To investigate the tropical Atlantic response to the remote El Nino-Southern Oscillation (ENSO) forcing, a Reduced Physics – Coupled Global Circulation Model (RP-CGCM) is developed, and four experiments are carried out. The results show that the RP-CGCM is capable of capturing the major features of Tropical Atlantic Variability (TAV) and its response to ENSO forcing. The SST response to the remote influence of ENSO may be divided into two stages. In stage one, the ENSO influences the tropical Atlantic SST primarily through the Troposphere Temperature (TT) mechanism, which predicts a uniform warming in the tropical Atlantic following the mature phase of El Nino. In the north tropical Atlantic (NTA), the Walker mechanism and the Pacific-North-American (PNA) mechanism work in concert with the TT-induced warming, giving rise to a robust SST response during the boreal spring in this region. In the south tropical Atlantic (STA), the southeasterly wind anomaly and increased stratus clouds work against the TT-induced warming, resulting in a much weaker SST response in this region. At this stage, the response can be largely explained by the ocean mixed layer response to changes in surface heat fluxes induced by ENSO. In stage two, ocean dynamics play a more active role in determining the evolution of SST. The cross-equatorial wind anomaly in the western to central equatorial Atlantic can change the SST in the eastern equatorial Atlantic through Bjerknes feedback and the SST in the central equatorial Atlantic through Ekman feedback. These feedback result in a cooling of SST in the equatorial south Atlantic (ESA) region which is so overwhelming that it cancels the warming effect induced by the TT mechanism and reverses the sign of the warm SST anomaly that is formed during stage one in this region. In general, the horizontal advection of heat plays a secondary role in the SST response to the remote influence of ENSO, except in the regions where the North Equatorial Countercurrent (NECC) dominates and the SST variability is strong. Entrainment is particularly important in maintaining the correct SST structure during boreal summer.

Le continuum sol-zone non saturée-aquifère est rarement abordé en modélisation des pesticides car il requiert des outils et une méthodologie élaborés. Ces outils peuvent avoir des niveaux de complexités variables, le plus simple étant le modèle global et le plus complexe, le modèle hydrogéologique de transport en 3 dimensions prenant en compte chacun des compartiments dans le détail. Dans ce contexte une modélisation associant de manière dynamique des outils ou des méthodes propres à chaque compartiment propose une solution intermédiaire intéressante. Une approche progressive de la modélisation hydrodynamique ainsi que de la modélisation des transferts de pesticides, appliqué au cas du bassin versant hydrogéologique de la source des Brévilles à Montreuil-sur-Epte (Val d’Oise) a pu être réalisée et fournir un modèle couplé 1D / 2D prenant en compte l’écoulement et le transport dans le sol, la zone non saturée et la zone saturée / The continuum ground-vadose zone-aquifer is rarely studied in the modeling of pesticides because it requires elaborate tools and methodology. These tools may have variable levels of complexity, the simplest being the global model and most complex, the hydrogeological model of transport in 3D taking into account each compartment in detail. In this context, a modeling associating in a dynamic way, tools or specific methods to each compartment will be an interesting intermediate solution. A progressive approach of hydrodynamic modeling and transfer modeling of pesticides applied to the case of the Brévilles spring catchment in Montreuil-sur-Epte (Val d'Oise) has been carried out and provided a coupled model 1D / 2D taking into account the flow and transport in the ground, the unsaturated zone and the saturated zone

This dissertation focused on developing an integrated surface – subsurface hydrologic simulation numerical model by programming and testing the coupling of the USGS MODFLOW-2005 Groundwater Flow Process (GWF) package (USGS, 2005) with the 2D surface water routing model: FLO-2D (O’Brien et al., 1993). The coupling included the necessary procedures to numerically integrate and verify both models as a single computational software system that will heretofore be referred to as WHIMFLO-2D (Wetlands Hydrology Integrated Model). An improved physical formulation of flow resistance through vegetation in shallow waters based on the concept of drag force was also implemented for the simulations of floodplains, while the use of the classical methods (e.g., Manning, Chezy, Darcy-Weisbach) to calculate flow resistance has been maintained for the canals and deeper waters. A preliminary demonstration exercise WHIMFLO-2D in an existing field site was developed for the Loxahatchee Impoundment Landscape Assessment (LILA), an 80 acre area, located at the Arthur R. Marshall Loxahatchee National Wild Life Refuge in Boynton Beach, Florida. After applying a number of simplifying assumptions, results have illustrated the ability of the model to simulate the hydrology of a wetland. In this illustrative case, a comparison between measured and simulated stages level showed an average error of 0.31% with a maximum error of 2.8%. Comparison of measured and simulated groundwater head levels showed an average error of 0.18% with a maximum of 2.9%.

A systematic procedure is designed to evaluate the role of stochastic forcing (SF) in El Nino ? Southern Oscillation (ENSO) exhibited by coupled ocean-atmosphere general circulation models (CGCMs). The procedure is applied on a 163-year run of a CGCM which has realistic representation of ENSO and SF. The realism of ENSO in the CGCM is determined by statistical comparison with a 29-year global reanalysis product. SF is extracted from both the CGCM and reanalysis as residual atmospheric variability uncoupled to the ocean. Further, the Madden-Julian Oscillation (MJO) and non-MJO components are isolated from SF. The CGCM stochastic components are compared to those from the reanalysis to validate their representation. A coupled ocean-atmosphere model of intermediate complexity is first forced with stochastic components from the reanalysis. The resulting ENSO is examined for realism to evaluate the strengths and weaknesses of the intermediate coupled model, which is then forced with the stochastic components from the CGCM. Results are diagnosed to investigate the role of SF. It is found that the SF can play an important role in ENSO in the CGCM, especially in its warm events. The role is similar to reanalysis SF in generating ENSO period and spring predictability barrier. However, unlike in case of the reanalysis, the seasonal dependence of ENSO variance in the CGCM does not seem to be originating from its SF. The contribution to statistics appears to be higher from the MJO component of SF compared to the non-MJO component. The intermediate model simulations also suggest that both in CGCM and nature, the SF operates on a weakly stable coupled system to produce ENSO variability.

This paper presents modifications to two widely used numerical groundwater flow models in an effort to improve upon the interaction between a well of finite length and conductivity with the surrounding formation. The first objective is to discard the common assumptions about flux- or head-based boundary conditions along the well screen by coupling pipe flow hydraulics and groundwater flow. The second objective is to avoid restricting the wellbore hydraulics to a single flow regime. Five flow regimes (laminar through rough-turbulent), based on Reynolds number and pipe roughness, are considered. The modifications are integrated into the highly versatile, well-documented and well-tested models HydroGeoSphere (finite-element/finite-difference) and USGS MODFLOW (finite-difference). Verification of the algorithm and code and is performed by comparing results to: 1) the idealized, analytical Theis solution; 2) the original, unmodified code; and 3) the results of a third party numerical solution that also accounts for variable frictional wellbore losses. Results highlight the inadequacy of either a uniform flux or a uniform head assumption along the wellbore. The solution also tends to produce much steeper hydraulic gradients in those portions of the aquifer nearest the pump intake than have previously been predicted. Systems most affected by in-well hydraulic losses include those for which well screen is long, pumping rate is large, pipe diameter is small, pipe roughness is large (either through design or aging) and aquifer conductivity is high. Improved modeling of the non-linear hydraulic conditions within the well screen can particularly influence the interpretation of wellbore flowmeter and tracer tests, leading to more precise knowledge of the variation of local aquifer hydraulic conductivity along well screens. Aquifer drawdown curves, solute transport and inflow velocities will also be influenced, which can impact capture zones and remediation costs. Given that the solution is incorporated within the HydroGeoSphere and MODFLOW models, it presents the additional advantage over existing approaches of offering a wide range of modeling capabilities, such as three-dimensional flow, arbitrary well inclination and surface-subsurface flow integration. / Thesis (Master, Civil Engineering) -- Queen's University, 2008-01-04 17:27:50.629

Orientador: Antonio Vidiella Barranco / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-08-18T11:57:02Z (GMT). No. of bitstreams: 1 Decordi_GustavoLazero_M.pdf: 2336423 bytes, checksum: d0ac4b8793e91906cabc7f57fd39f8e7 (MD5) Previous issue date: 2011 / Resumo: Nesta dissertação estudamos um modelo da interação radiação-matéria, mais conhecido como modelo Raman acoplado, consistindo de um átomo de três níveis na configuração ? (lambda) acoplado a dois modos do campo quantizado em regime de alta dessintonia átomo-campo. De início, apresentamos uma revisão dos assuntos que formam a base para o entendimento do trabalho. A partir daí, deduzimos o Hamiltoniano efetivo do modelo através do método de transformação unitária mantendo os termos de segunda ordem nas constantes de acoplamento e eliminando o nível intermediário. Na sequência, comparamos a dinâmica atômica sob duas preparações distintas: na primeira delas consideramos os dois modos em estados puros (estados coerentes), enquanto que na segunda alteramos a preparação do modo 2, mudando o estado coerente para um estado de máxima entropia (estado térmico). Finalizamos esta tese apresentando um estudo do emaranhamento na partição átomomodo 1 sob in uência do modo 2, considerado um subsistema externo. Adotando a Negatividade como principal medida de emaranhamento átomo-campo, vericamos em que circunstâncias do modelo (tempo, preparações iniciais) temos o máximo emaranhamento. / Abstract: In this work we study a model for the matter-radiation interaction, best known as Raman coupled model, which consists of an atom with three levels in the ? (lambda) conguration, coupled to two modes of the quantized field in a high atom-field detuning regime. At the beginning, we present a review of the subjects that form the background for understanding the work. After that, we deduce the Effective Hamiltonian of the model through the method of unitary transformation, keeping the terms of second order in the coupling constants and eliminating the intermediate level. In the sequence, we compare the atomic dynamics under two distinct preparations: in the first we consider the two modes as pure states (coherent states), while in the second we change the preparation in the mode 2, switching the coherent state to a state of maximum entropy (thermal state). We finish this dissertation presenting a study of the entanglement in the partition atommode 1 under the influence of the mode 2, considered as an external subsystem. Adopting the Negativity as the main measure of the atom-field entanglement, we verify in wich circumstances of the model (time, initial preparations) we achieve the maximum entanglement / Mestrado / Física Atômica e Molecular / Mestre em Física

Diverse hypotheses are behind the strength degradation in metals due to hydrogen diffusion, leading to a severe, sudden failure. These diverse hypotheses of hydrogen embrittlement include various mechanisms that are responsible for the embrittlement of metals due to hydrogen exposure in their microstructures. This research study focuses on one hydrogen embrittlement mechanism: Hydrogen-Enhanced-Localized-Plasticity (HELP). The HELP is the only single mechanism characterized by promoting localization of plastic flow ahead of the crack by increasing dislocation motion in that region. The current state of the art is a development of a numerical model representing a fully diffusion-mechanical coupled model. This fully coupled model attempts to gain valuable insights into hydrogen's influence on the mechanical properties and the fatigue life of metals, in general. First, detailed development of a numerical approach is illustrated describing how to fully couple the hydrogen diffusion and stresses using a finite element method. The formulation is based on a coupled temperature-displacement procedure using Abaqus. This coupled computational model, described in this first part, is novel because the mechanical part is based on an isotropic-kinematic hardening law. Furthermore, this fully coupled numerical model can capture both a hardening and softening effect of the stress-strain curve when the solution of the plastic properties is dependent on hydrogen. This can also contribute in a complementary way to the results previously shown by other researchers. Though these previous studies used the same hydrogen diffusion model, their mechanical part was based on a power law. Second, this research attempts to delve into the hydrogen effect on the constitutive response of metals undergoing a cyclic load. Hence, based on the HELP theory, this constitutive coupled model can capture different cyclic hardening behaviors. This study can largely contribute to understanding the degradation of the mechanical properties of materials before crack propagation, which has been heavily covered in the literature.

Yes / The wave–seabed interaction issue is of great importance for the design of foundation around marine infrastructures. Most previous investigations for such a problem have been limited to uncoupled or one-way coupled methods connecting two separated wave and seabed sub models with the continuity of pressures at the seabed surface. In this study, a strongly coupled model was proposed to realize both wave and seabed processes in a same program and to calculate the wave fields and seabed response simultaneously. The information between wave fields and seabed fields were strongly shared and thus results in a more profound investigation of the mechanism of the wave–seabed interaction. In this letter, the wave and seabed models were validated with previous experimental tests. Then, a set of application of present model were discussed in prediction of the wave-induced seabed response. Numerical results show the wave-induced liquefaction area of coupled model is smaller than that of uncoupled model. / Yes

Este trabalho apresenta uma investigação da interação entre o gelo marinho Antártico e o setor austral e sudoeste do Atlântico Sul. Para realizar este estudo foram utilizados dados de satélite da concentração do gelo marinho e o modelo numérico acoplado do NCAR (Nacional Center for Atmospheric Research) o CCSM3 (Community Climate System Model) versão 3. O CCSM3 foi integrado por 150 anos em 3 diferentes simulações. Estas foram forçadas com as climatologias prescritas da concentração de gelo máximo (MAX), mínimo (MIN) e médio (controle) com o objetivo de avaliar o impacto das mudanças do gelo marinho Antártico no Mar de Weddell e na região da Confluência Brasil-Malvinas (CBM). Este estudo enfatiza a interação das escalas de tempo anual, interanual a decadal. A metodologia empregada nesta pesquisa inclue as análises de correlação e espectral, bem como as técnicas estatísticas de funções ortogonais empíricas (EOF) e decomposição de valores singulares (SVD). O comportamento climático das variáveis oceânicas apresentou sensibilidade às diferentes concentrações de gelo marinho Antártico. A variabilidade das anomalias de TSM e SSM mostraram para o experimento MIN padrões espaciais que caracterizam um regime frio do Giro de Weddell, associado a menor intrusão da CDW. A resposta da variabilidade da temperatura, entre os cenários de gelo MAX e MIN, para a região da CBM sugere que menores concentrações de gelo marinho Antártico intensificam as anomalias de TSM desta região, com periodicidade interanual de 2-3 anos e decadal de 25 anos. A circulação oceânica, em ambas as regiões analisadas, associada a fase positiva da SAM se intensifica devido a influência das menores concentrações de gelo marinho. / In this work the interaction between Antarctic sea-ice and the South Atlantic ocean (austral and southwestern sectors) is investigated. To accomplish this satellite-observed sea-ice concentration (SIC) and a coupled model from NCAR-CCSM3 (National Center for Atmospheric Research - Community Climate System Model version 3) were employed. Three 150-year simulations, one each with the maximum (MAX), minimum (MIN) and average (control) SIC prescribed climatologies, were used to drive the CCSM3 run. The goal of the research is to evaluate the Weddell Sea and Brazil-Malvinas confluence (BMC) response to observed extremes in Antarctic sea-ice. This study focuses on annual, interannual and decadal timescales. The applied methodology uses correlation and spectrum analyses, as well as Empirical Orthogonal Functions (EOF) and Singular Value Decomposition (SVD). The annual mean behavior of oceanic variables showed sensibility to Antarctic sea-ice changes. The variability of SST and SSS anomalies showed for the sea-ice MIN experiment a spatial pattern that characterizes the cold regime of the Weddell Gyre, associate with low CDW intrusion. The response of the temperature variability, between sea-ice MAX and MIN scenarios, for the BMC region suggests that less Antarctic sea-ice produces a SST anomaly intensification in this region with a interannual cycle of the 2-3year and decadal cycle of the 25-year. The oceanic circulation in both study regions, related to positive SAM events, showed a intensification to less SIC influence.

Este trabalho apresenta uma investigação da interação entre o gelo marinho Antártico e o setor austral e sudoeste do Atlântico Sul. Para realizar este estudo foram utilizados dados de satélite da concentração do gelo marinho e o modelo numérico acoplado do NCAR (Nacional Center for Atmospheric Research) o CCSM3 (Community Climate System Model) versão 3. O CCSM3 foi integrado por 150 anos em 3 diferentes simulações. Estas foram forçadas com as climatologias prescritas da concentração de gelo máximo (MAX), mínimo (MIN) e médio (controle) com o objetivo de avaliar o impacto das mudanças do gelo marinho Antártico no Mar de Weddell e na região da Confluência Brasil-Malvinas (CBM). Este estudo enfatiza a interação das escalas de tempo anual, interanual a decadal. A metodologia empregada nesta pesquisa inclue as análises de correlação e espectral, bem como as técnicas estatísticas de funções ortogonais empíricas (EOF) e decomposição de valores singulares (SVD). O comportamento climático das variáveis oceânicas apresentou sensibilidade às diferentes concentrações de gelo marinho Antártico. A variabilidade das anomalias de TSM e SSM mostraram para o experimento MIN padrões espaciais que caracterizam um regime frio do Giro de Weddell, associado a menor intrusão da CDW. A resposta da variabilidade da temperatura, entre os cenários de gelo MAX e MIN, para a região da CBM sugere que menores concentrações de gelo marinho Antártico intensificam as anomalias de TSM desta região, com periodicidade interanual de 2-3 anos e decadal de 25 anos. A circulação oceânica, em ambas as regiões analisadas, associada a fase positiva da SAM se intensifica devido a influência das menores concentrações de gelo marinho. / In this work the interaction between Antarctic sea-ice and the South Atlantic ocean (austral and southwestern sectors) is investigated. To accomplish this satellite-observed sea-ice concentration (SIC) and a coupled model from NCAR-CCSM3 (National Center for Atmospheric Research - Community Climate System Model version 3) were employed. Three 150-year simulations, one each with the maximum (MAX), minimum (MIN) and average (control) SIC prescribed climatologies, were used to drive the CCSM3 run. The goal of the research is to evaluate the Weddell Sea and Brazil-Malvinas confluence (BMC) response to observed extremes in Antarctic sea-ice. This study focuses on annual, interannual and decadal timescales. The applied methodology uses correlation and spectrum analyses, as well as Empirical Orthogonal Functions (EOF) and Singular Value Decomposition (SVD). The annual mean behavior of oceanic variables showed sensibility to Antarctic sea-ice changes. The variability of SST and SSS anomalies showed for the sea-ice MIN experiment a spatial pattern that characterizes the cold regime of the Weddell Gyre, associate with low CDW intrusion. The response of the temperature variability, between sea-ice MAX and MIN scenarios, for the BMC region suggests that less Antarctic sea-ice produces a SST anomaly intensification in this region with a interannual cycle of the 2-3year and decadal cycle of the 25-year. The oceanic circulation in both study regions, related to positive SAM events, showed a intensification to less SIC influence.