Thesis (Ph. D.)--University of Washington, 1997. / Vita. Includes bibliographical references (leaves [138]-141).

Thesis (Ph. D.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 100-106). Also available on the World Wide Web.

Thesis (Ph. D.)--Oregon State University, 2001. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

Statistical models are necessary to quantify and understand the risk from natural hazards. A statistical framework is developed here to investigate the e ect of dependence between the frequency and intensity of natural hazards on the aggregate risk. The aggregate risk of a natural hazard is de ned as the sum of the intensities for all events within a season. This framework is applied to a database of extra tropical cyclone tracks from the NCEP-NCAR reanalysis for the October to March extended winters between 1950 and 2003. Large positive correlation is found between cyclone counts and the local mean vorticity over the exit regions of the North Atlantic and North Paci c storm tracks. The aggregate risk is shown to be sensitive to this dependence, especially over Scandinavia. Falsely assuming independence between the frequency and intensity results in large biases in the variance of the aggregate risk. Possible causes for the dependence are investigated by regressing winter cyclone counts and local mean vorticity on teleconnection indices with Poisson and linear models. The indices for the Scandinavian pattern, North Atlantic Oscillation and East Atlantic Pattern are able to account for most of the observed positive correlation over the North Atlantic. The sensitivity of extremes of the aggregate risk distribution to the inclusion of clustering, with and without frequency intensity dependence, is investigated using Cantelli bounds and a copula simulation approach. The inclusion of dependence is shown to be necessary to model the clustering of extreme events. The implication of these ndings for the insurance sector is investigated using the loss component of a catastrophe model. A mixture model approach provides a simple and e ective way to incorporate frequency-intensity dependence into the loss model. Including levels of correlation and overdispersion comparable to that observed in the reanalysis data results in an average increase of over 30% in the 200 year return level for the aggregate loss.

Thesis (M.S.)--Florida State University, 2006. / Advisor: Robert Hart, Florida State University, College of Arts and Sciences, Dept. of Meteorology. Title and description from dissertation home page (viewed Sept. 26, 2006). Document formatted into pages; contains xiii, 98 pages. Includes bibliographical references.

Maximum sustained and peak gust winds from eighteen European windstorms over the last 25 years were analyzed previously to develop surface-level wind predictions across a large and topographically varied landscape based on an anisotropic kriging interpolation methodology for meteorological station data. Results suggested that coastal and mountainous areas experience the highest wind speeds and highest variability over short distances, resulting in the highest errors across concurrent interpolated surfaces. This study utilizes covariates in conjunction with cokriging to investigate the use of cokriging as a method of improvement through the interpolation of five windstorms that impacted both the Alps region and the topographically-varied coastal regions of Western Europe. Results show that cokriging improves isotach interpolation for windstorms in 8 out of 10 models by reducing root mean square error and the total number of high-error stations, primarily in coastal and mountainous areas. Land cover alone contributed to the greatest model improvement in a majority of the models, while aspect and elevation (singularly and collectively) also improved models when compared to original kriging models. Improved surface interpolation is critical for improved understanding of macro-scale windstorm patterns and resulting damage, thus improving risk and vulnerability estimates.

No description available.

Le travail de recherche appliquée réalisé au cours du doctorat s’intéresse aux tempêtes hivernales à fort potentiel d’impact économique en Europe et comprend deux parties. La première partie vise à quantifier l’impact du changement climatique sur les tempêtes de vent hivernales extrêmes en Europe et s’appuie sur des données couvrant des périodes supérieures à 30 ans. La seconde partie du travail est plus opérationnelle et a pour objectif l’élaboration et la mise en place d’un outil de détection des tempêtes de vent hivernales en Europe à partir de prévisions météorologiques actualisées toutes les six heures. L’objectif général de la première partie du travail de recherche est d’apporter une vision moyen-terme de ce que pourraient être les tempêtes de vent hivernales en Europe au cours du XXIe siècle. Ce travail vient compléter la vision pour l’instant principalement court-terme du risque proposée par les modèles CatNat, utilisés par les (ré)assureurs pour connaître le coût du risque sur leur portefeuille. Au cours du travail de recherche, une nouvelle méthode a été proposée pour définir le potentiel de dommages associés à une tempête de vent en Europe. L’idée originale développée au cours du projet est l’utilisation de plusieurs variables capturant différentes échelles spatio-temporelles et prenant en compte la relation entre plusieurs variables caractéristiques d’un même cyclone extratropical. La recherche d’événements partageant une signature similaire et intense, simultanément dans la vorticité relative à 850 hPa, la pression au niveau de la mer et le vent de surface, conduit à la détection d’un nombre réduit d’événements. La comparaison du nombre d’événements qui constituent ce groupe et de leur intensité entre des données issues de réanalyses et celles issues de différentes simulations du climat futur peut apporter des réponses suffisantes aux compagnies d’assurance sur l’évolution de ce risque dans un climat dont les conditions climatiques sont différentes de celui d’aujourd’hui. Un premier article sur la méthode a été accepté dans le journal Natural Hazard and Earth Science System. La méthode a été appliquée aux données issues des modèles participant au projet CMIP5. Il s’agit d’évaluer la capacité des modèles de climat à reproduire les événements type « tempête de vent hivernales en Europe » et d’estimer l’impact du changement climatique sur la fréquence et l’intensité des tempêtes de vent hivernales en Europe. Un second article reprenant les résultats de cette étude est en préparation. La seconde partie de la thèse est focalisée sur le projet opérationnel Severe WIndstorms Forecasting Tool (SWIFT) dont le but est de développer un outil permettant, à partir de prévisions météorologiques issues toutes les six heures, de détecter un événement type tempête de vent pouvant causer des dégâts majeurs en Europe et de proposer aux entités du groupe AXA concernées une estimation du montant des pertes et du nombre de sinistres associés à l’événement à venir ainsi que leurs localisations. / The research carried out during the PhD deals with winter windstorms with high economic damage potential in Europe and can be divided in two parts. The first part aims at quantifying the impact of climate change on European winter windstorms and relies on datasets covering long periods of time (>30 years) either in the past or in the future. The objective of the second part is to forecast potential losses and claims associated with an upcoming extreme windstorm by using forecast data updated every six hours. The overall objective of the first part is to provide a medium-term view of what could be the winter windstorms in Europe during the 21st century. It thus completes the short-term vision of the risk given by the Catastrophe Models used by the (re)insurers to assess the cost of the risk on their portfolio. A new methodology has been developed to define the damage potential associated with European winter windstorms. The novelty of the methodology relies in the use of several variables capturing different spatiotemporal scales and the coupling that exists between variables during the cyclogenesis. Seeking for events sharing a similar intense signature simultaneously in the relative vorticity at 850 hPa, the mean sea level pressure and the surface wind speed lead to the detection of a small group of events. Comparing the number of events that belong to this group and their intensity in reanalysis datasets and different simulations of the future climate can provide enough information to insurance companies on the potential evolution of this hazard in a future climate. A first paper on the methodology has been accepted in the journal of Natural Hazard and Earth Science System.The methodology has been applied to the datasets provided by Global Climate Models (GCM) participating to the CMIP5 project. The goal is to assess the ability of GCMs to reproduce winter windstorms in Europe and the potential impact of climate change on the frequency and intensity of such events. A second paper presenting the results obtained from this second study will be submitted.The second part of the PhD focuses on the project Severe WIndstorms Forecasting Tool (SWIFT). The objective is to develop an early warning tool that detects an upcoming winter windstorms in meteorological forecasts updated every six hours and provides interested AXA entities with an alert on the upcoming windstorm as well as an estimate of the potential losses and claims.The tool has been developed in parallel of the research project and consists in two modules. In the first module, particularly intense systems are detected in meteorological forecasts and the associated gust footprint is extracted. In the second module, wind speeds are translated into a loss and a number of claims thanks to vulnerability curves. When a system is detected, an alert is sent with the appropriate information on the event propagation and the associated loss. The tool has been running automatically for the 2013 – 2014 winter season and detected most of the events that passed over Europe.

A research report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in Engineering. Johannesburg 2017 / The present study investigates the possibility of designing a catenary barrel vault, which can be implemented in regions where extreme tropical storms are frequently experienced. It moreover investigated the effect of non-uniform wind loads on catenary barrel vaults, and how to solve for these load conditions efficiently. The effects of high, non-uniform wind loads were assessed, and possible solutions were explored to determine a structurally efficient solution in resisting the loads applied. Different analysis and design techniques were explored in this research. These techniques included the optimization of the geometry, in resisting the applied loads most efficiently, as well as the structural design of the section in ensuring a durable and safe structure. The study revealed that the geometry of the structure cannot be optimised to resist the applied loads in a catenary fashion without external aid. By draping the vault in a post-tensioned basalt geogrid mesh, axial compression can be increased in the section and geometry optimisation can be achieved in resisting the applied loads in a catenary fashion. Three post-tensioning techniques were investigated and discussed. / MT 2018

The large-scale, mid-latitude circulation in the upper troposphere is dominated by Rossby waves. The jet stream flows along the wave structure and surface cyclones can be found ahead of the troughs of the waves, propagating eastward. This propagation is here estimated as the zonal phase speed which is quantified using spectral analysis, producing a unique, global daily value for each day of the winter season (DJF) between 1979 and 2019. From this data set phase speed events are defined as periods of more than four consecutive days of the top or bottom 5\% phase speed values, resulting in 15 low phase speed events and 22 high phase speed events. During events of low phase speed the 2m temperature is higher than the climatology at high latitudes and lower over Europe and Siberia. Zonal wind speed at 10m and 250hPa is also found to be lower than the climatology over both the Pacific and Atlantic storm track. Furthermore, low phase speed events are found to be occurring when blocking is present on either one or both storm tracks. During high phase speed events there is an overall increase in zonal wind speed both at 10m and 250hPa over both storm tracks as well as total magnitude of wind over western Europe. These findings suggest a link of high phase speed events to windstorms over Europe. A subjective classification indicates that at the onset of high phase speed events blocking is found mainly in two regions, one at high latitudes outside the Siberian coast and one at low latitudes outside the coast of Japan, suggesting enhanced temperature gradients at the entrance of the Pacific could cause these events. / Den storskaliga cirkulationen över mellanbredderna i den övre troposfären domineras av Rossbyvågor. Dessa är en vågstruktur som formas från Jordens rotation och vorticitet och associeras med det starka flödet från jetströmmen som återfinns längs vågstrukturen. På grund av vorticiteten uppstår cykloner framför vågornas tråg och hela systemet propagerar österut. Propageringen uppskattas här som fashastighet och kvantifieras med spektralanalys, en metod där interpolering från ett spektrum används snarare än teoretiska beräkningar. Detta producerar ett unikt och globalt dygnsmedel under vintersäsongen (December, Januari, Februari) mellan 1979 och 2019, där vintern väljs på grund av den stora variabiliteten i fashastighet som observeras då. Från denna data definieras fashastighetsevent som fyra eller fler dagar i sträck med de högsta eller lägsta 5 \%-värdena, vilket resulterar i 15 event med låg fasthastighet och 22 event med hög fashastighet. Under eventen med låg fashastighet är temperaturen vid 2m högre än klimatologin vid höga breddgrader och lägre över Europa och Sibirien. Den zonala vinden vid 10m och 250hPa är också lägre än klimatologin över både lågtrycksbanan över Stilla havet och Atlanten. Vidare så fann vi att låg fashastighet uppstår i samband med atmosfärisk blockering över en eller båda lågtrycksbanor. Under event med hög fashastighet observeras en ökning i zonal vindstyrka både vid 10m och 250hPa över båda lågtrycksbanorna samt en ökad styrka i den totala magnituden av vinden över västra Europa. Dessa fynd tyder på en länk mellan hög fashastighet och vindstormar i Europa. Vid starten av event med hög fashastighet återfinns atmosfärisk blockering främst i två regioner, en vid höga breddgrader utanför den Sibiriska kusten och en vid låga breddgrader utanför Japans kust, vilket tyder på att ökade temperaturgradienter vid början av lågtrycksbanan över Stilla havet kan orsaka dessa event.