Tropical cyclones (TCs) often change intensity as they move over mesoscale oceanic features, as a function of the oceanic mixed layer (OML) thermal response (cooling) to the storm's wind stress. For example, observational evidence indicates that TCs in the Gulf of Mexico rapidly weaken over cyclonic cold core eddies (CCEs) where the cooling response is enhanced, and they rapidly intensify over anticyclonic warm features such as the Loop Current (LC) and Warm Core Eddies (WCEs) where OML cooling is reduced. Understanding this contrasting thermal response has important implications for oceanic feedback to TCs' intensity in forecasting models. Based on numerical experimentation and data acquired during hurricanes Katrina and Rita, this dissertation delineates the contrasting velocity and thermal response to TCs in mesoscale oceanic eddies. Observational evidence and model results indicate that, during the forced stage, the wind-driven horizontal current divergence under the storm's eye is affected by the underlying geostrophic circulation. Upwelling (downwelling) regimes develop when the wind stress vector is with (against) the geostrophic OML velocity vector. During the relaxation stage, background geostrophic circulations modulate vertical dispersion of OML near-inertial energy. The near-inertial velocity response is subsequently shifted toward more sub-inertial frequencies inside WCEs, where rapid vertical dispersion prevents accumulation of kinetic energy in the OML that reduces vertical shears and layer cooling. By contrast, near-inertial oscillations are vertically trapped in OMLs inside CCEs that increases vertical shears and entrainment. Estimates of downward vertical radiation of near-inertial wave energies were significantly stronger in the LC bulge (12.1X10 super -2 W m super -2) compared to that in CCEs (1.8X10 super -2 W m super -2). The rotational and translation properties of the geostrophic eddies have an important impact on the internal wave wake produced by TCs. More near-inertial kinetic energy is horizontally trapped in more rapidly rotating eddies. This response enhances vertical shear development and mixing. Moreover, the upper ocean temperature anomaly and near-inertial oscillations induced by TCs are transported by the westward-propagating geostrophic eddies. From a broader perspective, coupled models must capture oceanic features to reproduce the differentiated TC-induced OML cooling to improve intensity forecasting.

Made available in DSpace on 2015-03-03T15:07:34Z (GMT). No. of bitstreams: 1 AndreFOAD_DISSERT.pdf: 2002320 bytes, checksum: 0ebf2e7fb75a8ce59284dc72a43ef7ba (MD5) Previous issue date: 2012-05-18 / The separation methods are reduced applications as a result of the operational costs, the low output and the long time to separate the uids. But, these treatment methods are important because of the need for extraction of unwanted contaminants in the oil production. The water and the concentration of oil in water should be minimal (around 40 to 20 ppm) in order to take it to the sea. Because of the need of primary treatment, the objective of this project is to study and implement algorithms for identification of polynomial NARX (Nonlinear Auto-Regressive with Exogenous Input) models in closed loop, implement a structural identification, and compare strategies using PI control and updated on-line NARX predictive models on a combination of three-phase separator in series with three hydro cyclones batteries. The main goal of this project is to: obtain an optimized process of phase separation that will regulate the system, even in the presence of oil gushes; Show that it is possible to get optimized tunings for controllers analyzing the mesh as a whole, and evaluate and compare the strategies of PI and predictive control applied to the process. To accomplish these goals a simulator was used to represent the three phase separator and hydro cyclones. Algorithms were developed for system identification (NARX) using RLS(Recursive Least Square), along with methods for structure models detection. Predictive Control Algorithms were also implemented with NARX model updated on-line, and optimization algorithms using PSO (Particle Swarm Optimization). This project ends with a comparison of results obtained from the use of PI and predictive controllers (both with optimal state through the algorithm of cloud particles) in the simulated system. Thus, concluding that the performed optimizations make the system less sensitive to external perturbations and when optimized, the two controllers show similar results with the assessment of predictive control somewhat less sensitive to disturbances / Os m?todos de separa??o de ?leo e ?gua possuem, em sua maioria, aplica??es reduzidas devido ao custo operacional, a baixa efici?ncia de separa??o e ao alto tempo de processamento da separa??o. Por?m, Esses m?todos de tratamento s?o importantes devido a necessidade de extra??o dos contaminantes mais indesejados no processo de produ??o do petr?leo, a ?gua, e ao mesmo tempo, a concentra??o de ?leo na ?gua deve ser m?nima (da ordem de 40 a 20ppm) para o descarte regular da fase aquosa ao mar. A partir dessa necessidade de tratamento prim?rio objetiva-se, neste trabalho, estudar e implementar algoritmos de identifica??o para modelos polinomiais NARX em malha fechada, detectando a estrutura dos modelos, e comparar estrat?gias de controle PI e preditivo utilizando os modelos NARX (Nonlinear Auto-Regressive with Exogenous Input) atualizados online em uma combina??o de separador trif?sico em s?rie com tr?s baterias de hidrociclones. Os objetivos principais deste trabalho s?o obter um processo otimizado de separa??o trif?sica que regule o sistema, mesmo na presen?a de golfadas; mostrar que e poss?vel obter sintonias otimizadas para os controladores analisando a malha como um todo; e, avaliar e comparar as estrat?gias de controle PI e preditivo aplicadas ao processo. Para cumprir estes objetivos foi utilizado um simulador para representar o separador trif?sico e os hidrociclones, al?m de desenvolvidos algoritmos de identifica??o de sistemas (NARX) utilizando MQR (M?nimos Quadrados Recursivo), aliados a m?todos de detec??o de estrutura de modelos. Tamb?m foram implementados algoritmos de controle preditivo com modelos NARX atualizados online, e algoritmos de otimiza??o que utilizam PSO (Particle Swarm Optimization). O trabalho finaliza com a compara??o de resultados obtidos a partir da utiliza??o dos controladores PI e preditivo no sistema simulado ambos com par?metros otimizados atrav?s do algoritmo de nuvem de part?culas, e concluindo que as otimiza??es realizadas tornam o regulat?rio menos sens?vel a perturba??es externas (golfadas) e quando otimizados os dois controladores apresentam resultados similares, sendo os resultados do preditivo um pouco menos sens?vel as perturba??es

Neste trabalho foi investigado o impacto da evolução dos eventos El Niño (EN) de acordo com as fases distintas da Oscilação Decadal do Pacífico (positiva, ODP(+) e negativa, ODP(-)) nas mudanças no transporte de umidade sobre o Sudeste da América do Sul (SEAS) durante o verão austral de 1950-1999. A resposta da variabilidade do Jato de Baixos Níveis a leste do Andes (JBN) e de algumas propriedades dos ciclones extratropicais sobre o cone sul do continente as modificações na circulação associadas aos eventos mencionados acima foi analisada. Foi mostrado que existem poucas mudanças significativas no regime de precipitação sobre a América do Sul ao se considerar a influência dos anos neutros do Pacífico Equatorial durante a ODP(+) quando comparado com os anos da ODP(- ). Entretanto, os eventos EN da ODP(+) indicam diferenças no padrão de anômalo de ondas em altos níveis em resposta as diferentes anomalias de Temperatura de Superfície do Mar (TSM) dos oceanos Pacífico e Atlântico Equatorial quando comparado com os eventos da ODP(-). Como conseqüência foram observadas anomalias positivas de precipitação no SEAS associadas à intensificação do fluxo convergente de umidade em baixos níveis oriundo do Atlântico Equatorial e região Amazônica para esta região durante os eventos EN da ODP(+). Todavia, os eventos da ODP(-) apresentaram anomalias positivas de precipitação apenas ao sul do SEAS e negativas ao norte desta como resposta ao movimento descendente e divergência anômala sobre o centro-leste do Brasil seguido de enfraquecimento do fluxo de umidade transportado pelos ventos alísios em direção aos subtrópicos. Os experimentos numéricos com Community Atmosphere Model versão 3.0 serviram para ajudar na interpretação das análises observacionais onde foi sugerido que o fenômeno EN é mais importante para forçar as anomalias climáticas de verão do continente do que o modo de ODP. A maior freqüência de casos de JBN detectados com o critério 1 de Bonner durante anos de EN da ODP(+) em relação a ODP(-) foi proporcional à quantidade de eventos selecionados em cada categoria. Em geral, os casos de JBN anômalo se deslocaram desde a Amazônia até o Sul do Brasil e Nordeste da Argentina, mas foi na ODP(-) que o sistema foi mais intenso apesar de apresentar menor potencial para o transporte de umidade para o SEAS quando comparado com os casos da ODP(+). Através do esquema numérico de Murray e Simmonds foi observado que, coerentemente com a intensificação do fluxo convergente de ar quente e úmido dos trópicos para o SEAS, os eventos EN da ODP(+) apresentaram ciclones extratropicais mais freqüentes e com pressões centrais mais baixas sobre o extremo Sul do Brasil, Uruguai, Nordeste da Argentina e vizinhanças do Atlântico Sudoeste em comparação com os eventos da ODP(-). / This work investigates the impact of the El Niño (EN) events and their evolution according to the PDO phases (warm, PDO(+) and cold, PDO(-)) focusing on the moisture transport exchanges from the north to the Southeast of the South America (SESA) during the austral summer period of 1950-1999. The variability of the Low Level Jet east of the Andes (LLJ) and some properties of extratropical cyclones over the southern cone of the continent in response to the modifications in the atmosphere circulation due to above mentioned events is analyzed. It is shown that on the South America continent there are not any significant changes in precipitation distribution during the neutral years in the Equatorial Pacific for PDO(+) when compared to the years of PDO(-). However, the EN events during PDO(+) indicate some differences in the anomalous wave pattern at high levels due to the variability of the Sea Surface Temperature (SST) anomalies on the Equatorial Pacific and Atlantic oceans when compared with the events for PDO(-). This implies in positive precipitation anomalies over the SESA which is associated to the enhancement of convergent moisture flux in this region. However, the events for PDO(-) showed positive precipitation anomalies only over the southern part of the SEAS and negative to the north which is associated to the downward motion and anomalous divergence over the centraleastern Brazil. This pattern may have contributed for weakening the moisture flux transported by the trade winds towards the subtropics. Numerical experiments with the Community Atmosphere Model version 3.0 also helped on the interpretation of the observational analysis where was suggested that EN events are more important to force the climate anomalies in the summer season over the continent than the PDO mode. The frequency of LLJ cases detected with the Bonner criterion 1 during the years of EN for PDO(+) is bigger than for PDO(-). The spatial position pattern for both categories of the anomalous LLJ is from the Amazon to Southern Brazil and Northeastern Argentina. During the PDO(-) the jet is more intense, however it seems to transport less moisture towards the SEAS region when compared to the PDO(+) cases. The extratropical cyclones tracked through a numerical scheme showed higher frequency and lower central pressures on the extreme of Southern Brazil, Uruguay, Northeastern Argentina and around the Southwest Atlantic during the EN events of PDO(+) when compared to the events of PDO(-). This is in agreement with the largest flux convergence of warm and humid air from the tropics to these areas.

Au cours de cette thèse nous avons caractérisé les tourbillons quasibidimensionnels générés par convection thermique turbulente dans une demi-bullede savon. La loi de puissance en temps sur leur déplacement quadratique moyen estégalement valide pour les cyclones terrestres. Cette loi permet la prévision detrajectoire de cyclones assortie du cône de prévision comparable aux cônesexistants. Ainsi, les incertitudes de prédiction de trajectoire et les fluctuations decette trajectoire par rapport à une trajectoire moyenne sont liées. Par ailleurs, l’étudede l’intensité des tourbillons de la bulle a montré qu’ils pouvaient être décrit par unmodèle de tourbillon de type Lamb. Le suivi lagrangien de particules de fluide dans letourbillon de la bulle a permis d’en suivre des phases d’intensification et de déclin.Nous proposons une loi d’intensification commune aux tourbillons de la bulle et auxcyclones terrestres. L’influence de la rotation de la bulle sur le nombre de tourbillons,sur leur durée de vie, sur leur trajectoire et sur la loi de puissance de leurdéplacement quadratique moyen a également été étudiée. Nous nous sommes aussiintéressés à l’influence de la rotation sur les propriétés statistiques du champ defluctuations de température. Les fonctions de structures de la température semblentse raidir avec la rotation de la bulle et leurs exposants passeraient d’un régime de loide puissance en n/3 à n/2. / This thesis aims at the characterisation of quasi two dimensionalvortices stemming from turbulent thermal convection in a half soap bubble heatedfrom below. The power law in time for their mean square displacement is also validfor Earth hurricanes. This law allows simple hurricane trajectory prediction with itstrack forecast cone wich compares very well to already available cones. In this way,track prediction uncertainty and track fluctuations around a mean track are linked.The intensity of the soap bubble vortices is also studied by the mean of particleimages velocimetry and shows that their velocity field profiles are well described by aLamb type model. The Lagrangian tracking of fluid praticles in a bubble vortex allowsus to follow its intensification and decline phases. We propose an intensification lawfor both soap bubble vortices and Earth hurricanes. Rotation influence on the vorticesnumber, on their life-time, on their trajectory and on the power law of their meansquared displacement is also gauged. The statistical properties of the temperaturefield fluctuations also seem to change with rotation. The exponent of the temperaturestructure functions present a scaling transition from n/3 to n/2.

The Philippines is considered one of the most vulnerable countries in the world to climate disasters due to a combination of its geospatial, political, economic, and social attributes. The nation gets hit with an average of 20 annual tropical cyclones, also known as typhoons, and through the process of climate change, these events are only growing in both frequency and magnitude. In the coastal capital city of Metro Manila, climate change coupled with rapid and unplanned urbanization has led to increased vulnerabilities of populations, infrastructures, and increased inequalities.  This thesis aims to assess the current disaster risk reduction and management (DRRM) frameworks present within the nation and National Capital Region (NCR), through a case study approach of the 2020 typhoons: Quinta, Rolly, and Ulysses. It presents findings through four thematic pillars of disaster prevention and mitigation, preparedness, response and early- recovery, and recovery and rehabilitation. It uses the perspectives of three key informants from the Office of Civil Defense (OCD), the Philippine Disaster Resilience Foundation (PDRF), and the Asian Development Bank (ADB), as well as additional diversified perspectives.  Findings suggest that DRRM has evolved since the implementation of the Republic Act No 10121 (RA 10121), or the Philippine Disaster Reduction and Management Act of 2010, however, can still be improved to tackle root causes of vulnerabilities. I use Roberts and Pelling’s (2020) transformation as liberation model as a theoretical framework to generate recommendations to policymakers that can help address vulnerabilities to typhoons. These recommendations include increasing participation and inclusivity within policy and decision making, creating a formal mechanism to measure vulnerabilities and inform future DRRM policies, and finally to reframe climate change and disaster risks as a socio-ecological issue rather than just an environmental one. / Filippinerna anses vara ett av de mest sårbara länderna i världen för klimatkatastrofer på grund av en kombination av dess geospatiala, politiska, ekonomiska och sociala egenskaper. Nationen drabbas av i genomsnitt 20 årliga tropiska cykloner, även kända som tyfoner, och genom klimatförändringsprocessen växer dessa händelser bara i både frekvens och omfattning. I kusthuvudstaden Metro Manila har klimatförändringar i kombination med snabb och oplanerad urbanisering lett till ökad sårbarhet hos befolkningar, infrastrukturer och ökade ojämlikheter.  Denna avhandling syftar till att bedöma de nuvarande ramverken för katastrofriskminskning och -hantering (DRRM) som finns i landet och i National Capital Region (NCR), i fallet med tyfonerna 2020: Quinta, Rolly och Ulysses. Avhandlingen illustrerar resultaten genom fyra tematiska pelare: förebyggande och begränsning av katastrofer, beredskap, insatser och tidig återhämtning samt återhämtning och rehabilitering. Detta görs utifrån tre nyckelinformanters perspektiv, från Office of Civil Defense (OCD), Philippine Disaster Resilience Foundation (PDRF) och Asian Development Bank (ADB).  Resultaten tyder på att nuvarande DRRM-policyer vidmakthåller orättvisa mönster i nationen och det borde tillämpas en förändring som befrielsemodell, baserad på Roberts och Pelling (2020), för att främja en mer rättvis och hållbar hantering av tyfoner i landet. Därför rekommenderas det att DRRM-policyer ökar deltagande och inkludering inom policy- och beslutsfattande, skapa en formell mekanism för att mäta sårbarheter och informera framtida DRRM-policyer, och slutligen att omformulera klimatförändringar och katastrofrisker som socioekologiska frågor snarare än bara miljömässiga sådana.

La prévision d'intensité des cyclones tropicaux est un enjeu opérationnel majeur qui connaît encore de graves déficiences. Cette thèse vise à mieux comprendre les mécanismes d'intensification cyclonique en lien avec un thalweg d'altitude originaire des moyennes latitudes et à mettre en évidence le rôle des conditions initiales pour la prévision cyclonique. Une première étude climatologique définit un seuil objectif pour l'intensification rapide des cyclones dans le Sud-Ouest de l'océan Indien, caractérise la localisation et la fréquence des interactions cyclone-thalweg, tout en identifiant les configurations propices à l'intensification. Le cas de Dora (2007) est identifié pour simuler l'interaction grâce à un modèle numérique en assimilant les caractéristiques du cyclone dans une analyse globale. L'interaction cyclone-thalweg simulée est particulièrement complexe. Dans un premier temps, du tourbillon potentiel provenant du thalweg se superpose au coeur du cyclone en moyenne et en haute troposphère. Ensuite, un forçage dynamique induit une accélération de la circulation cyclonique tangentielle dans une région extérieure au mur de l'oeil principal, provoquant un cycle de remplacement du mur de l'oeil. Le modèle simule correctement les différentes phases d'intensification du cyclone, ce qui permet de relier l'intensification aux effets du thalweg sur le cyclone. Une deuxième étude numérique dans le Pacifique Nord-Ouest met en évidence le rôle de la structure initiale d'un cyclone sur la prévision de trajectoire et d'intensité. La prévision cyclonique future progressera en affinant la structure du coeur cyclonique spécifiée dans l'état initial de la prévision.

Approved for public release, distribution is unlimited / occurring most frequently. For the 217 large-error cases due to midlatitude influences, the most frequent error mechanisms were E-DCI (midlatitude), excessive response to vertical wind shear, excessive midlatitude cyclogenesis (E-MCG), insufficient midlatitude cyclogenesis (I-MCG), excessive midlatitude cyclolysis (E-MCL) and excessive midlatitude anticyclogenesis (E-MAG), which accounted for 68% of all large errors occurring in both NOGAPS and GFDN. Characteristics and symptoms of the erroneous forecast tracks and model fields are documented and illustrative case studies are presented. Proper identification and removal of the track forecast displaying an error mechanism could form a selective consensus that will be more accurate than a non-selective consensus. / Captain, United States Air Force

La formation des Cyclones du Cap Vert met en jeu divers processus : les thalwegs, dorsales de l'onde d'Est africaine et l'anticyclone saharien en moyenne troposphère, les thalwegs des moyennes latitudes en moyenne et haute troposphère, le flux de mousson et les alizés au large de la côte Ouest africaine en basse troposphère, les systèmes convectifs. Ces processus sont étudiés à l'aide d'une climatologie sur cinq ans d'analyses du Centre Européen de Prévision Météorologique à Moyen Terme et d'images Meteosat. Deux cas particuliers sont ensuite modélisés avec Méso-NH : celui de la perturbation qui a donné naissance à l'ouragan Helene (2006) et celui de la « Perturbation D », un cas de non-cyclogénèse observé pendant la campagne AMMA / SOP-3 à Dakar en septembre 2006. Les évolutions des perturbations simulées sont quantifiées à l'aide de bilans d'énergie et de tourbillon. Le résultat principal de cette thèse est que l'ajustement géostrophique du champ de vent à une perturbation de pression d'origine convective dans la région des Îles du Cap Vert ne se produit que lorsqu'il y a un apport d'énergie cinétique tourbillonnaire par une conversion barotrope, ainsi qu'une advection horizontale de tourbillon cyclonique. Ceci confirme l'hypothèse bien connue selon laquelle la cyclogénèse tropicale est le résultat d'une interaction entre systèmes convectifs et un environnement favorable.

L'objectiu principal d'aquesta tesi és millorar l'actual capacitat de predicció de fenòmens meteorològics de pluja intensa potencialment perillosos a la Mediterrània occidental. Es desenvolupen i verifiquen tres sistemes de predicció per conjunts (SPC) que tenen en compte incerteses presents en els models numèrics i en les condicions inicials. Per generar els SPC s'utilitza la connexió entre les estructures de vorticitat potencial (VP) i els ciclons, a més de diferents esquemes de parametrització física. Es mostra que els SPC proporcionen una predicció més hàbil que la determinista. Els SPC generats pertorbant les condicions inicials han obtingut millor puntuació en verificacions estadístiques. Els resultats d'aquesta tesi mostren la utilitat i la idoneïtat dels mètodes de predicció basats en la pertorbació d'estructures de VP de nivells alts, precursors de les situacions ciclòniques. Els resultats i estratègies presentats pretenen ser un punt de partida per a futurs estudis que facin ús d'aquests mètodes. / The main goal of this thesis is to improve the current prediction skill of potentially hazardous heavy precipitation weather events in the western Mediterranean region. We develop and test three different ensemble prediction systems (EPSs) that account for uncertainties present in both the numerical models and the initial conditions. To generate the EPSs we take advantage of the connection between potential vorticity (PV) structures and cyclones, and use different physical parameterization schemes. We obtain an improvement in forecast skill when using an EPS compared to a determinist forecast. The EPSs generated perturbing the initial conditions perform better in the statistical verification scores. The results of this Thesis show the utility and suitability of forecasting methods based on perturbing the upper-level precursor PV structures present in cyclonic situations. The results and strategies here discussed aim to be a basis for future studies making use of these methods.