Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 22 for “"adjoint model"”.
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State estimation of the Labrador Sea with a coupled sea ice-ocean adjoint model
… time-evolving dynamically consistent numerical model. To elaborate upon the relationship between SI and ocean variability, a one year (1996- 1997) state estimate of the ocean and sea ice state in Labrador Sea and Baffin Bay is constructed and analyzed. The estimate is a synthesis of a regional …
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The use of adjoint models for determining the sensitivity of integral quantities in an eddy resolving Oean General Circulation Model
Adjoint models calculate the exact sensitivity of an output function of a model to infinitesimal perturbations in the forcing or initial conditions. In eddy resolving ocean models the presence of chaotic eddies is expected to lead to sensitivities to infinitesimal perturbations that are very …
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Using derivative information in the statistical analysis of computer models
Complex deterministic models are an important tool for studying a wide range of systems. Often though, such models are computationally too expensive to perform the many runs required. In this case one option is to build a Gaussian process emulator which acts as a surrogate, enabling fast prediction …
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Quantifying Terrestrial and Aquatic Ecosystem Methane Emissions with Process-based Biogeochemistry and Atmospheric Transport and Chemistry Models
… from Arctic wetlands and lakes, an integrated modeling framework was developed. It includes a newly developed process-based lake biogeochemical model and a widely used 4-D VAR inversion algorithm implemented with the nested grid high-resolution GEOS-Chem Adjoint model.
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Adjoint sensitivity analysis of the intercontinental impacts of aviation emissions on air quality and health
… various locations and times, this study uses the adjoint model of GEOS-Chem, a chemical transport model. The adjoint method efficiently computes sensitivities of a few objective functions, such as aggregated PM concentration and human exposure to PM concentration, with respect to many input …
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Subduction in an eddy-resolving state estimate of the northeast Atlantic Ocean
… combining a regional, eddy-resolving numerical model with observations to produce a state estimate of the ocean circulation. The estimate is a synthesis of a variety of in-situ observations from the Subduction Experiment, TOPEX/POSEIDON altimetry, and the MIT General Circulation Model. A novel …
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Subduction in an eddy-resolving state estimate of the northeast Atlantic Ocean
… combining a regional, eddy-resolving numerical model with observations to produce a state estimate of the ocean circulation. The estimate is a synthesis of a variety of in-situ observations from the Subduction Experiment, TOPEX/POSEIDON altimetry, and the MIT General Circulation Model. A novel …
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Structural analysis and optimization with a locally-Cartesian Hybrid Shell Model
The Hybrid Shell Model (HSM) is presented as an intermediate-fidelity structural model well suited for conceptual design of aerospace vehicles. Although significantly simpler and more economical than full 3D elasticity models, it can still capture full 3D geometries, large deformations, and …
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Constraining North Atlantic circulation with transient tracer observations
… temperature and salinity (T-S) observations with model results in the North Atlantic shows that regions of important model-data disagreements in the transient tracer fields can also be readily identified in the T-S distributions. In the model, excessive vertical penetration of convective …
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Computational Tools for Chemical Data Assimilation with CMAQ
… is the Environmental Protection Agency's main modeling tool for atmospheric pollution studies. CMAQ-ADJ, the adjoint model of CMAQ, offers new analysis capabilities such as receptor-oriented sensitivity analysis and chemical data assimilation. This thesis presents the construction, validation, …
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The Southern Ocean meridional overturning circulation as diagnosed from an eddy permitting state estimate
A modern general circulation model of the Southern Ocean with one-sixth of a degree resolution is optimized to the observed ocean in a weighted least squares sense. Convergence to the state estimate solution is carried out by systematically adjusting the control variables (atmospheric state and …
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The southern ocean meridional overturning circulation as diagnosed from an eddy permitting state estimate
A modern general circulation model of the Southern Ocean with one-sixth of a degree resolution is optimized to the observed ocean in a weighted least squares sense. Convergence to the state estimate solution is carried out by systematically adjusting the control variables (atmospheric state and …
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Driving the ocean's overturning : an adjoint sensitivity study
… and mixing on climatological time scales. An adjoint model is used to gain new insights into the spatial characteristics of the sensitivity patterns. Adjoint models provide the sensitivity of a diagnostic, often called cost function, to all model parameters in a single integration. In …
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Constraining the North Atlantic circulation with transient tracer observations
… temperature and salinity (T-S) observations with model results in the North Atlantic shows that regions of important model-data disagreements in the transient tracer fields can also be readily identified in the T-S distributions. In the model, excessive vertical penetration of convective …
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Probabilistic machine learning for the elimination of thermoacoustic instabilities
… for decades. They are notoriously difficult to model and despite efforts to eliminate them, can show up unexpectedly. The current thesis demonstrates how Bayesian machine learning techniques may be of benefit when modeling, designing against and trying to avoid thermoacoustic instabilities. We …
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Benefit-cost assessment of aviation environmental policies
… using sensitivity values calculated from an adjoint model built-in to the global chemical transport model (GCTM) used for the atmospheric modeling within this analysis. From this fast policy tool, first order estimates of the impact of ULSJ on premature mortality are calculated.
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Efficient Computational Tools for Variational Data Assimilation and Information Content Estimation
… procedure to combine data from observations with model predictions to obtain a more accurate representation of the state of the atmosphere. As models become more complex, determining the relationships between pollutants and their sources and sinks becomes computationally more challenging. The …
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Adjoint based solution and uncertainty quantification techniques for variational inverse problems
… system. Control parameters of the computational model are optimized such that the simulation results fit the physical measurements.The solution procedure is computationally expensive since it involves running the simulation computer model (the emph{forward model}) and the associated emph {adjoint …
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Applications of Adjoint Modelling in Chemical Composition: Studies of Tropospheric Ozone at Middle and High Northern Latitudes
… The GEOS-Chem global chemical transport model and its adjoint are used to interpret the impacts of midlatitude precursor emissions and atmospheric transport on the tropospheric ozone distribution at middle and high northern latitudes. In the Arctic, the model reproduces seasonal cycles of …
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MATLODE: A MATLAB ODE Solver and Sensitivity Analysis Toolbox
… the effect that of perturbations of the model inputs have on the model's outputs. Some of the key insights gained using sensitivity analysis are to understand the robustness of the model with respect to perturbations, and to select the most important parameters for the model. MATLODE is a …
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