Orientadores: Milton Mori, Alexandre de Paula Peres / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-04T02:14:15Z (GMT). No. of bitstreams: 1 Bernardo_Sergio_D.pdf: 16858562 bytes, checksum: 146132fc4ed6476801c980face63fe50 (MD5) Previous issue date: 2004 / Resumo: Este trabalho é fruto do esforço iniciado por pesquisadores do Laboratório de Modelagem e Simulação de Processos Químicos (FEQ-UNICAMP) visando estudar o escoamento do gás em ciclones. A premissa foi buscar a consolidação das informações já obtidas, usando como ferramenta para tal finalidade as modernas técnicas da Fluidodinâmica Computacional (CFD). O trabalho foi dividido em duas frentes: análise do escoamento monofásico (gás) e do escoamento bifásico (gás-sólido), tendo como foco o mapeamento do campo de velocidade, pressão e eficiência por meio de um modelo CFD tridimensional. O estudo foi embasado em resultados experimentais disponíveis na literatura científica, como também em experimentos numéricos desenvolvidos previamente por outros pesquisadores deste grupo de pesquisa. A busca incessante por informações que ajudem a elucidar o entendimento do complexo sistema de escoamento que ocorre no interior de um ciclone foi o marco inicial dos trabalhos do grupo. E neste trabalho apresenta-se a confirmação de informações anteriormente levantadas, como também novas perspectivas para a melhor compreensão do mecanismo de operação de um ciclone. As malhas numéricas tridimensionais foram geradas utilizando os pré-processadores Gambit e ICEM CFD HEXA e a partir daí os trabalhos foram desenvolvidos através de experimentos numéricos usando os pacotes computacionais em CFD: FLUENT (versão 6.0) e CFX (versões 5.5.1, 5.6 e 5.7) que fazem uso do método dos volumes finitos com variáveis co-localizadas (na qual todas as variáveis usam o mesmo volume de controle para realizar todas as integrações) na solução do sistema de equações de transporte, através de coordenadas generalizadas. Para adentrar no complexo campo da turbulência do escoamento, modelos de turbulência tais como RSM, LES e DES foram testados em simulações que foram capazes de extrair informações significativas a respeito do comportamento do escoamento do gás quando da presença de partículas sólidas. O trabalho abriu, ainda, uma ramificação para avaliar a influência de alterações na geometria do ciclone na fluidodinâmica de seu escoamento. Os resultados mostraram que a metodologia de trabalho empregada é adequada quanto à reprodução do comportamento fluidodinâmico dos escoamentos monofásico e bifásico em ciclones e que alterações geométricas propostas apontam para melhores resultados no processo de separação gás-sólido no equipamento / Abstract: This work is the result of the efforts of the CFD research group of the Chemical Processes Modeling and Simulation Laboratory located at FEQ-UNICAMP to study gas and gas-particle flow in a cyclone. The starting point was to consolidate previous information in cyclone flow using current CFD techniques. Two research lines were applied: the first one has studied gas flow and the second one was involved in the gas-solid flow study. These . analyses were focused on fluid dynamics parameters like tangential, axial and radial velocities profiles, pressure and coIlection efficiencies using a three-dimensional CFD model. Experimental and numerical results available in the literature were used to validate simulation data obtained in this work. Three-dimensional numerical grids were constructed using pre-processors like GAMBIT and ICEM CFD HEXA. The numerical simulations were performed using the commercial CFD codes FLUENT (v6.0) and CFX (v5.5.1, 5.6 and 5.7). These softwares make use of fmite volume method to solve transport equation system, using generalized coordinates. Turbulence models, like RSM, LES and DES were tested on simulations to extract important information about gas-solid flow profile. In addition, the influence of geometrical modifications on cyclone fluid dynamics was studied. The results showed that the methodology applied in this work is consistent to reproduce the fluid dynamic behavior of gas and gas-solid flow in a cyclone. Numerical results obtained here are in agreement with experimental results and other numerical data available in the literature. The modifications in the geometry proposed here indicate improvements in gas-solid coIlection efficiencies in the equipment. We believe that this study wiIl contribute to increase the knowledge on cyclone fluid dynamics / Doutorado / Desenvolvimento de Processos Químicos / Doutor em Engenharia Química

Thesis. 1977. M.S.--Massachusetts Institute of Technology. Dept. of Meteorology. / Microfiche copy available in Archives and Science. / Bibliography : leaves 96-97. / M.S.

A dissertation submitted to the Faculty of Science in fulfilment of the requirements for the degree Master of Science, University of the Witwatersrand, Johannesburg, 2019 / Tropical cyclones are becoming more intense and the locations at which they form and attain their lifetime maximum intensities are migrating poleward, exposing more regions to tropical cyclone impacts. This study investigated a new climatology for Southern Hemisphere tropical cyclones, aimed to update and re-examine the previous tropical cyclone climatology from the canonical works of Gray (1968, 1979). The optimal and minimum ranges of thermodynamic and dynamic climate variables during tropical cyclogenesis were determined, to define the conditions at which the majority of Southern Hemisphere tropical cyclones are generated. The change over time of tropical cyclone activity and the magnitude of the climate drivers at the 1000and 850mb levels was also examined. The sea surface temperatures of 27.5-28.5°C is observed as the optimal range at which a majority of storms undergo genesis. However, the lowest observed magnitude at which genesis was possible is 24°C. This challenges the 26.5°C threshold for genesis in the Southern Hemisphere. Based on factor analysis weightings and multivariate regression, sea surface temperature, air temperature and relative humidity also account for a relatively large amount of variability in the formation process of tropical cyclones, compared to the other climate variables examined. Over 1980-2016, an increase for Southern Hemisphere tropical cyclone maximum intensity of 2.4 m.s-1 per decade is observed. Of the climate drivers measured at the point of genesis; omega, meridional shear, sea surface temperature and solar flux display statistically significant correlations with tropical cyclone intensity. Sea surface temperature, air temperature, solar flux and vertical shear at the point of genesis for Southern Hemisphere tropical cyclones, demonstrate statistically significant increases in magnitude, while omega and relative humidity indicate a decreasing trend. The increase in thermodynamic variables and their relationship to storm intensity infers that a warming climate is capable of influencing tropical cyclone intensity. The El Niño Southern Oscillation, Indian Ocean Dipole, Southern Annular Mode and volcanic eruption events indicated a statistically significant relationship to metrics of tropical cyclone activity, mainly intensity and longitude of storm genesis. The tropical cyclone climatology established here by providing an up to date seasonality and background of Southern Hemisphere tropical cyclone activity, can assist impact and risk assessment studies in areas potentially vulnerable to tropical cyclone impacts within the Southern Hemisphere. / TL (2020)

Thesis (MEng (Civil Engineering))--University of Stellenbosch, 1999. / 100 leaves single printed pages, preliminary pages and numberd pages 1.1-9.1.Includes bibliography. List of figures, tables, symbols and acronyms. Scanned with a HP Scanjet 8250 Scanner to pdf format (OCR). / ENGLISH ABSTRACT: A tropical cyclone is a non-frontal, synoptic scale, low-pressure system over tropical or subtropical waters with organised convection and a definite cyclonic surface wind circulation. The system varies in size between a hundred and a few thousand kilometres in diameter with high winds circulating around a central low pressure. The process of bringing the lower atmospheric layers into thermodynamic equilibrium with the warm tropical waters add the energy to the atmosphere and lower the surface pressure. If favourable climatic conditions exist this leads to the formation of a warm core vortex, which can develop into a tropical cyclone. The occurrence of tropical cyclones follows seasonal variations, the tropical cyclone season for the Southwest Indian Ocean being between November and March. The occurrences peak along the Southern African East Coast between Mid-January and Mid-February. The data on the location and intensity of tropical cyclones along the Southeast Africa coastline were obtained from the Joint Typhoon Warning Centre and span the period between 1848 and 1999. The available data before 1945 consist of tropical cyclone tracks that influenced populated areas or were encountered by ships. It was assumed that a number of tropical cyclones before 1945 were not recorded and therefore data collected before 1945 were disregarded in the analysis. The development of radar in 1945 significantly improved the detection of tropical cyclones. Some of the tropical cyclone tracks recorded between 1945 and 1956 contain information about the intensity of the tropical cyclone. Since the dawn of the satellite age in the mid 1980's, the detection of tropical cyclones and intensity measurements have improved vastly. Monte Carlo simulation techniques were used to create long term data series based on the available measured data. Statistical distributions were fitted for each characteristic describing the tropical cyclone at its nearest position to the site under investigation. Tropical cyclones frequently occur along the Southern African East Coast. The region where more than one tropical cyclone per 100 years can be expected is bordered by latitudes 2.5°S to 32.5°S. The design parameters for structures in these regions should provide for the influence that a tropical cyclone will have on the site. The occurrence rate and expected maximum intensity of tropical cyclones with a 1DO-year return period vary with latitude along the Southern African East Coast. The maximum number of tropical cyclones in a 1DO-year period occurs at latitude 15°S with an expected number of tropical cyclones of 157.2 per 100 years. The maximum expected tropical cyclone intensity in a 100-year period is 143.5 knots at latitude 17.5°S. / AFRIKAANSE OPSOMMING: Tropiese siklone is nie-frontale laagdrukstelsels wat hulle ontstaan het oor tropiese en subtropiese oseane. 'n Stelsel bestaan uit 'n sentrale laagdrukstelsel met sirkulerende winde daar om. 'n Sikloon se deursnee kan wissel van 'n honderd tot 'n paar duisend kilometer. 'n Laagdrukstelsel ontstaan as gevolg van 'n termodinamiese wanbalans tussen die atmosfeer en die warm oseaanwater in die trope. Indien die benodigde atmosferiese toestande heers kan die laagdrukstelsel in 'n tropiese sikloon ontwikkel. In die Suidwestelike Indiese Oseaan vorm tropiese siklone tussen November en Maart. Die meeste siklone kom hier voor vanaf middel Januarie tot middel Februarie. Data is verkry vanaf die "Joint Typhoon Warning Centre" vir die Suidwestelike Indiese Oseaan en strek vanaf 1848 tot 1999. Die data voor 1945 verteenwoordig slegs die tropiese siklone wat bewoonde areas of skeepsvaart beinvloed het. Daar is aangeneem dat 'n betekenisvolle getal van die tropiese siklone voor 1945 nie gedokumenteer is nie en derhalwe is slegs data van sikloon voorkomste na 1945 gebruik in die studie. Vanaf 1945 het die ontwikkeling van radar die opsporing van siklone in onbewoonde areas moontlik gemaak. Die gebruik van weersatelliete vanaf die middel 1980's het die kwaliteit van die data nog verder verbeter. Monte Carlo simulasie tegnieke is gebruik om langtermyn data vir spesifieke posisies langs die kus te genereer. Statistiese verdelings is gepas op die eienskappe wat die sikloon beskryf wanneer dit die naaste posisie aan die terrein bereik. Die passing van die verdelings is gedoen op die beskikbare historiese data. Die verdelings is dan gebruik om langtermyn data stelle te skep vir die terrein. Tropiese siklone kom gereeld in die Suidwestelike Indiese Oseaan voor en beinvloed die Suid-Afrikaanse Ooskus. Meer as een tropiese sikloon kan elke 100 jaar verwag word in kusgebiede tussen breedtegrade 2.5° S en 32.5° S. Die ontwerpe vir strukture in die gebied moet dus voorsiening maak vir die invloed van tropiese siklone. Die voorkoms en intensiteit van tropiese siklone varieer met breedtegraad langs die Suid-Afrikaanse Ooskus. Die meeste siklone word verwag by breedtegraad 15°S met 'n gemiddelde van 157.2 siklone per 100 jaar. Die mees intensiewe siklone kom voor by breedtegraad 17.5°S met 'n verwagte 1:100 jaar intensiteit van 143.5 knope.

Approved for public release, distribution is unlimited / This thesis investigated the hypothesis that variations in tropical cyclone (TC) activity in the western North Pacific (WNP) may affect the teleconnection between the tropical WNP and North America. The teleconnection patterns of the 500 hPa geopotential height between a base point in the WNP (20 N 115 E) and a domain over North America (30 - 45 N, 70 -90 W) from 1951-2001 were examined. The 25 most active and the 25 least active TC years for two regions with the highest climatological average of TC activity, near the Philippines and Taiwan, respectively, were compared to determine if stronger teleconnection patterns occur during the more active years. For both regions, the correlation pattern is significant during active years and insignificant during inactive years, with the results based on TC activity in the Philippines region showing a larger difference. An analysis of 500 hPa mean winds showed weaker winds in the midlatitudes during active TC years when the teleconnection is stronger, which suggests that the teleconnection may consist mainly of Lau and Weng's (2000) zonally-elongated mode (Mode 1). Further cross correlations of the geopotential height and TC frequency parameters with the tropical eastern and western Pacific sea-surface temperatures (SST's) showed a significant correlation between TC activity and tropical eastern Pacific SST's, but the North America-WNP correlation is unlikely to be a result of a direct influence of SST's on the two regions. / Captain, United States Air Force

Extreme weather events have a large effect on society. As such, it is important to understand these events and to project how they may change in a future, warmer climate. The aim of this thesis is to develop a deeper understanding of two types of extreme weather events: subtropical floods and tropical cyclones (TCs). In the subtropics, the latitude is high enough that quasi-geostrophic dynamics are at least qualitatively relevant, while low enough that moisture may be abundant and convection strong. Extratropical extreme precipitation events are usually associated with large-scale flow disturbances, strong ascent, and large latent heat release. In the first part of this thesis, I examine the possible triggering of convection by the large-scale dynamics and investigate the coupling between the two. Specifically two examples of extreme precipitation events in the subtropics are analyzed, the 2010 and 2014 floods of India and Pakistan and the 2015 flood of Texas and Oklahoma. I invert the quasi-geostrophic omega equation to decompose the large-scale vertical motion profile to components due to synoptic forcing and diabatic heating. Additionally, I present model results from within the Column Quasi-Geostrophic framework. A single column model and cloud-revolving model are forced with the large-scale forcings (other than large-scale vertical motion) computed from the quasi-geostrophic omega equation with input data from a reanalysis data set, and the large-scale vertical motion is diagnosed interactively with the simulated convection. It is found that convection was triggered primarily by mechanically forced orographic ascent over the Himalayas during the India/Pakistan flood and by upper-level Potential Vorticity disturbances during the Texas/Oklahoma flood. Furthermore, a climate attribution analysis was conducted for the Texas/Oklahoma flood and it is found that anthropogenic climate change was responsible for a small amount of rainfall during the event but the intensity of this event may be greatly increased if it occurs in a future climate. In the second part of this thesis, I examine the ability of high-resolution global atmospheric models to simulate TCs. Specifically, I present an intercomparison of several models' ability to simulate the global characteristics of TCs in the current climate. This is a necessary first step before using these models to project future changes in TCs. Overall, the models were able to reproduce the geographic distribution of TCs reasonably well, with some of the models performing remarkably well. The intensity of TCs varied widely between the models, with some of this difference being due to model resolution.

Thesis (M.S.)--University of Hawaii at Manoa, 2006. / Includes bibliographical references (leaves 72-79). / x, 79 leaves, bound ill. (some col.) 29 cm

La vapeur d’eau convergeant vers les régions polaires se condense en nuages quiretiennent la chaleur terrestre. Ces nuages donnent lieu à des précipitations, qui adoucissent les océans polaires et épaississent les calottes de glace. Sans changement des vents, le transport de vapeur d’eau est appelé à augmenter dans un climat plus chaud et donc les chutes de neige sur les calottes aussi. Le surplus d’humidité risque cependant de rétroagir sur le réchauffement de surface.Afin de contraindre les projections futures, cette thèse se propose d’évaluer la variabilité actuelle du cycle de l’eau dans les hautes latitudes. Elle s’appuie sur sept réanalyses globales et des observations par radiosondages allant de 1979 à 2013. Leurs biais intrinsèques et les approximations de calcul n’entament pas les conclusions principales de cette étude.En Arctique, mise à part une légère surestimation, le transport d’humidité dans les réanalyses est remarquablement proche des observations, aussi bien dans le temps que dans l’espace. Dans toutes les réanalyses, les vents dominants n’advectent qu’une fraction de la vapeur d’eau, de 6 à 11%, au profit des perturbations. D’après la plupart des sources, évaporation, précipitation et humidité atmosphérique augmentent en accord avec l’élévation des températures. Toutefois, les flux de vapeur d’eau ne suivent pas la loi de Clausius-Clapeyron car humidité et vents sont moins corrélés, notamment près de la surface.En Antarctique, le manque d’observations se fait sentir : la convergence de vapeur d’eau sur la calotte varie de 117 à 156 mm par an selon les réanalyses. Le transport côtier, très variable dans l’espace, résulte de l’alternance entre vents catabatiques et passage de perturbations. Sur la côte, les radiosondages signalent une augmentation significative des flux d’humidité vers le Sud. À l’échelle du continent en revanche, les réanalyses ne font étatde quasiment aucune tendance.Enfin, le rôle des phénomènes météorologiques d’échelle courte est évalué de nouveau, selon plusieurs méthodes. En particulier, les cyclones extratropicaux laissent dans les flux de vapeur d’eau une empreinte caractéristique qui peut être détectée et quantifiée. / The water vapour converging to the polar regions condenses into heat-trappingclouds and eventually precipitates, freshening the polar oceans and thickening the ice-sheets. Modulo circulation changes, the moisture transport is expected to increase in a warmer climate. While the extra precipitation could dampen the ice sheets’ contribution to sea level rise, the surplus of moisture could also feed back on the surface warming. However, the present variability of the polar moisture budgets must be known precisely before they can be projected with confidence into the future.This study examines the atmospheric water cycle of both the Arctic and the Antarctic in seven global reanalyses and in radiosonde observations covering the 1979-2013 period. The impacts of known model and assimilation flaws and of the various numerical approximations were evaluated and proven to be limited, at least for the moisture flux variable and the more recent reanalyses.In the Arctic, aside from a slight overestimation, the northward fluxes in reanalyses exhibit a remarkable agreement with the radiosoundings in terms of spatial and temporal patterns. In all reanalyses, transient eddies provide the bulk of the mid-latitude moisture imports – 89-94% at 70◦ N. In most datasets, evaporation, precipitation and precipitable water increase in line with what is expected from a warming signal. However fluxes do not scale with the Clausius-Clapeyron relation because the increasing humidity is not correlatedwith the meridional wind, particularly near the surface.The representations of the Antarctic atmospheric water cycle in reanalyses suffer from the scarcity of observations : the moisture convergence estimations vary from 117 to 156 mm per year. On the coast, the mean moisture flux results from the interplay between transient eddies and katabatic winds, which are particularly sensitive to the orography. The coastalradiosonde sites report significant increases of the southward moisture fluxes but otherwise there are practically no trends in reanalyses on a continental scale.Finally, the share of transient eddies in moisture advection is qualified using alternate methods. In particular, extratropical cyclones leave a characteristic imprint on the transport field, which can be detected and quantified.

Tropical cyclones are among the most devastating natural disasters for human beings and the natural and manmade assets near to Atlantic basin. Estimating the current and future intensity of these powerful storms is crucial to protect life and property. Many methods and models exist for predicting the evolution of Atlantic basin cyclones, including numerical weather prediction models that simulate the dynamics of the atmosphere which require accurate measurements of the current state of the atmosphere (NHC, 2019). Often these models fail to capture dangerous aspects of storm evolution, such as rapid intensification (RI), in which a storm undergoes a steep increase in intensity over a short time. To improve prediction of these events, scientists have turned to statistical models to predict current and future intensity using readily collected satellite image data (Pradhan, 2018). However, even the current-intensity prediction models have shown limited success in generalizing to unseen data, a result we confirm in this study. Therefore, building models for the estimating the current and future intensity of hurricanes is valuable and challenging. In this study we focus on to estimating cyclone intensity using Geostationary Operational Environmental Satellite images. These images represent five spectral bands covering the visible and infrared spectrum. We have built and compared various types of deep neural models, including convolutional networks based on long short term memory models and convolutional regression models that have been trained to predict the intensity, as measured by maximum sustained wind speed. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2020. / FAU Electronic Theses and Dissertations Collection

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