Cette thèse s’inscrit dans la problématique de l’utilisation des observations satellitaires pour l’assimilation en prévision numérique du temps dans les régions nuageuses pluvieuses. Les travaux sont abordés en lien avec l’amélioration de la prévision des cyclones tropicaux et s’appuient sur la mission satellitaire innovante MEGHATROPIQUES couvrant les zones tropicales avec une répétitivité temporelle inégalée et en particulier sur le sondeur micro-ondes d’humidité SAPHIR à 183 GHz. Nous avons utilisé le modèle de prévision numérique du temps ALADIN-Réunion opérationnel à Météo-France depuis 2006 dont le domaine couvre une large partie de l’océan Indien avec une résolution horizontale de 8 km, ainsi que le modèle de transfert radiatif RTTOV-SCATT qui offre un bon compromis entre sa précision pour décrire les atmosphères diffusantes et sa rapidité d’exécution. Dans un premier temps nous avons optimisé le choix des propriétés radiatives des précipitations solides afin de simuler au mieux les températures de brillance SAPHIR avec les modèles ALADIN-Réunion et RTTOV-SCATT. Nous avons ensuite proposé une méthode d’inversion des températures de brillance SAPHIR en zones nuageuses basée sur une méthode bayésienne permettant de restituer des profils atmosphériques corrigés. Ces profils inversés ont été validés pour une situation particulière associée au cyclone Benilde (Décembre 2011). Les profils d’humidité spécifique ont alors été introduits comme de nouvelles observations dans l’assimilation variationnelle tridimensionnelle (3D-Var) du modèle ALADIN-Réunion. La capacité du système 3D-Var à contraindre le champ d’humidité analysé vers les profils inversés est démontrée, ainsi que l’amélioration des prévisions de précipitations à courte échéance. Toutefois, la prévision du cyclone Benilde est de moins bonne qualité avec ces observations additionnelles. Plusieurs pistes sont proposées pour expliquer et améliorer ces premiers résultats. Finalement, une étude a été réalisée pour préparer les évolutions des modèles de prévision numérique. Nous avons examiné la capacité d’une version d’ALADIN-Réunion avec un schéma de convection profonde pronostique à simuler le cycle de vie du cyclone Bejisa (Décembre 2013 - Janvier 2014). Des améliorations significatives sont notées à la fois sur la trajectoire et l’intensification de ce système tropical. De manière cohérente, la simulation des températures de brillance SAPHIR en zones nuageuses est en meilleur accord avec les observations. Un modèle à plus fine échelle (AROME) résolvant explicitement la convection profonde (résolution horizontale de 2.5 km) est appelé à remplacer le modèle ALADIN-Réunion. Sa capacité à décrire le système Bejisa est démontrée. Toutefois il apparaît que le choix optimal pour le type de particule décrivant les précipitations solides fait pour ALADIN-Réunion n’est pas adapté à la simulation des températures de brillance SAPHIR avec AROME et RTTOV-SCATT. Les causes de cette incohérence sont expliquées. / This thesis is focused on the use of satellite observations within cloudy and rainy areas for assimilation in numerical weather prediction models. The activities have been undertaken in the context of tropical cyclone forecasting. They have taken advantage of the recent satellite mission MEGHA-TROPIQUES covering tropical regions with an unprecedented temporal revisit with a focus on the humidity sounder SAPHIR at 183 GHz. We have used the numerical weather prediction model ALADIN-Réunion that is operational at Météo-France since 2006 and covers a large fraction of the Indian ocean with a 8 km horizontal resolution. The radiative transfer model RTTOV-SCATT has also been considered, since it provides a good compromise between its accuracy to simulate scattering atmospheres and its computational cost. In a first step, the choice of the radiative properties for solid precipitating particles has been optimized in order to improve the simulation of SAPHIR brightness temperatures with ALADIN-Réunion and RTTOV-SCATT models. Then, an inversion method of cloudy SAPHIR brightness temperatures based on the bayesian technique has been chosen in order to retrieve improved atmospheric profiles. The retrieved profiles have been validated for a case study corresponding to the tropical cyclone Benilde (December 2011). Profiles of specific humidity have been introduced as new observations in the tridimensional variational assimilation (3D-Var) system of the ALADIN-Réunion model. The capacity of the 3D-Var system to constrain the humidity analysis towards the retrieved profiles is demonstrated, together with improved short-range precipitation forecasts. On the other hand, the prediction of the tropical cyclone Benilde is degraded with these additional observations. A number of reasons are provided to explain and improve these first results. Finally, a study has been done to prepare future evolutions of numerical weather prediction models. We have examined the skill of a version of the ALADIN-Réunion model with a prognostic deep moist convection scheme to simulate the life cycle of tropical cyclone Bejisa (December 2013 - January 2014). Significant improvements have been noticed on the trajectory and on the intensification of this tropical system. Consistently, the simulation of SAPHIR brightness temperatures is in better agreement with observations. A fine scale model (AROME) describing explicitly deep moist convection is planned to replace the ALADIN-Réunion model. Its ability to describe the cyclone Bejisa is demonstrated. However, it appears that the optimal choice of the solid particle made for ALADIN-Réunion is not suited for the simulation of SAPHIR brightness temperatures with AROME and RTTOV-SCATT. Explanations are given of such inconsistency.

Concentric eyewall formation and eyewall replacement cycles are intrinsic processes that determine the intensity of a tropical cyclone, as opposed to purely environmental factors such as wind shear or the ocean heat content. Although extensive research has been done in this area, there is not a single widely accepted theory on the formation of secondary eyewall structures. Many previous studies focused on dynamic processes in the inner core of a tropical cyclone that would precede and ultimately lead to the formation of a secondary eyewall. Hurricanes Katrina and Rita in 2005 were frequently sampled by research aircraft which gathered a copious amount of data. During this time, Rita developed a secondary eyewall which eventually replaced the original eyewall. This thesis will investigate the formation of a secondary eyewall with particular emphasis on the rainband region, as observations show that an outer principal rainband transformed into the secondary ring. A high resolution, full physics model (MM5) initialized with global model forecast fields correctly predicted the secondary eyewall formation in Rita. The model output will be used to investigate both Katrina and Rita in terms of their PV generation characteristics since PV and vorticity maxima correlate well with wind maxima that accompany the eyewall and rainbands. Furthermore, dynamical processes such as vortex Rossby wave (VRW) activity in the inner core region will be analyzed. Comparison of the differences in the two storms might shed some light on dynamics that can lead to structure changes. Comparison of the model data with aircraft observation is used to validate the results. Doppler radar derived wind fields will be used to calculate the vertical vorticity. The vorticity field is closely related to PV and thus a manifestation of the PV generation process in the rainband. The investigation has shown that Rita?s principal rainband features higher PV generation rates at radii beyond 80 km. Both the azimuthal component and the projection of asymmetric PV generated by convection onto the azimuthal mean connected with the principal band are hypothesized to be of importance for the formation of the secondary eyewall. VRW were found not to be important for the initial formation of the ring but might enhance convective activity once the outer eyewall contracts.

A two-dimensional numerical model (RiverFLO-2D) has been enhanced to simulate flooding of urban areas by developing an innovative wet and dry surface algorithm, accounting for variable rainfall, and recoding the model computer program for parallel computing. The model formulation is based on the shallow water equations solved with an explicit time-stepping element-by-element finite element method. The dry-wet surface algorithm is based on a local approximation of the continuity and momentum equations for elements that are completely dry. This algorithm achieves global volume conservation in the finite element, even for flows over complex topographic surfaces. A new module was implemented to account for variable rainfall in space and time using NEXRAD precipitation estimates. The resulting computer code was parallelized using OpenMP Application Program Interface, which allows the model to run up to 5 times faster on multiple core computers. The model was verified with analytical solutions and validated with laboratory and field data. Model application to the Malpasset dam break and Sumacarcel flooding event show that the model accurately predicts flood wave travel times and water depths for these numerically demanding real cases. To illustrate the predictive capability of the enhanced model, an application was made of the city of Sweetwater flooding in Miami-Dade County, FL caused by the Hurricane Irene. The simulation starts with dry bed and rainfall is provided by NEXRAD estimates. Integrating NEXRAD rainfall estimates, developing a novel dry-wet area algorithm and parallelizing RiverFLO-2D code, this dissertation presents a proof of concept to accurately and efficiently predict floods in urban areas, identifying future improvements along this line of research.

Performance-based engineering (PBE) requires advances in hazard characterization, structural modeling, and nonlinear analysis techniques to fully and efficiently develop the fragility expressions and other tools forming the basis for risk-based design procedures. This research examined and extended the state-of-the-art in hazard characterization (wind and surge) and risk-based design procedures (seismic). State-of-the-art hurricane models (including wind field, tracking and decay models) and event-based simulation techniques were used to characterize the hurricane wind hazard along the Texas coast. A total of 10,000 years of synthetic hurricane wind speed records were generated for each zip-code in Texas and were used to statistically characterize the N-year maximum hurricane wind speed distribution for each zip-code location and develop design non-exceedance probability contours for both coastal and inland areas. Actual recorded wind and surge data, the hurricane wind field model, hurricane size parameters, and a measure of storm kinetic energy were used to develop wind-surge and wind-surge-energy models, which can be used to characterize the wind-surge hazard at a level of accuracy suitable for PBE applications. These models provide a powerful tool to quickly and inexpensively estimate surge depths at coastal locations in advance of a hurricane landfall. They also were used to create surge hazard maps that provide storm surge height non-exceedance probability contours for the Texas coast. The simulation tools, wind field models, and statistical analyses, make it possible to characterize the risk-consistent hurricane events considering both hurricane intensity and size. The proposed methodology for event-based hurricane hazard characterization, when coupled with a hurricane damage model, can also be used for regional loss estimation and other spatial impact analyses. In considering seismic hazard, a risk-consistent framework for displacement-based seismic design of engineered multistory woodframe structures was developed. Specifically, a database of probability-based scale factors which can be used in a direct displacement design (DDD) procedure for woodframe buildings was created using nonlinear time-history analyses with suitably scaled ground motions records. The resulting DDD procedure results in more risk-consistent designs and therefore advances the state-of-the-art in displacement-based seismic design of woodframe structures.

Thesis (D. Min.)--New Orleans Baptist Theological Seminary, 2008. / Abstract and vita. Includes final project proposal. Includes bibliographical references (leaves 146-152, 219-225).

The scarcity of data poses a challenging obstacle for the study of natural disasters, especially in developing countries where the social vulnerability plays as important a role as the physical vulnerability.  The work presented in this thesis is oriented towards the demonstration of the usefulness of press archives as a data source for the temporal and spatial analysis of landslides in Tegucigalpa, Honduras for the period between 1980 and 2005.  In the last four decades, Tegucigalpa has been characterized by a disorganized urban growth that has significantly contributed to the destabilization of the city’s slopes.  In the first part of the thesis, a description of the database compilation procedure is provided.  The limitations of using data derived from press archives have also been addressed to indicate how these affect the subsequent landslide analyses.  In the second part, the temporal richness offered by press archives has allowed the establishment of rainfall thresholds for landslide occurrence.  Through the use of the critical rainfall intensity method, the analysis of rainfall thresholds for 7, 15, 30 and 60 antecedent days shows that the number of yielded false alarms increases with the threshold duration.  A new method based on the rainfall frequency contour lines was proposed to improve the distinction between days with and without landslides.  This method also offers the possibility to identify the landslides that may only occur with a major contribution of anthropogenic disturbances as well as those landslides induced by high-magnitude rainfall events.  In the third part, the matrix method has been employed to construct two landslide susceptibility maps: one based on the multi-temporal press-based landslide inventory and a second one based on the landslide inventory derived from an aerial photograph interpretation carried out in 2014.  Despite the low spatial accuracy provided by the press archives in locating the landslides, both maps exhibit 69% of consistency in the susceptibility classes and a good agreement in the areas with the highest propensity to landslides.  Finally, the integration of these studies with major actions required to improve the process of landslide data collection is proposed to prepare Tegucigalpa for future landslides.

Hurricane Ivan struck the Gulf Coast in September 2004. Ivan was classified as a category five storm on the Saffir-Simpson scale of Hurricane Intensity before it made landfall in the U.S. with winds around 165 miles per hour. Its intensity dropped to a category three as it approached the Gulf Coast. Ivan damaged not only properties and businesses along the coast but inland as well. Heavy rains caused rivers and lakes to overflow their banks and tornadoes spawned by the storm struck Tennessee, Kentucky, Louisiana, and Georgia.The purpose of this research is to examine if hurricane insurance or separate endorsements adequately protects and reimburses owners for their losses and to access public and private responses to natural hazards and disaster mitigation using Gulf Shores, Alabama as a case study. Since fall 2004, many homeowners and business owners have been negotiating with their insurance companies. Owners received some help from the organizations like FEMA and the American Red Cross but these efforts were not enough to recuperate all the damages and losses. This study seeks to place the issues of insurance costs, claims and coverage in Gulf Shores, Alabama within the overall context of natural hazards research using archival sources, observation, questionnaires, and formal and informal interviews as data sources. In light of continuing migration to hurricane prone coastal areas, ever-increasing property values and insurance premiums, and the added risk of increasing hurricane frequency, this research contributes to a better understanding of the role of insurance on natural hazard mitigation and preparedness. / Department of Geography

Conserving the earth's precious water supply is of increasing importance in light of the growing population and climate dynamics; therefore, this study focuses on identifying those exotic species that are best suited for the changing climate and environment of the Lower Kanawha Valley Region in West Virginia without compromising the water sustainable qualities once exhibited by the indigenous species. This task was accomplished by reviewing, analyzing, and evaluating the plant hydraulics and habitat matching characteristics associated with the identified native and exotic species. These species were limited to those produced or found in the local nurseries and garden centers in the designated region, thereby providing a practical and water sustainable plant list for the local homeowners and design professionals. The final list of species was translated into a master planting design of an arboretum displaying and demonstrating water conservation on the grounds of the Hurricane Valley Park. / Department of Landscape Architecture

The dynamic behaviour of high-rise buildings has become a critical design consideration as buildings are built taller and more slender. Large wind vibrations cause an increase in the lateral wind loads, but more importantly, they can be perceived by building occupants creating levels of discomfort ranging from minor annoyance to severe motion sickness. The current techniques to address these issues include stiffening the lateral load resisting system, reducing the number of stories, or incorporating a vibration absorber at the top of the building. All of which have consequences on the overall project cost. The dynamic response of high-rise buildings is highly dependent on damping. Full-scale measurements of high-rise buildings have shown that the inherent damping decreases with height and recent in-situ measurements have shown that the majority of buildings over 250 meters have levels of damping less than 1% of critical. Studies have shown that small increases in the inherent damping can lead to vast improvement in dynamic response. A new damping system, the viscoelastic (VE) Fork Configuration Damper (FCD), has been developed at the University of Toronto to address these design challenges. The proposed FCDs are introduced in lieu of coupling beams in reinforced concrete (RC) coupled wall buildings and take advantage of the large shear deformations at these locations when the building is subjected to lateral loads. An experimental study was conducted on 5 small-scale VE dampers to characterize the VE material behaviour and 6 full-scale FCD samples in an RC coupled wall configuration (one designed for areas where low to moderate ductility is required and one with built-in ductile structural “fuse” for areas where high ductility is required). The VE material tests exhibited stable hysteretic behaviour under expected high-rise loading conditions and the full-scale tests validated the overall system performance based on the kinematic behaviour of coupled walls, wall anchorage and VE material behaviour. Analytical models were developed that capture the VE material behaviour and the FCD system performance well. An 85-storey high-rise building was studied analytically to validate the design approach and to highlight the improvements in building response resulting from the addition of FCDs.

The dynamic behaviour of high-rise buildings has become a critical design consideration as buildings are built taller and more slender. Large wind vibrations cause an increase in the lateral wind loads, but more importantly, they can be perceived by building occupants creating levels of discomfort ranging from minor annoyance to severe motion sickness. The current techniques to address these issues include stiffening the lateral load resisting system, reducing the number of stories, or incorporating a vibration absorber at the top of the building. All of which have consequences on the overall project cost. The dynamic response of high-rise buildings is highly dependent on damping. Full-scale measurements of high-rise buildings have shown that the inherent damping decreases with height and recent in-situ measurements have shown that the majority of buildings over 250 meters have levels of damping less than 1% of critical. Studies have shown that small increases in the inherent damping can lead to vast improvement in dynamic response. A new damping system, the viscoelastic (VE) Fork Configuration Damper (FCD), has been developed at the University of Toronto to address these design challenges. The proposed FCDs are introduced in lieu of coupling beams in reinforced concrete (RC) coupled wall buildings and take advantage of the large shear deformations at these locations when the building is subjected to lateral loads. An experimental study was conducted on 5 small-scale VE dampers to characterize the VE material behaviour and 6 full-scale FCD samples in an RC coupled wall configuration (one designed for areas where low to moderate ductility is required and one with built-in ductile structural “fuse” for areas where high ductility is required). The VE material tests exhibited stable hysteretic behaviour under expected high-rise loading conditions and the full-scale tests validated the overall system performance based on the kinematic behaviour of coupled walls, wall anchorage and VE material behaviour. Analytical models were developed that capture the VE material behaviour and the FCD system performance well. An 85-storey high-rise building was studied analytically to validate the design approach and to highlight the improvements in building response resulting from the addition of FCDs.