Dissertations / Theses on the topic 'Storms'

This thesis seeks to provide a new perspective on storms in Shakespeare. Rather than a recurrent motif, the storm is seen as protean: each play uses the storm in a singular way. The works of Shakespeare's contemporaries are explored for comparison, whilst meteorological texts and accounts of actual storms are examined for context. Using close reading and theories of ecocriticism throughout, I show that Shakespeare's storms are attentive to the environmental conditions of experience. Although the dominant practice of staging storms in early modern England is to suggest the supernatural, Shakespeare writes storms which operate quite differently. I argue that this is a compelling opportunity to see Shakespeare develop a complex engagement with audience expectations. Five plays are explored in separate chapters, each with respect to performative conditions and through close reading of the poetry. Firstly, I argue that the Globe's opening in 1599 demanded a spectacular showcase, to which Julius Caesar responded, shaping the play's language and staging. With King Lear (c.1605), the traditional, non-Shakespearean location of the heath betrays a tendency to misread the play in terms of location rather than event. King Lear's storm withholds the supernatural, a manifestly different approach from that in Macbeth (c.1606); Shakespeare both adheres to and resists convention in this respect. The relationship between storm and the supernatural in Macbeth is shown to be fundamental to the play's equivocation. Shakespeare's next storm is in Pericles (c.1608), which also contains a storm by George Wilkins. The two writers' approaches are explored with respect to the Bible, alluded to extensively throughout the play. Finally, with The Tempest (c.1611), I argue that Shakespeare's manipulation of audience expectation through the storm demands a reading which combines the metatheatrical and the ecocritical. Foregrounded as expressions of dramatic and environmental awareness, I bring new insights to Shakespeare's storms.

DICTIONARY OF STORMS is a collection of poetry that explores the dynamics of one family through their son’s absence. Using recurring images of skin, water, dragonflies, and pearls, the poems examine distance and absence, wanderlust and filial obligation from different family members’ perspectives. Desires are sloughed off, replaced by new ones, re-cultivated as mythos. The architecture of many individual poems, and the collection as a whole, are structured by meditative lyricism reminiscent of Li-Young Lee. Robert Hass’s poems and translations serve as a model for articulating both the difficulty and beauty of longing. Personae such as “Admonishing Brother Returns as Chrysanthemum” and “Hungry Brother Returns as Octopus” are influenced by Ai and Louise Glück. In the spirit of Emily Dickinson and John Keats, DICTIONARY OF STORMS reflects upon longing, grief, and desire.

Dust storms have a great many environmental implications in the world's dry lands where they are particularly common. Four main classes of dust event are identified and defined: dust storms, dust haze, blowing dust and dust devils. The geography of dust storms is analysed in each of eight major world regions: Africa, the Middle East, South-west Asia, Europe and the USSR, China, Australia, North America and Latin America. Terrestrially observed meteorological data and data from remote sensing platforms are employed to identify the major source areas in each region, their seasonality, diurnal patterns of activity and trajectories of long-range transport. Among the important controls on the frequency distribution of dust storm activity are the meteorological conditions that generate dust-raising winds, and a number of meteorological systems commonly cause dust storms in all global regions. These include low pressure fronts with intense baroclinal gradients, pressure gradient winds between moving or stationary air masses, katabatic winds and convectional cells. The nature of the surface upon which deflation occurs is also important; typical dust-producing geomorpholological units include alluvial spreads, lacustrine deposits, desert depressions, loess deposits and reactivated fossil dunes. Dust storm activity is prone to considerable variation. The seasonal characteristics are explicable with reference to the meteorological systems generating dust, the state of ground cover, particularly vegetation, and the effects of seasonal rainfall. Substantial variations also occur from year to year, and land use and climatic variations can substantially affect their occurrence.

Geomagnetic storms are well observed phenomena that enhance the plasma of the inner magnetosphere to high energies. They are defined by the characteristic trace in indices that measure the variation of the north-south component of the Earth’s magnetic field, such as the Dst or SYM-H. These indices are not purely measures of the symmetric ring current but include components of other current systems within the magnetosphere, primarily the tail and magnetopause currents. Using the methodology of Asikainen et al. [2010] the SMR index has been deconstructed to observe the evolution of the aforementioned current systems over the storm durations. Reeves et al. [2003] showed that only half of all storms caused an increase in the relativistic electron flux at geosynchronous orbit. For the remaining half the electron flux either does not change or decreases. It has been shown that the ring current decays faster for flux decrease storms than flux increase storms. Using a superposed epoch analysis, of geomagnetic indices and solar wind parameters, it has also been shown that although flux increase storms tend to have faster, less dense solar wind in the recovery phase of storms, it appears that it is the orientation of the IMF, which remains more southward in the recovery phase, that is the key parameter. This allows for the continued injection of plasma sheet particles into the inner magnetosphere. Further evidence to support this has been shown with the hydrogen and helium fluxes mirroring that of the electron flux. Finally, potential wave modes were evaluated over storm durations and potential acceleration mechanisms were noted as being more intense during flux increase storms than flux decrease storms; this is most likely due to the increase in the seed particles necessary for their generation.

Geomagnetic storms deposit energy and momentum into the Earth’s magnetosphere which in turn energizes the terrestrial atmosphere through Joule heating and particle precipitation. This storm energy predominantly converges at altitudes of 100 to 150 km, corresponding to the lower thermospheric region, which is then globally redistributed throughout the thermosphere. It is essential that we understand the times and magnitudes of this energy to understand the terrestrial atmospheric response to geomagnetic storms. However, our current knowledge is mostly limited to the studies of orbital altitudes of the thermosphere. We aim to fill this gap by conducting a statistical study of lower thermospheric response to geomagnetic storms. We use neutral temperature data from SABER (Sounding of the Atmosphere Using Broadband Emission Radiometry) instrument onboard the TIMED (Thermosphere, Ionosphere, and Mesosphere Energy Dynamics) satellite for this study. We devise a procedure to extract the storm response from SABER temperature measurements and deduce the magnitudes and times of the global storm energy redistribution in the 100 to 120 km altitude of the thermosphere. We use methods of inferential and descriptive statistics to investigate the lower thermospheric response for 145 storm intervals that occurred between 2002 and 2010. We also investigate the performance of the state-ofart physics and empirical models in replicating the lower thermosphere during geomagnetic storms.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 107-108).
Server virtualization enables data centers to run many VMs on individual hosts - this reduces costs, simplifies administration and facilitates management. Improvement in hardware and virtualization technology, coupled with the use of virtualization for desktop machines with modest steady-state resource utilization, is expected to allow individual hosts to run thousands of VMs at the same time. Such high VM densities per host would allow data centers to reap unprecedented cost-savings in the future. Unfortunately, unusually high CPU and memory pressure generated when many VMs boot up concurrently can cripple hosts that can otherwise run many VMs. Over provisioning hardware to avoid prohibitively high boot latencies that result from these - often daily - boot storms is clearly expensive. The aim of this thesis is to investigate whether a hypervisor could theoretically exploit the overlap in the instruction streams of concurrently booting VMs to reduce CPU pressure in boot storms. This idea, which we name silhouette execution, would allow hypervisors to use the CPU in a scalable way, much like transparent page sharing allows a hypervisor to use its limited memory in a scalable fashion. To evaluate silhouette execution, we studied user-space instruction streams from a few Linux services using dynamic instrumentation. We statistically profiled the extent of nondeterminism in program execution, and compiled the reasons behind any execution differences. Though there is significant overlap in the user-mode instruction streams of Linux services, our simple simulations show that silhouette execution would increase CPU pressure by 13% for 100 VMs and 6% for 1000 VMs. To remedy this, we present a few strategies for reducing synthetic differences in execution in user-space programs. Our simulations show that silhouette execution can reduce CPU pressure on a host by a factor of 8x for 100 VMs and a factor of 19x for 1000 VMs once these strategies are used. We believe that the insights provided in this thesis on controlling execution differences in concurrently booting VMs via dynamic instrumentation are a prelude to a successful future implementation of silhouette execution.
by Syed Aunn Hasan Raza.
M.Eng.

The coronal mass ejections (CMEs) and solar flares associated with extreme solar activity may strike the Earth's magnetosphere and give rise to geomagnetic storms. During geomagnetic storms, the polar plasma dynamics may influence the middle and low-latitude ionosphere via travelling ionospheric disturbances (TIDs). These are wave-like electron density disturbances caused by atmospheric gravity waves propagating in the ionosphere. TIDs focus and defocus SuperDARN signals producing a characteristic pattern of ground backscattered power (Samson et al., 1989). Geomagnetic storms may cause a decrease of total electron content (TEC), i.e. a negative storm effect, or/and an increase of TEC, i.e. a positive storm effect. The aim of this project was to investigate the ionospheric response to strong storms (Dst < -100 nT) between 2011 and 2015, using TEC and scintillation measurements derived from GPS receivers as well as SuperDARN power, Doppler velocity and convection maps. In this study the ionosphere's response to geomagnetic storms is determined by the magnitude and time of occurrence of the geomagnetic storm. The ionospheric TEC results of this study show that most of the storm effects observed were a combination of both negative and positive per storm per station (77.8%), and only 8.9% and 13.3% of effects on TEC were negative and positive respectively. The highest number of storm effects occurred in autumn (36.4%), while 31.6%, 28.4% and 3.6% occurred in winter, spring and summer respectively. During the storms studied, 71.4% had phase scintillation in the range of 0.7 - 1 radians, and only 14.3% of the storms had amplitude scintillations near 0.4. The storms studied at SANAE station generated TIDs with periods of less than an hour and amplitudes in the range 0.2 - 5 TECU. These TIDs were found to originate from the high-velocity plasma flows, some of which are visible in SuperDARN convection maps. Early studies concluded that likely sources of these disturbances correspond to ionospheric current surges (Bristow et al., 1994) in the dayside auroral zone (Huang et al., 1998).

Este trabajo presenta un marco metodológico para la estimación de la vulnerabilidad costera al impacto de tormentas a dos escalas, regional y local. Se hace una evaluación de la vulnerabilidad costera física mediante la cuantificación de dos componentes: erosión e inundación. Posteriormente, ambos elementos son integrados en un Índice de Vulnerabilidad Costera. La metodología desarrollada cubre los siguientes pasos: (i) clasificación de tormentas, (ii) evaluación de la respuesta inducida en la playa -inundación y erosión- (iii) caracterización de las playas en la zona de estudio (iv) definición del índice de vulnerabilidad costera y (v) evaluación de la vulnerabilidad costera. Estos pasos han sido derivados y aplicados a la costa catalana (Mediterráneo Noroccidental español) y pueden ser adaptados a otras costas. Los resultados obtenidos pueden ser fácilmente utilizados por los gestores costeros para identificar zonas costeras sensibles a una clase de tormenta dada y sus procesos inducidos (inundación, erosión o la combinación de ambos) para decidir donde tomar acciones para mitigar estos impactos.
This work presents a methodological framework for the estimation of coastal vulnerability to storm impacts at two scales, regional and local. It estimates the physical coastal vulnerability through the quantification of two components: erosion and flooding. Afterwards the two elements are integrated into the so called Coastal Vulnerability Index. The methodological process covers the following steps: (i) storm classification, (ii) evaluation of the induced beach response -flood and erosion-, (iii) coastal zone characterization, (iv) definition of a coastal vulnerability index to storms and (v) assessment of the coastal vulnerability. These steps have been derived and applied to the Catalan coast (NW Spanish Mediterranean) and can be adapted to other coasts. The obtained results can be used by coastal managers in an easy manner to identify sensitive coastal stretches for a given storm class and the induced processes (flooding, erosion or combination of both) with the purpose to take actions and mitigate these impacts.

Wave-storms are the responsible of the main changes in the Coast. Their detailed characterization results in a better design of any marine structure. The most common approach to describe wave-storms is to simplify the event by taking the significant wave-height (Hp), peak period (Tp) and direction (0p) at the peak of the storm and treating these variables independently. However, it is well accepted that some relationship should exist between them. What is more, the development of sophisticated numerical models in Coastal Engineering are demanding additional variables such as the duration of the wave-storm (D), the amount of associated energy (E), temporary evolution of the variables and their relationship to atmospheric climate-indices, to better reproduce the simulated processes. The main objectives and results of this thesis are as follows. First, wave-storms in the present wave climate of the Catalan Coast are characterized, assuming stationarity. The wave-storm variables modelled are: the energy at the peak of the wave-storm (Eu ), Tp , E, D, 0p and the proportions of time from the start to the storm peak and from the storm peak to the end (growth-decay rates). E, Eu , Tp and D are fit by generalized Pareto distributions (GPD). Their joint probability structure is characterized by a hierarchical Archimedean copula (HAC). 0p is characterized through a mixture of von Mises-Fisher probability distribution functions and related to E, T p and D through a multinomial logistic model. The growth-decay rates are related to D through third degree polynomials. A triangle and an irregular-trapezoid are proposed to model the wave-storm shape. In the present climate of the Catalan Coast, the constructed statistical model can serve to generate synthetic wave-storms. The most predominant 0p are north and east. The most appropriate geometric figure to describe the evolution of the wave-height is a irregular-trapezoid. For D over 100h, the peak of the wave-storm is generally closer to the end of the wave-storm than to the start. After establishing a stationary model, non-stationarity is incorporated into the characterization of wave-storms in the Catalan Coast. E, Hp , T p and D are characterized through non-stationary GPDs. The wave-storm threshold, the wave-storminess and the parameters of the GPDs are related to North Atlantic Oscillation (NAO), East Atlantic pattern (EA) and Scandinavian pattern (SC) and their first two time-derivatives, through Vectorial generalized additive models. The joint probability structure is characterized by a pseudo-time-dependent HAC. A severe greenhouse gas emission scenario is considered. The mean values of all wave-storm variables decrease in the 21st century, except for D in the northern part of the coast. A negative NAO may cause an increase in wave-storminess; the wave-storm threshold and the GPD parameters are most influenced by the dynamics of the climate-patterns, rather than by the climate-patterns themselves. The non-stationary methodology is repeated in the northwestern Black Sea, considering both a mild and a severe emission scenarios. Here, wave-storminess is not affected by the proposed climate-patterns, whereas the wave-storm threshold is strongly influenced by SC and EA. The average value of the wave-storm variables seem to have a more positive trend than in the Catalan Coast, and it is observed that an increase in mean values is related to an increase in variance. SC and EA also strongly influence the parameters of the GPDs. In the two study areas, the dependence between E and D is high, while the general dependence among the wave-storm variables is medium. In the Catalan Coast, it is expected that the dependence between E and D should increase with time. In the northwestern Black Sea, it is the dependence among all the wave-storm variables that increases with time, in both emission scenarios; the severe emission scenario presents less dependence among wave-storm variables.
El enfoque más común para describir los temporales de mar es simplificar este suceso tomando la altura de ola significante (Hp), el periodo pico (Tp) y la dirección (0p) en el pico de la tormenta y tratándolas de forma independiente. Sin embargo, está ampliamente aceptado que exista al menos alguna relación entre ellas. Es más, el desarrollo de sofisticados modelos numéricos en la ingeniería de costas pide variables adicionales como la duración de tormenta (D), la cantidad de energía asociada (E), la evolución temporal de las variables y su relación con índices climáticos atmosféricos, todo para una mejor reproducción de los procesos simulados. Los objetivos y resultados principales de esta tesis son los siguientes: Primero, se caracteriza tormentas de mar en el clima de oleaje presente, de la costa catalana, suponiendo estacionalidad. Las variables modeladas son: la energía unitaria en el pico del temporal (Eu), Tp, E, D, 0p y la proporción de tiempo desde el inicio hasta el pico y desde el pico al final del temporal (ratios de crecimiento-decrecimiento). Se caracteriza E, E u, T p y D con distribuciones generalizadas de Pareto (GPD), y se caracteriza la estructura de probabilidades conjunta de estas variables vía una cópula jerárquica arquimedeana (HAC). Se caracteriza 0p con una combinación de distribución de probabilidad de von Mises-Fisher y se le relaciona con E, T p y D a través de un modelo logístico multinomial. Se propone una forma triangular o trapezoide-irregular para modelar la forma del temporal. En el clima presente de la costa catalana, el modelo estadístico construido puede generar temporales sintéticos. Las 0p principales son el norte y el este. La figura geométrica que mejor describe la evolución de la altura de ola es un trapezoide irregular. Para D mayor que 100h, el pico del temporal está generalmente más cerca del final que del principio. La media de cada variable decrece en el siglo XXI, excepto la de D, en el norte de la costa. Una NAO negativa puede causar una subida de la tormentosidad. Además, el umbral de tormenta y los parámetros de GPD están influenciados principalmente por la dinámica de los patrones climáticos, en vez de serlo por los propios patrones climáticos. Después de establecer un modelo estacionario, se incorpora la no estacionalidad a la caracterización de temporales de mar en la costa catalana. Se caracteriza E, Hp, Tp y D con GPDs no estacionarios. El umbral de temporal, la tormentosidad y los parámetros de los GPDs están relacionados con la Oscilación de Atlántico norte (NAO), el Patrón de Atántico oriental (EA) y el Patrón escandinavo (SC) y sus primeras dos derivadas temporales, a través de Modelos aditivos generalizados vectoriales. Se caracteriza la estructura de probabilidades conjunta con un HAC pseudo-dependiente del tiempo. Se considera un escenario grave de cambio climático. Se repite la metodología no estacionaria en el noroeste del Mar Negro, considerando tanto un escenario suave de cambio climático como otro grave. En el noroeste del Mar Negro, la tormentosidad de mar no está afectada por los patrones climáticos propuestos, todo y que el umbral de temporal está fuertemente influenciado por SC y EA. Los valores medios de las variables de temporal parecen tener una tendencia más positiva que en la costa catalana, y se observa que una subida de los valores medios se relaciona con otra subida de las varianzas. SC y EA afectan fuertemente a los parámetros de los GPDs. En las dos zonas de estudio, la dependencia entre E y D es alta, mientras que la dependencia general entre las variables de temporal es media. En la costa catalana, se espera que la dependencia entre E y D crezca con el tiempo. En el noroeste del Mar Negro, es la dependencia entre todas las variables de temporal la que crece con el tiempo, en ambos escenarios de cambio climático: el escenario grave presenta menos dependencia entre las variables.

A study of the most extreme cyclones affecting the North Atlantic and Europe is presented with particular focus on extreme windstorms over the densely populated area of Western Europe, whose associated high surface wind speeds are capable of causing extensive structural damage and occasionally a loss of life. A novel cyclone identification and tracking algorithm is presented which explicitly recognises ‘multi-centre cyclones’ (MCCs), defined as cyclonic systems which contain two or three sea-level pressure minima. The method also recognises cyclone merging and splitting events and reduces the number of tracks which would have been spuriously split at some point in their life-cycle. MCC frequency is shown to increase with storm intensity, with approximately 60% of the top 30% of cyclones constituting MCCs at some point in their life-cycle. The first findings of the IMILAST (Inter-comparison of MId-LAtitudeSTorm diagnostics) project, an intercomparison study of 15 cyclone identification and tracking algorithms, are presented. Each method was applied to a 20 year period of the ERA-Interim dataset and results for cyclone frequency, intensity, life-cycle and track location were compared across the methods. The relationship between the evolution of the most intense wind storms affecting Western Europe (Britain and Ireland, Scandinavia, and Western Continental Europe) and the large-scale atmospheric flow is investigated using an automated cyclone tracking algorithm and an objective measure of cyclone destructiveness applied to ERA40 and ERA-Interim reanalysis data as well as EC-Earth model output data at two different spatial resolutions. Composite analyses reveal a clear connection between the precise location of upper-level anti-cyclonic wave breaking and cold air intrusion from the north and the position and orientation of an intense jet; this, in turn, plays a crucial role in determining into which region a developing extreme storm will be steered.

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Epub ahead of print. Paper 4: Manuscript.

 

Impacts of Geomagnetic storms on Trans-Canadian GridsInduced "dc" currents due to geomagnetic storms have caused power system blackouts and transformer damages in the past. Statistically, large geomagnetic storms follow a 10-11 year sunspot cycle, but geomagnetic disturbances with significant impacts can occur at any time. The geomagnetically induced currents (GIC) have wide range of detrimental effects on otherwise normal operation of power systems, communication systems, railway systems, and can cause oil and gas pipeline corrosion. This thesis presents a method of estimating the magnitudes of terrestrial voltages; which is based on solving the magnetic diffusion equation. The method predicts the oft-quoted figure of "1 volt per kilometer" for the range of geomagnetic field variations (magnitudes and frequencies) and ground resistivity frequently encountered. The prediction formula has been validated by the plane wave method. Geomagnetic storms have the tendency to disrupt the normal operation and even lead to major power outages depending upon the intensity of geomagnetic activity; whereas the major effects include transformer equipment damage, relay tripping, SVC failures resulting in minor or major power outages.
RÉSUMÉImpacts of Geomagnetic storms on Trans-Canadian GridsPar le passé, les courants induits produits par des orages électromagnétiques ont causés des dommages à des transformateurs ainsi que des pannes de courant majeures (blackouts). Statistiquement, les orages géomagnétiques sévères suivent un cycle d'activité solaire de 10 à 11 ans. Cependant, des perturbations géomagnétiques peuvent avoir un impact important et peuvent apparaître à n'importe quel moment. Les courants induits géomagnétiques ont un large champ d'effets néfastes sur les réseaux électriques, les systèmes de communication, les systèmes ferroviaires et peuvent causer de la corrosion dans les oléoducs. Cette thèse présente une méthode pour estimer l'amplitude des tensions terrestres qui est basée sur les équations de diffusion magnétique. Cette méthode prédit la figure couramment utilisée de « 1 volt par kilomètre » pour une étendue de champs géomagnétiques (amplitudes et fréquences) et de résistances du sol fréquemment rencontrées. La formule de prédiction a été validée par la méthode d'onde plane.Les orages géomagnétiques ont tendance à déranger les opérations normales et même à engendrer des pannes électriques majeures dépendamment de l'intensité de l'activité géomagnétique. Les principaux effets sont des dommages à l'équipement des transformateurs, des déclenchements de relais de protection, des défaillances des compensateurs statiques (SVC), ce qui causent parfois des pannes de courant mineures ou majeures.

The predictability of individual convective storms over the mid-latitude ocean is investigated by quantifying the divergence of pairs of perturbed forecasts in a cloud-resolving model. The Met Office non-hydrostatic Unified Model is used in an idealised configuration to simulate moist convection initiating under homogeneous destabilisation. All convection is represented explicitly since a convective parameterisation scheme is not used. The growth of potential temperature perturbations at a single height is quantified as a function of time and spatial scale. The perturbations are found to grow in two distinct stages. Firstly, changes in the regime diagnosed by the boundary layer parameterisation scheme lead to rapid but limited perturbation growth before growth by convective instability becomes dominant. Both error growth mechanisms are found to contribute independently to the total error growth in the forecast. The range of predictability in this perfect model framework is quantified for different spatial scales and initial condition error. The upper limit (provided by O.OO2K perturbations) is shown to be around 200 minutes at scales of 10km. Initial condition perturbations of similar magnitude to those of typical analysis errors (i.e. of order I K) were found to saturate almost immediately at all scales. The short time taken for the forecasts to become uncorrelated in all cases indicates that individual showers will always be unpredictable beyond approximately four hours. The asymmetry in the evolution of initially equal and opposite perturbations highlights the nonlinear nature of the growth, which could prove problematic for convective scale data assimilation and the design of 'optimal' perturbations for convective scale ensemble forecasting.

The Earth ionosphere becomes highly variable during extreme space-weather events. Observations from the Global Positioning System (GPS) in conjunction with tomographic imaging have the potential to characterise its disturbed behaviour. In this project, a four-dimensional tomographic technique is employed to reveal the temporal evolution and spatial distribution of ionisation in the ionosphere on a large scale (over Europe and the USA). The effects of geomagnetic storms on the dynamics of the plasma are investigated throughout the recent solar maximum, when the intensity of geornagnetic storms is greatest. The results presented in this thesis show, for the first time, a wide area view of the ionosphere during storm-time. Electron-density images of the disturbed mid/high latitude ionosphere and Total Electron Content (TEC) maps are produced over North America and Europe for several severe storms. Using both ground-based and Low Earth Orbit satellite-based GPS data as well as available ionosonde data during storm periods, improvements in imaging of ionospheric structures at storm time are made. A case-study for the 29th - 30th October 2003 storm shows the detailed evolution of ionisation in space and in time throughout the entire period of a complex storm. The peak heights of the disturbed F region were redistributed (uplifted) both over Europe and the USA around dusk for several major storm events. This uplift propagated westwards. Investigations into common features of storms indicated that positive or negative storm effects correlated with local time. In addition, the strongest enhancement in TEC and the highest uplift were in the USA sector. The project achievements are twofold. Firstly, abnormal behaviour of the disturbed ionosphere,such as enhancements in electron density and TEC and sudden uplifts of the peak height, is shown using a new GPS imaging technique. Secondly, the results will provide important experimental inputs into physical models of ionospheric storms and also contribute to the further understanding the dynamics of ionisation and underlying mechanisms of severe storms on a global scale.

There are numerous security challenges in cellular mobile networks, many of which originate from the Internet world. One of these challenges is to answer the problem with increasing rate of signalling messages produced by smart devices. In particular, many services in the Internet are provided through mobile applications in an unobstructed manner, such that users get an always connected feeling. These services, which usually come from instant messaging, advertising and social networking areas, impose significant signalling loads on mobile networks by frequent exchange of control data in the background. Such services and applications could be built intentionally or unintentionally, and result in denial of service attacks known as signalling attacks or storms. Negative consequences, among others, include degradations of mobile network’s services, partial or complete net- work failures, increased battery consumption for infected mobile terminals. This thesis examines the influence of signalling storms on different mobile technologies, and proposes defensive mechanisms. More specifically, using stochastic modelling techniques, this thesis first presents a model of the vulnerability in a single 3G UMTS mobile terminal, and studies the influence of the system’s internal parameters on stability under a signalling storm. Further on, it presents a queueing network model of the radio access part of 3G UMTS and examines the effect of the radio resource control (RRC) inactivity timers. In presence of an attack, the proposed dynamic setting of the timers manage to lower the signalling load in the network and to increase the threshold above which a network failure could happen. Further on, the network model is upgraded into a more generic and detailed model, represent different generations of mobile technologies. It is than used to compare technologies with dedicated and shared organisation of resource allocation, referred to as traditional and contemporary networks, using performance metrics such as: signalling and communication delay, blocking probability, signalling load on the network’s nodes, bandwidth holding time, etc. Finally, based on the carried analysis, two mechanisms are proposed for detection of storms in real time, based on counting of same-type bandwidth allocations, and usage of allocated bandwidth. The mechanisms are evaluated using discrete event simulation in 3G UMTS, and experiments are done combining the detectors with a simple attack mitigation approach.

Overwash, shoreface retreat, and barrier migration are common processes occurring in transgressive barrier island systems, the scale of which is exacerbated by sea level rise, subsidence and the frequency and magnitude of tropical and extratropical storms. Barrier morphology also clearly plays a key role in determining a morphological response to these processes. Using a hydrodynamic and sediment transport model (MIKE21) and selected barrier island and shoreface templates, informed by deltaic and coastal plain systems in the northern Gulf of Mexico, I performed simulations to determine barrier morphology in response to storms. A low dune with a gentle shoreface slope, characteristic of Louisiana deltaic barriers, demonstrates the greatest amount of shoreline erosion, dune overwash and barrier migration in response to a storm. Profile evolutions over time demonstrate the wider dune templates respond mostly via dune aggradation and barrier rollover whereas the narrow or low templates respond via dune overwash and barrier translation. Determining which barrier templates retain the most sediment over time becomes extremely important when planning coastal restoration projects here in Louisiana.

Quantitative projections are routinely made for the future statistics of climate variables, such as the frequency and intensity of storms in the North Atlantic. The quantification of uncertainty in these projections is particularly important if such results are to be used for decision making. This thesis addresses the design, use, and interpretation of models in climate science, using the behaviour of North Atlantic extratropical storms as a detailed case study. Results from novel statistical models and state-of-the-art dynamical models are generated and evaluated, looking at the frequency and intensity characteristics of storms in the eastern North Atlantic and the clustering characteristics of the most intense storms. It is found that statistical models are extremely limited by the shortness of the calibration data set of historical observations, and therefore have little merit other than simplicity. Dynamical models are primarily constrained by the accuracy of their dynamical assumptions, which cannot be easily quantified. Some relevant properties of dynamical systems, including structural instability, are discussed with reference to predictability in the North Atlantic and other aspects of climate science. This thesis concludes that despite the existence of "statistically significant" results from some individual models, there is little evidence that we can correctly evaluate even the sign of 21st century change of North Atlantic storm characteristics (frequency, intensity or spatial position). Although climate models do suggest that the magnitude of overall change will be small, this could still result in very large percentage changes to the tails of the distribution, given the nonlinear nature of the climate system. In order to make more confident conclusions about the tails of such distributions, much longer runs are needed than the 30 year slices requested by the CMIP experiments. In addition, formal quantification of subjective opinions about model error would benefit climate science, scientists, and decision-makers.

The purpose of this study was to identify how knowledgeable the students of Mississippi are of severe weather. The state of Mississippi is ranked second in the nation with the total number of deaths per state per year. The state also ranks among the top 10 of all states with number of tornadoes per state and cost of damage per state. Considering the facts mentioned above, a study was designed to discover if the students were taught severe weather awareness while they progressed through their twelve years of elementary and secondary schooling. A survey was created through the research of the Mississippi Department of Education, and Jim Belles, National Weather Service Memphis Office Warning Coordination Meteorologist. The results of the survey were then put to statistical tests to find out the significance of the survey questions.

The current design storm estimation method used in Canada is based on single site frequency analysis and single site intensity-duration-frequency relationships and involves large uncertainties, especially at short-term record stations and ungauged sites. To overcome the shortcoming of the current approach, a new improved method based on regional frequency analysis and regional depth-duration-frequency equations is proposed. The L-moments are used in the three stages of regional frequency analysis, namely the delineation of homogenous regions, the identification of a regional parent distribution, and the estimation of distribution's parameters. Following a numerical analysis of short duration (5 minutes to 24 hours) rainfall extremes from 375 stations, it was found that Canada may be considered as one homogeneous region where L-skewness and L-kurtosis display no significant spatial variability. Also, based on mean annual precipitation (map), Canada may be subdivided into climatologically homogeneous sub-regions, wherein the L-coefficient of variation in virtually constant. The regional parent distribution was identified as the general extreme value (GEV), the parameters of which depend on the map and storm duration. These findings are different from the present method, where the extreme value type I (EVI) is used irrespective of storm duration. A hierarchical regional approach is proposed for fitting the identified GEV distribution, where the L-skewness, L-coefficient of variation, and mean are estimated on a regional, sub-regional, and at-site basis, respectively. Monte Carlo simulation studies indicate that the hierarchical regional GEV frequency approach is substantially more accurate than the single site frequency method. In particular, it is shown that three times as much data are required for the single site method to provide the same accuracy as the hierarchical regional approach. The depth-duration and depth-frequency ratios computed by the developed hierarchical regional GEV approach are used to assess the hypothesis that convective cells associated with short duration storms (i.e. less than 120 minutes) have common properties in different hydrologic regions. Depth-duration ratios (defined as the ratios of the t-min to the 60-min rainfall depth of the same return period) are found to be independent of return period and geographical location for any storm less than 60 minutes. However, for storms of longer durations, depth-duration ratios depend on both the return period and the geographical location indexed by the at-site map. Depth-frequency ratios (defined as the ratios of the T-yr to the 10-yr rainfall depths of the same storm duration) are also found to depend on the return period and geographical location. Hence, the assumption of geographically independent depth-frequency ratios used in previous studies is incorrect. Generalized expressions of depth-duration and depth-frequency ratios are combined to develop a set of regional depth-duration-frequency equations that are applicable in Canada. These equations are found to be more accurate than other regional equations developed in previous studies. Furthermore, a split sampling experiment has verified that the proposed equations reproduce the rainfall frequency data at long-term record stations in different hydrologic zones better than the existing single site AES equations. Finally, the proposed hierarchical regional GEV approach and depth-duration-frequency equations are combined to develop a new design storm estimation method at ungauged sites. This method is shown to be a viable alternative to the current arbitrary interpolation procedure from isoline maps.

Solar transient eruptions are the main cause of interplanetary-magnetospheric disturbances leading to the phenomena known as geomagnetic storms. Eruptive solar events such as coronal mass ejections (CMEs) are currently considered the main cause of geomagnetic storms (GMS). GMS are strong perturbations of the Earth’s magnetic field that can affect space-borne and ground-based technological systems. The solar-terrestrial impact on modern technological systems is commonly known as Space Weather. Part of the research study described in this thesis was to investigate and establish a relationship between GMS (periods with Dst ≤ −50 nT) and their associated solar and interplanetary (IP) properties during solar cycle (SC) 23. Solar and IP geoeffective properties associated with or without CMEs were investigated and used to qualitatively characterise both intense and moderate storms. The results of this analysis specifically provide an estimate of the main sources of GMS during an average 11-year solar activity period. This study indicates that during SC 23, the majority of intense GMS (83%) were associated with CMEs, while the non-associated CME storms were dominant among moderate storms. GMS phenomena are the result of a complex and non-linear chaotic system involving the Sun, the IP medium, the magnetosphere and ionosphere, which make the prediction of these phenomena challenging. This thesis also explored the predictability of both the occurrence and strength of GMS. Due to their nonlinear driving mechanisms, the prediction of GMS was attempted by the use of neural network (NN) techniques, known for their non-linear modelling capabilities. To predict the occurrence of storms, a combination of solar and IP parameters were used as inputs in the NN model that proved to predict the occurrence of GMS with a probability of 87%. Using the solar wind (SW) and IP magnetic field (IMF) parameters, a separate NN-based model was developed to predict the storm-time strength as measured by the global Dst and ap geomagnetic indices, as well as by the locally measured K-index. The performance of the models was tested on data sets which were not part of the NN training process. The results obtained indicate that NN models provide a reliable alternative method for empirically predicting the occurrence and strength of GMS on the basis of solar and IP parameters. The demonstrated ability to predict the geoeffectiveness of solar and IP transient events is a key step in the goal towards improving space weather modelling and prediction.

Thesis (Ph. D.) -- University of Maryland, College Park, 2007.
Thesis research directed by: Astronomy. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

This M. Sc. thesis studies the statistical characteristics of convective storms in a monsoon regime in Darwin, northern Australia. It has been conducted with the use of radar. Enhanced knowledge of tropical convection is essential in studies of the global climate, and this study aims to bring light on some special characteristics of storms in a tropical environment. The observed behaviour of convective storms can be implemented in the parameterisation of these in cloud-resolving regional and global models. The wet season was subdivided into three regimes; build-up and breaks, the monsoon and the dry monsoon. Using a cell tracking system called TITAN, these regimes were shown to support different storm characteristics in terms of their temporal, spatial and height distributions. The build-up and break storms were seen to be more vigorous and particularly modulated diurnally by sea breezes. The monsoon was dominated by frequent but less intense and vertically less extensive convective cores. The explanation for this could be found in the atmospheric environment, with monsoonal convection having oceanic origins together with a mean upward motion of air through the depth of the troposphere. The dry monsoon was characterised by suppressed convection due to the presence of dry mid-level air. The effects of wind shear on convective line orientations were examined. The results show a diurnal evolution from low-level shear parallel orientations of convective lines to low-level shear perpendicular during build-up and breaks. The monsoon was dominated by complex orientations of convective lines. The thesis includes a study of merged and splitted cells, which have been separated from other storms, and mergers were shown to support more vigorous convection in terms of height distribution and reflectivity profiles. They were also seen to be the most long-lived category of storms as well as the most common type. Split storms were generally weaker, indicative of their general tendency to decay shortly after the split occurred.
En statistisk studie av konvektiva celler i en miljö som präglas av monsunförhållanden har utförts i Darwin, norra Australien, med hjälp av radar. En ökad förståelse for tropisk konvektion är nödvändig for att kunna studera klimatet globalt. Denna studie har bidragit till denna kunskapsbas genom att studera några viktiga parametrar hos konvektiva celler i en tropisk miljö. De observerade egenskaperna hos dessa celler kan implementeras i parametriseringen av högupplösta regionala och globala modeller. Regnperioden delades upp i tre olika regimer; uppbyggnad och avbrott, monsun och torr monsun. Genom att använda ett cellsökande system kallat TITAN, visade sig dessa regimer uppvisa olika karakteristika vad gäller tids- och rumsmässig samt vertikal distribution av konvektionsceller. Uppbyggnad- och avbrottsregimen dominerades av mäktiga och intensiva konvektionsceller, och modulerades av sjöbrisar på en daglig basis. Monsunen dominerades av talrika men mindre intensiva celler. Anledningen till detta kan finnas i atmosfäriska förhållanden, dar monsunen dominerades av konvektionsceller med oceanisk härkomst och allmän hävning genom större delen av troposfären. Den torra monsunen präglades av försvagad konvektion på grund av närvaron av mycket torr luft på medelhöga nivåer. Effekten av vindskjuvning på orienteringen av bylinjer undersöktes. Resultaten visar att en daglig övergång från en orientering som var parallell med vindskjuvningsvektorn till en vinkelrät orientering dominerade under uppbyggnad och avbrott. Monsunen präglades av komplexa orienteringar av bylinjer. Sammanväxande och splittrande celler separerades fran andra celler och undersöktes speciellt. De sammanväxande cellerna uppvisade mer intensiv konvektion och större vertikal maktighet. Denna kategori av celler, som var den vanligaste typen av ickeisolerade celler, levde också längre än andra celltyper. Splittrande celler var generellt svagare än andra celler, vilket indikerade den generella tendensen för denna celltyp att brytas ner strax efter det att en splittring ägt rum.

In this thesis, the role of mid-latitude cyclones in air pollution transport in the Northern Hemisphere is quantified. The storm tracking model, TRACK, is used to study the mechanisms through which pollution, specifically ozone (O3) and carbon monoxide (CO), are vented from the boundary layer to the free troposphere and thus transported over large distances, as well as the introduction of O3 from the stratosphere into the troposphere. The relationship between mid-latitude cyclones and air pollution transport of O3 and CO is explored for the first time using the Monitoring Atmospheric Composition and Climate (MACC) reanalysis, a combined meteorology and composition reanalysis dataset. A comparison between springtime surface ozone measurements at rural background sites on the west coast of Europe and cyclone track frequency in the surrounding regions was used to first establish the correlation between cyclone location and surface air quality. The focus is on spring as it tends to be the season of maximum intercontinental transport of O3. The surface observations were compared to the MACC O3 values at the same locations and case studies of how cyclones can influence surface O3 measurements are described. When cyclones track north of 53°N, there is a significant probability that the surface O3 will be high (> the 75th percentile), due to the close proximity to stratospheric intrusions and the transport at low levels across the North Atlantic Ocean. The most intense spring cyclones (95th percentile) were selected for two regions, the North Atlantic and the North Pacific, for further investigation into the mechanisms which impact O3 and CO concentrations near cyclones. These intense cyclones ( 60 over each region) often tracked over the major emission sources of eastern North America and East Asia. The distributions of MACC O3 and CO within a "typical" intense cyclone are examined by compositing the cyclones together. The cyclone-centered composites were compared to background composites of "average conditions" created by sampling the reanalysis data of the previous year to the cyclone locations. Mid-latitude cyclones are found to redistribute concentrations of O3 and CO horizontally and vertically throughout the cyclone. This is clearly shown to occur through two main mechanisms: (1) vertical lifting of CO-rich and O3-poor air isentropically from near the surface to the mid- to upper-troposphere in the region of the warm conveyor belt; and (2) descent of O3-rich and CO-poor air isentropically in the vicinity of the dry intrusion, from the stratosphere toward the mid-troposphere. This work was expanded to identify the links between teleconnection patterns, mainly the North Atlantic Oscillation (NAO), that affect the major storm track pathways in the North Atlantic sector and the distribution of MACC O3 and CO throughout the troposphere and lower stratosphere. For this analysis, TRACK was used to calculate seasonal weighted-average O3 and CO distribution maps based on the monthly NAO index. During positive NAO phase, the persistence of low pressures over the North Atlantic coupled with the Azores High promotes transport across the North Atlantic throughout the troposphere. During negative NAO phase, blocking high pressure in the eastern North Atlantic are known to occur, which shifts transport pathways to a more southerly zonal flow. This work demonstrates the complex relationship between the horizontal and vertical distribution of pollution, including surface concentrations, and synoptic-scale systems.

Previous studies on the effects of land cover influence on stream nitrogen have focused on base flow conditions or were conducted specifically within urbanized or primarily agricultural watersheds. While these studies have shown relationships between land cover and nitrogen, this relationship and the scale of influence could change during storms. The purpose of my study was to understand how land cover influences nitrogen in streams during storms. This was address using nine watersheds within the Little Tennessee Basin in North Carolina. While this basin is primarily forested, the nine watersheds have mixed agricultural, built, and forest land cover. Land cover influences were addressed through nitrogen concentration/discharge patterns, nitrogen concentration relationship to land cover, and comparison of storm and base flow nitrogen concentrations over time. Weekly base flow samples and samples from six storm were collected in 2010-2011. Total dissolved nitrogen (TDN), nitrate (NO??), dissolved organic nitrogen (DON), and ammonium (NH?⁺) concentrations were compared among sites. During most storms, DON peaked before the peak of the discharge while NO?? peaked after the peak of the storm. This suggest that DON could be coming from a near stream source or surface runoff while NO?? could be from longer pathways such as subsurface flow or from sources further away on the watershed. NO?? concentration varied among sites, while DON concentration varied more between base flow and storm samples. Examining the different landscape scales from 200-m local corridor, 200-m stream corridor, and entire watershed, watershed land cover was the best predictor for all the nitrogen concentrations. Agricultural and built combined best predicted TDN and NO??, while agricultural land cover was a better predictor of DON. For storms, nitrogen concentrations did not show seasonal patterns but was more related to discharge. Nitrogen concentration increased with discharge during storms and the more intense and longer storms had higher TDN and NO?? concentrations. However, conflicting seasonal trends were seen in monthly base flow. The more forested watersheds had high NO?? during the summer and low NO?? in the winter. For sites with higher NO??, the seasonality was reversed, with higher winter NO?? concentration. The least forested site had relatively constant nitrogen through the year at base flow and concentration decreased for most storms. Further studies on storms and nitrogen transport are needed to understand better the seasonal patterns of nitrogen input during storms.
Master of Science

Currently available wind-wave prediction models require a prohibitive amount of computing time for simulating non-linear wave-wave interactions. Moreover, some parts of wind-wave generation processes are not fully understood yet. For this reason accurate predictions are not always guaranteed. In contrast, Artificial Neural Network (ANN) techniques are designed to recognize the patterns between input and output so that they can save considerable computing time so that real-time wind-wave forecast can be available to the navy and commercial ships. For this reason, this study tries to use ANN techniques to predict waves for winter storms and hurricanes with much less computing time at the five National Oceanic and Atmospheric Administration (NOAA) wave stations along the East Coast of the U.S. from Florida to Maine (station 44007, 44013, 44025, 44009, and 41009). In order to identify prediction error sources of an ANN model, the 100% known wind-wave events simulated from the SMB model were used. The ANN predicted even untrained wind-wave events accurately, and this implied that it could be used for winter-storm and hurricane wave predictions. For the prediction of winter-storm waves, 1999 and 2001 winter-storm events with 403 data points had 1998 winter-storm events with 78 points were prepared for training and validation data sets, respectively. In general, because winter-storms are relatively evenly distributed over a large area and move slowly, wind information (u and v wind components) over a large domain was considered as ANN inputs. When using a 24-hour time-delay to simulate the time required for waves to be fully developed seas, the ANN predicted wave heights (r = 0.88) accurately, but the prediction accuracy of zero-crossing wave periods was much less (r = 0.61). For the prediction of hurricane waves, 15 hurricanes from 1995 to 2001 and Hurricane Bertha in 1998 were prepared for training and validation data sets, respectively. Because hurricanes affect a relatively small domain, move quickly, and change dramatically with time, the location of hurricane centers, the maximum wind speed, central pressure of hurricane centers, longitudinal and latitudinal distance between wave stations and hurricane centers were used as inputs. The ANN predicted wave height accurately when a 24-hour time-delay was used (r = 0.82), but the prediction accuracy of peak-wave periods was much less (r = 0.50). This is because the physical processes of wave periods are more complicated than those of wave heights. This study shows a possibility of an ANN technique as the winter-storm and hurricane-wave prediction model. If more winter-storm and hurricane data can be available, and the prediction of hurricane tracks is possible, we can forecast real-time wind-waves more accurately with less computing time.

Defence date: 07 March 2022
Examining Board: Lucy Riall (European University Institute); Pieter Judson (European University Institute); Florencia Peyrou Universidad Autónoma de Madrid); Stephen Jacobson, (Universitat Pompeu Fabra)
This thesis explores the effect of the 1848 revolutionary cycle in Spain and its imperial space, focusing on its global connections and on the intersections between revolution, counterrevolution, and empire building. In doing so, it aims to contribute to a global approach to the 1848 revolutions that goes beyond perspectives that are exclusively centred on Europe as space. In this thesis, mid-nineteenth century Spain is understood not as a nation-state within the Iberian Peninsula, but as a fluid global empire with colonies, diasporas, and exile communities in various spaces. Considering the chronological frame of a “long 1848” and using various scales, this thesis stresses the continuities between the political upheavals and international reconfigurations that occurred around the year 1846, and the revolutionary events of 1848-1849. This thesis opposes the traditional image of Spain as an exception to the revolutionary cycle. It argues that the Parisian Revolution did in fact have a significant impact on the Iberian Peninsula, which prompted the Spanish government to develop counterrevolutionary measures on both sides of the Atlantic. Exile communities in Europe and spaces like Paris, Oran or New Orleans profited from the occasion presented by the 1848 revolutions to challenge either the political status quo in the metropole or the colonial order in the Caribbean. This generated a flow of transnational mobilities of revolutionary (and counterrevolutionary) actors, information, propaganda, and material; mobilities that diverse state actors tried to curtail through various means to prevent revolutionary contagion. At the same time, hundreds of political prisoners were sent to overseas possessions as part of a repressive repertoire that combined counterrevolution and colonisation through the relocation of convicts. Finally, this thesis explores the changes to several political cultures in the Spanish empire during the early 1850s as a result of the revolutionary cycle.

Alabama, also known as the Dixie state, is no stranger to severe weather. Severe weather can occur during much of the year. Experienced local forecasters have long suspected that North and Central Alabama has its own tornado alley. Many of these forecasters have noticed storm tracks as well as tornado tracks to be similar to past historic events. Many questions have risen about the exact influential factors that cause convective initiation and tornadic development. For example the effects of terrain, water, and population on tornado climatology will be discussed in this study. The sometimes unreliable climatology of tornadoes will be addressed as well as the history of storm reporting. Tornado clusters were found and further explained regarding relationships with terrain, water, and population. Through this research, it is concluded that there are two distinct tornado regions that exist in North and Central Alabama.

Rainfall data are usually gathered at daily timescales due to the availability of daily rain-gauges throughout the world. However, rainfall data at fine timescale are required for certain hydrologic modellings such as crop simulation modelling, erosion modelling etc. Limited availability of such data leads to the option of daily rainfall disaggregation. This research investigates the use of a stochastic rainfall disaggregation model on a regional basis to disaggregate daily rainfall into any desired fine timescale in the State of Queensland, Australia. With the incorporation of seasonality into the variance relationship and capping of the fine timescale maximum intensities, the model was found to be a useful tool for disaggregating daily rainfall in the regions of Queensland. The degree of model complexity in terms of binary chain parameter calibration was also reduced by using only three parameters for Queensland. The resulting rainfall Intensity-Frequency-Duration (IFD) curves better predicted the intensities at fine timescale durations compared with the existing Australian Rainfall and Runoff (ARR) approach. The model has also been linked to the SILO Data Drill synthetic data to disaggregate daily rainfall at sites where limited or no fine timescale observed data are available. This research has analysed the fine timescale rainfall properties at various sites in Queensland and established sufficient confidence in using the model for Queensland.

This thesis investigates severe local storms in the United Kingdom, specifically tornadoes, waterspouts and severe hailstorms. Reference is also made to the United Kingdom's place in the tornado climatology of Europe and some comparisons are made with the United States. Outline forecast guidance is then considered. A major part of this thesis was the development of computerised tornado, waterspout and severe hailstorm data for the United Kingdom, followed by the validation and verification of as much of the component information as was reasonably possible. A European tornado and waterspout data base was developed likewise. Events that have been reported during the research period have been added to ensure that the data bases are up-to-date. Tornado, waterspout and severe hailstorm climatologies for the United Kingdom are presented. The place of the United Kingdom in the tornado climatology of Europe is discussed and comparisons are made with the tornado climatology of the United States. From the climatologies and several case studies, the possibilities of prediction, detection and warning are considered in outline. It is very much hoped and intended that this research will perpetuate further and more detailed research, as well as development and education. To this end, the thesis concludes with an internet web site on severe weather in general, which has been developed in parallel with this research. The site, of the Tornado and Storm Research Organisation, includes questionnaires developed by the writer which have already proven very useful in attracting numerous new reports of severe weather and also in greater detail than before. The site also serves to increase the awareness of severe weather in the United Kingdom and Europe, as well as to educate visitors about it. The web site in particular lends itself to on-going development.

This study is concerned with the preparation of a research datum line in historical climatology and will provide a valuable data set for a wide variety of researchers in the future who are interested in the relationship between aspects of the coastal and climate systems and the human-coastal environment interface. The principal objective was to create and prepare an original historical data base on the storms, floods, erosion events and sand movements in Scotland 1500-1991 A.D.

Thesis (MScEng)--Stellenbosch University, 2013.
ENGLISH ABSTRACT: Geomagnetic storms are primarily driven by the rapid transfer of energy from the solar wind to the magnetosphere. The mechanism of energy transfer involves the merging of the interplanetary magnetic field to the geomagnetic field in a process known as magnetic reconnection. This leads to an influx of energetic, charged particles into the magnetosphere so that current systems are enhanced. Specifically, an increase in the equatorial ring current leads to a decrease in the surface field. Geomagnetic storms are thus characterized by a strong decline in the horizontal components of the geomagnetic field, lasting from several hours to days. The intensity of a storm is described by the disturbed storm-time index, which is essentially a measure of the deviation from the typical quiet day variation along the equator. Severe storms can lead to the disruption of high frequency (HF) communications as a consequence of a strongly perturbed ionosphere. By the same token, the global positioning system (GPS) can become highly unreliable during magnetically disturbed conditions, yielding distance errors as large as 50 meters. The impact of geomagnetic activity and other solar-driven processes on technology systems are collectively known as space weather. Magnetic field sensing thus forms an important part of space weather forecasting and is vital to space science research as a means of improving our understanding of solar wind-magnetosphere interactions. This study examines the use of magnetometers built as SQUIDs (Superconducting Quantum Interference Devices) for monitoring the geomagnetic field for space weather forecasting purposes. A basic theory of superconductivity is presented and subsequently the key aspects governing the operation of SQUIDs are discussed. Space weather is also introduced with respect to the various processes on the sun that perturb the magnetosphere and hence the geomagnetic field. The method of analysis was basically to Fourier-transform the data using the Wiener-Khintchine theorem. A systematic approach to Fourier analysis is thus presented, demonstrating the superiority of the Wiener-Khintchine theorem in noise reduction. The suitability of SQUID magnetometers for space science research is demonstrated by a comparative study between SQUID and fluxgate datasets for magnetic storms during 2011. Strong correlation was observed between the frequency content of the SQUID and fluxgate signals. This result supports South Africa’s SQUID project, currently undertaken as a collaborative effort between SANSA Space Science and the Department of Electrical and Electronic Engineering at Stellenbosch University. This thesis thus lays a foundation for future research involving advanced magnetometry using SQUIDs.
AFRIKAANSE OPSOMMING: Geomagnetiese storms word hoofsaaklik gedryf deur die vinnige oordrag van energie van die sonwind na die magnetosfeer. Die meganisme van energie oordrag behels die samesmelting van die interplanetêre magneetveld met die geomagneetveld, in 'n proses wat bekend staan as magnetiese heraansluiting. Dit lei tot 'n instroming van energieke elektries-gelaaide deeltjies, tot in die magnetosfeer, met die gevolg dat magnetosferiese elektriese stroomstelsels versterk word. 'n Toename in die ekwatoriale ringstrome lei spesifiek tot 'n afname in die horisontale komponent van die geomagnetiese veld. Geomagnetiese storms word dus gekenmerk deur 'n sterk afname in die horisontale komponent van die geomagnetiese veld, ‘n afname wat etlike ure tot dae kan duur. Die intensiteit van 'n storm word beskryf deur die storm-tyd versteurings indeks , 'n maatstaf van die afwyking van die tipiese stil dag magnetiese variasie langs die ewenaar. Ernstige storms kan lei tot die ontwrigting van hoë frekwensie (HF) kommunikasie as 'n gevolg van 'n erg versteurde ionosfeer. Soortgelyk kan die Globale Posisionering Stelsel (GPS) hoogs onbetroubaar word tydens magneties versteurde toestande, en posisiefoute so groot as 50 meter veroorsaak. Die impak van geomagnetiese aktiwiteit en ander sonkrag gedrewe prosesse op tegnologie is gesamentlik bekend as ruimteweer. Magneetveldmetinge vorm dus 'n belangrike deel van ruimteweervoorspelling en is noodsaaklik vir ruimtewetenskaplike navorsing as 'n middel om die sonwind-magnetosfeer interaksies beter te verstaan. Hierdie studie ondersoek die gebruik van SQUID (Engels: Superconducting Quantum Interference Device) magnetometers vir die monitering van die geomagnetiese veld vir ruimteweervoorspellingsdoeleindes. ’n Basiese teorie van supergeleiding word aangebied, waarvolgens die sleutelaspekte van SQUIDs bespreek word. Ruimteweer word ook voorgestel in terme van die verskillende prosesse op die son wat die aarde se magnetosfeer en dus die geomagnetiese veld versteur. Die analisemetode wat hier gebruik word, is om die Fourier-transform van data met die Wiener-Khintchine theorema te bereken. A sistematiese metode vir Fourier-analise word aangebied, wat die superiorireit van die Wiener-Khintchine teorema vir ruisvermindering demonstreer. Die geskiktheid van SQUID magnetometers vir ruimtewetenskaplike navorsing word gedemonstreer deur ’n vergelykende studie tussen SQUID- en vloedhek-datastelle vir magnetiese storms gedurende 2011. Sterk korrelasie is waargeneem tussen die frekwensie-inhoud van die SQUID- en vloedhekseine. Hierdie resultate ondersteun Suid-Afrika se SQUID-projek, wat tans as ’n samewerkingspoging tussen SANSA Space Science en die Departement Elektriese en Elektroniese Ingenieurswese aan die Universiteit van Stellenbosch bedryf word. Hierdie tesis lê ’n fondasie vir toekomstige navorsing oor gevorderde magnetometrie met SQUIDs.

Weathering the entrepreneurial storm is considered by many an art form in itself but an undeniable, universal truth is the unilateral impact of an extraordinary leader on the chances of triumph in the face of great adversity. Yet the focus of academic studies all too often concerns the understanding of the weather patterns, the choice of captain and the direction of the ship rather than how to turn the wheel, raise the mast or set the sails. This study has the aim of deciphering the routines, actions and methods of entrepreneurial leaders so as to produce tangible, actionable knowledge which real practitioners can bestow upon themselves. This is a collective case study which examines ten entrepreneurial leaders from various cities throughout Sweden using semi-structured, in-depth interviews. The findings pertain to routines, activities and methods that they use to fulfil five roles of effective entrepreneurial leadership which are further boiled down to 52 thematic strategies. These strategies are then aligned into five fundamental skills; encompassing a collective approach, building individual relationships, fragmentation, dynamic perspective and utilising feedback. We believe that through developing these skills that entrepreneurial leaders can better cultivate their own routines, activities and methods contingent to their particular circumstance and transaction set.

It has been shown in ionospheric research that modelling total electron content (TEC) during storm conditions is a big challenge. In this study, mathematical equations were developed to estimate TEC over Sutherland (32.38⁰S, 20.81⁰E), during storm conditions, using the Empirical Orthogonal Function (EOF) analysis, combined with regression analysis. TEC was derived from GPS observations and a geomagnetic storm was defined for Dst ≤ -50 nT. The inputs for the model were chosen based on the factors that influence TEC variation, such as diurnal, seasonal, solar and geomagnetic activity variation, and these were represented by hour of the day, day number of the year, F10.7 and A index respectively. The EOF model was developed using GPS TEC data from 1999 to 2013 and tested on different storms. For the model validation (interpolation), three storms were chosen in 2000 (solar maximum period) and three others in 2006 (solar minimum period), while for extrapolation six storms including three in 2014 and three in 2015 were chosen. Before building the model, TEC values for the selected 2000 and 2006 storms were removed from the dataset used to construct the model in order to make the model validation independent on data. A comparison of the observed and modelled TEC showed that the EOF model works well for storms with non-significant ionospheric TEC response and storms that occurred during periods of low solar activity. High correlation coefficients between the observed and modelled TEC were obtained showing that the model covers most of the information contained in the observed TEC. Furthermore, it has been shown that the EOF model developed for a specific station may be used to estimate TEC over other locations within a latitudinal and longitudinal coverage of 8.7⁰ and 10.6⁰ respectively. This is an important result as it reduces the data dimensionality problem for computational purposes. It may therefore not be necessary for regional storm-time TEC modelling to compute TEC data for all the closest GPS receiver stations since most of the needed information can be extracted from measurements at one location.

The predictability of beach inundation is mainly related to wave runup and most of the formulations that have been developed focus on the hydrodynamics, disregarding the morphological changes caused during storms. For these reasons, the aim of this thesis is to provide more insight into beach inundation processes at embayed and open beaches and to determine how morphological changes can interfere with these processes. To this end, video measurements of beach inundation and the characteristic morphological changes were carried out at two stretches of coast with different wave climates: the stretch comprising La Barceloneta, Somorrostro and Nova Icaria, which are three artificial, tideless embayed beaches located in Barcelona, Spain (NW Mediterranean); and Noordwijk beach, which is an open, microtidal multibarred beach located in Noordwijk, the Netherlands (North Sea). The effects of a submerged and a detached breakwaters on the morphological and hydrodynamic changes occurring at La Barceloneta during storms is examined in chapter 2. The shoreline response before and after the beach nourishment and the construction of the protective structures was compared using a ten-year video-recorded dataset and hydrodynamics modelled using the SMC model. As a result of the protection works, La Barceloneta was divided into two beaches separated by a salient. A new methodological approach to analyzing beach rotation which eliminates the morphological effect is presented. Results indicate that the beach rotation process has been modified caused by a change in the wave-induced current system from a single dominant alongshore current to one composed of two dominant alongshore currents with opposite directions. In chapter 3, beach inundation affecting the three embayed beaches of Barcelona during the 17 strongest storm events of the period 2001-2008 is analyzed using daily time-exposure images. The shoreline variability due to storms was split into beach planform and morphological features in order to determine its influence on beach inundation measurements. The characterization of the inundation depended on the orientation with respect to the wave direction approach and the morphological features. Beach planform changes are the foremost influence on the inundation of Barcelona beaches. The inundation at the multibarred beach of Noordwijk during the seven strongest storms in the period between 1998 and 2005 is estimated, also using video monitoring techniques in chapter 4. Additionally, the influence of subtidal sandbars on the inundation is analyzed using the XBeach model. To this end, six simulations were carried out using barred profiles measured at Noordwijk but differing in sandbar height and location, and one simulation using a synthetic barless profile. Inundation values ranged from 22 to 105 m, with considerable alongshore variation before the peak of each storm because of the presence of the intertidal bars. The mean inundation values along the beach are well estimated using a simple inundation parameter. The XBeach model shows that the inundation is only affected by the morphology close to the shoreline (i.e. by the intertidal bars or the inner bar if it is wide and closer to shoreline). The outer bar does not seem to influence Beach inundation prediction at Somorrostro beach is evaluated in chapter 5. To this end, inundation measurements using video observations are compared with estimations including the tidal variations and the wave runup formulation of Stockdon et. al (2006) introducing deep water and local wave measurements and computations. The inundation is overestimated if any of the wave heights in the formulation are used. Estimations improved if a local wave height is used, in particular for waves approaching the shore obliquely. Finally, the alongshore variability of the inundation is better captured if the wave runup is assumed proportional to the breaking wave heightBARCELONA07
Las costas están expuestas a la erosión y la inundación producida por los temporales, los cuales son muy frecuentes y pueden producir grandes daños y pérdidas económicas. La inundación producida por los temporales es debida a la marea astronómica y meteorológica y al remonte del oleaje. La predicción de la inundación de la playa está principalmente relacionada con el remonte y la mayoría de las formulaciones propuestas se centran en parámetros hidrodinámicos sin tener en cuenta los cambios morfológicos causados durante los temporales. Por todo ello, el principal objetivo de esta tesis es proporcionar un mayor conocimiento de los procesos de inundación en playas encajadas y abiertas y determinar cómo los cambios morfológicos pueden interferir con estos procesos. Para ello, se han llevado a cabo medidas de la inundación y de los cambios morfológicos característicos utilizando imágenes de video en dos tramos de costa con climas de oleaje diferente: el tramo que comprende las playas de La Barceloneta, Somorrostro and Nova Icaria, las cuales son tres playas artificiales, encajadas y sin marea localizadas en Barcelona, España (NO Mediterráneo); y la playa de Noordwijk, la cual es una playa abierta, multibarrada y micromareal localizada en Noordwijk, Holanda (Mar del Norte). Los efectos de un dique sumergido y un dique exento en los cambios morfológicos e hidrodinámicos ocurridos en la playa de La Barceloneta durante temporales se examinan en el capítulo 2. La respuesta de la línea de orilla antes y después de la regeneración de la playa y de la construcción de las estructuras de protección se compara utilizando 10 años de video imágenes y la hidrodinámica modelada utilizando el Sistema de Modelado Costero (SMC). Como resultado de estas obras de protección, La Barceloneta quedó dividida en dos playas independientes separadas por un saliente. Una nueva metodología para analizar la rotación de la playa que elimina los cambios morfológicos es propuesta. Los resultados indican que la tendencia erosiva previamente observada en la zona noreste de la playa sigue estando presente en la actual playa noreste y está relacionada con el nuevo dique sumergido. Además, el proceso de rotación de la playa se ha modificado, produciéndose solamente en sentido contrario a las agujas del reloj en la playa noreste y en sentido horario en la playa suroeste. Este nuevo comportamiento es debido al cambio en el patrón de corrientes previamente formado por una corriente longitudinal dominante, a un sistema de corrientes compuesto por dos corrientes longitudinales en direcciones opuestas. En el capítulo 3, la inundación producida en las tres playas encajadas de Barcelona durante los 17 temporales más energéticos del periodo 2001-2008 es analizada utilizando imágenes diarias promediadas. La variabilidad de la línea de orilla debida a los temporales es discriminada en cambios en la forma en planta y morfologías (cúspides de playa, megacúspides, ondulaciones y saliente) para determinar su influencia en las medidas de inundación de la playa. La caracterización de la inundación dependió de la orientación respecto de la dirección de aproximación del oleaje y de las morfologías. Los cambios en la forma en planta de la playa son la máxima influencia en la inundación de las playas de Barcelona. Los cambios en la forma en planta hacia tierra y los cambios en el saliente suponen casi un 50% de la máxima inundación medida, mientras que las megacúspides y la ondulación suponen aproximadamente el 25%. El efecto de las cúspides de playa en la inundación es despreciable. Consecuentemente, la variación en la línea de orilla durante temporales influye significativamente los valores de inundación, especialmente en playas con pendientes fuertes. Pequeñas variaciones en la pendiente de la playa pueden sin embargo afectar sustancialmente la inundación en playas con pendientes suaves. La inundación de la playa multibarrada de Noordwijk durante los 7 temporales más fuertes ocurridos en el periodo comprendido entre 1998 y 2005 es también estimada utilizando medidas de video monitorización en el capítulo 4. Además, la influencia de las barras submareales en la inundación es analizada utilizando el modelo XBeach. Para ello, se realizaron siete simulaciones 1-D sin considerar los cambios morfológicos; seis simulaciones utilizando perfiles barrados medidos en la playa de Noordwijk pero que difieren en altura y localización de las barras, y una simulación utilizando un perfil ideal sin barras. Los valores de inundación oscilaron entre 22 y 105 m, con variaciones considerables a lo largo de la playa antes del pico del temporal debido a la presencia de barras intermareales. La inundación promedio a lo largo de la playa es estimada considerablemente bien utilizando un parámetro de inundación sencillo que incluye la pendiente intermareal y supramareal, la altura de ola y la longitud de onda en aguas profundas y la marea meteorológica. El modelo XBeach muestra que la inundación está solamente afectada por la morfología próxima a la línea de orilla, esto es, por las barras intermareales o por la barra interna si es ancha y próxima a la orilla. La barra externa no parece tener influencia en el comportamiento de la inundación. La predicción de la inundación en la playa de Somorrostro es evaluada en el capítulo 5. Para ello, medidas de la inundación utilizando observaciones de imágenes de video se comparan con estimaciones de la inundación incluyendo las variaciones de la marea y el fórmula del remonte de Stockdon et al. (2006), introduciendo medidas locales y en aguas profundas del oleaje así como oleaje modelado. Debido a que las observaciones corresponden a un remonte medio y las estimaciones usan el remonte excedido un 2% (R2%), la inundación es sobreestimada para cualquier altura de ola utilizada en la fórmula. Sin embargo, las estimaciones mejoran si una altura de ola medida a 10 m es utilizada en la fórmula en particular para oleajes con una aproximación oblicua a la línea de orilla. Finalmente, las diferencias entre las observaciones y las estimaciones varían a lo largo de la playa, siendo mayores en la zona de curvatura de la playa. La variabilidad de la inundación a lo largo de la playa es mejor caracterizada si el remonte se asume igual que la altura de ola en rotura.

This thesis presents a maritime archaeology of the medieval port town of Winchelsea, in East Sussex, United Kingdom. It specifically researches the aspects of seafaring and storminess which are shown to be vital for understanding how the town was structured and how life was lived. The study brings together a variety of sources – many collected during a fieldwork project at the ancient waterfront – which allowed for the production of a narrative about a community whose attitudes towards the sea shifted over time. In the process, a number of theoretical and methodological tools were developed that allow for (medieval) port towns to be studied in new ways, unhindered by any remaining perceived boundaries between the maritime and terrestrial spheres. The theoretical underpinning that functions as the study’s foundation is a relational approach – the maritime townscape – aided by two theoretical devices – rhythmanalysis and spatial trialectics – that encourage researchers to consider how the dynamisms of everyday life in a port were materialized in the past and how they can be studied and reconstructed by archaeologists. Approaching Winchelsea from the water, materials and places are discussed as they are encountered along the way. The ship archaeological material from the region is synthesized and contextualised within developments in shipbuilding in northwest Europe. This material serves as the basis for a discussion of the types and sizes of ships that would have called at medieval Winchelsea and the organisation and working of the Camber Estuary which functioned as the new town’s roadstead. These findings are subsequently related to New Winchelsea’s waterfront. Taking the results of a geotechnical survey conducted as part of this project as a starting point, the available information about the area is brought together and the first archaeological interpretation of how the waterfront was structured and could have functioned is put forward. Venturing into the town itself, the tools of spatial analysis are used to raise questions about Winchelsea’s seemingly simple grid-like structure and it is argued that the town was laid out with seafaring in mind. Yet, this structure imposed on a population in a top-down manner was to a large extent negotiated by the people’s own attitudes and affordances. One of the most telling indications of these are the remarkable instances of ship graffiti in the town – in St Thomas’ church and Blackfriars Barn undercroft – which were recorded using reflectance transformation imaging (RTI) and analysed. While highlighting the complexities involved in interpreting and finding meaning in ship graffiti, it is nonetheless argued that they demonstrate a multifaceted relationship with the sea. Finally, a local proxy for high-energy events is developed by dating a rhythmite sequence from a core extracted from the silted River Brede using paleomagnetic secular variation (PSV) and subjecting it to geochemical analysis (micro-XRF) using the ITRAX core scanner. This proxy allowed Winchelsea’s history of storminess to be both refined and contextualised within wider developments of medieval climate change. Working on the series of storm events that led to the destruction of ‘old’ and the founding of ‘new’ Winchelsea, it is proposed that the production of localised well-dated environmental proxies could contribute to solving methodological difficulties with reconciling information about weather events from written records and information about climate from environmental proxies. The localised proxy for high-energy events generated at Winchelsea revealed that weather conditions seemingly worsened in the second half of the thirteenth century, at the eve of the transition from the Medieval Climatic Anomaly (AD 950-1250) to the Little Ice Age (AD 1400-1700), forcing the residents of Old Winchelsea to protect themselves by building sea defences and ultimately requiring them to relocate to a nearby hilltop. Stimulated by the theoretical device of spatial trialectics, the choice of the new site, located c. 1.5 km inland, is interpreted, not only as a way of physically protecting oneself, but also as suggestive of a growing unease towards the sea. The results of the geotechnical survey indicate that the waterfront at the new site needed a certain amount of work to keep it viable as an access point to the water and provides physical evidence for what is suggested in the written sources: it was “perilous at all flowings of the tide”. Yet, the ambition reflected in the town’s layout and the fact that systems were put in place that allowed Winchelsea to continue functioning as a port, hint at a multifaceted relationship with the sea. Encouraged by the theoretical toolkit of rhythmanalysis, it is shown that people’s daily lives in Winchelsea were, to a large extent, lived to the rhythms of the sea: from millennial and centennial storminess down to the yearly sailing season and the daily tidal cycles. Yet, people’s activities emerged with the rhythms of the sea and not as a result of them. The complexity of this relationship is perhaps captured best by the ship graffiti. On the one hand, people found it necessary to engrave ship drawings in stone pillars in St Thomas, perhaps to acquire some form of spiritual protection from the sea, while – at the same or at a different time – also scratching ship drawings in wet plaster in an ostensibly secular undercroft, perhaps commemorating the mustering of a large naval fleet before setting out, and therefore seemingly celebrating the beneficial aspects of living beside the sea.