O trabalho consta do estudo do meio físico geotécnico do município de Porto Alegre visando a identificação e caracterização de unidades geotécnias, formadas por associações de solos com características físico-morfológicas e origem semelhantes. As unidades geotécnicas são definidas por um estudo de escritório baseado em levantamentos geológicos, pedológicos, topográficos e geográficos e também com o auxílio de fotografias aéreas, acompanhado de uma investigação de campo com a amostragem de perfis das diferentes unidades estimadas. Uma carta com a ocorrência das unidades geotécnicas e com a representação das estruturas geológicas de maior importância geotécina é construída. Destaque é dado ás unidades geotécnicas de solos subtropicais oriundos dos granitos, gnaisses e migmatitos. E executada uma avaliação das características físicas (mineralogia, granulometria, plasticidade, e índices físicos) e propriedades geotécnicas (compressibilidade, colapsividade e resistência ao cisalhamento) dos solos dos principais horizontes de perfis típicos destas unidades. São utilizados ensaios de caracterização, análises mineralógicas de rochas por lâminas delgadas, análises mineralógicas de argilas por meio de difratograma de raio X, ensaios de compressão confinada e ensaios de cisalhamento direto. Os resultados são apresentados em função dos principais horizontes de solos das unidades geotécnicas , são eles horizontes saprolíticos, formados por solo residual que ainda apresentam minerais primários e vestígios estruturais da rocha de origem e horizontes superficiais muitas das vezes laterizados. A análise foi feita à luz dos processos de formação e dos decorrentes fatores que determinam o comportamento geotécnico destes solos de intemperismo subtropical. / A study of the geotechnical environment of Porto Alegre county, by means of identification and characterization of geotechnical units, is here presented. These units consist of group of soils with similar origin, physical and morphological characteristics. The geotechnical units were defined based in geological, podological, topographic and geographic surveys as wel as in aerophotos. Field investigation, with sampling of profiles of different estimated unitis, was concomitantly perfomed. A map with the geotechnical units and main geological structures was elaborated. Geotechnical units of soils originated from granite, gneiss and migmatit were particulary studied. Physical characteristics (mineralogy, grain size distribution, plasticity and physical indexes) and geotechnical properties (compressibility, collapsibility and shear strenght) of soils of main horizons from theses units were evaluated. Characterization tests, rocks mineralogical analysis by means of X-rays diffraction, confined compression and directed shear tests were perfomed. Tests results were related to main horizons are saprolitc (hor.C), composed of residual soil, and surface horizon (hor.B), frequentely laterized. The results were analyzed regarding factors wich influence the geotechnical behavior of these subtropical soils.

Oxamniquine, 6-hydroxymethyl-2-N-isopropylaminomethyl-7-nitro-1,2,3,4- tetrahydroquinoline, is a potent schistosomicide used clinically in the treatment of infections due to Schistosoma mansoni. Schistosomiasis is the second most important tropical disease after malaria. Although oxamniquine is relatively well tolerated, severe central nervous system (CNS) effects characterized by convulsions, have been reported in a small percentage of the population treated with this drug.

HURDAT is the main historical archive of all tropical storms and hurricanes in the North Atlantic Basin, which includes the Caribbean Sea and Gulf of Mexico, from 1851 to the present. HURDAT is maintained and updated annually by the National Hurricane Center at Miami, Florida. Today, HURDAT is widely used by research scientists, operational hurricane forecasters, insurance companies, emergency managers and others. HURDAT contains both systematic biases and random errors. Thus, the reanalysis of HURDAT is vital. For this thesis, HURDAT is reanalyzed for the period of 1954-1963. The track and intensity of each existing tropical cyclone in HURDAT is assessed in the light of 21st century understanding and previously unrecognized tropical cyclones are detected and analyzed. The resulting changes will be recommended to the National Hurricane Center Best Track Change Committee for inclusion in HURDAT.

No description available.

Paleotempestology, the study of past tropical cyclones (TCs) using geological proxy techniques, is a growing discipline that utilizes data from a broad range of sources. Most paleotempestological studies have been conducted using “established proxies”, such as grain-size analysis, loss-on-ignition, and micropaleontological indicators. More recently researchers have been applying more advanced geochemical analyses, such as X-ray fluorescence (XRF) core scanning and stable isotopic geochemistry to generate new paleotempestological records. This is presented as a four article-type thesis that investigates how changing climate conditions have impacted the frequency and paths of tropical cyclones in the western North Atlantic basin on different spatial and temporal scales. The first article (Chapter 2; Oliva et al., 2017, Prog Phys Geog) provides an in-depth and up-to-date literature review of the current state of paleotempestological studies in the western North Atlantic basin. The assumptions, strengths and limitations of paleotempestological studies are discussed. Moreover, this article discusses innovative venues for paleotempestological research that will lead to a better understanding of TC dynamics under future climate change scenarios. The second article (Chapter 3; Oliva et al., submitted, The Holocene) presents the development of the first database summarizing the most up-to-date paleotempestological proxy data available for TC reconstructions for the western North Atlantic basin. Subsets of this new database are then used to reconstruct TC variability in the western North Atlantic basin. Using our new developed subsets, we investigate a key hypothesis, the Bermuda High Hypothesis that has been proposed to have influenced TC paths over centennial to millennial timescales. Results show an oscillation in the distribution of TC landfalls along the North American coast, suggesting a centennial oscillation in the mean summer position of the high pressure system. We suggest that a more serious, millennial scale shift in the Bermuda High to a northeastern (NE position) may have occurred at ~3000 and ~1000 cal yr BP. The third article (Chapter 4; Oliva et al., under review, Marine Geology) presents a local multi-proxy reconstruction of TC activity during the past 800 years from Robinson Lake, Chezzetcook Inlet in Nova Scotia, Canada. Here, we are testing the more recent use of the XRF scanning approach to paleotempestology at a local scale. Two sediment cores were extracted from Robinson Lake that were dated by 210Pb and 14C, analyzed for organic matter content, benthic foraminifera and thecamoebians, sediment grain size, and a range of elements and elemental ratios determined by XRF core scanning. Results show two periods of low TC activity based on multiple proxies including XRF technology: one from ~1150 to 1475 CE (800 – 475 cal yr BP) and the other from 1670 CE (280 cal yr BP) to the present, with the intervening period from ~1475 to 1670 CE (475 – 280 cal yr BP) as a time of more frequent and possibly higher magnitude TC activity. The fourth article (Chapter 5. Oliva et al., in preparation, Canadian Journal of Earth Sciences) explores the potential use of stable oxygen isotopes in tree ring α-cellulose to reconstruct past local TC activity surrounding areas of known TC strikes. Cores of 12 Picea mariana trees were extracted adjacent to Robinson Lake, Chezzetcook Inlet, Nova Scotia in order to test more contemporary and historically documented records of TC activity in this region as per Chapter 4. TCs precipitate 18O-depleted rain, leaving a unique signature in the source water that trees use to form cellulose. Using an autoregressive integrated moving average (ARIMA AR-1) model to detrend the data, local and regional time series were reconstructed. Local reconstructions led to most (> 95%) hurricanes and all major hurricane (± 1 year) being recorded in the isotope record, whereas the regional reconstruction shows no major hurricane, only a few hurricanes (< 40%) and one signal with a higher error (> 1 year). This thesis contributes to advancing our knowledge in paleotempestology of the western North Atlantic basin by: 1) bringing an up-to-date current status on paleotempestology, 2) the development and ongoing use of a new paleotempestology database for the western North Atlantic basin publicly available, 3) a local scale study using new XRF core elemental technology and 4) the exploratory use of tree-ring α-cellulose oxygen isotopic analysis based on contemporary and historical documents at local sites.

specialcollections@tulane.edu / 1 / Diego Schubb

The Atlantic hurricane of May 1951 had several interesting characteristics. Chief among these were the high latitude and early season of its origin, the type of air mass in which it formed, its formation in a cold core low that extended high than the 200-mb level, and the loop in its path. There was not available enough observational data within and near the storm in order to make a detailed study sufficient to completely explain these phenomena. Some of the meteorological conditions observed shortly proceeding and during the existence of this storm were studied and are described here. Its formation and movement is analyzed and discussed in relation to various theories on the origin and movement of hurricanes. / Typescript. / "Submitted to the Graduate Council of Florida State University in partial fulfillment of the requirements for the degree of Master of Science." / "August, 1952." / Includes bibliographical references (leaves 15-16).

Studies have shown that urban areas enhance mesoscale precipitation but have not revealed if urban areas have the same effect on synoptic scale precipitation. This study used Multi-Precipitation Estimator (MPE) and Next-Generation Weather Radar (NEXRAD) stage III data to examine the effect of urban areas on rainfall associated with hurricanes and tropical storms from 1976–2005. These urban areas were divided into upwind and downwind areas where 6-hour precipitation totals were calculated and compared. Results displayed that 69.2% of urban areas had greater rainfall in the upwind area. Statistical analyses revealed that there is a larger range of higher precipitation values in the upwind area and a smaller range of lower precipitation values in the downwind area. Therefore, instead of urban areas enhancing tropical rainfall it weakens the rainfall. Based on the results, there is no relationship between urban areas and enhanced rainfall; however, there is a relationship between the distribution of precipitation and urban areas.

No description available.

Tropical cyclones (TCs) are destructive, natural occurring phenomena that can cause the loss of lives, extensive structural damage, and negative economic impacts. A major hazard associated with these tropical systems is rainfall, which can result in flood conditions, contributing to the death and destruction. The role rainfall plays in the severity of the TC aftermath emphasizes the importance for models to produce reliable precipitation forecasts. Hurricane model precipitation forecasts can be improved through precipitation verification as the model weaknesses are identified. In this study, the Hurricane Analysis and Forecast System (HAFS), an experimental NOAA hurricane model, is evaluated for its skillfulness in forecasting TC precipitation. An object-based verification method is used as it is demonstrated to more accurately represent the model skill compared to traditional point-based verification methods. A 600 km search radius is implemented to capture the TC rainfall and the objects are defined by 2, 5, and 10 mm/hr rain rate thresholds. The 2 mm/hr threshold is chosen to predominantly represent stratiform precipitation, and the 5 and 10 mm/hr thresholds are used as approximate thresholds between stratiform and convective precipitation. Shape metrics such as area, closure, dispersion, and fragmentation, are calculated for the forecast and observed objects and compared using a Mann Whitney U test. The evaluation showed that model precipitation characteristics were consistent with storms that are too intense due to forecast precipitation being too central and enclosed around the TC center at the 2 mm/hr threshold, and too cohesive at the 10 mm/hr threshold. Changes in the model skill with lead time were also investigated. The model spin-up negatively impacted the model skill up to six hours at the 2 mm/hr threshold and up to three hours at the 5 mm/hr threshold, and the skill was not affected by the spin-up at the 10 mm/hr threshold. This indicates that the model took longer to realistically depict stratiform precipitation compared to convective precipitation. The model skill also worsened after 48 hours at the 2 and 10 mm/hr thresholds when the precipitation tended to be too cohesive. Future work will apply the object-based verification method to evaluate the TC precipitation forecasts of the Basin-Scale Hurricane Weather Research and Forecasting (HWRF-B) model. / Master of Science / Tropical cyclone (TC) precipitation can impose serious threats, such as flood conditions, which can result in death and severe damage. Due to these negative consequences associated with TC rainfall, it is important for affected populations to be sufficiently prepared once these TCs make landfall. Hurricane models play a large role in the preparations that are made as they predict the location and intensity of TC rainfall, which influences the peoples' choices in taking precautionary measures. Therefore, hurricane models need to be accurate, and comparing the forecast precipitation to the observed precipitation allows for areas in which the model performs poorly to be identified. Model developers can then be informed of the areas that need to be improved. In this study, the precipitation forecasts from the Hurricane Analysis and Forecast System (HAFS) model, a hurricane model that is currently under development, are evaluated. The shape and size of the forecast and observed precipitation are quantified for light, moderate, and heavy precipitation using metrics such as area, perimeter, and elongation. The values of these metrics for the forecast and observed precipitation are compared using a statistical test. The results show that the hurricane model tended to forecast storms that are too weak due to forecast precipitation being too close to the TC center, too wrapped around the TC center, and too connected. The hurricane model is also evaluated for the accuracy of its forecasts with time from model initialization. The model had a harder time representing lighter precipitation than heavier precipitation during the first 6 hours after initialization. A decrease in the accuracy of the model forecasts was also shown 48 hours after initialization due to the general degradation of model accuracy with time after initialization. Future work will evaluate the TC precipitation forecasts of another hurricane model, the Basin-Scale Hurricane Weather Research and Forecasting (HWRF-B) model.