamentos estratégicos para a manutenção do funcionamento social. No entanto, inexistem trabalhos que as abordem historicamente em suas complexidades estatísticas, sinóticas e termodinâmicas em toda a extensão da América do Sul (AS), sendo os estudos ora restritivos no tempo, ora restritivos no espaço. Esta dissertação identifica e analisa as ondas de calor sobre a AS em suas distintas áreas de atuação regional, para um período de 30 anos, fazendo uso dos dados diários de reanálise do European Centre for Medium-Range Weather Forecasts (ECMWF), com resolução de 0,75° na área delimitadas pelas coordenadas (60°S15°N) e (8530°W). Para isto adota um critério de identificação objetivo e consistente com a variabilidade da extensão temporal e da intensidade das anomalias positivas de temperaturas, discutindo os aspectos metodológicos não consensuais presentes na literatura. As ondas de calor foram agrupadas segundo os padrões de variabilidade guiados por fenômenos atmosféricos específicos, em uma nova técnica alternativa ao uso das Funções Ortogonais Empíricas, derivada dos mapas de correlações espaciais. Os resultados mostram que as ondas de calor acontecem em qualquer época do ano, preferencialmente no período climatológico de maiores temperaturas; além disso, sua frequência está aumentando com o passar dos anos na AS. Para completar, os mapas de composições das climatologias sinóticas permitem identificar sistemas meteorológicos específicos para cada uma das dez regiões homogêneas identificadas, alguns deles relacionados ao fenômeno El Niño Oscilação-Sul e a padrões determinados de circulação atmosférica, precipitação e Temperatura da Superfície do Mar. Tendo em vista a possibilidade de inclusão da mesma técnica aos estudos globais e para as ondas de frio, este trabalho se insere no início de uma vasta gama de estudos inter-relacionados, dentro do contexto das mudanças climáticas e de considerável interesse socioeconômico envolvido. / Heat waves constitute extreme sequences of high temperatures that can cause biological, economic, and social damages, thus requiring strategic planning discussion for social functioning maintenance. However, there are no papers addressing them from a historical point of view in their statistical, synoptic, and thermodynamic complexities throughout South America (SA), being the studies sometimes restrictive in time, and sometimes restrictive in space. This dissertation identifies and analyses the SA heat waves over their regional areas, for a period of 30 years, making use of reanalysis daily data of European Centre for Medium-Range Weather Forecasts (ECMWF), with 0.75° resolution over the area delimited by the coordinates ranges (60°S15°N) and (8530°W). To do that, it adopts an objective identification criterion consistent with the variability of the temporal extension and the intensity of the positive anomalies of temperatures, discussing the nonconsensual methodological aspects present in the literature. The heat waves were grouped according to the variability patterns guided by specific atmospheric phenomena, in a new alternative technique to the use of the Empirical Orthogonal Functions, derived from the maps of spatial correlations. The results show that the heat waves happen at any time of the year, preferably in the climatic period of higher temperatures; in addition, its frequency is increasing over the years in AS. To complete, the correlation maps of synoptic climatology allow the identification of specific meteorological systems in each of the ten identified homogeneous region, some of them related with El Niño Southern Oscillation and with determined patterns of atmospheric circulation, precipitation, and Sea Surface Temperature. Considering the possibility of including the same technique in global studies and in the case of cold waves, this work is part of a wide range of interrelated studies within the context of climate change and considerable socioeconomic interest involved.

As ondas de calor constituem sequências extremas de elevadas temperaturas que podem causar prejuízos biológicos, econômicos e sociais, desta forma demandando discussões em planejamentos estratégicos para a manutenção do funcionamento social. No entanto, inexistem trabalhos que as abordem historicamente em suas complexidades estatísticas, sinóticas e termodinâmicas em toda a extensão da América do Sul (AS), sendo os estudos ora restritivos no tempo, ora restritivos no espaço. Esta dissertação identifica e analisa as ondas de calor sobre a AS em suas distintas áreas de atuação regional, para um período de 30 anos, fazendo uso dos dados diários de reanálise do European Centre for Medium-Range Weather Forecasts (ECMWF), com resolução de 0,75° na área delimitadas pelas coordenadas (60°S15°N) e (8530°W). Para isto adota um critério de identificação objetivo e consistente com a variabilidade da extensão temporal e da intensidade das anomalias positivas de temperaturas, discutindo os aspectos metodológicos não consensuais presentes na literatura. As ondas de calor foram agrupadas segundo os padrões de variabilidade guiados por fenômenos atmosféricos específicos, em uma nova técnica alternativa ao uso das Funções Ortogonais Empíricas, derivada dos mapas de correlações espaciais. Os resultados mostram que as ondas de calor acontecem em qualquer época do ano, preferencialmente no período climatológico de maiores temperaturas; além disso, sua frequência está aumentando com o passar dos anos na AS. Para completar, os mapas de composições das climatologias sinóticas permitem identificar sistemas meteorológicos específicos para cada uma das dez regiões homogêneas identificadas, alguns deles relacionados ao fenômeno El Niño Oscilação-Sul e a padrões determinados de circulação atmosférica, precipitação e Temperatura da Superfície do Mar. Tendo em vista a possibilidade de inclusão da mesma técnica aos estudos globais e para as ondas de frio, este trabalho se insere no início de uma vasta gama de estudos inter-relacionados, dentro do contexto das mudanças climáticas e de considerável interesse socioeconômico envolvido. / Heat waves constitute extreme sequences of high temperatures that can cause biological, economic, and social damages, thus requiring strategic planning discussion for social functioning maintenance. However, there are no papers addressing them from a historical point of view in their statistical, synoptic, and thermodynamic complexities throughout South America (SA), being the studies sometimes restrictive in time, and sometimes restrictive in space. This dissertation identifies and analyses the SA heat waves over their regional areas, for a period of 30 years, making use of reanalysis daily data of European Centre for Medium-Range Weather Forecasts (ECMWF), with 0.75° resolution over the area delimited by the coordinates ranges (60°S15°N) and (8530°W). To do that, it adopts an objective identification criterion consistent with the variability of the temporal extension and the intensity of the positive anomalies of temperatures, discussing the nonconsensual methodological aspects present in the literature. The heat waves were grouped according to the variability patterns guided by specific atmospheric phenomena, in a new alternative technique to the use of the Empirical Orthogonal Functions, derived from the maps of spatial correlations. The results show that the heat waves happen at any time of the year, preferably in the climatic period of higher temperatures; in addition, its frequency is increasing over the years in AS. To complete, the correlation maps of synoptic climatology allow the identification of specific meteorological systems in each of the ten identified homogeneous region, some of them related with El Niño Southern Oscillation and with determined patterns of atmospheric circulation, precipitation, and Sea Surface Temperature. Considering the possibility of including the same technique in global studies and in the case of cold waves, this work is part of a wide range of interrelated studies within the context of climate change and considerable socioeconomic interest involved.

No description available.

Orientador: João Lima Sant'Anna Neto / Resumo: Nos últimos anos as mudanças climáticas têm sido foco de diversas pesquisas de cunho científico e político principalmente após as publicações dos relatórios desenvolvidos pelo IPCC. Segundo o grupo, e fato incontestável para muitos pesquisadores, as mudanças climáticas deverão aumentar consideravelmente o número e intensidade dos eventos meteorológicos extremos. Contudo, tais repercussões não ocorrerão em todos os espaços e com intensidades equivalentes. Cada grupo de acordo com o seu poder aquisitivo, forma organizacional, processo histórico e cultural percebem a eminência do risco de modo singular e, da mesma forma, em um futuro próximo, responderão de modo desigual a partir de mecanismos capazes de se precaverem com maior ou menor resiliência à essas repercussões. Diante desta discussão esta pesquisa teve o objetivo de analisar e pesquisar as repercussões dos eventos extremos, associados a temperatura (frio e calor) e condições de conforto térmico humano e bairros com diferentes padrões socioeconômicos na cidade de Presidente Prudente. A hipótese dessa pesquisa é que a população residente nos setores menos valorizados e mais segregados socio-economicamente é também a camada mais vulnerável e afetada, negativamente, por essas ocorrências extremas e com impactos significativos no conforto térmico e saúde. Para contemplar este universo de análise a pesquisa é composta por três vertentes principais: análise dos eventos extremos de frio e calor e a influência na biometeorologia... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In recent years, climate changes have been the focus of several scientific and political research studies, especially after the publication of reports elaborated by the IPCC. According to the group, as well as an unquestionable fact for many researchers, climate changes should considerably increase the number and intensity of extreme weather events. However, such repercussions will not occur in all spaces and with equivalent intensities. Each group, according to their purchasing power, organizational form, historical and cultural process, perceives the eminence of risk in a unique way and, in the near future, will respond unequally through mechanisms that will be able to be cautious with more or less resilience about these repercussions. Given this discussion, this research aimed to analyze and research the repercussions of extreme events associated with temperature (cold and heat) and conditions of thermic comfort in differents socioeconomic districts in the Presidente Prudente city. The hypothesis of this research is that the population residing in the least valued and most socially and economically segregated sectors is also the most vulnerable and negatively affected by these extreme occurrences layer, with significant impacts on thermal comfort and health. In order to contemplate this universe of analysis, the research consists of three main strands: analysis of extreme cold and heat events and the influence on human biometeorology through thermal comfort and discomfort;... (Complete abstract click electronic access below) / Doutor

Made available in DSpace on 2014-08-20T14:25:47Z (GMT). No. of bitstreams: 1 dissertacao_mari_firpo.pdf: 1272617 bytes, checksum: f59407ea3e3a879715dca6636c682cbe (MD5) Previous issue date: 2008-02-15 / In this paper the results of Cold and heat waves and their relationships with to El Niño and La Niña events in 13 meteorological stations in Rio Grande do Sul along the years of 1967 up to 2005 are presented. Daily frost and maximum and minimum air temperature data were used. The anomalies were obtained subtracting the average year (climatological normal to the data set) of each year which was analyzed. Cold waves were considered the period of five or more days of consecutive negative minimum temperature and hot waves for the same time but in positive anomalies and maximum temperature. It was also used a quantil technique to split in quartile segments the highest anomalies values and the anomalies interval values of each wave in order to classify them according to its intensity and termic amplitude respectively. Only the waves of five days were classified. Analyzing the waves average behavior it was observed that the cold ones happen more in the winter and that there is an homogeneity related to its distribution in the state. On the other hand, the heat waves happen also in the colder months, but their distribution is heterogeneous, happening more in the meteorological stations located more in the northern part of the state. The relationships between frosts and waves it was noticed that there is a positive correlation between the frosts average number and the cold waves and negatives average number to the heat ones, statistically significant at 1% level in the months of June and July, but not in August. The relationships between cold and heat waves and the ENSO events show that, in general, the occurrence of La Niña increases the number of cold waves and decreases the heat waves in Rio Grande do Sul, while the El Niño increases the heat waves and decreases the cold waves. It was also analyzed the frost relationships with ENSO events and it was noted that in the months of June and July there is a higher occurrence of frosts during La Niñas. However, in August this occurrence is higher during El Niños / Neste trabalho são apresentados os resultados do estudo feito sobre a ocorrência de ondas de frio e calor e suas relações com El Niño e La Niña, em 13 estações meteorológicas do Rio Grande do Sul para o período entre os anos de 1967 a 2005. As anomalias foram obtidas subtraindo-se o ano médio (normal climatológica para a série de dados) de cada ano em questão. Foram consideradas ondas de frio, os períodos de cinco ou mais dias consecutivos de anomalias negativas de temperatura mínima e ondas de calor, o mesmo período de anomalias positivas de temperatura máxima. Foi utilizada a técnica dos quantis para dividir, em ordens quartílicas, os maiores valores de anomalias e os valores de intervalo de anomalias de cada onda, a fim de classificá-las quanto a intensidade e a amplitude térmica, respectivamente. Apenas as ondas de 5 dias foram classificadas. Analisando o comportamento médio das ondas, observou-se que as de frio ocorrem mais no inverno e que há uma homogeneidade quanto à sua distribuição no Estado. Já as ondas de calor também ocorrem mais nos meses mais frios, mas sua distribuição é heterogênea, ocorrendo em maior quantidade nas estações meteorológicas localizadas mais ao norte do Estado. Notou-se que há uma correlação positiva entre o número médio de geadas e o número médio de ondas de frio e negativa quanto as ondas de calor, significativas a 1% para os meses de junho e julho, mas não para o mês de agosto. As relações entre ondas de frio e calor e os eventos ENSO mostraram que, em geral, a ocorrência de La Niña faz aumentar o número de ondas de frio e diminuir o número de ondas de calor no Rio Grande do Sul, enquanto a ocorrência de El Niño faz aumentar o número de ondas de calor e diminuir as ondas de frio. Quanto às geadas, também foi analisada sua relação com os eventos ENSO e constatou-se que nos meses de junho e julho, há uma maior ocorrência de geadas nos meses de La Niña, porém, no mês de agosto, essa ocorrência é maior nos meses de El Niño

Heat waves represent a public health challenge that requires multiple responses and warnings to protect vulnerable populations. Although studies have reported an increasing trend of heat wave occurrence in many areas of the world, no clear trend exists in East Tennessee. Using data from Parameter-elevated Relationships on Independent Slope Models (PRISM), CDC WONDER and the United States Census Bureau, the relationship between mortality rates and year was estimated during heat wave events between 1999 and 2010. Five heat wave definitions were tested. Overall, 2007 and 2010 stand out as the years with the highest number of heat wave days in East Tennessee. August could be described as the hottest month. Three of the heat wave definitions tested show increasing non-accidental mortality rates with year. The relative risk for cardiovascular mortality is elevated among females compared to males for one of the heat wave definitions (Relative Risk (RR) = 1.33, CI= 1.08-1.65).