À l'échelle du monde, les littoraux peuvent se diviser en différentes catégories : les côtes rocheuses, sableuses, vaseuses et mixtes. Cependant, les littoraux meubles sableux et vaseux sont retrouvés régulièrement mélangés sur différentes façades côtières mondiales. Des apports de vases temporaires ou permanents sont en effet observés sur des plages sableuses. Ces environnements mixtes atypiques, qui couplent alors les processus d’érosions, de transports et de dépôts associés à la fois aux sédiments cohésifs et non cohésifs, ont été peu étudiés. Afin d’identifier les forçages des variations morpho-dynamiques sur des environnements sableux et mixtes, quatre plages sablo-vaseuses ou entièrement sableuses de type Low-Tide-Terrace ont été suivies mensuellement sur deux années en baie et estuaire de la Vilaine (Bretagne Sud). Des suivis hydro-morpho-sédimentaires spécifiques à haute résolution et des suivis par photogrammétrie ont été menés ponctuellement sur ces sites. À l'échelle régionale, ce travail met en évidence le rôle de la morphologie initiale et l’héritage géologique régional dans la réponse morphologique du littoral de la baie de Vilaine aux conditions d’énergie extrêmes. La capacité de résilience à moyen-terme du littoral des plages de Bretagne Sud a été démontrée. Dans une approche plus spécifique, un comportement morphodynamique d'une plage sablo-vaseuse proche de celle d'une plage uniquement sableuse a été observé lors des phases de haute énergie. Les variations d’altitudes du platier vaseux et des modelés sédimentaires en ridges and runnels sont principalement contrôlées par l’énergie des vagues mais également par les propriétés physiques des sédiments et particulièrement celles liées à l'interaction entre le sable provenant de la section réflective et la vase de la section dissipative. La capacité d’érosion du platier vaseux par les vagues est potentiellement diminuée au niveau des interfaces des sédiments cohésifs et non-cohésifs. / At the world scale, coastal areas can be divided in several categories: rocky, sandy, muddy and mixed coasts. However, these sedimentary coasts are regularly found mixed. Temporary or permanent mud inputs are observed on the sandy beaches. These atypical mixed environments, coupling erosional, transports and deposits processes associated to cohesive and non-cohesive sediments have been poorly studied. So, understanding theirs morphological and sedimentary dynamics and the identification of regional and local forcings driving them are essential. Four sandy-muddy or fully sandy Low-Tide-Terrace beaches from the bay and estuary of Vilaine (South-Brittany) have been monthly monitored over two years to characterize their morphodynamics beahaviors. Specific monitoring of coupled hydrodynamics and morpho- sedimentary surveys and photogrammetry experiments have been conducted on mixed sandy- muddy or full sandy beaches. At a regional scale, this work highlights the role of the initial morphology and regional geology inheritance on the morphological response of the littoral zones to extreme energy conditions. Despite some erosion patterns in local parts of beaches, particularly close to shore protection structures, the mid-term recovery capacity of the south-Brittany coastal area after extreme wave energy conditions have been proved. In a more specific approach, the works regarding the sandy- muddy beach dynamic show a morphodynamics behaviour close to that of a fully sandy beach during high energy event. The mudflat elevation changes and the dynamic of the ridges and runnels sedimentary patterns are mainly controlled by the incoming waves but also by the own physical properties of the sediment, particularly those induced by the interaction between the sand from the reflective section and the mudflat. A sand deposit between mud layers potentially decreases the wave erosion capacity on the mudflat.

The occurrence of mid-latitude spread F (SF) over South Africa has not been extensively studied since the installation of the DPS-4 digisondes at Madimbo (30.88◦E, 22.38◦S), Grahamstown (33.32◦S, 26.50◦E) and Louisvale (28.51◦S, 21.24◦E). This study is intended to quantify the probability of the occurrence of F region disturbances associated with ionospheric spread F (SF) and L-band scintillation over South Africa. This study used available ionosonde data for 8 years (2000-2008) from the three South African stations. The SF events were identified manually on ionograms and grouped for further statistical analysis into frequency SF (FSF), range SF (RSF) and mixed SF (MSF). The results show that the diurnal pattern of SF occurrence peaks strongly between 23:00 and 00:00 UT. This pattern is true for all seasons and types of SF at Madimbo and Grahamstown during 2001 and 2005, except for RSF which had peaks during autumn and spring during 2001 at Madimbo. The probability of both MSF and FSF tends to increase with decreasing sunspot number (SSN), with a peak in 2005 (a moderate solar activity period). The seasonal peaks of MSF and FSF are more frequent during winter months at both Madimbo and Grahamstown. In this study SF was evident in ∼ 0.03% and ∼ 0.06% of the available ionograms at Madimbo and Grahamstown respectively during the eight year period. The presence of ionospheric irregularities associated with SF and scintillation was investigated using data from selected Global Positioning System (GPS) receiver stations distributed across South Africa. The results, based on GPS total electron content (TEC) and ionosonde measurements, show that SF over this region can most likely be attributed to travelling ionospheric disturbances (TIDs), caused by gravity waves (GWs) and neutral wind composition changes. The GWs were mostly associated with geomagnetic storms and sub-storms that occurred during periods of high and moderate solar activity (2001-2005). SF occurrence during the low solar activity period (2006-2008)can probably be attributed to neutral wind composition changes.

Storms play a significant role in beach morphodynamics. Storm-induced beach-profile changes and their longshore variations are investigated in this study. The impacts of four summer tropical storms and two series of winter storms over the last 10 years along the coast of Treasure Island were documented. Tropical storms Alberto in 2006, Fay in 2008, Debby in 2012, Hermine in 2016 and winter storms in winter seasons of 2014 and 2015 are discussed in this study. In general, the Treasure Island beach experienced more erosion generated by tropical storms with greater intensity, but shorter duration, as compared to winter storms due to lower waves, weaker wind and smaller storm surge. Winter storms typically do not generate high storm surge and generally do not cause erosion at the dune and back beach unless the pre-storm beach is very narrow. Based on pre- and post-storm beach-profile surveys along the coast of Treasure Island, the northern end of the barrier island, located directly downdrift of the John’s Pass tidal inlet, experienced erosion along the entire profile during the storms. Along the middle part of Treasure Island, dry beach suffered erosion during both the tropical storms and winter seasons while the nearshore zone suffered erosion during the tropical storms and experienced deposition during the winter seasons. Sunset Beach at the southern end experienced severe erosion during tropical storm Debby, but not during other storms. Winter seasons caused relatively small changes to the morphology of Sunset Beach. Deposition happened in the nearshore zone along Sunset Beach during winter storms. Survey line R143 at the very south end of Treasure Island suffered erosion in tropical storm Alberto, Debby and Hermine. Beach profile changes induced by Tropical storm Fay was different as compared to other tropical storms. Considerably less beach erosion occurred due to the large distance of the storm path from the study area. Overall, Sunshine Beach, bounded by John’s Pass inlet at northern end of Treasure Island, was influenced both by wave conditions and the tidal flows. Sediment transport was to the north along the coast of Sunshine Beach when wind direction was from south, e.g. during tropical storm Fay. However the northward sediment transport was blocked by the John’s Pass jetty. Therefore, deposition occurred at Sunshine Beach during tropical storm Fay. When wind direction was from north (e.g. during tropical storms Alberto and during the winter seasons), southward sediment transport was generated. Erosion occurs during the northerly approaching storms. The morphodynamics of the middle section of Treasure Island are influenced by the sand supply at the attachment point of John’s Pass ebb delta. Sunset Beach experienced various levels of erosion during the tropical storms not only because of the high wave, strong wind and high water level generated by storms, but also due to the higher waves associated with an offshore dredged pit.

[Summary] Chapter I . The general characteristics of solar radiation at metre wavelengths are described, with reference to data published in the literature. A brief description of some aspects of solar physics relevant to the study of solar noise is given, and the literature relating to the correlation of radio effects with solar disturbances is reviewed. Chapter II. A concise description of the apparatus constructed for the continuous recording of the flux density of solar radio noise at a frequency of 300 Mc/s is given, with some mention of difficulties experienced, and how these were overcome. Full circuit diagrams of electronic apparatus, and illustrative photographs, are supplied. Chapter III. The development of theories of the origin and propagation of solar noise radiation is historically reviewed and the success of each theory in explaining or predicting observed phenomena, is assessed. A working model is chosen from among these theories, and reasons for its adoption are given. Chapter IV. Observations made by the author of solar radiation at a frequency of 300 Mc/s are described, together with a description of the objects and methods, of analysis of the records. Chapter V. Phenomena observed by the author are compared with those observed by other workers. It is concluded that storm bursts are caused by transients similar to those producing Type II and Type ITI bursts, and a model for the production of storm bursts is tentatively suggested. Chapter VI. Suggestions for further research, including suggestions for methods of testing the author's conclusions, are made.

Atmospheric aerosols are suspensions of solid and/or liquid particles in the air from natural and anthropogenic sources. Aerosols are ubiquitous in the air and are often observable as dust, smoke and haze. Dust is considered to be one of the major components of tropospheric aerosols over the globe. Natural and human processes contribute to aerosol emissions. Each year, several billion tons of soil-dust is entrained into the atmosphere playing a vital role in solar irradiance attenuation, and affects marine environments, atmospheric dynamics and weather. Air pollution has recently become a serious environmental problem. Over recent years in the public health domain particulate matter (PM) concentration has become a topic of considerable importance, since epidemiological studies have shown that exposure to particulates with aerodynamic diameters of < 10 ìm (PM10) and especially < 2.5 ìm (PM2.5) induces an increase of lung cancer, morbidity and cardiopulmonary mortality. Mineral dust plays an important role in the optical, physical and chemical processes in the atmosphere, while dust deposition adds exogenous mineral and organic material to terrestrial surfaces, having a significant impact on the Earth’s ecosystems and biogeochemical cycles. The role of dust aerosols in atmospheric processes, i.e. Earth’s radiation balance, cloud microphysics, etc, strongly depends on a variety of physico-chemical parameters, size distribution, dust sources, atmospheric lifetime and mixing processes in the atmosphere. Analysis of the physical properties and chemical composition of dust aerosols is important to determine aerosol sources, mixing processes, transport pathways and their effects on human health. Atmospheric aerosols affect the global climatic system in many ways, i.e. by attenuating the solar radiation reaching the ground, modifying the solar spectrum, re-distributing the earth-atmosphere energy budget and influencing cloud microphysics and the hydrological cycle. Satellite remote for sensing provides an important observational means for monitoring dust production and for improving the understanding of the effects of regional-scale atmospheric processes on dust emission and transport. The Sistan region is located in southeastern Iran, close to the Iranian borders with Pakistan and Afghanistan. The climate is arid, with low annual average precipitation of ~55 mm occurring mainly in the winter (December to February) and evaporation exceeding ~4000 mm.year-1. During summer (June – September), the area is under the influence of a low pressure system attributed to the Indian thermal low that extends further to the west as a consequence of the south Asian monsoon system. These low pressure conditions are the trigger for the development of the Levar northerly wind, commonly known as the “120-day wind”, causing frequent dust and sand storms and contributing to the deterioration of air quality. Therefore, one of the main factors affecting the weather conditions over the region is the strong winds rendering Sistan as one of the windiest deserts in the world. Severe droughts during the past decades, especially after 1999, have caused desiccation of the Hamoun lakes which is located in the northern part of Sistan, leaving a fine layer of sediment that is easily lifted by the wind, thus modifying the basin to one of the most active sources of dust in southwest Asia. The strong winds blow fine sand off the exposed Hamoun lake beds and deposit it to form huge dunes that may cover a hundred or more villages along the former lakeshore. Hamoun dry lake beds are mainly composed of quaternary lacustrine silt and clay material as well as Holocene fluvial sand, silt and clay. These materials have been carried to the basin by the rivers, while along their courses neogene fluvial sand, eolian sand, silt and clay are the main constituents. This thesis analyses the aerosol characteristics, dust loading and air quality over the Sistan region based on first time measurements conducted. The dust loading was measured using dust traps near the Hamoun basin during the period August 2009 to July 2010. Dust loading from the Hamoun basin appears to have a significant contributing influence on the development of extreme dust storms, especially during the summer days. This influence firstly seems to depend on the intensity and duration of dust storms, and secondarily, on the distance from the source region, the wind speed and altitude. The grain-size distribution of the dust loading is strongly influenced by the distance from the dust source. Furthermore, the particle size distribution exhibited a shift towards lower values as the altitude increases, with this feature found to be more obvious amongst larger sized particles, while the frequency of particles below 2.5 ìm seemed not to be affected by altitude. In general, the analysis revealed significant spatio-temporal variability of regional dust loading and characteristics. This finding necessitates more systematic observations at as many locations as possible around the Hamoun basin in order to improve the understanding of force dynamics, transport mechanisms as well as to quantify the dust amounts emitted from the Hamoun basin. To assess air quality characteristics in two cities of Zabol and Zahedan affected by the Sistan dust storms, systematic airborne PM concentrations were measured during the period September 2010 to September 2011 and July 2008 to March 2010, respectively. The results showed that the PM10 concentrations were considerably higher than the corresponding European Union air quality annual standard and the mean PM2.5 concentration (32 ìgm-3) also overcame the Air Quality Index (AQI) annual PM2.5 standards. This poor air quality is affected by dust storms from the Sistan desert. The drainage of the Hamoun wetlands, in association with the intense Levar winds in summer, is the main factor responsible for the frequent and massive dust storms over the Sistan region. Hamoun, as an intense dust source region, caused a dramatic increase in PM10 concentrations and a deterioration of air quality (65% of the days were considered unhealthy for sensitive people and 34.9% as hazardous) in Zabol city. The maximum PM10 concentrations occurred between 8:00 to 11:00 Local Sidereal Time (LST) in Zabol and between 12:00 and 20:00 LST in Zahedan, indicating that Sistan dust storms reach Zahedan after six to nine hours. The strong correlation between daily PM2.5 and PM10 concentrations indicated that they have similar sources and an increase of PM10 significantly affects PM2.5. Considering the air pollution standards defined by the United state Environmental Protection Agency (USEPA), determining that only on one day per year may the AQI be higher than 100 ìg.m-3, it was found that the values of AQI in Zahedan overcame this level for 86 days out of 399, expressing a fraction of 21.5%. It should be noted that on 25 days (6.3%) the atmospheric conditions were very unhealthy or hazardous for the whole population and this requires more attention by officials, managers and urban planners. Windblown transport and deposition of dust is widely recognized as an important physical and chemical concern to climate, human health and ecosystems. To mitigate the impact of these phenomena, this thesis examines for the first time, the mineralogical and chemical properties of dust over Sistan by collecting aerosol and soil samples. These data were analyzed to investigate the chemical and mineralogical characteristics of dust, relevance of inferred sources and contributions to air pollution. Dust aerosol characterization included chemical analysis of major and trace elements by X-Ray Fluorescence (XRF) and mineral analysis by X-Ray Diffraction (XRD). The results showed that quartz, calcite, muscovite, plagioclase and chlorite are the main mineralogical components of the dust, in descending order, over Sistan, and were present in all the selected airborne dust samples. In contrast, significantly lower percentages for enstatite, halite, dolomite, microcline, gypsum, diopside, orthoclase and hornblende were found, since these elements occurred only in some of the samples. On the other hand, silicone dioxide (SiO2), Calcium oxide (CaO), Aluminum oxide (Al2O3), Sodium oxide (Na2O), Magnesium Oxide (MgO) and Iron (III) Oxide (Fe2O3) were the major elements characterising the dust, while large amounts of Fluorine (F), Chlorine (Cl) and Sulfur (S) were also found as trace elements. The mineralogy and chemical composition of airborne dust at both stations were nearly the same and quite similar to the soil samples collected at several locations downwind. This suggests that the dust over Sistan is locally emitted, i.e. from the Hamoun basin, and in a few cases can also be long-range transported to distant regions. On the other hand, individual dust storms showed significant differences between either evaporite-dominated aerosols or those characterized by deflation from alluvial silts. These possibly reflect either localized climatic cyclicity or desiccation cycles. However, in some cases the soil samples showed poor comparisons with aerosol compositions, suggesting that dynamic sorting, soil-forming processes and climatic influences, such as rainfall, altered the mineralogy and chemistry in these partially eolian deposits. Estimates of Enrichment Factors (EF) for all studied elements show that all of them have very low EF values, suggesting natural origin from local materials. The results suggest that a common dust source region can be inferred, which is the eroded sedimentary environment in the extensive Hamoun dry lakes. Scanning Electronic Microscope (SEM) analyses of the samples indicated that airborne dust has rounded irregular, prismatic and rhombic shapes, with only the finer particles and a few cases of the coarser dust being spherical. This thesis analyses the aerosol patterns over the arid environment of Sistan region by means of multiple satellite platforms aiming to reveal the spatio-temporal and vertical distribution of dust aerosols. The dataset used includes records of Aerosol Index (AI) from the Total Ozone Mapping Spectrometer (TOMS) on board the Nimbus-7 (1979–92) and the Earth Probe (mid-1996 to 2001) satellites and six-year AI records from OMI aboard Aura. Moreover, the Aerosol Optical Depth (AOD) is analyzed through 11-year records from Multi-angle Imaging Spectro Radiometer (MISR) aboard Terra (2000-2010) and from seven-year Deep Blue records from MODIS aboard Aqua (2002-2011). The main focus is to determine similarities and differences in dust climatology provided by these sensors over the Sistan region and surroundings. The results showed a marked seasonal cycle with high aerosol loading during summer and lower in winter, while MISR, MODIS Deep Blue and OMI climatologies agree in both terms of monthly and seasonally mean spatial and temporal aerosol patterns revealing similar seasonal behavior over the region. After prolonged drought conditions in 1999 at Hamoun lakes (northern of Sistan) the dust-aerosol load over the area has increased. The higher aerosol concentrations during summer are interpreted as a result of the Levar northerly winds and the drying of Hamoun lakes. The satellite monitoring highlights Sistan and Hamoun basin as major dust source regions in south Asia, spreading dust aerosols over Afghanistan, Pakistan and Arabian Sea. / Thesis (PhD)--University of Pretoria, 2012. / Geography, Geoinformatics and Meteorology / Unrestricted

Since the earliest published American narratives, writers and subsequent Western clinicians alike have often mislabeled Indigenous behaviors, especially the behaviors of Indigenous women, as insanity. And yet, as Pemina Yellow Bird (Three Affiliated Tribes) explains, "Native peoples generally do not have a notion of "insane" or "mentally ill." (4). Instead, Indigenous peoples often discuss mental health in their communities through storytelling. As but one example of the ways that cultural narratives work to reclaim Indigenous understandings of mental health, this paper analyzes how the writings of Chickasaw author Linda Hogan challenge non-Indigenous understandings of mental health as a gendered phenomenon within tribal communities. Hogan does this in ways that destigmatize behaviors including hallucinations or prophetic dreams that Western medicine considers abnormal, and reintroduces community-specific understandings of these behaviors as either a supernatural phenomenon or a gift of foreknowledge. Hogan's novel Solar Storms (1995), in particular, reframes stereotypical images of tribal women as insane with images of Indigenous women as cultural, political, and spiritual leaders in their communities. While she addresses community-specific understandings of actual mental illness, Hogan also characterizes what many might mistake for mental illness as the essential foresight of Indigenous women and thereby offers a healing corrective to the prevailing narrative of Indigenous women's presumed insanity. A central discussion in this paper is how Hogan defines knowledge-making and Indigenous women's rights and responsibilities in Solar Storms. The term "rights and responsibilities" refers to a sense of stewardship Indigenous women in the novel experience to protect land and community: this charge may include giving life through childbirth, communicating with animals and the dead, dreaming of medicinal plants, intuitively remembering traditional song and dance, "seeing" creatures without one's eyesight, and healing abilities, among others. Female knowledge-making, then, refers to insights about oneself, community, and the material and immaterial world in enacting these behaviors. By expressing the possibilities of Indigenous women's relationship with the natural and supernatural world instead of either exoticizing or dismissing them, Solar Storms works to legitimize Indigenous modes of female knowledge-making in the face of ongoing colonial assumptions about Indigenous insanity.

Storms have been impacting coastal morphodynamics directly due to its intensifying effects over the years. Climate change has caused an exponential impact on storms and therefore morphodynamic changes in the coasts. A specific land that has constantly been threatened is Dauphin Island, a barrier island in Alabama. Over time, it has experienced a total land loss of 100 ft of shoreline over the past of 3 decades and an overall 16% land loss of the island due to the intensifying effects of storms due to a changing climate. In this study, we use Hurricane Ivan as an example. In order to analyze the effects of a future scenario we incorporate the effects of sea level rise. Therefore, we compare three different scenarios of Hurricane Ivan including its current scenario in 2004, current scenario with sea level and future scenario with sea level. Increases in storm surge include wind speed, minimum central pressure and translation speed. These are all factors affecting the breaching in the barrier island. We aim to show how climate change can intensify the effects of hurricanes and impact coastal erosion by comparing a future climate with current climate. We use Hurricane Ivan in Dauphin Island as a case study.

A study of large solar storms in the equinox periods of solar cycles 23 and 24 is presented to quantify their effects on the total electron content (TEC) in the ionosphere. We study the dependence of TEC over the contiguous US on various storm parameters, including the onset time of the storm, the duration of the storm, its intensity, and the rate of change of the ring current response. These parameters are inferred autonomously and compared to TEC values obtained from the CORS network of GPS stations. To quantify the effects we examine the difference between the storm-time TEC value and an average from 5 quiet days during the same month. These values are studied over a grid with 1 deg x 1 deg spatial resolution in latitude and longitude over the US sector. Correlations between storm parameters and the quantified delta TEC values are studied using machine learning techniques to identify the most important controlling variables. The weights inferred by the algorithm for each input variable show their importance to the resultant TEC change. The results of this work are compared to recent TEC studies to investigate the effects of large storms on the distribution of ionospheric density over large spatial and temporal scales. / MS / This study analyzes the impact of geomagnetic storms on the electrical properties of the upper atmosphere at altitudes where satellites routinely fly. The storms are caused by bursts of charged particles from the sun entering the Earth’s atmosphere at high latitudes, leading to phenomena like the aurora. These fluctuations in the atmospheric electrical properties can potentially have serious consequences for the electrical power grid, the communications infrastructure, and various technological systems. Given the risks solar storms can pose, it is important to predict how strong the impact of a given storm is likely to be. The current study applies machine learning techniques to model one particular parameter that relates to the electrified atmosphere over the contiguous US sector. We quantify the strength of the fluctuations as a function of various storm parameters, including onset time and duration. This enables us to autonomously infer which storm parameters have the most significant influence on the resultant atmospheric changes, and compare our results to other recent studies.

This thesis presents an analysis of the internal structure of storm systems passing through Blacksburg, Virginia, between November 1985 and October 1986. An S-band dual polarized radar located at the Virginia Tech Satellite Tracking Station scanned two different sites and collected atmospheric backscattering information. This information was processed by computers at the ground station and converted into reflectivity (Z) and differential reflectivity (ZDR) range height indicators (RHI). The range height indicators show the two dimensional rain intensity distribution of the storms. The linear extent of storms crossing the radio path from the radar to the Intelsat V Satellite were examined. The path lengths and heights of the storms were collected and tabulated. Histograms and exceedance plots for these lengths and heights are included. The storm rain path length is also compared to the link attenuation. / Master of Science

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