Science.gov

Sample records for order ocean model

  1. High-Order/Low-Order methods for ocean modeling

    SciTech Connect

    Newman, Christopher; Womeldorff, Geoff; Chacón, Luis; Knoll, Dana A.

    2015-06-01

    We examine a High Order/Low Order (HOLO) approach for a z-level ocean model and show that the traditional semi-implicit and split-explicit methods, as well as a recent preconditioning strategy, can easily be cast in the framework of HOLO methods. The HOLO formulation admits an implicit-explicit method that is algorithmically scalable and second-order accurate, allowing timesteps much larger than the barotropic time scale. We demonstrate how HOLO approaches, in particular the implicit-explicit method, can provide a solid route for ocean simulation to heterogeneous computing and exascale environments.

  2. Low-order models of biogenic ocean mixing

    NASA Astrophysics Data System (ADS)

    Dabiri, J. O.; Rosinelli, D.; Koumoutsakos, P.

    2009-12-01

    Biogenic ocean mixing, the process whereby swimming animals may affect ocean circulation, has primarily been studied using order-of-magnitude theoretical estimates and a small number of field observations. We describe numerical simulations of arrays of simplified animal shapes migrating in inviscid fluid and at finite Reynolds numbers. The effect of density stratification is modeled in the fluid dynamic equations of motion by a buoyancy acceleration term, which arises due to perturbations to the density field by the migrating bodies. The effects of fluid viscosity, body spacing, and array configuration are investigated to identify scenarios in which a meaningful contribution to ocean mixing by swimming animals is plausible.

  3. Massively parallel implementation of a high order domain decomposition equatorial ocean model

    SciTech Connect

    Ma, H.; McCaffrey, J.W.; Piacsek, S.

    1999-06-01

    The present work is about the algorithms and parallel constructs of a spectral element equatorial ocean model. It shows that high order domain decomposition ocean models can be efficiently implemented on massively parallel architectures, such as the Connection Machine Model CM5. The optimized computational efficiency of the parallel spectral element ocean model comes not only from the exponential convergence of the numerical solution, but also from the work-intensive, medium-grained, geometry-based data parallelism. The data parallelism is created to efficiently implement the spectral element ocean model on the distributed-memory massively parallel computer, which minimizes communication among processing nodes. Computational complexity analysis is given for the parallel algorithm of the spectral element ocean model, and the model's parallel performance on the CM5 is evaluated. Lastly, results from a simulation of wind-driven circulation in low-latitude Atlantic Ocean are described.

  4. MASSIVELY PARALLEL IMPLEMENTATION OF A HIGH ORDER DOMAIN DECOMPOSITION EQUATORIAL OCEAN MODEL

    SciTech Connect

    MA,H.; MCCAFFREY,J.W.; PIACSEK,S.

    1998-07-15

    The present work is about the algorithms and parallel constructs of a spectral element equatorial ocean model. It shows that high order domain decomposition ocean models can be efficiently implemented on massively parallel architectures, such as the Connection Machine Model CM5. The optimized computational efficiency of the parallel spectral element ocean model comes not only from the exponential convergence of the numerical solution, but also from the work-intensive, medium-grained, geometry-based data parallelism. The data parallelism is created to efficiently implement the spectral element ocean model on the distributed-memory massively parallel computer, which minimizes communication among processing nodes. Computational complexity analysis is given for the parallel algorithm of the spectral element ocean model, and the model's parallel performance on the CM5 is evaluated. Lastly, results from a simulation of wind-driven circulation in low-latitude Atlantic ocean are described.

  5. The Modular Arbitrary-Order Ocean-Atmosphere Model of the RMIB: MAOOAM

    NASA Astrophysics Data System (ADS)

    De Cruz, Lesley; Demaeyer, Jonathan; Vannitsem, Stéphane

    2016-04-01

    The coupled ocean-atmosphere system exhibits a decadal variability at midlatitudes, which gives rise to the North-Atlantic Oscillation (NOA). The driving mechanism behind this variability has been the subject of much interest and debate in recent years. This conundrum was addressed using several low-order coupled ocean-atmosphere models for midlatitudes, with an increasing level of physical realism: OA-QG-WS v1 [1], v2 [2], and most recently, VDDG [3]. The VDDG-model was designed to capture the key dynamics of the coupled ocean-atmosphere system, featuring a two-layer atmosphere over a shallow-water ocean layer with passively advected temperature. It incorporates both frictional coupling and an energy balance scheme which accounts for radiative and heat fluxes between ocean and atmosphere. The spectral expansion was truncated at 10 atmospheric and 8 oceanic modes, and a coupled low-frequency variability was found. We present an extended version of the VDDG model, in which an arbitrary number of atmospheric and oceanic modes can be retained. The modularity of the new model version allows one to easily modify the model physics. Using this new model, named the "Modular Arbitrary-Order Ocean-Atmosphere Model" (MAOOAM), we analyse the dependence of the model dynamics on the truncation level of the spectral expansion. Indeed, previous studies have shown that spurious behaviour may exist in low-resolution models, which can be unveiled by a comparison with their high-resolution counterparts [4]. In particular, we assess the robustness of the coupled low-frequency variability when the number of modes is increased. References [1] Vannitsem, S.: Dynamics and predictability of a low-order wind-driven ocean-atmosphere coupled model, Climate dynamics, 42, 1981-1998, 2014. [2] Vannitsem, S. and De Cruz, L.: A 24-variable low-order coupled ocean-atmosphere model: OA-QG-WS v2, Geoscientific Model Development, 7, 649-662, 2014. [3] Vannitsem, S., Demaeyer, J., De Cruz, L., and Ghil

  6. Stochastic modelling and predictability: analysis of a low-order coupled ocean-atmosphere model.

    PubMed

    Vannitsem, Stéphane

    2014-06-28

    There is a growing interest in developing stochastic schemes for the description of processes that are poorly represented in atmospheric and climate models, in order to increase their variability and reduce the impact of model errors. The use of such noise could however have adverse effects by modifying in undesired ways a certain number of moments of their probability distributions. In this work, the impact of developing a stochastic scheme (based on stochastic averaging) for the ocean is explored in the context of a low-order coupled (deterministic) ocean-atmosphere system. After briefly analysing its variability, its ability in predicting the oceanic flow generated by the coupled system is investigated. Different phases in the error dynamics are found: for short lead times, an initial overdispersion of the ensemble forecast is present while the ensemble mean follows a dynamics reminiscent of the combined amplification of initial condition and model errors for deterministic systems; for longer lead times, a reliable diffusive ensemble spread is observed. These different phases are also found for ensemble-oriented skill measures like the Brier score and the rank histogram. The implications of these features on building stochastic models are then briefly discussed.

  7. Dynamics and predictability of a low-order wind-driven ocean - atmosphere model

    NASA Astrophysics Data System (ADS)

    Vannitsem, Stéphane

    2013-04-01

    The dynamics of a low order coupled wind-driven Ocean-Atmosphere (OA) system is investigated with emphasis on its predictability properties. The low-order coupled deterministic system is composed of a baroclinic atmosphere for which 12 dominant dynamical modes are only retained (Charney and Straus, 1980) and a wind-driven, quasi-geostrophic and reduced-gravity shallow ocean whose field is truncated to four dominant modes able to reproduce the large scale oceanic gyres (Pierini, 2011). The two models are coupled through mechanical forcings only. The analysis of its dynamics reveals first that under aperiodic atmospheric forcings only dominant single gyres (clockwise or counterclockwise) appear. This feature is expected to be related with the specific domain choice over which the coupled system is defined. Second the dynamical quantities characterizing the short-term predictability (Lyapunov exponents, Lyapunov dimension, Kolmogorov-Sinaï (KS) entropy) displays a complex dependence as a function of the key parameters of the system, namely the coupling strength and the external thermal forcing. In particular, the KS-entropy is increasing as a function of the coupling in most of the experiments, implying an increase of the rate of loss of information about the localization of the system on his attractor. Finally the dynamics of the error is explored and indicates, in particular, a rich variety of short term behaviors of the error in the atmosphere depending on the (relative) amplitude of the initial error affecting the ocean, from polynomial (at2 + bt3 + ct4) up to purely exponential evolutions. These features are explained and analyzed in the light of the recent findings on error growth (Nicolis et al, 2009). References Charney J G, Straus DM (1980) Form-Drag Instability, Multiple Equilibria and Propagating Planetary Waves in Baroclinic, Orographically Forced, Planetary Wave Systems. J Atmos Sci 37: 1157-1176. Nicolis C, Perdigao RAP, Vannitsem S (2009) Dynamics of

  8. Dynamics and predictability of a low-order wind-driven ocean-atmosphere coupled model

    NASA Astrophysics Data System (ADS)

    Vannitsem, Stéphane

    2014-04-01

    The dynamics of a low-order coupled wind-driven ocean-atmosphere system is investigated with emphasis on its predictability properties. The low-order coupled deterministic system is composed of a baroclinic atmosphere for which 12 dominant dynamical modes are only retained (Charney and Straus in J Atmos Sci 37:1157-1176, 1980) and a wind-driven, quasi-geostrophic and reduced-gravity shallow ocean whose field is truncated to four dominant modes able to reproduce the large scale oceanic gyres (Pierini in J Phys Oceanogr 41:1585-1604, 2011). The two models are coupled through mechanical forcings only. The analysis of its dynamics reveals first that under aperiodic atmospheric forcings only dominant single gyres (clockwise or counterclockwise) appear, while for periodic atmospheric solutions the double gyres emerge. In the present model domain setting context, this feature is related to the level of truncation of the atmospheric fields, as indicated by a preliminary analysis of the impact of higher wavenumber ("synoptic" scale) modes on the development of oceanic gyres. In the latter case, double gyres appear in the presence of a chaotic atmosphere. Second the dynamical quantities characterizing the short-term predictability (Lyapunov exponents, Lyapunov dimension, Kolmogorov-Sinaï (KS) entropy) displays a complex dependence as a function of the key parameters of the system, namely the coupling strength and the external thermal forcing. In particular, the KS-entropy is increasing as a function of the coupling in most of the experiments, implying an increase of the rate of loss of information about the localization of the system on its attractor. Finally the dynamics of the error is explored and indicates, in particular, a rich variety of short term behaviors of the error in the atmosphere depending on the (relative) amplitude of the initial error affecting the ocean, from polynomial ( at 2 + bt 3 + ct 4) up to exponential-like evolutions. These features are explained

  9. A New Ice-sheet / Ocean Interaction Model for Greenland Fjords using High-Order Discontinuous Galerkin Methods

    NASA Astrophysics Data System (ADS)

    Kopera, M. A.; Maslowski, W.; Giraldo, F.

    2015-12-01

    One of the key outstanding challenges in modeling of climate change and sea-level rise is the ice-sheet/ocean interaction in narrow, elongated and geometrically complicated fjords around Greenland. To address this challenge we propose a new approach, a separate fjord model using discontinuous Galerkin (DG) methods, or FDG. The goal of this project is to build a separate, high-resolution module for use in Earth System Models (ESMs) to realistically represent the fjord bathymetry, coastlines, exchanges with the outside ocean, circulation and fine-scale processes occurring within the fjord and interactions at the ice shelf interface. FDG is currently at the first stage of development. The DG method provides FDG with high-order accuracy as well as geometrical flexibility, including the capacity to handle non-conforming adaptive mesh refinement to resolve the processes occurring near the ice-sheet/ocean interface without introducing prohibitive computational costs. Another benefit of this method is its excellent performance on multi- and many-core architectures, which allows for utilizing modern high performance computing systems for high-resolution simulations. The non-hydrostatic model of the incompressible Navier-Stokes equation will account for the stationary ice-shelf with sub-shelf ocean interaction, basal melting and subglacial meltwater influx and with boundary conditions at the surface to account for floating sea ice. The boundary conditions will be provided to FDG via a flux coupler to emulate the integration with an ESM. Initially, FDG will be tested for the Sermilik Fjord settings, using real bathymetry, boundary and initial conditions, and evaluated against available observations and other model results for this fjord. The overarching goal of the project is to be able to resolve the ice-sheet/ocean interactions around the entire coast of Greenland and two-way coupling with regional and global climate models such as the Regional Arctic System Model (RASM

  10. A Parallel Icosahedral, Higher Order Discontinuous Galerkin, Global Shallow Water Model: Global Ocean Tides and Aquaplanet Benchmarks

    NASA Astrophysics Data System (ADS)

    Salehipour, H.; Stuhne, G.; Peltier, W. R.

    2012-12-01

    The development of models of the ocean tides with higher resolution near the coastlines and courser mesh offshore, has been required due to the significant impacts of coastline configuration and bathymetry (associated with sea level rise) on the amplitude and phase of tidal constituents, not only under present conditions but also in the deep past [Griffiths and Peltier GRL 2008, Griffiths and Peltier AMS 2009, Hill et al. JGR 2011]. A global tidal model with enhanced resolution at the poles has been developed by Griffiths and Peltier [2008, 2009], which, although capable of highly resolving polar ocean tides , is based upon a standard structured Arakawa C grid and hence is not capable of resolving coastlines locally. Furthermore the use of a nested modelling approach, although it may enable local spatial refinement [Hill et al. 2011], nevertheless suffers from its inherent dependence on the availability of a global tidal model with necessarily low spatial resolution to provide the open boundary conditions required for the local high resolution model. On the other hand, an unstructured triangulation of the global domain provides a standalone framework that may be employed to study highly resolved regions without relying on secondary models. The first step in the development of the structure we are employing was described in Stuhne and Peltier [Ocean Modeling, 2009]. In further extending this modelling structure we are employing a new discontinuous Galerkin (DG) discretization of the governing equations in order to provide very high order of accuracy while also ensuring that momentum transport is locally conserved [Giraldo et al. JCP 2002]. After validating the 2D shallow water model with several test suites appropriate to aquaplanets [Williamson et al. JCP 1992, Galewsky et al. Tellus 2004, Nair and Lauritzen JCP 2010], the governing equations are extended to include the influence of internal tide drag in the deep ocean as well as the drag in shallow marginal seas

  11. Earth and ocean modeling

    NASA Technical Reports Server (NTRS)

    Knezovich, F. M.

    1976-01-01

    A modular structured system of computer programs is presented utilizing earth and ocean dynamical data keyed to finitely defined parameters. The model is an assemblage of mathematical algorithms with an inherent capability of maturation with progressive improvements in observational data frequencies, accuracies and scopes. The Eom in its present state is a first-order approach to a geophysical model of the earth's dynamics.

  12. Interaction between surface wind and ocean circulation in the Carolina Capes in a coupled low-order model

    SciTech Connect

    Xie, L.; Pietrafesa, L.J.; Raman, S.

    1997-03-18

    Interactions between surface winds and ocean currents over an east-coast continental shelf are studied using a simple mathematical model. The model physics include cross-shelf advection of sea surface temperature (SST) by Ekman drift, upwelling due to Ekman transport divergence, differential heating of the low-level atmosphere by a cross-shelf SST gradient, and the Coriolis effect. Additionally, the effects of diabatic cooling of surface waters due to air-sea heat exchange and of the vertical density stratification on the thickness of the upper ocean Ekman layer are considered. The model results are qualitatively consistent with observed wind-driven coastal ocean circulation and surface wind signatures induced by SST. This simple model also demonstrates that two-way air-sea interaction plays a significant role in the subtidal frequency variability of coastal ocean circulation and mesoscale variability of surface wind fields over coastal waters.

  13. Ocean General Circulation Models

    SciTech Connect

    Yoon, Jin-Ho; Ma, Po-Lun

    2012-09-30

    1. Definition of Subject The purpose of this text is to provide an introduction to aspects of oceanic general circulation models (OGCMs), an important component of Climate System or Earth System Model (ESM). The role of the ocean in ESMs is described in Chapter XX (EDITOR: PLEASE FIND THE COUPLED CLIMATE or EARTH SYSTEM MODELING CHAPTERS). The emerging need for understanding the Earth’s climate system and especially projecting its future evolution has encouraged scientists to explore the dynamical, physical, and biogeochemical processes in the ocean. Understanding the role of these processes in the climate system is an interesting and challenging scientific subject. For example, a research question how much extra heat or CO2 generated by anthropogenic activities can be stored in the deep ocean is not only scientifically interesting but also important in projecting future climate of the earth. Thus, OGCMs have been developed and applied to investigate the various oceanic processes and their role in the climate system.

  14. Mesoscale ocean dynamics modeling

    SciTech Connect

    mHolm, D.; Alber, M.; Bayly, B.; Camassa, R.; Choi, W.; Cockburn, B.; Jones, D.; Lifschitz, A.; Margolin, L.; Marsden, L.; Nadiga, B.; Poje, A.; Smolarkiewicz, P.; Levermore, D.

    1996-05-01

    This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The ocean is a very complex nonlinear system that exhibits turbulence on essentially all scales, multiple equilibria, and significant intrinsic variability. Modeling the ocean`s dynamics at mesoscales is of fundamental importance for long-time-scale climate predictions. A major goal of this project has been to coordinate, strengthen, and focus the efforts of applied mathematicians, computer scientists, computational physicists and engineers (at LANL and a consortium of Universities) in a joint effort addressing the issues in mesoscale ocean dynamics. The project combines expertise in the core competencies of high performance computing and theory of complex systems in a new way that has great potential for improving ocean models now running on the Connection Machines CM-200 and CM-5 and on the Cray T3D.

  15. Application of a Reduced Order Kalman Filter to Initialize a Coupled Atmosphere-Ocean Model: Impact on the Prediction of El Nino

    NASA Technical Reports Server (NTRS)

    Ballabrera-Poy, J.; Busalacchi, A.; Murtugudde, R.

    2000-01-01

    A reduced order Kalman Filter, based on a simplification of the Singular Evolutive Extended Kalman (SEEK) filter equations, is used to assimilate observed fields of the surface wind stress, sea surface temperature and sea level into the nonlinear coupled ocean-atmosphere model of Zebiak and Cane. The SEEK filter projects the Kalman Filter equations onto a subspace defined by the eigenvalue decomposition of the error forecast matrix, allowing its application to high dimensional systems. The Zebiak and Cane model couples a linear reduced gravity ocean model with a single vertical mode atmospheric model of Zebiak. The compatibility between the simplified physics of the model and each observed variable is studied separately and together. The results show the ability of the model to represent the simultaneous value of the wind stress, SST and sea level, when the fields are limited to the latitude band 10 deg S - 10 deg N In this first application of the Kalman Filter to a coupled ocean-atmosphere prediction model, the sea level fields are assimilated in terms of the Kelvin and Rossby modes of the thermocline depth anomaly. An estimation of the error of these modes is derived from the projection of an estimation of the sea level error over such modes. This method gives a value of 12 for the error of the Kelvin amplitude, and 6 m of error for the Rossby component of the thermocline depth. The ability of the method to reconstruct the state of the equatorial Pacific and predict its time evolution is demonstrated. The method is shown to be quite robust for predictions up to six months, and able to predict the onset of the 1997 warm event fifteen months before its occurrence.

  16. Application of a Reduced Order Kalman Filter to Initialize a Coupled Atmosphere-Ocean Model: Impact on the Prediction of El Nino

    NASA Technical Reports Server (NTRS)

    Ballabrera-Poy, Joaquim; Busalacchi, Antonio J.; Murtugudde, Ragu

    2000-01-01

    A reduced order Kalman Filter, based on a simplification of the Singular Evolutive Extended Kalman (SEEK) filter equations, is used to assimilate observed fields of the surface wind stress, sea surface temperature and sea level into the nonlinear coupled ocean-atmosphere model. The SEEK filter projects the Kalman Filter equations onto a subspace defined by the eigenvalue decomposition of the error forecast matrix, allowing its application to high dimensional systems. The Zebiak and Cane model couples a linear reduced gravity ocean model with a single vertical mode atmospheric model of Zebiak. The compatibility between the simplified physics of the model and each observed variable is studied separately and together. The results show the ability of the model to represent the simultaneous value of the wind stress, SST and sea level, when the fields are limited to the latitude band 10 deg S - 10 deg N. In this first application of the Kalman Filter to a coupled ocean-atmosphere prediction model, the sea level fields are assimilated in terms of the Kelvin and Rossby modes of the thermocline depth anomaly. An estimation of the error of these modes is derived from the projection of an estimation of the sea level error over such modes. This method gives a value of 12 for the error of the Kelvin amplitude, and 6 m of error for the Rossby component of the thermocline depth. The ability of the method to reconstruct the state of the equatorial Pacific and predict its time evolution is demonstrated. The method is shown to be quite robust for predictions I up to six months, and able to predict the onset of the 1997 warm event fifteen months before its occurrence.

  17. Simple ocean carbon cycle models

    SciTech Connect

    Caldeira, K.; Hoffert, M.I.; Siegenthaler, U.

    1994-02-01

    Simple ocean carbon cycle models can be used to calculate the rate at which the oceans are likely to absorb CO{sub 2} from the atmosphere. For problems involving steady-state ocean circulation, well calibrated ocean models produce results that are very similar to results obtained using general circulation models. Hence, simple ocean carbon cycle models may be appropriate for use in studies in which the time or expense of running large scale general circulation models would be prohibitive. Simple ocean models have the advantage of being based on a small number of explicit assumptions. The simplicity of these ocean models facilitates the understanding of model results.

  18. Open ocean tide modelling

    NASA Technical Reports Server (NTRS)

    Parke, M. E.

    1978-01-01

    Two trends evident in global tidal modelling since the first GEOP conference in 1972 are described. The first centers on the incorporation of terms for ocean loading and gravitational self attraction into Laplace's tidal equations. The second centers on a better understanding of the problem of near resonant modelling and the need for realistic maps of tidal elevation for use by geodesists and geophysicists. Although new models still show significant differences, especially in the South Atlantic, there are significant similarities in many of the world's oceans. This allows suggestions to be made for future locations for bottom pressure gauge measurements. Where available, estimates of M2 tidal dissipation from the new models are significantly lower than estimates from previous models.

  19. Implementation of a reduced order Kalman filter to assimilate ocean color data into a coupled physical-biochemical model of the North Aegean Sea.

    NASA Astrophysics Data System (ADS)

    Kalaroni, Sofia; Tsiaras, Kostas; Economou-Amilli, Athena; Petihakis, George; Politikos, Dimitrios; Triantafyllou, George

    2013-04-01

    Within the framework of the European project OPEC (Operational Ecology), a data assimilation system was implemented to describe chlorophyll-a concentrations of the North Aegean, as well the impact on the European anchovy (Engraulis encrasicolus) biomass distribution provided by a bioenergetics model, related to the density of three low trophic level functional groups of zooplankton (heterotrophic flagellates, microzooplankton and mesozooplankton). The three-dimensional hydrodynamic-biogeochemical model comprises two on-line coupled sub-models: the Princeton Ocean Model (POM) and the European Regional Seas Ecosystem Model (ERSEM). The assimilation scheme is based on the Singular Evolutive Extended Kalman (SEEK) filter and its variant that uses a fixed correction base (SFEK). For the initialization, SEEK filter uses a reduced order error covariance matrix provided by the dominant Empirical Orthogonal Functions (EOF) of model. The assimilation experiments were performed for year 2003 using SeaWiFS chlorophyll-a data during which the physical model uses the atmospheric forcing obtained from the regional climate model HIRHAM5. The assimilation system is validated by assessing the relevance of the system in fitting the data, the impact of the assimilation on non-observed biochemical parameters and the overall quality of the forecasts.

  20. Simulating Tsunamis in the Indian Ocean with Real Bathymetry by using a High- Order Triangular Discontinuous Galerkin Oceanic Shallow Water Model

    DTIC Science & Technology

    2009-03-01

    fault extent constrained by observed tsunami arrival time to the northwest, east and south of the slip zone indicates a fault zone of approximately...1000 kilometers by 200 kilometers. The epicenter location lies on the southern end of the fault zone . To accommodate trench curvature, this fault plane...Pollitz, and S. L. Bilek, ”Implications of the 26 December 2004 Sumatra-Andaman earthquake on tsunami forecast and assessment models for great subduction

  1. LLNL Ocean General Circulation Model

    SciTech Connect

    Wickett, M. E.; Caldeira, K.; Duffy, P.

    2005-12-29

    The LLNL OGCM is a numerical ocean modeling tool for use in studying ocean circulation over a wide range of space and time scales, with primary applications to climate change and carbon cycle science.

  2. Modeling ocean deep convection

    NASA Astrophysics Data System (ADS)

    Canuto, V. M.; Howard, A.; Hogan, P.; Cheng, Y.; Dubovikov, M. S.; Montenegro, L. M.

    The goal of this study is to assess models for Deep Convection with special emphasis on their use in coarse resolution ocean general circulation models. A model for deep convection must contain both vertical transport and lateral advection by mesoscale eddies generated by baroclinic instabilities. The first process operates mostly in the initial phases while the second dominates the final stages. Here, the emphasis is on models for vertical mixing. When mesoscales are not resolved, they are treated with the Gent and McWilliams parameterization. The model results are tested against the measurements of Lavender, Davis and Owens, 2002 (LDO) in the Labrador Sea. Specifically, we shall inquire whether the models are able to reproduce the region of " deepest convection," which we shall refer to as DC (mixed layer depths 800-1300 m). The region where it was measured by Lavender et al. (2002) will be referred to as the LDO region. The main results of this study can be summarized as follows. 3° × 3° resolution. A GFDL-type OGCM with the GISS vertical mixing model predicts DC in the LDO region where the vertical heat diffusivity is found to be 10 m 2 s -1, a value that is quite close to the one suggested by heuristic studies. No parameter was changed from the original GISS model. However, the GISS model also predicts some DC in a region to the east of the LDO region. 3° × 3° resolution. A GFDL-type OGCM with the KPP model (everything else being the same) does not predict DC in the LDO region where the vertical heat diffusivity is found to be 0.5 × 10 -4 m 2 s -1 which is the background value. The KPP model yields DC only to the east of the LDO region. 1° × 1° resolution. In this case, a MY2.5 mixing scheme predicts DC in the LDO region. However, it also predicts DC to the west, north and south of it, where it is not observed. The behavior of the KPP and MY models are somewhat anti-symmetric. The MY models yield too low a mixing in stably stratified flows since they

  3. Development of ocean model LSOMG

    NASA Astrophysics Data System (ADS)

    Sachl, Libor; Martinec, Zdenek

    2015-04-01

    The purpose of this contribution is to present the ocean general circulation model LSOMG. It originates from the LSG (Maier-Reimer and Mikolajewicz, 1992) ocean model, however, significant number of changes has been made. LSOMG is a z-coordinate baroclinic ocean model which solves the primitive equations under the Boussinesq approximation. We intend to use the model for a various geophysical applications with the focus on paleoclimate studies. Hence, the model is not as complex as the current state-of-art climate models, such as the Modular Ocean Model or NEMO models. On the other hand, it is less computationally demanding. The changes and improvements in the code will be reported. One of the obvious changes is that the governing equations are no more discretized on the Arakawa E grid. The whole model has been rewritten on the Arakawa C grid. The main motivation is to avoid a coexistence of two solutions on the grid that evolve independently of each other. A more natural treatment of boundary conditions and simpler structure of the grid are additional advantages. Another significant change is the treatment of time tendencies. The system of equations is split to barotropic and baroclinic subsystems. Both subsystems may either be discretized at the same time points (as in the original LSG model), or their discretizations may be staggered in time as described in Griffies (2004). The original fully implicit barotropic time stepping scheme was found to significantly dissipate energy. Three different time stepping schemes are available instead. Namely, the predictor-corrector scheme of Griffies (2004), the generalized forward-backward scheme of Shchepetkin and McWilliams (2008) and the implicit free surface scheme of Campin et al. (2004). The first two schemes are intended to be used with the split-explicit model configuration for short-term studies whereas the third scheme is suitable for long-term studies, e.g. paleoclimate studies. The short-term studies may also

  4. Reduced Order Podolsky Model

    NASA Astrophysics Data System (ADS)

    Thibes, Ronaldo

    2017-02-01

    We perform the canonical and path integral quantizations of a lower-order derivatives model describing Podolsky's generalized electrodynamics. The physical content of the model shows an auxiliary massive vector field coupled to the usual electromagnetic field. The equivalence with Podolsky's original model is studied at classical and quantum levels. Concerning the dynamical time evolution, we obtain a theory with two first-class and two second-class constraints in phase space. We calculate explicitly the corresponding Dirac brackets involving both vector fields. We use the Senjanovic procedure to implement the second-class constraints and the Batalin-Fradkin-Vilkovisky path integral quantization scheme to deal with the symmetries generated by the first-class constraints. The physical interpretation of the results turns out to be simpler due to the reduced derivatives order permeating the equations of motion, Dirac brackets and effective action.

  5. Climate Modeling: Ocean Cavities below Ice Shelves

    SciTech Connect

    Petersen, Mark Roger

    2016-09-12

    The Accelerated Climate Model for Energy (ACME), a new initiative by the U.S. Department of Energy, includes unstructured-mesh ocean, land-ice, and sea-ice components using the Model for Prediction Across Scales (MPAS) framework. The ability to run coupled high-resolution global simulations efficiently on large, high-performance computers is a priority for ACME. Sub-ice shelf ocean cavities are a significant new capability in ACME, and will be used to better understand how changing ocean temperature and currents influence glacial melting and retreat. These simulations take advantage of the horizontal variable-resolution mesh and adaptive vertical coordinate in MPAS-Ocean, in order to place high resolution below ice shelves and near grounding lines.

  6. Dissipation effects in North Atlantic Ocean modeling

    NASA Astrophysics Data System (ADS)

    Dietrich, D. E.; Mehra, A.; Haney, R. L.; Bowman, M. J.; Tseng, Y. H.

    2004-03-01

    Numerical experiments varying lateral viscosity and diffusivity between 20 and 150 m2/s in a North Atlantic Ocean (NAO) model having 4th-order accurate numerics, in which the dense deep current system (DCS) from the northern seas and Arctic Ocean is simulated directly show that Gulf Stream (GS) separation is strongly affected by the dissipation of the DCS. This is true even though the separation is highly inertial with large Reynolds number for GS separation flow scales. We show that realistic NAO modeling requires less than 150 m2/s viscosity and diffusivity in order to maintain the DCS material current with enough intensity to get realistic GS separation near Cape Hatteras (CH). This also demands accurate, low dissipation numerics, because of the long transit time (1-10 years) of DCS material from its northern seas and Arctic Ocean source regions to the Cape Hatteras region and the small lateral and vertical scales of DCS.

  7. Assimilation of Along-track Altimetry Data Into An Eddy-permitting Primitive-equation Model of The North and Tropical Atlantic Ocean Using Isopycnal-eof Order-reduction

    NASA Astrophysics Data System (ADS)

    Faucher, P.; de Mey, P.; Gavart, M.

    We present and discuss altimetric assimilation experiments into a primitive-equation model of the North Atlantic using isopycnal EOFs to propagate the altimeter sig- nal downwards and to the other model variables. Faucher, Gavart and De Mey (JGR, 2002) showed from a set of historical hydrographic data that the dominant isopycnal EOF accounts for most of the surface dynamic height variability in the North Atlantic ocean. In addition the reduced-order observability problem for altimetry is more nat- urally studied in isopycnal coordinates because the displacement of isopycnals is the largest contribution of deep ocean dynamics to the sea-level changes. The 1/3 degree ocean model from the CLIPPER and MERCATOR projects (based on OPA 8.1 code developped at LODYC, Paris) was used to solve the primitive equations from 20S to 70N. The assimilation experiments were performed with the combined along-track TOPEX-POSEIDON and ERS-1 data sets between 1 january 1993 and 31 decem- ber 1993. We implemented a multivariate reduced-order optimal interpolation method (SOFA: De Mey and Benkiran, 2002) with a vertical projection of altimetry data using data-based isopycnal EOFs. This paper will show and discuss compared results from several approaches in different regions of the North Atlantic.

  8. Four simple ocean carbon models

    NASA Technical Reports Server (NTRS)

    Moore, Berrien, III

    1992-01-01

    This paper briefly reviews the key processes that determine oceanic CO2 uptake and sets this description within the context of four simple ocean carbon models. These models capture, in varying degrees, these key processes and establish a clear foundation for more realistic models that incorporate more directly the underlying physics and biology of the ocean rather than relying on simple parametric schemes. The purpose of this paper is more pedagogical than purely scientific. The problems encountered by current attempts to understand the global carbon cycle not only require our efforts but set a demand for a new generation of scientist, and it is hoped that this paper and the text in which it appears will help in this development.

  9. Ocean U.S. GODAE: Global Ocean Prediction with the HYbrid Coordinate Ocean Model (HYCOM)

    DTIC Science & Technology

    2008-10-01

    Ocean U.S. GODAE: Global Ocean Prediction with the HYbrid Coordinate Ocean Model (HYCOM) By Eric P. Chassignet1 and Harley E. Hurlburt2 1 COAPS ...UAcademia:U Florida State University/Center for Ocean-Atmospheric Prediction Studies ( COAPS ); University of Miami/Rosenstiel School of Marine and

  10. Ocean modeling in a global ocean observing system

    NASA Astrophysics Data System (ADS)

    Smith, Neville R.

    1993-08-01

    The oceanographic community is currently contemplating the design of a global ocean climate observing system to help monitor, describe, and understand the seasonal to decadal climate changes of the ocean and to provide the observations needed for climate prediction. This review attempts to define a role for modeling within that system, the central theme being that the observational and modeling elements must be developed in concert, with the presence of one enhancing the value of the other. Three distinct categories of model-to-data interface are identified. In the first class, models and data collection develop separately, being joined only by intermittent validation steps. In the second, and by far most important, class the model and data collection evolve together, either in a time-space data assimilation and prediction system, or through the application of inverse methods. In the final category, model information feeds back to the observing system design, and vice versa, and the model assimilation system provides quality control on the data. The key role of (atmospheric) models in the determination of surface fluxes to drive ocean models is discussed. A nontrivial role is proposed for ocean models whereby they provide additional, and largely independent, constraints on atmospheric forecast system estimates. The role of ocean models in the analysis of surface and upper ocean fields needs to be developed, particularly with respect to salinity and nonphysical fields. The use of models in rationalizing the choice of observation platforms is discussed, together with some of the difficulties in interpreting such studies. The state of tropical ocean prediction is reviewed with particular emphasis on systems that assimilate subsurface temperature data. A range of thermocline models are also reviewed with the emphasis on subduction and the problem of initializing and constraining models that resolve mesoscale eddies. Some of the issues involved in matching the models to

  11. First-order linear tectonovolcanic ridges in oceans

    NASA Astrophysics Data System (ADS)

    Pushcharovsky, Yu. M.

    2011-03-01

    The first-order Line, Hawaiian, Emperor, Pukapuka, Louisville, Ninetyeast, and Chagos-Lackadive tectonovolcanic ridges in the Pacific and Indian oceans are considered. These ridges are combined into the category of demarcation tectonic units separating the largest morphostructural sectors of the oceans. The ridges extend for thousands kilometers and are a few hundred kilometers in width. Their crest zones are crowned by numerous volcanoes. The volcanic rocks are largely basalts with elevated alkalinity. All of the ridges were formed in the Late Cretaceous-Cenozoic; the ages of particular ridges are variable. The dimensions of the demarcation tectonic units allow us to refer them to the processes proceeding in the mantle, including tectonic flow, faulting, and significant strike-slip displacements.

  12. A Review of Ocean Models.

    DTIC Science & Technology

    1981-01-23

    Dimensional Turbulence Kinetic Energy Equation 4-13 4.2.4 The Parameterization of Surface Fluxes 4-14 4.3 BULK MIXING-LAYER MODELS 4-16 4.3.1 Buoyancy...Momentum Conservation 4-54 4.4.2 Turbulence Flux Model 4-54 4.4.3 Diffusion Model Intercomparisons 4-65 4.5 DISCUSSION 4-74 REFERENCES 4-77 I I...mixed surface layer (Kise, 1979), and to forcing induced by mixed-layer turbulence (Bell, 1978). One-dimensional upper-ocean models are based on the

  13. Modelling ocean circulation in Deep-ocean aquaplanets

    NASA Astrophysics Data System (ADS)

    McKinstry, A.

    2012-04-01

    Léger et al. (2004) and Küchner (2003) hypothesised that Ocean planets, Super-Earth planets with liquid-water oceans covering their whole surfaces may exist. Planets with liquid water surfaces could have ocean depths of 70-100 km with bottom pressures of 1-5 GPa. To date, no general circulation models have been run on such oceans, primarily because of a lack of equation of state for seawater at such depths. In this work a deep-water seawater Equation of State is implemented in the MITgcm ocean model. The EOS depends not only on the salinity and temperature but also on CO2 concentration. Several proposed ocean compositions, in particular magnesium and sodium sulphates salts ,H2O / ammonia mixes are investigated. While geothermal plumes in pure water systems will rise through an the whole ocean depths, saline-enriched plumes do not, due to differential thermal expansions for saline fluids leading to a loss of buoyancy (Melosh et al., 2004). Vance and Brown (2005) have shown that double-diffusive convection is expected to be a significant feature of such high-pressure oceans: depending on ocean composition, a double-diffusive layer will frustrate deep ocean convective processes and hence heat transfer. Convection happens separately in the warm, saline layers below and cooler, more dilute layer above. While this has been seen in isolated areas on Earth, such as the Red Sea, we explore the effects of heat and salin transfer through this layer on global circulation for deep ocean planet.

  14. A first-order estimate of shock heating and vaporization in oceanic impacts

    NASA Technical Reports Server (NTRS)

    Croft, S. K.

    1982-01-01

    The vaporization of water in oceanic impacts of asteroids or comets of multikilometer dimensions is estimated by a semianalytical modeling of impact heating and shock isobar geometry that is based on computer code calculations. The mass of water vaporized in an infinitely deep ocean by the impact of a 10 km diameter asteroid at 25 km/sec (these values have been proposed for the Cretaceous/Tertiary extinction bolide) is approximately equal to the total mass of water vapor present in the earth's atmosphere, and 3-4 orders of magnitude larger than the mass of water vapor in the stratosphere. For projectiles of this size, however, the finite depth of the ocean becomes significant and may considerably reduce the amount of water vapor initially generated by the impact. Climatological models and extinction scenarios invoking the effects of impact-generated water vapor may critically depend on the a priori ambiguous details of the hypothesized impact.

  15. On effective resolution in ocean models

    NASA Astrophysics Data System (ADS)

    Soufflet, Yves; Marchesiello, Patrick; Lemarié, Florian; Jouanno, Julien; Capet, Xavier; Debreu, Laurent; Benshila, Rachid

    2016-02-01

    The increase of model resolution naturally leads to the representation of a wider energy spectrum. As a result, in recent years, the understanding of oceanic submesoscale dynamics has significantly improved. However, dissipation in submesoscale models remains dominated by numerical constraints rather than physical ones. Effective resolution is limited by the numerical dissipation range, which is a function of the model numerical filters (assuming that dispersive numerical modes are efficiently removed). We present a Baroclinic jet test case set in a zonally reentrant channel that provides a controllable test of a model capacity at resolving submesoscale dynamics. We compare simulations from two models, ROMS and NEMO, at different mesh sizes (from 20 to 2 km). Through a spectral decomposition of kinetic energy and its budget terms, we identify the characteristics of numerical dissipation and effective resolution. It shows that numerical dissipation appears in different parts of a model, especially in spatial advection-diffusion schemes for momentum equations (KE dissipation) and tracer equations (APE dissipation) and in the time stepping algorithms. Effective resolution, defined by scale-selective dissipation, is inadequate to qualify traditional ocean models with low-order spatial and temporal filters, even at high grid resolution. High-order methods are better suited to the concept and probably unavoidable. Fourth-order filters are suited only for grid resolutions less than a few kilometers and momentum advection schemes of even higher-order may be justified. The upgrade of time stepping algorithms (from filtered Leapfrog), a cumbersome task in a model, appears critical from our results, not just as a matter of model solution quality but also of computational efficiency (extended stability range of predictor-corrector schemes). Effective resolution is also shaken by the need for non scale-selective barotropic mode filters and requires carefully addressing the

  16. Determining Reduced Order Models for Optimal Stochastic Reduced Order Models

    SciTech Connect

    Bonney, Matthew S.; Brake, Matthew R.W.

    2015-08-01

    The use of parameterized reduced order models(PROMs) within the stochastic reduced order model (SROM) framework is a logical progression for both methods. In this report, five different parameterized reduced order models are selected and critiqued against the other models along with truth model for the example of the Brake-Reuss beam. The models are: a Taylor series using finite difference, a proper orthogonal decomposition of the the output, a Craig-Bampton representation of the model, a method that uses Hyper-Dual numbers to determine the sensitivities, and a Meta-Model method that uses the Hyper-Dual results and constructs a polynomial curve to better represent the output data. The methods are compared against a parameter sweep and a distribution propagation where the first four statistical moments are used as a comparison. Each method produces very accurate results with the Craig-Bampton reduction having the least accurate results. The models are also compared based on time requirements for the evaluation of each model where the Meta- Model requires the least amount of time for computation by a significant amount. Each of the five models provided accurate results in a reasonable time frame. The determination of which model to use is dependent on the availability of the high-fidelity model and how many evaluations can be performed. Analysis of the output distribution is examined by using a large Monte-Carlo simulation along with a reduced simulation using Latin Hypercube and the stochastic reduced order model sampling technique. Both techniques produced accurate results. The stochastic reduced order modeling technique produced less error when compared to an exhaustive sampling for the majority of methods.

  17. Toward Submesocale Ocean Modelling and Observations for Global Ocean Forecast.

    NASA Astrophysics Data System (ADS)

    Drillet, Y.

    2014-12-01

    Mercator Ocean is the French oceanographic operational center involved in the development an operation of global high resolution ocean forecasting systems; it is part of the European Copernicus Marine service initiated during MyOcean project. Mercator Ocean currently delivers daily 1/12° global ocean forecast based on the NEMO model which allows for a good representation of mesoscale structures in main areas of the global ocean. Data assimilation of altimetry provides a precise initialization of the mesoscale structures while in situ observations, mainly based on the ARGO network, and satellite Sea Surface Temperature constrain water mass properties from the surface to intermediate depths. One of the main improvements scheduled in the coming years is the transitioning towards submesoscale permitting horizontal resolution (1/36°). On the basis of numerical simulations in selected areas and standard diagnostics developed to validate operational systems, we will discuss : i) The impact of the resolution increase at the basin scale. ii) Adequacy of numerical schemes, vertical resolution and physical parameterization. iii) Adequacy of currently implemented data assimilation procedures in particular with respect to new high resolution data set such as SWOT.

  18. Computational ocean acoustics: Advances in 3D ocean acoustic modeling

    NASA Astrophysics Data System (ADS)

    Schmidt, Henrik; Jensen, Finn B.

    2012-11-01

    The numerical model of ocean acoustic propagation developed in the 1980's are still in widespread use today, and the field of computational ocean acoustics is often considered a mature field. However, the explosive increase in computational power available to the community has created opportunities for modeling phenomena that earlier were beyond reach. Most notably, three-dimensional propagation and scattering problems have been prohibitive computationally, but are now addressed routinely using brute force numerical approaches such as the Finite Element Method, in particular for target scattering problems, where they are being combined with the traditional wave theory propagation models in hybrid modeling frameworks. Also, recent years has seen the development of hybrid approaches coupling oceanographic circulation models with acoustic propagation models, enabling the forecasting of sonar performance uncertainty in dynamic ocean environments. These and other advances made over the last couple of decades support the notion that the field of computational ocean acoustics is far from being mature. [Work supported by the Office of Naval Research, Code 321OA].

  19. Modelling Tropical Cyclones-Ocean interactions: the role of the Atmophere - Ocean coupling frequency

    NASA Astrophysics Data System (ADS)

    Scoccimarro, Enrico; Fogli, Pier Giuseppe; Gualdi, Silvio; Masina, Simona; Navarra, Antonio

    2016-04-01

    The interaction between Tropical Cyclones (TCs) and ocean is a major mechanism responsible for energy exchange between the atmosphere and the ocean. TCs affect the thermal and dynamical structure of the ocean, but the magnitude of the impact is still uncertain. Very few CMIP5 models demonstrated ability in representing TCs, mainly due to their horizontal resolution. We aim to improve TCs representation in next CMIPs experiments through the new CMCC-CM2VHR General Circulation Model, having a horizontal resolution of 1/4 degree in both atmospheric and ocean components. The model is capable to represent realistically TCs up to Cat-5 Typhoons. A good representation of the TC-Ocean interaction strongly depends on the coupling frequency between the atmospheric and the ocean components. In this work, we found that a better representation of the negative Sea Surface Temperature - TC induced feedback, through a high (hourly) coupling frequency, ensures the reduction of the TC induced Power Dissipation Index (PDI) bias of one order of magnitude. In addition, a cat-5 storm case study is deeply investigated also in terms of TC effects on the deep ocean.

  20. Scripps Ocean Modeling and Remote Sensing (SOMARS)

    DTIC Science & Technology

    1988-09-20

    Topics in this brief reports include: Kalman filtering of oceanographic data; Remote sensing of sea surface temperature; Altimetry and Surface heat fluxes; Ocean models of the marine mixed layer; Radar altimetry; Mathematical model of California current eddies.

  1. A predictive ocean oil spill model

    SciTech Connect

    Sanderson, J.; Barnette, D.; Papodopoulos, P.; Schaudt, K.; Szabo, D.

    1996-07-01

    This is the final report of a two-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Initially, the project focused on creating an ocean oil spill model and working with the major oil companies to compare their data with the Los Alamos global ocean model. As a result of this initial effort, Los Alamos worked closely with the Eddy Joint Industry Project (EJIP), a consortium oil and gas producing companies in the US. The central theme of the project was to use output produced from LANL`s global ocean model to look in detail at ocean currents in selected geographic areas of the world of interest to consortium members. Once ocean currents are well understood this information could be used to create oil spill models, improve offshore exploration and drilling equipment, and aid in the design of semi-permanent offshore production platforms.

  2. Nested ocean models: Work in progress

    NASA Technical Reports Server (NTRS)

    Perkins, A. Louise

    1991-01-01

    The ongoing work of combining three existing software programs into a nested grid oceanography model is detailed. The HYPER domain decomposition program, the SPEM ocean modeling program, and a quasi-geostrophic model written in England are being combined into a general ocean modeling facility. This facility will be used to test the viability and the capability of two-way nested grids in the North Atlantic.

  3. Ocean foam generation and modeling

    NASA Technical Reports Server (NTRS)

    Porter, R. A.; Bechis, K. P.

    1976-01-01

    A laboratory investigation was conducted to determine the physical and microwave properties of ocean foam. Special foam generators were designed and fabricated, using porous glass sheets, known as glass frits, as the principal element. The glass frit was sealed into a water-tight vertical box, a few centimeters from the bottom. Compressed air, applied to the lower chamber, created ocean foam from sea water lying on the frit. Foam heights of 30 cm were readily achieved, with relatively low air pressures. Special photographic techniques and analytical procedures were employed to determine foam bubble size distributions. In addition, the percentage water content of ocean foam was determined with the aid of a particulate sampling procedure. A glass frit foam generator, with pore diameters in the range 70 - 100 micrometers, produced foam with bubble distributions very similar to those found on the surface of natural ocean foam patches.

  4. Stochastic Modeling of Decadal Variability in Ocean Gyres

    NASA Astrophysics Data System (ADS)

    Kondrashov, Dmitri; Berloff, Pavel

    2015-04-01

    Decadal large-scale low-frequency variability of the ocean circulation due to its nonlinear dynamics remains a big challenge for theoretical understanding and practical ocean modeling. This paper presents a novel fully data-driven approach that addresses this challenge. We propose non-Markovian low-order methodology with stochastic closure and data-adaptive mode decomposition. The multilayer stochastic linear model is obtained from the coarse-grained eddy-resolving ocean model solution, and it reproduces with high accuracy the main statistical properties of the decadal variability. The proposed methodology does not depend on the governing fluid dynamics equations and geometry of the problem, and it can be extended to other ocean models and ultimately to the real data.

  5. Stochastic modeling of decadal variability in ocean gyres

    NASA Astrophysics Data System (ADS)

    Kondrashov, D.; Berloff, P.

    2015-03-01

    Decadal large-scale low-frequency variability of the ocean circulation due to its nonlinear dynamics remains a big challenge for theoretical understanding and practical ocean modeling. This paper presents a novel fully data driven approach that addresses this challenge. Proposed is non-Markovian low-order methodology with stochastic closure and use of mode decomposition by multichannel Singular Spectrum Analysis. The multilayer stochastic linear model is obtained from the coarse-grained eddy-resolving ocean model solution, and with high accuracy it reproduces the main statistical properties of the decadal variability. The proposed methodology does not depend on the governing fluid dynamics equations and geometry of the problem, and it can be extended to other ocean models and ultimately to the real data.

  6. Lagrangian predictability characteristics of an Ocean Model

    NASA Astrophysics Data System (ADS)

    Lacorata, Guglielmo; Palatella, Luigi; Santoleri, Rosalia

    2014-11-01

    The Mediterranean Forecasting System (MFS) Ocean Model, provided by INGV, has been chosen as case study to analyze Lagrangian trajectory predictability by means of a dynamical systems approach. To this regard, numerical trajectories are tested against a large amount of Mediterranean drifter data, used as sample of the actual tracer dynamics across the sea. The separation rate of a trajectory pair is measured by computing the Finite-Scale Lyapunov Exponent (FSLE) of first and second kind. An additional kinematic Lagrangian model (KLM), suitably treated to avoid "sweeping"-related problems, has been nested into the MFS in order to recover, in a statistical sense, the velocity field contributions to pair particle dispersion, at mesoscale level, smoothed out by finite resolution effects. Some of the results emerging from this work are: (a) drifter pair dispersion displays Richardson's turbulent diffusion inside the [10-100] km range, while numerical simulations of MFS alone (i.e., without subgrid model) indicate exponential separation; (b) adding the subgrid model, model pair dispersion gets very close to observed data, indicating that KLM is effective in filling the energy "mesoscale gap" present in MFS velocity fields; (c) there exists a threshold size beyond which pair dispersion becomes weakly sensitive to the difference between model and "real" dynamics; (d) the whole methodology here presented can be used to quantify model errors and validate numerical current fields, as far as forecasts of Lagrangian dispersion are concerned.

  7. Models for ecological models: Ocean primary productivity

    USGS Publications Warehouse

    Wikle, Christopher K.; Leeds, William B.; Hooten, Mevin B.

    2016-01-01

    The ocean accounts for more than 70% of planet Earth's surface, and it processes are critically important to marine and terrestrial life.  Ocean ecosystems are strongly dependent on the physical state of the ocean (e.g., transports, mixing, upwelling, runoff, and ice dynamics(.  As an example, consider the Coastal Gulf of Alaska (CGOA) region.

  8. Optimal Combining Data for Improving Ocean Modeling

    DTIC Science & Technology

    2011-09-30

    of regional circulation models for accurate estimating the upper ocean velocity field, subsurface thermohaline structure, and mixing characteristics...high resolution circulation model - Incorporating subgrid Lagrangian models identified via drifter data into circulation models for improving...velocity field obtained from a realistic circulation model. 2. Constructing and testing fusion algorithms for combining glider observations with

  9. Modelling Ocean Surface Waves in Polar Regions

    NASA Astrophysics Data System (ADS)

    Hosekova, Lucia; Aksenov, Yevgeny; Coward, Andrew; Bertino, Laurent; Williams, Timothy; Nurser, George A. J.

    2015-04-01

    In the Polar Oceans, the surface ocean waves break up sea ice cover and create the Marginal Ice Zone (MIZ), an area between the sea-ice free ocean and pack ice characterized by highly fragmented ice. This band of sea ice cover is undergoing dramatic changes due to sea ice retreat, with up to a 39% widening in the Arctic Ocean reported over the last three decades and projections predicting a continuing increase. The surface waves, sea ice and ocean interact in the MIZ through multiple complex feedbacks and processes which are not accounted for in any of the present-day climate models. To address this issue, we present a model development which implements surface ocean wave effects in the global Ocean General Circulation Model NEMO, coupled to the CICE sea ice model. Our implementation takes into account a number of physical processes specific to the MIZ dynamics. Incoming surface waves are attenuated due to reflection and energy dissipation induced by the presence of ice cover, which is in turn fragmented in response to external stresses. This process generates a distribution of floe sizes and impacts the dynamics of sea ice by the means of combined rheology that takes into account floe collisions and allows for a more realistic representation of the MIZ. We present results from the NEMO OGCM at 1 degree resolution with a wave-ice interaction module described above. The module introduces two new diagnostics previously unavailable in GCM's: surface wave spectra in sea ice covered areas, and floe size distribution due to wave-induced fragmentation. We discuss the impact of these processes on the ocean and sea ice state, including ocean circulation, mixing, stratification and the role of the MIZ in the ocean variability. The model predictions for the floe sizes in the summer Arctic Ocean range from 60 m in the inner MIZ to a few tens of meters near the open ocean, which agrees with estimates from the satellites. The extent of the MIZ throughout the year is also in

  10. An isopycnic ocean carbon cycle model

    NASA Astrophysics Data System (ADS)

    Assmann, K. M.; Bentsen, M.; Segschneider, J.; Heinze, C.

    2010-02-01

    The carbon cycle is a major forcing component in the global climate system. Modelling studies, aiming to explain recent and past climatic changes and to project future ones, increasingly include the interaction between the physical and biogeochemical systems. Their ocean components are generally z-coordinate models that are conceptually easy to use but that employ a vertical coordinate that is alien to the real ocean structure. Here, we present first results from a newly-developed isopycnic carbon cycle model and demonstrate the viability of using an isopycnic physical component for this purpose. As expected, the model represents well the interior ocean transport of biogeochemical tracers and produces realistic tracer distributions. Difficulties in employing a purely isopycnic coordinate lie mainly in the treatment of the surface boundary layer which is often represented by a bulk mixed layer. The most significant adjustments of the ocean biogeochemistry model HAMOCC, for use with an isopycnic coordinate, were in the representation of upper ocean biological production. We present a series of sensitivity studies exploring the effect of changes in biogeochemical and physical processes on export production and nutrient distribution. Apart from giving us pointers for further model development, they highlight the importance of preformed nutrient distributions in the Southern Ocean for global nutrient distributions. The sensitivity studies show that iron limitation for biological particle production, the treatment of light penetration for biological production, and the role of diapycnal mixing result in significant changes of nutrient distributions and liniting factors of biological production.

  11. Thermal and mechanical structure of the upper mantle: A comparison between continental and oceanic models

    NASA Technical Reports Server (NTRS)

    Froidevaux, C.; Schubert, G.; Yuen, D. A.

    1976-01-01

    Temperature, velocity, and viscosity profiles for coupled thermal and mechanical models of the upper mantle beneath continental shields and old ocean basins show that under the continents, both tectonic plates and the asthenosphere, are thicker than they are beneath the oceans. The minimum value of viscosity in the continental asthenosphere is about an order of magnitude larger than in the shear zone beneath oceans. The shear stress or drag underneath continental plates is also approximately an order of magnitude larger than the drag on oceanic plates. Effects of shear heating may account for flattening of ocean floor topography and heat flux in old ocean basins.

  12. A one ocean model of biodiversity

    NASA Astrophysics Data System (ADS)

    O'Dor, Ronald K.; Fennel, Katja; Berghe, Edward Vanden

    2009-09-01

    The history of life is written in the ocean, and the history of the ocean is written in DNA. Geologists have shown us that hundreds of millions of years of ocean history can be revealed from records of a single phylum in cores of mud from abyssal plains. We are now accumulating genetic tools to unravel the relationships of hundreds of phyla to track this history back billions of years. The technologies demonstrated by the Census of Marine Life (CoML) mean that the ocean is no longer opaque or unknowable. The secrets of the largest component of the biosphere are knowable. The cost of understanding the history of ocean life is not cheap, but it is also not prohibitive. A transparent, open ocean is available for us to use to understand ourselves. This article develops a model of biodiversity equilibration in a single, physically static ocean as a step towards biodiversity in physically complex real oceans. It attempts to be quantitative and to simultaneously account for biodiversity patterns from bacteria to whales focusing on emergent properties rather than details. Biodiversity reflects long-term survival of DNA sequences, stabilizing "ecosystem services" despite environmental change. In the ocean, mechanisms for ensuring survival range from prokaryotes maintaining low concentrations of replicable DNA throughout the ocean volume, anticipating local change, to animals whose mobility increases with mass to avoid local change through movement. Whales can reach any point in the ocean in weeks, but prokaryotes can only diffuse. The high metabolic costs of mobility are offset by the dramatically lower number of DNA replicates required to ensure survival. Reproduction rates probably scale more or less inversely with body mass. Bacteria respond in a week, plankton in a year, whales in a century. We generally lack coherent theories to explain the origins of animals (metazoans) and the contributions of biodiversity to ecosystems. The One Ocean Model suggests that mobile

  13. Development of an Ocean Model for COAMPS

    DTIC Science & Technology

    2016-06-07

    leveraging related programs to develop an ocean data assimilation capability. This prediction system will be the cornerstone of a vertically...ocean data assimilation system to a mesoscale atmospheric data assimilation system. This will include studies of issues that include, but are not...any given area; the availability of data , particularly synthetic observations; and the lack of a full-physics global model present the largest

  14. A coastal ocean model with subgrid approximation

    NASA Astrophysics Data System (ADS)

    Walters, Roy A.

    2016-06-01

    A wide variety of coastal ocean models exist, each having attributes that reflect specific application areas. The model presented here is based on finite element methods with unstructured grids containing triangular and quadrilateral elements. The model optimizes robustness, accuracy, and efficiency by using semi-implicit methods in time in order to remove the most restrictive stability constraints, by using a semi-Lagrangian advection approximation to remove Courant number constraints, and by solving a wave equation at the discrete level for enhanced efficiency. An added feature is the approximation of the effects of subgrid objects. Here, the Reynolds-averaged Navier-Stokes equations and the incompressibility constraint are volume averaged over one or more computational cells. This procedure gives rise to new terms which must be approximated as a closure problem. A study of tidal power generation is presented as an example of this method. A problem that arises is specifying appropriate thrust and power coefficients for the volume averaged velocity when they are usually referenced to free stream velocity. A new contribution here is the evaluation of three approaches to this problem: an iteration procedure and two mapping formulations. All three sets of results for thrust (form drag) and power are in reasonable agreement.

  15. Higher order turbulence closure models

    NASA Technical Reports Server (NTRS)

    Amano, Ryoichi S.; Chai, John C.; Chen, Jau-Der

    1988-01-01

    Theoretical models are developed and numerical studies conducted on various types of flows including both elliptic and parabolic. The purpose of this study is to find better higher order closure models for the computations of complex flows. This report summarizes three new achievements: (1) completion of the Reynolds-stress closure by developing a new pressure-strain correlation; (2) development of a parabolic code to compute jets and wakes; and, (3) application to a flow through a 180 deg turnaround duct by adopting a boundary fitted coordinate system. In the above mentioned models near-wall models are developed for pressure-strain correlation and third-moment, and incorporated into the transport equations. This addition improved the results considerably and is recommended for future computations. A new parabolic code to solve shear flows without coordinate tranformations is developed and incorporated in this study. This code uses the structure of the finite volume method to solve the governing equations implicitly. The code was validated with the experimental results available in the literature.

  16. Optimal Combining Data for Improving Ocean Modeling

    DTIC Science & Technology

    2012-09-30

    regional circulation models for accurate estimating the upper ocean velocity field, subsurface thermohaline structure, and mixing characteristics (2...data fusion in the framework of twin experiments with a high resolution circulation model and on real data - Combining radar data with tracer... thermohaline patterns and, second, separating space and time variability in glider observations for fast changing thermohaline structures (etc mesoscale fronts

  17. Ocean Model Assessment with Lagrangian Metrics

    DTIC Science & Technology

    2016-06-07

    project are to aid in the development of accurate modeling of upper ocean circulation by using data on circulation observations to test models. These tests...Approved for public release; distribution unlimited 13. SUPPLEMENTARY NOTES 14. ABSTRACT The long-term goals of this project are to aid in the

  18. An isopycnic ocean carbon cycle model

    NASA Astrophysics Data System (ADS)

    Assmann, K. M.; Bentsen, M.; Segschneider, J.; Heinze, C.

    2009-07-01

    The carbon cycle is a major forcing component in the global climate system. Modelling studies aiming to explain recent and past climatic changes and to project future ones thus increasingly include the interaction between the physical and biogeochemical systems. Their ocean components are generally z-coordinate models that are conceptually easy to use but that employ a vertical coordinate that is alien to the real ocean structure. Here we present first results from a newly developed isopycnic carbon cycle model and demonstrate the viability of using an isopycnic physical component for this purpose. As expected, the model represents interior ocean transport of biogeochemical tracers well and produces realistic tracer distributions. Difficulties in employing a purely isopycnic coordinate lie mainly in the treatment of the surface boundary layer which is often represented by a bulk mixed layer. The most significant adjustments of the biogeochemical code for use with an isopycnic coordinate are in the representation of upper ocean biological production. We present a series of sensitivity studies exploring the effect of changes in biogeochemical and physical processes on export production and nutrient distribution. Apart from giving us pointers for further model development, they highlight the importance of preformed nutrient distributions in the Southern Ocean for global nutrient distributions. Use of a prognostic slab atmosphere allows us to assess the effect of the changes in export production on global ocean carbon uptake and atmospheric CO2 levels. Sensitivity studies show that iron limitation for biological particle production, the treatment of light penetration for biological production, and the role of diapycnal mixing result in significant changes of modelled air-sea fluxes and nutrient distributions.

  19. Modeling oceanic and atmospheric vortices

    SciTech Connect

    Dritschel, D.G.; Legras, B. CNRS, Lab. de Meteorologie Dynamique, Paris )

    1993-03-01

    Numerical modeling and prediction of coherent structures in geophysical fluid dynamics is reviewed. Numerical computation is widely used in geophysical fluid dynamics due to the nonlinear behaviour of the systems studied and the complexity of the mathematical models used. Idealized systems and the determination of potential vorticity in simplified atmospheric models are discussed. Atmospheric vortex structures, their interactions, and the effects on weather are described. A quasigeostrophic model is used to illustrate the effect of trophospherically generated disturbances on the polar vortex using the contour dynamics numerical method. A comparison of numerical techniques for simulating the evolution of neighboring vortices of unequal size is given. Future developments in the use of numerical models in geophysical fluid dynamics and weather prediction are discussed. 15 refs.

  20. Optimal Combining Data for Improving Ocean Modeling

    DTIC Science & Technology

    2013-09-30

    improving diagnosis and prediction of meso- and submesoscale processes in coastal frontal zones. Our theoretical findings in studying finite-size... Submesoscale physical- biogeochemical coupling across the Ligurian Current (northwestern Mediterranean) using a bio- optical glider, Limnol. Oceanogr...Garraffo, and L. Piterbarg , 2012, Parameterization of Submesoscale Transport in the Gulf Stream Region Using Lagrangian Subgridscale Models, Ocean

  1. iMarNet: an ocean biogeochemistry model intercomparison project within a common physical ocean modelling framework

    NASA Astrophysics Data System (ADS)

    Kwiatkowski, L.; Yool, A.; Allen, J. I.; Anderson, T. R.; Barciela, R.; Buitenhuis, E. T.; Butenschön, M.; Enright, C.; Halloran, P. R.; Le Quéré, C.; de Mora, L.; Racault, M.-F.; Sinha, B.; Totterdell, I. J.; Cox, P. M.

    2014-12-01

    Ocean biogeochemistry (OBGC) models span a wide variety of complexities, including highly simplified nutrient-restoring schemes, nutrient-phytoplankton-zooplankton-detritus (NPZD) models that crudely represent the marine biota, models that represent a broader trophic structure by grouping organisms as plankton functional types (PFTs) based on their biogeochemical role (dynamic green ocean models) and ecosystem models that group organisms by ecological function and trait. OBGC models are now integral components of Earth system models (ESMs), but they compete for computing resources with higher resolution dynamical setups and with other components such as atmospheric chemistry and terrestrial vegetation schemes. As such, the choice of OBGC in ESMs needs to balance model complexity and realism alongside relative computing cost. Here we present an intercomparison of six OBGC models that were candidates for implementation within the next UK Earth system model (UKESM1). The models cover a large range of biological complexity (from 7 to 57 tracers) but all include representations of at least the nitrogen, carbon, alkalinity and oxygen cycles. Each OBGC model was coupled to the ocean general circulation model Nucleus for European Modelling of the Ocean (NEMO) and results from physically identical hindcast simulations were compared. Model skill was evaluated for biogeochemical metrics of global-scale bulk properties using conventional statistical techniques. The computing cost of each model was also measured in standardised tests run at two resource levels. No model is shown to consistently outperform all other models across all metrics. Nonetheless, the simpler models are broadly closer to observations across a number of fields and thus offer a high-efficiency option for ESMs that prioritise high-resolution climate dynamics. However, simpler models provide limited insight into more complex marine biogeochemical processes and ecosystem pathways, and a parallel approach of

  2. iMarNet: an ocean biogeochemistry model inter-comparison project within a common physical ocean modelling framework

    NASA Astrophysics Data System (ADS)

    Kwiatkowski, L.; Yool, A.; Allen, J. I.; Anderson, T. R.; Barciela, R.; Buitenhuis, E. T.; Butenschön, M.; Enright, C.; Halloran, P. R.; Le Quéré, C.; de Mora, L.; Racault, M.-F.; Sinha, B.; Totterdell, I. J.; Cox, P. M.

    2014-07-01

    Ocean biogeochemistry (OBGC) models span a wide range of complexities from highly simplified, nutrient-restoring schemes, through nutrient-phytoplankton-zooplankton-detritus (NPZD) models that crudely represent the marine biota, through to models that represent a broader trophic structure by grouping organisms as plankton functional types (PFT) based on their biogeochemical role (Dynamic Green Ocean Models; DGOM) and ecosystem models which group organisms by ecological function and trait. OBGC models are now integral components of Earth System Models (ESMs), but they compete for computing resources with higher resolution dynamical setups and with other components such as atmospheric chemistry and terrestrial vegetation schemes. As such, the choice of OBGC in ESMs needs to balance model complexity and realism alongside relative computing cost. Here, we present an inter-comparison of six OBGC models that were candidates for implementation within the next UK Earth System Model (UKESM1). The models cover a large range of biological complexity (from 7 to 57 tracers) but all include representations of at least the nitrogen, carbon, alkalinity and oxygen cycles. Each OBGC model was coupled to the Nucleus for the European Modelling of the Ocean (NEMO) ocean general circulation model (GCM), and results from physically identical hindcast simulations were compared. Model skill was evaluated for biogeochemical metrics of global-scale bulk properties using conventional statistical techniques. The computing cost of each model was also measured in standardised tests run at two resource levels. No model is shown to consistently outperform or underperform all other models across all metrics. Nonetheless, the simpler models that are easier to tune are broadly closer to observations across a number of fields, and thus offer a high-efficiency option for ESMs that prioritise high resolution climate dynamics. However, simpler models provide limited insight into more complex marine

  3. Serving ocean model data on the cloud

    USGS Publications Warehouse

    Meisinger, M.; Farcas, C.; Farcas, E.; Alexander, Corrine; Arrott, M.; de La Beaujardière, J.; Hubbard, P.; Mendelssohn, R.; Signell, R.

    2009-01-01

    The NOAA-led Integrated Ocean Observing System (IOOS) and the NSF-funded Ocean Observatories Initiative Cyberinfrastructure Project (OOI-CI) are collaborating on a prototype data delivery system for numerical model output and other gridded data using cloud computing. The strategy is to take an existing distributed system for delivering gridded data and redeploy on the cloud, making modifications to the system that allow it to harness the scalability of the cloud as well as adding functionality that the scalability affords. ??2009 MTS.

  4. Assimilation of altimeter topography into oceanic models

    NASA Technical Reports Server (NTRS)

    Demey, Pierre; Menard, Yves; Pinardi, Nadia; Schroeter, J.; Verron, J.

    1991-01-01

    The primary goals of the authors are to build an intuition for assimilation techniques and to investigate the impact of variable altimeter topography on simple or complex oceanic models. In particular, applying various techniques and sensitivity studies to model and data constraints plays a key role. We are starting to use quasi-geostrophic, semigeostrophic, and primitive-equation (PE) models and to test the schemes in regions of interest to the World Ocean Circulation Experiment (WOCE), as well as in the northeast Atlantic and the Mediterranean. The impact of scatterometer wind forcing on the results is also investigated. The use of Geosat, European Remote Sensing satellite (ERS-1), and TOPEX/POSEIDON altimetry data is crucial in fine tuning the models and schemes to the selected areas of interest.

  5. Effects of ocean grid resolution on tropical cyclone-induced upper ocean responses using a global ocean general circulation model

    NASA Astrophysics Data System (ADS)

    Li, Hui; Sriver, Ryan L.

    2016-11-01

    Tropical cyclones (TCs) have the potential to influence regional and global climate through interactions with the upper ocean. Here we present results from a suite of ocean-only model experiments featuring the Community Earth System Model, in which we analyze the effect of tropical cyclone wind forcing on the global ocean using three different horizontal ocean grid resolutions (3°, 1°, and 0.1°). The ocean simulations are forced with identical atmospheric inputs from the Coordinated Ocean-Ice Reference Experiments version 2 (COREv2) normal year forcing conditions, featuring global blended TC winds from a fully coupled CESM simulation with a 25 km atmosphere. The simulated TC climatology shows good agreement with observational estimates of annual TC statistics, including annual frequency, intensity distributions, and geographic distributions. Each ocean simulation is composed of a 5 year spin-up with COREv2 normal year forcing, followed by 18 months with blended TC winds. In addition, we conduct corresponding control simulations for each grid resolution configuration without blended TC winds. We find that ocean horizontal and vertical grid resolutions affect TC-induced heat and momentum fluxes, poststorm cold wake features, and ocean subsurface temperature profiles. The responses are amplified for smaller grid spacing. Moreover, analyses show that the annually accumulated TC-induced ocean heat uptake is also sensitive to ocean grid resolution, which may have important implications for modeled ocean heat budgets and variability.

  6. Tropical Weather System and Ocean Modeling.

    DTIC Science & Technology

    1983-01-01

    September issue. The draft of a second article on the ocean model has been completed. Both articles are included as Appendices in this final report. We have...of the study result will be given. The interactions between atmospheric vortex pairs are simulated and studied with a nondivergent barotropic model...relative movements -" -J of the vortices are sensitive to the separation distance " /91

  7. Higher Order Cumulant Studies of Ocean Surface Random Fields from Satellite Altimeter Data

    NASA Technical Reports Server (NTRS)

    Cheng, B.

    1996-01-01

    Higher order statistics, especially 2nd order statistics, have been used to study ocean processes for many years in the past, and occupy an appreciable part of the research literature on physical oceanography. They in turn form part of a much larger field of study in statistical fluid mechanics.

  8. Partially molten magma ocean model

    SciTech Connect

    Shirley, D.N.

    1983-02-15

    The properties of the lunar crust and upper mantle can be explained if the outer 300-400 km of the moon was initially only partially molten rather than fully molten. The top of the partially molten region contained about 20% melt and decreased to 0% at 300-400 km depth. Nuclei of anorthositic crust formed over localized bodies of magma segregated from the partial melt, then grew peripherally until they coverd the moon. Throughout most of its growth period the anorthosite crust floated on a layer of magma a few km thick. The thickness of this layer is regulated by the opposing forces of loss of material by fractional crystallization and addition of magma from the partial melt below. Concentrations of Sr, Eu, and Sm in pristine ferroan anorthosites are found to be consistent with this model, as are trends for the ferroan anorthosites and Mg-rich suites on a diagram of An in plagioclase vs. mg in mafics. Clustering of Eu, Sr, and mg values found among pristine ferroan anorthosites are predicted by this model.

  9. Submesoscale Flows and Mixing in the Oceanic Surface Layer Using the Regional Oceanic Modeling System (ROMS)

    DTIC Science & Technology

    2014-09-30

    Submesoscale Flows and Mixing in the Oceanic Surface Layer Using the Regional Oceanic Modeling System (ROMS) M. Jeroen Molemaker (PI) James C...long-term goals of this project are to further the insight into the dynamics of submesoscale flow in the oceanic surface layer. Using the Regional...Oceanic Modeling System (ROMS), we aim to understand the impact of submesoscale processes on tracer mixing at small scales and the transfer of energy

  10. The dependence of global ocean modeling on background diapycnal mixing.

    PubMed

    Deng, Zengan

    2014-01-01

    The Argo-derived background diapycnal mixing (BDM) proposed by Deng et al. (in publish) is introduced to and applied in Hybrid Coordinate Ocean Model (HYCOM). Sensitive experiments are carried out using HYCOM to detect the responses of ocean surface temperature and Meridional Overturning Circulation (MOC) to BDM in a global context. Preliminary results show that utilizing a constant BDM, with the same order of magnitude as the realistic one, may cause significant deviation in temperature and MOC. It is found that the dependence of surface temperature and MOC on BDM is prominent. Surface temperature is decreased with the increase of BDM, because diapycnal mixing can promote the deep cold water return to the upper ocean. Comparing to the control run, more striking MOC changes can be caused by the larger variation in BDM.

  11. The forecasting Ocean assimilation model (FOAM) system

    NASA Astrophysics Data System (ADS)

    Bell, M. J.; Acreman, D.; Barciela, R.; Hines, A.; Martin, M. J.; Sellar, A.; Stark, J.; Storkey, D.

    The FOAM system is built around the ocean and sea-ice components of the Met Office's Unified Model (UM), developed by the Hadley Centre for coupled ocean-ice-atmosphere climate prediction. It is forced by 6-hourly surface fluxes from the Met Office's Numerical Weather Prediction (NWP) system, and assimilates temperature and salinity profiles from in situ instruments, surface temperature, sea-ice concentration and sea surface height data. A coarse resolution global configuration of FOAM on a 1 ° latitude-longitude grid with 20 vertical levels was implemented in the Met Office's operational suite in 1997. Nested models with grid spacings ranging from 30 km to 6 km are used to provide detailed forecasts for selected regions. The models are run each morning and typically produce 5-day forecasts. Real-time daily and archived analyses for the North Atlantic are freely available at http://nerc-essc.reading.ac.uk/las for research and developmentpurposes. We will present results from studies of the accuracy of the forecasts and how it depends on the data types assimilated and the assimilation scheme used. We will also briefly describe the developments being made to assimilate sea-ice concentration and velocity data and incorporate the HadOCC NPZD (nutrient-phytoplankton-zooplankton-detritus) model and assimilation of ocean colour data.

  12. Ocean Prediction with the Hybrid Coordinate Ocean Model (HYCOM)

    DTIC Science & Technology

    2006-01-01

    into hybrid approaches. Isopycnal (density tracking) layers are best in the deep stratified ocean, z-levels (constant fixed depths) are best used to...when this would lead to excessive crowding of coordinate surfaces. Thus, vertical grid points can be geometrically constrained to remain at a fixed depth...isopycnal in the open stratified ocean, but smoothly reverts to a terrain-following (a) coordinate in shallow coastal regions and to fixed pressure

  13. Mixing parametrizations for ocean climate modelling

    NASA Astrophysics Data System (ADS)

    Gusev, Anatoly; Moshonkin, Sergey; Diansky, Nikolay; Zalesny, Vladimir

    2016-04-01

    The algorithm is presented of splitting the total evolutionary equations for the turbulence kinetic energy (TKE) and turbulence dissipation frequency (TDF), which is used to parameterize the viscosity and diffusion coefficients in ocean circulation models. The turbulence model equations are split into the stages of transport-diffusion and generation-dissipation. For the generation-dissipation stage, the following schemes are implemented: the explicit-implicit numerical scheme, analytical solution and the asymptotic behavior of the analytical solutions. The experiments were performed with different mixing parameterizations for the modelling of Arctic and the Atlantic climate decadal variability with the eddy-permitting circulation model INMOM (Institute of Numerical Mathematics Ocean Model) using vertical grid refinement in the zone of fully developed turbulence. The proposed model with the split equations for turbulence characteristics is similar to the contemporary differential turbulence models, concerning the physical formulations. At the same time, its algorithm has high enough computational efficiency. Parameterizations with using the split turbulence model make it possible to obtain more adequate structure of temperature and salinity at decadal timescales, compared to the simpler Pacanowski-Philander (PP) turbulence parameterization. Parameterizations with using analytical solution or numerical scheme at the generation-dissipation step of the turbulence model leads to better representation of ocean climate than the faster parameterization using the asymptotic behavior of the analytical solution. At the same time, the computational efficiency left almost unchanged relative to the simple PP parameterization. Usage of PP parametrization in the circulation model leads to realistic simulation of density and circulation with violation of T,S-relationships. This error is majorly avoided with using the proposed parameterizations containing the split turbulence model

  14. Continental and oceanic crustal magnetization modelling

    NASA Technical Reports Server (NTRS)

    Harrison, C. G. A.; Hayling, K. L.

    1984-01-01

    Inversion of magnetic data from the MAGSAT satellite, to arrive at intensities of magnetization of the Earth's crust, was performed by two different methods. The first method uses a spherical harmonic model of the magnetic field. The coefficients believed to represent sources in the Earth's crust can then be inverted to arrive at vertical dipole moments per unit area at the Earth's surface. The spherical harmonic models contain coefficients of degrees of harmonics up to 23. The dipole moment per unit area for a surface element can then be determined by summing the contribution for each individual degree of harmonic. The magnetic moments were calculated for continental and oceanic areas separately as well as over certain latitudinal segments. Of primary concern was to determine whether there are any differences between continental and oceanic areas. The second analysis with magnetization intensities was made using narrower ranges of degrees of harmonics, assuming that higher degrees are present in the core field signal.

  15. Sonar signal processing using probabilistic signal and ocean environmental models.

    PubMed

    Culver, R Lee; Camin, H John

    2008-12-01

    Acoustic signals propagating through the ocean are refracted, scattered, and attenuated by the ocean volume and boundaries. Many aspects of how the ocean affects acoustic propagation are understood, such that the characteristics of a received signal can often be predicted with some degree of certainty. However, acoustic ocean parameters vary with time and location in a manner that is not, and cannot be, precisely known; some uncertainty will always remain. For this reason, the characteristics of the received signal can never be precisely predicted and must be described in probabilistic terms. A signal processing structure recently developed relies on knowledge of the ocean environment to predict the statistical characteristics of the received signal, and incorporates this description into the processor in order to detect and classify targets. Acoustic measurements at 250 Hz from the 1996 Strait of Gibraltar Acoustic Monitoring Experiment are used to illustrate how the processor utilizes environmental data to classify source depth and to underscore the importance of environmental model fidelity and completeness.

  16. NCAR CSM ocean model by the NCAR oceanography section. Technical note

    SciTech Connect

    1996-05-01

    This technical note documents the ocean component of the NCAR Climate System Model (CSM). The ocean code has been developed from the Modular Ocean Model (version 1.1) which was developed and maintained at the NOAA Geophysical Fluid Dynamics Laboratory in Princeton. As a tribute to Mike Cox, and because the material is still relevant, the first four sections of this technical note are a straight reproduction from the GFDL Technical Report that Mike wrote in 1984. The remaining sections document how the NCAR Oceanography Section members have developed the MOM 1.1 code, and how it is forced, in order to produce the NCAR CSM Ocean Model.

  17. Ocean modelling aspects for drift applications

    NASA Astrophysics Data System (ADS)

    Stephane, L.; Pierre, D.

    2010-12-01

    Nowadays, many authorities in charge of rescue-at-sea operations lean on operational oceanography products to outline research perimeters. Moreover, current fields estimated with sophisticated ocean forecasting systems can be used as input data for oil spill/ adrift object fate models. This emphasises the necessity of an accurate sea state forecast, with a mastered level of reliability. This work focuses on several problems inherent to drift modeling, dealing in the first place with the efficiency of the oceanic current field representation. As we want to discriminate the relevance of a particular physical process or modeling option, the idea is to generate series of current fields of different characteristics and then qualify them in term of drift prediction efficiency. Benchmarked drift scenarios were set up from real surface drifters data, collected in the Mediterranean sea and off the coasts of Angola. The time and space scales that we are interested in are about 72 hr forecasts (typical timescale communicated in case of crisis), for distance errors that we hope about a few dozen of km around the forecast (acceptable for reconnaissance by aircrafts) For the ocean prediction, we used some regional oceanic configurations based on the NEMO 2.3 code, nested into Mercator 1/12° operational system. Drift forecasts were computed offline with Mothy (Météo France oil spill modeling system) and Ariane (B. Blanke, 1997), a Lagrangian diagnostic tool. We were particularly interested in the importance of the horizontal resolution, vertical mixing schemes, and any processes that may impact the surface layer. The aim of the study is to ultimately point at the most suitable set of parameters for drift forecast use inside operational oceanic systems. We are also motivated in assessing the relevancy of ensemble forecasts regarding determinist predictions. Several tests showed that mis-described observed trajectories can finally be modelled statistically by using uncertainties

  18. Warm Bias and Parameterization of Boundary Upwelling in Ocean Models

    SciTech Connect

    Cessi, Paola; Wolfe, Christopher

    2012-11-06

    It has been demonstrated that Eastern Boundary Currents (EBC) are a baroclinic intensification of the interior circulation of the ocean due to the emergence of mesoscale eddies in response to the sharp buoyancy gradients driven by the wind-stress and the thermal surface forcing. The eddies accomplish the heat and salt transport necessary to insure that the subsurface flow is adiabatic, compensating for the heat and salt transport effected by the mean currents. The EBC thus generated occurs on a cross-shore scale of order 20-100 km, and thus this scale needs to be resolved in climate models in order to capture the meridional transport by the EBC. Our result indicate that changes in the near shore currents on the oceanic eastern boundaries are linked not just to local forcing, such as coastal changes in the winds, but depend on the basin-wide circulation as well.

  19. A PARALLEL IMPLEMENTATION OF A SPECTRAL ELEMENT OCEAN MODEL FOR SIMULATING LOW-LATITUDE CIRCULATION SYSTEM

    SciTech Connect

    MA,H.; MCCAFFREY,J.; PIACSEK,S.

    1997-11-01

    This paper is about the parallel implementation of a high-resolution, spectral element, primitive equation model of a homogeneous equatorial ocean. The present work shows that the high-order domain decomposition methods can be efficiently implemented in a massively parallel computing environment to solve large-scale CFD problems, such as the general circulation of the ocean.

  20. Global ocean modeling on the Connection Machine

    SciTech Connect

    Smith, R.D.; Dukowicz, J.K.; Malone, R.C.

    1993-10-01

    The authors have developed a version of the Bryan-Cox-Semtner ocean model (Bryan, 1969; Semtner, 1976; Cox, 1984) for massively parallel computers. Such models are three-dimensional, Eulerian models that use latitude and longitude as the horizontal spherical coordinates and fixed depth levels as the vertical coordinate. The incompressible Navier-Stokes equations, with a turbulent eddy viscosity, and mass continuity equation are solved, subject to the hydrostatic and Boussinesq approximations. The traditional model formulation uses a rigid-lid approximation (vertical velocity = 0 at the ocean surface) to eliminate fast surface waves. These waves would otherwise require that a very short time step be used in numerical simulations, which would greatly increase the computational cost. To solve the equations with the rigid-lid assumption, the equations of motion are split into two parts: a set of twodimensional ``barotropic`` equations describing the vertically-averaged flow, and a set of three-dimensional ``baroclinic`` equations describing temperature, salinity and deviations of the horizontal velocities from the vertically-averaged flow.

  1. North Atlantic Finite Element Ocean Modeling

    NASA Astrophysics Data System (ADS)

    Veluthedathekuzhiyil, Praveen

    This thesis presents a modified version of the Finite Element Ocean Model (FEOM) developed at Alfred Wegener Institute for Polar and Marine Research (AWI) for the North Atlantic Ocean. A reasonable North Atlantic Ocean simulation is obtained against the observational data sets in a Control simulation (CS) where the surface boundary conditions are relaxed to a climatology. The vertical mixing in the model was tuned to represent convection in the model, also the horizontal mixing and diffusion coefficients to represent the changes in the resolution of the model’s unstructured grid. In addition, the open boundaries in the model are treated with a sponge layer where tracers are relaxed to climatology. The model is then further modified to accept the atmospheric flux forcing at the surface boundary with an added net heat flux correction and freshwater forcing from major rivers that are flowing into the North Atlantic Ocean. The impact of this boundary condition on the simulation results is then analyzed and shows many improvements albeit the drift in tracer properties around the Gulf Stream region remains as that of the CS case. However a comparison of the vertical sections at Cape Desolation and Cape Farewell with the available observational data sets shows many improvements in this simulation compared to that of the CS case. But the freshwater content in the Labrador Sea interior shows a continued drift as that of the CS case with an improvement towards the 10th model year. A detailed analysis of the boundary currents around the Labrador Sea shows the weak offshore transport of freshwater from the West Greenland Current (WGC) as one of the causes. To further improve the model and reasonably represent the boundary currents and associated sub-grid scale eddies in the model, a modified sub-grid scale parameterization based on Gent and McWilliams, (1990) is adopted. The sensitivity of using various approaches in the thickness diffusion parameter ( Kgm) for this

  2. Ocean forecasting in terrain-following coordinates: Formulation and skill assessment of the Regional Ocean Modeling System

    USGS Publications Warehouse

    Haidvogel, D.B.; Arango, H.; Budgell, W.P.; Cornuelle, B.D.; Curchitser, E.; Di, Lorenzo E.; Fennel, K.; Geyer, W.R.; Hermann, A.J.; Lanerolle, L.; Levin, J.; McWilliams, J.C.; Miller, A.J.; Moore, A.M.; Powell, T.M.; Shchepetkin, A.F.; Sherwood, C.R.; Signell, R.P.; Warner, J.C.; Wilkin, J.

    2008-01-01

    Systematic improvements in algorithmic design of regional ocean circulation models have led to significant enhancement in simulation ability across a wide range of space/time scales and marine system types. As an example, we briefly review the Regional Ocean Modeling System, a member of a general class of three-dimensional, free-surface, terrain-following numerical models. Noteworthy characteristics of the ROMS computational kernel include: consistent temporal averaging of the barotropic mode to guarantee both exact conservation and constancy preservation properties for tracers; redefined barotropic pressure-gradient terms to account for local variations in the density field; vertical interpolation performed using conservative parabolic splines; and higher-order, quasi-monotone advection algorithms. Examples of quantitative skill assessment are shown for a tidally driven estuary, an ice-covered high-latitude sea, a wind- and buoyancy-forced continental shelf, and a mid-latitude ocean basin. The combination of moderate-order spatial approximations, enhanced conservation properties, and quasi-monotone advection produces both more robust and accurate, and less diffusive, solutions than those produced in earlier terrain-following ocean models. Together with advanced methods of data assimilation and novel observing system technologies, these capabilities constitute the necessary ingredients for multi-purpose regional ocean prediction systems. ?? 2007 Elsevier Inc. All rights reserved.

  3. Modeling and Assimilating Ocean Color Radiances

    NASA Technical Reports Server (NTRS)

    Gregg, Watson

    2012-01-01

    Radiances are the source of information from ocean color sensors to produce estimates of biological and geochemical constituents. They potentially provide information on various other aspects of global biological and chemical systems, and there is considerable work involved in deriving new information from these signals. Each derived product, however, contains errors that are derived from the application of the radiances, above and beyond the radiance errors. A global biogeochemical model with an explicit spectral radiative transfer model is used to investigate the potential of assimilating radiances. The results indicate gaps in our understanding of radiative processes in the oceans and their relationships with biogeochemical variables. Most important, detritus optical properties are not well characterized and produce important effects of the simulated radiances. Specifically, there does not appear to be a relationship between detrital biomass and its optical properties, as there is for chlorophyll. Approximations are necessary to get beyond this problem. In this reprt we will discuss the challenges in modeling and assimilation water-leaving radiances and the prospects for improving our understanding of biogeochemical process by utilizing these signals.

  4. Atmosphere-magma ocean modeling of GJ 1132 b

    NASA Astrophysics Data System (ADS)

    Schaefer, Laura; Wordsworth, Robin; Berta-Thompson, Zachory K.; Sasselov, Dimitar

    2017-01-01

    GJ 1132 b is a nearby Earth-sized exoplanet transiting an M dwarf, and is amongst the most highly characterizable small exoplanets currently known. Using a coupled atmosphere-magma ocean model, we determine that GJ 1132 b must have begun with more than 5 wt% initial water in order to still retain a water-based atmosphere. We also determine the amount of O2 that can build up in the atmosphere as a result of hydrogen dissociation and loss. We find that the magma ocean absorbs at most ~ 10% of the O2 produced, whereas more than 90% is lost to space through hydrodynamic drag. The results of the model depend strongly on the initial water abundance and the XUV model. The most common outcome for GJ 1132 b from our simulations is a tenuous atmosphere dominated by O2, although for very large initial water abundances, atmospheres with several thousands of bars of O2 are possible. A substantial steam envelope would indicate either the existence of an earlier H2 envelope or low XUV flux over the system's lifetime. A steam atmosphere would also imply the continued existence of a magma ocean on GJ 1132 b. Preliminary modeling with the addition of CO2 gas will be presented.

  5. Interactive Visual Analysis within Dynamic Ocean Models

    NASA Astrophysics Data System (ADS)

    Butkiewicz, T.

    2012-12-01

    The many observation and simulation based ocean models available today can provide crucial insights for all fields of marine research and can serve as valuable references when planning data collection missions. However, the increasing size and complexity of these models makes leveraging their contents difficult for end users. Through a combination of data visualization techniques, interactive analysis tools, and new hardware technologies, the data within these models can be made more accessible to domain scientists. We present an interactive system that supports exploratory visual analysis within large-scale ocean flow models. The currents and eddies within the models are illustrated using effective, particle-based flow visualization techniques. Stereoscopic displays and rendering methods are employed to ensure that the user can correctly perceive the complex 3D structures of depth-dependent flow patterns. Interactive analysis tools are provided which allow the user to experiment through the introduction of their customizable virtual dye particles into the models to explore regions of interest. A multi-touch interface provides natural, efficient interaction, with custom multi-touch gestures simplifying the otherwise challenging tasks of navigating and positioning tools within a 3D environment. We demonstrate the potential applications of our visual analysis environment with two examples of real-world significance: Firstly, an example of using customized particles with physics-based behaviors to simulate pollutant release scenarios, including predicting the oil plume path for the 2010 Deepwater Horizon oil spill disaster. Secondly, an interactive tool for plotting and revising proposed autonomous underwater vehicle mission pathlines with respect to the surrounding flow patterns predicted by the model; as these survey vessels have extremely limited energy budgets, designing more efficient paths allows for greater survey areas.

  6. Modeling Coccolithophores in the Global Oceans

    NASA Astrophysics Data System (ADS)

    Gregg, W.

    2006-12-01

    Coccolithophores are important ecological and geochemical components of the global oceans. A global three- dimensional model was used to simulate their distributions in a multi-phytoplankton context. The realism of the simulation was supported by comparisons of model surface nutrients and total chlorophyll with in situ and satellite observations. Nitrate, silica, and dissolved iron surface distributions were positively correlated with in situ data across major oceanographic basins. Global annual departures were +18.9% for nitrate (model high), +5.4% for silica, and +45.0% for iron. Total surface chlorophyll was also positively correlated with satellite and in situ data sets across major basins. Global annual departures were -8.0% with SeaWiFS (model low), +1.1% with Aqua, and -17.1% with in situ data. Global annual primary production estimates were within 1% and 9% of estimates derived from SeaWiFS and Aqua, respectively, using a common primary production algorithm. Coccolithophore annual mean relative abundances were 2.6% lower than observations, but were positively correlated across basins. Two of the other three phytoplankton groups, diatoms and cyanobacteria, were also positively correlated with observations. Distributions of coccolithophores were dependent upon interactions and competition with the other phytoplankton groups. In this model coccolithophores had a competitive advantage over diatoms and chlorophytes by virtue of a greater ability to utilize nutrients and light at low values. However, their higher sinking rates placed them at a disadvantage when nutrients and light were plentiful. In very low nutrient conditions, such as the mid-ocean gyres, coccolithophores were unable to compete with the efficient nutrient utilization capability and low sinking rate of cyanobacteria. Comparisons of simulated coccolithophore distributions with satellite-derived estimates of calcite concentration and coccolithophore blooms showed some agreement, but also areas of

  7. Modeling coccolithophores in the global oceans

    NASA Astrophysics Data System (ADS)

    Gregg, Watson W.; Casey, Nancy W.

    2007-03-01

    Coccolithophores are important ecological and geochemical components of the global oceans. A global three-dimensional model was used to simulate their distributions in a multi-phytoplankton context. The realism of the simulation was supported by comparisons of model surface nutrients and total chlorophyll with in situ and satellite observations. Nitrate, silica, and dissolved iron surface distributions were positively correlated with in situ data across major oceanographic basins. Global annual departures were +18.9% for nitrate (model high), +5.4% for silica, and +45.0% for iron. Total surface chlorophyll was also positively correlated with satellite and in situ data sets across major basins. Global annual departures were -8.0% with Sea-viewing Wide Field-of-view Sensor (SeaWiFS) (model low), +1.1% with Aqua, and -17.1% with in situ data. Global annual primary production estimates were within 1% and 9% of estimates derived from SeaWiFS and Aqua, respectively, using a common primary production algorithm. Coccolithophore annual mean relative abundances were 2.6% lower than observations, but were positively correlated across basins. Two of the other three phytoplankton groups, diatoms and cyanobacteria, were also positively correlated with observations. Distributions of coccolithophores were dependent upon interactions and competition with the other phytoplankton groups. In this model, coccolithophores had a competitive advantage over diatoms and chlorophytes by virtue of a greater ability to utilize nutrients and light at low values. However, their higher sinking rates placed them at a disadvantage when nutrients and light were plentiful. In very low nutrient conditions, such as the mid-ocean gyres, coccolithophores were unable to compete with the efficient nutrient utilization capability and low sinking rate of cyanobacteria. Comparisons of simulated coccolithophore distributions with satellite-derived estimates of calcite concentration and coccolithophore blooms

  8. Response Of Ocean Carbon Export To Different Model Algorithms

    NASA Astrophysics Data System (ADS)

    Caglar Yumruktepe, Veli; Salihoglu, Baris; Kideys, Ahmet E.

    2013-04-01

    Effects of climate change on the biological carbon pump (BCP) and vice-versa, and the influence of change in ecosystem structure on the dynamics of BCP are vital topics to understand the role of oceans in the global carbon cycle and sequestration of greenhouse gases. Construction of a complete carbon budget, requires better understanding of air-sea exchanges and the processes controlling the vertical and horizontal transport of carbon in the ocean, particularly the biological carbon pump. Improved parameterization of carbon sequestration within ecosystem models is vital to better understand and predict changes in the global carbon cycle. However, due to the complexity of processes controlling particle aggregation, sinking and decomposition, existing ecosystem models necessarily parameterize carbon sequestration using simple algorithms. For this reason, the primary aim of this study is to provide new parameterizations of the downward flux of organic carbon, suitable for inclusion in numerical models. The study area was chosen to be the North Atlantic Basin (NA) and the surrounding shelf seas. In the scope of this study, first, the skill of existing models in representing particle fluxes were compared theoretically. The unique algorithms used in three state-of-the art ecosystem models ERSEM, PISCES and MEDUSA have been compared and tested against observational data collected at the PAP mooring site. For testing purposes, algorithms were inserted into a common 1D pelagic ecosystem model. Following comparison of existing algorithms, new experimental results obtained from targeted mesocosm experiments and open ocean observations, will be utilized to develop improved formulations. New algorithms will be compared to existing model formulations using a standard validation data set complied within the framework of BASIN. In order to assess algorithm response under differing hydrographic environments, each set of algorithms will be tested within a 1D framework at three sites

  9. Numerical noise in ocean and estuarine models

    USGS Publications Warehouse

    Walters, R.; Carey, G.F.

    1984-01-01

    Approximate methods for solving the shallow water equations may lead to solutions exhibiting large fictitious, numerically-induced oscillations. The analysis of the discrete dispersion relation and modal solutions of small wavelengths provides a powerful technique for assessing the sensitivity of alternative numerical schemes to irregular data which may lead to such oscillatory numerical noise. For those schemes where phase speed vanishes at a finite wavenumber or there are multiple roots for wavenumber, oscillation modes can exist which are uncoupled from the dynamics of the problem. The discrete modal analysis approach is used here to identify two classes of spurious oscillation modes associated respectively with the two different asymptotic limits corresponding to estuarine and large scale ocean models. The analysis provides further insight into recent numerical results for models which include large spatial scales and Coriolis acceleration. ?? 1984.

  10. Evaluating the deep-ocean circulation of a global ocean model using carbon isotopic ratios

    NASA Astrophysics Data System (ADS)

    Paul, André; Dutkiewicz, Stephanie; Gebbie, Jake; Losch, Martin; Marchal, Olivier

    2016-04-01

    We study the sensitivity of a global three-dimensional biotic ocean carbon-cycle model to the parameterizations of gas exchange and biological productivity as well as to deep-ocean circulation strength, and we employ the carbon isotopic ratios δ13C and Δ14C of dissolved inorganic carbon for a systematic evaluation against observations. Radiocarbon (Δ14C) in particular offers the means to assess the model skill on a time scale of 100 to 1000 years relevant to the deep-ocean circulation. The carbon isotope ratios are included as tracers in the MIT general circulation model (MITgcm). The implementation involves the fractionation processes during photosynthesis and air-sea gas exchange. We present the results of sixteen simulations combining two different parameterizations of the piston velocity, two different parameterizations of biological productivity (including the effect of iron fertilization) and four different overturning rates. These simulations were first spun up to equilibrium (more than 10,000 years of model simulation) and then continued from AD 1765 to AD 2002. For the model evaluation, we followed the OCMIP-2 (Ocean Carbon-Cycle Model Intercomparision Project phase two) protocol, comparing the results to GEOSECS (Geochemical Ocean Sections Survey) and WOCE (World Ocean Circulation Experiment) δ13C and natural Δ14C data in the world ocean. The range of deep natural Δ14C (below 1000 m) for our single model (MITgcm) was smaller than for the group of different OCMIP-2 models. Furthermore, differences between different model parameterizations were smaller than for different overturning rates. We conclude that carbon isotope ratios are a useful tool to evaluate the deep-ocean circulation. Since they are also available from deep-sea sediment records, we postulate that the simulation of carbon isotope ratios in a global ocean model will aid in estimating the deep-ocean circulation and climate during present and past.

  11. Ocean circulation modeling by use of radar altimeter data

    NASA Technical Reports Server (NTRS)

    Olbers, Dirk; Alpers, W.; Hasselmann, K.; Maier-Reimer, E.; Kase, R.; Krauss, W.; Siedler, G.; Willebrand, J.; Zahel, W.

    1991-01-01

    The project will investigate the use of radar altimetry (RA) data in the determination of the ocean circulation models. RA data will be used to verify prognostic experiments of the steady state and seasonal cycle of large-scale circulation models and the statistical steady state of eddy-resolving models. The data will serve as initial and update conditions in data assimilation experiments and as constraints in inverse calculations. The aim of the project is a better understanding of ocean physics, the determination and mapping of ocean currents, and a contribution to the establishment of ocean circulation models for climate studies. The goal of the project is to use satellite radar altimetry data for improving our knowledge of ocean circulation both in a descriptive sense and through the physics that govern the circulation state. The basic tool is a series of ocean circulation models. Depending on the model, different techniques will be applied to incorporate the RA data.

  12. Submesoscale Flows and Mixing in the Ocean Surface Layer Using the Regional Oceanic Modeling System (ROMS)

    DTIC Science & Technology

    2013-09-30

    DISTRIBUTION A: Approved for public release; distribution unlimited. Submesoscale Flows and Mixing in the Ocean Surface Layer Using the Regional...long-term goals of this project are to further the insight into the dynamics of submesoscale flow in the oceanic surface layer. Using the regional...oceanic modeling system (ROMS) we aim to understand the impact of submesoscale processes on the mixing at small scales of tracers and the transfer of

  13. An update on modeling land-ice/ocean interactions in CESM

    SciTech Connect

    Asay-davis, Xylar

    2011-01-24

    This talk is an update on ongoing land-ice/ocean coupling work within the Community Earth System Model (CESM). The coupling method is designed to allow simulation of a fully dynamic ice/ocean interface, while requiring minimal modification to the existing ocean model (the Parallel Ocean Program, POP). The method makes use of an immersed boundary method (IBM) to represent the geometry of the ice-ocean interface without requiring that the computational grid be modified in time. We show many of the remaining development challenges that need to be addressed in order to perform global, century long climate runs with fully coupled ocean and ice sheet models. These challenges include moving to a new grid where the computational pole is no longer at the true south pole and several changes to the coupler (the software tool used to communicate between model components) to allow the boundary between land and ocean to vary in time. We discuss benefits for ice/ocean coupling that would be gained from longer-term ocean model development to allow for natural salt fluxes (which conserve both water and salt mass, rather than water volume).

  14. Carbon isotopes in the ocean model of the Community Earth System Model (CESM1)

    NASA Astrophysics Data System (ADS)

    Jahn, A.; Lindsay, K.; Giraud, X.; Gruber, N.; Otto-Bliesner, B. L.; Liu, Z.; Brady, E. C.

    2015-08-01

    Carbon isotopes in the ocean are frequently used as paleoclimate proxies and as present-day geochemical ocean tracers. In order to allow a more direct comparison of climate model results with this large and currently underutilized data set, we added a carbon isotope module to the ocean model of the Community Earth System Model (CESM), containing the cycling of the stable isotope 13C and the radioactive isotope 14C. We implemented the 14C tracer in two ways: in the "abiotic" case, the 14C tracer is only subject to air-sea gas exchange, physical transport, and radioactive decay, while in the "biotic" version, the 14C additionally follows the 13C tracer through all biogeochemical and ecological processes. Thus, the abiotic 14C tracer can be run without the ecosystem module, requiring significantly fewer computational resources. The carbon isotope module calculates the carbon isotopic fractionation during gas exchange, photosynthesis, and calcium carbonate formation, while any subsequent biological process such as remineralization as well as any external inputs are assumed to occur without fractionation. Given the uncertainty associated with the biological fractionation during photosynthesis, we implemented and tested three parameterizations of different complexity. Compared to present-day observations, the model is able to simulate the oceanic 14C bomb uptake and the 13C Suess effect reasonably well compared to observations and other model studies. At the same time, the carbon isotopes reveal biases in the physical model, for example, too sluggish ventilation of the deep Pacific Ocean.

  15. Development and Utilization of the Regional Oceanic Modeling System (ROMS)

    DTIC Science & Technology

    2008-09-30

    simulation studies with the Regional Oceanic Modeling System (ROMS). The targeted problems are submesoscale wakes, fronts, and eddies; nearshore currents...2005: Routes to dissipation in the ocean: The 2D/3D turbulence conundrum. In: Marine Turbulence : Theories, Observations, and Models , Eds. H...Development and Utilization of the Regional Oceanic Modeling System (ROMS) James C. McWilliams Department of Atmospheric Sciences and Institute

  16. Oceanic radiance model development and validation: application of airborne active-passive ocean color spectral measurements.

    PubMed

    Hoge, F E; Swift, R; Yungel, J

    1995-06-20

    It is shown that airborne active-passive (laser-solar) ocean color data can be used to develop and validate oceanic radiance models. The two principal inputs to the oceanic radiance model, chlorophyll pigment and incident solar irradiance, are obtained from a nadir-viewing laser-induced fluorescence spectrometer and a zenith-viewing radiometer, respectively. The computed water-leaving radiances are validated by comparison with the calibrated output of a separate nadir-viewing radiometer subsystem. In the North Atlantic Ocean, the calculated and the observed airborne radiances are found to compare very favorably for the 443-, 520-, and 550-nm wavelengths over an ∼ 170-km flight track east of St. John's, Newfoundland. The results further suggest that the semianalytical radiance model of ocean color, the airborne active (laser) fluorescence spectrometer, and the passive (solar) radiometric instrumentation are all remarkably precise.

  17. Whither low-order climate models?

    NASA Astrophysics Data System (ADS)

    Viebahn, Jan; Dijkstra, Henk A.

    2015-04-01

    A zoo of low-order (small degrees of freedom) deterministic and stochastic climate models has appeared in the literature with each focussing on specific aspects of (paleo)climate variability. The advantage of these models is that their behavior can be analyzed in detail and hence cause and effect (mechanisms) can be disentangled efficiently. Indeed, much insight has been obtained by `thinking deep about simple models'. However, the disadvantage is that each model usually contains idealizations and severe approximations such that the mechanisms underlying a certain phenomenon in these models may not represent the mechanisms which are at work in more detailed models and in observations. The danger is thus that low-order model results will be ignored by many of the climate science community. In this presentation, focus will be on several issues related to the use of low-order model results. Did the results of these models contribute to a better understanding of observed climate variability or did they only aggravate the confusion about cause and effect? In the spirit of `essentially all models are wrong but some are useful' (George Box), which type of models (e.g. stochastic versus deterministic, ad hoc versus truncated, etc.) has been more useful than others (has been the best fit for purpose)? Does this provide future guidelines on the development and usage of these models? Example models and their results will serve to address these issues.

  18. Diurnal ocean surface layer model validation

    NASA Technical Reports Server (NTRS)

    Hawkins, Jeffrey D.; May, Douglas A.; Abell, Fred, Jr.

    1990-01-01

    The diurnal ocean surface layer (DOSL) model at the Fleet Numerical Oceanography Center forecasts the 24-hour change in a global sea surface temperatures (SST). Validating the DOSL model is a difficult task due to the huge areas involved and the lack of in situ measurements. Therefore, this report details the use of satellite infrared multichannel SST imagery to provide day and night SSTs that can be directly compared to DOSL products. This water-vapor-corrected imagery has the advantages of high thermal sensitivity (0.12 C), large synoptic coverage (nearly 3000 km across), and high spatial resolution that enables diurnal heating events to be readily located and mapped. Several case studies in the subtropical North Atlantic readily show that DOSL results during extreme heating periods agree very well with satellite-imagery-derived values in terms of the pattern of diurnal warming. The low wind and cloud-free conditions necessary for these events to occur lend themselves well to observation via infrared imagery. Thus, the normally cloud-limited aspects of satellite imagery do not come into play for these particular environmental conditions. The fact that the DOSL model does well in extreme events is beneficial from the standpoint that these cases can be associated with the destruction of the surface acoustic duct. This so-called afternoon effect happens as the afternoon warming of the mixed layer disrupts the sound channel and the propagation of acoustic energy.

  19. Oceanic Excitations On Polar Motion: A Cross Comparison Among Models

    NASA Astrophysics Data System (ADS)

    Zhou, Y.; Chen, J.; Liao, X.; Wilson, C. R.

    2004-12-01

    Recent studies based on various oceanic general circulation models (OGCMs) demonstrated that the oceans are a major contributor to polar motion excitations. In this paper, we analyze and compare observed non-atmospheric polar motion excitations with oceanic angular momentum (OAM) variations determined from four OGCMs, which include the parallel ocean climate model (POCM), a barotropic ocean model (BOM), the Estimating the Circulation and Climate of the Ocean (ECCO) non-data-assimilating model (ECCO-NDA), and the ECCO data-assimilating model (ECCO-DA). The data to be analyzed span a 5-year¡_s overlapped period from 1993 to 1997. At annual time scale, these four OAM estimates do not agree well with each other, while POCM shows relatively larger discrepancies than other three models. At intraseasonal time scales, ECCO-DA yields the best agreement with observations, and reduces the variance of non-atmospheric excitations by about 60%, 10-20% more than those explained by other three models. However, at the very short periods of 4-20 days, the BOM estimates could explain about half of the observed variance, twice as much as that by ECCO-NDA, and also shows considerably better correlation with observations. Due to different modeling schemes and methods, significant discrepancies could arise with respect to the quantity of modeling large-scale oceanic mass redistribution and current variation. A clear understanding of global oceanic contributions to polar motion excitation still remains a challenge.

  20. A fractional-order infectivity SIR model

    NASA Astrophysics Data System (ADS)

    Angstmann, C. N.; Henry, B. I.; McGann, A. V.

    2016-06-01

    Fractional-order SIR models have become increasingly popular in the literature in recent years, however unlike the standard SIR model, they often lack a derivation from an underlying stochastic process. Here we derive a fractional-order infectivity SIR model from a stochastic process that incorporates a time-since-infection dependence on the infectivity of individuals. The fractional derivative appears in the generalised master equations of a continuous time random walk through SIR compartments, with a power-law function in the infectivity. We show that this model can also be formulated as an infection-age structured Kermack-McKendrick integro-differential SIR model. Under the appropriate limit the fractional infectivity model reduces to the standard ordinary differential equation SIR model.

  1. Three-Dimensional Ocean Noise Modeling

    DTIC Science & Technology

    2015-03-01

    tf^NOG^^ WOODS HOLE OCEANOGRAPHIC INSTITUTION Applied Ocean Physics and Engineering Department, Senior Scientist February 27, 2015 Dr. Kyle...Office (WHOI) ONR REG Boston N62879 -J Defense Technical Information Center Naval Research Laboratory MS#12 • Woods Hole, MA 02543 USA...Applied Ocean Physics and Engineering Department Woods Hole Oceanographic Institution, Woods Hole, MA 02542 *now at: Department of Oceanography

  2. Iron supply to the Southern Ocean mixed layer from below; the ocean model effect

    NASA Astrophysics Data System (ADS)

    Schourup-Kristensen, Vibe; Hauck, Judith; Losch, Martin; Wolf-Gladrow, Dieter A.; Völker, Christoph

    2015-04-01

    In the iron limited Southern Ocean, the biogeochemical results of commonly used ocean general circulation biogeochemical models differ greatly dependent on the ocean model used. This is largely due to the difficulties in reproducing a realistic mixed layer depth (MLD), which leads to different degrees of light limitation and nutrient supply from below. Regarding the iron sources to the Southern Ocean, research has traditionally focused on the input from dust and the sediment, but recent studies have highlighted the importance of the vertical supply to the mixed layer from the nutrient rich deeper water. This latter supply mechanism may also be affected by the large inter-model differences in the MLD and thereby influence the total net primary production and export production in the models. We have performed a model study in which the biogeochemical model REcoM2 was coupled to two different ocean models, the Finite Element Sea-ice Ocean Model (FESOM) and the MIT general circulation model (MITgcm). The effect of the ocean mixed layer on the magnitude of the iron sources from below in the two models was analyzed, as was the effect on the export and net primary production. Our results revealed a remarkable difference in terms of mode and magnitude of transport dependent on the mixed layer depth in the two models; the mean iron supply from below in the Southern Ocean was on average four times higher in MITgcm than in FESOM. The dominant pathway was entrainment in MITgcm, whereas diffusion dominated in FESOM. We discuss how the difference in the depth and seasonal amplitude of the mixed layer between the models has a major effect on the vertical iron profile and thereby also on the iron fluxes. A further effect of the difference in supply is that the fraction of exported net primary production is higher in MITgcm than in FESOM, showing that the choice of ocean model has a significant impact on the modeled carbon cycle in the Southern Ocean, with possible implications for

  3. Including eddies in global ocean models

    NASA Astrophysics Data System (ADS)

    Semtner, Albert J.; Chervin, Robert M.

    The ocean is a turbulent fluid that is driven by winds and by surface exchanges of heat and moisture. It is as important as the atmosphere in governing climate through heat distribution, but so little is known about the ocean that it remains a “final frontier” on the face of the Earth. Many ocean currents are truly global in extent, such as the Antarctic Circumpolar Current and the “conveyor belt” that connects the North Atlantic and North Pacific oceans by flows around the southern tips of Africa and South America. It has long been a dream of some oceanographers to supplement the very limited observational knowledge by reconstructing the currents of the world ocean from the first principles of physics on a computer. However, until very recently, the prospect of doing this was thwarted by the fact that fluctuating currents known as “mesoscale eddies” could not be explicitly included in the calculation.

  4. A Coupled Ocean General Circulation, Biogeochemical, and Radiative Model of the Global Oceans: Seasonal Distributions of Ocean Chlorophyll and Nutrients

    NASA Technical Reports Server (NTRS)

    Gregg, Watson W.; Busalacchi, Antonio (Technical Monitor)

    2000-01-01

    A coupled ocean general circulation, biogeochemical, and radiative model was constructed to evaluate and understand the nature of seasonal variability of chlorophyll and nutrients in the global oceans. Biogeochemical processes in the model are determined from the influences of circulation and turbulence dynamics, irradiance availability. and the interactions among three functional phytoplankton groups (diatoms. chlorophytes, and picoplankton) and three nutrients (nitrate, ammonium, and silicate). Basin scale (greater than 1000 km) model chlorophyll results are in overall agreement with CZCS pigments in many global regions. Seasonal variability observed in the CZCS is also represented in the model. Synoptic scale (100-1000 km) comparisons of imagery are generally in conformance although occasional departures are apparent. Model nitrate distributions agree with in situ data, including seasonal dynamics, except for the equatorial Atlantic. The overall agreement of the model with satellite and in situ data sources indicates that the model dynamics offer a reasonably realistic simulation of phytoplankton and nutrient dynamics on synoptic scales. This is especially true given that initial conditions are homogenous chlorophyll fields. The success of the model in producing a reasonable representation of chlorophyll and nutrient distributions and seasonal variability in the global oceans is attributed to the application of a generalized, processes-driven approach as opposed to regional parameterization and the existence of multiple phytoplankton groups with different physiological and physical properties. These factors enable the model to simultaneously represent many aspects of the great diversity of physical, biological, chemical, and radiative environments encountered in the global oceans.

  5. Southern Ocean bottom water characteristics in CMIP5 models

    NASA Astrophysics Data System (ADS)

    Heuzé, CéLine; Heywood, Karen J.; Stevens, David P.; Ridley, Jeff K.

    2013-04-01

    Southern Ocean deep water properties and formation processes in climate models are indicative of their capability to simulate future climate, heat and carbon uptake, and sea level rise. Southern Ocean temperature and density averaged over 1986-2005 from 15 CMIP5 (Coupled Model Intercomparison Project Phase 5) climate models are compared with an observed climatology, focusing on bottom water. Bottom properties are reasonably accurate for half the models. Ten models create dense water on the Antarctic shelf, but it mixes with lighter water and is not exported as bottom water as in reality. Instead, most models create deep water by open ocean deep convection, a process occurring rarely in reality. Models with extensive deep convection are those with strong seasonality in sea ice. Optimum bottom properties occur in models with deep convection in the Weddell and Ross Gyres. Bottom Water formation processes are poorly represented in ocean models and are a key challenge for improving climate predictions.

  6. Use of Envisat RA2 Sea Level Observations in the Bluelink Ocean Modelling System

    NASA Astrophysics Data System (ADS)

    Griffin, David A.; Oke, Peter R.; Cahill, Madeline L.

    2010-12-01

    Satellite and in-situ components of the Global Ocean Observing System are assimilated into the Bluelink mesoscale-resolving global ocean model in order to produce both hindcasts and forecasts of the three- dimensional physical state of the ocean. Sea level anomaly estimates provided by the RA2 altimeter embarked on Envisat are an essential inclusion (along with data from Jason-1 and -2) in the data set. We show that with three altimeters in use, the basic features of many rapidly evolving mesoscale features can successfully be simulated in a global ocean model. This has been verified using un-assimilated surface-drifting buoys, and other data. Many successful applications of the system have now been made. Here, we describe how the search for a WWII wreck off Brisbane was assisted by information on ocean currents, and discuss an interesting case of coastal water temperatures near Sydney exceeding climatology by 4o in May 2010.

  7. Assimilation of geodetic dynamical ocean topography data into ocean circulation model

    NASA Astrophysics Data System (ADS)

    Janjic, Tijana; Schroeter, Jens; Albertella, Alberta; Bosch, Wolfgang; Rummel, Reiner; Savcenko, Roman

    Estimation of ocean circulation via assimilation of satellite measurements of dynamical ocean topography (DOT) into the global finite-element ocean model (FEOM) is investigated. The DOT was obtained by means of geodetic approach from carefully cross-calibrated multi-mission-altimeter data and GRACE gravity fields. The spectral consistency was achieved by means of the filtering applied on sea surface and geoid. Since the dynamical ocean topography is obtained from data types coming from different sources, different techniques can be employed for their assimilation into ocean circulation models. For example, the data can be combined and interpolated onto the model grid before they are used in assimilation. In this case special care needs to be taken concerning the specification of observational error statistics. The assimilation is performed by employing the local SEIK filter and various functions for observations error covariance are used. Finally we consider the effects of assimilation on potential temperature field and on steric height changes. Analysed potential temperature is compared with ARGO data. We also compared the standard deviation of the observations and standard deviation of the steric height calculated from the analysis. In many regions of the world ocean there is a good correspondence between these two fields. However also structures that are not present in the observations appear in the steric height standard deviations. Keywords: dynamical ocean topography, data assimilation Session: A2.6

  8. Baroclinic Rossby Wave Signature in a General Circulation Ocean Model.

    DTIC Science & Technology

    1983-06-01

    northwest with a wavelength cf 300 km. For other laritudes of the North acific Ocean , Price and Maqaard (1980) determined that first mode baroclinic Rossby...role in the latitude belt 40-50N in the North acific 10 -. - !o Ocean . Magaard (1983) ir. a paper discussing bariclin _c Rossty wave energetics...HD-AI132 219 BAROCLINIC ROSSBY WAVE SIGNATURE IN A GENERAL CIRCULATION OCEAN MODEL(U) NAVAL POSTGRADUATE SCHOOLU MONTEREY CA A H RUTSCH JUN 83

  9. Optimization of a Parallel Ocean General Circulation Model

    NASA Technical Reports Server (NTRS)

    Chao, Yi

    1997-01-01

    Global climate modeling is one of the grand chalenges of computational science, and ocean modeling plays an important role in both understanding the current climatic conditions and predicting the future climate change.

  10. Ocean Modeling and Visualization on Massively Parallel Computer

    NASA Technical Reports Server (NTRS)

    Chao, Yi; Li, P. Peggy; Wang, Ping; Katz, Daniel S.; Cheng, Benny N.

    1997-01-01

    Climate modeling is one of the grand challenges of computational science, and ocean modeling plays an important role in both understanding the current climatic conditions and predicting future climate change.

  11. Documentation of the Fourth Order Band Model

    NASA Technical Reports Server (NTRS)

    Kalnay-Rivas, E.; Hoitsma, D.

    1979-01-01

    A general circulation model is presented which uses quadratically conservative, fourth order horizontal space differences on an unstaggered grid and second order vertical space differences with a forward-backward or a smooth leap frog time scheme to solve the primitive equations of motion. The dynamic equations for motion, finite difference equations, a discussion of the structure and flow chart of the program code, a program listing, and three relevent papers are given.

  12. Adaptation of a general circulation model to ocean dynamics

    NASA Technical Reports Server (NTRS)

    Turner, R. E.; Rees, T. H.; Woodbury, G. E.

    1976-01-01

    A primitive-variable general circulation model of the ocean was formulated in which fast external gravity waves are suppressed with rigid-lid surface constraint pressires which also provide a means for simulating the effects of large-scale free-surface topography. The surface pressure method is simpler to apply than the conventional stream function models, and the resulting model can be applied to both global ocean and limited region situations. Strengths and weaknesses of the model are also presented.

  13. A Parallel Ocean Model With Adaptive Mesh Refinement Capability For Global Ocean Prediction

    SciTech Connect

    Herrnstein, Aaron R.

    2005-12-01

    An ocean model with adaptive mesh refinement (AMR) capability is presented for simulating ocean circulation on decade time scales. The model closely resembles the LLNL ocean general circulation model with some components incorporated from other well known ocean models when appropriate. Spatial components are discretized using finite differences on a staggered grid where tracer and pressure variables are defined at cell centers and velocities at cell vertices (B-grid). Horizontal motion is modeled explicitly with leapfrog and Euler forward-backward time integration, and vertical motion is modeled semi-implicitly. New AMR strategies are presented for horizontal refinement on a B-grid, leapfrog time integration, and time integration of coupled systems with unequal time steps. These AMR capabilities are added to the LLNL software package SAMRAI (Structured Adaptive Mesh Refinement Application Infrastructure) and validated with standard benchmark tests. The ocean model is built on top of the amended SAMRAI library. The resulting model has the capability to dynamically increase resolution in localized areas of the domain. Limited basin tests are conducted using various refinement criteria and produce convergence trends in the model solution as refinement is increased. Carbon sequestration simulations are performed on decade time scales in domains the size of the North Atlantic and the global ocean. A suggestion is given for refinement criteria in such simulations. AMR predicts maximum pH changes and increases in CO2 concentration near the injection sites that are virtually unattainable with a uniform high resolution due to extremely long run times. Fine scale details near the injection sites are achieved by AMR with shorter run times than the finest uniform resolution tested despite the need for enhanced parallel performance. The North Atlantic simulations show a reduction in passive tracer errors when AMR is applied instead of a uniform coarse resolution. No

  14. Ocean Wave Studies with Applications to Ocean Modeling and Improvement of Satellite Altimeter Measurements

    NASA Technical Reports Server (NTRS)

    Glazman, Roman E.

    1999-01-01

    Combining analysis of satellite data (altimeter, scatterometer, high-resolution visible and infrared images, etc.) with mathematical modeling of non-linear wave processes, we investigate various ocean wave fields (on scales from capillary to planetary), their role in ocean dynamics and turbulent transport (of heat and biogeochemical quantities), and their effects on satellite altimeter measuring accuracy. In 1998 my attention was focused on long internal gravity waves (10 to 1000 km), known also as baroclinic inertia-gravity (BIG) waves. We found these waves to be a major factor of altimeter measurements "noise," resulting in a greater uncertainty [up to 10 cm in terms of sea surface height (SSH) amplitude] in the measured SSH signal than that caused by the sea state bias variations (up to 5 cm or so). This effect still remains largely overlooked by the satellite altimeter community. Our studies of BIG waves address not only their influence on altimeter measurements but also their role in global ocean dynamics and in transport and turbulent diffusion of biogeochemical quantities. In particular, in collaboration with Prof Peter Weichman, Caltech, we developed a theory of turbulent diffusion caused by wave motions of most general nature. Applied to the problem of horizontal turbulent diffusion in the ocean, the theory yielded the effective diffusion coefficient as a function of BIG wave parameters obtainable from satellite altimeter data. This effort, begun in 1997, has been successfully completed in 1998. We also developed a theory that relates spatial fluctuations of scalar fields (such as sea surface temperature, chlorophyll concentration, drifting ice concentration, etc.) to statistical characteristics of BIG waves obtainable from altimeter measurements. A manuscript is in the final stages of preparation. In order to verify the theoretical predictions and apply them to observations, we are now analyzing Sea-viewing Wide Field of view Sensor (SeaWiFS) and Field of

  15. Modern Geodynamic Model of the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Petrov, O.; Sobolev, N.; Morozov, A.; Grikurov, G.; Shokalsky, S.; Kashubin, S.; Petrov, E.

    2012-04-01

    In 2011 at VSEGEI (Russia) within the international project "Atlas of Geological Maps of the Circumpolar Arctic", a draft of the structural tectonic map of the Arctic at 1: 5,000,000 scale was prepared. This map is accompanied by a model of deep lithospheric structure of the Russian Arctic, which reflects thickness, types and specific features of crustal structure, and by geodynamic reconstructions. Analysis of the geological and geophysical data enables distinguishing a set of features in the Arctic evolution: - Differences in geological structure and geodynamic evolution of the Western and Eastern Arctic have been spotted no less than since the Early Paleozoic, which was reflected in the formation of caledonides in the West of the Arctic, and ellesmerides in the East. - In the Middle Paleozoic-Mesozoic (Late Devonian-Early Cretaceous), the eastern parts of the Arctic were affected by geodynamic processes taking place in the Paleo-Pacific. The formation of the Canadian basin was a result of the Late Jurassic-Early Cretaceous riftogenesis. A set of features of this basin - such as constrained spreading, considerable depth and topography of the floor, sedimentation specifics - allows us to consider it as a marginal basin of the Paleo-Pacific that moved into an island-arc evolution stage in the Late Jurassic. Collision orogenic activities that widely manifested themselves in the Northern-Eastern part of Asia on the verge of the Early-Late Cretaceous are related to intraplate riftogenic processes in the Central Arctic that were followed by basic magmatism manifestations in Svalbard, Franz Josef Land and New Siberian Islands. Cretaceous stage of the intraplate riftogenesis determined to a great extent the modern-day structure of the Eastern Arctic. - The opening of the Northern Atlantic was accompanied by tectonic compression in the Eastern parts of the Arctic. The formation of the Eurasian basin was preceded by Late Cretaceous-Paleogene period of amplitude

  16. Net diffusivity in ocean general circulation models with nonuniform grids

    NASA Technical Reports Server (NTRS)

    Yin, F. L.; Fung, I. Y.

    1991-01-01

    The numerical vertical diffusivity K(num), embedded in a numerical ocean general circulation model with nonuniform vertical grid, is estimated. It is shown that in a downwelling region, K(num) is negative for a grid with grid size increasing with depth. When the grid size increment, or the downward vertical velocity, is large, K(num) may exceed the vertical diffusivity specified and may result in a negative effective vertical diffusivity. Therefore care needs to be taken to specify the vertical diffusivity in a numerical model with nonuniform grid, and a lower bound is generally imposed in order to avoid an unphysical negative value. Some possible effects of the negative effective diffusivity are discussed.

  17. GENERAL: Self-organized Criticality Model for Ocean Internal Waves

    NASA Astrophysics Data System (ADS)

    Wang, Gang; Lin, Min; Qiao, Fang-Li; Hou, Yi-Jun

    2009-03-01

    In this paper, we present a simple spring-block model for ocean internal waves based on the self-organized criticality (SOC). The oscillations of the water blocks in the model display power-law behavior with an exponent of -2 in the frequency domain, which is similar to the current and sea water temperature spectra in the actual ocean and the universal Garrett and Munk deep ocean internal wave model [Geophysical Fluid Dynamics 2 (1972) 225; J. Geophys. Res. 80 (1975) 291]. The influence of the ratio of the driving force to the spring coefficient to SOC behaviors in the model is also discussed.

  18. Ocean modeling at multiple resolutions for ISR applications

    NASA Astrophysics Data System (ADS)

    Cathcart, J. Michael; Teague, J. Ralph; Burdette, Ed; Kocher, Brian

    2011-05-01

    Recent research efforts at Georgia Tech have focused on the development of a multi-resolution ocean clutter model. This research was driven by the need to support both surveillance and search requirements set by several government customers. These requirements indicated a need to support target detection and tracking for both resolved and unresolved scenarios for targets located either above or on an ocean surface. As a result of this changing sensor resolution characteristic for the various acquisition scenarios, a need for accurate ocean surface models at different geometric resolutions arose. Georgia Tech met this need through development of a multi-resolution approach to modeling both the ocean surface and, subsequently, the ocean signature across the optical spectrum. This approach combined empirical overhead data with high resolution ocean surface models to construct a series of varying resolution ocean clutter models. This paper will describe the approach to utilizing and merging the various clutter models as well as the results of using these models in the target detection and tracking analysis. Remaining issues associated with this clutter model development will be identified and potential solutions discussed.

  19. Modeling Ocean Ecosystems: The PARADIGM Program

    DTIC Science & Technology

    2006-03-01

    associated life forms. And paradoxically, as we learn more and more about ocean life, for example, through the genomics revolution (Doney et al., 2004...designed to exploit present another challenge to interdis- includes a strong component of retro- new information (e.g., from genomics ), ciplinary ocean...interannual scales-and construct a trient-poor subtropical gyres, the phy- and new molecular and genomic tech- system with enough adaptability to re

  20. Coupled atmosphere-ocean models of Titan's past

    NASA Astrophysics Data System (ADS)

    McKay, C. P.; Pollack, J. B.; Lunine, J. I.; Courtin, R.

    1993-03-01

    The behavior and possible past evolution of fully coupled atmosphere and ocean model of Titan are investigated. It is found that Titan's surface temperature was about 20 K cooler at 4 Gyr ago and will be about 5 K warmer 0.5 Gyr in the future. The change in solar luminosity and the conversion of oceanic CH4 to C2H6 drive the evolution of the ocean and atmosphere over time. Titan appears to have experienced a frozen epoch about 3 Gyr ago independent of whether an ocean is present or not. This finding may have important implications for understanding the inventory of Titan's volatile compounds.

  1. Oceanic excitations on polar motion: a cross comparison among models

    NASA Astrophysics Data System (ADS)

    Zhou, Y. H.; Chen, J. L.; Liao, X. H.; Wilson, C. R.

    2005-08-01

    Recent studies based on various ocean general circulation models (OGCMs) demonstrate that the oceans are a major contributor to polar motion excitations. In this paper, we analyse and compare observed non-atmospheric polar motion excitations with oceanic angular momentum (OAM) variations determined from four OGCMs, which include the parallel ocean climate model (POCM), a barotropic ocean model (BOM), the Estimating the Circulation and Climate of the Ocean (ECCO) non-data-assimilating model (ECCO-NDA) and the ECCO data-assimilating model (ECCO-DA). The data to be analysed span a 5-yr overlapped period from 1993 to 1997. At annual timescale, considerable discrepancies exist between POCM and the other three models, which result mainly from differences in annual components of the forcing wind fields. At semi-annual timescale, however, POCM shows better phase agreement with observed non-atmospheric polar motion excitation than the other three ocean models. At intraseasonal timescales, ECCO-DA yields better agreement with observations, and reduces the variance of non-atmospheric excitations by ~60 per cent, 10-20 per cent more than those explained by the other three models. However, at the very short periods of 4-20 days, the BOM estimates could explain about half of the observed variance, twice as much as that by ECCO-NDA, and also shows considerably better correlation with observations. Due to different modelling schemes and methods, significant discrepancies could arise with respect to the quality of modelling large-scale oceanic mass redistribution and current variation. A complete understanding of global oceanic contributions to polar motion excitation still remains a challenge.

  2. Dynamical models of happiness with fractional order

    NASA Astrophysics Data System (ADS)

    Song, Lei; Xu, Shiyun; Yang, Jianying

    2010-03-01

    This present study focuses on a dynamical model of happiness described through fractional-order differential equations. By categorizing people of different personality and different impact factor of memory (IFM) with different set of model parameters, it is demonstrated via numerical simulations that such fractional-order models could exhibit various behaviors with and without external circumstance. Moreover, control and synchronization problems of this model are discussed, which correspond to the control of emotion as well as emotion synchronization in real life. This study is an endeavor to combine the psychological knowledge with control problems and system theories, and some implications for psychotherapy as well as hints of a personal approach to life are both proposed.

  3. Depths of Intraplate Indian Ocean Earthquakes from Waveform Modeling

    NASA Astrophysics Data System (ADS)

    Baca, A. J.; Polet, J.

    2014-12-01

    The Indian Ocean is a region of complex tectonics and anomalous seismicity. The ocean floor in this region exhibits many bathymetric features, most notably the multiple inactive fracture zones within the Wharton Basin and the Ninetyeast Ridge. The 11 April 2012 MW 8.7 and 8.2 strike-slip events that took place in this area are unique because their rupture appears to have extended to a depth where brittle failure, and thus seismic activity, was considered to be impossible. We analyze multiple intraplate earthquakes that have occurred throughout the Indian Ocean to better constrain their focal depths in order to enhance our understanding of how deep intraplate events are occurring and more importantly determine if the ruptures are originating within a ductile regime. Selected events are located within the Indian Ocean away from major plate boundaries. A majority are within the deforming Indo-Australian tectonic plate. Events primarily display thrust mechanisms with some strike-slip or a combination of the two. All events are between MW5.5-6.5. Event selections were handled this way in order to facilitate the analysis of teleseismic waveforms using a point source approximation. From these criteria we gathered a suite of 15 intraplate events. Synthetic seismograms of direct P-waves and depth phases are computed using a 1-D propagator matrix approach and compared with global teleseismic waveform data to determine a best depth for each event. To generate our synthetic seismograms we utilized the CRUST1.0 software, a global crustal model that generates velocity values at the hypocenter of our events. Our waveform analysis results reveal that our depths diverge from the Global Centroid Moment Tensor (GCMT) depths, which underestimate our deep lithosphere events and overestimate our shallow depths by as much as 17 km. We determined a depth of 45km for our deepest event. We will show a comparison of our final earthquake depths with the lithospheric thickness based on

  4. Comprehensive plate models for the thermal evolution of oceanic lithosphere

    NASA Astrophysics Data System (ADS)

    Grose, Christopher J.; Afonso, Juan Carlos

    2013-09-01

    Seafloor spreading and the cooling of oceanic lithosphere is a fundamental feature of plate tectonics in the Earth, the details of which are unveiled by modeling with constraints from mineral physics and geophysical observations. To work toward a more complete model of the thermal evolution of oceanic lithosphere, we investigate the contributions of axial hydrothermal circulation, oceanic crust, and temperature-pressure-dependent thermal properties. We find that models with only temperature-dependent properties disagree with geophysical observations unless properties are artificially modified. On the other hand, more comprehensive models are in better agreement with geophysical observations. Our preferred model requires a thermal expansivity reduction of 15% from a mineral physics estimate, and predicts a plate thickness of about 110-130 km. A principal result of our analysis is that the oceanic crust is a major contributor to the cooling of oceanic lithosphere. The oceanic crust acts as an insulating lid on the mantle, causing the rate of lithospheric cooling to increase from "crustal" values near the ridge to higher mantle values at old-age. Major consequences of this insulation effect are: (a) low seafloor subsidence rate in proximity to ridge axes (<5 Ma), (b) the thermal structure of oceanic lithosphere is significantly warmer than previous models, (c) seafloor heat flow is significantly lower over young (<35 Ma) seafloor compared to simple models, (d) a low net seafloor heat flux (˜27 TW), and (e) temperature at the base of the seismogenic zone extends to 700-800°C mantle.

  5. Using ocean tracers to reduce uncertainties about ocean diapycnal mixing and model projections

    NASA Astrophysics Data System (ADS)

    Goes, M. P.; Urban, N.; Keller, K.; Schmittner, A.; Tonkonojenkov, R.; Haran, M.

    2010-12-01

    Current projections of the oceanic response to anthropogenic climate forcings are uncertain. Two key sources of these uncertainties are (i) structural errors in current Earth system models and (ii) imperfect knowledge of model parameters. Ocean tracers observations have the potential to reduce these uncertainties. Previous studies typically consider each tracer separately, neglect potentially important statistical properties of the system, or use methods that impose rather daunting computational demands. Here we extend and improve upon a recently developed approach using horizontally averaged vertical profiles of chlorofluorocarbon (CFC-11), radiocarbon (DC14), and temperature (T) observations to reduce model parametric and structural uncertainties. Our method estimates a joint probability density function, which considers cross-tracer correlations and spatial autocorrelations of the errors. We illustrate this method by estimating two model parameters related to the vertical diffusivity, the background vertical diffusivity and the upper Southern Ocean mixing. We show that enhancing the upper Southern Ocean mixing in the model improves the representations of ocean tracers, as well as improves hindcasts of the Atlantic Meridional Overturning Circulation (AMOC) and Ocean Carbon uptake. The most probable value of the background vertical diffusivity in the pelagic pycnocline is between 0.1-0.2 cm2/s. According to the statistical method, observations of DC14 reduce the uncertainty about the background vertical diffusivity the most followed by CFC-11 and T. Using all three tracers jointly reduces the model uncertainty by 40%, more than each tracer individually. Given several important caveats, we illustrate how the reduced model parametric uncertainty improves probabilistic projections of the AMOC and Ocean Carbon uptake.

  6. Numerical model of the transition from continental rifting to oceanization: the case study of the Ligure-Piemontese ocean.

    NASA Astrophysics Data System (ADS)

    Roda, M.; Marotta, A. M.; Conte, K.; Spalla, M. I.

    2015-12-01

    The transition from continental rifting to oceanization has been investigated by mean of a 2D thermo-mechanical numerical model in which the formation of oceanic crust by mantle serpentinization, due to the hydration of the uprising peridotite, as been implemented. Model predictions have been compared with natural data related to the Permian-Triassic thinning affecting the continental lithosphere of the Alpine domain, in order to identify which portions of the present Alpine-Apennine system, preserving the imprints of Permian-Triassic high temperature (HT) metamorphism, is compatible, in terms of lithostratigraphy and tectono-metamorphic evolution, with a lithospheric extension preceding the opening of the Ligure-Piemontese oceanic basin. At this purpose age, petrological and structural data from the Alpine and Apennine ophiolite complexes are compared with model predictions from the oceanization stage. Our comparative analysis supports the thesis that the lithospheric extension preceding the opening of the Alpine Tethys did not start on a stable continental lithosphere, but developed by recycling part of the old Variscan collisional suture. The HT Permian-Triassic metamorphic re-equilibration overprints an inherited tectonic and metamorphic setting consequent to the Variscan subduction and collision, making the Alps a key case history to explore mechanisms responsible for the re-activation of orogenic scars.

  7. Analyzing Glacial-Interglacial Ocean Biogeochemical States in the MPI-Earth System Model

    NASA Astrophysics Data System (ADS)

    Heinze, M.; Ilyina, T.

    2015-12-01

    There is still little consensus about the mechanisms causing the glacial - interglacial variationsin atmospheric CO2 concentrations of around 100 ppm. Some of those mechanisms aredriven by alterations in ocean biogeochemical cycles. Hence, it is crucial to understand oceanbiogeochemistry dynamics during glacial-interglacial transitions. Within the German nationalclimate modeling initiative PalMod, aiming at simulating a full glacial cycle (135k - today) intransient mode with a state-of-the-art Earth System Model (ESM), we address the oceanbiogeochemistry cycles using a comprehensive modeling approach. In order to set up themodel we start with ocean only simulations, which are based on the 3-D ocean generalcirculation model MPIOM coupled to the ocean biogeochemistry model HAMOCC.Atmospheric forcing data is derived from a fully coupled LGM simulation including theatmosphere general circulation model ECHAM6. This setup provides us a sophisticatedrepresentation of the ocean biogeochemistry during the LGM without using any kind of datarestoring,to be consistent with the biological, chemical and physical dynamics of the model.We analyze alterations in ocean biogeochemistry during the LGM in comparison to a preindustrialcontrol climate. We discuss and quantify the changes in ocean biogeochemicalcycles between these two states, as well as possible implications for carbon transfer due tochanges in ocean dynamics. In the next steps we will use the ocean biogeochemistry model aspart of the fully coupled MPI-ESM. Our results aim at improving the understanding of glacial- interglacial changes in atmospheric CO2, especially in terms of marine carbon sequestrationand release. The presented work contributes to developing comprehensive ESMs, which arecapable of simulating the climate evolution and the variability during the last glacial cycle.

  8. A Community Terrain-Following Ocean Modeling System

    DTIC Science & Technology

    2006-09-30

    ways to incorporate wetting and drying effects. 4. A new NPZD biological model have been added using the formulation proposed by Powell et al. (2006...A Community Terrain-Following Ocean Modeling System Hernan G. Arango Institute of Marine and Coastal Sciences Rutgers University 71 Dudley Road...generation primitive equation, Terrain-following Ocean Modeling System (TOMS) for high-resolution scientific and operational applications. This

  9. Ocean modelling on the CYBER 205 at GFDL

    NASA Technical Reports Server (NTRS)

    Cox, M.

    1984-01-01

    At the Geophysical Fluid Dynamics Laboratory, research is carried out for the purpose of understanding various aspects of climate, such as its variability, predictability, stability and sensitivity. The atmosphere and oceans are modelled mathematically and their phenomenology studied by computer simulation methods. The present state-of-the-art in the computer simulation of large scale oceans on the CYBER 205 is discussed. While atmospheric modelling differs in some aspects, the basic approach used is similar. The equations of the ocean model are presented along with a short description of the numerical techniques used to find their solution. Computational considerations and a typical solution are presented in section 4.

  10. Early Eocene's climate and ocean circulation from coupled model simulations

    NASA Astrophysics Data System (ADS)

    Weber, Tobias; Thomas, Maik

    2014-05-01

    While proxy data provide a snapshot of climate conditions at a specific location, coupled atmosphere-ocean models are able to expand this knowledge over the globe. Therefore, they are indispensable tools for understanding past climate conditions. We model the dynamical state of atmosphere and ocean during the Early Eocene and pre-industrial times, using the coupled atmosphere-ocean model ECHAM5/MPIOM with realistic reconstructions of vegetation and CO2. The resulting simulated climate variables are compared to terrestrial and oceanic proxies. The Early Eocene climate is in the global mean warmer (~13°C) and wetter (~1 mm/d) than in pre-industrial times. Especially temperatures in the Southern Ocean, the Greenland Sea and Arctic Ocean raise by up to 25K, being in accordance with surface temperature estimates from terrestrial and marine proxy data. The oceans are hereby rendered ice-free, leading to a decrease of polar albedo and thereby facilitating polar warming. This leads to a by 5K diminished equator-to-pole temperature gradient. Warmer temperatures as well as changed bathymetry have an effect on ocean dynamics in the Early Eocene. Although deep-water formation can be found in the Greenland Sea, Weddell Sea, and Tethys Sea, it is weaker than in the pre-industrial run and the resulting circulation is shallower. This is not only visible in water transport through sea gates but also in the Atlantic Meridional Overturning Circulation (AMOC), adopting its maximum at 700m depths in the Early Eocene, while maximum transport is reached in the pre-industrial control run at 1200m. Albeit a shallow and weak thermohaline circulation, a global ocean conveyor belt is being triggered, causing a transport from the areas of subduction through the Atlantic and Southern Oceans into the Indian and Pacific Oceans.

  11. Modeling pCO sub 2 in the upper ocean

    SciTech Connect

    Archer, D.

    1990-12-01

    This report summarizes our current understanding of the physical, chemical, and biological processes that control the natural cycling of carbon dioxide (CO{sub 2}) in the surface ocean. Because the physics of mixing at the ocean surface creates the essential framework for the chemistry and biology, and because the literature on surface ocean mixing is extensive, a major focus of the report is to review existing mixed layer models for the upper ocean and their implementation in global ocean circulation models. Three families of mixed layer models have been developed. The integrated turbulent kinetic energy'' (TKE) models construct a budget for surface ocean TKE, using the wind stress as source and dissipation as sink for TKE. The shear instability'' models maintain profiles of current velocity resulting from the wind stress. Turbulence closure'' models are the most general and the most complicated of the three types, and are based on laboratory studies of fluid turbulence. This paper explores behavioral distinctions between the three types of models, and summarizes previously published comparisons of the generality, accuracy, and computational requirements of the three models. The application of mixed layer models to treatment of sea ice is also reviewed. 101 refs., 7 figs., 1 tab.

  12. Modelling the distribution of plutonium in the Pacific Ocean.

    PubMed

    Nakano, Masanao; Povinec, Pavel P

    2003-01-01

    An Oceanic General Circulation Model (OGCM) including a plutonium scavenging model as well as an advection-diffusion model has been developed for modelling the distribution of plutonium in the Pacific Ocean. Calculated 239, 240Pu water profile concentrations and 239, 240Pu inventories in water and sediment of the Pacific Ocean have showed a reasonable agreement with the experimental results. The presence of local fallout plutonium in central North Pacific waters has been confirmed. The observed 240Pu/239Pu mass ratios confirm that plutonium originating from local fallout from nuclear weapons tests carried out at Bikini and Enewetak Atolls is more rapidly removed from surface waters to deeper waters than plutonium originating from global fallout. The developed OGCM can be used for modelling the dispersion of other non-conservative tracers in the ocean as well.

  13. Observed and Modeled Trends in Southern Ocean Sea Ice

    NASA Technical Reports Server (NTRS)

    Parkinson, Claire L.

    2003-01-01

    Conceptual models and global climate model (GCM) simulations have both indicated the likelihood of an enhanced sensitivity to climate change in the polar regions, derived from the positive feedbacks brought about by the polar abundance of snow and ice surfaces. Some models further indicate that the changes in the polar regions can have a significant impact globally. For instance, 37% of the temperature sensitivity to a doubling of atmospheric CO2 in simulations with the GCM of the Goddard Institute for Space Studies (GISS) is attributable exclusively to inclusion of sea ice variations in the model calculations. Both sea ice thickness and sea ice extent decrease markedly in the doubled CO, case, thereby allowing the ice feedbacks to occur. Stand-alone sea ice models have shown Southern Ocean hemispherically averaged winter ice-edge retreats of 1.4 deg latitude for each 1 K increase in atmospheric temperatures. Observations, however, show a much more varied Southern Ocean ice cover, both spatially and temporally, than many of the modeled expectations. In fact, the satellite passive-microwave record of Southern Ocean sea ice since late 1978 has revealed overall increases rather than decreases in ice extents, with ice extent trends on the order of 11,000 sq km/year. When broken down spatially, the positive trends are strongest in the Ross Sea, while the trends are negative in the Bellingshausen/Amundsen Seas. Greater spatial detail can be obtained by examining trends in the length of the sea ice season, and those trends show a coherent picture of shortening sea ice seasons throughout almost the entire Bellingshausen and Amundsen Seas to the west of the Antarctic Peninsula and in the far western Weddell Sea immediately to the east of the Peninsula, with lengthening sea ice seasons around much of the rest of the continent. This pattern corresponds well with the spatial pattern of temperature trends, as the Peninsula region is the one region in the Antarctic with a strong

  14. Variability of Ocean Heat Uptake: Reconciling Observations and Models

    SciTech Connect

    AchutaRao, K M; Santer, B D; Gleckler, P J; Taylor, K; Pierce, D; Barnett, T; Wigley, T L

    2005-05-05

    This study examines the temporal variability of ocean heat uptake in observations and in climate models. Previous work suggests that coupled Atmosphere-Ocean General Circulation Models (A-OGCMs) may have underestimated the observed natural variability of ocean heat content, particularly on decadal and longer timescales. To address this issue, we rely on observed estimates of heat content from the 2004 World Ocean Atlas (WOA-2004) compiled by Levitus et al. (2005). Given information about the distribution of observations in WOA-2004, we evaluate the effects of sparse observational coverage and the infilling that Levitus et al. use to produce the spatially-complete temperature fields required to compute heat content variations. We first show that in ocean basins with limited observational coverage, there are important differences between ocean temperature variability estimated from observed and infilled portions of the basin. We then employ data from control simulations performed with eight different A-OGCMs as a test-bed for studying the effects of sparse, space- and time-varying observational coverage. Subsampling model data with actual observational coverage has a large impact on the inferred temperature variability in the top 300 and 3000 meters of the ocean. This arises from changes in both sampling depth and in the geographical areas sampled. Our results illustrate that subsampling model data at the locations of available observations increases the variability, reducing the discrepancy between models and observations.

  15. Southern Ocean abyssal heat uptake in fine and coarse resolution climate model simulations

    NASA Astrophysics Data System (ADS)

    Newsom, E. R.; Singh, H.; Bitz, C. M.

    2013-12-01

    The recently observed warming of Antarctic Bottom Water (AABW) represents an important component of accumulated sea level rise and global ocean heat uptake. Yet in simulations of greenhouse warming with coarse resolution climate models (which parameterize ocean eddies), Southern Ocean heat uptake dominantly occurs within near-surface waters, which are subsequently transported northward and subducted at mid-latitudes. Here, we examine the response of the abyssal Southern Ocean to greenhouse forcing within a global climate model run with a fine resolution (eddy-resolving) ocean component, which more faithfully simulates AABW formation than its coarse resolution counterparts. We argue that AABW warming may play a more important role in Southern Ocean heat uptake than is suggested by the CMIP5 ensemble of coarse resolution models. We examine the heat uptake in the Southern Ocean using the Community Climate System Model version 3.5 (CCSM 3.5). The model was run at two resolutions in the ocean and sea ice components: coarse (1 degree), which is a standard resolution of many CMIP5 models, and fine (.1 degree), in which sea ice and AABW is formed more realistically. The atmosphere and land components were fixed throughout at .5 degrees resolution. Each version was forced identically with a 1% ramping of CO2 for 150 years. The fine resolution simulation produces more dense water in the control climate, which sinks to a more realistic depth. We attribute this to the improved simulation of sea ice formation regions granted by increasing the ocean model resolution. The reduction of AABW formation as the climate warms leads to a larger response at depth at fine resolution; below 2000 meters, the fine resolution simulation takes up two orders of magnitude more heat than at coarse resolution. We further propose a framework to weigh the amount of heat taken up at depth in the Southern Ocean by the timescale at which it is sequestered, giving more value to heating of regions with

  16. Modeling water clarity in oceans and coasts

    EPA Science Inventory

    In oceans and coastal waters, phytoplankton is the primary producer of organic compounds which form the base for the food chain. The concentration of phytoplankton is a major factor controlling water clarity and the depth to which light penetrates in the water column. The light i...

  17. Advances in a distributed approach for ocean model data interoperability

    USGS Publications Warehouse

    Signell, Richard P.; Snowden, Derrick P.

    2014-01-01

    An infrastructure for earth science data is emerging across the globe based on common data models and web services. As we evolve from custom file formats and web sites to standards-based web services and tools, data is becoming easier to distribute, find and retrieve, leaving more time for science. We describe recent advances that make it easier for ocean model providers to share their data, and for users to search, access, analyze and visualize ocean data using MATLAB® and Python®. These include a technique for modelers to create aggregated, Climate and Forecast (CF) metadata convention datasets from collections of non-standard Network Common Data Form (NetCDF) output files, the capability to remotely access data from CF-1.6-compliant NetCDF files using the Open Geospatial Consortium (OGC) Sensor Observation Service (SOS), a metadata standard for unstructured grid model output (UGRID), and tools that utilize both CF and UGRID standards to allow interoperable data search, browse and access. We use examples from the U.S. Integrated Ocean Observing System (IOOS®) Coastal and Ocean Modeling Testbed, a project in which modelers using both structured and unstructured grid model output needed to share their results, to compare their results with other models, and to compare models with observed data. The same techniques used here for ocean modeling output can be applied to atmospheric and climate model output, remote sensing data, digital terrain and bathymetric data.

  18. Oxygen utilization rate (OUR) underestimates ocean respiration: A model study

    NASA Astrophysics Data System (ADS)

    Koeve, W.; Kähler, P.

    2016-08-01

    We use a simple 1-D model representing an isolated density surface in the ocean and 3-D global ocean biogeochemical models to evaluate the concept of computing the subsurface oceanic oxygen utilization rate (OUR) from the changes of apparent oxygen utilization (AOU) and water age. The distribution of AOU in the ocean is not only the imprint of respiration in the ocean's interior but is strongly influenced by transport processes and eventually loss at the ocean surface. Since AOU and water age are subject to advection and diffusive mixing, it is only when they are affected both in the same way that OUR represents the correct rate of oxygen consumption. This is the case only when advection prevails or with uniform respiration rates, when the proportions of AOU and age are not changed by transport. In experiments with the 1-D tube model, OUR underestimates respiration when maximum respiration rates occur near the outcrops of isopycnals and overestimates when maxima occur far from the outcrops. Given the distribution of respiration in the ocean, i.e., elevated rates near high-latitude outcrops of isopycnals and low rates below the oligotrophic gyres, underestimates are the rule. Integrating these effects globally in three coupled ocean biogeochemical and circulation models, we find that AOU-over-age based calculations underestimate true model respiration by a factor of 3. Most of this difference is observed in the upper 1000 m of the ocean with the discrepancies increasing toward the surface where OUR underestimates respiration by as much as factor of 4.

  19. Theory and Practice of Data Assimilation in Ocean Modeling

    DTIC Science & Technology

    2001-09-30

    implementation and validation of practical data assimilation methods for synoptic ocean models. By “data assimilation” we mean the construction of a...composite estimate of the state of the ocean based on a combination of observed data with computational model output. Since data assimilation methods which...interested in the price paid in terms of accuracy and confidence for using economical but suboptimal data assimilation methods . Direct calculation of

  20. Theory and Practice of Data Assimilation in Ocean Modeling

    DTIC Science & Technology

    2006-09-30

    assimilation methods for regional to basin scale ocean models. By "data assimilation" we mean the construction of a composite estimate of the state...of the ocean based on a combination of observed data with computational model output. Since data assimilation methods which give the most and best...terms of accuracy and confidence for using economical but suboptimal data assimilation methods . Report Documentation Page Form ApprovedOMB No

  1. Theory and Practice of Data Assimilation in Ocean Modeling

    DTIC Science & Technology

    1998-01-01

    practical data assimilation methods for synoptic ocean models. By "data assimilation" we mean the construction of a composite estimate of the state of the...ocean based on a combination of observed data with computational model output. Since data assimilation methods which give the most and best information...accuracy and confidence for using economical but suboptimal data assimilation methods . Optimized methods require accurate knowledge of the statistics of

  2. Theory and Practice of Data Assimilation in Ocean Modeling

    DTIC Science & Technology

    1997-09-30

    assimilation methods for synoptic ocean models. By “data assimilation,” we mean the construction of a composite estimate of the state of the ocean based on a...combination of observed data with computational model output. Since data assimilation methods which give the most and best information are highly...accuracy and confidence for using economical but suboptimal data assimilation methods . Optimized methods require accurate knowledge of the statistics of

  3. Modeling and Parameterization Study of Radiance in a Dynamic Ocean

    DTIC Science & Technology

    2012-09-30

    simulation of nonlinear capillary-gravity waves (CGW) • develop numerical capabilities for free-surface turbulence ( FST ) and the resultant surface...based simulations and modeling to solve the problem of ocean RT in a dynamic SBL environment that includes CGW and FST . The complex dynamic...processes of the ocean SBL, the nonlinear CGW interactions, and the development and transport of FST are modeled using physics-based computations. The

  4. An Arctic Ice/Ocean Coupled Model with Wave Interactions

    DTIC Science & Technology

    2013-09-30

    case TOPAZ : a hybrid coordinate ocean model of roughly 13 km horizontal resolution forced by ECMWF atmospheric fields, as the platform to construct a...the TOPAZ ice/ocean model and WAVEWATCH III, and, for the latter, cross-relate to any viscoelastic parametrization of the sea ice to calibrate the...goal of embedding the 3D WIM described above into the TOPAZ framework, by so doing allowing fully directional seas generated by WAVEWATCH III as

  5. Hybrid reduced order modeling for assembly calculations

    DOE PAGES

    Bang, Youngsuk; Abdel-Khalik, Hany S.; Jessee, Matthew A.; ...

    2015-08-14

    While the accuracy of assembly calculations has greatly improved due to the increase in computer power enabling more refined description of the phase space and use of more sophisticated numerical algorithms, the computational cost continues to increase which limits the full utilization of their effectiveness for routine engineering analysis. Reduced order modeling is a mathematical vehicle that scales down the dimensionality of large-scale numerical problems to enable their repeated executions on small computing environment, often available to end users. This is done by capturing the most dominant underlying relationships between the model's inputs and outputs. Previous works demonstrated the usemore » of the reduced order modeling for a single physics code, such as a radiation transport calculation. This paper extends those works to coupled code systems as currently employed in assembly calculations. Finally, numerical tests are conducted using realistic SCALE assembly models with resonance self-shielding, neutron transport, and nuclides transmutation/depletion models representing the components of the coupled code system.« less

  6. Hybrid reduced order modeling for assembly calculations

    SciTech Connect

    Bang, Youngsuk; Abdel-Khalik, Hany S.; Jessee, Matthew A.; Mertyurek, Ugur

    2015-08-14

    While the accuracy of assembly calculations has greatly improved due to the increase in computer power enabling more refined description of the phase space and use of more sophisticated numerical algorithms, the computational cost continues to increase which limits the full utilization of their effectiveness for routine engineering analysis. Reduced order modeling is a mathematical vehicle that scales down the dimensionality of large-scale numerical problems to enable their repeated executions on small computing environment, often available to end users. This is done by capturing the most dominant underlying relationships between the model's inputs and outputs. Previous works demonstrated the use of the reduced order modeling for a single physics code, such as a radiation transport calculation. This paper extends those works to coupled code systems as currently employed in assembly calculations. Finally, numerical tests are conducted using realistic SCALE assembly models with resonance self-shielding, neutron transport, and nuclides transmutation/depletion models representing the components of the coupled code system.

  7. Chaotic dynamics in a simple dynamical green ocean plankton model

    NASA Astrophysics Data System (ADS)

    Cropp, Roger; Moroz, Irene M.; Norbury, John

    2014-11-01

    The exchange of important greenhouse gases between the ocean and atmosphere is influenced by the dynamics of near-surface plankton ecosystems. Marine plankton ecosystems are modified by climate change creating a feedback mechanism that could have significant implications for predicting future climates. The collapse or extinction of a plankton population may push the climate system across a tipping point. Dynamic green ocean models (DGOMs) are currently being developed for inclusion into climate models to predict the future state of the climate. The appropriate complexity of the DGOMs used to represent plankton processes is an ongoing issue, with models tending to become more complex, with more complicated dynamics, and an increasing propensity for chaos. We consider a relatively simple (four-population) DGOM of phytoplankton, zooplankton, bacteria and zooflagellates where the interacting plankton populations are connected by a single limiting nutrient. Chaotic solutions are possible in this 4-dimensional model for plankton population dynamics, as well as in a reduced 3-dimensional model, as we vary two of the key mortality parameters. Our results show that chaos is robust to the variation of parameters as well as to the presence of environmental noise, where the attractor of the more complex system is more robust than the attractor of its simplified equivalent. We find robust chaotic dynamics in low trophic order ecological models, suggesting that chaotic dynamics might be ubiquitous in the more complex models, but this is rarely observed in DGOM simulations. The physical equations of DGOMs are well understood and are constrained by conservation principles, but the ecological equations are not well understood, and generally have no explicitly conserved quantities. This work, in the context of the paucity of the empirical and theoretical bases upon which DGOMs are constructed, raises the interesting question of whether DGOMs better represent reality if they include

  8. Arctic Ocean Freshwater: How Robust are Model Simulations

    NASA Technical Reports Server (NTRS)

    Jahn, A.; Aksenov, Y.; deCuevas, B. A.; deSteur, L.; Haekkinen, S.; Hansen, E.; Herbaut, C.; Houssais, M.-N.; Karcher, M.; Kauker, F.; Lique, C.; Nguyen, A.; Pemberton, P.; Worthen, D.; Zhang, J.

    2012-01-01

    The Arctic freshwater (FW) has been the focus of many modeling studies, due to the potential impact of Arctic FW on the deep water formation in the North Atlantic. A comparison of the hindcasts from ten ocean-sea ice models shows that the simulation of the Arctic FW budget is quite different in the investigated models. While they agree on the general sink and source terms of the Arctic FW budget, the long-term means as well as the variability of the FW export vary among models. The best model-to-model agreement is found for the interannual and seasonal variability of the solid FW export and the solid FW storage, which also agree well with observations. For the interannual and seasonal variability of the liquid FW export, the agreement among models is better for the Canadian Arctic Archipelago (CAA) than for Fram Strait. The reason for this is that models are more consistent in simulating volume flux anomalies than salinity anomalies and volume-flux anomalies dominate the liquid FW export variability in the CAA but not in Fram Strait. The seasonal cycle of the liquid FW export generally shows a better agreement among models than the interannual variability, and compared to observations the models capture the seasonality of the liquid FW export rather well. In order to improve future simulations of the Arctic FW budget, the simulation of the salinity field needs to be improved, so that model results on the variability of the liquid FW export and storage become more robust.

  9. Tracer Modeling with the Hybrid Coordinates Ocean Model (hycom)

    NASA Astrophysics Data System (ADS)

    Garraffo, Z. D.; Kim, H.; Li, B.; Mehra, A.; Rivin, I.; Spindler, T.; Tolman, H. L.

    2012-12-01

    A series of tracer simulations have been started at NCEP/NWS aiming to a variety of applications, from dispersion of contaminants in estimations motivated by the Japanese nuclear accident near Fukushima, to nutrient estimations. The tracer capabilities of HYCOM are used, in regional domains, nested to daily nowcast/forecast fields from 1/12 HYCOM (RTOFS-Global) model output. A Fukushima Cs-137 simulation is now run in operational mode (RTOFS_ET). The simulation was initialized at the time of the Fukushima nuclear accident, and includes atmospheric deposition of Cs-137 and coastal discharge from a high resolution coastal model (ROMS done at NOAA/NOS). Almost all tracer moved offshore before the end of the first year after the accident. The tracer initially deposited in the Pacific ocean through the atmosphere slowly moves eastward and to deeper waters following the 3D ocean circulation. A series of simulations were started for nutrient estimations in the Gulf Stream and Mid Atlantic Bight region. Initially the capabilities implemented in HYCOM are used. The work aims to monitoring nutrients in the chosen region. Work is done in collaboration with Victoria Coles of U. Maryland.

  10. Multi-property modeling of ocean basin carbon fluxes

    NASA Technical Reports Server (NTRS)

    Volk, Tyler

    1988-01-01

    The objectives of this project were to elucidate the causal mechanisms in some of the most important features of the global ocean/atomsphere carbon system. These included the interaction of physical and biological processes in the seasonal cycle of surface water pCo2, and links between productivity, surface chlorophyll, and the carbon cycle that would aid global modeling efforts. In addition, several other areas of critical scientific interest involving links between the marine biosphere and the global carbon cycle were successfully pursued; specifically, a possible relation between phytoplankton emitted DMS and climate, and a relation between the location of calcium carbonate burial in the ocean and metamorphic source fluxes of CO2 to the atmosphere. Six published papers covering the following topics are summarized: (1) Mass extinctions, atmospheric sulphur and climatic warming at the K/T boundary; (2) Sensitivity of climate and atmospheric CO2 to deep-ocean and shallow-ocean carbonate burial; (3) Controls on CO2 sources and sinks in the earthscale surface ocean; (4) pre-anthropogenic, earthscale patterns of delta pCO2 between ocean and atmosphere; (5) Effect on atmospheric CO2 from seasonal variations in the high latitude ocean; and (6) Limitations or relating ocean surface chlorophyll to productivity.

  11. Numerical simulation of Typhoon Muifa (2011) using a Coupled Ocean-Atmosphere-Wave-Sediment Transport (COAWST) modeling system

    NASA Astrophysics Data System (ADS)

    Liu, Na; Ling, Tiejun; Wang, Hui; Zhang, Yunfei; Gao, Zhiyi; Wang, Yi

    2015-04-01

    The newly developed Coupled Ocean-Atmosphere-Wave-Sediment Transport (COAWST) Modeling System is applied to investigate typhoon-ocean interactions in this study. The COAWST modeling system represents the state-of-the-art numerical simulation technique comprising several coupled models to study coastal and environmental processes. The modeling system is applied to simulate Typhoon Muifa (2011), which strengthened from a tropical storm to a super typhoon in the Northwestern Pacific, to explore the heat fluxes exchanged among the processes simulated using the atmosphere model WRF, ocean model ROMS and wave model SWAN. These three models adopted the same horizontal grid. Three numerical experiments with different coupling configurations are performed in order to investigate the impact of typhoon-ocean interaction on the intensity and ocean response to typhoon. The simulated typhoon tracks and intensities agree with observations. Comparisons of the simulated variables with available atmospheric and oceanic observations show the good performance of using the coupled modeling system for simulating the ocean and atmosphere processes during a typhoon event. The fully coupled simulation that includes a ocean model identifies a decreased SST as a result of the typhoon-forced entrainment. Typhoon intensity and wind speed are reduced due to the decrease of the sea surface temperature when using a coupled ocean model. The experiments with ocean coupled to atmosphere also results in decreased sea surface heat flux and air temperature. The heat flux decreases by about 29% compared to the WRF only case. The reduction of the energy induced by SST decreases, resulting in weakening of the typhoon. Coupling of the waves to the atmosphere and ocean model induces a slight increase of SST in the typhoon center area with the ocean-atmosphere interaction increased as a result of wave feedback to atmosphere.

  12. Testing Components of New Community Isopycnal Ocean Circulation Model

    SciTech Connect

    Bryan, Kirk

    2008-05-09

    The ocean and atmosphere are both governed by the same physical laws and models of the two media have many similarities. However, there are critical differences that call for special methods to provide the best simulation. One of the most important difference is that the ocean is nearly opaque to radiation in the visible and infra-red part of the spectrum. For this reason water mass properties in the ocean are conserved along trajectories for long distances and for long periods of time. For this reason isopycnal coordinate models would seem to have a distinct advantage in simulating ocean circulation. In such a model the coordinate surfaces are aligned with the natural paths of near adiabatic, density conserving flow in the main thermocline. The difficulty with this approach is at the upper and lower boundaries of the ocean, which in general do not coincide with density surfaces. For this reason hybrid coordinate models were proposed by Bleck and Boudra (1981) in which Cartesian coordinates were used near the ocean surface and isopycnal coordinates were used in the main thermocline. This feature is now part of the HICOM model (Bleck, 2002).

  13. Development of a regional model for the North Indian Ocean

    NASA Astrophysics Data System (ADS)

    Rahaman, Hasibur; Ravichandran, M.; Sengupta, Debasis; Harrison, Matthew J.; Griffies, Stephen M.

    2014-03-01

    We have developed a one-way nested Indian Ocean regional model. The model combines the National Oceanic and Atmospheric Administration (NOAA) Geophysical Fluid Dynamics Laboratory's (GFDL) Modular Ocean Model (MOM4p1) at global climate model resolution (nominally one degree), and a regional Indian Ocean MOM4p1 configuration with 25 km horizontal resolution and 1 m vertical resolution near the surface. Inter-annual global simulations with Coordinated Ocean-Ice Reference Experiments (CORE-II) surface forcing over years 1992-2005 provide surface boundary conditions. We show that relative to the global simulation, (i) biases in upper ocean temperature, salinity and mixed layer depth are reduced, (ii) sea surface height and upper ocean circulation are closer to observations, and (iii) improvements in model simulation can be attributed to refined resolution, more realistic topography and inclusion of seasonal river runoff. Notably, the surface salinity bias is reduced to less than 0.1 psu over the Bay of Bengal using relatively weak restoring to observations, and the model simulates the strong, shallow halocline often observed in the North Bay of Bengal. There is marked improvement in subsurface salinity and temperature, as well as mixed layer depth in the Bay of Bengal. Major seasonal signatures in observed sea surface height anomaly in the tropical Indian Ocean, including the coastal waveguide around the Indian peninsula, are simulated with great fidelity. The use of realistic topography and seasonal river runoff brings the three dimensional structure of the East India Coastal Current and West India Coastal Current much closer to observations. As a result, the incursion of low salinity Bay of Bengal water into the south-eastern Arabian Sea is more realistic.

  14. Improved Upper Ocean/Sea Ice Modeling in the GISS GCM for Investigating Climate Change

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This project built on our previous results in which we highlighted the importance of sea ice in overall climate sensitivity by determining that for both warming and cooling climates, when sea ice was not allowed to change, climate sensitivity was reduced by 35-40%. We also modified the Goddard Institute for Space Studies (GISS) 8 deg x lO deg atmospheric General Circulation Model (GCM) to include an upper-ocean/sea-ice model involving the Semtner three-layer ice/snow thermodynamic model, the Price et al. (1986) ocean mixed layer model and a general upper ocean vertical advection/diffusion scheme for maintaining and fluxing properties across the pycnocline. This effort, in addition to improving the sea ice representation in the AGCM, revealed a number of sensitive components of the sea ice/ocean system. For example, the ability to flux heat through the ice/snow properly is critical in order to resolve the surface temperature properly, since small errors in this lead to unrestrained climate drift. The present project, summarized in this report, had as its objectives: (1) introducing a series of sea ice and ocean improvements aimed at overcoming remaining weaknesses in the GCM sea ice/ocean representation, and (2) performing a series of sensitivity experiments designed to evaluate the climate sensitivity of the revised model to both Antarctic and Arctic sea ice, determine the sensitivity of the climate response to initial ice distribution, and investigate the transient response to doubling CO2.

  15. Ocean and Coastal Modeling: Nonlinear Acoustic Propagation

    DTIC Science & Technology

    2009-03-27

    support of the operations at sea . The NRL prediction system, was configured with 3 nesting domains at resolutions of 4, 2, and 0.6 km. Two separate...to provide a minimum connection with realtime data since NCOM-GL assimilates sea surface temperatures (SST) and Modular Ocean Data Assimilation...recirculation patterns can be found between the eddy and the coastline. [FIGURE 2] The Sea Surface Temperature (SST) images obtained from NOAA AVHRR displayed

  16. Optimal Combining Data for Improving Ocean Modeling

    DTIC Science & Technology

    2008-09-30

    hyperbolic or elliptic) and on the Hurst exponent characterizing the dynamics type (local or non-local). 3. Fusion data for estimating RD. Theoretical...1) RD vs time and different values of Hurst exponent h = 0.1 (black), h = 1 (red), h = 2 (blue) γ = 0.1,Ω = 0, 2) Same for γ = 0.1,Ω = 2 ). 3...accurate estimating the upper ocean velocity field and mixing characteristics such as relative dispersion and finite size Lyapunov exponent , (2

  17. Models of the Equatorial Ocean Circulation.

    DTIC Science & Technology

    1980-01-01

    doctoral committee for their encouragement and advice in the development of this work. I am especially indebted to Dr. Julian P. McCreary of Nova University...large scale wind fluctuations thousands of kilometers to the west in the Central Pacific ( McCreary , 1977). A better understanding of such events could...all equatorial oceans can be found in Knauss (1963); Philander (1973b); Leetmaa, McCreary and Moore (1980); Tsuchiya (1975); Cochrane et al. (1979) and

  18. Reduced Order Modeling in General Relativity

    NASA Astrophysics Data System (ADS)

    Tiglio, Manuel

    2014-03-01

    Reduced Order Modeling is an emerging yet fast developing filed in gravitational wave physics. The main goals are to enable fast modeling and parameter estimation of any detected signal, along with rapid matched filtering detecting. I will focus on the first two. Some accomplishments include being able to replace, with essentially no lost of physical accuracy, the original models with surrogate ones (which are not effective ones, that is, they do not simplify the physics but go on a very different track, exploiting the particulars of the waveform family under consideration and state of the art dimensional reduction techniques) which are very fast to evaluate. For example, for EOB models they are at least around 3 orders of magnitude faster than solving the original equations, with physically equivalent results. For numerical simulations the speedup is at least 11 orders of magnitude. For parameter estimation our current numbers are about bringing ~100 days for a single SPA inspiral binary neutron star Bayesian parameter estimation analysis to under a day. More recently, it has been shown that the full precessing problem for, say, 200 cycles, can be represented, through some new ideas, by a remarkably compact set of carefully chosen reduced basis waveforms (~10-100, depending on the accuracy requirements). I will highlight what I personally believe are the challenges to face next in this subarea of GW physics and where efforts should be directed. This talk will summarize work in collaboration with: Harbir Antil (GMU), Jonathan Blackman (Caltech), Priscila Canizares (IoA, Cambridge, UK), Sarah Caudill (UWM), Jonathan Gair (IoA. Cambridge. UK), Scott Field (UMD), Chad R. Galley (Caltech), Frank Herrmann (Germany), Han Hestahven (EPFL, Switzerland), Jason Kaye (Brown, Stanford & Courant). Evan Ochsner (UWM), Ricardo Nochetto (UMD), Vivien Raymond (LIGO, Caltech), Rory Smith (LIGO, Caltech) Bela Ssilagyi (Caltech) and MT (UMD & Caltech).

  19. Numerical modeling of ocean hydrodynamics with variational assimilation of observational data

    NASA Astrophysics Data System (ADS)

    Zalesny, V. B.; Agoshkov, V. I.; Shutyaev, V. P.; Le Dimet, F.; Ivchenko, B. O.

    2016-07-01

    Models and methods of the numerical modeling of ocean hydrodynamics dating back to the pioneering works of A.S. Sarkisyan are considered, with emphasis on the formulation of problems and algorithms of mathematical modeling and the four-dimensional variational assimilation of observational data. An algorithm is proposed for studying the sensitivity of the optimal solution to observational data errors in a seasurface temperature assimilation problem in order to retrieve heat fluxes on the surface. An example of a solution of the optimal problem of the World Ocean hydrodynamics with the assimilation of climatic temperature and salinity observations is offered.

  20. Modeling Mesoscale Eddies in the North Atlantic Ocean

    NASA Technical Reports Server (NTRS)

    Chao, Yi

    1999-01-01

    Ocean modeling plays an important role in understanding the current climatic conditions and predicting the future climate change. Modeling the ocean at eddy-permitting and/or eddy resolving resolutions (1/3 degree or higher) has a two-fold objective. One part is to represent the ocean as realistically as possible, because mesoscale eddies have an impact on the large-scale circulation. The second objective is to learn how to represent effects of mesoscale eddies without explicitly resolving them. This is particularly important for climate models which cannot be run at eddy-resolving resolutions because of the computational constraints. At JPL, a 1/6 degree latitude by 1/6 degree longitude with 37 vertical levels Atlantic Ocean model has been developed. The model is based on the Parallel Ocean Program (POP) developed at Los Alamos National Laboratory (LANL). Using the 256-processor Cray T3D, we have conducted a 40-year integration of this Atlantic eddy-resolving ocean model. A regional analysis demonstrate that many observed features associated with the Caribbean Sea eddies can be realistically simulated by this model. Analysis of this Atlantic eddy-resolving ocean model further suggests that these Caribbean Sea eddies are connected with eddies formed outside the Caribbean Sea at the confluence of the North Brazil Current (NBC) and the North Equatorial Countercurrent. The diagram of the model simulated surface current shows that the Caribbean eddies ultimately originate in the NBC retroflection region, traveling more than a year from the North Brazil coast through the Lesser Antilles into the Caribbean Sea and eventually into the Gulf of Mexico. Additional information is contained in the original.

  1. A generalized multivariate regression model for modelling ocean wave heights

    NASA Astrophysics Data System (ADS)

    Wang, X. L.; Feng, Y.; Swail, V. R.

    2012-04-01

    In this study, a generalized multivariate linear regression model is developed to represent the relationship between 6-hourly ocean significant wave heights (Hs) and the corresponding 6-hourly mean sea level pressure (MSLP) fields. The model is calibrated using the ERA-Interim reanalysis of Hs and MSLP fields for 1981-2000, and is validated using the ERA-Interim reanalysis for 2001-2010 and ERA40 reanalysis of Hs and MSLP for 1958-2001. The performance of the fitted model is evaluated in terms of Pierce skill score, frequency bias index, and correlation skill score. Being not normally distributed, wave heights are subjected to a data adaptive Box-Cox transformation before being used in the model fitting. Also, since 6-hourly data are being modelled, lag-1 autocorrelation must be and is accounted for. The models with and without Box-Cox transformation, and with and without accounting for autocorrelation, are inter-compared in terms of their prediction skills. The fitted MSLP-Hs relationship is then used to reconstruct historical wave height climate from the 6-hourly MSLP fields taken from the Twentieth Century Reanalysis (20CR, Compo et al. 2011), and to project possible future wave height climates using CMIP5 model simulations of MSLP fields. The reconstructed and projected wave heights, both seasonal means and maxima, are subject to a trend analysis that allows for non-linear (polynomial) trends.

  2. Multiscale models for synoptic-mesoscale interactions in the ocean

    NASA Astrophysics Data System (ADS)

    Grooms, Ian; Shafer Smith, K.; Majda, Andrew J.

    2012-11-01

    Multiscale analysis is used to derive two sets of coupled models, each based on the same distinguished limit, to represent the interaction of the midlatitude oceanic synoptic scale-where coherent features such as jets and rings form-and the mesoscale, defined by the internal deformation scale. The synoptic scale and mesoscale overlap at low and mid latitudes, and are hence synonymous in much of the oceanographic literature; at higher latitudes the synoptic scale can be an order of magnitude larger than the deformation scale, which motivates our asymptotic approach and our nonstandard terminology. In the first model the synoptic dynamics are described by ‘Large Amplitude Geostrophic’ (LAG) equations while the eddy dynamics are quasigeostrophic. This model has order one isopycnal variation on the synoptic scale; the synoptic dynamics respond to an eddy momentum flux while the eddy dynamics respond to the baroclinically unstable synoptic density gradient. The second model assumes small isopycnal variation on the synoptic scale, but allows for a planetary scale background density gradient that may be fixed or evolved on a slower time scale. Here the large-scale equations are just the barotropic quasigeostrophic equations, and the mesoscale is modeled by the baroclinic quasigeostrophic equations. The synoptic dynamics now respond to both eddy momentum and buoyancy fluxes, but the small-scale eddy dynamics are simply advected by the synoptic-scale flow-there is no baroclinic production term in the eddy equations. The energy budget is closed by deriving an equation for the slow evolution of the eddy energy, which ensures that energy gained or lost by the synoptic-scale flow is reflected in a corresponding loss or gain by the eddies. This latter model, aided by the eddy energy equation-a key result of this paper-provides a conceptual basis through which to understand the classic baroclinic turbulence cycle.

  3. Detecting toxic diatom blooms from ocean color and a regional ocean model

    NASA Astrophysics Data System (ADS)

    Anderson, Clarissa R.; Kudela, Raphael M.; Benitez-Nelson, Claudia; Sekula-Wood, Emily; Burrell, Christopher T.; Chao, Yi; Langlois, Gregg; Goodman, Jo; Siegel, David A.

    2011-02-01

    An apparent link between upwelling-related physical signatures, macronutrients, and toxic diatom blooms in the various “hotspots” throughout California has motivated attempts to forecast harmful algal blooms (HABs) as a function of select environmental variables. Empirical models for predicting toxic Pseudo-nitzschia blooms in one such region, the Santa Barbara Channel (SBC), are tested in a nowcast mode using predictions based on merging data from MODIS ocean color geophysical products and the Regional Ocean Modeling System (ROMS) applied to the Southern California Bight. Thresholds for each model generate event forecasts. Spatially-explicit, monthly HAB maps are compared to shipboard observations and California monitoring data, demonstrating that the models predict offshore events otherwise undetected by nearshore monitoring. The use of mechanistic hydrodynamic models in concert with empirical, biological models facilitates future process studies on the effects of coastal eutrophication and climate change on regional HAB dynamics.

  4. Evaluating CMIP5 Models' Representation of Oceanic Drivers of North African Climate

    NASA Astrophysics Data System (ADS)

    Notaro, M.; Wang, F.; Yu, Y.; Mao, J.; Shi, X.; Wei, Y.

    2015-12-01

    North Africa is highly vulnerable to hydrologic variability and extremes, including impacts of climate change. Prior North African studies largely disagree regarding the dominant oceanic drivers of the region's hydrologic variability and the likely impacts of climate change. Here, we aim to apply a multivariate statistical method, the Generalized Equilibrium Feedback Assessment (GEFA), to evaluate the representation of the oceanic drivers of North African rainfall in the Coupled Model Intercomparison Project Phase Five (CMIP5) in comparison to a GEFA-based observational benchmark. The reliability of the statistical GEFA method is first evaluated against dynamical experiments within the Community Earth System Model (CESM), with initial focus on the atmospheric response to sea-surface temperature anomalies in the tropical Pacific and Indian Oceans. In order to estimate the minimum number of years of data needed to obtain stable GEFA response estimates to individual SST forcings, given large atmospheric internal variability, we apply GEFA to data records of varying durations from the CESM Large Ensemble historical simulations. After validating the GEFA method, we apply the statistical approach to both CESM and a range of CMIP5 models in order to elucidate the models' representation of oceanic drivers of North African rainfall. The observed oceanic forcings of North African rainfall, as investigated in a parallel study, serves as the benchmark for evaluating each model's performance and credibility in terms of future climate projections.

  5. Global Earth Response to Loading by Ocean Tide Models

    NASA Technical Reports Server (NTRS)

    Estes, R. H.; Strayer, J. M.

    1979-01-01

    Mathematical and programming techniques to numerically calculate Earth response to global semidiurnal and diurnal ocean tide models were developed. Global vertical crustal deformations were evaluated for M sub 2, S sub 2, N sub 2, K sub 2, K sub 1, O sub 1, and P sub 1 ocean tide loading, while horizontal deformations were evaluated for the M sub 2 tidal load. Tidal gravity calculations were performed for M sub 2 tidal loads, and strain tensor elements were evaluated for M sub 2 loads. The M sub 2 solution used for the ocean tide included the effects of self-gravitation and crustal loading.

  6. On the dependence of hindcast skill on ocean thermodynamics in a coupled ocean-atmosphere model

    SciTech Connect

    Kleeman, R. )

    1993-11-01

    Three different mechanisms for the generation of ENSO SST anomalies within a simplified tropical Pacific Ocean model are examined: thermocline depth changes, Ekman-induced upwelling anomalies, and zonal advection changes. The effect of varying the relative influence of these terms on the realism of tropical pacific coupled models is analyzed. The principal tool used to assess such realism is hindcast skill, with forced ocean and oscillatory behavior also being examined. Of the mechanisms considered, thermocline perturbations are shown to be crucially important for high coupled-model hindcast skills. Furthermore, it is concluded that the realism of the model (as measured by hindcast skill) deteriorates markedly when the influence on SST of Ekman upwelling becomes greater than a small fraction of the thermocline influence. This provides strong evidence for the hypothesis that Ekman upwelling anomalies (which are essentially a local response to wind stress anomalies) have only a small influence on the creation of real world SST anomalies. The implications of this latter point for coupled models involving ocean general circulation models is briefly discussed. It is also demonstrated that western boundary reflections provide a vital role by means of a negative feedback in ensuring realistic performance. The hindcast skill (as measured by NINO3 anomaly correlation) demonstrated by a model involving only the thermocline mechanism can be tuned to exceed that of the benchmark Cane and Zebiak model for hindcast lags up to 7 months (from 7 to 12 months the model skills are roughly equal). 47 refs., 32 figs.

  7. Modelling of Ocean Induced Magnetic Signals in Swarm Satellite Data

    NASA Astrophysics Data System (ADS)

    Einspigel, D.; Velimsky, J.; Martinec, Z.; Sachl, L.

    2015-12-01

    It is well known that the motion of sea water in the Earth's main magnetic field induces the secondary magnetic field which can be measured by satellite, land-based or sea surface magnetic measurements, despite being rather weak, reaching intensities of up to a few nT. We focus on the extraction of ocean induced signals from Swarm satellite data and their interpretation by a comparison with synthetic signals. Results of our modeling and data processing efforts will be presented. We use two ocean circulation models: 1) DEBOT, a barotropic model of ocean tide flow and 2) LSOMG, a baroclinic model of global ocean circulation; and two different approaches for modelling the secondary magnetic field: 1) a single-layer approximation model and 2) a three-dimensional time-domain electromagnetic induction model. Swarm data are analyzed along night-time tracks of the satellites. Only a small amount of the data can be used for the analysis of ocean-induced signals because of permanently present strong signals from the magnetosphere and disruptive effects of polar electrojets. Nevertheless, the extracted signals from selected Swarm data tracks show a relatively good coincidence with predicted signals.

  8. Improved Upper Ocean/Sea Ice Modeling in the GISS GCM for Investigating Climate Change

    NASA Technical Reports Server (NTRS)

    1998-01-01

    This project built on our previous results in which we highlighted the importance of sea ice in overall climate sensitivity by determining that for both warming and cooling climates, when sea ice was not allowed to change, climate sensitivity was reduced by 35-40%. We also modified the GISS 8 deg x lO deg atmospheric GCM to include an upper-ocean/sea-ice model involving the Semtner three-layer ice/snow thermodynamic model, the Price et al. (1986) ocean mixed layer model and a general upper ocean vertical advection/diffusion scheme for maintaining and fluxing properties across the pycnocline. This effort, in addition to improving the sea ice representation in the AGCM, revealed a number of sensitive components of the sea ice/ocean system. For example, the ability to flux heat through the ice/snow properly is critical in order to resolve the surface temperature properly, since small errors in this lead to unrestrained climate drift. The present project, summarized in this report, had as its objectives: (1) introducing a series of sea ice and ocean improvements aimed at overcoming remaining weaknesses in the GCM sea ice/ocean representation, and (2) performing a series of sensitivity experiments designed to evaluate the climate sensitivity of the revised model to both Antarctic and Arctic sea ice, determine the sensitivity of the climate response to initial ice distribution, and investigate the transient response to doubling CO2.

  9. An Analysis of an Eddy-Resolving Global Ocean Model in the Tropical Indian Ocean

    DTIC Science & Technology

    1990-09-01

    Ocean circulation. The seasonally-reversing Somali Current is simulated by the model, and includes seasonai undercurrents and a tvo-gyre system during...undercurrents and a two-gyre system during the southwest monson. Westward-flow occ,, rs beneath the Southwest Monsoon Current during June and July. The...25 F. THE SOMALI CURRENT SYSTEM ....................................... 28 G. THROUGHFLOW IN THE

  10. U. S. GODAE: Global Ocean Prediction with the HYbrid Coordinate Ocean Model

    DTIC Science & Technology

    2009-01-01

    conditions to nested models with fixed depth z-level coordinates, terrain following coordinates, generalized coordinates (HYCOM), and unstructured...ocean prediction using HYCOM. DoD HPC Users Conference Proceedings, pp. 259-262. Zamudio , L., P.J. Hogan and E.J. Metzger, 2008. Summer generation of

  11. Ocean Simulation Model. Version 2. First Order Frontal Simulation

    DTIC Science & Technology

    1991-05-01

    S2,NPTS-50 IFCXCI) .LT. XMIN) THEN XNIN=X(I) ELSE IF(X(I) .GT. XMAX) XKAX=X(I) ENDIF 818 CONTINUE C C RESCALE X,Y TO FIT IN MASK BUFFER C D=MXCOLS...INITIALIZE MASK BUFFER C 822 WRITE(tIl,824) 824 FONT(2X.’GENERATING 0 MASK’) DO 830 I~lMXROWS DO 828 Jul ,MXCOLS NASK(J, I)u1 m2 CONTINUE 830 CONTINUE C C SET...CHECK ON Q BUFFER C NOK=O u 860 I=I,MXCOLS IMINUSMO IPLUSzO DO 850 J=1,MXROWS IF(NASK(IJ) .LT. 0) THEN IMINUS=IMINUS+I ELSE IF(MASK(I,J) .GT. 0) IPLUS

  12. Adaptive h -refinement for reduced-order models: ADAPTIVE h -refinement for reduced-order models

    DOE PAGES

    Carlberg, Kevin T.

    2014-11-05

    Our work presents a method to adaptively refine reduced-order models a posteriori without requiring additional full-order-model solves. The technique is analogous to mesh-adaptive h-refinement: it enriches the reduced-basis space online by ‘splitting’ a given basis vector into several vectors with disjoint support. The splitting scheme is defined by a tree structure constructed offline via recursive k-means clustering of the state variables using snapshot data. This method identifies the vectors to split online using a dual-weighted-residual approach that aims to reduce error in an output quantity of interest. The resulting method generates a hierarchy of subspaces online without requiring large-scale operationsmore » or full-order-model solves. Furthermore, it enables the reduced-order model to satisfy any prescribed error tolerance regardless of its original fidelity, as a completely refined reduced-order model is mathematically equivalent to the original full-order model. Experiments on a parameterized inviscid Burgers equation highlight the ability of the method to capture phenomena (e.g., moving shocks) not contained in the span of the original reduced basis.« less

  13. Reduced-order modelling numerical homogenization.

    PubMed

    Abdulle, A; Bai, Y

    2014-08-06

    A general framework to combine numerical homogenization and reduced-order modelling techniques for partial differential equations (PDEs) with multiple scales is described. Numerical homogenization methods are usually efficient to approximate the effective solution of PDEs with multiple scales. However, classical numerical homogenization techniques require the numerical solution of a large number of so-called microproblems to approximate the effective data at selected grid points of the computational domain. Such computations become particularly expensive for high-dimensional, time-dependent or nonlinear problems. In this paper, we explain how numerical homogenization method can benefit from reduced-order modelling techniques that allow one to identify offline and online computational procedures. The effective data are only computed accurately at a carefully selected number of grid points (offline stage) appropriately 'interpolated' in the online stage resulting in an online cost comparable to that of a single-scale solver. The methodology is presented for a class of PDEs with multiple scales, including elliptic, parabolic, wave and nonlinear problems. Numerical examples, including wave propagation in inhomogeneous media and solute transport in unsaturated porous media, illustrate the proposed method.

  14. Parallel Computation of the Regional Ocean Modeling System (ROMS)

    SciTech Connect

    Wang, P; Song, Y T; Chao, Y; Zhang, H

    2005-04-05

    The Regional Ocean Modeling System (ROMS) is a regional ocean general circulation modeling system solving the free surface, hydrostatic, primitive equations over varying topography. It is free software distributed world-wide for studying both complex coastal ocean problems and the basin-to-global scale ocean circulation. The original ROMS code could only be run on shared-memory systems. With the increasing need to simulate larger model domains with finer resolutions and on a variety of computer platforms, there is a need in the ocean-modeling community to have a ROMS code that can be run on any parallel computer ranging from 10 to hundreds of processors. Recently, we have explored parallelization for ROMS using the MPI programming model. In this paper, an efficient parallelization strategy for such a large-scale scientific software package, based on an existing shared-memory computing model, is presented. In addition, scientific applications and data-performance issues on a couple of SGI systems, including Columbia, the world's third-fastest supercomputer, are discussed.

  15. Modeling Ability Differentiation in the Second-Order Factor Model

    ERIC Educational Resources Information Center

    Molenaar, Dylan; Dolan, Conor V.; van der Maas, Han L. J.

    2011-01-01

    In this article we present factor models to test for ability differentiation. Ability differentiation predicts that the size of IQ subtest correlations decreases as a function of the general intelligence factor. In the Schmid-Leiman decomposition of the second-order factor model, we model differentiation by introducing heteroscedastic residuals,…

  16. A world ocean model for greenhouse sensitivity studies: resolution intercomparison and the role of diagnostic forcing

    NASA Astrophysics Data System (ADS)

    Washington, Warren M.; Meehl, Gerald A.; Verplank, Lynda; Bettge, Thomas W.

    1994-05-01

    We have developed an improved version of a world ocean model with the intention of coupling to an atmospheric model. This article documents the simulation capability of this 1° global ocean model, shows improvements over our earlier 5° version, and compares it to features simulated with a 0.5° model. These experiments use a model spin-up methodology whereby the ocean model can subsequently be coupled to an atmospheric model and used for order 100-year coupled model integrations. With present-day computers, 1° is a reasonable compromise in resolution that allows for century-long coupled experiments. The 1° ocean model is derived from a 0.5°-resolution model developed by A. Semtner (Naval Postgraduate School) and R. Chervin (National Center for Atmospheric Research) for studies of the global eddy-resolving world ocean circulation. The 0.5° bottom topography and continental outlines have been altered to be compatible with the 1° resolution, and the Arctic Ocean has been added. We describe the ocean simulation characteristics of the 1° version and compare the result of weakly constraining (three-year time scale) the three-dimensional temperature and salinity fields to the observations below the thermocline (710 m) with the model forced only at the top of the ocean by observed annual mean wind stress, temperature, and salinity. The 1° simulations indicate that major ocean circulation patterns are greatly improved compared to the 5° version and are qualitatively reproduced in comparison to the 0.5° version. Using the annual mean top forcing alone in a 100-year simulation with the 1° version preserves the general features of the major observed temperature and salinity structure with most climate drift occurring mainly beneath the thermocline in the first 50 75 years. Because the thermohaline circulation in the 1° version is relatively weak with annual mean forcing, we demonstrate the importance of the seasonal cycle by performing two sensitivity experiments

  17. Nonparametric Bayes Stochastically Ordered Latent Class Models

    PubMed Central

    Yang, Hongxia; O’Brien, Sean; Dunson, David B.

    2012-01-01

    Latent class models (LCMs) are used increasingly for addressing a broad variety of problems, including sparse modeling of multivariate and longitudinal data, model-based clustering, and flexible inferences on predictor effects. Typical frequentist LCMs require estimation of a single finite number of classes, which does not increase with the sample size, and have a well-known sensitivity to parametric assumptions on the distributions within a class. Bayesian nonparametric methods have been developed to allow an infinite number of classes in the general population, with the number represented in a sample increasing with sample size. In this article, we propose a new nonparametric Bayes model that allows predictors to flexibly impact the allocation to latent classes, while limiting sensitivity to parametric assumptions by allowing class-specific distributions to be unknown subject to a stochastic ordering constraint. An efficient MCMC algorithm is developed for posterior computation. The methods are validated using simulation studies and applied to the problem of ranking medical procedures in terms of the distribution of patient morbidity. PMID:22505787

  18. On-orbit vicarious calibration of ocean color sensors using an ocean surface reflectance model.

    PubMed

    Werdell, P Jeremy; Bailey, Sean W; Franz, Bryan A; Morel, André; McClain, Charles R

    2007-08-10

    Recent advances in global biogeochemical research demonstrate a critical need for long-term ocean color satellite data records of consistent high quality. To achieve that quality, spaceborne instruments require on-orbit vicarious calibration, where the integrated instrument and atmospheric correction system is adjusted using in situ normalized water-leaving radiances, such as those collected by the marine optical buoy (MOBY). Unfortunately, well-characterized time-series of in situ data are scarce for many historical satellite missions, in particular, the NASA coastal zone color scanner (CZCS) and the ocean color and temperature scanner (OCTS). Ocean surface reflectance models (ORMs) accurately reproduce spectra observed in clear marine waters, using only chlorophyll a (C(a)) as input, a measurement for which long-term in situ time series exist. Before recalibrating CZCS and OCTS using modeled radiances, however, we evaluate the approach with the Sea-viewing Wide-Field-of-view Sensor (SeaWiFS). Using annual C(a) climatologies as input into an ORM, we derive SeaWiFS vicarious gains that differ from the operational MOBY gains by less than +/-0.9% spectrally. In the context of generating decadal C(a) climate data records, we quantify the downstream effects of using these modeled gains by generating satellite-to-in situ data product validation statistics for comparison with the operational SeaWiFS results. Finally, we apply these methods to the CZCS and OCTS ocean color time series.

  19. Interannual variability of CFC-11 absorption by the ocean: an offline model study

    NASA Astrophysics Data System (ADS)

    Valsala, Vinu; Alsibai, Hayyan M.; Ikeda, Motoyoshi; Maksyutov, Shamil

    2011-04-01

    The global ocean Chlorofluorocarbon (CFC-11) was simulated in an offline model driven by re-analysis ocean currents in order to identify the mechanisms of interannual to interdecadal variability of air-sea CFC fluxes. The model was forced with the observed anthropogenic perturbations of atmospheric CFC-11 from the post industrial period (1938) following the OCMIP-II flux protocols along with the observed winds from 1960 to 1999 in the formulation of surface gas exchanges. The model ocean CFC-11 inventories, at the end of 1990s, accounted approximately 1% of the total atmospheric CFC-11, which is consistent with the corresponding observations. The mid-to-high latitude oceans were venue for strong (weak) oceanic sinks (sources) of CFC-11 during the winter (summer) months. The Southern Ocean (south of 40°S) and the North Atlantic (north of 35°N) provided two largest sinks of CFC-11, through which 31.4 and 14.6% of the global ocean CFC-11 entered, respectively. The eastern tropical Pacific Ocean exhibited large interannual variability of CFC-11 flux with a strong (weak) sink during La Niña (El Niño) years and represented 36% of the global CFC-11 flux variability. The North Atlantic and Southern Ocean were found as regions of large sink efficiency: a capacity to sink more CFC than outsource, although it reduced by 80 and 70%, respectively, in the last 40 years compared to 1960. The sink to source ratio of global ocean CFC-11 fluxes were reduced from 90 to 50% in the last 40 years. This indicates a saturation of CFC in the above-thermocline subsurface that makes the upper ocean less efficient in absorbing CFC in recent decades. A positive trend in CFC sink is now limited to the Southern Ocean, central tropical Pacific and western boundary current regions which possess active upwelling of old water with long time since last atmospheric contact. However, a globally averaged trend was a reduced CFC-11 sink, by emitting 30% of the total ocean CFC-11 that was absorbed

  20. The Effect of Atmosphere-Ocean-Wave Interactions and Model Resolution on Hurricane Katrina in a Coupled Regional Climate Model

    NASA Astrophysics Data System (ADS)

    Patricola, C. M.; Chang, P.; Saravanan, R.; Montuoro, R.

    2012-04-01

    The sensitivity of simulated strength, track, and structure of Hurricane Katrina to atmospheric model resolution, cumulus parameterization, and initialization time, as well as mesoscale ocean-atmosphere interactions with and without small-scale ocean-wave effect, are investigated with a fully coupled regional climate model. The atmosphere, ocean, and wave components are represented by the Weather Research and Forecasting Model (WRF), Regional Ocean Modeling System (ROMS), and Simulating WAves Nearshore (SWAN) model. Uncoupled atmosphere-only simulations with horizontal resolutions of 1, 3, 9, and 27 km show that while the simulated cyclone track is highly sensitive to initialization time, its dependence on model resolution is relatively weak. Using NCEP/CFSR reanalysis as initial and boundary conditions, WRF, even at low resolution, is able to track Katrina accurately for 3 days before it made landfall on August 29, 2005. Katrina's strength, however, is much more difficult to reproduce and exhibits a strong dependence on model resolution. At its lowest resolution (27 km), WRF is only capable of simulating a maximum strength of Category 2 storm. Even at 1 km resolution, the simulated Katrina only reaches Category 4 storm intensity. Further WRF experiments with and without cumulus parameterization reveal minor changes in strength. None of the WRF-only simulations capture the observed rapid intensification of Katrina to Category 5 when it passed over a warm Loop-Current eddy (LCE) in the Gulf of Mexico, suggesting that mesoscale ocean-atmosphere interactions involving LCEs may play a crucial role in Katrina's rapid intensification. Coupled atmosphere-ocean simulations are designed and carried out to investigate hurricane Katrina-LCE interactions with and without considering small-scale ocean wave processes in order to fully understand the dynamical ocean-atmosphere processes in the observed rapid cyclone intensification.

  1. (CO sub 2 uptake in an Ocean Circulation Model)

    SciTech Connect

    Siegenthaler, U.C.

    1990-11-06

    The traveler collaborated with Drs. J. L. Sarmiento and J. C. Orr of the Program in Atmospheric Sciences at Princeton University to finish the article A Perturbation Simulation of CO{sub 2} Uptake in an Ocean Circulation Model,'' which has been submitted to the Journal of Geophysical Research for publication. With F. Joos, a graduate student from the University of Bern, the traveler started writing a journal article describing a box model of the global carbon cycle that is an extension of the one-dimensional box-diffusion model. The traveler further collaborated with F. Joos and Dr. J. L. Sarmiento on modeling the potential enhancement of oceanic CO{sub 2} uptake by fertilizing the southern ocean with iron. A letter describing the results is currently being written for the journal Nature.

  2. Predictability of a coupled ocean-atmosphere model

    NASA Technical Reports Server (NTRS)

    Goswami, B. N.; Shukla, J.

    1991-01-01

    A study is presented to determine the limits on the predictability of the coupled ocean-atmosphere system. Following the classical methods developed for atmospheric predictability studies, the model used is one of the simplest that realistically reproduces many of the important features of the observed interannual variability of sea surface temperature in the tropical Pacific Ocean when forced by observed wind stresses. As no reasonable analysis is available for all the fields, initial conditions for these prediction experiments were taken from a model control run in which the ocean model was forced by the observed surface winds. The atmospheric component of the coupled model is not capable of accurately simulating the large-scale components of the observed wind stress.

  3. Seasonal heat and freshwater cycles in the Arctic Ocean in CMIP5 coupled models

    NASA Astrophysics Data System (ADS)

    Ding, Yanni; Carton, James A.; Chepurin, Gennady A.; Steele, Michael; Hakkinen, Sirpa

    2016-04-01

    This study examines the processes governing the seasonal response of the Arctic Ocean and sea ice to surface forcings as they appear in historical simulations of 14 Coupled Model Intercomparison Project Phase 5 coupled climate models. In both models and observations, the seasonal heat budget is dominated by a local balance between net surface heating and storage in the heat content of the ocean and in melting/freezing of sea ice. Observations suggest ocean heat storage is more important than sea ice melt, while in most of these models, sea ice melt dominates. Seasonal horizontal heat flux divergence driven by the seasonal cycle of volume transport is only important locally. In models and observations, the dominant terms in the basin-average seasonal freshwater budget are the storages of freshwater between the ocean and sea ice, and the exchange between the two. The largest external source term is continental discharge in early summer, which is an order of magnitude smaller. The appearance of sea ice (extent and volume) and also ocean stratification in both the heat and freshwater budgets provides two links between the budgets and provides two mechanisms for feedback. One consequence of such an interaction is the fact that models with strong/weak seasonal surface heating also have strong/weak seasonal haline and temperature stratification.

  4. A Community Terrain-Following Ocean Modeling System

    DTIC Science & Technology

    2002-09-30

    turbulent closure model for geophysical fluid problems. Rev. Geophys., 20, 851-875. Mellor, G. L., S. Hakkinen and T. Ezer and R. Patchen, 2002: A...Analysis of results from a numerical ocean model, J. Geophys. Res., 10.1029/2002JC001509. Mellor, G. L., S. Hakkinen and T. Ezer and R. Patchen, 2002: A

  5. Colombian ocean waves and coasts modeled by special functions

    NASA Astrophysics Data System (ADS)

    Duque Tisnés, Simón

    2013-06-01

    Modeling the ocean bottom and surface of both Atlantic and Pacific Oceans near the Colombian coast is a subject of increasing attention due to the possibility of finding oil deposits that haven't been discovered, and as a way of monitoring the ocean limits of Colombia with other countries not only covering the possibility of naval intrusion but as a chance to detect submarine devices that are used by illegal groups for different unwished purposes. In the development of this topic it would be necessary to use Standard Hydrodynamic Equations to model the mathematical shape of ocean waves that will take differential equations forms. Those differential equations will be solved using computer algebra software and methods. The mentioned solutions will involve the use of Special Functions such as Bessel Functions, Whittaker, Heun, and so on. Using the Special Functions mentioned above, the obtained results will be simulated by numerical methods obtaining the typical patterns around the Colombian coasts (both surface and bottom). Using this simulation as a non-perturbed state, any change in the patter could be taken as an external perturbation caused by a strange body or device in an specific area or region modeled, building this simulation as an ocean radar or an unusual object finder. It's worth mentioning that the use of stronger or more rigorous methods and more advanced Special Functions would generate better theoretical results, building a more accurate simulation model that would lead to a finest detection.

  6. Multiresolution in CROCO (Coastal and Regional Ocean Community model)

    NASA Astrophysics Data System (ADS)

    Debreu, Laurent; Auclair, Francis; Benshila, Rachid; Capet, Xavier; Dumas, Franck; Julien, Swen; Marchesiello, Patrick

    2016-04-01

    CROCO (Coastal and Regional Ocean Community model [1]) is a new oceanic modeling system built upon ROMS_AGRIF and the non-hydrostatic kernel of SNH, gradually including algorithms from MARS3D (sediments)and HYCOM (vertical coordinates). An important objective of CROCO is to provide the possibility of running truly multiresolution simulations. Our previous work on structured mesh refinement [2] allowed us to run two-way nesting with the following major features: conservation, spatial and temporal refinement, coupling at the barotropic level. In this presentation, we will expose the current developments in CROCO towards multiresolution simulations: connection between neighboring grids at the same level of resolution and load balancing on parallel computers. Results of preliminary experiments will be given both on an idealized test case and on a realistic simulation of the Bay of Biscay with high resolution along the coast. References: [1] : CROCO : http://www.croco-ocean.org [2] : Debreu, L., P. Marchesiello, P. Penven, and G. Cambon, 2012: Two-way nesting in split-explicit ocean models: algorithms, implementation and validation. Ocean Modelling, 49-50, 1-21.

  7. The ocean quasi-homogeneous layer model and global cycle of carbon dioxide in system of atmosphere-ocean

    NASA Astrophysics Data System (ADS)

    Glushkov, Alexander; Glushkov, Alexander; Loboda, Nataliya; Khokhlov, Valery; Serbov, Nikoly; Svinarenko, Andrey

    The purpose of this paper is carrying out the detailed model of the CO2 global turnover in system of "atmosphere-ocean" with using the ocean quasi-homogeneous layer model. Practically all carried out models are functioning in the average annual regime and accounting for the carbon distribution in bio-sphere in most general form (Glushkov et al, 2003). We construct a modified model for cycle of the carbon dioxide, which allows to reproduce a season dynamics of carbon turnover in ocean with account of zone ocean structure (up quasi-homogeneous layer, thermocline and deepest layer). It is taken into account dependence of the CO2 transfer through the bounder between atmosphere and ocean upon temperature of water and air, wind velocity, buffer mechanism of the CO2 dissolution. The same program is realized for atmosphere part of whole system. It is obtained a tempo-ral and space distribution for concentration of non-organic carbon in ocean, partial press of dissolute CO2 and value of exchange on the border between atmosphere and ocean. It is estimated a role of the wind intermixing of the up ocean layer. The increasing of this effect leads to increasing the plankton mass and further particles, which are transferred by wind, contribute to more quick immersion of microscopic shells and organic material. It is fulfilled investigation of sen-sibility of the master differential equations system solutions from the model parameters. The master differential equa-tions system, describing a dynamics of the CO2 cycle, is numerically integrated by the four order Runge-Cutt method under given initial values of valuables till output of solution on periodic regime. At first it is indicated on possible real-zation of the chaos scenario in system. On our data, the difference of the average annual values for the non-organic car-bon concentration in the up quasi-homogeneous layer between equator and extreme southern zone is 0.15 mol/m3, be-tween the equator and extreme northern zone is 0

  8. Numerical modelling of floating debris in the world's oceans.

    PubMed

    Lebreton, L C-M; Greer, S D; Borrero, J C

    2012-03-01

    A global ocean circulation model is coupled to a Lagrangian particle tracking model to simulate 30 years of input, transport and accumulation of floating debris in the world ocean. Using both terrestrial and maritime inputs, the modelling results clearly show the formation of five accumulation zones in the subtropical latitudes of the major ocean basins. The relative size and concentration of each clearly illustrate the dominance of the accumulation zones in the northern hemisphere, while smaller seas surrounded by densely populated areas are also shown to have a high concentration of floating debris. We also determine the relative contribution of different source regions to the total amount of material in a particular accumulation zone. This study provides a framework for describing the transport, distribution and accumulation of floating marine debris and can be continuously updated and adapted to assess scenarios reflecting changes in the production and disposal of plastic worldwide.

  9. Estimating the numerical diapycnal mixing in the GO5.0 ocean model

    NASA Astrophysics Data System (ADS)

    Megann, Alex; Nurser, George

    2014-05-01

    Constant-depth (or "z-coordinate") ocean models such as MOM and NEMO have become the de facto workhorse in climate applications, and have attained a mature stage in their development and are well understood. A generic shortcoming of this model type, however, is a tendency for the advection scheme to produce unphysical numerical diapycnal mixing, which in some cases may exceed the explicitly parameterised mixing based on observed physical processes (e.g. Hofmann and Maqueda, 2006), and this is likely to have effects on the long-timescale evolution of the simulated climate system. Despite this, few quantitative estimations have been made of the typical magnitude of the effective diapycnal diffusivity due to numerical mixing in these models. GO5.0 is the latest ocean model configuration developed jointly by the UK Met Office and the National Oceanography Centre (Megann et al, 2013). It uses version 3.4 of the NEMO model, on the ORCA025 global tripolar grid. Two approaches to quantifying the numerical diapycnal mixing in this model are described: the first is based on the isopycnal watermass analysis of Lee et al (2002), while the second uses a passive tracer to diagnose mixing across density surfaces. Results from these two methods will be compared and contrasted. Hofmann, M. and Maqueda, M. A. M., 2006. Performance of a second-order moments advection scheme in an ocean general circulation model. JGR-Oceans, 111(C5). Lee, M.-M., Coward, A.C., Nurser, A.G., 2002. Spurious diapycnal mixing of deep waters in an eddy-permitting global ocean model. JPO 32, 1522-1535 Megann, A., Storkey, D., Aksenov, Y., Alderson, S., Calvert, D., Graham, T., Hyder, P., Siddorn, J., and Sinha, B., 2013: GO5.0: The joint NERC-Met Office NEMO global ocean model for use in coupled and forced applications, Geosci. Model Dev. Discuss., 6, 5747-5799,.

  10. An improved model for the microwave brightness temperature seen from space over calm ocean

    NASA Astrophysics Data System (ADS)

    Cruz-Pol, Sandra L.

    An improved model for the microwave brightness temperature seen from space over calm ocean is presented. This model can be divided into two sub-models, the atmospheric absorption model and the ocean surface emissivity model. An improved model for the absorption of the atmosphere near the 22 GHz water vapor line is presented in the first part of this work. The Van-Vleck-Weisskopf line shape is used with a simple parameterized version of the model from Liebe for the water vapor absorption spectra and a scaling of the model from Rosenkranz for the 20-32 GHz oxygen absorption. Radiometric brightness temperature measurements from two sites of contrasting climatological properties-San Diego, CA and West Palm Beach, FL-are used as ground truth for comparison with in situ radiosonde derived brightness temperatures. Estimation of the new model's four parameters, related to water vapor line strength, line width and continuum absorption, and far-wing oxygen absorption, are performed using the Newton-Raphson inversion method. Improvements to the water vapor line strength and line width parameters are found to be statistically significant. The accuracy of brightness temperatures computed using the improved model is 1.3-2% near 22 GHz. In the second part of this work, a modified ocean emissivity model is presented. We investigate the contribution to the brightness temperature from the specular ocean emission. For this purpose, satellite- based microwave radiometric measurements from the TOPEX/Poseidon project are employed together with near- coincident radiosonde profiles from fifteen stations around the world's oceans and TOPEX altimeter measurements for filtering of low wind conditions. The radiative transfer equation is applied to these profiles, using the atmospheric model developed in part one, in order to account for atmospheric effects in the modeled brightness temperature. NODC ocean temperature and salinity profiles are used in determining the dielectric properties of

  11. Assimilation of SeaWiFS Ocean Chlorophyll Data into a Three-Dimensional Global Ocean Model

    NASA Technical Reports Server (NTRS)

    Gregg, Watson W.

    2005-01-01

    Assimilation of satellite ocean color data is a relatively new phenomenon in ocean sciences. However, with routine observations from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS), launched in late 1997, and now with new data from the Moderate Resolution Imaging Spectroradometer (MODIS) Aqua, there is increasing interest in ocean color data assimilation. Here SeaWiFS chlorophyll data were assimilated with an established thre-dimentional global ocean model. The assimilation improved estimates of hlorophyll and primary production relative to a free-run (no assimilation) model. This represents the first attempt at ocean color data assimilation using NASA satellites in a global model. The results suggest the potential of assimilation of satellite ocean chlorophyll data for improving models.

  12. An Extensible Reduced Order Model Builder for Simulation and Modeling

    SciTech Connect

    2012-09-28

    REVEAL is a software framework for building reduced order models (surrogate models) for high fidelity complex scientific simulations. REVEAL is designed to do reduced order modeling and sensitivity analysis for scientific simulations. REVEAL incorporates a range of sampling and regression methods. It provides complete user environment and is adaptable to new simulators, runs jobs on any computing platform of choice, automatically post processes simulation results and provides a range of data analysis tools. The software is generic and can easily be extended to incorporate new methods, simulators.

  13. Ocean Dynamics Simulation during an Extreme Bora Event using a Two-Way Coupled Atmosphere-Ocean Modeling System

    NASA Astrophysics Data System (ADS)

    Licer, Matjaz; Smerkol, Peter; Fettich, Anja; Ravdas, Michalis; Papapostolou, Alexandros; Mantziafou, Anneta; Cedilnik, Jure; Strajnar, Benedikt; Jeromel, Maja; Pristov, Neva; Jerman, Jure; Petan, Saso; Malacic, Vlado; Sofianos, Sarantis

    2015-04-01

    The response of the Adriatic Sea to cold north-easterly Bora wind forcing has been modelled numerous times, but usually using one-way coupling techniques. One of the most significant events of the kind took place in February 2012, when hurricane force Bora was blowing over the Northern Adriatic almost continuously for over three weeks, causing extreme air-sea interactions leading to severe water cooling (below 4 degrees Celsius) and extensive dense water formation (with density anomalies above 30.5 kg/m3). The intensity of the atmosphere-ocean interactions during such conditions calls for a two-way atmosphere-ocean coupling approach. We compare the performances of a) fully two-way coupled atmosphere-ocean modelling system and b) one way coupled ocean model (forced by the atmospheric model hourly output) to the available in-situ measurements (coastal buoy, CTD). The models used were ALADIN (4.4 km resolution) on the atmospheric side and POM (1/30°× 1/30° resolution) on the ocean side. The atmosphere-ocean coupling was implemented using the OASIS3-MCT model coupling toolkit. We show that the atmosphere-ocean two-way coupling significantly improves the simulated temperature and density response of the ocean since it represents short-termed transient features much better than the offline version of the ocean model.

  14. Numerically modelling tidal dissipation with bottom drag in the oceans of Titan and Enceladus

    NASA Astrophysics Data System (ADS)

    Hay, Hamish C. F. C.; Matsuyama, Isamu

    2017-01-01

    Icy satellites that contain subsurface oceans require sufficient thermal energy to prevent the liquid portion of their interiors from freezing. We develop a numerical finite difference model to solve the Laplace Tidal Equations on a sphere in order to simulate tidal flow and thermal energy dissipation in these oceans, neglecting the presence of an icy lid. The model is applied to Titan and Enceladus, where we explore how Rayleigh (linear) and bottom (quadratic) drag terms affect dissipation. The latter drag regime can only be applied numerically. We find excellent agreement between our results and recent analytical work. Obliquity tide Rossby-wave resonant features become independent of ocean thickness under the bottom drag regime for thick oceans. We show that for Titan, dissipation from this Rossby-wave resonance can act to dampen the rate of outward orbital migration by up to 40% for Earth-like values of bottom drag coefficient. Gravity-wave resonances can act to cause inward migration, although this is unlikely due to the thin oceans required to form such resonances. The same is true of all eccentricity tide resonances on Enceladus, such that dissipation becomes negligible for thick oceans under the bottom drag regime.

  15. Climate Ocean Modeling on a Beowulf Class System

    NASA Technical Reports Server (NTRS)

    Cheng, B. N.; Chao, Y.; Wang, P.; Bondarenko, M.

    2000-01-01

    With the growing power and shrinking cost of personal computers. the availability of fast ethernet interconnections, and public domain software packages, it is now possible to combine them to build desktop parallel computers (named Beowulf or PC clusters) at a fraction of what it would cost to buy systems of comparable power front supercomputer companies. This led as to build and assemble our own sys tem. specifically for climate ocean modeling. In this article, we present our experience with such a system, discuss its network performance, and provide some performance comparison data with both HP SPP2000 and Cray T3E for an ocean Model used in present-day oceanographic research.

  16. Generalized Reduced Order Modeling of Aeroservoelastic Systems

    NASA Astrophysics Data System (ADS)

    Gariffo, James Michael

    Transonic aeroelastic and aeroservoelastic (ASE) modeling presents a significant technical and computational challenge. Flow fields with a mixture of subsonic and supersonic flow, as well as moving shock waves, can only be captured through high-fidelity CFD analysis. With modern computing power, it is realtively straightforward to determine the flutter boundary for a single structural configuration at a single flight condition, but problems of larger scope remain quite costly. Some such problems include characterizing a vehicle's flutter boundary over its full flight envelope, optimizing its structural weight subject to aeroelastic constraints, and designing control laws for flutter suppression. For all of these applications, reduced-order models (ROMs) offer substantial computational savings. ROM techniques in general have existed for decades, and the methodology presented in this dissertation builds on successful previous techniques to create a powerful new scheme for modeling aeroelastic systems, and predicting and interpolating their transonic flutter boundaries. In this method, linear ASE state-space models are constructed from modal structural and actuator models coupled to state-space models of the linearized aerodynamic forces through feedback loops. Flutter predictions can be made from these models through simple eigenvalue analysis of their state-transition matrices for an appropriate set of dynamic pressures. Moreover, this analysis returns the frequency and damping trend of every aeroelastic branch. In contrast, determining the critical dynamic pressure by direct time-marching CFD requires a separate run for every dynamic pressure being analyzed simply to obtain the trend for the critical branch. The present ROM methodology also includes a new model interpolation technique that greatly enhances the benefits of these ROMs. This enables predictions of the dynamic behavior of the system for flight conditions where CFD analysis has not been explicitly

  17. Modelling the turbulence of a freezing Martian ocean

    NASA Astrophysics Data System (ADS)

    Kiss, Gabor; Leitner, Johannes; Firneis, Maria

    2015-04-01

    We modified the General Ocean Turbulence Model (GOTM) to fit simulations investigating the hypotheses of early oceans or seas on planet Mars. Observed morphologies like paleoshorelines (Parker et al. 1987, Carr et al. 2003) and buried craters (Boyce et al. 2005, Head et al. 2002) indicate possible processes which could have been caused by large standing open bodies of water in the northern hemisphere of Mars. These structures, as well as altitude measurements of delta networks (diAchille et al. 2010) proclaim various sizes of oceans and or seas. Evidence for their existence whether one or more at different times in the early history of the planet, or the evolution and fate of an ocean are still elusive. The smoothness of the northern plains is debated, to be the result of volcanic effluents followed by the deposition of the sedimental load called the Vastias Borealis Formation (VBF). Detailed observations of crater depths (d/D ratios) in the northern hemisphere have shown further arguments for a northern ocean. The prevailing opinion is a short life of a liquid ocean, and a rather fast freezing period leading to sublimation under a thin atmosphere. McKay et al. (1990) have shown that liquid habitats could be maintained under an ice sheet for up to several hundred million years, if melt/freshwater and or volcanic activity was supported. Using the atmospheric data of the GCM (Forget et al. 1999) as input parameters for temperature and wind velocities, we simulate an ocean exposed from mild to freezing temperatures of water at different atmospheric pressures. We are investigating the detailed effects of turbulence on the ocean or sea floors, as well as the effects of salinity and freshwater inflow on the Martian soil. Apart from the driving forces like fed of outflow channels and or rivers and wind, the duration of liquid water is a key question on the redistribution of sediments and the formation of coastal structures.

  18. A Conceptual Model for Extratropical Atmosphere-ocean Interaction

    NASA Astrophysics Data System (ADS)

    Zhao, B.; Reichler, T.

    2015-12-01

    Equipped with the current understanding for atmosphere-ocean interaction, we build a simple physically-based system of coupled equations to portray the relationships among major atmospheric and oceanic modes, including the NAO, AMO, AMOC, ENSO and stratospheric NAM. The simple model reproduces the strongly timescale-dependent character of the relationships, which changes in strength and direction on scales ranging from days to centuries. Another emphasis is placed on explicitly resolving the air-sea heat fluxes as a function of timescale to provide insight into the coupling between ocean and atmosphere. In constructing and testing the simple model we make use of a multi-millennium-long control integration with a fully coupled climate model. Cross-correlation, spectral analysis and inverse methods are employed to characterize important aspects of the interactions in the full and simple models. It is found that, a) Bjerknes' conjecture on ocean-atmosphere coupling, that is the atmosphere drives climate on high frequencies (days to months) while the ocean acts as the main source of climate variability on interannual and longer timescales, is confirmed; b) the AMOC can be readily understood as a harmonic oscillator driven by the NAO; c) the two-way interaction between NAO and AMO, and also the influence of ENSO on both NAO and AMO are essential for reproducing important correlation features; and d) the consideration of heat fluxes provides additional explanatory power to our model. Our approach not only helps to clarify our understanding for the nature of the atmosphere-ocean interaction problem but also raises new and intriguing questions for future research.

  19. The Marine Virtual Laboratory: enabling efficient ocean model configuration

    NASA Astrophysics Data System (ADS)

    Oke, P. R.; Proctor, R.; Rosebrock, U.; Brinkman, R.; Cahill, M. L.; Coghlan, I.; Divakaran, P.; Freeman, J.; Pattiaratchi, C.; Roughan, M.; Sandery, P. A.; Schaeffer, A.; Wijeratne, S.

    2015-11-01

    The technical steps involved in configuring a regional ocean model are analogous for all community models. All require the generation of a model grid, preparation and interpolation of topography, initial conditions, and forcing fields. Each task in configuring a regional ocean model is straight-forward - but the process of downloading and reformatting data can be time-consuming. For an experienced modeller, the configuration of a new model domain can take as little as a few hours - but for an inexperienced modeller, it can take much longer. In pursuit of technical efficiency, the Australian ocean modelling community has developed the Web-based MARine Virtual Laboratory (WebMARVL). WebMARVL allows a user to quickly and easily configure an ocean general circulation or wave model through a simple interface, reducing the time to configure a regional model to a few minutes. Through WebMARVL, a user is prompted to define the basic options needed for a model configuration, including the: model, run duration, spatial extent, and input data. Once all aspects of the configuration are selected, a series of data extraction, reprocessing, and repackaging services are run, and a "take-away bundle" is prepared for download. Building on the capabilities developed under Australia's Integrated Marine Observing System, WebMARVL also extracts all of the available observations for the chosen time-space domain. The user is able to download the take-away bundle, and use it to run the model of their choice. Models supported by WebMARVL include three community ocean general circulation models, and two community wave models. The model configuration from the take-away bundle is intended to be a starting point for scientific research. The user may subsequently refine the details of the model set-up to improve the model performance for the given application. In this study, WebMARVL is described along with a series of results from test cases comparing WebMARVL-configured models to observations

  20. Decadal-Scale Response of the Antarctic Ice sheet to a Warming Ocean using the POPSICLES Coupled Ice Sheet-Ocean model

    NASA Astrophysics Data System (ADS)

    Martin, D. F.; Asay-Davis, X.; Cornford, S. L.; Price, S. F.; Ng, E. G.; Collins, W.

    2015-12-01

    We present POPSICLES simulation results covering the full Antarctic Ice Sheet and the Southern Ocean spanning the period from 1990 to 2010. We use the CORE v. 2 interannual forcing data to force the ocean model. Simulations are performed at 0.1o(~5 km) ocean resolution with adaptive ice sheet resolution as fine as 500 m to adequately resolve the grounding line dynamics. We discuss the effect of improved ocean mixing and subshelf bathymetry (vs. the standard Bedmap2 bathymetry) on the behavior of the coupled system, comparing time-averaged melt rates below a number of major ice shelves with those reported in the literature. We also present seasonal variability and decadal melting trends from several Antarctic regions, along with the response of the ice shelves and the consequent dynamic response of the grounded ice sheet.POPSICLES couples the POP2x ocean model, a modified version of the Parallel Ocean Program, and the BISICLES ice-sheet model. POP2x includes sub-ice-shelf circulation using partial top cells and the commonly used three-equation boundary layer physics. Standalone POP2x output compares well with standard ice-ocean test cases (e.g., ISOMIP) and other continental-scale simulations and melt-rate observations. BISICLES makes use of adaptive mesh refinement and a 1st-order accurate momentum balance similar to the L1L2 model of Schoof and Hindmarsh to accurately model regions of dynamic complexity, such as ice streams, outlet glaciers, and grounding lines. Results of BISICLES simulations have compared favorably to comparable simulations with a Stokes momentum balance in both idealized tests (MISMIP-3d) and realistic configurations.The figure shows the BISICLES-computed vertically-integrated grounded ice velocity field 5 years into a 20-year coupled full-continent Antarctic-Southern-Ocean simulation. Submarine melt rates are painted onto the surface of the floating ice shelves. Grounding lines are shown in green.

  1. Climate impacts on ocean acidification in the North Sea and Baltic Sea: a modelling study

    NASA Astrophysics Data System (ADS)

    Daewel, Ute; Schrum, Corinna; Pushpadas, Dhanya

    2013-04-01

    CO2 increase in the atmosphere does not only potentially change the overall climate, but also increase the dissolved inorganic carbon (DIC) content in the ocean by ocean-atmosphere gas exchange leading to a decrease in oceanic ph (acidification). Hence, it has both direct (via acidification) and indirect (via changes in atmospheric fields) implications for marine ecosystems and their productivity. On the other hand, changes in primary production would likewise impact the DIC content and could potentially alter the process of acidification on different temporal scales (seasonal, inter-annual, and decadal). Here, we extended the 3d coupled ecosystem model ECOSMO II by formulations for carbon chemistry and applied the model system to the North Sea and Baltic Sea in order to investigate ocean acidification in that specific region. We specifically aim in disentangling direct and indirect impacts of changes in atmospheric CO2 on acidification. Therefore we will first, present results from a multi-decadal model hind cast (1948-2008) to describe the dynamics in ocean acidification with respect to the different time scales. Secondly, we apply downscaled products from General Circulation Models to project future climate impacts (2070-2100) on acidification. And thirdly, we will present results from cross-experiments, where we investigate the influence of future CO2 increase under present day atmospheric condition and vice versa. These scenarios allow disentangling the direct and indirect impacts on the process of acidification comparative in the North Sea and Baltic Sea.

  2. U.S. GODAE: Global Ocean Prediction with the HYbrid Coordinate Ocean Model

    DTIC Science & Technology

    2007-09-30

    models with fixed depth z-level coordinates, terrain following coordinates, generalized coordinates (HYCOM), and unstructured grids. (5) To facilitate...days of atmospheric forecast forcing. A total of 8007 temperature profiles from fixed buoys and ARGO floats (fairly evenly distributed between 65°S...E.P. Chassignet and G. Halliwell, 2006: Value of bulk heat flux parameterizations for ocean SST prediction. J. Mar. Sys. (submitted) Zamudio , L

  3. Stochastic modeling of inhomogeneous ocean waves

    NASA Astrophysics Data System (ADS)

    Smit, P. B.; Janssen, T. T.; Herbers, T. H. C.

    2015-12-01

    Refraction of swell waves in coastal waters can result in fast-scale variations of wave statistics due to wave interference. These variations cannot be resolved by wave models based on the radiative transport equation. More advanced models based on quasi-coherent theory, a generalization of the radiative transfer equation, can be coupled or nested into larger-scale models to resolve such local inhomogeneous effects. However, source terms for quasi-coherent models to account for non-conservative and nonlinear effects are not available, which hampers their operational use. In the present work we revisit the derivation of quasi-coherent theory to consistently include a source term for dissipation associated with depth-induced wave breaking. We demonstrate how general source terms can be incorporated in this class of models and compare model simulations with the new dissipation term to laboratory observations of focusing and breaking waves over a submerged shoal. The results show that a consistent derivation of source terms is essential to accurately capture coherent effects in coastal areas. Specifically, our results show that if coherent effects are ignored in the dissipation term, interference effects are strongly exaggerated. With the development of source terms for quasi-coherent models they can be effectively nested inside or otherwise coupled to larger-scale wave models to efficiently improve operational predictive capability of wave models near the coast.

  4. Arctic pathways of Pacific Water: Arctic Ocean Model Intercomparison experiments.

    PubMed

    Aksenov, Yevgeny; Karcher, Michael; Proshutinsky, Andrey; Gerdes, Rüdiger; de Cuevas, Beverly; Golubeva, Elena; Kauker, Frank; Nguyen, An T; Platov, Gennady A; Wadley, Martin; Watanabe, Eiji; Coward, Andrew C; Nurser, A J George

    2016-01-01

    Pacific Water (PW) enters the Arctic Ocean through Bering Strait and brings in heat, fresh water, and nutrients from the northern Bering Sea. The circulation of PW in the central Arctic Ocean is only partially understood due to the lack of observations. In this paper, pathways of PW are investigated using simulations with six state-of-the art regional and global Ocean General Circulation Models (OGCMs). In the simulations, PW is tracked by a passive tracer, released in Bering Strait. Simulated PW spreads from the Bering Strait region in three major branches. One of them starts in the Barrow Canyon, bringing PW along the continental slope of Alaska into the Canadian Straits and then into Baffin Bay. The second begins in the vicinity of the Herald Canyon and transports PW along the continental slope of the East Siberian Sea into the Transpolar Drift, and then through Fram Strait and the Greenland Sea. The third branch begins near the Herald Shoal and the central Chukchi shelf and brings PW into the Beaufort Gyre. In the models, the wind, acting via Ekman pumping, drives the seasonal and interannual variability of PW in the Canadian Basin of the Arctic Ocean. The wind affects the simulated PW pathways by changing the vertical shear of the relative vorticity of the ocean flow in the Canada Basin.

  5. Arctic pathways of Pacific Water: Arctic Ocean Model Intercomparison experiments

    PubMed Central

    Karcher, Michael; Proshutinsky, Andrey; Gerdes, Rüdiger; de Cuevas, Beverly; Golubeva, Elena; Kauker, Frank; Nguyen, An T.; Platov, Gennady A.; Wadley, Martin; Watanabe, Eiji; Coward, Andrew C.; Nurser, A. J. George

    2016-01-01

    Abstract Pacific Water (PW) enters the Arctic Ocean through Bering Strait and brings in heat, fresh water, and nutrients from the northern Bering Sea. The circulation of PW in the central Arctic Ocean is only partially understood due to the lack of observations. In this paper, pathways of PW are investigated using simulations with six state‐of‐the art regional and global Ocean General Circulation Models (OGCMs). In the simulations, PW is tracked by a passive tracer, released in Bering Strait. Simulated PW spreads from the Bering Strait region in three major branches. One of them starts in the Barrow Canyon, bringing PW along the continental slope of Alaska into the Canadian Straits and then into Baffin Bay. The second begins in the vicinity of the Herald Canyon and transports PW along the continental slope of the East Siberian Sea into the Transpolar Drift, and then through Fram Strait and the Greenland Sea. The third branch begins near the Herald Shoal and the central Chukchi shelf and brings PW into the Beaufort Gyre. In the models, the wind, acting via Ekman pumping, drives the seasonal and interannual variability of PW in the Canadian Basin of the Arctic Ocean. The wind affects the simulated PW pathways by changing the vertical shear of the relative vorticity of the ocean flow in the Canada Basin. PMID:27818853

  6. Arctic pathways of Pacific Water: Arctic Ocean Model Intercomparison experiments

    NASA Astrophysics Data System (ADS)

    Aksenov, Yevgeny; Karcher, Michael; Proshutinsky, Andrey; Gerdes, Rüdiger; de Cuevas, Beverly; Golubeva, Elena; Kauker, Frank; Nguyen, An T.; Platov, Gennady A.; Wadley, Martin; Watanabe, Eiji; Coward, Andrew C.; Nurser, A. J. George

    2016-01-01

    Pacific Water (PW) enters the Arctic Ocean through Bering Strait and brings in heat, fresh water, and nutrients from the northern Bering Sea. The circulation of PW in the central Arctic Ocean is only partially understood due to the lack of observations. In this paper, pathways of PW are investigated using simulations with six state-of-the art regional and global Ocean General Circulation Models (OGCMs). In the simulations, PW is tracked by a passive tracer, released in Bering Strait. Simulated PW spreads from the Bering Strait region in three major branches. One of them starts in the Barrow Canyon, bringing PW along the continental slope of Alaska into the Canadian Straits and then into Baffin Bay. The second begins in the vicinity of the Herald Canyon and transports PW along the continental slope of the East Siberian Sea into the Transpolar Drift, and then through Fram Strait and the Greenland Sea. The third branch begins near the Herald Shoal and the central Chukchi shelf and brings PW into the Beaufort Gyre. In the models, the wind, acting via Ekman pumping, drives the seasonal and interannual variability of PW in the Canadian Basin of the Arctic Ocean. The wind affects the simulated PW pathways by changing the vertical shear of the relative vorticity of the ocean flow in the Canada Basin.

  7. Gravity model improvement investigation. [improved gravity model for determination of ocean geoid

    NASA Technical Reports Server (NTRS)

    Siry, J. W.; Kahn, W. D.; Bryan, J. W.; Vonbun, F. F.

    1973-01-01

    This investigation was undertaken to improve the gravity model and hence the ocean geoid. A specific objective is the determination of the gravity field and geoid with a space resolution of approximately 5 deg and a height resolution of the order of five meters. The concept of the investigation is to utilize both GEOS-C altimeter and satellite-to-satellite tracking data to achieve the gravity model improvement. It is also planned to determine the geoid in selected regions with a space resolution of about a degree and a height resolution of the order of a meter or two. The short term objectives include the study of the gravity field in the GEOS-C calibration area outlined by Goddard, Bermuda, Antigua, and Cape Kennedy, and also in the eastern Pacific area which is viewed by ATS-F.

  8. Variability of the thermohaline circulation in a simple coupled atmosphere-ocean model

    NASA Astrophysics Data System (ADS)

    Taboada, J. J.; Lorenzo, M. N.

    2003-04-01

    The behavior of the Atlantic thermohaline circulation (THC) is essential to a better understanding of climate change. Paleoclimatic studies suggest that this circulation has experimented repeated changes throughout the history of the Earth associated to climate changes [1]. The coupled 3-dimensional climate models are useful in quantitatively assessing the details of the thermohaline circulation and for comparison with observations. However, the currently available computing capacity reduces the possibility of carry out exhaustive parametric studies of the THC. Models of reduced complexity can help overcome this difficulty and make valuable contributions to a better understanding of parameter space. Moreover, these models are most useful as exploratory tools for hypothesis building. Here we study a low-order coupled atmosphere-ocean general circulation model in order to understand the behavior of the thermohaline circulation through different changes on the interaction between atmosphere-ocean [1,2]. The atmosphere is represented by a low-order atmospheric "general circulation" model introduced by Lorenz in 1984 [3] and the ocean model considered here is a 3-box model which simulates the North Atlantic thermohaline circulation [2]. [1] Broecker W.S. (1997) Thermohaline circulation, the Achilles Heel of our climate system: will man-made CO_2 upset the current balance?. Science, 278, 1582-1588. [2] Roebber, P.J. (1995) Climate variability in a low-order coupled atmosphere-ocean model. Tellus, 47A, 473-494. [3] Lorenz, E.N. (1984) Irregularity. A fundamental property of the atmosphere. Tellus, 36A, 98-110.

  9. Sensitivity of ocean model simulation in the coastal ocean to the resolution of the meteorological forcing

    NASA Astrophysics Data System (ADS)

    Chen, Feng; Shapiro, Georgy; Thain, Richard

    2013-04-01

    The quality of ocean simulations depends on a number of factors such as approximations in governing equations, errors introduced by the numerical scheme, uncertainties in input parameters, and atmospheric forcing. The identification of relations between the uncertainties in input and output data is still a challenge for the development of numerical models. The impacts of ocean variables on ocean models are still not well known (e.g., Kara et al., 2009). Given the considerable importance of the atmospheric forcing to the air-sea interaction, it is essential that researchers in ocean modelling work need a good understanding about how sensitive the atmospheric forcing is to variations of model results, which is beneficial to the development of ocean models. Also, it provides a proper way to choose the atmospheric forcing in ocean modelling applications. Our previous study (Shapiro et al, 2011) has shown that the basin-wide circulation pattern and the temperature structure in the Black Sea produced by the same model is significantly dependent on the source of the meteorological input, giving remarkably different responses. For the purpose of this study we have chosen the Celtic Sea where high resolution meteo data are available from the UK Met office since 2006. The Celtic Sea is tidally dominated water basin, with the tidal stream amplitude varying from 0.25m/s in the southwest to 2 m/s in the Bristol Channel. It is also filled with mesoscale eddies which contribute to the formation of the residual (tidally averaged) circulation pattern (Young et al, 2003). The sea is strongly stratified from April to November, which adds to the formation of density driven currents. In this paper we analyse how sensitive the model output is to variations in the spatial resolution of meteorological using low (1.6°) and high (0.11°) resolution meteo forcing, giving the quantitative relation between variations of met forcing and the resulted differences of model results, as well as

  10. An Arctic Ice/Ocean Coupled Model with Wave Interactions

    DTIC Science & Technology

    2015-09-30

    contemporary Arctic climate models. OBJECTIVES To make progress with our long-term goals, over the lifetime of the project we will – further our...performance of climate models in predicting the rate of disappearance of Arctic sea ice (Jeffries et al., 2013), are fuelling considerable interest in the...coupled climate models will also benefit, for although direct ocean wave effects are unlikely to be subsumed in global scale simulations because of

  11. Task Models in the Digital Ocean

    ERIC Educational Resources Information Center

    DiCerbo, Kristen E.

    2014-01-01

    The Task Model is a description of each task in a workflow. It defines attributes associated with that task. The creation of task models becomes increasingly important as the assessment tasks become more complex. Explicitly delineating the impact of task variables on the ability to collect evidence and make inferences demands thoughtfulness from…

  12. Spurious dianeutral mixing in a global ocean model using spherical centroidal voronoi tessellations

    NASA Astrophysics Data System (ADS)

    Zhao, Shimei; Liu, Yudi

    2016-12-01

    In order to quantitatively evaluate the spurious dianeutral mixing in a global ocean model MPAS-Ocean (Model for Prediction Across Scales) using a spherical centroidal voronoi tessellations developed jointly by the National Center for Atmospheric Research and the Los Alamos National Laboratory in the United States, we choose z* vertical coordinate system in MPAS-Ocean, in which all physical mixing processes, such as convection adjustment and explicit diffusion parameter schemes, are omitted, using a linear equation of state. By calculating the Reference Potential Energy (RPE), front revolution position, time rate of RPE change, probability density function distribution and dimensionless parameter χ, from the perspectives of resolution, viscosity, Horizontal Grid Reynolds Number (HGRN), ReΔ, and momentum transmission scheme, using two ideal cases, overflow and baroclinic eddy channel, we qualitatively analyze the simulation results by comparison with the three non-isopycnal models in Ilicak et al. (2012), i.e., MITGCM, MOM, and ROMS. The results show that the spurious dianeutral mixing in the MPAS-Ocean increases over time. The spurious dianeutral transport is proportional to the HGRN directly and is reduced by increasing the lateral viscosity or using a finer resolution to control HGRN. When the HGRN is less than 10, spurious transport is reduced significantly. When using the proper viscosity closure, MPAS-Ocean performs better than MITGCM and MOM, closely to ROMS, in the 2D case without rotation, and much better than the above-mentioned three ocean models under the condition of 3D space with rotation due to the cell area difference between the hexagon cell and the quadrilateral cell with the same resolution. Both the Zalesak (1979) flux corrected transport scheme and Leith closure in MPAS-Ocean play an excellent role in reducing spurious dianeutral mixing. The performance of Leith scheme is preferable to the condition of three-dimensional baroclinic eddy.

  13. Can simple models predict large-scale surface ocean isoprene concentrations?

    NASA Astrophysics Data System (ADS)

    Booge, Dennis; Marandino, Christa A.; Schlundt, Cathleen; Palmer, Paul I.; Schlundt, Michael; Atlas, Elliot L.; Bracher, Astrid; Saltzman, Eric S.; Wallace, Douglas W. R.

    2016-09-01

    We use isoprene and related field measurements from three different ocean data sets together with remotely sensed satellite data to model global marine isoprene emissions. We show that using monthly mean satellite-derived chl a concentrations to parameterize isoprene with a constant chl a normalized isoprene production rate underpredicts the measured oceanic isoprene concentration by a mean factor of 19 ± 12. Improving the model by using phytoplankton functional type dependent production values and by decreasing the bacterial degradation rate of isoprene in the water column results in only a slight underestimation (factor 1.7 ± 1.2). We calculate global isoprene emissions of 0.21 Tg C for 2014 using this improved model, which is twice the value calculated using the original model. Nonetheless, the sea-to-air fluxes have to be at least 1 order of magnitude higher to account for measured atmospheric isoprene mixing ratios. These findings suggest that there is at least one missing oceanic source of isoprene and, possibly, other unknown factors in the ocean or atmosphere influencing the atmospheric values. The discrepancy between calculated fluxes and atmospheric observations must be reconciled in order to fully understand the importance of marine-derived isoprene as a precursor to remote marine boundary layer particle formation.

  14. Ice-Ocean Interaction at Seasonal to Decadal Scales in the Regional Arctic System Model

    NASA Astrophysics Data System (ADS)

    Maslowski, W.; Osinski, R.; Clement Kinney, J. L.; Craig, A.; Roberts, A.

    2013-12-01

    Understanding of critical processes and feedbacks operating in the Arctic Climate System becomes increasingly critical as the perennial and total summer sea ice cover continues its accelerated decline since the late 1990s. At the same time, realistic representation of such processes in Earth System models (ESMs) is fundamental to increase their skill in simulating the past and predicting future climate change in the Arctic. With respect to sea ice, its drift, export, deformation, and thermodynamic response to atmospheric and oceanic forcing needs further investigation. In order to understand oceanic effects on the Arctic ice pack and climate, an advanced knowledge of the regional circulation patterns, spatial and temporal variability, mesoscale processes, freshwater and heat budgets in the Arctic Ocean and their fluxes to/from Atlantic/Pacific is required. To address some of the requirements for understanding arctic processes and interactions we examine new results from the Regional Arctic System Model (RASM), which is a fully coupled regional climate model developed following the framework of the Community Earth System Model (CESM). At present, RASM consists of the Parallel Ocean Program (POP), Community Ice Model (CICE), Variable Infiltration Capacity (VIC) land hydrology model and the Weather Research and Forecasting (WRF) model coupled through the flux coupler (CPL7). The horizontal resolution currently used in POP and CICE components is 1/12-degree (or ~9 km) whereas in WRF and VIC it is 50 km. Presented results are from a RASM compset, where the atmospheric and land hydrology components are replaced with the 1948-2009 reanalysis data from Version 2 of the Coordinated Ocean-ice Reference Experiment (CORE-II) dataset. In particular, we focus on the upper Arctic Ocean heat and freshwater content, their variability and potential impact on the sea ice thickness and area. Crucial processes to be realistically represented in future ESMs are also discussed.

  15. Approximate Stokes Drift Profiles and their use in Ocean Modelling

    NASA Astrophysics Data System (ADS)

    Breivik, Oyvind; Bidlot, Jea-Raymond; Janssen, Peter A. E. M.; Mogensen, Kristian

    2016-04-01

    Deep-water approximations to the Stokes drift velocity profile are explored as alternatives to the monochromatic profile. The alternative profiles investigated rely on the same two quantities required for the monochromatic profile, viz the Stokes transport and the surface Stokes drift velocity. Comparisons against parametric spectra and profiles under wave spectra from the ERA-Interim reanalysis and buoy observations reveal much better agreement than the monochromatic profile even for complex sea states. That the profiles give a closer match and a more correct shear has implications for ocean circulation models since the Coriolis-Stokes force depends on the magnitude and direction of the Stokes drift profile and Langmuir turbulence parameterizations depend sensitively on the shear of the profile. Of the two Stokes drift profiles explored here, the profile based on the Phillips spectrum is by far the best. In particular, the shear near the surface is almost identical to that influenced by the f-5 tail of spectral wave models. The NEMO general circulation ocean model was recently extended to incorporate the Stokes-Coriolis force along with two other wave-related effects. The ECWMF coupled atmosphere-wave-ocean ensemble forecast system now includes these wave effects in the ocean model component (NEMO).

  16. Toward an Internal Gravity Wave Spectrum in Global Ocean Models

    DTIC Science & Technology

    2015-05-14

    14 MAY 2015 2. REPORT TYPE 3. DATES COVERED 00-00-2015 to 00-00-2015 4. TITLE AND SUBTITLE Toward an Internal Gravity Wave Spectrum in Global...resolution global ocean models forced by atmospheric fields and tides are beginning to display realistic internal gravity wave spectra, especially as

  17. Stochastic modelling and predictability: analysis of a low-order coupled ocean–atmosphere model

    PubMed Central

    Vannitsem, Stéphane

    2014-01-01

    There is a growing interest in developing stochastic schemes for the description of processes that are poorly represented in atmospheric and climate models, in order to increase their variability and reduce the impact of model errors. The use of such noise could however have adverse effects by modifying in undesired ways a certain number of moments of their probability distributions. In this work, the impact of developing a stochastic scheme (based on stochastic averaging) for the ocean is explored in the context of a low-order coupled (deterministic) ocean–atmosphere system. After briefly analysing its variability, its ability in predicting the oceanic flow generated by the coupled system is investigated. Different phases in the error dynamics are found: for short lead times, an initial overdispersion of the ensemble forecast is present while the ensemble mean follows a dynamics reminiscent of the combined amplification of initial condition and model errors for deterministic systems; for longer lead times, a reliable diffusive ensemble spread is observed. These different phases are also found for ensemble-oriented skill measures like the Brier score and the rank histogram. The implications of these features on building stochastic models are then briefly discussed. PMID:24842037

  18. Multi-Scale Coupling in Ocean and Climate Modeling

    SciTech Connect

    Zhengyu Liu, Leslie Smith

    2009-08-14

    We have made significant progress on several projects aimed at understanding multi-scale dynamics in geophysical flows. Large-scale flows in the atmosphere and ocean are influenced by stable density stratification and rotation. The presence of stratification and rotation has important consequences through (i) the conservation of potential vorticity q = {omega} {center_dot} {del} {rho}, where {omega} is the total vorticity and {rho} is the density, and (ii) the existence of waves that affect the redistribution of energy from a given disturbance to the flow. Our research is centered on quantifying the effects of potential vorticity conservation and of wave interactions for the coupling of disparate time and space scales in the oceans and the atmosphere. Ultimately we expect the work to help improve predictive capabilities of atmosphere, ocean and climate modelers. The main findings of our research projects are described.

  19. The salinity effect in a mixed layer ocean model

    NASA Technical Reports Server (NTRS)

    Miller, J. R.

    1976-01-01

    A model of the thermally mixed layer in the upper ocean as developed by Kraus and Turner and extended by Denman is further extended to investigate the effects of salinity. In the tropical and subtropical Atlantic Ocean rapid increases in salinity occur at the bottom of a uniformly mixed surface layer. The most significant effects produced by the inclusion of salinity are the reduction of the deepening rate and the corresponding change in the heating characteristics of the mixed layer. If the net surface heating is positive, but small, salinity effects must be included to determine whether the mixed layer temperature will increase or decrease. Precipitation over tropical oceans leads to the development of a shallow stable layer accompanied by a decrease in the temperature and salinity at the sea surface.

  20. Observations and models of inertial waves in the deep ocean

    NASA Technical Reports Server (NTRS)

    Fu, L.-L.

    1981-01-01

    A study of the structure of the inertial peak in deep ocean kinetic energy is presented, based on records taken from Polymode arrays deployed in the western North Atlantic Ocean. Results are interpreted in terms of both local sources and turning point effects on internal waves generated at lower latitudes, and it is found that three classes of environment and their corresponding spectra emerge from peak height variations: (1) the 1500-m level near the Mid-Atlantic Ridge, with the greatest peak height of 18 dB; (2) the upper and deep ocean over rough topography and the deep ocean underneath the Gulf Stream, with the intermediate peak height of 11.5 dB; and (3) the deep ocean over smooth topography, with the lowest peak height of 7.5 dB. Using the globally valid wave functions obtained by Munk and Phillips (1968), frequency spectra near f are calculated numerically. The model is latitudinally dependent, with the frequency shift and bandwidth of the inertial peak decreasing with latitude.

  1. Modeling the Effects of Anisotropic Turbulence and Dispersive Waves on Oceanic Circulation and their Incorporation in Navy Ocean Models

    DTIC Science & Technology

    2011-09-30

    anisotropic turbulence and dispersive waves in different environments , test them, compare them with data and implement them in ocean models. In this project...stratification and/or a solid body rotation. We have also performed computer simulations with an idealized circulation model of quasi-two-dimensional...member of a team on Martian planetary boundary layer at the International Space Science Institute and was responsible for reviewing turbulence models

  2. GRACE gravity model: assssment in terms of deep ocean currents from hydrography and from the ECCO ocean model

    NASA Technical Reports Server (NTRS)

    Zlotnicki, V.; Stammer, D.; Fukumori, I.

    2003-01-01

    Here we assess the new generation of gravity models, derived from GRACE data. The differences between a global geoid model (one from GRACE data and one the well-known EGM-96), minus a Mean Sea Surface derived from over a decade of altimetric data are compared to hydrographic data from the Levitus compilation and to the ECCO numerical ocean model, which assimilates altimetry and other data.

  3. LOSCAR: Long-term Ocean-atmosphere-Sediment CArbon cycle Reservoir Model

    NASA Astrophysics Data System (ADS)

    Zeebe, R. E.

    2011-06-01

    The LOSCAR model is designed to efficiently compute the partitioning of carbon between ocean, atmosphere, and sediments on time scales ranging from centuries to millions of years. While a variety of computationally inexpensive carbon cycle models are already available, many are missing a critical sediment component, which is indispensable for long-term integrations. One of LOSCAR's strengths is the coupling of ocean-atmosphere routines to a computationally efficient sediment module. This allows, for instance, adequate computation of CaCO3 dissolution, calcite compensation, and long-term carbon cycle fluxes, including weathering of carbonate and silicate rocks. The ocean component includes various biogeochemical tracers such as total carbon, alkalinity, phosphate, oxygen, and stable carbon isotopes. We have previously published applications of the model tackling future projections of ocean chemistry and weathering, pCO2 sensitivity to carbon cycle perturbations throughout the Cenozoic, and carbon/calcium cycling during the Paleocene-Eocene Thermal Maximum. The focus of the present contribution is the detailed description of the model including numerical architecture, processes and parameterizations, tuning, and examples of input and output. Typical CPU integration times of LOSCAR are of order seconds for several thousand model years on current standard desktop machines. The LOSCAR source code in C can be obtained from the author by sending a request to loscar.model@gmail.com.

  4. A parallel coupled oceanic-atmospheric general circulation model

    SciTech Connect

    Wehner, M.F.; Bourgeois, A.J.; Eltgroth, P.G.; Duffy, P.B.; Dannevik, W.P.

    1994-12-01

    The Climate Systems Modeling group at LLNL has developed a portable coupled oceanic-atmospheric general circulation model suitable for use on a variety of massively parallel (MPP) computers of the multiple instruction, multiple data (MIMD) class. The model is composed of parallel versions of the UCLA atmospheric general circulation model, the GFDL modular ocean model (MOM) and a dynamic sea ice model based on the Hiber formulation extracted from the OPYC ocean model. The strategy to achieve parallelism is twofold. One level of parallelism is accomplished by applying two dimensional domain decomposition techniques to each of the three constituent submodels. A second level of parallelism is attained by a concurrent execution of AGCM and OGCM/sea ice components on separate sets of processors. For this functional decomposition scheme, a flux coupling module has been written to calculate the heat, moisture and momentum fluxes independent of either the AGCM or the OGCM modules. The flux coupler`s other roles are to facilitate the transfer of data between subsystem components and processors via message passing techniques and to interpolate and aggregate between the possibly incommensurate meshes.

  5. A simple metabolic model of glacial-interglacial energy supply to the upper ocean

    NASA Astrophysics Data System (ADS)

    Pelegrí, J. L.; Olivella, R.; García-Olivares, A.

    2011-03-01

    We use a simple two-state two-box ocean to simulate the CO2 signal during the last four glacial-interglacial transitions in the earth system. The model is inspired by the similarity in spatial organization and temporal transition patterns between the earth and other complex systems, such as mammals. The comparison identifies the earth's metabolic rate with net autotrophic primary production in the upper ocean, sustained through new inorganic carbon and nutrients advected from the deep ocean and organic matter remineralized within the upper ocean. We view the glacial-interglacial transition as a switch of the upper ocean from a basal to an enhanced metabolic state, with energy supply initially relying on the remineralization of the local organic sources and the eventual steady state resulting from the increased advective supply of inorganic deep sources. During the interglacial-glacial transition the opposite occurs, with an initial excess of advective supply and primary production that allows the replenishment of the upper-ocean organic storages. We set the relative change in energy supply from the CO2 signal and use genetic algorithms to explore the sensitivity of the model output to both the basal recirculation rate and the intensity-timing of the maximum recirculation rate. The model is capable of reproducing quite well the long-term oscillations, as shown by correlations with observations typically about 0.8. The dominant time scale for each cycle ranges between about 40 and 45 kyr, close to the 41 kyr average obliquity astronomical period, and the deep-ocean recirculation rate increases between one and two orders of magnitude from glacial to interglacial periods.

  6. Modeling of SAR signatures of shallow water ocean topography

    NASA Technical Reports Server (NTRS)

    Shuchman, R. A.; Kozma, A.; Kasischke, E. S.; Lyzenga, D. R.

    1984-01-01

    A hydrodynamic/electromagnetic model was developed to explain and quantify the relationship between the SEASAT synthetic aperture radar (SAR) observed signatures and the bottom topography of the ocean in the English Channel region of the North Sea. The model uses environmental data and radar system parameters as inputs and predicts SAR-observed backscatter changes over topographic changes in the ocean floor. The model results compare favorably with the actual SEASAT SAR observed backscatter values. The developed model is valid for only relatively shallow water areas (i.e., less than 50 meters in depth) and suggests that for bottom features to be visible on SAR imagery, a moderate to high velocity current and a moderate wind must be present.

  7. Model-based inversion for a shallow ocean application

    SciTech Connect

    Candy, J.V.; Sullivan, E.J.

    1994-03-01

    A model-based approach to invert or estimate the sound speed profile (SSP) from noisy pressure-field measurements is discussed. The resulting model-based processor (MBP) is based on the state-space representation of the normal-mode propagation model. Using data obtained from the well-known Hudson Canyon experiment, a noisy shallow water ocean environment, the processor is designed and the results compared to those predicted using various propagation models and data. It is shown that the MBP not only predicts the sound speed quite well, but also is able to simultaneously provide enhanced estimates of both modal and pressure-field measurements which are useful for localization and rapid ocean environmental characterization.

  8. Ocean Simulation Model for Internal Waves

    DTIC Science & Technology

    1990-08-01

    MODEL1.DAT U D 4°NZ Real U,V,W, (U(i),V(i),W(i), Z Z(i), i= 1 ,NZ) MODEL1.AUX U S 3°NZ Real NT,NX,NZ,DT, NTNX,NZDT, DXDZ,T0, LAT , DX,DZ,T0, LAT , LON,AZ LON...Oceanographic and Atmospheric Research Laboratory, Stennis Space Center, Mississippi 39529-5004. 9 1 .... .... . .. ...8 I I I II I I Foreword The effects of the...I A. Background 1 B. Project Objectives 1 C. Purpose of This Manual 1 II. Background and Derivation of Algorithms 2 A. Stochastic Representation of

  9. An ice-ocean coupled model for the Northern Hemisphere

    NASA Technical Reports Server (NTRS)

    Cheng, Abe; Preller, Ruth

    1992-01-01

    The Hibler ice model has been modified and adapted to a domain that includes most of the sea ice-covered areas in the Northern Hemisphere. This model, joined with the Cox ocean model, is developed as an enhancement to the U.S. Navy's sea ice forecasting, PIPS, and is termed PIPS2.0. Generally, the modeled ice edge is consistent with the Navy-NOAA Joint Ice Center weekly analysis, and the modeled ice thickness distribution agrees with submarine sonar data in the central Arctic basin.

  10. Real-Time Ocean Modeling Systems

    DTIC Science & Technology

    2013-10-22

    2002 2. REPORT TYPE 3. DATES COVERED (From - To) Journal Article 4 . TITLE AND SUBTITLE Real-time 16iebaf Modeling Systems \\&&»A 5a...Director NCST E.O. Hartwig, 7000 Public Affairs (Unclassified/ Unlimited Only), Code 7n30 4 Division, Code Author, Code HQ-NRL 5511/6 (Rev. 12-93...according to the routing in Section 4 . 1. NRL Reports Submit the diskette (if available), manuscript, typed double-spaced, complete with tables

  11. Theory and Practice of Data Assimilation in Ocean Modeling

    DTIC Science & Technology

    2007-09-30

    the development, implementation and evaluation of practical data assimilation methods for regional to basin scale ocean models. Since the data... assimilation methods that give the most and best information are highly resource intensive, and often not practical for use with detailed models, we are...particularly interested in the price paid in terms of accuracy and confidence for using economical but suboptimal data assimilation methods . Explicit

  12. Theory and Practice of Data Assimilation in Ocean Modeling

    DTIC Science & Technology

    2002-09-30

    development, implementation and validation of practical data assimilation methods for synoptic ocean models. By "data assimilation" we mean the... assimilation methods which give the most and best information are highly resource intensive, and often not practical for use with detailed models, we are...particularly interested in the price paid in terms of accuracy and confidence for using economical but suboptimal data assimilation methods . Direct

  13. An ocean scatter propagation model for aeronautical satellite communication applications

    NASA Technical Reports Server (NTRS)

    Moreland, K. W.

    1990-01-01

    In this paper an ocean scattering propagation model, developed for aircraft-to-satellite (aeronautical) applications, is described. The purpose of the propagation model is to characterize the behavior of sea reflected multipath as a function of physical propagation path parameters. An accurate validation against the theoretical far field solution for a perfectly conducting sinusoidal surface is provided. Simulation results for typical L band aeronautical applications with low complexity antennas are presented.

  14. Modelling of the Circulation of the Western Indian Ocean

    DTIC Science & Technology

    1988-01-01

    MODELLING OF THE CIRCULATION OF THE WESTERN INDIAN OCEAN Contract N00014-85-K-0019 Julian P. McCreary Pijush K. Kundu Nova University Oceanographic...described below. (i) Cooling of the Arabian Sea: McCreary and Kundu (1989) have just completed a modeling study of the variability in the Arabian Sea...entirely responsible for the observed annual heat gained by the Arabian Sea. (ii) The Gulf of Tehuantepec: McCreary , Lee and Enfield (1989) have

  15. Model Order Reduction of Aeroservoelastic Model of Flexible Aircraft

    NASA Technical Reports Server (NTRS)

    Wang, Yi; Song, Hongjun; Pant, Kapil; Brenner, Martin J.; Suh, Peter

    2016-01-01

    This paper presents a holistic model order reduction (MOR) methodology and framework that integrates key technological elements of sequential model reduction, consistent model representation, and model interpolation for constructing high-quality linear parameter-varying (LPV) aeroservoelastic (ASE) reduced order models (ROMs) of flexible aircraft. The sequential MOR encapsulates a suite of reduction techniques, such as truncation and residualization, modal reduction, and balanced realization and truncation to achieve optimal ROMs at grid points across the flight envelope. The consistence in state representation among local ROMs is obtained by the novel method of common subspace reprojection. Model interpolation is then exploited to stitch ROMs at grid points to build a global LPV ASE ROM feasible to arbitrary flight condition. The MOR method is applied to the X-56A MUTT vehicle with flexible wing being tested at NASA/AFRC for flutter suppression and gust load alleviation. Our studies demonstrated that relative to the fullorder model, our X-56A ROM can accurately and reliably capture vehicles dynamics at various flight conditions in the target frequency regime while the number of states in ROM can be reduced by 10X (from 180 to 19), and hence, holds great promise for robust ASE controller synthesis and novel vehicle design.

  16. Decadal-Scale Response of the Antarctic Ice sheet to a Warming Ocean using the POPSICLES Coupled Ice Sheet-Ocean model

    NASA Astrophysics Data System (ADS)

    Martin, Daniel; Asay-Davis, Xylar; Cornford, Stephen; Price, Stephen; Ng, Esmond; Collins, William

    2016-04-01

    We present POPSICLES simulation results covering the full Antarctic Ice Sheet and the Southern Ocean spanning the period from 1990 to 2010. We use the CORE v. 2 interannual forcing data to force the ocean model. Simulations are performed at 0.1 degree (~5 km) ocean resolution with adaptive ice sheet resolution as fine as 500 m to adequately resolve the grounding line dynamics. We discuss the effect of improved ocean mixing and subshelf bathymetry (vs. the standard Bedmap2 bathymetry) on the behavior of the coupled system, comparing time-averaged melt rates below a number of major ice shelves with those reported in the literature. We also present seasonal variability and decadal melting trends from several Antarctic regions, along with the response of the ice shelves and the consequent dynamic response of the grounded ice sheet. POPSICLES couples the POP2x ocean model, a modified version of the Parallel Ocean Program, and the BISICLES ice-sheet model. POP2x includes sub-ice-shelf circulation using partial top cells and the commonly used three-equation boundary layer physics. Standalone POP2x output compares well with standard ice-ocean test cases (e.g., ISOMIP) and other continental-scale simulations and melt-rate observations. BISICLES makes use of adaptive mesh refinement and a 1st-order accurate momentum balance similar to the L1L2 model of Schoof and Hindmarsh to accurately model regions of dynamic complexity, such as ice streams, outlet glaciers, and grounding lines. Results of BISICLES simulations have compared favorably to comparable simulations with a Stokes momentum balance in both idealized tests (MISMIP-3d) and realistic configurations.

  17. Geochemical constraints on ocean general circulation models. Final report, May 1, 1995--April 30, 1997

    SciTech Connect

    Broecker, W.S.

    1998-05-17

    A better understanding of the manner in which the ocean operates is essential to the preparation for the consequences of the generation of CO{sub 2} by fossil fuel burning. Examples are as follows: (1) the ocean will ultimately take up a major fraction of the CO{sub 2} produced, but this uptake is retarded by the slow mixing rates, in order to predict the uptake, researchers must develop and validate general circulation models for the ocean; (2) during glacial time large global climate changes occurred. The changes were abrupt happening in a few decades. The trigger for these changes appears to have been reorganizations of the large-scale thermohaline circulation of the ocean. Models suggest that if the CO{sub 2} content of the atmosphere rises to more than 700 ppm, then a possibility exists that another such reorganization might occur. Hence, researchers must learn more about the factors influencing deep-water formation both in the northern Atlantic and in the Souther Ocean. The thrust of this research was to develop constraints based on the distributions of chemicals and tracers in the sea. The accomplishments are outlined in this report.

  18. High resolution modeling of direct ocean carbon sequestration

    SciTech Connect

    Michael Follows; John Marshall

    2004-04-22

    This work has followed two themes: (1) Developing and using the adjoint of the MIT ocean biogeochemistry model to examine the efficiency of carbon sequestration in a global configuration. We have demonstrated the power of the adjoint method for systematic ocean model sensitivity studies. We have shown that the relative efficiency of carbon sequestration in the Atlantic and Pacific basins changes with the period of interest. For decadal to centennial scales, the Pacific is more efficient. On longer timescales the Atlantic is more efficient . (2) We have developed and applied a high-resolution, North Atlantic circulation and tracer model to investigate the role of the mesoscale in controlling sequestration efficiency. We show that the mesoscale eddy field, and its explicit representation, significantly affects the estimated sequestration efficiency for local sources on the Eastern US seaboard.

  19. The biological carbon pump in the ocean: Reviewing model representations and its feedbacks on climate perturbations.

    NASA Astrophysics Data System (ADS)

    Hülse, Dominik; Arndt, Sandra; Ridgwell, Andy; Wilson, Jamie

    2016-04-01

    The ocean-sediment system, as the biggest carbon reservoir in the Earth's carbon cycle, plays a crucial role in regulating atmospheric carbon dioxide concentrations and climate. Therefore, it is essential to constrain the importance of marine carbon cycle feedbacks on global warming and ocean acidification. Arguably, the most important single component of the ocean's carbon cycle is the so-called "biological carbon pump". It transports carbon that is fixed in the light-flooded surface layer of the ocean to the deep ocean and the surface sediment, where it is degraded/dissolved or finally buried in the deep sediments. Over the past decade, progress has been made in understanding different factors that control the efficiency of the biological carbon pump and their feedbacks on the global carbon cycle and climate (i.e. ballasting = ocean acidification feedback; temperature dependant organic matter degradation = global warming feedback; organic matter sulphurisation = anoxia/euxinia feedback). Nevertheless, many uncertainties concerning the interplay of these processes and/or their relative significance remain. In addition, current Earth System Models tend to employ empirical and static parameterisations of the biological pump. As these parametric representations are derived from a limited set of present-day observations, their ability to represent carbon cycle feedbacks under changing climate conditions is limited. The aim of my research is to combine past carbon cycling information with a spatially resolved global biogeochemical model to constrain the functioning of the biological pump and to base its mathematical representation on a more mechanistic approach. Here, I will discuss important aspects that control the efficiency of the ocean's biological carbon pump, review how these processes of first order importance are mathematically represented in existing Earth system Models of Intermediate Complexity (EMIC) and distinguish different approaches to approximate

  20. Oxygen gradients across the Pacific Ocean: Resolving an apparent discrepancy between atmospheric and ocean observations and models

    NASA Astrophysics Data System (ADS)

    Mikaloff Fletcher, S. E.; Steinkamp, K.; Stephens, B. B.; Tohjima, Y.; Gruber, N.

    2015-12-01

    We use oceanic and atmospheric model simulations to investigate and resolve a disagreement between observations of atmospheric O2/N2 and CO2 data and air-sea fluxes estimated from an ocean inversion. Atmospheric observations of O2/N2 and CO2 can be combined to calculate atmospheric potential oxygen (APO=O2/N2+1.1CO2), a powerful atmospheric tracer for ocean biogeochemical processes that is not influenced by terrestrial photosynthesis or respiration. A recent study identified a deep APO minimum in the Northwest Pacific from measurements collected on a repeat transect between New Zealand and Japan. This minimum could not be reproduced in atmospheric model simulations forced with air-sea fluxes estimated from ocean data, suggesting that oxygen uptake in the Northwest Pacific must be under-estimated by a factor of two. We use an updated ocean inverse method to estimate new air-sea fluxes from the ocean interior measurements at a higher spatial resolution than previous work using a suite of ten ocean general circulation models (OGCMs). These new air-sea flux estimates are able to match the atmospheric APO data when used as boundary conditions for an atmospheric transport model. The relative roles of thermal and biological processses in contributing to oxygen absorption by the North Pacific and other ocean regions is investigated.

  1. Coupled Modeling of Hydrodynamics and Sound in Coastal Ocean for Renewable Ocean Energy Development

    SciTech Connect

    Long, Wen; Jung, Ki Won; Yang, Zhaoqing; Copping, Andrea; Deng, Z. Daniel

    2016-03-01

    An underwater sound model was developed to simulate sound propagation from marine and hydrokinetic energy (MHK) devices or offshore wind (OSW) energy platforms. Finite difference methods were developed to solve the 3D Helmholtz equation for sound propagation in the coastal environment. A 3D sparse matrix solver with complex coefficients was formed for solving the resulting acoustic pressure field. The Complex Shifted Laplacian Preconditioner (CSLP) method was applied to solve the matrix system iteratively with MPI parallelization using a high performance cluster. The sound model was then coupled with the Finite Volume Community Ocean Model (FVCOM) for simulating sound propagation generated by human activities, such as construction of OSW turbines or tidal stream turbine operations, in a range-dependent setting. As a proof of concept, initial validation of the solver is presented for two coastal wedge problems. This sound model can be useful for evaluating impacts on marine mammals due to deployment of MHK devices and OSW energy platforms.

  2. Validation of a global finite element sea-ice ocean model

    NASA Astrophysics Data System (ADS)

    Timmermann, R.; Danilov, S.; Schröter, J.

    2009-04-01

    Results from a global Finite Element Sea ice-Ocean Model (FESOM) are evaluated using a wide range of observational datasets. FESOM's ocean component is a primitive-equation, hydrostatic ocean model using isopycnic diffusion and a Gent-McWilliams scheme to parameterize the effects of sub-gridscale turbulence on tracer distribution. Vertical mixing and convection are parameterized as a function of the Richardson number and the Monin-Obukhov length. A finite element dynamic-thermodynamic sea ice-model with elastic-viscous-plastic rheology has been developed and coupled to the ocean component. The model features a prognostic snow layer but neglects internal heat storage. All model components are discretized on a triangular/tetrahedral grid with a continuous, conforming representation of model variables. The coupled model has been run in a global configuration and forced with NCEP daily atmospheric reanalysis data for 1948-2007. Results are analysed with a focus on the Southern Hemisphere. While summer ice extent is underestimated in both hemispheres, winter ice extents are in good agreement with satellite data. Southern Ocean sea ice thickness distribution agrees well with ship-based observations and even quantitatively with data from upwards looking sonars (ULS). Sea ice freezing rates have been validated using repeated salinity profiles from Southern Elephant Seals. Gulf Stream transport is underestimated, but transports of the Kuroshio and the Antarctic Circumpolar Current appear realistic. A comparison of numerical tracer studies to observed CFC distribution indicates that bottom layer ventilation occurs on realistic pathways. Global meridional overturning features a strong Antarctic Bottom Water (AABW) cell, while the formation of North Atlantic Deep Water (NADW) appears to be on the weak side. Besides pure model validation, the study also identifies regions and processes that critically require a locally increased horizontal resolution in order to be represented

  3. Documentation, critique, and suggested changes in a simple ocean model

    SciTech Connect

    Taylor, K.E.

    1986-10-01

    A simple upwelling-diffusion model originally formulated by the NYU modeling group and described in Hoffert et al. (1983) has been rederived and critically analyzed. The purpose was to evaluate how to best incorporate the model into a climate model such as the Livermore Statistical Dynamical Model (LSDM). Hoffert's model was one of the first models to be used to study the question of the transient response of the ocean to climate perturbations. It successfully reproduces the equilibrium temperature structure of the deep ocean. I have found that there are some problems in the formulation of the model when it is applied at individual latitudes. I have offered a simple alternative that allows the thermohaline circulation to vary in such a way as to keep the polar temperature just above the freezing point. I have also corrected some inconsistencies in the poleward heat transport equations. Analytic solutions of the model equations under simple harmonic forcing have been found and can be used to verify the finite-difference schemes of numerical models. Full analysis of a more complex model that includes upwelling driven by surface wind stress has not yet been completed.

  4. Assessing first-order emulator inference for physical parameters in nonlinear mechanistic models

    USGS Publications Warehouse

    Hooten, Mevin B.; Leeds, William B.; Fiechter, Jerome; Wikle, Christopher K.

    2011-01-01

    We present an approach for estimating physical parameters in nonlinear models that relies on an approximation to the mechanistic model itself for computational efficiency. The proposed methodology is validated and applied in two different modeling scenarios: (a) Simulation and (b) lower trophic level ocean ecosystem model. The approach we develop relies on the ability to predict right singular vectors (resulting from a decomposition of computer model experimental output) based on the computer model input and an experimental set of parameters. Critically, we model the right singular vectors in terms of the model parameters via a nonlinear statistical model. Specifically, we focus our attention on first-order models of these right singular vectors rather than the second-order (covariance) structure.

  5. Sensitivity of ocean model simulation in the coastal ocean to the resolution of the meteorological forcing

    NASA Astrophysics Data System (ADS)

    Shapiro, G. I.; Cheng, F.; Thain, R.

    2012-04-01

    The quality of the ocean model simulation depends on a number of factors e.g. approximations in the governing equations, errors introduced by the numerical scheme, and uncertainties in input parameters such as atmospheric forcing. Our previous study (Shapiro et al., 2011) has shown that the basin-wide circulation pattern and the temperature structure in the Black Sea produced by the same model is significantly dependent on the source of the meteorological input. The horizontal resolution was approximately the same, however, the wind and cloudiness patterns provided by the reanalysis data obtained from National Centers for Environmental Prediction (NCEP, USA) and Japanese 25 year Re-Analysis Project (JRA) were sometimes quite different, which resulted directly in different responses of the sea. For the purposes of this study we have chosen the Celtic Sea, where high resolution meteorological data are available from the UK Met office from 2006. The Celtic Sea is a tidally dominated water basin, with the tidal stream amplitude varying from 0.25 m/s in the southwest to 2 m/s in the Bristol Channel. It is also filled with mesoscale eddies which contribute to the formation of the residual (tidally averaged) circulation pattern (Young et al., 2004). The sea is strongly stratified from April to November, which adds to the formation of density driven currents. In this paper we analyse how sensitive the model output is to variations in the spatial resolution of meteorological parameters obtained from the same source, so that any difference in the ocean output is purely linked to variations in resolution. The original resolution of the meteorological parameters was 1/9 of a degree (about 12 km), which was subsampled to create resolutions up to 96 km. The effect of varying the resolution of the meteorological parameters is not obvious a priori. The length scales of most energetic dynamic features in both ocean and atmosphere are defined by the Rossby radius of deformation

  6. Model of Methane Hydrate Formation in Mid-ocean Ridges

    NASA Astrophysics Data System (ADS)

    Dmitrievsky, A. N.; Balanyuk, I. E.; Sorokhtin, O. G.; Matveenkov, V. V.; Dongaryan, L. Sh.

    2003-04-01

    MODEL OF METHANE HYDRATE FORMATION IN MID-OCEAN RIDGES A.N. Dmitrievsky, I.E. Balanyuk, O.G.Sorokhtin, V.V. Matveenkov, and L.Sh. Dongaryan P.P.Shirshov Institute of Oceanology Russian Academy of Sciences Moscow, Russia, balanyuk@sio.rssi.ru One among the most perspective direction in studying the ocean floor is the research of hydrothermal fields within the most active zones — rift valleys, where the processes of spreading of the ocean floor, uplift of the deep matter to the surface of the ocean floor, and creation of the new oceanic crust occur. Volcanic activity in these zones is accompanied with the formation of the hydrothermal system executing separation, transfer, and precipitation of a series of chemical elements. It is known that ore deposits with high concentration of iron, manganese, copper, nickel, cobalt are formed as a result of hydrothermal activity. It is much less known that hydrothermal activity in these zones has important but not so evident result — the formation of hydrocarbons in the form of methane hydrates. We propose the hypothesis of formation of methane hydrate deposits over the shallow slopes of the mid-oceanic ridges as an outcome of the action of two factors: the thermal convection of water in fractured-porous rocks of the crust and the reaction of serpentinization of the crust. The intensive exhalation of hydrocarbons takes place in the process of serpentinization. The conditions of water convection in the porous media are favorable for the formation and accumulation of methane hydrates in the near-surface layers of the oceanic crust. The carbonic-acid gas dissolved in the seawater is involved into the process of methane hydrate formation. It was established that the most favorable conditions for this mechanism are over the slopes of the Mid-Atlantic Ridge. All types of water areas where gas hydrates occur can be conditionally subdivided into following geodynamic zones: the abyssal basins of the inner and marginal seas, the

  7. Ocean modelling for aquaculture and fisheries in Irish waters

    NASA Astrophysics Data System (ADS)

    Dabrowski, T.; Lyons, K.; Cusack, C.; Casal, G.; Berry, A.; Nolan, G. D.

    2015-06-01

    The Marine Institute, Ireland, runs a suite of operational regional and coastal ocean models. Recent developments include several tailored products that focus on the key needs of the Irish aquaculture sector. In this article, an overview of the products and services derived from the models are presented. A shellfish model that includes growth and physiological interactions of mussels with the ecosystem and is fully embedded in the 3-D numerical modelling framework has been developed at the Marine Institute. This shellfish model has a microbial module designed to predict levels of coliform contamination in mussels. This model can also be used to estimate the carrying capacity of embayments, assess impacts of pollution on aquaculture grounds and help to classify shellfish waters. The physical coastal model of southwest Ireland provides a three day forecast of shelf water movement in the region. This is assimilated into a new harmful algal bloom alert system used to inform end-users of potential toxic shellfish events and high biomass blooms that include fish killing species. Further services include the use of models to identify potential sites for offshore aquaculture, to inform studies of potential cross-contamination in farms from the dispersal of planktonic sea lice larvae and other pathogens that can infect finfish and to provide modelled products that underpin the assessment and advisory services on the sustainable exploitation of the marine fisheries resources. This paper demonstrates that ocean models can provide an invaluable contribution to the sustainable blue growth of aquaculture and fisheries.

  8. Simulation of the tropical oceans with an ocean GCM coupled to an atmospheric mixed-layer model

    SciTech Connect

    Murtugudde, R.; Seager, R.; Busalacchi, A.

    1996-08-01

    A reduced gravity, primitive equation, ocean general circulation model (GCM) is coupled to an advective atmospheric mixed-layer (AML) model to demonstrate the importance of a nonlocal atmospheric mixed-layer parameterization for a proper simulation of surface heat fluxes and sea surface temperatures (SST). Seasonal variability of the model SSTs and the circulation are generally in good agreement with the observations in each of the tropical oceans. These results are compared to other simulations that use a local equilibrium mixed-layer model. Inclusion of the advective AML model is demonstrated to lead to a significant improvement in the SST simulation in all three oceans. Advection and diffusion of the air humidity play significant roles in determining SSTs even in the tropical Pacific where the local equilibrium assumption was previously deemed quite accurate. The main, and serious, model flaw is an inadequate representation of the seasonal cycle in the upwelling regions of the eastern Atlantic and Pacific Oceans. The results indicate that the feedback between mixed-layer depths and SSTs can amplify SST errors, implying that increased realism in the modeling of the ocean mixed layer increases the demand for realism in the representation of the surface heat fluxes. The performance of the GCM with a local-equilibrium mixed-layer model in the Atlantic is as poor as previous simple ocean model simulations of the Atlantic. The conclusion of earlier studies that the simple ocean model was at fault may, in fact, not be correct. Instead the local-equilibrium heat flux parameterization appears to have been the major source of error. Accurate SST predictions may, hence, be feasible by coupling the AML model to computationally efficient simple ocean models. 69 refs., 18 figs., 1 tab.

  9. Fifty years of numerical modeling of baroclinic ocean

    NASA Astrophysics Data System (ADS)

    Sarkisyan, A. S.

    2012-02-01

    This paper presents a brief critical analysis of the main historical stages of numerical modeling for the last fifty years. It was a half a century ago that the numerical simulation of an actual baroclinic ocean was initiated by the author and his students [1, 2]. In meteorology, studies on the numerical modeling of a baroclinic atmosphere existed much earlier [21, 22]. Despite this, a similar move in oceanography was met with strong resistance. At that time, there were many studies on the calculation of the total mass transport. The founders of this field, V.B. Shtokman, H. Sverdrup, and W. Munk, were mistaken in believing that they addressed baroclinic models of the ocean. The author preferred works by V. Ekman [12] and I. Sandström and B. Helland-Hansen [19]. A generalization of recent studies made it possible to come to some conclusions on the need to use the level of the free oceanic surface as a basis rather than the function of total mass transport, on the role of the baroclinic β effect (BARBE), on the joint effect of baroclinicity and bottom relief (JEBAR), etc. The author conditionally divides these fifty years into the following three stages. (1) The first stage was 1961-1969, when the author and his students performed almost exclusively diagnostic and adaptation calculations of climatic characteristics. (2) The second stage began with papers by K. Bryan [23] and his students. This is an important and promising stage involving mainly prognostic studies and four-dimensional analysis. The major advances in modeling at this stage (the Gulf Stream separation point [61], the Kuroshio seasonal evolution [63], the formation of the cold intermediate layer in the Black Sea [80], the subsurface countercurrent in the Caspian Sea [25], the realistic four-dimensional analysis of the Kara Sea [60], etc.) were due to high-resolution and/or data assimilation with an adequate period of integration. (3) The third stage began with the activities of international

  10. Assessment of uncertainties of ocean color parameters for the ocean Carbon-based Productivity Model

    NASA Astrophysics Data System (ADS)

    Sheng, M. A.; Xiaofeng, Yang; Zui, Tao; Ziwei, Li; Xuan, Zhou

    2014-03-01

    With the developments of ocean color remote sensing technology, some ocean color parameters can be derived by satellite globally. These terms, including chlorophyll concentration (Chl), particulate backscattering coefficients (bbp), photosynthetically available radiation (PAR), have been proved to be related to NPP of phytoplankton. Based on these parameters with other auxiliary data, a carbon-based productivity model (CbPM) had been developed. The model derives phytoplankton carbon(C) from bbp and utilizes the ratios of C and Chl to describe the phytoplankton growth rates (μ) which has physiological dependencies on light (through variations in PAR), nutrients, and temperature. This paper indicated how the uncertainties in satellite derived parameters (Chl, bbp and PAR) propagated through the CbPM using Monte Carlo method. Comparisons on the individual contributor to the random uncertainty in NPP between these input items were discussed. The analysis results showed that among the three parameters, the biggest contribution to the uncertainty in the model output came from Chl. Therefore, improvements in the accuracy of Chl would have the largest potential to improve the ability of CbPM in estimating NPP of phytoplankton.

  11. A new high resolution tidal model in the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Cancet, Mathilde; Andersen, Ole; Lyard, Florent; Cotton, David; Benveniste, Jérôme

    2016-04-01

    The Arctic Ocean is a challenging region for tidal modeling, because of its complex and not well-documented bathymetry, together combined with the intermittent presence of sea ice and the fact that the in situ tidal observations are scarce at such high latitudes. As a consequence, the accuracy of the global tidal models decreases by several centimeters in the Polar Regions. It has a large impact on the quality of the satellite altimeter sea surface heights in these regions (ERS1/2, Envisat, CryoSat-2, SARAL/AltiKa and the future Sentinel-3 mission), but also on the end-users' applications that need accurate tidal information. Better knowledge of the tides will improve the quality of the high latitudes altimeter sea surface heights and of all derived products, such as the altimetry-derived geostrophic currents, the mean sea surface and the mean dynamic topography. In addition, accurate tidal models are highly strategic information for ever-growing maritime and industrial activities in this region. NOVELTIS and DTU Space have recently developed a regional, high-resolution tidal atlas in the Arctic Ocean, in the framework of an extension of the CryoSat Plus for Oceans (CP4O) project funded by ESA (STSE program). In particular, this atlas benefits from the assimilation of the most complete satellite altimetry dataset ever used in this region, including the Envisat data up to 82°N and the CryoSat-2 reprocessed data between 82°N and 88°N. The combination of all these satellites gives the best possible coverage of altimetry-derived tidal constituents. Tide gauge data have also been used either for assimilation or validation. This paper presents the methodology followed to develop the model and the performances of this new regional tidal model in the Arctic Ocean.

  12. Coupled wave-ocean modeling system experiments in the Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Clementi, Emanuela; Oddo, Paolo; Korres, Gerasimos; Pinardi, Nadia; Drudi, Massimiliano; Tonani, Marina; Grandi, Alessandro; Adani, Mario

    2015-04-01

    Wind waves and oceanic circulation processes are of major interest in determining accurate sea state predictions and their interactions are very important for individual dynamic processes. This work presents a coupled wave-current numerical modelling system composed by the ocean circulation model NEMO (Nucleus for European Modelling of the Ocean) and the third generation wave model WaveWatchIII (WW3) implemented in the Mediterranean Sea with 1/16° horizontal resolution and forced by ECMWF atmospheric fields. In order to evaluate the performance of the coupled model, two sets of numerical experiments have been performed and described in this work. A first set of experiments has been built by coupling the wave and circulation models that hourly exchange the following fields: the sea surface currents and air-sea temperature difference are transferred from NEMO model to WW3 model modifying respectively the mean momentum transfer of waves and the wind speed stability parameter; while the neutral drag coefficient computed by WW3 model is passed to NEMO that computes the turbulent component. Five years (2009-2013) numerical experiments have been carried out in both uncoupled and coupled modes. In order to validate the modelling system, numerical results have been compared with coastal and drifting buoys and remote sensing data. Comparison results demonstrate that the WW3 model can fairly reproduce the observed wave characteristics and show that the wave-current interactions improve the representation of the wave spectrum. Minor improvements have been reached by comparing coupled and uncoupled circulation NEMO model results with observations. A second set of numerical experiments has been performed by considering NEMO model one-way coupled with WW3 model. The hydrodynamic model receives from the wave model the neutral drag coefficient and a set of wave fields used to calculate the wave-induced vertical mixing according to Qiao et al. (2010) formulation. Two experiments

  13. Role of south Indian Ocean swells in modulating the north Indian Ocean wave climate through modelling and remote sensing

    NASA Astrophysics Data System (ADS)

    Samiksha, S. V.; Vethamony, P.; Aboobacker, V. M.; Rashmi, R.

    2012-04-01

    Implementation and validation of a third generation wave model, Wavewatch III was used to study the characteristics of the south Indian ocean swells and their propagation in the north Indian Ocean. The NCEP reanalysis wind data (2.5° x 2.5°) has been used to generate the wind waves for the entire Indian Ocean during 2006 - 2007. The modelled wave parameters have been compared with measured buoy data and with merged altimeter data. The model results show good agreement with the buoy and altimeter data. A case study is carried out to study the propagation of the swells generated at the roaring 40°S in the Indian Ocean during May 2007. The "southern swell" occurred during May 2007 has been successfully reproduced in the wave model, which confirmed by the comparison of modelled significant wave heights with the merged altimeter significant wave heights. These swells were generated in the Atlantic ocean near the southern tip of South Africa and propagated towards the north Indian Ocean. These waves touches the Madagascar region and further hits the La Reunion islands after three days thus creating numerous damages near the islands. The magnitude of the swell is around 15m near the generation area and it reduces to around 6m near the La Reunion islands while propagating towards the north Indian Ocean. Further the swell energy is spataially distributed in the northern and southern Indian Ocean. The study reveals that the swells generated in the roaring forties and propagating in the SW/SSW direction influences more to Bay of Bengal than Arabian Sea. This occurs during pre-monsoon season primarily because large scale winds are weak in the north Indian Ocean during this period and hence swells from south Indian Ocean dominates at this time. The case of "southern swell" also happened to be at the same season. Further wave parameters were extracted at few locations in the northern Indian Ocean to study the impact of May 2007 swells on the wave climate. An average of around

  14. Random-forcing model of the mesoscale oceanic eddies

    NASA Astrophysics Data System (ADS)

    Berloff, Pavel S.

    2005-04-01

    The role of mesoscale oceanic eddies in driving large-scale currents is studied in an eddy-resolving midlatitude double-gyre ocean model. The reference solution is decomposed into large-scale and eddy components in a way which is dynamically consistent with a non-eddy-resolving ocean model. That is, the non-eddy-resolving solution driven by this eddy-forcing history, calculated on the basis of this decomposition, correctly approximates the original flow. The main effect of the eddy forcing on the large-scale flow is to enhance the eastward-jet extension of the subtropical western boundary current. This is an anti-diffusive process, which cannot be represented in terms of turbulent diffusion. It is shown that the eddy-forcing history can be approximated as a space-time correlated, random-forcing process in such a way that the non-eddy-resolving solution correctly approximates the reference solution. Thus, the random-forcing model can potentially replace the diffusion model, which is commonly used to parameterize eddy effects on the large-scale currents. The eddy-forcing statistics are treated as spatially inhomogeneous but stationary, and the dynamical roles of space-time correlations and spatial inhomogeneities are systematically explored. The integral correlation time, oscillations of the space correlations, and inhomogeneity of the variance are found to be particularly important for the flow response.

  15. Tasman leakage in a fine-resolution ocean model

    NASA Astrophysics Data System (ADS)

    van Sebille, Erik; England, Matthew H.; Zika, Jan D.; Sloyan, Bernadette M.

    2012-03-01

    Tasman leakage, the westward flow of thermocline waters south of Australia from the Pacific to the Indian Ocean, is one of the lesser-studied of the inter-ocean exchanges. Here, some of the properties of the Tasman leakage are inferred from Lagrangian particles integrated using the three-dimensional velocity fields of the 1/10 degree resolution OFES model. The mean Tasman leakage in this model is 4.2 Sv, with a standard deviation of 4.3 Sv. The heat flux associated with this leakage lies in the range 0.08-0.18 PW. There is large variability in the Tasman leakage on both sub-weekly and inter-annual scales, but no trend over the 1983-1997 period. Despite the large weekly variability, with peaks of more than 20 Sv, it appears that less than half of the Tasman leakage is carried within eddies.

  16. Modelling coral polyp calcification in relation to ocean acidification

    NASA Astrophysics Data System (ADS)

    Hohn, S.; Merico, A.

    2012-11-01

    Rising atmospheric CO2 concentrations due to anthropogenic emissions induce changes in the carbonate chemistry of the oceans and, ultimately, a drop in ocean pH. This acidification process can harm calcifying organisms like coccolithophores, molluscs, echinoderms, and corals. It is expected that ocean acidification in combination with other anthropogenic stressors will cause a severe decline in coral abundance by the end of this century, with associated disastrous effects on reef ecosystems. Despite the growing importance of the topic, little progress has been made with respect to modelling the impact of acidification on coral calcification. Here we present a model for a coral polyp that simulates the carbonate system in four different compartments: the seawater, the polyp tissue, the coelenteron, and the calcifying fluid. Precipitation of calcium carbonate takes place in the metabolically controlled calcifying fluid beneath the polyp tissue. The model is adjusted to a state of activity as observed by direct microsensor measurements in the calcifying fluid. We find that a transport mechanism for bicarbonate is required to supplement carbon into the calcifying fluid because CO2 diffusion alone is not sufficient to sustain the observed calcification rates. Simulated CO2 perturbation experiments reveal decreasing calcification rates under elevated pCO2 despite the strong metabolic control of the calcifying fluid. Diffusion of CO2 through the tissue into the calcifying fluid increases with increasing seawater pCO2, leading to decreased aragonite saturation in the calcifying fluid. Our modelling study provides important insights into the complexity of the calcification process at the organism level and helps to quantify the effect of ocean acidification on corals.

  17. Theory and Practice of Data Assimilation in Ocean Modeling

    DTIC Science & Technology

    2009-01-01

    assimilation methods for regional to basin scale ocean models. Since data assimilation methods that give the most and best information are highly...accuracy and confidence for using economical but suboptimal data assimilation methods . Direct calculation of full PDFs is not feasible for...estimates. APPROACH The basic assumptions underlying data assimilation methods in use or proposed are known to be false to some degree. We plan

  18. Theory and Practice of Data Assimilation in Ocean Modeling

    DTIC Science & Technology

    2008-09-30

    objective of this project is the development, implementation and evaluation of practical data assimilation methods for regional to basin scale ocean...models. Since data assimilation methods that give the most and best information are highly resource intensive, and often not practical for use with... assimilation methods . 1 Report Documentation Page Form ApprovedOMB No. 0704-0188 Public reporting burden for the collection of information is estimated to

  19. Anisotropic Mesoscale Eddy Transport in Ocean General Circulation Models

    NASA Astrophysics Data System (ADS)

    Reckinger, S. J.; Fox-Kemper, B.; Bachman, S.; Bryan, F.; Dennis, J.; Danabasoglu, G.

    2014-12-01

    Modern climate models are limited to coarse-resolution representations of large-scale ocean circulation that rely on parameterizations for mesoscale eddies. The effects of eddies are typically introduced by relating subgrid eddy fluxes to the resolved gradients of buoyancy or other tracers, where the proportionality is, in general, governed by an eddy transport tensor. The symmetric part of the tensor, which represents the diffusive effects of mesoscale eddies, is universally treated isotropically in general circulation models. Thus, only a single parameter, namely the eddy diffusivity, is used at each spatial and temporal location to impart the influence of mesoscale eddies on the resolved flow. However, the diffusive processes that the parameterization approximates, such as shear dispersion, potential vorticity barriers, oceanic turbulence, and instabilities, typically have strongly anisotropic characteristics. Generalizing the eddy diffusivity tensor for anisotropy extends the number of parameters to three: a major diffusivity, a minor diffusivity, and the principal axis of alignment. The Community Earth System Model (CESM) with the anisotropic eddy parameterization is used to test various choices for the newly introduced parameters, which are motivated by observations and the eddy transport tensor diagnosed from high resolution simulations. Simply setting the ratio of major to minor diffusivities to a value of five globally, while aligning the major axis along the flow direction, improves biogeochemical tracer ventilation and reduces global temperature and salinity biases. These effects can be improved even further by parameterizing the anisotropic transport mechanisms in the ocean.

  20. A Pacific Ocean general circulation model for satellite data assimilation

    NASA Technical Reports Server (NTRS)

    Chao, Y.; Halpern, D.; Mechoso, C. R.

    1991-01-01

    A tropical Pacific Ocean General Circulation Model (OGCM) to be used in satellite data assimilation studies is described. The transfer of the OGCM from a CYBER-205 at NOAA's Geophysical Fluid Dynamics Laboratory to a CRAY-2 at NASA's Ames Research Center is documented. Two 3-year model integrations from identical initial conditions but performed on those two computers are compared. The model simulations are very similar to each other, as expected, but the simulations performed with the higher-precision CRAY-2 is smoother than that with the lower-precision CYBER-205. The CYBER-205 and CRAY-2 use 32 and 64-bit mantissa arithmetic, respectively. The major features of the oceanic circulation in the tropical Pacific, namely the North Equatorial Current, the North Equatorial Countercurrent, the South Equatorial Current, and the Equatorial Undercurrent, are realistically produced and their seasonal cycles are described. The OGCM provides a powerful tool for study of tropical oceans and for the assimilation of satellite altimetry data.

  1. Ocean modelling for aquaculture and fisheries in Irish waters

    NASA Astrophysics Data System (ADS)

    Dabrowski, T.; Lyons, K.; Cusack, C.; Casal, G.; Berry, A.; Nolan, G. D.

    2016-01-01

    The Marine Institute, Ireland, runs a suite of operational regional and coastal ocean models. Recent developments include several tailored products that focus on the key needs of the Irish aquaculture sector. In this article, an overview of the products and services derived from the models are presented. The authors give an overview of a shellfish model developed in-house and that was designed to predict the growth, the physiological interactions with the ecosystem, and the level of coliform contamination of the blue mussel. As such, this model is applicable in studies on the carrying capacity of embayments, assessment of the impacts of pollution on aquaculture grounds, and the determination of shellfish water classes. Further services include the assimilation of the model-predicted shelf water movement into a new harmful algal bloom alert system used to inform end users of potential toxic shellfish events and high biomass blooms that include fish-killing species. Models are also used to identify potential sites for offshore aquaculture, to inform studies of potential cross-contamination in farms from the dispersal of planktonic sea lice larvae and other pathogens that can infect finfish, and to provide modelled products that underpin the assessment and advisory services on the sustainable exploitation of the resources of marine fisheries. This paper demonstrates that ocean models can provide an invaluable contribution to the sustainable blue growth of aquaculture and fisheries.

  2. An equilibrium model for the coupled ocean-atmosphere boundary layer in the tropics

    NASA Technical Reports Server (NTRS)

    Sui, C.-H.; Lau, K.-M.; Betts, Alan K.

    1991-01-01

    An atmospheric convective boundary layer (CBL) model is coupled to an ocean mixed-layer (OML) model in order to study the equilibrium state of the coupled system in the tropics, particularly in the Pacific region. The equilibrium state of the coupled system is solved as a function of sea-surface temperature (SST) for a given surface wind and as a function of surface wind for a given SST. It is noted that in both cases, the depth of the CBL and OML increases and the upwelling below the OML decreases, corresponding to either increasing SST or increasing surface wind. The coupled ocean-atmosphere model is solved iteratively as a function of surface wind for a fixed upwelling and a fixed OML depth, and it is observed that SST falls with increasing wind in both cases. Realistic gradients of mixed-layer depth and upwelling are observed in experiments with surface wind and SST prescribed as a function of longitude.

  3. Theoretical comparison of subgrid turbulence in atmospheric and oceanic quasi-geostrophic models

    NASA Astrophysics Data System (ADS)

    Kitsios, Vassili; Frederiksen, Jorgen S.; Zidikheri, Meelis J.

    2016-04-01

    Due to the massive disparity between the largest and smallest eddies in the atmosphere and ocean, it is not possible to simulate these flows by explicitly resolving all scales on a computational grid. Instead the large scales are explicitly resolved, and the interactions between the unresolved subgrid turbulence and large resolved scales are parameterised. If these interactions are not properly represented then an increase in resolution will not necessarily improve the accuracy of the large scales. This has been a significant and long-standing problem since the earliest climate simulations. Historically subgrid models for the atmosphere and ocean have been developed in isolation, with the structure of each motivated by different physical phenomena. Here we solve the turbulence closure problem by determining the parameterisation coefficients (eddy viscosities) from the subgrid statistics of high-resolution quasi-geostrophic atmospheric and oceanic simulations. These subgrid coefficients are characterised into a set of simple unifying scaling laws, for truncations made within the enstrophy-cascading inertial range. The ocean additionally has an inverse energy cascading range, within which the subgrid model coefficients have different scaling properties. Simulations adopting these scaling laws are shown to reproduce the statistics of the reference benchmark simulations across resolved scales, with orders of magnitude improvement in computational efficiency. This reduction in both resolution dependence and computational effort will improve the efficiency and accuracy of geophysical research and operational activities that require data generated by general circulation models, including weather, seasonal, and climate prediction; transport studies; and understanding natural variability and extreme events.

  4. Time domain analysis of the weighted distributed order rheological model

    NASA Astrophysics Data System (ADS)

    Cao, Lili; Pu, Hai; Li, Yan; Li, Ming

    2016-11-01

    This paper presents the fundamental solution and relevant properties of the weighted distributed order rheological model in the time domain. Based on the construction of distributed order damper and the idea of distributed order element networks, this paper studies the weighted distributed order operator of the rheological model, a generalization of distributed order linear rheological model. The inverse Laplace transform on weighted distributed order operators of rheological model has been obtained by cutting the complex plane and computing the complex path integral along the Hankel path, which leads to the asymptotic property and boundary discussions. The relaxation response to weighted distributed order rheological model is analyzed, and it is closely related to many physical phenomena. A number of novel characteristics of weighted distributed order rheological model, such as power-law decay and intermediate phenomenon, have been discovered as well. And meanwhile several illustrated examples play important role in validating these results.

  5. Ocean Hydrodynamics Numerical Model in Curvilinear Coordinates for Simulating Circulation of the Global Ocean and its Separate Basins.

    NASA Astrophysics Data System (ADS)

    Gusev, Anatoly; Diansky, Nikolay; Zalesny, Vladimir

    2010-05-01

    The original program complex is proposed for the ocean circulation sigma-model, developed in the Institute of Numerical Mathematics (INM), Russian Academy of Sciences (RAS). The complex can be used in various curvilinear orthogonal coordinate systems. In addition to ocean circulation model, the complex contains a sea ice dynamics and thermodynamics model, as well as the original system of the atmospheric forcing implementation on the basis of both prescribed meteodata and atmospheric model results. This complex can be used as the oceanic block of Earth climate model as well as for solving the scientific and practical problems concerning the World ocean and its separate oceans and seas. The developed program complex can be effectively used on parallel shared memory computational systems and on contemporary personal computers. On the base of the complex proposed the ocean general circulation model (OGCM) was developed. The model is realized in the curvilinear orthogonal coordinate system obtained by the conformal transformation of the standard geographical grid that allowed us to locate the system singularities outside the integration domain. The horizontal resolution of the OGCM is 1 degree on longitude, 0.5 degree on latitude, and it has 40 non-uniform sigma-levels in depth. The model was integrated for 100 years starting from the Levitus January climatology using the realistic atmospheric annual cycle calculated on the base of CORE datasets. The experimental results showed us that the model adequately reproduces the basic characteristics of large-scale World Ocean dynamics, that is in good agreement with both observational data and results of the best climatic OGCMs. This OGCM is used as the oceanic component of the new version of climatic system model (CSM) developed in INM RAS. The latter is now ready for carrying out the new numerical experiments on climate and its change modelling according to IPCC (Intergovernmental Panel on Climate Change) scenarios in the

  6. Modelling the Oceanic Nd Isotopic Composition With a North Atlantic Eddy Permitting Model

    NASA Astrophysics Data System (ADS)

    Peronne, S.; Treguier, A.; Arsouze, T.; Dutay, J.; Lacan, F.; Jeandel, C.

    2006-12-01

    The oceanic water masses differ by their temperatures, salinity, but also a number of geochemical tracers characterized by their weak concentrations and their ability to quantify oceanic processes (mixing, scavenging rates etc). Among these tracers, the Nd isotopic composition (hereafter epsilon-Nd) is a (quasi) conservative tracer of water mass mixing in the ocean interior, far from any lithogenic inputs. It has been recently established that exchange of Nd at the oceanic margins could be the dominant process controlling both its concentration and isotopic composition distribution in the ocean. This was demonstrated using in situ measurements and budget calculations and has recently been confirmed by a low resolution (2°) modeling approach (Arsouze et al., 2006). However, the currents flowing on the ocean margins are not correctly represented in coarse ocean models. It is the case in the North Atlantic ocean, which is of particular interest since i) it is the area of deep water formation and ii) these deep waters are characterized by the most negative epsilon-Nd values of the world ocean, which are used as "imprint" of the present and past thermohaline circulation. It is therefore essential to understand how these water masses acquire their epsilon-Nd signature. We propose here the first results of the modeling of oceanic Nd isotopic composition at eddy-permitting resolution, with the North Atlantic 0.25° version of the NEMO model used for the DRAKKAR European project. A 150 years off-line experiment and a shorter on-line experiment are performed. Simulated Nd distributions are compared to the present-day data base, vertical profiles, and the results of the low resolution model (in the North Atlantic). The eddy permitting model generally provides improved results, provided a high enough exchange rate is imposed in the deep ocean. Deficiencies of the simulated distribution in the Nordic Seas and the subpolar gyre are explained by errors in the input function on

  7. Global Ocean Circulation Modeling with an Isopycnic Coordinate Model. Final Report for May 1, 1998 - April 30, 2002

    SciTech Connect

    Bleck, R.

    2004-05-19

    The overall aim of this project was to continue development of a global version of the Miami Isopycnic Coordinate Ocean Model (MICOM) with the intent of turning it into a full-fledged oceanic component of an earth system model.

  8. Modeling oceanic multiphase flow by using Lagrangian particle tracking

    NASA Astrophysics Data System (ADS)

    Matsumura, Y.

    2014-12-01

    While the density of seawater is basically determined by its temperature, salinity and pressure, the effective density becomes higher when the water mass contains suspended sediment. On the other hands, effective density declines when water mass contains fine scale materials of lower density such as bubbles and ice crystals. Such density anomaly induced by small scale materials suspended in water masses sometimes plays important roles in the sub-mesoscale ocean physics. To simulate these small scale oceanic multiphase flow, a new modeling framework using an online Lagrangian particle tracking method is developed. A Lagrangian particle tracking method has substantial advantages such as an explicit treatment of buoyancy force acting on each individual particle, no numerical diffusion and dissipation, high dynamic range and an ability to track the history and each individual particle. However, its numerical cost causes difficulty when we try to simulate a large number of particles. In the present study we implement a numerically efficient particle tracking scheme using linked-list data structure, which is coupled with a nonhydrostatic dynamical core. This newly developed model successfully reproduces characteristics of some interesting small scale multiphase processes, for example hyperpycnal flow (a sediment-rich river water plume trapped at ocean floor) and grease ice cover (a slurry mixture of frazil ice crystals and seawater).

  9. Modeling of Oceanic Gas Hydrate Instability and Methane Release in Response to Climate Change

    SciTech Connect

    Reagan, Matthew; Reagan, Matthew T.; Moridis, George J.

    2008-04-15

    Paleooceanographic evidence has been used to postulate that methane from oceanic hydrates may have had a significant role in regulating global climate, implicating global oceanic deposits of methane gas hydrate as the main culprit in instances of rapid climate change that have occurred in the past. However, the behavior of contemporary oceanic methane hydrate deposits subjected to rapid temperature changes, like those predicted under future climate change scenarios, is poorly understood. To determine the fate of the carbon stored in these hydrates, we performed simulations of oceanic gas hydrate accumulations subjected to temperature changes at the seafloor and assessed the potential for methane release into the ocean. Our modeling analysis considered the properties of benthic sediments, the saturation and distribution of the hydrates, the ocean depth, the initial seafloor temperature, and for the first time, estimated the effect of benthic biogeochemical activity. The results show that shallow deposits--such as those found in arctic regions or in the Gulf of Mexico--can undergo rapid dissociation and produce significant methane fluxes of 2 to 13 mol/yr/m{sup 2} over a period of decades, and release up to 1,100 mol of methane per m{sup 2} of seafloor in a century. These fluxes may exceed the ability of the seafloor environment (via anaerobic oxidation of methane) to consume the released methane or sequester the carbon. These results will provide a source term to regional or global climate models in order to assess the coupling of gas hydrate deposits to changes in the global climate.

  10. Subaqueous melting in Zachariae Isstrom, Northeast Greenland combining observations and an ocean general circulation model

    NASA Astrophysics Data System (ADS)

    Cai, C.; Rignot, E. J.; Menemenlis, D.

    2015-12-01

    Zachariae Isstrom, a major ice stream in northeast Greenland, has lost its entire ice shelf in the past decade. Here, we study the evolution of subaqueous melting of its floating section during the transition. Observations show that the rate of ice shelf melting has doubled during 1999-2010 and is twice higher than that maintaining the ice shelf in a state of mass equilibrium. The ice shelf melt rate depends on the thermal forcing from warm, salty, subsurface ocean water of Atlantic origin (AW), and - in contrast with Antarctic ice shelves - on the mixing of AW with fresh buoyant subglacial discharge. Subglacial discharge has increased as result of enhanced ice sheet runoff driven by warmer air temperature; ocean thermal forcing has increased due enhanced advection of AW. Here, we employ the Massassuchetts Institute of Technology general circulation model (MITgcm) at a high spatial resolution (1 m horizontal and 1 m vertical spacing near the grounding line) to simulate the melting process in 3-D. The model is constrained by ice thickness from mass conservation, oceanic bathymetry from NASA Operation IceBridge gravity data, in-situ ocean temperature/salinity data, ocean tide height and current from the Arctic Ocean Tidal Inverse Model (AOTIM-5) and subglacial discharge from output products of the Regional Atmospheric Climate Model (RACMO). We compare the results in winter (no runoff) with summer (maximum runoff) at two different stages with (prior to 2012) and without the ice shelf (after 2012) to subaqueous melt rates deduced from remote sensing observations. We show that ice melting by the ocean has increased by one order of magnitude as a result of the transition from ice shelf terminating to near-vertical calving front terminating. We also find that subglacial discharge has a significant impact on the ice shelf melt rates in Greenland. We conclude on the impact of ocean warming and air temperature warming on the melting regime of the ice margin of Zachariae

  11. Strong coupling among Antarctic ice shelves, ocean circulation and sea ice in a global sea-ice - ocean circulation model

    NASA Astrophysics Data System (ADS)

    Sergienko, Olga

    2016-04-01

    The thermodynamic effects of Antarctic ice shelf interaction with ocean circulation are investigated using a global, high-resolution, isopycnal ocean-circulation model coupled to a sea-ice model. The model uses NASA MERRA Reanalysis from 1992 to 2011 as atmospheric forcing. The simulated long-period variability of ice-shelf melting/freezing rates differ across geographic locations. The ice shelves in Antarctic Peninsula, Amundsen and Bellingshausen sea embayments and the Amery Ice Shelf experience an increase in melting starting from 2005. This increase in melting is due to an increase in the subsurface (100-500 m) ocean heat content in the embayments of these ice shelves, which is caused by an increase in sea-ice concentration after 2005, and consequent reduction of the heat loss to the atmosphere. Our simulations provide a strong evidence for a coupling between ocean circulation, sea ice and ice shelves.

  12. Predicting interactions among fishing, ocean warming, and ocean acidification in a marine system with whole-ecosystem models.

    PubMed

    Griffith, Gary P; Fulton, Elizabeth A; Gorton, Rebecca; Richardson, Anthony J

    2012-12-01

    An important challenge for conservation is a quantitative understanding of how multiple human stressors will interact to mitigate or exacerbate global environmental change at a community or ecosystem level. We explored the interaction effects of fishing, ocean warming, and ocean acidification over time on 60 functional groups of species in the southeastern Australian marine ecosystem. We tracked changes in relative biomass within a coupled dynamic whole-ecosystem modeling framework that included the biophysical system, human effects, socioeconomics, and management evaluation. We estimated the individual, additive, and interactive effects on the ecosystem and for five community groups (top predators, fishes, benthic invertebrates, plankton, and primary producers). We calculated the size and direction of interaction effects with an additive null model and interpreted results as synergistic (amplified stress), additive (no additional stress), or antagonistic (reduced stress). Individually, only ocean acidification had a negative effect on total biomass. Fishing and ocean warming and ocean warming with ocean acidification had an additive effect on biomass. Adding fishing to ocean warming and ocean acidification significantly changed the direction and magnitude of the interaction effect to a synergistic response on biomass. The interaction effect depended on the response level examined (ecosystem vs. community). For communities, the size, direction, and type of interaction effect varied depending on the combination of stressors. Top predator and fish biomass had a synergistic response to the interaction of all three stressors, whereas biomass of benthic invertebrates responded antagonistically. With our approach, we were able to identify the regional effects of fishing on the size and direction of the interacting effects of ocean warming and ocean acidification.

  13. Impact of an upgraded model in the NCEP Global Ocean Data Assimilation System: The tropical Indian Ocean

    NASA Astrophysics Data System (ADS)

    Rahaman, Hasibur; Behringer, David W.; Penny, Stephen G.; Ravichandran, M.

    2016-11-01

    The National Centers for Environmental Prediction (NCEP) and the Indian National Centre for Ocean Information Services (INCOIS) produces global ocean analysis based on the Global Ocean Data Assimilation System (GODAS). This study shows how upgrades to the forward model simulations from MOM4p0d to MOM4p1 impact ocean analyses over the tropical Indian Ocean in GODAS. Three experiments were performed with same atmospheric forcing fields: (i) using MOM4p0d (GODAS_p0), (ii) using MOM4p1 (GODAS_p1), both using observed temperature and synthetic salinity, and (iii) using MOM4p1 (GODAS_p1S) assimilating both observed temperature and observed salinity. Validation with independent observations shows significant improvement of subsurface temperature and salinity in the new analysis using MOM4p1 versus MOM4p0d. There is also improvement in the upper ocean current of the equatorial Indian Ocean. The impact of observed salinity on the upper ocean surface current is marginal, but there is significant improvement in the subsurface current. The seasonal and inter-annual variability of the Wyrtki jet and the equatorial undercurrent is improved in GODAS_p1 versus GODAS_p0. All analyses reproduced the Indian Ocean dipole, with the GODAS_p1S simulated sea surface temperature (SST) the most accurate. The temperature inversion over the north Bay of Bengal (BoB) is reproduced only in GODAS_p1S. The mean sea level over BoB and equatorial Indian Ocean improved in GODAS_p1S as compared with AVISO observation. The combined model upgrade and assimilation of observed salinity led to reduced root-mean-square deviation and higher correlation coefficient values in the sea level anomaly (SLA) when compared with satellite observations.

  14. Reduced-Order Models for Acoustic Response Prediction

    DTIC Science & Technology

    2011-07-01

    acoustic and thermal loading. These methods reduce a finite element model to a reduced-order system of nonlinear modal equations. A short...magnitude reductions in computational cost over full-order finite element analysis. 15. SUBJECT TERMS sonic fatigue, reduced-order models, acoustic...4.4.3 Vacuum Shaker Test ...........................................................................................93 4.4.4 Finite element

  15. Biomineral shell formation under ocean acidification: a shift from order to chaos

    PubMed Central

    Fitzer, Susan C.; Chung, Peter; Maccherozzi, Francesco; Dhesi, Sarnjeet S.; Kamenos, Nicholas A.; Phoenix, Vernon R.; Cusack, Maggie

    2016-01-01

    Biomineral production in marine organisms employs transient phases of amorphous calcium carbonate (ACC) in the construction of crystalline shells. Increasing seawater pCO2 leads to ocean acidification (OA) with a reduction in oceanic carbonate concentration which could have a negative impact on shell formation and therefore survival. We demonstrate significant changes in the hydrated and dehydrated forms of ACC in the aragonite and calcite layers of Mytilus edulis shells cultured under acidification conditions (1000 μatm pCO2) compared to present day conditions (380 μatm pCO2). In OA conditions, Mytilus edulis has more ACC at crystalisation sites. Here, we use the high-spatial resolution of synchrotron X-ray Photo Emission Electron Microscopy (XPEEM) combined with X-ray Absorption Spectroscopy (XAS) to investigate the influence of OA on the ACC formation in the shells of adult Mytilus edulis. Electron Backscatter Diffraction (EBSD) confirms that OA reduces crystallographic control of shell formation. The results demonstrate that OA induces more ACC formation and less crystallographic control in mussels suggesting that ACC is used as a repair mechanism to combat shell damage under OA. However, the resultant reduced crystallographic control in mussels raises concerns for shell protective function under predation and changing environments. PMID:26876022

  16. Biomineral shell formation under ocean acidification: a shift from order to chaos

    NASA Astrophysics Data System (ADS)

    Fitzer, Susan C.; Chung, Peter; Maccherozzi, Francesco; Dhesi, Sarnjeet S.; Kamenos, Nicholas A.; Phoenix, Vernon R.; Cusack, Maggie

    2016-02-01

    Biomineral production in marine organisms employs transient phases of amorphous calcium carbonate (ACC) in the construction of crystalline shells. Increasing seawater pCO2 leads to ocean acidification (OA) with a reduction in oceanic carbonate concentration which could have a negative impact on shell formation and therefore survival. We demonstrate significant changes in the hydrated and dehydrated forms of ACC in the aragonite and calcite layers of Mytilus edulis shells cultured under acidification conditions (1000 μatm pCO2) compared to present day conditions (380 μatm pCO2). In OA conditions, Mytilus edulis has more ACC at crystalisation sites. Here, we use the high-spatial resolution of synchrotron X-ray Photo Emission Electron Microscopy (XPEEM) combined with X-ray Absorption Spectroscopy (XAS) to investigate the influence of OA on the ACC formation in the shells of adult Mytilus edulis. Electron Backscatter Diffraction (EBSD) confirms that OA reduces crystallographic control of shell formation. The results demonstrate that OA induces more ACC formation and less crystallographic control in mussels suggesting that ACC is used as a repair mechanism to combat shell damage under OA. However, the resultant reduced crystallographic control in mussels raises concerns for shell protective function under predation and changing environments.

  17. Fractional-order variational optical flow model for motion estimation.

    PubMed

    Chen, Dali; Sheng, Hu; Chen, YangQuan; Xue, Dingyü

    2013-05-13

    A new class of fractional-order variational optical flow models, which generalizes the differential of optical flow from integer order to fractional order, is proposed for motion estimation in this paper. The corresponding Euler-Lagrange equations are derived by solving a typical fractional variational problem, and the numerical implementation based on the Grünwald-Letnikov fractional derivative definition is proposed to solve these complicated fractional partial differential equations. Theoretical analysis reveals that the proposed fractional-order variational optical flow model is the generalization of the typical Horn and Schunck (first-order) variational optical flow model and the second-order variational optical flow model, which provides a new idea for us to study the optical flow model and has an important theoretical implication in optical flow model research. The experiments demonstrate the validity of the generalization of differential order.

  18. Upper oceanic response to tropical cyclone Phailin in the Bay of Bengal using a coupled atmosphere-ocean model

    NASA Astrophysics Data System (ADS)

    Prakash, Kumar Ravi; Pant, Vimlesh

    2017-01-01

    A numerical simulation of very severe cyclonic storm `Phailin', which originated in southeastern Bay of Bengal (BoB) and propagated northwestward during 10-15 October 2013, was carried out using a coupled atmosphere-ocean model. A Model Coupling Toolkit (MCT) was used to make exchanges of fluxes consistent between the atmospheric model `Weather Research and Forecasting' (WRF) and ocean circulation model `Regional Ocean Modelling System' (ROMS) components of the `Coupled Ocean-Atmosphere-Wave-Sediment Transport' (COAWST) modelling system. The track and intensity of tropical cyclone (TC) Phailin simulated by the WRF component of the coupled model agrees well with the best-track estimates reported by the India Meteorological Department (IMD). Ocean model component (ROMS) was configured over the BoB domain; it utilized the wind stress and net surface heat fluxes from the WRF model to investigate upper oceanic response to the passage of TC Phailin. The coupled model shows pronounced sea surface cooling (2-2.5 °C) and an increase in sea surface salinity (SSS) (2-3 psu) after 06 GMT on 12 October 2013 over the northwestern BoB. Signature of this surface cooling was also observed in satellite data and buoy measurements. The oceanic mixed layer heat budget analysis reveals relative roles of different oceanic processes in controlling the mixed layer temperature over the region of observed cooling. The heat budget highlighted major contributions from horizontal advection and vertical entrainment processes in governing the mixed layer cooling (up to -0.1 °C h-1) and, thereby, reduction in sea surface temperature (SST) in the northwestern BoB during 11-12 October 2013. During the post-cyclone period, the net heat flux at surface regained its diurnal variations with a noontime peak that provided a warming tendency up to 0.05 °C h-1 in the mixed layer. Clear signatures of TC-induced upwelling are seen in vertical velocity (about 2.5 × 10-3 m s-1), rise in isotherms and

  19. Implementation of a direct nonhydrostatic pressure gradient discretisation into a layered ocean model

    NASA Astrophysics Data System (ADS)

    Klingbeil, Knut; Burchard, Hans

    2013-05-01

    The increasing demand for the investigation of nonhydrostatic effects in ocean modelling requires crucial modifications to models applying the hydrostatic pressure assumption. Within many studies the capability of the pressure-correcting projection method for the inclusion of the missing nonhydrostatic pressure contribution into an existing hydrostatic model kernel was verified. It provides accurate results but also requires computational (and implementational) effort for solving a Poisson equation for the pressure correction. In contrast, some studies were based on an alternative approach that does not require the inversion of a Poisson equation. Within this alternative approach the nonhydrostatic pressure contribution is calculated by an explicit vertical integration of the additional nonhydrostatic terms in the balance of vertical momentum. Since ocean models are not intended to replace classical engineering tools and are usually applied to nearly hydrostatic flows, this straight-forward extension of the hydrostatic procedure is an interesting option. However, the feasibility of the alternative approach was not tested within a full 3D explicit mode-splitting model yet. Furthermore, the nonhydrostatic capability of the alternative approach has so far not been validated against well known nonhydrostatic benchmark test cases. In order to assess the potential of the alternative approach for future ocean modelling applications, in the present study these required but still missing investigations are carried out. To demonstrate the necessary modifications to an explicit mode-splitting hydrostatic model kernel, the extension of the General Estuarine Transport Model (GETM) is outlined. The simulation results of laboratory and idealised oceanic test cases are presented and compared to analytical theory, laboratory experiments and other numerical simulations. This validation indicates the nonhydrostatic capability of the extended GETM. However, stability issues limited

  20. gpuPOM: a GPU-based Princeton Ocean Model

    NASA Astrophysics Data System (ADS)

    Xu, S.; Huang, X.; Zhang, Y.; Fu, H.; Oey, L.-Y.; Xu, F.; Yang, G.

    2014-11-01

    Rapid advances in the performance of the graphics processing unit (GPU) have made the GPU a compelling solution for a series of scientific applications. However, most existing GPU acceleration works for climate models are doing partial code porting for certain hot spots, and can only achieve limited speedup for the entire model. In this work, we take the mpiPOM (a parallel version of the Princeton Ocean Model) as our starting point, design and implement a GPU-based Princeton Ocean Model. By carefully considering the architectural features of the state-of-the-art GPU devices, we rewrite the full mpiPOM model from the original Fortran version into a new Compute Unified Device Architecture C (CUDA-C) version. We take several accelerating methods to further improve the performance of gpuPOM, including optimizing memory access in a single GPU, overlapping communication and boundary operations among multiple GPUs, and overlapping input/output (I/O) between the hybrid Central Processing Unit (CPU) and the GPU. Our experimental results indicate that the performance of the gpuPOM on a workstation containing 4 GPUs is comparable to a powerful cluster with 408 CPU cores and it reduces the energy consumption by 6.8 times.

  1. Present-day Circum-Antarctic Simulations using the POPSICLES Coupled Ice Sheet-Ocean Model

    NASA Astrophysics Data System (ADS)

    Asay-Davis, X.; Martin, D. F.; Price, S. F.; Maltrud, M. E.; Collins, W.

    2014-12-01

    We present POPSICLES simulation results covering the full Antarctic Ice Sheet and the Southern Ocean spanning the period 1990 to 2010. Simulations are performed at 0.1o (~5 km) ocean resolution and with adaptive ice-sheet model resolution as fine as 500 m. We compare time-averaged melt rates below a number of major ice shelves with those reported by Rignot et al. (2013) as well as other recent studies. We also present seasonal variability and decadal trends in submarine melting from several Antarctic regions. Finally, we explore the influence on basal melting and system dynamics resulting from two different choices of climate forcing: a "normal-year" climatology and the CORE v. 2 forcing data (Large and Yeager 2008).POPSICLES couples the POP2x ocean model, a modified version of the Parallel Ocean Program (Smith and Gent, 2002), and the BISICLES ice-sheet model (Cornford et al., 2012). POP2x includes sub-ice-shelf circulation using partial top cells (Losch, 2008) and boundary layer physics following Holland and Jenkins (1999), Jenkins (2001), and Jenkins et al. (2010). Standalone POP2x output compares well with standard ice-ocean test cases (e.g., ISOMIP; Losch, 2008) and other continental-scale simulations and melt-rate observations (Kimura et al., 2013; Rignot et al., 2013). BISICLES makes use of adaptive mesh refinement and a 1st-order accurate momentum balance similar to the L1L2 model of Schoof and Hindmarsh (2009) to accurately model regions of dynamic complexity, such as ice streams, outlet glaciers, and grounding lines. Results of BISICLES simulations have compared favorably to comparable simulations with a Stokes momentum balance in both idealized tests (MISMIP-3D; Pattyn et al., 2013) and realistic configurations (Favier et al. 2014).A companion presentation, "Response of the Antarctic Ice Sheet to ocean forcing using the POPSICLES coupled ice sheet-ocean model" in session C024 covers the ice-sheet response to these melt rates in the coupled simulation

  2. Skill Assessment of a Spectral Ocean-Atmosphere Radiative Model

    NASA Technical Reports Server (NTRS)

    Gregg, Watson, W.; Casey, Nancy W.

    2009-01-01

    Ocean phytoplankton, detrital material, and water absorb and scatter light spectrally. The Ocean- Atmosphere Spectral Irradiance Model (OASIM) is intended to provide surface irradiance over the oceans with sufficient spectral resolution to support ocean ecology, biogeochemistry, and heat exchange investigations, and of sufficient duration to support inter-annual and decadal investigations. OASIM total surface irradiance (integrated 200 nm to 4 microns) was compared to in situ data and three publicly available global data products at monthly 1-degree resolution. OASIM spectrally-integrated surface irradiance had root mean square (RMS) difference= 20.1 W/sq m (about 11%), bias=1.6 W/sq m (about 0.8%), regression slope= 1.01 and correlation coefficient= 0.89, when compared to 2322 in situ observations. OASIM had the lowest bias of any of the global data products evaluated (ISCCP-FD, NCEP, and ISLSCP 11), and the best slope (nearest to unity). It had the second best RMS, and the third best correlation coefficient. OASIM total surface irradiance compared well with ISCCP-FD (RMS= 20.7 W/sq m; bias=-11.4 W/sq m, r=0.98) and ISLSCP II (RMS =25.2 W/sq m; bias= -13.8 W/sq m; r=0.97), but less well with NCEP (RMS =43.0 W/sq m ;bias=-22.6 W/sq m; x=0.91). Comparisons of OASIM photosynthetically available radiation (PAR) with PAR derived from SeaWiFS showed low bias (-1.8 mol photons /sq m/d, or about 5%), RMS (4.25 mol photons /sq m/d ' or about 12%), near unity slope (1.03) and high correlation coefficient (0.97). Coupled with previous estimates of clear sky spectral irradiance in OASIM (6.6% RMS at 1 nm resolution), these results suggest that OASIM provides reasonable estimates of surface broadband and spectral irradiance in the oceans, and can support studies on ocean ecosystems, carbon cycling, and heat exchange.

  3. Bio-Optical Measurement and Modeling of the California Current and Southern Oceans

    NASA Technical Reports Server (NTRS)

    Mitchell, B. Gregg; Mitchell, B. Greg

    2003-01-01

    The SIMBIOS project's principal goals are to validate standard or experimental ocean color products through detailed bio-optical and biogeochemical measurements, and to combine Ocean optical observations with modeling to contribute to satellite vicarious radiometric calibration and algorithm development.

  4. An Eddy-Resolving Ocean Reanalysis using the 1/12 degree Global HYbrid Coordinate Ocean Model (HYCOM) and the Navy Coupled Ocean Data Assimilation (NCODA) Scheme

    DTIC Science & Technology

    2013-05-01

    research opportunities 2 HYbrid Coordinate Ocean Model 3 Tri-pole latitudinal grid resolution (km) Mercator projection : 66°S to 47°N Curvi...Data Assimilation (NCODA) scheme 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER 5e. TASK NUMBER...capable of fully resolving oceanic mesoscale features (eddies and current meanders) across the globe • This project addresses the need for a long

  5. Evaluating the ocean biogeochemical components of Earth system models using atmospheric potential oxygen and ocean color data

    NASA Astrophysics Data System (ADS)

    Nevison, C. D.; Manizza, M.; Keeling, R. F.; Kahru, M.; Bopp, L.; Dunne, J.; Tiputra, J.; Ilyina, T.; Mitchell, B. G.

    2015-01-01

    The observed seasonal cycles in atmospheric potential oxygen (APO) at a range of mid- to high-latitude surface monitoring sites are compared to those inferred from the output of six Earth system models (ESMs) participating in the fifth phase of the Coupled Model Intercomparison Project phase 5 (CMIP5). The simulated air-sea O2 fluxes are translated into APO seasonal cycles using a matrix method that takes into account atmospheric transport model (ATM) uncertainty among 13 different ATMs. Three of the ocean biogeochemistry models tested are able to reproduce the observed APO cycles at most sites, to within the large TransCom3-era ATM uncertainty used here, while the other three generally are not. Net primary production (NPP) and net community production (NCP), as estimated from satellite ocean color data, provide additional constraints, albeit more with respect to the seasonal phasing of ocean model productivity than overall magnitude. The present analysis suggests that, of the tested ocean biogeochemistry models, the community ecosystem model (CESM) and the Geophysical Fluid Dynamics Laboratory (GFDL) ESM2M are best able to capture the observed APO seasonal cycle at both northern and southern hemispheric sites. In most models, discrepancies with observed APO can be attributed to the underestimation of NPP, deep ventilation or both in the northern oceans.

  6. The development of a coupled ice-ocean model for forecasting ice conditions in the Arctic

    NASA Astrophysics Data System (ADS)

    Riedlinger, Shelley H.; Preller, Ruth H.

    1991-09-01

    A coupled ice-ocean model has been developed to investigate how a better simulation of ice-ocean interaction can improve sea ice forecasting capabilities. The coupling of the ice and ocean results in improved temporal variability of ocean circulation and heat and salt exchange between ice and ocean. The U.S. Navy's Polar Ice Prediction System is coupled to a diagnostic version of the Bryan-Cox three-dimensional ocean circulation model. A horizontal grid spacing of 127 km was used in the coupled model with 17 vertical levels from the surface to the ocean bottom. Atmospheric data from the Naval Operational Global Atmospheric Prediction System (NOGAPS) for 1986 were used to force the model. The ice-ocean model simulation yielded realistic ice thickness distributions, ice drifts, and ocean currents. The model predicted accurate seasonal trends in ice growth and decay. Excess ice is often grown in the Greenland and Barents seas in fall and winter. This is due, in part, to the model's grid resolution which does not accurately resolve narrow currents, such as the West Spitsbergen Current. A sensitivity study of the heat transfer coefficients used in the ice model showed that the ice edge could be improved by using different coefficient values for thick ice, thin ice, and open water. Other sensitivity studies examined the effect of removing the "distorted" physics frequently used in the Bryan-Cox ocean circulation model and the effect of the vertical eddy momentum coefficient on the surface ocean circulation. An additional simulation was made using 1989 NOGAPS forcing to examine what type of variability could occur when using different years of NOGAPS forcing in the diagnostic ocean model. Significant differences occurred between the 1989 and 1986 ice thickness distributions as well as the oceanic heat fluxes. These differences show that the forecast system, which presently uses an ocean "climatology," can benefit from the variability allowed by the diagnostic ocean model.

  7. The Design and Analysis of Salmonid Tagging Studies in the Columbia Basin; Volume XII; A Multinomial Model for Estimating Ocean Survival from Salmonid Coded Wire-Tag Data.

    SciTech Connect

    Ryding, Kristen E.; Skalski, John R.

    1999-06-01

    The purpose of this report is to illustrate the development of a stochastic model using coded wire-tag (CWT) release and age-at-return data, in order to regress first year ocean survival probabilities against coastal ocean conditions and climate covariates.

  8. Complex functionality with minimal computation: Promise and pitfalls of reduced-tracer ocean biogeochemistry models

    NASA Astrophysics Data System (ADS)

    Galbraith, Eric D.; Dunne, John P.; Gnanadesikan, Anand; Slater, Richard D.; Sarmiento, Jorge L.; Dufour, Carolina O.; de Souza, Gregory F.; Bianchi, Daniele; Claret, Mariona; Rodgers, Keith B.; Marvasti, Seyedehsafoura Sedigh

    2015-12-01

    Earth System Models increasingly include ocean biogeochemistry models in order to predict changes in ocean carbon storage, hypoxia, and biological productivity under climate change. However, state-of-the-art ocean biogeochemical models include many advected tracers, that significantly increase the computational resources required, forcing a trade-off with spatial resolution. Here, we compare a state-of-the art model with 30 prognostic tracers (TOPAZ) with two reduced-tracer models, one with 6 tracers (BLING), and the other with 3 tracers (miniBLING). The reduced-tracer models employ parameterized, implicit biological functions, which nonetheless capture many of the most important processes resolved by TOPAZ. All three are embedded in the same coupled climate model. Despite the large difference in tracer number, the absence of tracers for living organic matter is shown to have a minimal impact on the transport of nutrient elements, and the three models produce similar mean annual preindustrial distributions of macronutrients, oxygen, and carbon. Significant differences do exist among the models, in particular the seasonal cycle of biomass and export production, but it does not appear that these are necessary consequences of the reduced tracer number. With increasing CO2, changes in dissolved oxygen and anthropogenic carbon uptake are very similar across the different models. Thus, while the reduced-tracer models do not explicitly resolve the diversity and internal dynamics of marine ecosystems, we demonstrate that such models are applicable to a broad suite of major biogeochemical concerns, including anthropogenic change. These results are very promising for the further development and application of reduced-tracer biogeochemical models that incorporate "sub-ecosystem-scale" parameterizations.

  9. Model Calculations of Ocean Acidification at the End Cretaceous

    NASA Astrophysics Data System (ADS)

    Tyrrell, T.; Merico, A.; Armstrong McKay, D. I.

    2014-12-01

    Most episodes of ocean acidification (OA) in Earth's past were either too slow or too minor to provide useful lessons for understanding the present. The end-Cretaceous event (66 Mya) is special in this sense, both because of its rapid onset and also because many calcifying species (including 100% of ammonites and >95% of calcareous nannoplankton and planktonic foraminifera) went extinct at this time. We used box models of the ocean carbon cycle to evaluate whether impact-generated OA could feasibly have been responsible for the calcifier mass extinctions. We simulated several proposed consequences of the asteroid impact: (1) vaporisation of gypsum (CaSO4) and carbonate (CaCO3) rocks at the point of impact, producing sulphuric acid and CO2 respectively; (2) generation of NOx by the impact pressure wave and other sources, producing nitric acid; (3) release of CO2 from wildfires, biomass decay and disinterring of fossil organic carbon and hydrocarbons; and (4) ocean stirring leading to introduction into the surface layer of deep water with elevated CO2. We simulated additions over: (A) a few years (e-folding time of 6 months), and also (B) a few days (e-folding time of 10 hours) for SO4 and NOx, as recently proposed by Ohno et al (2014. Nature Geoscience, 7:279-282). Sulphuric acid as a consequence of gypsum vaporisation was found to be the most important acidifying process. Results will also be presented of the amounts of SO4 required to make the surface ocean become extremely undersaturated (Ωcalcite<0.5) for different e-folding times and combinations of processes. These will be compared to estimates in the literature of how much SO4 was actually released.

  10. Bayesian Inference of High-Dimensional Dynamical Ocean Models

    NASA Astrophysics Data System (ADS)

    Lin, J.; Lermusiaux, P. F. J.; Lolla, S. V. T.; Gupta, A.; Haley, P. J., Jr.

    2015-12-01

    This presentation addresses a holistic set of challenges in high-dimension ocean Bayesian nonlinear estimation: i) predict the probability distribution functions (pdfs) of large nonlinear dynamical systems using stochastic partial differential equations (PDEs); ii) assimilate data using Bayes' law with these pdfs; iii) predict the future data that optimally reduce uncertainties; and (iv) rank the known and learn the new model formulations themselves. Overall, we allow the joint inference of the state, equations, geometry, boundary conditions and initial conditions of dynamical models. Examples are provided for time-dependent fluid and ocean flows, including cavity, double-gyre and Strait flows with jets and eddies. The Bayesian model inference, based on limited observations, is illustrated first by the estimation of obstacle shapes and positions in fluid flows. Next, the Bayesian inference of biogeochemical reaction equations and of their states and parameters is presented, illustrating how PDE-based machine learning can rigorously guide the selection and discovery of complex ecosystem models. Finally, the inference of multiscale bottom gravity current dynamics is illustrated, motivated in part by classic overflows and dense water formation sites and their relevance to climate monitoring and dynamics. This is joint work with our MSEAS group at MIT.

  11. Evaluating the ocean biogeochemical components of earth system models using atmospheric potential oxygen (APO) and ocean color data

    NASA Astrophysics Data System (ADS)

    Nevison, C. D.; Manizza, M.; Keeling, R. F.; Kahru, M.; Bopp, L.; Dunne, J.; Tjiputra, J.; Mitchell, B. G.

    2014-06-01

    The observed seasonal cycles in atmospheric potential oxygen (APO) at a range of mid to high latitude surface monitoring sites are compared to those inferred from the output of 6 Earth System Models participating in the fifth phase of the Coupled Model Intercomparison Project (CMIP5). The simulated air-sea O2 fluxes are translated into APO seasonal cycles using a matrix method that takes into account atmospheric transport model (ATM) uncertainty among 13 different ATMs. Half of the ocean biogeochemistry models tested are able to reproduce the observed APO cycles at most sites, to within the current large ATM uncertainty, while the other half generally are not. Net Primary Production (NPP) and net community production (NCP), as estimated from satellite ocean color data, provide additional constraints, albeit more with respect to the seasonal phasing of ocean model productivity than the overall magnitude. The present analysis suggests that, of the tested ocean biogeochemistry models, CESM and GFDL ESM2M are best able to capture the observed APO seasonal cycle at both Northern and Southern Hemisphere sites. In the northern oceans, the comparison to observed APO suggests that most models tend to underestimate NPP or deep ventilation or both.

  12. Closure of the Mongol-Okhotsk Ocean: Insights from seismic tomography and numerical modelling

    NASA Astrophysics Data System (ADS)

    Fritzell, E. H.; Bull, A. L.; Shephard, G. E.

    2016-07-01

    The existence of the Palaeozoic and Mesozoic Mongol-Okhotsk Ocean is evident from the Mongol-Okhotsk suture, which stretches from central Mongolia to the Sea of Okhotsk. A lack of sufficient palaeomagnetic data and an otherwise diffuse suture with an abrupt termination to the west has led to difficulties in reconstructing the history, geometry and closure of this ocean. Both the timing and style of the ocean's closure are unclear and have led to several alternative reconstructions. Closure timing ranges between the Late Jurassic (∼155 Ma) and beginning of the Early Cretaceous (∼120 Ma), and the proposed kinematics include contemporaneous subduction along two opposite margins, subduction along only one margin or with a component of left-lateral shear. In the present study, numerical models of mantle convection are coupled with global plate reconstructions to investigate ambiguities regarding the closure of the Mongol-Okhotsk Ocean. In order to decipher the tectonic history of this enigmatic region, two end-member scenarios of subduction location - either along the present-day northern or the southern margins of the Mongol-Okhotsk Ocean - are imposed as kinematic surface boundary conditions for the past 230 Myrs. Through a comparison to seismic tomography, the results indicate a preferred subduction history along the Siberian margin (relative northern margin) of the Mongol-Okhotsk Ocean. At present-day, the slab remnant is predicted to be located farther west than previously proposed. Furthermore, we find that the subducting slabs in this region generate a hot, dense pile at the same location and with a similar shape as the Perm Anomaly.

  13. Upscalling processes in an ocean-atmosphere multiscale coupled model

    NASA Astrophysics Data System (ADS)

    Masson, S. G.; Berthet, S.; Samson, G.; Crétat, J.; Colas, F.; Echevin, V.; Jullien, S.; Hourdin, C.

    2015-12-01

    This work explores new pathways toward a better representation of the multi-scale physics that drive climate variability. We are analysing the key upscaling processes by which small-scale localized errors have a knock-on effect onto global climate. We focus on the Peru-Chilli coastal upwelling, an area known to hold among the strongest models biases in the Tropics. Our approach is based on the development of a multiscale coupling interface allowing us to couple WRF with the NEMO oceanic model in a configuration including 2-way nested zooms in the oceanic and/or the atmospheric component of the coupled model. Upscalling processes are evidenced and quantified by comparing three 20-year long simulations of a tropical channel (45°S-45°N), which differ by their horizontal resolution: 0.75° everywhere, 0.75°+0.25° zoom in the southeastern Pacific or 0.25° everywhere. This set of three 20-year long simulations was repeated with 3 different sets of parameterizations to assess the robustness of our results. Our results show that adding an embedded zoom over the southeastern Pacific only in the atmosphere cools down the SST along the Peru-Chili coast, which is a clear improvement. This change is associated with a displacement of the low-level cloud cover, which moves closer to the coast cooling further the coastal area SST. Offshore, we observe the opposite effect with a reduction of the cloud cover with higher resolution, which increases solar radiation and warms the SST. Increasing the resolution in the oceanic component show contrasting results according to the different set parameterization used in the experiments. Some experiment shows a coastal cooling as expected, whereas, in other cases, we observe a counterintuitive response with a warming of the coastal SST. Using at the same time an oceanic and an atmospheric zoom mostly combines the results obtained when using the 2-way nesting in only one component of the coupled model. In the best case, we archive by this

  14. Verification of the naval oceanic vertical aerosol model during FIRE

    NASA Technical Reports Server (NTRS)

    Davidson, K. L.; Deleeuw, G.; Gathman, S. G.; Jensen, D. R.

    1990-01-01

    The value of Naval Oceanic Vertical Aerosol Model (NOVAM) is illustrated for estimating the non-uniform and non-logarithmic extinction profiles, based on a severe test involving conditions close to and beyond the limits of applicability of NOVAM. A more comprehensive evaluation of NOVAM from the FIRE data is presented, which includes a clear-air case. For further evaluation more data are required on the vertical structure of the extinction in the marine atmospheric boundary layer (MABL), preferably for different meteorological conditions and in different geographic areas (e.g., ASTEX).

  15. On the Indonesian Throughflow in the OCCAM 1/4 degree ocean model

    NASA Astrophysics Data System (ADS)

    Humphries, U. W.; Webb, D. J.

    2008-07-01

    The Indonesian Throughflow is analysed in two runs of the OCCAM 1/4 degree global ocean model, one using monthly climatological winds and one using ECMWF analysed six-hourly winds for the period 1993 to 1998. The long-term model throughflow agrees with observations and the value predicted by Godfrey's Island Rule. The Island Rule has some skill in predicting the annual signal each year but is poor at predicting year to year and shorter term variations in the total flow, especially in El Niño years. The spectra of transports in individual passages show significant differences between those connecting the region to the Pacific Ocean and those connecting with the Indian Ocean. On investigation we found that changes in the northern transports were strongly correlated with changes in the position of currents in the Celebes Sea and off Halmahera. Vertical profiles of transport are in reasonable agreement with observations but the model overestimates the near surface transport through the Lombok Strait and the dense overflow from the Pacific through the Lifamatola Strait into the deep Banda Sea. In both cases the crude representation of the passages by the model appears responsible. In the north the model shows, as expected, that the largest transport is via the Makassar Strait. However this is less than expected and instead there is significant flow via the Halmahera Sea. If Godfrey's Island Rule is correct and the throughflow is forced by the northward flow between Australia and South America, then the Halmahers Sea route should be important. It is the most southerly route around New Guinea to the Indian Ocean and there is no apparent reason why the flow should go further north in order to pass through the Makassar Strait. The model result thus raises the question of why in reality the Makassar Strait route appears to dominate the throughflow.

  16. On the Indonesian throughflow in the OCCAM 1/4 degree ocean model

    NASA Astrophysics Data System (ADS)

    Humphries, U. W.; Webb, D. J.

    2007-03-01

    The Indonesian Throughflow is analysed in two runs of the OCCAM 1/4 degree global ocean model, one using monthly climatological winds and one using ECMWF analysed six-hourly winds for the period 1993 to 1998. The long-term model throughflow agrees with observations and the value predicted by Godfrey's Island Rule. The Island Rule has some skill in predicting the annual signal each year but is poor at predicting year to year and shorter term variations in the total flow especially in El Nino years. The spectra of transports in individual passages show significant differences between those connecting the region to the Pacific Ocean and those connecting with the Indian Ocean. This implies that different sets of waves are involved in the two regions. Vertical profiles of transport are in reasonable agreement with observations but the model overestimates the near surface transport through the Lombok Strait and the dense overflow from the Pacific through the Lifamatola Strait into the deep Banda Sea. In both cases the crude representation of the passages by the model appears responsible. In the north the model shows, as expected, that the largest transport is via the Makassar Strait. However this is less than expected and instead there is significant flow via the Halmahera Sea. If Godfrey's Island Rule is correct and the throughflow is forced by the northward flow between Australia and South America, then the Halmahers Sea route should be important. It is the most southerly route around New Guinea to the Indian Ocean and there is no apparent reason why the flow should go further north in order to pass through the Makassar Strait. The model result thus raises the question of why in reality the Makassar Strait route appears to dominate the throughflow.

  17. The Fidelity of Ocean Models With Explicit Eddies (Chapter 17)

    SciTech Connect

    McClean, J; Jayne, S; Maltrud, M; Ivanova, D

    2007-08-01

    Current practices within the oceanographic community have been reviewed with regard to the use of metrics to assess the realism of the upper-ocean circulation, ventilation processes diagnosed by time-evolving mixed layer depth and mode water formation, and eddy heat fluxes in large-scale fine resolution ocean model simulations. We have striven to understand the fidelity of these simulations in the context of their potential use in future fine-resolution coupled climate system studies. A variety of methodologies are used to assess the veracity of the numerical simulations. Sea surface height variability and the location of western boundary current paths from altimetry have been used routinely as basic indicators of fine-resolution model performance. Drifters and floats have also been used to provide pseudo-Eulerian measures of the mean and variability of surface and sub-surface flows, while statistical comparisons of observed and simulated means have been carried out using James tests. Probability density functions have been used to assess the Gaussian nature of the observed and simulated flows. Length and time scales have been calculated in both Eulerian and Lagrangian frameworks from altimetry and drifters, respectively. Concise measures of multiple model performance have been obtained from Taylor diagrams. The time-evolution of the mixed layer depth at monitoring stations has been compared with simulated time series. Finally, eddy heat fluxes are compared to climatological inferences.

  18. Assimilating ocean tide determined data into global tidal models

    NASA Astrophysics Data System (ADS)

    Zahel, W.

    1995-01-01

    A data assimilation procedure, which has successfully been applied to fictive and realistic scenarios, is applied to a 1 °-model making use of an effective iterative method for the solution of the minimization problem. Two sets of ocean tide determined data are used for the purpose of assimilation, the more extensive one mainly comprising pelagic together with some coastal sea surface elevation data, and the other one consisting of loading gravity data. The computed O1 and M2 global tidal oscillation systems, namely the fields of tidal elevation and loading gravity, are compared with numerous additional pelagic and coastal elevation data and with a selected number of proper gravity data, respectively. The assimilation of the two sets of data leads to an enormous reduction of the errors of the model results in all oceans. Assimilating this altogether still restricted number of data, allows studying the generation of realistic tidal oscillation phenomena by individual data and comparing these data effects with those having been obtained by previous data assimilation experiments using a model with coarser grid spacing. The field of dynamical residuals resulting from data assimilation reflects the far reaching influence of the data, and it is shown that the spatially integrated work done by the residuals contributes to the in all reduced rate of dissipation in the tidal power balance.

  19. Verification of a numerical ocean model of the Arabian Sea

    NASA Astrophysics Data System (ADS)

    Simmons, Ray C.; Luther, Mark E.; O'Brien, James J.; Legler, David M.

    1988-12-01

    A case study evaluating the predictive capability of an upper layer circulation model of the northwest Indian Ocean is presented. The model is a nonlinear, reduced gravity model incorporating realistic boundary geometry and is forced by observed winds. Model results for the fall of 1985 are compared with and evaluated against U.S. Navy bathythermograph and NOAA satellite data collected during August-November 1985. An assessment is made of the model's ability to simulate correctly the circulation structure. Ship wind observations are converted to wind stress for model forcing by a procedure developed by Legler and Navon (1988). The model is only moderately successful in reproducing the structure of the large, rather homogeneous pool of water located off the Arabian Peninsula in September. However, the model behaves remarkably well in the dynamically active region around Socotra. Major fronts and eddies frequently observed in the region during the transition period between the southwest and the northeast monsoon appear in the 1985 model results and compare well, both temporally and spatially, with the observational data. Thus given accurate wind information, the model appears highly effective in dynamically active regions and demonstrates potential as a useful prognostic tool for evaluation of the Arabian Sea when real time winds become available.

  20. Preliminary ice shelf-ocean simulation results from idealized standalone-ocean and coupled model intercomparison projects (MIPs)

    NASA Astrophysics Data System (ADS)

    Asay-Davis, Xylar; Martin, Daniel

    2016-04-01

    The second Ice Shelf-Ocean MIP (ISOMIP+) and the first Marine Ice Sheet-Ocean MIP (MISOMIP1) prescribe a set of idealized experiments for ocean models with ice-shelf cavities and coupled ice sheet-ocean models, respectively. ISOMIP+ and MISOMIP1 were designed together with the third Marine Ice Sheet MIP (MISMIP+) with three main goals, namely that the MIPs should provide: a controlled forum for researchers to compare their model results with those from other models during model development. a path for testing components in the process of developing coupled ice sheet-ocean models. a basic setup from which a large variety of parameter and process studies can usefully be performed. The experimental design for the three MIPs is currently under review in Geoscientific Model Development (Asay-Davis et al. 2015, doi:10.5194/gmdd-8-9859-2015). We present preliminary results from ISOMIP+ and MISOMIP1 experiments using several ocean-only and coupled ice sheet-ocean models. Among ocean models, we show that differences in model behavior are significant enough that similar results can only be achieved by tuning model parameters (e.g. boundary-layer transfer coefficients, drag coefficients, vertical mixing parameterizations) for each models. This tuning is constrained by a desired mean melt rate in quasi-steady state under specified forcing conditions, akin to how models would be tuned based on observations for non-idealized simulations. We also present a number of parameter studies based the MIP experiments. Again, using several models, we show that melt rates respond sub-linearly to both changes in the square root of the drag coefficient and the heat-transfer coefficient, and that melting is relatively insensitive to horizontal-mixing coefficients (perhaps because the resolution is sufficient to permit eddies) but more sensitive to vertical-mixing coefficients. We show that the choice of the equation of state (linear or nonlinear) does not have a significant impact as long as

  1. Ice-ocean-ecosystem operational model of the Baltic Sea

    NASA Astrophysics Data System (ADS)

    Janecki, M.; Dzierzbicka-Glowacka, L.; Jakacki, J.; Nowicki, A.

    2012-04-01

    3D-CEMBS is a fully coupled model adopted for the Baltic Sea and have been developed within the grant, wchich is supported by the Polish State Committee of Scientific Reasearch. The model is based on CESM1.0 (Community Earth System Model), in our configuration it consists of two active components (ocean and ice) driven by central coupler (CPL7). Ocean (POP version 2.1) and ice models (CICE model, version 4.0) are forced by atmospheric and land data models. Atmospheric data sets are provided by ICM-UM model from University of Warsaw. Additionally land model provides runoff of the Baltic Sea (currently 78 rivers). Ecosystem model is based on an intermediate complexity marine ecosystem model for the global domain (J.K. Moore et. al., 2002) and consists of 11 main components: zooplankton, small phytoplankton, diatoms, cyanobacteria, two detrital classes, dissolved oxygen and the nutrients nitrate, ammonium, phosphate and silicate. The model is configured at two horizontal resolutions, approximately 9km and 2km (1/12° and 1/48° respectively). The model bathymetry is represented as 21 vertical levels and the thickness of the first four layers were chosen to be five metres. 3D-CEMBS model grid is based on stereographic coordinates, but equator of these coordinates is in the centre of the Baltic Sea (rotated stereographic coordinates) and we can assume that shape of the cells are square and they are identical. Currently model works in a operational state. The model creates 48-hour forecasts every 6 hours (or when new atmospheric dataset is available). Prognostic variables such as temperature, salinity, ice cover, currents, sea surface height and phytoplankton concentration are presented online on a the website and are available for registered users. Also time series for any location are accessible. This work was carried out in support of grant No NN305 111636 and No NN306 353239 - the Polish state Committee of Scientific Research. The partial support for this study was

  2. Coupled ice-flow/ocean circulation modeling in the Amundsen Sea Embayment using ISSM and MITgcm.

    NASA Astrophysics Data System (ADS)

    Larour, E. Y.; Menemenlis, D.; Schodlok, M.

    2014-12-01

    the West Antarctic Ice Sheet is thought to be prone to marine instability in which prolonged grounding line retreat could occur due to inland downwards sloping bedrocks. However, this instability is difficult to model in part due to the absence of good parameterizations for melt-rates under ice-shelves, in particular near or at the grounding-line, where a complex interplay between butressing, melt-rate, water-pressure and internal stresses in the ice develops. In order to simulate such melt rates accurately, ice-sheet models need to be fully coupled to ocean models, in order to capture the feedback mechanisms between heat-flux at the ice/ocean interface and cavity shape driven by grounding-line retreat.Here, we show an example of such a coupling between the Ice Sheet System Model (ISSM) and the MIT General Circulation Model (MITgcm). The goal is to run sensitivity studies of the evolution of Pine Island Glacier in West Antarctica. We quantify the impact of feedbacks between both systems by running short transients (20-100 years) of the coupled ice-sheet flow/ocean circulation model. We vary inputs such as far-field temperature of the Circumpolar Deep-Water, surface temperature of the Amundsen Sea Embayment, and far-field surface ice-flow velocity. Preliminary insights into the variability of the system are presented, as well as quantified impacts of variations in model inputs.This work was performed at the California Institute of Technology's Jet Propulsion Laboratory undera contract with the National Aeronautics and Space Administration's Cryosphere Science Program.

  3. World Ocean Circulation Experiment

    NASA Technical Reports Server (NTRS)

    Clarke, R. Allyn

    1992-01-01

    The oceans are an equal partner with the atmosphere in the global climate system. The World Ocean Circulation Experiment is presently being implemented to improve ocean models that are useful for climate prediction both by encouraging more model development but more importantly by providing quality data sets that can be used to force or to validate such models. WOCE is the first oceanographic experiment that plans to generate and to use multiparameter global ocean data sets. In order for WOCE to succeed, oceanographers must establish and learn to use more effective methods of assembling, quality controlling, manipulating and distributing oceanographic data.

  4. Modeling of Perturbations in Mid-Ocean Hydrothermal Systems

    NASA Astrophysics Data System (ADS)

    Singh, S.; Lowell, R. P.

    2013-12-01

    Mid-ocean ridge hydrothermal systems are complex fluid circulation systems straddling the locations of formation of oceanic crust. Due to the dynamic nature of the crust building process, these systems are episodically subject to magmatic and seismic perturbations. Magma may be emplaced deep or shallow in the oceanic crust thereby changing the thermal structure and permeability of the system. Such events would enhance hydrothermal venting resulting in an increase in vent temperature and heat output along with a decrease in vent salinity in a phase separating system. Event plumes, which may be associated with dike intrusions into the shallow crust, are an important class of such perturbations. In this case, the formation of low salinity vapor may add to the thermal buoyancy flux and allow the plume to rise rapidly to a considerable height above the seafloor. Additionally, seismic or tectonic disturbances may occur both deep and shallow in the crust, changing the fluid-flow structure in the system. Upon knowledge of a major magmatic or seismotectonic event, temporary surveillance at the respective mid ocean ridge site is often increased as a result of rapid response cruises. One of the most common observations made after such events is the temperature of vent fluids, which is then correlated to time of observed activity and used to estimate the residence time of fluids in the system. However, our numerical results indicate that for deep-seated perturbations, surface salinity may show quicker response than temperature. This result serves as our motivation to seek better understanding of propagation mechanism of perturbations through hydrothermal systems. We construct analytical models for fluid flow, heat and salt transfer in both single cracks and through porous media to investigate how perturbations affect both heat and salt transfer to the surface. Our preliminary results for simplified fluid circulation systems tend to support the results from numerical modeling

  5. Radiative transfer theory applied to ocean bottom modeling.

    PubMed

    Quijano, Jorge E; Zurk, Lisa M

    2009-10-01

    Research on the propagation of acoustic waves in the ocean bottom sediment is of interest for active sonar applications such as target detection and remote sensing. The interaction of acoustic energy with the sea floor sublayers is usually modeled with techniques based on the full solution of the wave equation, which sometimes leads to mathematically intractable problems. An alternative way to model wave propagation in layered media containing random scatterers is the radiative transfer (RT) formulation, which is a well established technique in the electromagnetics community and is based on the principle of conservation of energy. In this paper, the RT equation is used to model the backscattering of acoustic energy from a layered elastic bottom sediment containing distributions of independent scatterers due to a constant single frequency excitation in the water column. It is shown that the RT formulation provides insight into the physical phenomena of scattering and conversion of energy between waves of different polarizations.

  6. Improvement in Geoid Models for Ocean Circulation Studies

    NASA Technical Reports Server (NTRS)

    Tapley, Byron D.; Chambers, Don P.; Poole, Steve; Ries, John c.

    2003-01-01

    At wavelengths of 500 km and longer, the GRACE GGM01 Model produces a significantly better marine geoid than any previous model. This conclusion follows from evaluating the geostrophic currents determined by combining the model with a mean sea surface from altimetry. The agreement with currents computed from a traditional hydrographic map is very close, which suggests that one of the primary missions of the TOPEX/POSEIDON mission, to determine the absolute dynamic ocean topography, may soon be met. This solution has been made available to the public at http://www.csr.utexs.edu/grace/gravity. The results reported in this paper have been presented at the 2003 EGS-AGU-EUG Joint Assembly. Two articles are currently being prepared for Geophysical Research Letters to summarize these results.

  7. A high-resolution ocean and sea-ice modelling system for the Arctic and North Atlantic Oceans

    NASA Astrophysics Data System (ADS)

    Dupont, F.; Higginson, S.; Bourdallé-Badie, R.; Lu, Y.; Roy, F.; Smith, G. C.; Lemieux, J.-F.; Garric, G.; Davidson, F.

    2015-01-01

    As part of the CONCEPTS (Canadian Operational Network of Coupled Environmental PredicTion Systems) initiative, The Government of Canada is developing a high resolution (1/12°) ice-ocean regional model covering the North Atlantic and the Arctic oceans. The objective is to provide Canada with short-term ice-ocean predictions and hazard warnings in ice infested regions. To evaluate the modelling component (as opposed to the analysis - or data-assimilation - component), a series of hindcasts for the period 2003-2009 is carried out, forced at the surface by the Canadian Global Re-Forecasts. These hindcasts test how the model represent upper ocean characteristics and ice cover. Each hindcast implements a new aspect of the modelling or the ice-ocean coupling. Notably, the coupling to the multi-category ice model CICE is tested. The hindcast solutions are then assessed using a validation package under development, including in-situ and satellite ice and ocean observations. The conclusions are: (1) the model reproduces reasonably well the time mean, variance and skewness of sea surface height. (2) The model biases in temperature and salinity show that while the mean properties follow expectations, the Pacific Water signature in the Beaufort Sea is weaker than observed. (3) However, the modelled freshwater content of the Arctic agrees well with observational estimates. (4) The distribution and volume of the sea ice is shown to be improved in the latest hindcast thanks to modifications to the drag coefficients and to some degree as well to the ice thickness distribution available in CICE. (5) On the other hand, the model overestimates the ice drift and ice thickness in the Beaufort Gyre.

  8. The CAFE model: A net production model for global ocean phytoplankton

    NASA Astrophysics Data System (ADS)

    Silsbe, Greg M.; Behrenfeld, Michael J.; Halsey, Kimberly H.; Milligan, Allen J.; Westberry, Toby K.

    2016-12-01

    The Carbon, Absorption, and Fluorescence Euphotic-resolving (CAFE) net primary production model is an adaptable framework for advancing global ocean productivity assessments by exploiting state-of-the-art satellite ocean color analyses and addressing key physiological and ecological attributes of phytoplankton. Here we present the first implementation of the CAFE model that incorporates inherent optical properties derived from ocean color measurements into a mechanistic and accurate model of phytoplankton growth rates (μ) and net phytoplankton production (NPP). The CAFE model calculates NPP as the product of energy absorption (QPAR), and the efficiency (ϕμ) by which absorbed energy is converted into carbon biomass (CPhyto), while μ is calculated as NPP normalized to CPhyto. The CAFE model performance is evaluated alongside 21 other NPP models against a spatially robust and globally representative set of direct NPP measurements. This analysis demonstrates that the CAFE model explains the greatest amount of variance and has the lowest model bias relative to other NPP models analyzed with this data set. Global oceanic NPP from the CAFE model (52 Pg C m-2 yr-1) and mean division rates (0.34 day-1) are derived from climatological satellite data (2002-2014). This manuscript discusses and validates individual CAFE model parameters (e.g., QPAR and ϕμ), provides detailed sensitivity analyses, and compares the CAFE model results and parameterization to other widely cited models.

  9. Manganese in the west Atlantic Ocean in the context of the first global ocean circulation model of manganese

    NASA Astrophysics Data System (ADS)

    van Hulten, Marco; Middag, Rob; Dutay, Jean-Claude; de Baar, Hein; Roy-Barman, Matthieu; Gehlen, Marion; Tagliabue, Alessandro; Sterl, Andreas

    2017-03-01

    Dissolved manganese (Mn) is a biologically essential element. Moreover, its oxidised form is involved in removing itself and several other trace elements from ocean waters. Here we report the longest thus far (17 500 km length) full-depth ocean section of dissolved Mn in the west Atlantic Ocean, comprising 1320 data values of high accuracy. This is the GA02 transect that is part of the GEOTRACES programme, which aims to understand trace element distributions. The goal of this study is to combine these new observations with new, state-of-the-art, modelling to give a first assessment of the main sources and redistribution of Mn throughout the ocean. To this end, we simulate the distribution of dissolved Mn using a global-scale circulation model. This first model includes simple parameterisations to account for the sources, processes and sinks of Mn in the ocean. Oxidation and (photo)reduction, aggregation and settling, as well as biological uptake and remineralisation by plankton are included in the model. Our model provides, together with the observations, the following insights: - The high surface concentrations of manganese are caused by the combination of photoreduction and sources contributing to the upper ocean. The most important sources are sediments, dust, and, more locally, rivers. - Observations and model simulations suggest that surface Mn in the Atlantic Ocean moves downwards into the southward-flowing North Atlantic Deep Water (NADW), but because of strong removal rates there is no elevated concentration of Mn visible any more in the NADW south of 40° N. - The model predicts lower dissolved Mn in surface waters of the Pacific Ocean than the observed concentrations. The intense oxygen minimum zone (OMZ) in subsurface waters is deemed to be a major source of dissolved Mn also mixing upwards into surface waters, but the OMZ is not well represented by the model. Improved high-resolution simulation of the OMZ may solve this problem. - There is a mainly

  10. Modeling the Ocean Tide for Tidal Power Generation Applications

    NASA Astrophysics Data System (ADS)

    Kawase, M.; Gedney, M.

    2014-12-01

    Recent years have seen renewed interest in the ocean tide as a source of energy for electrical power generation. Unlike in the 1960s, when the tidal barrage was the predominant method of power extraction considered and implemented, the current methodology favors operation of a free-stream turbine or an array of them in strong tidal currents. As tidal power generation moves from pilot-scale projects to actual array implementations, numerical modeling of tidal currents is expected to play an increasing role in site selection, resource assessment, array design, and environmental impact assessment. In this presentation, a simple, coupled ocean/estuary model designed for research into fundamental aspects of tidal power generation is described. The model consists of a Pacific Ocean-size rectangular basin and a connected fjord-like embayment with dimensions similar to that of Puget Sound, Washington, one of the potential power generation sites in the United States. The model is forced by an idealized lunar tide-generating potential. The study focuses on the energetics of a tidal system including tidal power extraction at both global and regional scales. The hyperbolic nature of the governing shallow water equations means consequence of tidal power extraction cannot be limited to the local waters, but is global in extent. Modeling power extraction with a regional model with standard boundary conditions introduces uncertainties of 3 ~ 25% in the power extraction estimate depending on the level of extraction. Power extraction in the model has a well-defined maximum (~800 MW in a standard case) that is in agreement with previous theoretical studies. Natural energy dissipation and tidal power extraction strongly interact; for a turbine array of a given capacity, the higher the level of natural dissipation the lower the power the array can extract. Conversely, power extraction leads to a decrease in the level of natural dissipation (Figure) as well as the tidal range and the

  11. Exponential order statistic models of software reliability growth

    NASA Technical Reports Server (NTRS)

    Miller, D. R.

    1985-01-01

    Failure times of a software reliabilty growth process are modeled as order statistics of independent, nonidentically distributed exponential random variables. The Jelinsky-Moranda, Goel-Okumoto, Littlewood, Musa-Okumoto Logarithmic, and Power Law models are all special cases of Exponential Order Statistic Models, but there are many additional examples also. Various characterizations, properties and examples of this class of models are developed and presented.

  12. Exponential order statistic models of software reliability growth

    NASA Technical Reports Server (NTRS)

    Miller, D. R.

    1986-01-01

    Failure times of a software reliability growth process are modeled as order statistics of independent, nonidentically distributed exponential random variables. The Jelinsky-Moranda, Goel-Okumoto, Littlewood, Musa-Okumoto Logarithmic, and Power Law models are all special cases of Exponential Order Statistic Models, but there are many additional examples also. Various characterizations, properties and examples of this class of models are developed and presented.

  13. 77 FR 13606 - Ocean Transportation Intermediary License; Rescission of Order of Revocation

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-07

    ... From the Federal Register Online via the Government Publishing Office FEDERAL MARITIME COMMISSION... the Order revoking the following license is being rescinded by the Federal Maritime Commission... Number: 021014N. Name: Magic Transport, Inc. Address: Pepsi Industrial Park, PR-2, KM 19.5, Interior...

  14. 76 FR 555 - Ocean Transportation Intermediary License; Rescission of Order of Revocation

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-05

    ... pursuant to section 19 of the Shipping Act of 1984 (46 U.S.C. chapter 409) and the regulations of the... 33166. Order Published: FR: 11/26/10 (Volume 75, No. 227 Pg. 72825). Tanga S. FitzGibbon,...

  15. Anisotropic mesoscale eddy transport in ocean general circulation models

    NASA Astrophysics Data System (ADS)

    Reckinger, Scott; Fox-Kemper, Baylor; Bachman, Scott; Bryan, Frank; Dennis, John; Danabasoglu, Gokhan

    2014-11-01

    In modern climate models, the effects of oceanic mesoscale eddies are introduced by relating subgrid eddy fluxes to the resolved gradients of buoyancy or other tracers, where the proportionality is, in general, governed by an eddy transport tensor. The symmetric part of the tensor, which represents the diffusive effects of mesoscale eddies, is universally treated isotropically. However, the diffusive processes that the parameterization approximates, such as shear dispersion and potential vorticity barriers, typically have strongly anisotropic characteristics. Generalizing the eddy diffusivity tensor for anisotropy extends the number of parameters from one to three: major diffusivity, minor diffusivity, and alignment. The Community Earth System Model (CESM) with the anisotropic eddy parameterization is used to test various choices for the parameters, which are motivated by observations and the eddy transport tensor diagnosed from high resolution simulations. Simply setting the ratio of major to minor diffusivities to a value of five globally, while aligning the major axis along the flow direction, improves biogeochemical tracer ventilation and reduces temperature and salinity biases. These effects can be improved by parameterizing the oceanic anisotropic transport mechanisms.

  16. Bayesian Analysis of Order-Statistics Models for Ranking Data.

    ERIC Educational Resources Information Center

    Yu, Philip L. H.

    2000-01-01

    Studied the order-statistics models, extending the usual normal order-statistics model into one in which the underlying random variables followed a multivariate normal distribution. Used a Bayesian approach and the Gibbs sampling technique. Applied the proposed method to analyze presidential election data from the American Psychological…

  17. Comparison of a Coupled Ocean-Atmosphere Model with and without Oceanic Eddy-Induced Advection. Part I: Ocean Spinup and Control Integrations.

    NASA Astrophysics Data System (ADS)

    Hirst, Anthony C.; O'Farrell, Siobhan P.; Gordon, Hal B.

    2000-01-01

    The Gent and McWilliams (GM) parameterization for large-scale water transport caused by mesoscale oceanic eddies is introduced into the oceanic component of the Commonwealth Scientific and Industrial Research Organisation global coupled ocean-atmosphere model. Parallel simulations with and without the GM scheme are performed to examine the effect of this parameterization on the model behavior for integrations lasting several centuries under conditions of constant atmospheric CO2. The solution of the version with GM shows several significant improvements over that of the earlier version. First, the generally beneficial effects of the GM scheme found previously in studies of stand-alone ocean models, including more realistic deep water properties, increased stratification, reduced high-latitude convection, elimination of fictitious horizontal diffusive heat transport, and more realistic surface fluxes in some regions, are all maintained during the coupled integration. These improvements are especially pronounced in the high-latitude Southern Ocean. Second, the magnitude of flux adjustment is reduced in the GM version, mainly because of smaller surface fluxes at high southern latitudes in the GM ocean spinup. Third, the GM version displays markedly reduced climate drift in comparison to the earlier version. Analysis in the present study verifies previous indications that changes in the pattern of convective heat flux are central to the drift in the earlier version, supporting the view that reduced convective behavior in the GM version contributes to the reduction in drift. Based on the satisfactory behavior of the GM model version, the GM coupled integration is continued for a full 1000 yr. Key aspects of the model behavior during this longer period are also presented. Interannual variability of surface air temperature in the two model versions is briefly examined using some simple measures of magnitude. The variability differs between the two versions regionally, but

  18. Ocean acidification in the Meso- vs. Cenozoic: lessons from modeling about the geological expression of paleo-ocean acidification

    NASA Astrophysics Data System (ADS)

    Greene, S. E.; Ridgwell, A.; Kirtland Turner, S.

    2015-12-01

    Rapid climatic and biotic events putatively associated with ocean acidification are scattered throughout the Meso-Cenozoic. Many of these rapid perturbations, variably referred to as hyperthermals (Paleogene) and oceanic anoxic events or mass extinction events (Mesozoic), share a number of characteristic features, including some combination of negative carbon isotopic excursion, global warming, and a rise in atmospheric CO2 concentration. Comparisons between ocean acidification events over the last ~250 Ma are, however, problematic because the types of marine geological archives and carbon reservoirs that can be interrogated are fundamentally different for early Mesozoic vs. late Mesozoic-Cenozoic events. Many Mesozoic events are known primarily or exclusively from geological outcrops of relatively shallow water deposits, whereas the more recent Paleogene hyperthermal events have been chiefly identified from deep sea records. In addition, these earlier events are superimposed on an ocean with a fundamentally different carbonate buffering capacity, as calcifying plankton (which created the deep-sea carbonate sink) originate in the mid-Mesozoic. Here, we use both Earth system modeling and reaction transport sediment modeling to explore the ways in which comparable ocean acidification-inducing climate perturbations might manifest in the Mesozoic vs. the Cenozoic geological record. We examine the role of the deep-sea carbonate sink in the expression of ocean acidification, as well as the spatial heterogeneity of surface ocean pH and carbonate saturation state. These results critically inform interpretations of ocean acidification prior to the mid-Mesozoic advent of calcifying plankton and expectations about the recording of these events in geological outcrop.

  19. Numerical Modeling of Gravity, Geoid, and the Thermal Structure of Oceanic Lithosphere

    NASA Astrophysics Data System (ADS)

    Davis, D.; Grose, C. J.

    2010-12-01

    In order to better understand links between the thermal and density structure of oceanic lithosphere with its surface manifestations, we implement numerical techniques to predict both the thermal structure of oceanic lithosphere and the consequent gravity field and geoid height. The two principal problems of our potential field numerical algorithm are the transposition of density data in two-dimensional Cartesian space into a three-dimensional spherical shell model, and accurately quantifying deformation in the Cartesian grid associated with contraction and isostatic adjustment. Using this model we investigate anomalies in gravity and the geoid due to density heterogeneities associated with varying properties and boundary conditions of the oceanic lithosphere. Such sources of thermal and density structure include the impact of variable heat transport properties, lattice preferred orientation, mantle potential temperature and adiabate, plate thickness, and the composite mineral assemblage. Variable transport properties are known to result in substantial deviations in the geotherm relative to that expected from models with constant thermal parameters. Since the near-surface lithosphere is cooler, the impact on geoid height should be smaller and this is important for constraining the effective diffusivity of the lithosphere. In addition, composite mineralogy is important due to phase changes. In particular, the spinel-garnet transition rapidly elevates in lithosphere around ages of 20 to 40 Mya. Such a density anomaly is likely to be observable in the geoid height, and this may account for unexplained features of geoid slope at young ages.

  20. The role of local atmospheric forcing on the modulation of the ocean mixed layer depth in reanalyses and a coupled single column ocean model

    NASA Astrophysics Data System (ADS)

    Pookkandy, Byju; Dommenget, Dietmar; Klingaman, Nicholas; Wales, Scott; Chung, Christine; Frauen, Claudia; Wolff, Holger

    2016-11-01

    The role of local atmospheric forcing on the ocean mixed layer depth (MLD) over the global oceans is studied using ocean reanalysis data products and a single-column ocean model coupled to an atmospheric general circulation model. The focus of this study is on how the annual mean and the seasonal cycle of the MLD relate to various forcing characteristics in different parts of the world's oceans, and how anomalous variations in the monthly mean MLD relate to anomalous atmospheric forcings. By analysing both ocean reanalysis data and the single-column ocean model, regions with different dominant forcings and different mean and variability characteristics of the MLD can be identified. Many of the global oceans' MLD characteristics appear to be directly linked to the different atmospheric forcing characteristics at different locations. Here, heating and wind-stress are identified as the main drivers; in some, mostly coastal, regions the atmospheric salinity forcing also contributes. The annual mean MLD is more closely related to the annual mean wind-stress and the MLD seasonality is more closely related to the seasonality in heating. The single-column ocean model, however, also points out that the MLD characteristics over most global ocean regions, and in particular in the tropics and subtropics, cannot be maintained by local atmospheric forcings only, but are also a result of ocean dynamics that are not simulated in a single-column ocean model. Thus, lateral ocean dynamics are essential in correctly simulating observed MLD.

  1. Technical Report Series on Global Modeling and Data Assimilation. Volume 22; A Coupled Ocean-Atmosphere Radiative Model for Global Ocean Biogeochemical Models

    NASA Technical Reports Server (NTRS)

    Gregg, Watson W.; Suarez, Max J. (Editor)

    2002-01-01

    An ocean-atmosphere radiative model (OARM) evaluates irradiance availability and quality in the water column to support phytoplankton growth and drive ocean thermodynamics. An atmospheric component incorporates spectral and directional effects of clear and cloudy skies as a function of atmospheric optical constituents, and spectral reflectance across the air-sea interface. An oceanic component evaluates the propagation of spectral and directional irradiance through the water column as a function of water, five phytoplankton groups, and chromophoric dissolved organic matter. It tracks the direct and diffuse streams from the atmospheric component, and a third stream, upwelling diffuse irradiance. The atmospheric component of OARM was compared to data sources at the ocean surface with a coefficient of determination (r2) of 0.97 and a root mean square of 12.1%.

  2. Model Development Highlight for 1984: The GLA Fourth Order GCM

    NASA Technical Reports Server (NTRS)

    Pfaendtner, J.

    1985-01-01

    A number of improvements have been made to the GLA Fourth Order General Circulation Model and its associated run procedures during the past year. Major development efforts have been carried out in the following areas: (1) model resolution; (2) boundary fields and topography; (3) post-processing of model results on CYBER computer; and (4) model source code.

  3. A comparison of zero-order, first-order, and monod biotransformation models

    USGS Publications Warehouse

    Bekins, B.A.; Warren, E.; Godsy, E.M.

    1998-01-01

    Under some conditions, a first-order kinetic model is a poor representation of biodegradation in contaminated aquifers. Although it is well known that the assumption of first-order kinetics is valid only when substrate concentration, S, is much less than the half-saturation constant, K(s), this assumption is often made without verification of this condition. We present a formal error analysis showing that the relative error in the first-order approximation is S/K(S) and in the zero-order approximation the error is K(s)/S. We then examine the problems that arise when the first-order approximation is used outside the range for which it is valid. A series of numerical simulations comparing results of first- and zero-order rate approximations to Monod kinetics for a real data set illustrates that if concentrations observed in the field are higher than K(s), it may better to model degradation using a zero-order rate expression. Compared with Monod kinetics, extrapolation of a first-order rate to lower concentrations under-predicts the biotransformation potential, while extrapolation to higher concentrations may grossly over-predict the transformation rate. A summary of solubilities and Monod parameters for aerobic benzene, toluene, and xylene (BTX) degradation shows that the a priori assumption of first-order degradation kinetics at sites contaminated with these compounds is not valid. In particular, out of six published values of KS for toluene, only one is greater than 2 mg/L, indicating that when toluene is present in concentrations greater than about a part per million, the assumption of first-order kinetics may be invalid. Finally, we apply an existing analytical solution for steady-state one-dimensional advective transport with Monod degradation kinetics to a field data set.A formal error analysis is presented showing that the relative error in the first-order approximation is S/KS and in the zero-order approximation the error is KS/S where S is the substrate

  4. Modeling Higher-Order Correlations within Cortical Microcolumns

    PubMed Central

    Köster, Urs; Sohl-Dickstein, Jascha; Gray, Charles M.; Olshausen, Bruno A.

    2014-01-01

    We statistically characterize the population spiking activity obtained from simultaneous recordings of neurons across all layers of a cortical microcolumn. Three types of models are compared: an Ising model which captures pairwise correlations between units, a Restricted Boltzmann Machine (RBM) which allows for modeling of higher-order correlations, and a semi-Restricted Boltzmann Machine which is a combination of Ising and RBM models. Model parameters were estimated in a fast and efficient manner using minimum probability flow, and log likelihoods were compared using annealed importance sampling. The higher-order models reveal localized activity patterns which reflect the laminar organization of neurons within a cortical column. The higher-order models also outperformed the Ising model in log-likelihood: On populations of 20 cells, the RBM had 10% higher log-likelihood (relative to an independent model) than a pairwise model, increasing to 45% gain in a larger network with 100 spatiotemporal elements, consisting of 10 neurons over 10 time steps. We further removed the need to model stimulus-induced correlations by incorporating a peri-stimulus time histogram term, in which case the higher order models continued to perform best. These results demonstrate the importance of higher-order interactions to describe the structure of correlated activity in cortical networks. Boltzmann Machines with hidden units provide a succinct and effective way to capture these dependencies without increasing the difficulty of model estimation and evaluation. PMID:24991969

  5. Modeling higher-order correlations within cortical microcolumns.

    PubMed

    Köster, Urs; Sohl-Dickstein, Jascha; Gray, Charles M; Olshausen, Bruno A

    2014-07-01

    We statistically characterize the population spiking activity obtained from simultaneous recordings of neurons across all layers of a cortical microcolumn. Three types of models are compared: an Ising model which captures pairwise correlations between units, a Restricted Boltzmann Machine (RBM) which allows for modeling of higher-order correlations, and a semi-Restricted Boltzmann Machine which is a combination of Ising and RBM models. Model parameters were estimated in a fast and efficient manner using minimum probability flow, and log likelihoods were compared using annealed importance sampling. The higher-order models reveal localized activity patterns which reflect the laminar organization of neurons within a cortical column. The higher-order models also outperformed the Ising model in log-likelihood: On populations of 20 cells, the RBM had 10% higher log-likelihood (relative to an independent model) than a pairwise model, increasing to 45% gain in a larger network with 100 spatiotemporal elements, consisting of 10 neurons over 10 time steps. We further removed the need to model stimulus-induced correlations by incorporating a peri-stimulus time histogram term, in which case the higher order models continued to perform best. These results demonstrate the importance of higher-order interactions to describe the structure of correlated activity in cortical networks. Boltzmann Machines with hidden units provide a succinct and effective way to capture these dependencies without increasing the difficulty of model estimation and evaluation.

  6. Adaptive tracking for complex systems using reduced-order models

    NASA Technical Reports Server (NTRS)

    Carnigan, Craig R.

    1990-01-01

    Reduced-order models are considered in the context of parameter adaptive controllers for tracking workspace trajectories. A dual-arm manipulation task is used to illustrate the methodology and provide simulation results. A parameter adaptive controller is designed to track a payload trajectory using a four-parameter model instead of the full-order, nine-parameter model. Several simulations with different payload-to-arm mass ratios are used to illustrate the capabilities of the reduced-order model in tracking the desired trajectory.

  7. Adaptive tracking for complex systems using reduced-order models

    NASA Technical Reports Server (NTRS)

    Carignan, Craig R.

    1990-01-01

    Reduced-order models are considered in the context of parameter adaptive controllers for tracking workspace trajectories. A dual-arm manipulation task is used to illustrate the methodology and provide simulation results. A parameter adaptive controller is designed to track the desired position trajectory of a payload using a four-parameter model instead of a full-order, nine-parameter model. Several simulations with different payload-to-arm mass ratios are used to illustrate the capabilities of the reduced-order model in tracking the desired trajectory.

  8. Stirring effects in models of oceanic plankton populations

    NASA Astrophysics Data System (ADS)

    Neufeld, Zoltan

    2012-09-01

    We present an overview and extend previous results on the effects of large scale oceanic transport processes on plankton population dynamics, considering different types of ecosystem models. We find that increasing stirring rate in an environment where the carrying capacity is non-uniformly distributed leads to an overall decrease of the effective carrying capacity of the system. This may lead to sharp regime shifts induced by stirring in systems with multiple steady states. In prey-predator type systems, stirring leads to resonant response of the population dynamics to fluctuations enhancing the spatial variability—patchiness—in a certain range of stirring rates. Oscillatory population models produce strongly heterogeneous patchy distribution of plankton blooms when the stirring is weak, while strong stirring may either synchronise the oscillatory dynamics, when the inhomogeneity is relatively weak, or suppress oscillations completely (oscillator death) by reducing the effective carrying capacity below the bifurcation point.

  9. Stirring effects in models of oceanic plankton populations.

    PubMed

    Neufeld, Zoltan

    2012-09-01

    We present an overview and extend previous results on the effects of large scale oceanic transport processes on plankton population dynamics, considering different types of ecosystem models. We find that increasing stirring rate in an environment where the carrying capacity is non-uniformly distributed leads to an overall decrease of the effective carrying capacity of the system. This may lead to sharp regime shifts induced by stirring in systems with multiple steady states. In prey-predator type systems, stirring leads to resonant response of the population dynamics to fluctuations enhancing the spatial variability-patchiness-in a certain range of stirring rates. Oscillatory population models produce strongly heterogeneous patchy distribution of plankton blooms when the stirring is weak, while strong stirring may either synchronise the oscillatory dynamics, when the inhomogeneity is relatively weak, or suppress oscillations completely (oscillator death) by reducing the effective carrying capacity below the bifurcation point.

  10. LOSCAR: Long-term Ocean-atmosphere-Sediment CArbon cycle Reservoir Model v2.0.4

    NASA Astrophysics Data System (ADS)

    Zeebe, R. E.

    2012-01-01

    The LOSCAR model is designed to efficiently compute the partitioning of carbon between ocean, atmosphere, and sediments on time scales ranging from centuries to millions of years. While a variety of computationally inexpensive carbon cycle models are already available, many are missing a critical sediment component, which is indispensable for long-term integrations. One of LOSCAR's strengths is the coupling of ocean-atmosphere routines to a computationally efficient sediment module. This allows, for instance, adequate computation of CaCO3 dissolution, calcite compensation, and long-term carbon cycle fluxes, including weathering of carbonate and silicate rocks. The ocean component includes various biogeochemical tracers such as total carbon, alkalinity, phosphate, oxygen, and stable carbon isotopes. LOSCAR's configuration of ocean geometry is flexible and allows for easy switching between modern and paleo-versions. We have previously published applications of the model tackling future projections of ocean chemistry and weathering, pCO2 sensitivity to carbon cycle perturbations throughout the Cenozoic, and carbon/calcium cycling during the Paleocene-Eocene Thermal Maximum. The focus of the present contribution is the detailed description of the model including numerical architecture, processes and parameterizations, tuning, and examples of input and output. Typical CPU integration times of LOSCAR are of order seconds for several thousand model years on current standard desktop machines. The LOSCAR source code in C can be obtained from the author by sending a request to loscar.model@gmail.com.

  11. Simulation of the world ocean climate with a massively parallel numerical model

    NASA Astrophysics Data System (ADS)

    Ushakov, K. V.; Ibrayev, R. A.; Kalmykov, V. V.

    2015-07-01

    The INM-IO numerical World Ocean model is verified through the calculation of the model ocean climate. The numerical experiment was conducted for a period of 500 years following the CORE-I protocol. We analyze some basic elements of the large-scale ocean circulation and local and integral characteristics of the model solution. The model limitations and ways they are overcome are described. The results generally fit the level of leading models. This experiment is a necessary step preceding the transition to high-resolution diagnostic and prognostic calculations of the state of the World Ocean and its individual basins.

  12. Multi-agent-based Order Book Model of financial markets

    NASA Astrophysics Data System (ADS)

    Preis, T.; Golke, S.; Paul, W.; Schneider, J. J.

    2006-08-01

    We introduce a simple model for simulating financial markets, based on an order book, in which several agents trade one asset at a virtual exchange continuously. For a stationary market the structure of the model, the order flow rates of the different kinds of order types and the used price time priority matching algorithm produce only a diffusive price behavior. We show that a market trend, i.e. an asymmetric order flow of any type, leads to a non-trivial Hurst exponent for the price development, but not to "fat-tailed" return distributions. When one additionally couples the order entry depth to the prevailing trend, also the stylized empirical fact of "fat tails" can be reproduced by our Order Book Model.

  13. Closing the Seasonal Ocean Surface Temperature Balance in the Eastern Tropical Oceans from Remote Sensing and Model Reanalyses

    NASA Technical Reports Server (NTRS)

    Roberts, J. Brent; Clayson, Carol A.

    2012-01-01

    The Eastern tropical ocean basins are regions of significant atmosphere-ocean interaction and are important to variability across subseasonal to decadal time scales. The numerous physical processes at play in these areas strain the abilities of coupled general circulation models to accurately reproduce observed upper ocean variability. Furthermore, limitations in the observing system of important terms in the surface temperature balance (e.g., turbulent and radiative heat fluxes, advection) introduce uncertainty into the analyses of processes controlling sea surface temperature variability. This study presents recent efforts to close the surface temperature balance through estimation of the terms in the mixed layer temperature budget using state-of-the-art remotely sensed and model-reanalysis derived products. A set of twelve net heat flux estimates constructed using combinations of radiative and turbulent heat flux products - including GEWEX-SRB, ISCCP-SRF, OAFlux, SeaFlux, among several others - are used with estimates of oceanic advection, entrainment, and mixed layer depth variability to investigate the seasonal variability of ocean surface temperatures. Particular emphasis is placed on how well the upper ocean temperature balance is, or is not, closed on these scales using the current generation of observational and model reanalysis products. That is, the magnitudes and spatial variability of residual imbalances are addressed. These residuals are placed into context within the current uncertainties of the surface net heat fluxes and the role of the mixed layer depth variability in scaling the impact of those uncertainties, particularly in the shallow mixed layers of the Eastern tropical ocean basins.

  14. Improving Ocean Angular Momentum Estimates Using a Model Constrained by Data

    NASA Technical Reports Server (NTRS)

    Ponte, Rui M.; Stammer, Detlef; Wunsch, Carl

    2001-01-01

    Ocean angular momentum (OAM) calculations using forward model runs without any data constraints have, recently revealed the effects of OAM variability on the Earth's rotation. Here we use an ocean model and its adjoint to estimate OAM values by constraining the model to available oceanic data. The optimization procedure yields substantial changes in OAM, related to adjustments in both motion and mass fields, as well as in the wind stress torques acting on the ocean. Constrained and unconstrained OAM values are discussed in the context of closing the planet's angular momentum budget. The estimation procedure, yields noticeable improvements in the agreement with the observed Earth rotation parameters, particularly at the seasonal timescale. The comparison with Earth rotation measurements provides an independent consistency check on the estimated ocean state and underlines the importance of ocean state estimation for quantitative. studies of the variable large-scale oceanic mass and circulation fields, including studies of OAM.

  15. Automated mapping of the ocean floor using the theory of intrinsic random functions of order k

    USGS Publications Warehouse

    David, M.; Crozel, D.; Robb, James M.

    1986-01-01

    High-quality contour maps can be computer drawn from single track echo-sounding data by combining Universal Kriging and the theory of intrinsic random function of order K (IRFK). These methods interpolate values among the closely spaced points that lie along relatively widely spaced lines. The technique provides a variance which can be contoured as a quantitative measure of map precision. The technique can be used to evaluate alternative survey trackline configurations and data collection intervals, and can be applied to other types of oceanographic data. ?? 1986 D. Reidel Publishing Company.

  16. Onset time and strength of oceanic deep convection diagnosed from an ocean large-eddy simulation model

    SciTech Connect

    Denbo, D.W.

    1995-01-01

    Deep convection has an important role in the large-scale thermohaline circulation, which in turn plays a central part in determining global climate. Manabe and Stouffer`s climate simulations have shown that the thermal and dynamic structure of the oceans have pronounced changes in model climates with increased CO{sub 2}. In their simulations, the addition of low-salinity surface water at high latitudes prevents the ventilation of the deep ocean, thus reducing or in some cases nearly extinguishing the thermohaline circulation. Siegenthaler and Sarmiento remarked that whereas the ocean is the largest of the rapidly exchanging global carbon reservoirs and a major sink for anthropogenic carbon, this uptake capacity become available only when the whole ocean is chemically equilibrated with the new atmospheric CO{sub 2} concentration. The dynamics of the oceanic uptake of CO{sub 2} is therefore strongly determined by the rate of downward transport of CO{sub 2}-laden water from surface to depth. The importance of deep convection in moderating the uptake of CO{sub 2} by the ocean and its role in the meridional circulation, which affects climate by transporting heat from the tropics to the polar regions, motivates this research. The experiments described here were designed to study the sensitivity of the onset time and strength of deep convection to changes in the heat flux, latent heat flux, and perturbations of the surface mixed-layer temperature and salinity.

  17. Modelling of partially-resolved oceanic symmetric instability

    NASA Astrophysics Data System (ADS)

    Bachman, S. D.; Taylor, J. R.

    2014-10-01

    A series of idealized numerical models have been developed to investigate the effects of partially resolved symmetric instability (SI) in oceanic general circulation models. An analysis of the energetics of symmetric instability is used to argue that the mixed layer can be at least partially restratified even when some SI modes are absent due to either large horizontal viscosity or coarse model resolution. Linear stability analysis reveals that in the idealized models the amount of restratification can be predicted as a function of the grid spacing and viscosity. The models themselves are used to demonstrate these predictions and reveal three possible outcomes in steady-state: (1) incomplete restratification due to viscosity, (2) incomplete restratification due to resolution, and (3) excessive restratification due to anisotropy of the viscosity. The third outcome occurs even on a high-resolution isotropic grid and in two separate numerical models, and thus appears to be a sort of robust numerical feature. The three outcomes are used to recommend criteria that a successful SI parameterization should satisfy.

  18. First and Higher Order Effects on Zero Order Radiative Transfer Model

    NASA Astrophysics Data System (ADS)

    Neelam, M.; Mohanty, B.

    2014-12-01

    Microwave radiative transfer model are valuable tool in understanding the complex land surface interactions. Past literature has largely focused on local sensitivity analysis for factor priotization and ignoring the interactions between the variables and uncertainties around them. Since land surface interactions are largely nonlinear, there always exist uncertainties, heterogeneities and interactions thus it is important to quantify them to draw accurate conclusions. In this effort, we used global sensitivity analysis to address the issues of variable uncertainty, higher order interactions, factor priotization and factor fixing for zero-order radiative transfer (ZRT) model. With the to-be-launched Soil Moisture Active Passive (SMAP) mission of NASA, it is very important to have a complete understanding of ZRT for soil moisture retrieval to direct future research and cal/val field campaigns. This is a first attempt to use GSA technique to quantify first order and higher order effects on brightness temperature from ZRT model. Our analyses reflect conditions observed during the growing agricultural season for corn and soybeans in two different regions in - Iowa, U.S.A and Winnipeg, Canada. We found that for corn fields in Iowa, there exist significant second order interactions between soil moisture, surface roughness parameters (RMS height and correlation length) and vegetation parameters (vegetation water content, structure and scattering albedo), whereas in Winnipeg, second order interactions are mainly due to soil moisture and vegetation parameters. But for soybean fields in both Iowa and Winnipeg, we found significant interactions only to exist between soil moisture and surface roughness parameters.

  19. Explicit Generation of Orthogonal Grids for Ocean Models

    NASA Astrophysics Data System (ADS)

    Murray, Ross J.

    1996-07-01

    Several explicit methods are proposed for generating global orthogonal curvilinear grids for ocean modelling. The methods are based on the conformal properties of stereographic and Mercator map projections and have been developed with the specific object of removing the North Pole from the ocean domain. Some of the configurations, in addition to overcoming the pole problem, have very attractive resolution properties in the polar regions. Two of the constructions are geometrical in nature, while a third is based on the superposition of potential fields generated by discrete coordinate poles. The methods described here differ from those commonly employed in engineering problems in that grid line control is exercised by the placement of a finite number of singularities, and no specific condition is placed upon the fitting of coordinate lines to physical boundaries. The grids produced are accordingly of global construction and have smooth variations in grid size. Being of analytical or semi-analytical formulation, the grids may be generated quickly and without the need for advanced software.

  20. Modeling Thermal and Environmental Effects of Prototype Scale Ocean Thermal Energy Conversion

    NASA Astrophysics Data System (ADS)

    Hamrick, J. M.

    2010-12-01

    Ocean thermal energy conversion (OTEC) utilizes the temperature difference between the mix lay and deep water electricity generation. The small temperature difference compared to other thermal-electric generation devises, typically between 20 and 25 C, requires the substantial volumetric flows on the order of hundreds of cubic meters per second to generate net energy and recover capital investments. This presentation described the use of a high resolution three-dimensional EFDC model with an embedded jet-plume model to simulate the thermal and environmental impacts of a number of prototype OTEC configurations on the southwest coast of Oahu, Hawaii. The EFDC model is one-way nested into a larger scale ROMS model to allow for realistic incorporation of region processes including external and internal tides and sub-tidal circulation. Impacts on local thermal structure and the potential for nutrient enrichment of the mixed layer are addressed with model and presented.

  1. Modelling Limit Order Execution Times from Market Data

    NASA Astrophysics Data System (ADS)

    Kim, Adlar; Farmer, Doyne; Lo, Andrew

    2007-03-01

    Although the term ``liquidity'' is widely used in finance literatures, its meaning is very loosely defined and there is no quantitative measure for it. Generally, ``liquidity'' means an ability to quickly trade stocks without causing a significant impact on the stock price. From this definition, we identified two facets of liquidity -- 1.execution time of limit orders, and 2.price impact of market orders. The limit order is an order to transact a prespecified number of shares at a prespecified price, which will not cause an immediate execution. On the other hand, the market order is an order to transact a prespecified number of shares at a market price, which will cause an immediate execution, but are subject to price impact. Therefore, when the stock is liquid, market participants will experience quick limit order executions and small market order impacts. As a first step to understand market liquidity, we studied the facet of liquidity related to limit order executions -- execution times. In this talk, we propose a novel approach of modeling limit order execution times and show how they are affected by size and price of orders. We used q-Weibull distribution, which is a generalized form of Weibull distribution that can control the fatness of tail to model limit order execution times.

  2. Response of the Antarctic ice sheet to ocean forcing using the POPSICLES coupled ice sheet-ocean model

    NASA Astrophysics Data System (ADS)

    Martin, D. F.; Asay-Davis, X.; Price, S. F.; Cornford, S. L.; Maltrud, M. E.; Ng, E. G.; Collins, W.

    2014-12-01

    We present the response of the continental Antarctic ice sheet to sub-shelf-melt forcing derived from POPSICLES simulation results covering the full Antarctic Ice Sheet and the Southern Ocean spanning the period 1990 to 2010. Simulations are performed at 0.1 degree (~5 km) ocean resolution and ice sheet resolution as fine as 500 m using adaptive mesh refinement. A comparison of fully-coupled and comparable standalone ice-sheet model results demonstrates the importance of two-way coupling between the ice sheet and the ocean. The POPSICLES model couples the POP2x ocean model, a modified version of the Parallel Ocean Program (Smith and Gent, 2002), and the BISICLES ice-sheet model (Cornford et al., 2012). BISICLES makes use of adaptive mesh refinement to fully resolve dynamically-important regions like grounding lines and employs a momentum balance similar to the vertically-integrated formulation of Schoof and Hindmarsh (2009). Results of BISICLES simulations have compared favorably to comparable simulations with a Stokes momentum balance in both idealized tests like MISMIP3D (Pattyn et al., 2013) and realistic configurations (Favier et al. 2014). POP2x includes sub-ice-shelf circulation using partial top cells (Losch, 2008) and boundary layer physics following Holland and Jenkins (1999), Jenkins (2001), and Jenkins et al. (2010). Standalone POP2x output compares well with standard ice-ocean test cases (e.g., ISOMIP; Losch, 2008) and other continental-scale simulations and melt-rate observations (Kimura et al., 2013; Rignot et al., 2013). A companion presentation, "Present-day circum-Antarctic simulations using the POPSICLES coupled land ice-ocean model" in session C027 describes the ocean-model perspective of this work, while we focus on the response of the ice sheet and on details of the model. The figure shows the BISICLES-computed vertically-integrated ice velocity field about 1 month into a 20-year coupled Antarctic run. Groundling lines are shown in green.

  3. A Comparison between the TOPEX/POSEIDON Data and a Global Ocean General Circulation Model during 1992-1993

    NASA Technical Reports Server (NTRS)

    Chao, Yi; Fu, Lee-Lueng

    1995-01-01

    The TOPEX/POSEIDON altimetric sea level observation during 1992-1993 was used to validate the simulation made by a global ocean general circulation model (OGCM) forced by the daily wind stress and heat flux derived from the National Meteorological Center operational analysis. The OGCM is a version of the modular ocean model with a horizontal resolution of 2 deg longitude and 1 deg latitude and 22 levels in the vertical. The model simulation is compared to the observation at spatial scales of the order of 500 km and larger. Only the temporal variations are examined. The variability is composed primarily of the annual cycle and intraseasonal fluctuations (periods shorter than 100 days). The basic features of the annual cycle are simulated well by the model. Major discrepancies are found in the eastern tropical Pacific, as well as the eastern North Pacific and most of the interior of the North Atlantic. The culprit is suspected to be the inadequate heat forcing and mixing parameterizations of the model. Significant intraseasonal variability is found in the central North Pacific and the Southern Ocean. The simulation is highly correlated with the observation at periods from 20 to 100 days. The spatial scales are larger than 1000 km in many places. These variabilities are apparently the barotropic response of the ocean to wind forcing. The results of the study provide a basis for future assimilation of the data into the OGCM for improved description of the large-scale ocean variabilities.

  4. Using Green's Functions to initialize and adjust a global, eddying ocean biogeochemistry general circulation model

    NASA Astrophysics Data System (ADS)

    Brix, H.; Menemenlis, D.; Hill, C.; Dutkiewicz, S.; Jahn, O.; Wang, D.; Bowman, K.; Zhang, H.

    2015-11-01

    The NASA Carbon Monitoring System (CMS) Flux Project aims to attribute changes in the atmospheric accumulation of carbon dioxide to spatially resolved fluxes by utilizing the full suite of NASA data, models, and assimilation capabilities. For the oceanic part of this project, we introduce ECCO2-Darwin, a new ocean biogeochemistry general circulation model based on combining the following pre-existing components: (i) a full-depth, eddying, global-ocean configuration of the Massachusetts Institute of Technology general circulation model (MITgcm), (ii) an adjoint-method-based estimate of ocean circulation from the Estimating the Circulation and Climate of the Ocean, Phase II (ECCO2) project, (iii) the MIT ecosystem model "Darwin", and (iv) a marine carbon chemistry model. Air-sea gas exchange coefficients and initial conditions of dissolved inorganic carbon, alkalinity, and oxygen are adjusted using a Green's Functions approach in order to optimize modeled air-sea CO2 fluxes. Data constraints include observations of carbon dioxide partial pressure (pCO2) for 2009-2010, global air-sea CO2 flux estimates, and the seasonal cycle of the Takahashi et al. (2009) Atlas. The model sensitivity experiments (or Green's Functions) include simulations that start from different initial conditions as well as experiments that perturb air-sea gas exchange parameters and the ratio of particulate inorganic to organic carbon. The Green's Functions approach yields a linear combination of these sensitivity experiments that minimizes model-data differences. The resulting initial conditions and gas exchange coefficients are then used to integrate the ECCO2-Darwin model forward. Despite the small number (six) of control parameters, the adjusted simulation is significantly closer to the data constraints (37% cost function reduction, i.e., reduction in the model-data difference, relative to the baseline simulation) and to independent observations (e.g., alkalinity). The adjusted air-sea gas

  5. US GODAE: Global Ocean Prediction with the Hybrid Coordinate Ocean Model (HYCOM)

    DTIC Science & Technology

    2009-06-01

    coastal application was to assess the impact of open boundary conditions from the HYCOM ocean prediction system on the dynamics and accuracy of a...near the Florida Keys when hurricane Katrina crossed South Florida in late August 2005. iMPact In summary, 25 institutions (nine from academia, nine...example, detailed surface current information derived from HYCOM is summarized by OCENS (Ocean and Coastal ENviromental Sensing, http

  6. U.S. GODAE: Global Ocean Prediction With the HYbrid Coordinate Ocean Model (HYCOM)

    DTIC Science & Technology

    2009-06-01

    and ocean prediction system developers. The main goal of the first coastal application was to assess the impact of open boundary conditions from...Keys when hurricane Katrina crossed South Florida in late August 2005. IMPACT In summary, 25 institutions (nine from academia, nine from...Ocean and Coastal ENviromental Sensing, http://www.ocens.com) for their customers who continually provide posi- tive feedback on their accuracy

  7. U.S. Navy Hindcast Spectral Ocean Wave Model Climatic Atlas: North Atlantic Ocean

    DTIC Science & Technology

    1983-10-01

    for their technical w, Ms. Pamela J. Young, Ms. Elaine H. Mason, The development of a Spectral Ocean Wave Ms. Laura K. Metcalf for their data proces...Research and Development Center; Mr. She] which this atlas is based. Lazanoff previously of Fleet Numel Oceanography Center; Dr. Ledolph Baer of...Ship Ocean on Research and Development Center; Mr. Sheldon Lazanoff previously of Fleet Numerical Oceanography Center; Dr. Ledolph Baer of the National

  8. A model to simulate nonhydrostatic internal gravity waves in the ocean

    NASA Astrophysics Data System (ADS)

    Vitousek, S.; Fringer, O. B.; Zhang, Y.

    2015-12-01

    Internal gravity waves in the ocean are primarily generated due to tidal flow over topography that generates internal tides, or internal waves of tidal frequency. As they propagate, internal tides steepen into trains of internal solitary waves that eventually break upon interacting with shallow coastal topography. Modeling internal solitary waves is difficult because they have length scales that are short relative to the internal tide, and so many grid points in three dimensions are needed to accurately resolve their evolution. Because internal solitary waves arise from a balance between nonlinear advection of momentum and nonhydrostatic dispersion, they must be simulated with nonhydrostatic ocean models. Such models are expensive because computation of the nonhydrostatic pressure requires solution of a three-dimensional Poisson equation that can incur an order of magnitude increase in the computational cost. Finally, because internal solitary waves can propagate over long distances with little to no dissipation or mixing of the thermocline upon which they propagate, the numerical model must minimize spurious vertical numerical diffusion of the density field. We will discuss development of a new ocean model designed to accurately simulate internal solitary waves. Horizontally unstructured, finite-volume grids are employed to enable resolution of the multiscale nature of internal solitary waves by refining the grid where they are likely to form. To resolve the nonlinear-nonhydrostatic balance in the waves, the model computes the nonhydrostatic pressure, but with a preconditioner that ensures minimal overhead where the nonhydrotatic pressure is not needed. Finally, to minimize spurious numerical diffusion, we employ an Arbitrary-Lagrangian-Eulerian (ALE), or hybrid, vertical coordinate system in which the vertical direction is discretized with boundary-following (sigma or s), Cartesian (z), or density-following (isopycnal) coordinates. Because isopycnal coordinates

  9. Building Higher-Order Markov Chain Models with EXCEL

    ERIC Educational Resources Information Center

    Ching, Wai-Ki; Fung, Eric S.; Ng, Michael K.

    2004-01-01

    Categorical data sequences occur in many applications such as forecasting, data mining and bioinformatics. In this note, we present higher-order Markov chain models for modelling categorical data sequences with an efficient algorithm for solving the model parameters. The algorithm can be implemented easily in a Microsoft EXCEL worksheet. We give a…

  10. Optimisation methods for bathymetry and open boundary conditions in finite element model of ocean tides

    SciTech Connect

    Lyard, F.; Genco, M.L.

    1994-10-01

    A bidimensional, spectral in time, quasi-linearised hydrodynamic ocean tide model has been developed at the Institut de Mecanique de Grenoble. This model is derived from the classical shallow water equations by removing the velocity unknowns in the continuity equation, that leads to an elliptic, second-order differential equation where tide denivellation remains the only unknown quantity. The problem is solved in its variational formulation and the finite elements method is used to discretise the equations in the spatial domain with a Lagrange-P2 approximation. Bottom topography has to be known at the integration points of the elements. In the case of the large oceanic basins, a specific method, called the bathymetry optimisation method, is needed to correctly take into account the bottom topography inside the model. The accuracy of the model`s solutions is also strongly dependent on the quality of the open boundary conditions because of the elliptic characteristics of the problem. The optimisation method for open boundary conditions relies on the use of the in situ data available in the modelled domain. The aim of this paper is to present the basis of these optimisations of bathymetry and open boundary conditions. An illustration of the related improvements is presented on the North Atlantic Basin. 36 refs., 10 figs., 5 tabs.

  11. First-order estimate of the planktic foraminifer biomass in the modern ocean

    NASA Astrophysics Data System (ADS)

    Schiebel, R.; Movellan, A.

    2012-09-01

    Planktic foraminifera are heterotrophic mesozooplankton of global marine abundance. The position of planktic foraminifers in the marine food web is different compared to other protozoans and ranges above the base of heterotrophic consumers. Being secondary producers with an omnivorous diet, which ranges from algae to small metazoans, planktic foraminifers are not limited to a single food source, and are assumed to occur at a balanced abundance displaying the overall marine biological productivity at a regional scale. With a new non-destructive protocol developed from the bicinchoninic acid (BCA) method and nano-photospectrometry, we have analysed the protein-biomass, along with test size and weight, of 754 individual planktic foraminifers from 21 different species and morphotypes. From additional CHN analysis, it can be assumed that protein-biomass equals carbon-biomass. Accordingly, the average individual planktic foraminifer protein- and carbon-biomass amounts to 0.845 μg. Samples include symbiont bearing and symbiont-barren species from the sea surface down to 2500 m water depth. Conversion factors between individual biomass and assemblage-biomass are calculated for test sizes between 72 and 845 μm (minimum test diameter). Assemblage-biomass data presented here include 1128 sites and water depth intervals. The regional coverage of data includes the North Atlantic, Arabian Sea, Red Sea, and Caribbean as well as literature data from the eastern and western North Pacific, and covers a wide range of oligotrophic to eutrophic waters over six orders of magnitude of planktic-foraminifer assemblage-biomass (PFAB). A first order estimate of the average global planktic foraminifer biomass production (>125 μm) ranges from 8.2-32.7 Tg C yr-1 (i.e. 0.008-0.033 Gt C yr-1), and might be more than three times as high including neanic and juvenile individuals adding up to 25-100 Tg C yr-1. However, this is a first estimate of regional PFAB extrapolated to the global scale

  12. On Impacts of Ocean Waves in Marginal Ice Zones and their Repercussions for Arctic Ice/Ocean Models (Invited)

    NASA Astrophysics Data System (ADS)

    Squire, V. A.

    2013-12-01

    Associated with a gradual metamorphosis of summer Arctic sea ice -- from a quasi-continuous ice sheet punctuated by pressure ridges and leads to a mélange of ice floes resembling a MIZ, is an augmented presence of sizeable ocean waves that may have propagated into the pack ice from distant storms or have arisen within the MIZ itself due to the larger fetches that are now more common [Francis et al., 2011]. If sufficiently forceful as they pass through the ice field, these waves can break up the ice floes to create a new floe size distribution (FSD), change local concentration by moving floes around, and supplement the melting that is occurring because of ice albedo feedback. In turn, the ocean waves themselves attenuate due to conservative scattering from the randomly-sized, spatially-disordered floes and cakes making up the MIZ that diffuse the waves and return energy to neighboring open water, and lose energy through several prospective dissipative processes. Consequently, the omission of ocean waves from ice/ocean models is unwise, as they can potentially alter atmosphere-ice-ocean coupling appreciably by affecting MIZ morphology so radically. In a series of 3 research projects, involving scientists from Norway, Canada, Australia and NZ, we have systematically investigated how ocean wave interactions with sea ice can be embedded in an ice/ocean model; first at high resolution in the Fram Strait and later in other MIZ around the Arctic Basin. In each case it has been possible to track how the MIZ forms and, on the basis of its FSD or an abrupt change of concentration, how wide it becomes as a result of an inbound wave field provided by a spectral model such as WAM. Initially unidirectional seas were considered [Williams et al., 2013ab] but more sophisticated 2D scattering paradigms are now being developed that allow directionally defined seas to be modeled. Based upon the recognition that a MIZ can be delineated into a number of contiguous bands of ice floes

  13. Predicting Tests Ordered in Hospital Laboratories using Generalized Linear Modeling.

    PubMed

    Leaven, Laquanda T

    2016-01-01

    Laboratory services in healthcare systems play a vital role in inpatient care. Most hospital laboratories are facing the challenge of reducing cost and improving service quality. The author focuses on identifying test order patterns in a laboratory for a large urban hospital. The data collected from this facility consists of all tests ordered over a three-month time frame and contains test orders for approximately 17,500 patients. Poisson and negative binomial regression models are used to determine how well patient characteristics (patient length of stay and the medical units in which patients are placed) will predict the number of tests being ordered. The test order prediction model developed in this study will aid the management and phlebotomists in the hospital laboratory in securing methods to satisfy the test order demand. By implementing the recommendations of this study, hospital laboratories should see significant improvements in phlebotomist productivity and resource utilization, implementation of which could result in cost savings.

  14. Phase-field-crystal model for ordered crystals

    NASA Astrophysics Data System (ADS)

    Alster, Eli; Elder, K. R.; Hoyt, Jeffrey J.; Voorhees, Peter W.

    2017-02-01

    We describe a general method to model multicomponent ordered crystals using the phase-field-crystal (PFC) formalism. As a test case, a generic B2 compound is investigated. We are able to produce a line of either first-order or second-order order-disorder phase transitions, features that have not been incorporated in existing PFC approaches. Further, it is found that the only elastic constant for B2 that depends on ordering is C11. This B2 model is then used to study antiphase boundaries (APBs). The APBs are shown to reproduce classical mean-field results. Dynamical simulations of ordering across small-angle grain boundaries predict that dislocation cores pin the evolution of APBs.

  15. Ocean Turbulence I: One-Point Closure Model Momentum and Heat Vertical Diffusivities

    NASA Technical Reports Server (NTRS)

    Canuto, V. M.; Howard, A.; Cheng, Y.; Dubovikov, M. S.

    1999-01-01

    Since the early forties, one-point turbulence closure models have been the canonical tools used to describe turbulent flows in many fields. In geophysics, Mellor and Yamada applied such models using the 1980 state-of-the art. Since then, no improvements were introduced to alleviate two major difficulties: 1) closure of the pressure correlations, which affects the correct determination of the critical Richardson number Ri(sub cr) above which turbulent mixing is no longer possible and 2) the need to express the non-local third-order moments (TOM) in terms of lower order moments rather than via the down-gradient approximation as done thus far, since the latter seriously underestimates the TOMs. Since 1) and 2) are still being dealt with adjustable parameters which weaken the credibility of the models, alternative models, not based on turbulence modeling, have been suggested. The aim of this paper is to show that new information, partly derived from the newest 2-point closure model discussed, can be used to solve these shortcomings. The new one-point closure model, which in its simplest form is algebraic and thus simple to implement, is first shown to reproduce a variety of data. Then, it is used in a Ocean-General Circulation Model (O-GCM) where it reproduces well a large variety of ocean data. While phenomenological models are specifically tuned to ocean turbulence, the present model is not. It is first tested against laboratory data on stably stratified flows and then used in an O-GCM. It is more general, more predictive and more resilient, e.g., it can incorporate phenomena like wave-breaking at the surface, salinity diffusivity, non-locality, etc. One important feature that naturally comes out of the new model is that the predicted Richardson critical value Ri(sub cr) is Ri (sub cr approx. = 1) in agreement with both Large Eddy Simulations (LES) and empirical evidence while all previous models predicted Ri (sub cr approx. = 0.2) which led to a considerable

  16. Atmospheric Turbulence Modeling for Aerospace Vehicles: Fractional Order Fit

    NASA Technical Reports Server (NTRS)

    Kopasakis, George (Inventor)

    2015-01-01

    An improved model for simulating atmospheric disturbances is disclosed. A scale Kolmogorov spectral may be scaled to convert the Kolmogorov spectral into a finite energy von Karman spectral and a fractional order pole-zero transfer function (TF) may be derived from the von Karman spectral. Fractional order atmospheric turbulence may be approximated with an integer order pole-zero TF fit, and the approximation may be stored in memory.

  17. Behaviour of oceanic 137Cs following the Fukushima Daiichi Nuclear Power Plant accident for four years simulated numerically by a regional ocean model

    NASA Astrophysics Data System (ADS)

    Torn, M. S.; Koven, C. D.; Riley, W. J.; Zhu, B.; Hicks Pries, C.; Phillips, C. L.

    2014-12-01

    A series of accidents at the Fukushima Dai-ichi Nuclear Power Plant (1F NPP) following the earthquake and tsunami of 11 March 2011 resulted in the release of radioactive materials to the ocean by two major pathways, direct release from the accident site and atmospheric deposition.We reconstructed spatiotemporal variability of 137Cs activity in the regional ocean for four years by numerical model, such as a regional scale and the North Pacific scale oceanic dispersion models, an atmospheric transport model, a sediment transport model, a dynamic biological compartment model for marine biota and river runoff model. Direct release rate of 137Cs were estimated for four years after the accident by comparing simulated results and observed activities very close to the site. The estimated total amounts of directly release was 3.6±0.7 PBq. Directly release rate of 137Cs decreased exponentially with time by the end of December 2012 and then, was almost constant. Decrease rate were quite small after 2013. The daily release rate of 137Cs was estimated to be the order of magnitude of 1010 Bq/day by the end of March 2015. The activity of directly released 137Cs was detectable only in the coastal zone after December 2012. Simulated 137Cs activities attributable to direct release were in good agreement with observed activities, a result that implies the estimated direct release rate was reasonable. There is no observed data of 137Cs activity in the ocean from 11 to 21 March 2011. Observed data of marine biota should reflect the history of 137Cs activity in this early period. We reconstructed the history of 137Cs activity in this early period by considering atmospheric deposition, river input, rain water runoff from the 1F NPP site. The comparisons between simulated 137Cs activity of marine biota by a dynamic biological compartment and observed data also suggest that simulated 137Cs activity attributable to atmospheric deposition was underestimated in this early period. The

  18. Behaviour of oceanic 137Cs following the Fukushima Daiichi Nuclear Power Plant accident for four years simulated numerically by a regional ocean model

    NASA Astrophysics Data System (ADS)

    Tsumune, D.; Tsubono, T.; Aoyama, M.; Misumi, K.; Tateda, Y.

    2015-12-01

    A series of accidents at the Fukushima Dai-ichi Nuclear Power Plant (1F NPP) following the earthquake and tsunami of 11 March 2011 resulted in the release of radioactive materials to the ocean by two major pathways, direct release from the accident site and atmospheric deposition.We reconstructed spatiotemporal variability of 137Cs activity in the regional ocean for four years by numerical model, such as a regional scale and the North Pacific scale oceanic dispersion models, an atmospheric transport model, a sediment transport model, a dynamic biological compartment model for marine biota and river runoff model. Direct release rate of 137Cs were estimated for four years after the accident by comparing simulated results and observed activities very close to the site. The estimated total amounts of directly release was 3.6±0.7 PBq. Directly release rate of 137Cs decreased exponentially with time by the end of December 2012 and then, was almost constant. Decrease rate were quite small after 2013. The daily release rate of 137Cs was estimated to be the order of magnitude of 1010 Bq/day by the end of March 2015. The activity of directly released 137Cs was detectable only in the coastal zone after December 2012. Simulated 137Cs activities attributable to direct release were in good agreement with observed activities, a result that implies the estimated direct release rate was reasonable. There is no observed data of 137Cs activity in the ocean from 11 to 21 March 2011. Observed data of marine biota should reflect the history of 137Cs activity in this early period. We reconstructed the history of 137Cs activity in this early period by considering atmospheric deposition, river input, rain water runoff from the 1F NPP site. The comparisons between simulated 137Cs activity of marine biota by a dynamic biological compartment and observed data also suggest that simulated 137Cs activity attributable to atmospheric deposition was underestimated in this early period. The

  19. Modelling the ocean site effect on seismic noise body waves

    NASA Astrophysics Data System (ADS)

    Gualtieri, L.; Stutzmann, E.; Farra, V.; Capdeville, Y.; Schimmel, M.; Ardhuin, F.; Morelli, A.

    2014-05-01

    Secondary microseismic noise is generated by non-linear interactions between ocean waves at the ocean surface. We present here the theory for computing the site effect of the ocean layer upon body waves generated by noise sources distributed along the ocean surface. By defining the wavefield as the superposition of plane waves, we show that the ocean site effect can be described as the constructive interference of multiply reflected P waves in the ocean that are then converted to either P or SV waves at the ocean-crust interface. We observe that the site effect varies strongly with period and ocean depth, although in a different way for body waves than for Rayleigh waves. We also show that the ocean site effect is stronger for P waves than for S waves. We validate our computation by comparing the theoretical noise body wave sources with the sources inferred from beamforming analysis of the three seismogram components recorded by the Southern California Seismic Network. We use rotated traces for the beamforming analysis, and we show that we clearly detect P waves generated by ocean gravity wave interactions along the track of typhoon Ioke (2006 September). We do not detect the corresponding SV waves, and we demonstrate that this is because their amplitude is too weak.

  20. Dynamics of the Atlantic meridional overturning circulation and Southern Ocean in an ocean model of intermediate complexity

    NASA Astrophysics Data System (ADS)

    McCreary, Julian P.; Furue, Ryo; Schloesser, Fabian; Burkhardt, Theodore W.; Nonaka, Masami

    2016-04-01

    A steady-state, variable-density, 2-layer, ocean model (VLOM) is used to investigate basic dynamics of the Atlantic meridional overturning circulation and Southern Ocean. The domain consists of idealized (rectangular) representations of the Atlantic, Southern, and Pacific Oceans. The model equations represent the depth-averaged, layer-1 response (except for one solution in which they represent the depth-integrated flow over both layers). To allow for overturning, water can cross the bottom of layer 1 at the velocity we =wd +wm +wn , the three parts representing: interior diffusion wd that increases the layer-1 thickness h throughout the basin, mixed-layer entrainment wm that ensures h is never less than a minimum value hm , and diapycnal (cooling) processes external to the basin wn that adjust h to hn . For most solutions, horizontal mixing has the form of Rayleigh damping with coefficient ν , which we interpret to result from baroclinic instability through the closure, V∗ = - (ν /f2) ∇P , where ∇P = ∇(1/2 g‧h2) is the depth-integrated pressure gradient, g‧ is the reduced-gravity coefficient, and ν is a mixing coefficient; with this interpretation, the layer-1 flow corresponds to the sum of the Eulerian-mean and eddy-mean (V∗) transport/widths, that is, the "residual" circulation. Finally, layer-1 temperature cools polewards in response to a surface heat flux Q, and the cooling can be strong enough in the Southern Ocean for g‧ = 0 south of a latitude y0 , in which case layer 1 vanishes and the model reduces to a single layer 2. Solutions are obtained both numerically and analytically. The analytic approach splits fields into interior and boundary-layer parts, from which a coupled set of integral constraints can be derived. The set allows properties of the circulation (upwelling-driven transport out of the Southern Ocean M , downwelling transport in the North Atlantic, transport of the Antarctic Circumpolar Current) and stratification (Atlantic

  1. Parallelism and optimization of numerical ocean forecasting model

    NASA Astrophysics Data System (ADS)

    Xu, Jianliang; Pang, Renbo; Teng, Junhua; Liang, Hongtao; Yang, Dandan

    2016-10-01

    According to the characteristics of Chinese marginal seas, the Marginal Sea Model of China (MSMC) has been developed independently in China. Because the model requires long simulation time, as a routine forecasting model, the parallelism of MSMC becomes necessary to be introduced to improve the performance of it. However, some methods used in MSMC, such as Successive Over Relaxation (SOR) algorithm, are not suitable for parallelism. In this paper, methods are developedto solve the parallel problem of the SOR algorithm following the steps as below. First, based on a 3D computing grid system, an automatic data partition method is implemented to dynamically divide the computing grid according to computing resources. Next, based on the characteristics of the numerical forecasting model, a parallel method is designed to solve the parallel problem of the SOR algorithm. Lastly, a communication optimization method is provided to avoid the cost of communication. In the communication optimization method, the non-blocking communication of Message Passing Interface (MPI) is used to implement the parallelism of MSMC with complex physical equations, and the process of communication is overlapped with the computations for improving the performance of parallel MSMC. The experiments show that the parallel MSMC runs 97.2 times faster than the serial MSMC, and root mean square error between the parallel MSMC and the serial MSMC is less than 0.01 for a 30-day simulation (172800 time steps), which meets the requirements of timeliness and accuracy for numerical ocean forecasting products.

  2. Predictability of the Indian Ocean Dipole in the coupled models

    NASA Astrophysics Data System (ADS)

    Liu, Huafeng; Tang, Youmin; Chen, Dake; Lian, Tao

    2017-03-01

    In this study, the Indian Ocean Dipole (IOD) predictability, measured by the Indian Dipole Mode Index (DMI), is comprehensively examined at the seasonal time scale, including its actual prediction skill and potential predictability, using the ENSEMBLES multiple model ensembles and the recently developed information-based theoretical framework of predictability. It was found that all model predictions have useful skill, which is normally defined by the anomaly correlation coefficient larger than 0.5, only at around 2-3 month leads. This is mainly because there are more false alarms in predictions as leading time increases. The DMI predictability has significant seasonal variation, and the predictions whose target seasons are boreal summer (JJA) and autumn (SON) are more reliable than that for other seasons. All of models fail to predict the IOD onset before May and suffer from the winter (DJF) predictability barrier. The potential predictability study indicates that, with the model development and initialization improvement, the prediction of IOD onset is likely to be improved but the winter barrier cannot be overcome. The IOD predictability also has decadal variation, with a high skill during the 1960s and the early 1990s, and a low skill during the early 1970s and early 1980s, which is very consistent with the potential predictability. The main factors controlling the IOD predictability, including its seasonal and decadal variations, are also analyzed in this study.

  3. A Model for the National Assessment of Higher Order Thinking.

    ERIC Educational Resources Information Center

    Paul, Richard; Nosich, Gerald M.

    This document provides a model for the national assessment of higher order thinking and consists of a preface and four main sections. The preface discusses the problem of lower order learning, summarizes the state of research into critical thinking and instructional reform, and explains the structure of the paper. Section 1 of the paper describes…

  4. Stable static structures in models with higher-order derivatives

    SciTech Connect

    Bazeia, D.; Lobão, A.S.; Menezes, R.

    2015-09-15

    We investigate the presence of static solutions in generalized models described by a real scalar field in four-dimensional space–time. We study models in which the scalar field engenders higher-order derivatives and spontaneous symmetry breaking, inducing the presence of domain walls. Despite the presence of higher-order derivatives, the models keep to equations of motion second-order differential equations, so we focus on the presence of first-order equations that help us to obtain analytical solutions and investigate linear stability on general grounds. We then illustrate the general results with some specific examples, showing that the domain wall may become compact and that the zero mode may split. Moreover, if the model is further generalized to include k-field behavior, it may contribute to split the static structure itself.

  5. Multi-Model Comparison of Southern Ocean and Sea Ice Trends in CORE-II and CMIP5 Model

    NASA Astrophysics Data System (ADS)

    Downes, S. M.; Griffies, S. M.; Farneti, R.; Marsland, S. J.; Uotila, P.; Hogg, A.

    2014-12-01

    The Southern Ocean circulation, influenced by buoyancy, momentum and sea ice processes, varies on seasonal to centennial timescales. Incomplete spatio-temporal observations of the full ocean water column, overlying ocean-ice-atmosphere fluxes, and adjacent polar dynamics challenge our ability to model the Southern Ocean. However, several studies have indicated this region is particularly important in the evolving climate, including the anthropogenic influences. Models coherently capture large-scale Southern Ocean patterns, however it is the magnitude and location of these patterns that varies widely. In particular, difficulties with modelling of small scale processes remains an outstanding issue. Here we review the representation of the Southern Ocean circulation, including fluxes at the ocean-ice and ocean-atmosphere interfaces, in numerous coupled climate models from two international modeling efforts, namely the Coordinated Ocean-ice Reference Experiments Phase II (CORE-II) and Coupled Model Intercomparison Project Phase 5 (CMIP5). We focus on the relationships between large scale and mesoscale overturning circulation, formation of key water masses and the associated deep winter mixed layers, buoyancy and wind fluxes, and sea ice. We identify major uncertainties in the modelling of past, present and projected large-scale ocean processes, and provide insights for future modelling directions.

  6. Bayesian Model Comparison for the Order Restricted RC Association Model

    ERIC Educational Resources Information Center

    Iliopoulos, G.; Kateri, M.; Ntzoufras, I.

    2009-01-01

    Association models constitute an attractive alternative to the usual log-linear models for modeling the dependence between classification variables. They impose special structure on the underlying association by assigning scores on the levels of each classification variable, which can be fixed or parametric. Under the general row-column (RC)…

  7. Parallel Nonnegative Least Squares Solvers for Model Order Reduction

    DTIC Science & Technology

    2016-03-01

    NNLS problems that arise when the Energy Conserving Sampling and Weighting hyper-reduction procedure is used when constructing a reduced-order model...ScaLAPACK and performance results are presented. nonnegative least squares, model order reduction, hyper-reduction, Energy Conserving Sampling and...nonnegative least squares (NNLS) prob- lem comes from the embedded hyper-reduction step referred to as Energy Conserv- ing Sampling and Weighting (ECSW

  8. Reduced-order models for vertical human-structure interaction

    NASA Astrophysics Data System (ADS)

    Van Nimmen, Katrien; Lombaert, Geert; De Roeck, Guido; Van den Broeck, Peter

    2016-09-01

    For slender and lightweight structures, the vibration serviceability under crowd- induced loading is often critical in design. Currently, designers rely on equivalent load models, upscaled from single-person force measurements. Furthermore, it is important to consider the mechanical interaction with the human body as this can significantly reduce the structural response. To account for these interaction effects, the contact force between the pedestrian and the structure can be modelled as the superposition of the force induced by the pedestrian on a rigid floor and the force resulting from the mechanical interaction between the structure and the human body. For the case of large crowds, however, this approach leads to models with a very high system order. In the present contribution, two equivalent reduced-order models are proposed to approximate the dynamic behaviour of the full-order coupled crowd-structure system. A numerical study is performed to evaluate the impact of the modelling assumptions on the structural response to pedestrian excitation. The results show that the full-order moving crowd model can be well approximated by a reduced-order model whereby the interaction with the pedestrians in the crowd is modelled using a single (equivalent) SDOF system.

  9. Three-dimensional turbulent bottom density currents from a high-order nonhydrostatic spectral element model.

    SciTech Connect

    Ozgokmen, T.; Fischer, P.; Duan, J.; Iliescu, T.; Mathematics and Computer Science; Univ. of Miami; IIT; Virginia Polytechnic Inst. and State Univ.

    2004-09-01

    Overflows are bottom gravity currents that supply dense water masses generated in high-latitude and marginal seas into the general circulation. Oceanic observations have revealed that mixing of overflows with ambient water masses takes place over small spatial and time scales. Studies with ocean general circulation models indicate that the strength of the thermohaline circulation is strongly sensitive to representation of overflows in these models. In light of these results, overflow-induced mixing emerges as one of the prominent oceanic processes. In this study, as a continuation of an effort to develop appropriate process models for overflows, nonhydrostatic 3D simulations of bottom gravity are carried out that would complement analysis of dedicated observations and large-scale ocean modeling. A parallel high-order spectral-element Navier-Stokes solver is used as the basis of the simulations. Numerical experiments are conducted in an idealized setting focusing on the startup phase of a dense water mass released at the top of a sloping wedge. Results from 3D experiments are compared with results from 2D experiments and laboratory experiments, based on propagation speed of the density front, growth rate of the characteristic head at the leading edge, turbulent overturning length scales, and entrainment parameters. Results from 3D experiments are found to be in general agreement with those from laboratory tank experiments. In 2D simulations, the propagation speed is approximately 20% slower than that of the 3D experiments and the head growth rate is 3 times as large, Thorpe scales are 1.3-1.5 times as large, and the entrainment parameter is up to 2 times as large as those in the 3D experiments. The differences between 2D and 3D simulations are entirely due to internal factors associated with the truncation of the Navier-Stokes equations for 2D approximation.

  10. Deep ocean warming assessed from altimeters, Gravity Recovery and Climate Experiment, in situ measurements, and a non-Boussinesq ocean general circulation model

    NASA Astrophysics Data System (ADS)

    Song, Y. Tony; Colberg, Frank

    2011-02-01

    Observational surveys have shown significant oceanic bottom water warming, but they are too spatially and temporally sporadic to quantify the deep ocean contribution to the present-day sea level rise (SLR). In this study, altimetry sea surface height (SSH), Gravity Recovery and Climate Experiment (GRACE) ocean mass, and in situ upper ocean (0-700 m) steric height have been assessed for their seasonal variability and trend maps. It is shown that neither the global mean nor the regional trends of altimetry SLR can be explained by the upper ocean steric height plus the GRACE ocean mass. A non-Boussinesq ocean general circulation model (OGCM), allowing the sea level to rise as a direct response to the heat added into the ocean, is then used to diagnose the deep ocean steric height. Constrained by sea surface temperature data and the top of atmosphere (TOA) radiation measurements, the model reproduces the observed upper ocean heat content well. Combining the modeled deep ocean steric height with observational upper ocean data gives the full depth steric height. Adding a GRACE-estimated mass trend, the data-model combination explains not only the altimetry global mean SLR but also its regional trends fairly well. The deep ocean warming is mostly prevalent in the Atlantic and Indian oceans, and along the Antarctic Circumpolar Current, suggesting a strong relation to the oceanic circulation and dynamics. Its comparison with available bottom water measurements shows reasonably good agreement, indicating that deep ocean warming below 700 m might have contributed 1.1 mm/yr to the global mean SLR or one-third of the altimeter-observed rate of 3.11 ± 0.6 mm/yr over 1993-2008.

  11. Numerical model of crustal accretion and cooling rates of fast-spreading mid-ocean ridges

    NASA Astrophysics Data System (ADS)

    Machetel, P.; Garrido, C. J.

    2013-10-01

    We designed a thermo-mechanical numerical model for fast-spreading mid-ocean ridge with variable viscosity, hydrothermal cooling, latent heat release, sheeted dyke layer, and variable melt intrusion possibilities. The model allows for modulating several accretion possibilities such as the "gabbro glacier" (G), the "sheeted sills" (S) or the "mixed shallow and MTZ lenses" (M). These three crustal accretion modes have been explored assuming viscosity contrasts of 2 to 3 orders of magnitude between strong and weak phases and various hydrothermal cooling conditions depending on the cracking temperatures value. Mass conservation (stream-function), momentum (vorticity) and temperature equations are solved in 2-D cartesian geometry using 2-D, alternate direction, implicit and semi-implicit finite-difference scheme. In a first step, an Eulerian approach is used solving iteratively the motion and temperature equations until reaching steady states. With this procedure, the temperature patterns and motions that are obtained for the various crustal intrusion modes and hydrothermal cooling hypotheses display significant differences near the mid-ocean ridge axis. In a second step, a Lagrangian approach is used, recording the thermal histories and cooling rates of tracers travelling from the ridge axis to their final emplacements in the crust far from the mid-ocean ridge axis. The results show that the tracer's thermal histories are depending on the temperature patterns and the crustal accretion modes near the mid-ocean ridge axis. The instantaneous cooling rates obtained from these thermal histories betray these discrepancies and might therefore be used to characterize the crustal accretion mode at the ridge axis. These deciphering effects are even more pronounced if we consider the average cooling rates occurring over a prescribed temperature range. Two situations were tested at 1275-1125 °C and 1050-850 °C. The first temperature range covers mainly the crystallization range

  12. Wave-induced upper-ocean mixing in a climate model of intermediate complexity

    NASA Astrophysics Data System (ADS)

    Babanin, Alexander V.; Ganopolski, Andrey; Phillips, William R. C.

    Climate modelling, to a great extent, is based on simulating air-sea interactions at larger scales. Small-scale interactions and related phenomena, such as wind-generated waves and wave-induced turbulence are sub-grid processes for such models and therefore cannot be simulated explicitly. In the meantime, the waves play the principal role in the upper-ocean mixing. This role is usually parameterized, mostly to account for the wave-breaking turbulence and to describe downward diffusion of such turbulence. The main purpose of the paper is to demonstrate that an important physical mechanism, that is the ocean mixing due to waves, is presently missing in the climate models, whereas the effect of this mixing is significant. It is argued that the mixing role of the surface waves is not limited to the mere transfer of the wind stress and energy across the ocean interface by means of breaking and surface currents. The waves facilitate two processes in the upper-ocean which can deliver turbulence to the depths of the order of 100 m directly, rather than diffusing it from the surface. The first process is due to capacity of the waves to generate turbulence, unrelated to the wave breaking, at all depths where the wave orbital motion is significant. The second process is Langmuir circulation, triggered by the waves. Such wave-controlled mixing should cause seasonal variations of the mixed-layer depth, which regulates the thermodynamic balance between the ocean and atmosphere. In the present paper, these variations are parameterized in terms of the global winds. The variable mixed-layer depth is then introduced in the climate model of intermediated complexity CLIMBER-2 with a purpose of reproducing the pre-industrial climate. Comparisons are conducted with the NRL global atlas of the mixed layer, and performance of the wave-mixing parameterisations was found satisfactory in circumstances where the mixing is expected to be dominated by the wind-generated waves. It is shown that

  13. Digital adaptive controllers using second order models with transport lag

    NASA Technical Reports Server (NTRS)

    Joshi, S.; Kaufman, H.

    1975-01-01

    Design of a discrete optimal regulator requires the a priori knowledge of a mathematical model for the system of interest. Because a second-order model with transport lag is very amenable to control computations and because this type of model has been used previously to represent certain high order single input-single output processes, an adaptive controller was designed based upon adjustment of controls computed for such a model. An extended Kalman filter was utilized for tracking the model parameters which were subsequently used to update a set of optimal control gains. Favorable results were obtained in applying this procedure to the control of several examples including a ninth order nonlinear process.

  14. The energy balance over land and oceans: An assessment based on direct observations and CMIP5 climate models

    NASA Astrophysics Data System (ADS)

    Wild, Martin; Folini, Doris; Hakuba, Maria; Schär, Christoph; Seneviratne, Sonia; Kato, Seiji; Rutan, David; Ammann, Christof; Wood, Eric; König-Langlo, Gert

    2015-04-01

    The energy budgets over land and oceans are still afflicted with considerable uncertainties, despite their key importance for terrestrial and maritime climates. We evaluate these budgets as represented in 43 CMIP5 climate models with direct observations from both surface and space and identify substantial biases, particularly in the surface fluxes of downward solar and thermal radiation. These flux biases in the various models are then linearly related to their respective land and ocean means to infer best estimates for present day downward solar and thermal radiation over land and oceans. Over land, where most direct observations are available to constrain the surface fluxes, we obtain 184 and 306 Wm-2 for solar and thermal downward radiation, respectively. Over oceans, with weaker observational constraints, corresponding estimates are around 185 and 356 Wm-2. Considering additionally surface albedo and emissivity, we infer a surface absorbed solar and net thermal radiation of 136 and -66 Wm-2 over land, and 170 and -53 Wm-2 over oceans, respectively. The surface net radiation is thus estimated at 70 Wm-2 over land and 117 Wm-2 over oceans, which may impose additional constraints on the poorly known sensible/latent heat flux magnitudes, estimated here near 32/38 Wm-2 over land, and 16/100 Wm-2 over oceans. Estimated uncertainties are on the order of 10 and 5 Wm-2 for most surface and TOA fluxes, respectively. By combining these surface budgets with satellite-determined TOA budgets we quantify the atmospheric energy budgets as residuals (including ocean to land transports), and revisit the global mean energy balance. This study has recently been published online in Climate Dynamics.

  15. Further development and testing of a second-order bulk boundary layer model. Master's thesis

    SciTech Connect

    Krasner, R.D.

    1993-05-03

    A one-layer bulk boundary layer model is developed. The model predicts the mixed layer values of the potential temperature, mixing ratio, and u- and v-momentum. The model also predicts the depth of the boundary layer and the vertically integrated turbulence kinetic energy (TKE). The TKE is determined using a second-order closure that relates the rate of dissipation to the TKE. The fractional area covered by rising motion sigma and the entrainment rate (E) are diagnostically determined. The model is used to study the clear convective boundary layer (CBL) using data from the Wangara, Australia boundary layer experiment. The Wangara data is also used as an observation base to validate model results. A further study is accomplished by simulating the planetary boundary layer (PBL) over an ocean surface. This study is designed to find the steady-state solutions of the prognostic variable.

  16. Multivariable frequency weighted model order reduction for control synthesis

    NASA Technical Reports Server (NTRS)

    Schmidt, David K.

    1989-01-01

    Quantitative criteria are presented for model simplification, or order reduction, such that the reduced order model may be used to synthesize and evaluate a control law, and the stability robustness obtained using the reduced order model will be preserved when controlling the full-order system. The error introduced due to model simplification is treated as modeling uncertainty, and some of the results from multivariate robustness theory are brought to bear on the model simplification problem. A numerical procedure developed previously is shown to lead to results that meet the necessary criteria. The procedure is applied to reduce the model of a flexible aircraft. Also, the importance of the control law itself, in meeting the modeling criteria, is underscored. An example is included that demonstrates that an apparently robust control law actually amplifies modest modeling errors in the critical frequency region, and leads to undesirable results. The cause of this problem is associated with the canceling of lightly damped transmission zeroes in the plant. An attempt is made to expand on some of the earlier results and to further clarify the theoretical basis behind the proposed methodology.

  17. Order reduction for a model of marine bacteriophage evolution

    NASA Astrophysics Data System (ADS)

    Pagliarini, Silvia; Korobeinikov, Andrei

    2017-02-01

    A typical mechanistic model of viral evolution necessary includes several time scales which can differ by orders of magnitude. Such a diversity of time scales makes analysis of these models difficult. Reducing the order of a model is highly desirable when handling such a model. A typical approach applied to such slow-fast (or singularly perturbed) systems is the time scales separation technique. Constructing the so-called quasi-steady-state approximation is the usual first step in applying the technique. While this technique is commonly applied, in some cases its straightforward application can lead to unsatisfactory results. In this paper we construct the quasi-steady-state approximation for a model of evolution of marine bacteriophages based on the Beretta-Kuang model. We show that for this particular model the quasi-steady-state approximation is able to produce only qualitative but not quantitative fit.

  18. A coupled ice-ocean model of upwelling in the marginal ice zone

    NASA Technical Reports Server (NTRS)

    Roed, L. P.; Obrien, J. J.

    1983-01-01

    A dynamical coupled ice-ocean numerical model for the marginal ice zone (MIZ) is suggested and used to study upwelling dynamics in the MIZ. The nonlinear sea ice model has a variable ice concentration and includes internal ice stress. The model is forced by stresses on the air/ocean and air/ice surfaces. The main coupling between the ice and the ocean is in the form of an interfacial stress on the ice/ocean interface. The ocean model is a linear reduced gravity model. The wind stress exerted by the atmosphere on the ocean is proportional to the fraction of open water, while the interfacial stress ice/ocean is proportional to the concentration of ice. A new mechanism for ice edge upwelling is suggested based on a geostrophic equilibrium solution for the sea ice medium. The upwelling reported in previous models invoking a stationary ice cover is shown to be replaced by a weak downwelling due to the ice motion. Most of the upwelling dynamics can be understood by analysis of the divergence of the across ice edge upper ocean transport. On the basis of numerical model, an analytical model is suggested that reproduces most of the upwelling dynamics of the more complex numerical model.

  19. Seasonal Distributions of Global Ocean Chlorophyll and Nutrients: Analysis with a Coupled Ocean General Circulation Biogeochemical, and Radiative Model

    NASA Technical Reports Server (NTRS)

    Gregg, Watson W.

    1999-01-01

    A coupled general ocean circulation, biogeochemical, and radiative model was constructed to evaluate and understand the nature of seasonal variability of chlorophyll and nutrients in the global oceans. The model is driven by climatological meteorological conditions, cloud cover, and sea surface temperature. Biogeochemical processes in the model are determined from the influences of circulation and turbulence dynamics, irradiance availability, and the interactions among three functional phytoplankton groups (diatoms, chorophytes, and picoplankton) and three nutrient groups (nitrate, ammonium, and silicate). Phytoplankton groups are initialized as homogeneous fields horizontally and vertically, and allowed to distribute themselves according to the prevailing conditions. Basin-scale model chlorophyll results are in very good agreement with CZCS pigments in virtually every global region. Seasonal variability observed in the CZCS is also well represented in the model. Synoptic scale (100-1000 km) comparisons of imagery are also in good conformance, although occasional departures are apparent. Agreement of nitrate distributions with in situ data is even better, including seasonal dynamics, except for the equatorial Atlantic. The good agreement of the model with satellite and in situ data sources indicates that the model dynamics realistically simulate phytoplankton and nutrient dynamics on synoptic scales. This is especially true given that initial conditions are homogenous chlorophyll fields. The success of the model in producing a reasonable representation of chlorophyll and nutrient distributions and seasonal variability in the global oceans is attributed to the application of a generalized, processes-driven approach as opposed to regional parameterization, and the existence of multiple phytoplankton groups with different physiological and physical properties. These factors enable the model to simultaneously represent the great diversity of physical, biological

  20. Modeling Surface Water Transport in the Central Pacific Ocean With 129I Records From Coral Skeletons

    NASA Astrophysics Data System (ADS)

    Beck, W.; Biddulph, D. L.; Russell, J. L.; Burr, G. S.; Jull, T. J.; Correge, T.; Roeder, B.

    2008-12-01

    129I occurs naturally in extremely low abundance via cosmic ray interactions in the atmosphere as well as by spontaneous fission of uranium. Oceanic concentrations of 129I have risen by several orders of magnitude during the last half century largely from environmental pollution coming from several point-source nuclear fuel reprocessing plants. In the Pacific basin, much of the increase has apparently come from the Hanford Nuclear reprocessing plant in the United States, with iodine primarily arriving via the Columbia River. Coral skeletons preserve records of 129I concentration of the surface waters from which they were deposited, yielding records with annual resolution or better. We will present three such records from different locations in the Pacific Ocean: the Solomon Islands, Easter Island and Clipperton Atoll. For this study, drill cores from living massive coral skeletons of the species Porites Lobata were collected from these sites. 129I/127I values were measured using accelerator mass spectrometry (AMS) at the University of Arizona with an NEC 3 MV Pelletron accelerator. Results from the analysis of the corals will be compared to the distribution of other mixed-layer tracers (chloro-fluorocarbons and tritium) collected during the World Ocean Circulation Experiment cruises conducted between 1990 and 2002. The 129I/127I records observed in these corals will also be compared to tracer transit time calculations determined from a 20th century simulation of the GFDL coupled-climate passive-tracer model.

  1. A High-Order Multiscale Global Atmospheric Model

    NASA Astrophysics Data System (ADS)

    Nair, R. D.

    2015-12-01

    The High-Order Method Modeling Environment (HOMME), developed at NCAR, is a petascale hydrostatic framework, which employs the cubed-sphere grid system and high-order continuous or discontinuous Galerkin (DG) methods. Recently, the HOMME framework is being extended to a non-hydrostatic dynamical core, named as the "High-Order Multiscale Atmospheric Model (HOMAM)." The spatial discretization for HOMAM is based on DG or high-order finite-volume methods. Orography is handled by the terrain-following height-based coordinate system. To alleviate the stringent CFL stability requirement resulting from the vertical aspects of the dynamics, an operator-splitting time integration scheme based on the horizontally explicit and vertically implicit (HEVI) philosophy is adopted for HOMAM. Preliminary results with the benchmark test cases proposed in the Dynamical Core Model Intercomparison project (DCMIP) test-suite will be presented in the seminar.

  2. A High-Order Multiscale Global Atmospheric Model

    NASA Astrophysics Data System (ADS)

    Nair, Ram

    2016-04-01

    The High-Order Method Modeling Environment (HOMME), developed at NCAR, is a petascale hydrostatic framework, which employs the cubed-sphere grid system and high-order continuous or discontinuous Galerkin (DG) methods. Recently, the HOMME framework is being extended to a non-hydrostatic dynamical core, named as the "High-Order Multiscale Atmospheric Model (HOMAM)." The spatial discretization is based on DG or high-order finite-volume methods. Orography is handled by the terrain-following height-based coordinate system. To alleviate the stringent CFL stability requirement resulting from the vertical aspects of the dynamics, an operator-splitting time integration scheme based on the horizontally explicit and vertically implicit (HEVI) philosophy is adopted for HOMAM. Preliminary results with the benchmark test cases proposed in the Dynamical Core Model Intercomparison project (DCMIP) test-suite will be presented in the seminar.

  3. Emergent smectic order in simple active particle models

    NASA Astrophysics Data System (ADS)

    Romanczuk, Pawel; Chaté, Hugues; Chen, Leiming; Ngo, Sandrine; Toner, John

    2016-06-01

    Novel ‘smectic-P’ behavior, in which self-propelled particles form rows and move on average along them, occurs generically within the orientationally ordered phase of simple models that we simulate. Both apolar (head-tail symmetric) and polar (head-tail asymmetric) models with aligning and repulsive interactions exhibit slow algebraic decay of smectic order with system size up to some finite length scale, after which faster decay occurs. In the apolar case, this scale is that of an undulation instability of the rows. In the polar case, this instability is absent, but traveling fluctuations disrupt the rows in large systems and motion and smectic order may spontaneously globally rotate. These observations agree with a new hydrodynamic theory which we present here. Variants of our models also exhibit active smectic ‘A’ and ‘C’ order, with motion orthogonal and oblique to the layers respectively.

  4. Improving Estimates of Atmosphere-Ocean Greenhouse Gas Fluxes for Earth-System Modelling

    NASA Astrophysics Data System (ADS)

    Vieira, V. M. N. C. S.; Sahlee, E.; Jurus, P.; Clementi, E.; Pettersson, H.; Mateus, M.

    2016-08-01

    Accurate estimates of atmosphere-ocean balances and fluxes of greenhouse gases and aerosols are fundamental for Earth-System models forecasting the climate change, and for Earth Observation estimates of oceanic sinks and sources coupling satellite imagery with reverse modelling. The standard formulations are 24 and 36 years old, and recent alternatives have emerged. We developed a framework congregating the geophysical processes involved, customizable with alternative formulations, and that can be used as basis for novel couplers of atmospheric and oceanographic model components. We tested it with fine resolution data from the European coastal ocean. Although the solubility formulations agreed well, their minor divergences yielded differences of many tons of greenhouse gases dissolved at the ocean surface. The transfer velocities largely mismatched their estimates, in part consequence of the standard formulation not considering factors that were proved determinant at the coastal ocean. Climate Change research requires further calibration and validation of atmosphere-ocean interactions.

  5. Natural ocean carbon cycle sensitivity to parameterizations of the recycling in a climate model

    NASA Astrophysics Data System (ADS)

    Romanou, A.; Romanski, J.; Gregg, W. W.

    2014-02-01

    Sensitivities of the oceanic biological pump within the GISS (Goddard Institute for Space Studies ) climate modeling system are explored here. Results are presented from twin control simulations of the air-sea CO2 gas exchange using two different ocean models coupled to the same atmosphere. The two ocean models (Russell ocean model and Hybrid Coordinate Ocean Model, HYCOM) use different vertical coordinate systems, and therefore different representations of column physics. Both variants of the GISS climate model are coupled to the same ocean biogeochemistry module (the NASA Ocean Biogeochemistry Model, NOBM), which computes prognostic distributions for biotic and abiotic fields that influence the air-sea flux of CO2 and the deep ocean carbon transport and storage. In particular, the model differences due to remineralization rate changes are compared to differences attributed to physical processes modeled differently in the two ocean models such as ventilation, mixing, eddy stirring and vertical advection. GISSEH(GISSER) is found to underestimate mixed layer depth compared to observations by about 55% (10%) in the Southern Ocean and overestimate it by about 17% (underestimate by 2%) in the northern high latitudes. Everywhere else in the global ocean, the two models underestimate the surface mixing by about 12-34%, which prevents deep nutrients from reaching the surface and promoting primary production there. Consequently, carbon export is reduced because of reduced production at the surface. Furthermore, carbon export is particularly sensitive to remineralization rate changes in the frontal regions of the subtropical gyres and at the Equator and this sensitivity in the model is much higher than the sensitivity to physical processes such as vertical mixing, vertical advection and mesoscale eddy transport. At depth, GISSER, which has a significant warm bias, remineralizes nutrients and carbon faster thereby producing more nutrients and carbon at depth, which

  6. Natural Ocean Carbon Cycle Sensitivity to Parameterizations of the Recycling in a Climate Model

    NASA Technical Reports Server (NTRS)

    Romanou, A.; Romanski, J.; Gregg, W. W.

    2014-01-01

    Sensitivities of the oceanic biological pump within the GISS (Goddard Institute for Space Studies ) climate modeling system are explored here. Results are presented from twin control simulations of the air-sea CO2 gas exchange using two different ocean models coupled to the same atmosphere. The two ocean models (Russell ocean model and Hybrid Coordinate Ocean Model, HYCOM) use different vertical coordinate systems, and therefore different representations of column physics. Both variants of the GISS climate model are coupled to the same ocean biogeochemistry module (the NASA Ocean Biogeochemistry Model, NOBM), which computes prognostic distributions for biotic and abiotic fields that influence the air-sea flux of CO2 and the deep ocean carbon transport and storage. In particular, the model differences due to remineralization rate changes are compared to differences attributed to physical processes modeled differently in the two ocean models such as ventilation, mixing, eddy stirring and vertical advection. GISSEH(GISSER) is found to underestimate mixed layer depth compared to observations by about 55% (10 %) in the Southern Ocean and overestimate it by about 17% (underestimate by 2%) in the northern high latitudes. Everywhere else in the global ocean, the two models underestimate the surface mixing by about 12-34 %, which prevents deep nutrients from reaching the surface and promoting primary production there. Consequently, carbon export is reduced because of reduced production at the surface. Furthermore, carbon export is particularly sensitive to remineralization rate changes in the frontal regions of the subtropical gyres and at the Equator and this sensitivity in the model is much higher than the sensitivity to physical processes such as vertical mixing, vertical advection and mesoscale eddy transport. At depth, GISSER, which has a significant warm bias, remineralizes nutrients and carbon faster thereby producing more nutrients and carbon at depth, which

  7. Spreading and wandering of Gaussian-Schell model laser beams in an anisotropic turbulent ocean

    NASA Astrophysics Data System (ADS)

    Wu, Yuqian; Zhang, Yixin; Zhu, Yun; Hu, Zhengda

    2016-09-01

    The effect of anisotropic turbulence on the spreading and wandering of Gaussian-Schell model (GSM) laser beams propagating in an ocean is studied. The long-term spreading of a GSM beam propagating through the paraxial channel of a turbulent ocean is also developed. Expressions of random wander for such laser beams are derived in an anisotropic turbulent ocean based on the extended Huygens-Fresnel principle. We investigate the influence of parameters in a turbulent ocean on the beam wander and spreading. Our results indicate that beam spreading and random beam wandering are smaller without considering the anisotropy of turbulence in the oceanic channel. Salinity fluctuation has a greater contribution to both the beam spreading and beam wander than that of temperature fluctuations in a turbulent ocean. Our results could be helpful for designing a free-space optical wireless communication system in an oceanic environment.

  8. A simple method for improving the time-stepping accuracy in atmosphere and ocean models

    NASA Astrophysics Data System (ADS)

    Williams, P. D.

    2012-12-01

    In contemporary numerical simulations of the atmosphere and ocean, evidence suggests that time-stepping errors may be a significant component of total model error, on both weather and climate time-scales. This presentation will review the available evidence, and will then suggest a simple but effective method for substantially improving the time-stepping numerics at no extra computational expense. A common time-stepping method in atmosphere and ocean models is the leapfrog scheme combined with the Robert-Asselin (RA) filter. This method is used in the following models (and many more): ECHAM, MAECHAM, MM5, CAM, MESO-NH, HIRLAM, KMCM, LIMA, SPEEDY, IGCM, PUMA, COSMO, FSU-GSM, FSU-NRSM, NCEP-GFS, NCEP-RSM, NSEAM, NOGAPS, RAMS, and CCSR/NIES-AGCM. Although the RA filter controls the time-splitting instability, it also introduces non-physical damping and reduces the accuracy. This presentation proposes a simple modification to the RA filter, which has become known as the RAW filter (Williams 2009, 2011). When used in conjunction with the leapfrog scheme, the RAW filter eliminates the non-physical damping and increases the amplitude accuracy by two orders, yielding third-order accuracy. (The phase accuracy remains second-order.) The RAW filter can easily be incorporated into existing models, typically via the insertion of just a single line of code. Better simulations are obtained at no extra computational expense. Results will be shown from recent implementations of the RAW filter in various models, including SPEEDY and COSMO. For example, in SPEEDY, the skill of weather forecasts is found to be significantly improved. In particular, in tropical surface pressure predictions, five-day forecasts made using the RAW filter have approximately the same skill as four-day forecasts made using the RA filter (Amezcua, Kalnay & Williams 2011). These improvements are encouraging for the use of the RAW filter in other atmosphere and ocean models. References PD Williams (2009) A

  9. Coastal ocean research in sub-Saharan Africa: towards operational oceanography using satellites, in situ measurements and numerical models

    NASA Astrophysics Data System (ADS)

    Shillington, Frank

    Sub-Saharan Africa is greatly influenced by major western boundary currents of the Indian Ocean, Agulhas Current and the Somali Current (for six months of the year), and the major eastern boundary upwelling current systems of the Atlantic Ocean, with their concomitant nu-trient rich upwelling ecosystems which support large fisheries: the Benguela Upwelling System and the Canary Upwelling System. The location of the tip of placecountry-regionSouth Africa is unique in the world oceans, since it is such the only place where a warm western boundary current can interact with a cold upwelling ecosystem. In addition, the Agulhas Current is unique in that it retroflects 80% of its large volume flux back into the placeIndian Ocean. The interocean transport of warm thermocline water from the Indian to the placeAtlantic ocean is of global importance. Satellite observations of temperature, chlorophyll, sea surface height, and wind and waves have elucidated many of these first order processes. Numerical ocean models forced and constrained by satellite measurements are being increasingly used to place operational oceanography on a sound footing. Partnerships with African and northern hemisphere collaborators (e.g. the new Norwegian Nansen-Tutu Centre for Marine Research, PlaceNamePrinceton PlaceTypeUniversity) will enhance operational oceanography around placeAfrica to the benefit of all its inhabitants. All of the above aspects will be discussed, with specific examples of local innovative space borne techniques.

  10. Higher-Order Latent Trait Models for Cognitive Diagnosis

    ERIC Educational Resources Information Center

    de la Torre, Jimmy; Douglas, Jeffrey A.

    2004-01-01

    Higher-order latent traits are proposed for specifying the joint distribution of binary attributes in models for cognitive diagnosis. This approach results in a parsimonious model for the joint distribution of a high-dimensional attribute vector that is natural in many situations when specific cognitive information is sought but a less informative…

  11. Statistically accurate low-order models for uncertainty quantification in turbulent dynamical systems.

    PubMed

    Sapsis, Themistoklis P; Majda, Andrew J

    2013-08-20

    A framework for low-order predictive statistical modeling and uncertainty quantification in turbulent dynamical systems is developed here. These reduced-order, modified quasilinear Gaussian (ROMQG) algorithms apply to turbulent dynamical systems in which there is significant linear instability or linear nonnormal dynamics in the unperturbed system and energy-conserving nonlinear interactions that transfer energy from the unstable modes to the stable modes where dissipation occurs, resulting in a statistical steady state; such turbulent dynamical systems are ubiquitous in geophysical and engineering turbulence. The ROMQG method involves constructing a low-order, nonlinear, dynamical system for the mean and covariance statistics in the reduced subspace that has the unperturbed statistics as a stable fixed point and optimally incorporates the indirect effect of non-Gaussian third-order statistics for the unperturbed system in a systematic calibration stage. This calibration procedure is achieved through information involving only the mean and covariance statistics for the unperturbed equilibrium. The performance of the ROMQG algorithm is assessed on two stringent test cases: the 40-mode Lorenz 96 model mimicking midlatitude atmospheric turbulence and two-layer baroclinic models for high-latitude ocean turbulence with over 125,000 degrees of freedom. In the Lorenz 96 model, the ROMQG algorithm with just a single mode captures the transient response to random or deterministic forcing. For the baroclinic ocean turbulence models, the inexpensive ROMQG algorithm with 252 modes, less than 0.2% of the total, captures the nonlinear response of the energy, the heat flux, and even the one-dimensional energy and heat flux spectra.

  12. The Regional Earth System Model (RegESM) using RegCM4 coupled with the MITgcm ocean model: First assessments over the MED-CORDEX domain

    NASA Astrophysics Data System (ADS)

    Mariotti, Laura; Utku Turunçoǧlu, Ufuk; Farneti, Riccardo; Sannino, Gianmaria; Vittoria Struglia, Maria; Carillo, Adriana; Giorgi, Filippo

    2016-04-01

    In the framework of global climate studies, there is an increasingly growing concern about the vulnerability of the Mediterranean region, where high population density and intense exploitation activities pose severe questions on the sustainability of terrestrial water management, both for the present and the future. Ocean modeling studies suggest that the Mediterranean thermohaline circulation could be weakened in conditions of global greenhouse warming, an event which would undoubtedly affect regional climate, possibly triggering global feedback processes. Experiments with the atmosphere-ocean coupled system confirmed that a good comprehension of Mediterranean processes requires the explicit inclusion of the feedbacks between the atmospheric and the oceanic components, thus achieving a complete, fully coupled description of the Mediterranean hydrological cycle, at the same time gaining new insights in our current ability to reproduce the atmospheric hydrological processes and to close the hydrological balance. These issues are addressed by the upgraded PROTHEUS system which was jointly developed by ENEA and ICTP. Here we present a first evaluation of the performances of the new PROTHEUS system (called PROTHEUS 2.0) composed by the regional climate model RegCM4 (Giorgi et al. 2012) coupled with both the ocean model MITgcm (Marshall J. et al. 1997a,b) and the HD river model (Max-Planck's HD model; Hagemann and Dümenil, 1998) using RegESM (Regional Earth System Model) as a driver. The three-component (atmosphere, ocean and river routing) fully coupled model exchanges sea surface temperature (SST) from the ocean to the atmospheric model, surface wind stress, energy and freshwater fluxes from the atmosphere to the ocean model, surface and sub-surface runoff from the atmospheric component to the river routing model (Max-Planck's HD model; Hagemann and Dümenil, 1998). In order to have water conservation within the system, the river routing component sends the

  13. Reproducibility and Transparency in Ocean-Climate Modeling

    NASA Astrophysics Data System (ADS)

    Hannah, N.; Adcroft, A.; Hallberg, R.; Griffies, S. M.

    2015-12-01

    Reproducibility is a cornerstone of the scientific method. Within geophysical modeling and simulation achieving reproducibility can be difficult, especially given the complexity of numerical codes, enormous and disparate data sets, and variety of supercomputing technology. We have made progress on this problem in the context of a large project - the development of new ocean and sea ice models, MOM6 and SIS2. Here we present useful techniques and experience.We use version control not only for code but the entire experiment working directory, including configuration (run-time parameters, component versions), input data and checksums on experiment output. This allows us to document when the solutions to experiments change, whether due to code updates or changes in input data. To avoid distributing large input datasets we provide the tools for generating these from the sources, rather than provide raw input data.Bugs can be a source of non-determinism and hence irreproducibility, e.g. reading from or branching on uninitialized memory. To expose these we routinely run system tests, using a memory debugger, multiple compilers and different machines. Additional confidence in the code comes from specialised tests, for example automated dimensional analysis and domain transformations. This has entailed adopting a code style where we deliberately restrict what a compiler can do when re-arranging mathematical expressions.In the spirit of open science, all development is in the public domain. This leads to a positive feedback, where increased transparency and reproducibility makes using the model easier for external collaborators, who in turn provide valuable contributions. To facilitate users installing and running the model we provide (version controlled) digital notebooks that illustrate and record analysis of output. This has the dual role of providing a gross, platform-independent, testing capability and a means to documents model output and analysis.

  14. Transonic limit cycle oscillation analysis using reduced order aerodynamic models

    NASA Astrophysics Data System (ADS)

    Dowell, E. H.; Thomas, J. P.; Hall, K. C.

    2004-01-01

    Limit cycle oscillations have been observed in flight operations of modern aircraft, wind tunnel experiments and mathematical models. Both fluid and structural nonlinearities are thought to contribute to these phenomena. With recent advances in reduced order aerodynamic modeling, it is now feasible to analyze limit cycle oscillations that may occur in transonic flow including the effects of structural and fluid nonlinearities. In this paper an airfoil with control surface freeplay (a common structural nonlinearity) is used to investigate transonic flutter and limit cycle oscillations. The reduced order aerodynamic model used in this paper assumes the shock motion is small and in proportion to the structural motions.

  15. A generalized model of pelagic biogeochemistry for the global ocean ecosystem. Part I: Theory

    NASA Astrophysics Data System (ADS)

    Vichi, M.; Pinardi, N.; Masina, S.

    2007-01-01

    The set of equations for global ocean biogeochemistry deterministic models have been formulated in a comprehensive and unified form in order to use them in numerical simulations of the marine ecosystem for climate change studies (PELAGOS, PELAgic biogeochemistry for Global Ocean Simulations). The fundamental approach stems from the representation of marine trophic interactions and major biogeochemical cycles introduced in the European Regional Seas Ecosystem Model (ERSEM). Our theoretical formulation revisits and generalizes the stoichiometric approach of ERSEM by defining the state variables as Chemical Functional Families (CFF). CFFs are further subdivided into living, non-living and inorganic components. Living CFFs are the basis for the definition of Living Functional Groups, the biomass-based functional prototype of the real organisms. Both CFFs and LFGs are theoretical constructs which allow us to relate measurable properties of marine biogeochemistry to the state variables used in deterministic models. This approach is sufficiently generic that may be used to describe other existing biomass-based ecosystem model.

  16. How well do global ocean biogeochemistry models simulate dissolved iron distributions?

    NASA Astrophysics Data System (ADS)

    Tagliabue, Alessandro; Aumont, Olivier; DeAth, Ros; Dunne, John P.; Dutkiewicz, Stephanie; Galbraith, Eric; Misumi, Kazuhiro; Moore, J. Keith; Ridgwell, Andy; Sherman, Elliot; Stock, Charles; Vichi, Marcello; Völker, Christoph; Yool, Andrew

    2016-02-01

    Numerical models of ocean biogeochemistry are relied upon to make projections about the impact of climate change on marine resources and test hypotheses regarding the drivers of past changes in climate and ecosystems. In large areas of the ocean, iron availability regulates the functioning of marine ecosystems and hence the ocean carbon cycle. Accordingly, our ability to quantify the drivers and impacts of fluctuations in ocean ecosystems and carbon cycling in space and time relies on first achieving an appropriate representation of the modern marine iron cycle in models. When the iron distributions from 13 global ocean biogeochemistry models are compared against the latest oceanic sections from the GEOTRACES program, we find that all models struggle to reproduce many aspects of the observed spatial patterns. Models that reflect the emerging evidence for multiple iron sources or subtleties of its internal cycling perform much better in capturing observed features than their simpler contemporaries, particularly in the ocean interior. We show that the substantial uncertainty in the input fluxes of iron results in a very wide range of residence times across models, which has implications for the response of ecosystems and global carbon cycling to perturbations. Given this large uncertainty, iron fertilization experiments based on any single current generation model should be interpreted with caution. Improvements to how such models represent iron scavenging and also biological cycling are needed to raise confidence in their projections of global biogeochemical change in the ocean.

  17. Model-based processing for shallow ocean environments: The broadband problem

    SciTech Connect

    Candy, J.V.; Sullivan, E.J.

    1996-01-31

    Most acoustic sources found is the ocean environmental are spatially complex and broadband. When propagating in a shallow ocean these source characteristics complicate the analysis of received acoustic data considerably. The enhancement of broadband acoustic pressure- field measurements using a vertical array is discussed. Here a model- based approach is developed for a broadband source using a normal- mode propagation model.

  18. A small parameter model of circulation in a homogeoneous baroclinic ocean

    NASA Technical Reports Server (NTRS)

    Borisenkov, Y. P.

    1974-01-01

    A small parameter model of circulation in a homogeneous baroclinic ocean is presented. The principles common to the construction of small parameter models and certain energetic principles developed in connection with atmospheric processes are made use of. These principles were applied in the study of processes in a baroclinic ocean.

  19. Evaluation of Arctic Sea Ice Thickness Simulated by Arctic Ocean Model Intercomparison Project Models

    NASA Technical Reports Server (NTRS)

    Johnson, Mark; Proshuntinsky, Andrew; Aksenov, Yevgeny; Nguyen, An T.; Lindsay, Ron; Haas, Christian; Zhang, Jinlun; Diansky, Nikolay; Kwok, Ron; Maslowski, Wieslaw; Hakkinen, Sirpa; Ashik, Igor; De Cuevas, Beverly

    2012-01-01

    Six Arctic Ocean Model Intercomparison Project model simulations are compared with estimates of sea ice thickness derived from pan-Arctic satellite freeboard measurements (2004-2008); airborne electromagnetic measurements (2001-2009); ice draft data from moored instruments in Fram Strait, the Greenland Sea, and the Beaufort Sea (1992-2008) and from submarines (1975-2000); and drill hole data from the Arctic basin, Laptev, and East Siberian marginal seas (1982-1986) and coastal stations (1998-2009). Despite an assessment of six models that differ in numerical methods, resolution, domain, forcing, and boundary conditions, the models generally overestimate the thickness of measured ice thinner than approximately 2 mand underestimate the thickness of ice measured thicker than about approximately 2m. In the regions of flat immobile landfast ice (shallow Siberian Seas with depths less than 25-30 m), the models generally overestimate both the total observed sea ice thickness and rates of September and October ice growth from observations by more than 4 times and more than one standard deviation, respectively. The models do not reproduce conditions of fast ice formation and growth. Instead, the modeled fast ice is replaced with pack ice which drifts, generating ridges of increasing ice thickness, in addition to thermodynamic ice growth. Considering all observational data sets, the better correlations and smaller differences from observations are from the Estimating the Circulation and Climate of the Ocean, Phase II and Pan-Arctic Ice Ocean Modeling and Assimilation System models.

  20. Modeling and Measurement of Ocean Generated Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Liang, R.; Avera, W. E.; Nelson, J.; Brozena, J. M.

    2011-12-01

    -track gradient. Total-field compensated and edited data from each aircraft and the magnetic base-station data were low-pass filtered and sub-sampled to 4Hz for analysis. Data from the magnetic base-stations exhibit good coherence, as do the data from the ocean-bottom magnetometers. After correction for the geomagnetic component, the two aircraft residuals matched quite closely in both amplitude and phase in many places, but in other places the phase match was poor. This produced an overall poor coherence between the two residuals. However, cross-spectral analysis showed that there was a statistical correlation between the two aircraft residuals in the frequency band 0.02-0.05 Hz (5000-2000 m wavelength for an aircraft flying at 100 m/s). Both the amplitude (0.1-0.2 nT) and wavelength were consistent with predictions computed from the 3-D water velocities and conductivity from the ADCP using a simple model. The predicted undersea magnetic fields correlated well with the measured undersea magnetometer fields at times, but they rarely matched at the "wiggle-for-wiggle" level. More often, it was the statistics that correlated well.

  1. First-Order Frameworks for Managing Models in Engineering Optimization

    NASA Technical Reports Server (NTRS)

    Alexandrov, Natlia M.; Lewis, Robert Michael

    2000-01-01

    Approximation/model management optimization (AMMO) is a rigorous methodology for attaining solutions of high-fidelity optimization problems with minimal expense in high- fidelity function and derivative evaluation. First-order AMMO frameworks allow for a wide variety of models and underlying optimization algorithms. Recent demonstrations with aerodynamic optimization achieved three-fold savings in terms of high- fidelity function and derivative evaluation in the case of variable-resolution models and five-fold savings in the case of variable-fidelity physics models. The savings are problem dependent but certain trends are beginning to emerge. We give an overview of the first-order frameworks, current computational results, and an idea of the scope of the first-order framework applicability.

  2. Reduced-Order Modeling: New Approaches for Computational Physics

    NASA Technical Reports Server (NTRS)

    Beran, Philip S.; Silva, Walter A.

    2001-01-01

    In this paper, we review the development of new reduced-order modeling techniques and discuss their applicability to various problems in computational physics. Emphasis is given to methods ba'sed on Volterra series representations and the proper orthogonal decomposition. Results are reported for different nonlinear systems to provide clear examples of the construction and use of reduced-order models, particularly in the multi-disciplinary field of computational aeroelasticity. Unsteady aerodynamic and aeroelastic behaviors of two- dimensional and three-dimensional geometries are described. Large increases in computational efficiency are obtained through the use of reduced-order models, thereby justifying the initial computational expense of constructing these models and inotivatim,- their use for multi-disciplinary design analysis.

  3. A Fractional Order Recovery SIR Model from a Stochastic Process.

    PubMed

    Angstmann, C N; Henry, B I; McGann, A V

    2016-03-01

    Over the past several decades, there has been a proliferation of epidemiological models with ordinary derivatives replaced by fractional derivatives in an ad hoc manner. These models may be mathematically interesting, but their relevance is uncertain. Here we develop an SIR model for an epidemic, including vital dynamics, from an underlying stochastic process. We show how fractional differential operators arise naturally in these models whenever the recovery time from the disease is power-law distributed. This can provide a model for a chronic disease process where individuals who are infected for a long time are unlikely to recover. The fractional order recovery model is shown to be consistent with the Kermack-McKendrick age-structured SIR model, and it reduces to the Hethcote-Tudor integral equation SIR model. The derivation from a stochastic process is extended to discrete time, providing a stable numerical method for solving the model equations. We have carried out simulations of the fractional order recovery model showing convergence to equilibrium states. The number of infecteds in the endemic equilibrium state increases as the fractional order of the derivative tends to zero.

  4. A Community Terrain-Following Ocean Modeling System (ROMS)

    DTIC Science & Technology

    2015-09-30

    forecasting that includes advanced data assimilation, ensemble prediction, and analysis tools for adaptive sampling and circulation dynamics...relocatable, coastal, coupled atmosphere-ocean forecasting applications. OBJECTIVES The main objectives of this project are: • To develop and test a...coupled atmosphere-ocean forecasting capabilities. • To develop advanced 4-dimension Variational (4D-Var) data assimilation capabilities and analysis

  5. Order reduction for an RNA virus evolution model.

    PubMed

    Korobeinikov, Andrei; Archibasov, Aleksei; Sobolev, Vladimir

    2015-10-01

    A mathematical or computational model in evolutionary biology should necessary combine several comparatively fast processes, which actually drive natural selection and evolution, with a very slow process of evolution. As a result, several very different time scales are simultaneously present in the model; this makes its analytical study an extremely difficult task. However, the significant difference of the time scales implies the existence of a possibility of the model order reduction through a process of time separation. In this paper we conduct the procedure of model order reduction for a reasonably simple model of RNA virus evolution reducing the original system of three integro-partial derivative equations to a single equation. Computations confirm that there is a good fit between the results for the original and reduced models.

  6. Bayesian Hierarchical Model Characterization of Model Error in Ocean Data Assimilation and Forecasts

    DTIC Science & Technology

    2012-09-28

    potential benefits from allowing switching between different process models in this setting. This will be greatly facilitated by the emulator approach...of sea surface height (SSH), SST, and phytoplankton ( chlorophyll ) data from 1998, 1999, 2000, and 2001. We then used remotely sensed SeaWiFS ocean

  7. Effects of vertical shear in modelling horizontal oceanic dispersion

    NASA Astrophysics Data System (ADS)

    Lanotte, A. S.; Corrado, R.; Palatella, L.; Pizzigalli, C.; Schipa, I.; Santoleri, R.

    2016-02-01

    The effect of vertical shear on the horizontal dispersion properties of passive tracer particles on the continental shelf of the South Mediterranean is investigated by means of observation and model data. In situ current measurements reveal that vertical gradients of horizontal velocities in the upper mixing layer decorrelate quite fast ( ˜ 1 day), whereas an eddy-permitting ocean model, such as the Mediterranean Forecasting System, tends to overestimate such decorrelation time because of finite resolution effects. Horizontal dispersion, simulated by the Mediterranean sea Forecasting System, is mostly affected by: (1) unresolved scale motions, and mesoscale motions that are largely smoothed out at scales close to the grid spacing; (2) poorly resolved time variability in the profiles of the horizontal velocities in the upper layer. For the case study we have analysed, we show that a suitable use of deterministic kinematic parametrizations is helpful to implement realistic statistical features of tracer dispersion in two and three dimensions. The approach here suggested provides a functional tool to control the horizontal spreading of small organisms or substance concentrations, and is thus relevant for marine biology, pollutant dispersion as well as oil spill applications.

  8. Toward an internal gravity wave spectrum in global ocean models

    NASA Astrophysics Data System (ADS)

    Müller, Malte; Arbic, Brian K.; Richman, James G.; Shriver, Jay F.; Kunze, Eric L.; Scott, Robert B.; Wallcraft, Alan J.; Zamudio, Luis

    2015-05-01

    High-resolution global ocean models forced by atmospheric fields and tides are beginning to display realistic internal gravity wave spectra, especially as model resolution increases. This paper examines internal waves in global simulations with 0.08° and 0.04° (~8 and 4 km) horizontal resolutions, respectively. Frequency spectra of internal wave horizontal kinetic energy in the North Pacific lie closer to observations in the 0.04° simulation than in the 0.08° simulation. The horizontal wave number and frequency (K-ω) kinetic energy spectra contain peaks in the semidiurnal tidal band and near-inertial band, along with a broadband frequency continuum aligned along the linear dispersion relations of low-vertical-mode internal waves. Spectral kinetic energy transfers describe the rate at which nonlinear mechanisms remove or supply kinetic energy in specific K-ω ranges. Energy is transferred out of low-mode inertial and semidiurnal internal waves into a broad continuum of higher-frequency and higher-wave number internal waves.

  9. Coupled model of INM-IO global ocean model, CICE sea ice model and SCM OIAS framework

    NASA Astrophysics Data System (ADS)

    Bayburin, Ruslan; Rashit, Ibrayev; Konstantin, Ushakov; Vladimir, Kalmykov; Gleb, Dyakonov

    2015-04-01

    Status of coupled Arctic model of ocean and sea ice is presented. Model consists of INM IO global ocean component of high resolution, Los Alamos National Laboratory CICE sea ice model and a framework SCM OIAS for the ocean-ice-atmosphere-land coupled modeling on massively-parallel architectures. Model is currently under development at the Institute of Numerical Mathematics (INM), Hydrometeorological Center (HMC) and P.P. Shirshov Institute of Oceanology (IO). Model is aimed at modeling of intra-annual variability of hydrodynamics in Arctic and. The computational characteristics of the world ocean-sea ice coupled model governed by SCM OIAS are presented. The model is parallelized using MPI technologies and currently can use efficiently up to 5000 cores. Details of programming implementation, computational configuration and physical phenomena parametrization are analyzed in terms of intercoupling complex. Results of five year computational experiment of sea ice, snow and ocean state evolution in Arctic region on tripole grid with horizontal resolution of 3-5 kilometers, closed by atmospheric forcing field from repeating "normal" annual course taken from CORE1 experiment data base are presented and analyzed in terms of the state of vorticity and warm Atlantic water expansion.

  10. Oceanic Carbon Dioxide Uptake in a Model of Century-Scale Global Warming

    PubMed

    Sarmiento; Le Quéré C

    1996-11-22

    In a model of ocean-atmosphere interaction that excluded biological processes, the oceanic uptake of atmospheric carbon dioxide (CO2) was substantially reduced in scenarios involving global warming relative to control scenarios. The primary reason for the reduced uptake was the weakening or collapse of the ocean thermohaline circulation. Such a large reduction in this ocean uptake would have a major impact on the future growth rate of atmospheric CO2. Model simulations that include a simple representation of biological processes show a potentially large offsetting effect resulting from the downward flux of biogenic carbon. However, the magnitude of the offset is difficult to quantify with present knowledge.

  11. Projection-Based Reduced Order Modeling for Spacecraft Thermal Analysis

    NASA Technical Reports Server (NTRS)

    Qian, Jing; Wang, Yi; Song, Hongjun; Pant, Kapil; Peabody, Hume; Ku, Jentung; Butler, Charles D.

    2015-01-01

    This paper presents a mathematically rigorous, subspace projection-based reduced order modeling (ROM) methodology and an integrated framework to automatically generate reduced order models for spacecraft thermal analysis. Two key steps in the reduced order modeling procedure are described: (1) the acquisition of a full-scale spacecraft model in the ordinary differential equation (ODE) and differential algebraic equation (DAE) form to resolve its dynamic thermal behavior; and (2) the ROM to markedly reduce the dimension of the full-scale model. Specifically, proper orthogonal decomposition (POD) in conjunction with discrete empirical interpolation method (DEIM) and trajectory piece-wise linear (TPWL) methods are developed to address the strong nonlinear thermal effects due to coupled conductive and radiative heat transfer in the spacecraft environment. Case studies using NASA-relevant satellite models are undertaken to verify the capability and to assess the computational performance of the ROM technique in terms of speed-up and error relative to the full-scale model. ROM exhibits excellent agreement in spatiotemporal thermal profiles (<0.5% relative error in pertinent time scales) along with salient computational acceleration (up to two orders of magnitude speed-up) over the full-scale analysis. These findings establish the feasibility of ROM to perform rational and computationally affordable thermal analysis, develop reliable thermal control strategies for spacecraft, and greatly reduce the development cycle times and costs.

  12. An Order Statistics Approach to the Halo Model for Galaxies

    NASA Astrophysics Data System (ADS)

    Paul, Niladri; Paranjape, Aseem; Sheth, Ravi K.

    2017-01-01

    We use the Halo Model to explore the implications of assuming that galaxy luminosities in groups are randomly drawn from an underlying luminosity function. We show that even the simplest of such order statistics models - one in which this luminosity function p(L) is universal - naturally produces a number of features associated with previous analyses based on the `central plus Poisson satellites' hypothesis. These include the monotonic relation of mean central luminosity with halo mass, the Lognormal distribution around this mean, and the tight relation between the central and satellite mass scales. In stark contrast to observations of galaxy clustering, however, this model predicts no luminosity dependence of large scale clustering. We then show that an extended version of this model, based on the order statistics of a halo mass dependent luminosity function p(L|m), is in much better agreement with the clustering data as well as satellite luminosities, but systematically under-predicts central luminosities. This brings into focus the idea that central galaxies constitute a distinct population that is affected by different physical processes than are the satellites. We model this physical difference as a statistical brightening of the central luminosities, over and above the order statistics prediction. The magnitude gap between the brightest and second brightest group galaxy is predicted as a by-product, and is also in good agreement with observations. We propose that this order statistics framework provides a useful language in which to compare the Halo Model for galaxies with more physically motivated galaxy formation models.

  13. The anthropogenic influence on Iron deposition over the oceans: a 3-D global modeling

    NASA Astrophysics Data System (ADS)

    Myriokefalitakis, Stelios; Mihalopoulos, Nikos; Baker, Alex; Kanakidou, Maria

    2014-05-01

    Iron (Fe) deposition over oceans is directly linked to the marine biological productivity and consequently to atmospheric CO2 concentrations. Experimental and modeling results support that both inorganic (sulphate, ammonium and nitrate) and organic (e.g. oxalate) ligands can increase the Fe mobilization. Mineral dust deposition is considered as the most important supply of bioavailable Fe in the oceans. Although, due to the low soil soluble iron fractions, atmospheric processes which are also related to anthropogenic emissions, can convert iron to more soluble forms in the atmosphere. Recent studies also support that anthropogenic emissions of Fe from combustion sources also significantly contribute to the dissolved Fe atmospheric pool. The evaluation of the impact of humans on atmospheric soluble or bioavailable Fe deposition remains challenging, since Fe mobilization due to changes in anthropogenic emissions is largely uncertain. In the present study, the global atmospheric Fe cycle is parameterized in the 3-D chemical transport global model TM4-ECPL and the model is used to calculate the Fe deposition over the oceans. The model considers explicitly organic, sulfur and nitrogen gas-phase chemistry, aqueous-phase organic chemistry, including oxalate and all major aerosol constituents. TM4-ECPL simulates the organic and inorganic ligand-promoted mineral Fe dissolution and also aqueous-phase photochemical reactions between different forms of Fe (III/II). Primary emissions of Fe associated with dust and soluble Fe from combustion processes as well as atmospheric processing of the emitted Fe is taken into account in the model Sensitivity simulations are performed to study the impact of anthropogenic emissions on Fe deposition. For this preindustrial, present and future emission scenarios are used in the model in order to examine the response of chemical composition of iron-containing aerosols to environmental changes. The release of soluble iron associated with

  14. User’s Manual for the Navy Coastal Ocean Model (NCOM) Version 4.0

    DTIC Science & Technology

    2009-02-06

    number of aspects of the ocean model run, including the model physics and numerics, the forcing, and the output. modelo - name of model (NCOM1) being...model. In Three-Dimensional Coastal Ocean Models, N. Heaps, Ed., American Union, New York, N.Y., 208 pp . Collins-Sussman, B., B.W. Fitzpatrick...Serrano, (1997). ERA description. ECMWF Re-Analysis Project Report Series, No. 1, 72 pp . [Available from ECMWF, Shinfield Park, Reading RG2 9AX

  15. Navy Coastal Ocean Model (NCOM) Version 4.0 (User’s Manual)

    DTIC Science & Technology

    2009-02-06

    number of aspects of the ocean model run, including the model physics and numerics, the forcing, and the output. modelo - name of model (NCOM1...circulation model. In Three-Dimensional Coastal Ocean Models, N. Heaps, Ed., American Union, New York, N.Y., 208 pp . Collins-Sussman, B., B.W. Fitzpatrick...E. Serrano, (1997). ERA description. ECMWF Re-Analysis Project Report Series, No. 1, 72 pp . [Available from ECMWF, Shinfield Park, Reading RG2 9AX

  16. A new derivation of the shallow water equations in geographical coordinates and their application to the global barotropic ocean model (the DEBOT model)

    NASA Astrophysics Data System (ADS)

    Einšpigel, David; Martinec, Zdeněk

    2015-08-01

    The purpose of this paper is to present a new global barotropic ocean model-the DEBOT model. The model is based on the shallow water equations which we newly express in geographical coordinates. The derivation includes the boundary conditions and the Reynolds tensor in a form used commonly in oceanography. The numerical model employs finite differences on an Arakawa-C grid in space and a generalized forward-backward scheme in time with a combined third-order Adams-Bashforth and fourth-order Adams-Moulton step. The validity of the model is demonstrated by the tests based on conservation integral invariants. As a practical application, we present ocean circulation simulations generated by the lunisolar tidal force.

  17. A second-order impact model for forest fire regimes.

    PubMed

    Maggi, Stefano; Rinaldi, Sergio

    2006-09-01

    We present a very simple "impact" model for the description of forest fires and show that it can mimic the known characteristics of wild fire regimes in savannas, boreal forests, and Mediterranean forests. Moreover, the distribution of burned biomasses in model generated fires resemble those of burned areas in numerous large forests around the world. The model has also the merits of being the first second-order model for forest fires and the first example of the use of impact models in the study of ecosystems.

  18. A first order analytical TOD sensor performance model

    NASA Astrophysics Data System (ADS)

    Bijl, Piet; Hogervorst, Maarten A.

    2016-10-01

    In this paper we present a new, analytical TOD model. The model provides an estimate of the TOD curve for an Optical, Electro-Optical or Thermal Infrared imaging system based on a limited number of essential system parameters. This is useful to get a quick Target Acquisition range prediction but also serves as a first order input to an image-based TOD simulation model. The model is based on a human observer performance dataset on TOD test patterns, systematically degraded by simulated sensor effects. The model is validated against a number of historical TOD tests on visual and thermal camera systems and provides excellent performance predictions.

  19. Acceleration for microflow simulations of high-order moment models by using lower-order model correction

    NASA Astrophysics Data System (ADS)

    Hu, Zhicheng; Li, Ruo; Qiao, Zhonghua

    2016-12-01

    We study the acceleration of steady-state computation for microflow, which is modeled by the high-order moment models derived recently from the steady-state Boltzmann equation with BGK-type collision term. By using the lower-order model correction, a novel nonlinear multi-level moment solver is developed. Numerical examples verify that the resulting solver improves the convergence significantly thus is able to accelerate the steady-state computation greatly. The behavior of the solver is also numerically investigated. It is shown that the convergence rate increases, indicating the solver would be more efficient, as the total levels increases. Three order reduction strategies of the solver are considered. Numerical results show that the most efficient order reduction strategy would be ml-1 = ⌈ml / 2 ⌉.

  20. Effects of Southern Hemisphere Wind Changes on the Meridional Overturning Circulation in Ocean Models.

    PubMed

    Gent, Peter R

    2016-01-01

    Observations show that the Southern Hemisphere zonal wind stress maximum has increased significantly over the past 30 years. Eddy-resolving ocean models show that the resulting increase in the Southern Ocean mean flow meridional overturning circulation (MOC) is partially compensated by an increase in the eddy MOC. This effect can be reproduced in the non-eddy-resolving ocean component of a climate model, providing the eddy parameterization coefficient is variable and not a constant. If the coefficient is a constant, then the Southern Ocean mean MOC change is balanced by an unrealistically large change in the Atlantic Ocean MOC. Southern Ocean eddy compensation means that Southern Hemisphere winds cannot be the dominant mechanism driving midlatitude North Atlantic MOC variability.

  1. Modeling the role of nitrification in open ocean productivity and the nitrogen cycle.

    PubMed

    Yool, Andrew

    2011-01-01

    The ocean is an important component of the global carbon cycle, and currently serves as the principal sink for anthropogenic CO(2) from the atmosphere. A key role in the natural oceanic carbon cycle is played by the plankton ecosystem, which acts to elevate the storage capacity of the ocean, but it is believed that this will experience change in the future in response to anthropogenic forcing. One of the approaches used to understand and forecast the oceanic carbon cycle is ecosystem modeling, and this is typically grounded on the nitrogen cycle because of the strong regulatory role this element plays in biological productivity. Nitrification is one of the central processes in the oceanic nitrogen cycle, one whose role may change in the future, but also one with a particular relevance to observational efforts to quantify the biological carbon cycle. Here, we describe and summarize current efforts to model nitrification in pelagic open ocean ecosystems, and look forward to future avenues for progress.

  2. Modeling of subaqueous melting in Petermann Fjord, Northwestern Greenland using an ocean general circulation model

    NASA Astrophysics Data System (ADS)

    Cai, C.; Rignot, E. J.; Xu, Y.; An, L.; Tinto, K. J.; van den Broeke, M. R.

    2014-12-01

    Basal melting of the floating tongue of Petermann Glacier, in northwestern Greenland is by far the largest process of mass ablation. Melting of the floating tongue is controlled by the buoyancy of the melt water plume, the pressure-dependence of the melting point of sea ice, and the mixing of warm subsurface water with fresh buoyant subglacial discharge. In prior simulations of this melting process, the role of subglacial discharge has been neglected because in similar configurations (floating ice shelves) in the Antarctic, surface runoff is negligible; this is however not true in Greenland. Here, we use the Mass Institute of Technology general circulation model (MITgcm) at a high spatial resolution (10 m x 10 m) to simulate the melting process of the ice shelf in 2-D. The model is constrained by ice shelf bathymetry and ice thickness (refined model in the immediate vicinity of the grounding line) from NASA Operation IceBridge (2011), ocean temperature/salinity data from Johnson et al. (2011), ocean tide height and current from the Arctic Ocean Tidal Inverse Model (AOTIM-5) by Padman and Erofeeva (2004) and subglacial discharge at the grounding line calculated by the hydrostatic potential of the ice from estimated products of the Regional Atmospheric Climate Model (RACMO) of Royal Netherlands Meteorological Institute (KNMI). We compare the results obtained in winter (no runoff) with summer, and the sensitivity of the results to thermal forcing from the ocean, and to the variation of tide height and current, and to the magnitude of subglacial runoff. We conclude on the impact of the ocean and surface melting on the melting regime of the floating ice tongue of Petermann. The basal melt rate increases ~20% with summer surface runoff. This work is performed under a contract with NASA Cryosphere Program.

  3. Tracking the drift of a human body in the coastal ocean using numerical prediction models of the oceanic, atmospheric and wave conditions.

    PubMed

    Carniel, S; Umgiesser, G; Sclavo, M; Kantha, L H; Monti, S

    2002-01-01

    This paper describes the use of numerical models to infer the path of a floating human body in the Ligurian Sea (north-west Mediterranean) during the month of January 2001. The prevailing oceanic currents were obtained from a state-of-the-art real-time nowcast/forecast ocean circulation model, while the sea state was inferred from a numerical model of the surface gravity waves, both driven by regional atmospheric models. The surface currents (from the ocean model) and the drift ones at the ocean surface, as inferred from the wave model, were used to drive a Lagrangian model of the drifting body to deduce its plausible trajectory along the Ligurian coast. The inferred path is reasonably consistent with location and time of the discovery on the French coast. This note illustrates the utility of numerical prediction models at the disposal of modern forensic science in the fields of ocean sciences.

  4. Experimental design for three interrelated Marine Ice-Sheet and Ocean Model Intercomparison Projects

    NASA Astrophysics Data System (ADS)

    Asay-Davis, X. S.; Cornford, S. L.; Durand, G.; Galton-Fenzi, B. K.; Gladstone, R. M.; Gudmundsson, G. H.; Hattermann, T.; Holland, D. M.; Holland, D.; Holland, P. R.; Martin, D. F.; Mathiot, P.; Pattyn, F.; Seroussi, H.

    2015-11-01

    Coupled ice sheet-ocean models capable of simulating moving grounding lines are just becoming available. Such models have a broad range of potential applications in studying the dynamics of marine ice sheets and tidewater glaciers, from process studies to future projections of ice mass loss and sea level rise. The Marine Ice Sheet-Ocean Model Intercomparison Project (MISOMIP) is a community effort aimed at designing and coordinating a series of model intercomparison projects (MIPs) for model evaluation in idealized setups, model verification based on observations, and future projections for key regions in the West Antarctic Ice Sheet (WAIS). Here we describe computational experiments constituting three interrelated MIPs for marine ice sheet models and regional ocean circulation models incorporating ice shelf cavities. These consist of ice sheet experiments under the Marine Ice Sheet MIP third phase (MISMIP+), ocean experiments under the ice shelf-ocean MIP second phase (ISOMIP+) and coupled ice sheet-ocean experiments under the MISOMIP first phase (MISOMIP1). All three MIPs use a shared domain with idealized bedrock topography and forcing, allowing the coupled simulations (MISOMIP1) to be compared directly to the individual component simulations (MISMIP+ and ISOMIP+). The experiments, which have qualitative similarities to Pine Island Glacier Ice Shelf and the adjacent region of the Amundsen Sea, are designed to explore the effects of changes in ocean conditions, specifically the temperature at depth, on basal melting and ice dynamics. In future work, differences between model results will form the basis for evaluation of the participating models.

  5. Accurate numerical forward model for optimal retracking of SIRAL2 SAR echoes over open ocean

    NASA Astrophysics Data System (ADS)

    Phalippou, L.; Demeestere, F.

    2011-12-01

    The SAR mode of SIRAL-2 on board Cryosat-2 has been designed to measure primarily sea-ice and continental ice (Wingham et al. 2005). In 2005, K. Raney (KR, 2005) pointed out the improvements brought by SAR altimeter for open ocean. KR results were mostly based on 'rule of thumb' considerations on speckle noise reduction due to the higher PRF and to speckle decorrelation after SAR processing. In 2007, Phalippou and Enjolras (PE,2007) provided the theoretical background for optimal retracking of SAR echoes over ocean with a focus on the forward modelling of the power-waveforms. The accuracies of geophysical parameters (range, significant wave heights, and backscattering coefficient) retrieved from SAR altimeter data were derived accounting for SAR echo shape and speckle noise accurate modelling. The step forward to optimal retracking using numerical forward model (NFM) was also pointed out. NFM of the power waveform avoids analytical approximation, a warranty to minimise the geophysical dependent biases in the retrieval. NFM have been used for many years, in operational meteorology in particular, for retrieving temperature and humidity profiles from IR and microwave radiometers as the radiative transfer function is complex (Eyre, 1989). So far this technique was not used in the field of ocean conventional altimetry as analytical models (e.g. Brown's model for instance) were found to give sufficient accuracy. However, although NFM seems desirable even for conventional nadir altimetry, it becomes inevitable if one wish to process SAR altimeter data as the transfer function is too complex to be approximated by a simple analytical function. This was clearly demonstrated in PE 2007. The paper describes the background to SAR data retracking over open ocean. Since PE 2007 improvements have been brought to the forward model and it is shown that the altimeter on-ground and in flight characterisation (e.g antenna pattern range impulse response, azimuth impulse response

  6. Tropical Indian Ocean surface salinity bias in Climate Forecasting System coupled models and the role of upper ocean processes

    NASA Astrophysics Data System (ADS)

    Parekh, Anant; Chowdary, Jasti S.; Sayantani, Ojha; Fousiya, T. S.; Gnanaseelan, C.

    2016-04-01

    In the present study sea surface salinity (SSS) biases and seasonal tendency over the Tropical Indian Ocean (TIO) in the coupled models [Climate Forecasting System version 1 (CFSv1) and version 2 (CFSv2)] are examined with respect to observations. Both CFSv1 and CFSv2 overestimate SSS over the TIO throughout the year. CFSv1 displays improper SSS seasonal cycle over the Bay of Bengal (BoB), which is due to weaker model precipitation and improper river runoff especially during summer and fall. Over the southeastern Arabian Sea (AS) weak horizontal advection associated with East Indian coastal current during winter limits the formation of spring fresh water pool. On the other hand, weaker Somali jet during summer results for reduced positive salt tendency in the central and eastern AS. Strong positive precipitation bias in CFSv1 over the region off Somalia during winter, weaker vertical mixing and absence of horizontal salt advection lead to unrealistic barrier layer during winter and spring. The weaker stratification and improper spatial distribution of barrier layer thickness (BLT) in CFSv1 indicate that not only horizontal flux distribution but also vertical salt distribution displays large discrepancies. Absence of fall Wyrtki jet and winter equatorial currents in this model limit the advection of horizontal salt flux to the eastern equatorial Indian Ocean. The associated weaker stratification in eastern equatorial Indian Ocean can lead to deeper mixed layer and negative Sea Surface Temperature (SST) bias, which in turn favor positive Indian Ocean Dipole bias in CFSv1. It is important to note that improper spatial distribution of barrier layer and stratification can alter the air-sea interaction and precipitation in the models. On the other hand CFSv2 could produce the seasonal evolution and spatial distribution of SSS, BLT and stratification better than CFSv1. However CFSv2 displays positive bias in evaporation over the whole domain and negative bias in

  7. Error Estimation for Reduced Order Models of Dynamical Systems

    SciTech Connect

    Homescu, C; Petzold, L; Serban, R

    2004-01-22

    The use of reduced order models to describe a dynamical system is pervasive in science and engineering. Often these models are used without an estimate of their error or range of validity. In this paper we consider dynamical systems and reduced models built using proper orthogonal decomposition. We show how to compute estimates and bounds for these errors, by a combination of small sample statistical condition estimation and error estimation using the adjoint method. Most importantly, the proposed approach allows the assessment of regions of validity for reduced models, i.e., ranges of perturbations in the original system over which the reduced model is still appropriate. Numerical examples validate our approach: the error norm estimates approximate well the forward error while the derived bounds are within an order of magnitude.

  8. Stochastic Modeling and Global Warming Trend Extraction For Ocean Acoustic Travel Times.

    DTIC Science & Technology

    1995-01-06

    consideration and that these models can not currently be relied upon by themselves to predict global warming . Experimental data is most certainly needed, not...only to measure global warming itself, but to help improve the ocean model themselves. (AN)

  9. Nonlocal order parameters for the 1D Hubbard model.

    PubMed

    Montorsi, Arianna; Roncaglia, Marco

    2012-12-07

    We characterize the Mott-insulator and Luther-Emery phases of the 1D Hubbard model through correlators that measure the parity of spin and charge strings along the chain. These nonlocal quantities order in the corresponding gapped phases and vanish at the critical point U(c)=0, thus configuring as hidden order parameters. The Mott insulator consists of bound doublon-holon pairs, which in the Luther-Emery phase turn into electron pairs with opposite spins, both unbinding at U(c). The behavior of the parity correlators is captured by an effective free spinless fermion model.

  10. Nonlocal Order Parameters for the 1D Hubbard Model

    NASA Astrophysics Data System (ADS)

    Montorsi, Arianna; Roncaglia, Marco

    2012-12-01

    We characterize the Mott-insulator and Luther-Emery phases of the 1D Hubbard model through correlators that measure the parity of spin and charge strings along the chain. These nonlocal quantities order in the corresponding gapped phases and vanish at the critical point Uc=0, thus configuring as hidden order parameters. The Mott insulator consists of bound doublon-holon pairs, which in the Luther-Emery phase turn into electron pairs with opposite spins, both unbinding at Uc. The behavior of the parity correlators is captured by an effective free spinless fermion model.

  11. Internal pressure gradient errors in σ-coordinate ocean models in high resolution fjord studies

    NASA Astrophysics Data System (ADS)

    Berntsen, Jarle; Thiem, Øyvind; Avlesen, Helge

    2015-08-01

    Terrain following ocean models are today applied in coastal areas and fjords where the topography may be very steep. Recent advances in high performance computing facilitate model studies with very high spatial resolution. In general, numerical discretization errors tend to zero with the grid size. However, in fjords and near the coast the slopes may be very steep, and the internal pressure gradient errors associated with σ-models may be significant even in high resolution studies. The internal pressure gradient errors are due to errors when estimating the density gradients in σ-models, and these errors are investigated for two idealized test cases and for the Hardanger fjord in Norway. The methods considered are the standard second order method and a recently proposed method that is balanced such that the density gradients are zero for the case ρ = ρ(z) where ρ is the density and z is the vertical coordinate. The results show that by using the balanced method, the errors may be reduced considerably also for slope parameters larger than the maximum suggested value of 0.2. For the Hardanger fjord case initialized with ρ = ρ(z) , the errors in the results produced with the balanced method are orders of magnitude smaller than the corresponding errors in the results produced with the second order method.

  12. Validation of The Standard Aerosol Models Used In The Atmospheric Correction Algorithms For Satellite Ocean Observation

    NASA Astrophysics Data System (ADS)

    Martiny, N.; Santer, R.

    Over ocean, the total radiance measured by the satellite sensors at the top of the atmo- sphere is mainly atmospheric. In order to access to the water leaving radiance, directly related to the concentration of the different components of the water, we need to cor- rect the satellite measurements from the important atmospheric contribution. In the atmosphere, the light emitted by the sun is scattered by the molecules, absorbed by the gases, and both scattered and absorbed in unknown proportions by the aerosols, particles confined in the first layer of the atmosphere due to their large size. The remote sensing of the aerosols represents then a complex step in the atmospheric correction scheme. Over ocean, the principle of the aerosol remote sensing lies on the assump- tion that the water is absorbent in the red and the near-infrared. The aerosol model is then deduced from these spectral bands and used to extrapolate the aerosol optical properties in the visible wavelengths. For ocean color sensors such as CZCS, OCTS, POLDER, SeaWiFS or MODIS, the atmospheric correction algorithms use standard aerosol models defined by Shettle &Fenn for their look-up-tables. Over coastal wa- ters, are these models still suitable? The goal of this work is to validate the standard aerosol models used in the atmospheric correction algorithms over coastal zones. For this work, we use ground-based in-situ measurements from the CIMEL sunphotome- ter instrument. Using the extinction measurements, we can deduce the aerosol spectral dependency which falls between the spectral dependency of two standard Shettle &Fenn aerosol models. After the interpolation of the aerosol model, we can use it to extrapolate in the visible the optical parameters needed for the atmospheric correction scheme: Latm, the atmospheric radiance and T, the atmospheric transmittance. The simulations are done using a radiative transfer code based on the successive order of scattering. Latm and T are then used for

  13. A first appraisal of prognostic ocean DMS models and prospects for their use in climate models

    NASA Astrophysics Data System (ADS)

    Le Clainche, Yvonnick; VéZina, Alain; Levasseur, Maurice; Cropp, Roger A.; Gunson, Jim R.; Vallina, Sergio M.; Vogt, Meike; Lancelot, Christiane; Allen, J. Icarus; Archer, Stephen D.; Bopp, Laurent; Deal, Clara; Elliott, Scott; Jin, Meibing; Malin, Gill; Schoemann, VéRonique; Simó, Rafel; Six, Katharina D.; Stefels, Jacqueline

    2010-09-01

    Ocean dimethylsulfide (DMS) produced by marine biota is the largest natural source of atmospheric sulfur, playing a major role in the formation and evolution of aerosols, and consequently affecting climate. Several dynamic process-based DMS models have been developed over the last decade, and work is progressing integrating them into climate models. Here we report on the first international comparison exercise of both 1D and 3D prognostic ocean DMS models. Four global 3D models were compared to global sea surface chlorophyll and DMS concentrations. Three local 1D models were compared to three different oceanic stations (BATS, DYFAMED, OSP) where available time series data offer seasonal coverage of chlorophyll and DMS variability. Two other 1D models were run at one site only. The major point of divergence among models, both within 3D and 1D models, relates to their ability to reproduce the summer peak in surface DMS concentrations usually observed at low to mid- latitudes. This significantly affects estimates of global DMS emissions predicted by the models. The inability of most models to capture this summer DMS maximum appears to be constrained by the basic structure of prognostic DMS models: dynamics of DMS and dimethylsulfoniopropionate (DMSP), the precursor of DMS, are slaved to the parent ecosystem models. Only the models which include environmental effects on DMS fluxes independently of ecological dynamics can reproduce this summer mismatch between chlorophyll and DMS. A major conclusion of this exercise is that prognostic DMS models need to give more weight to the direct impact of environmental forcing (e.g., irradiance) on DMS dynamics to decouple them from ecological processes.

  14. New, higher-order, elasticity-based micromechanics model

    SciTech Connect

    Williams, T. O.

    2003-01-01

    The formulation for a new homogenization theory is presented. The theory utilizes a higher-order, elasticity-based cell analysis of a periodic array of unit cells. The unit cell is discretized into subregions or subcells. The displacement field within each subcell is approximated by an (truncated) eigenfunction function expansion of up to fifth order. The governing equations are developed by satisfying the pointwise governing equations of geometrically linear continuum mechanics exactly up through the given order of the subcell displacement fields. The specified governing equations are valid for any type of constitutive model used to describe the behavior of the material in a subcell. The fifth order theory is subsequently reduced to a third order theory. The appropriate reduction of the fifth and third order theories to the first order theory (which corresponds to a variant of the original method of cells (MOC) (Aboudi, 1991) theory) is outlined. The 3D ECM theory correctly reduces to the 2D ECM theory microstructures and the exact 1D theory for bilaminated structures. Comparison of the predicted bulk and local responses with published results indicates that the theory accurately predicts both types of responses. Furthermore, it is shown that the higher order fields introduced coupling effects between the local fields that can result in substantial changes in the predicted bulk inelastic response of a composite.

  15. Trends in Ocean Irradiance using a Radiative Model Forced with Terra Aerosols and Clouds

    NASA Technical Reports Server (NTRS)

    Gregg, Watson; Casey, Nancy; Romanou, Anastasia

    2010-01-01

    Aerosol and cloud information from MODIS on Terra provide enhanced capability to understand surface irradiance over the oceans and its variability. These relationships can be important for ocean biology and carbon cycles. An established radiative transfer model, the Ocean-Atmosphere Spectral Irradiance Model (OASIM) is used to describe ocean irradiance variability on seasonal to decadal time scales. The model is forced with information on aerosols and clouds from the MODIS sensor on Terra and Aqua. A 7-year record (2000-2006) showed no trends in global ocean surface irradiance or photosynthetic available irradiance (PAR). There were significant (P<0.05) negative trends in the Mediterranean Sea, tropical Pacific) and tropical Indian Oceans, of -7.0, -5.0 and -2.7 W/sq m respectively. Global interannual variability was also modest. Regional interannual variability was quite large in some ocean basins, where monthly excursions from climatology were often >20 W/sq m. The trends using MODIS data contrast with results from OASIM using liquid water path estimates from the International Satellite Cloud Climatology Project (ISCCP). Here, a global trend of -2 W/sq m was observed, largely dues to a large negative trend in the Antarctic -12 W/sq m. These results suggest the importance of the choice of liquid water path data sets in assessments of medium-length trends in ocean surface irradiance. The choices also impact the evaluation of changes in ocean biogeochemistry.

  16. Model Order Reduction for Fluid Dynamics with Moving Solid Boundary

    NASA Astrophysics Data System (ADS)

    Gao, Haotian; Wei, Mingjun

    2016-11-01

    We extended the application of POD-Galerkin projection for model order reduction from usual fixed-domain problems to more general fluid-solid systems when moving boundary/interface is involved. The idea is similar to numerical simulation approaches using embedded forcing terms to represent boundary motion and domain change. However, such a modified approach will not get away with the unsteadiness of boundary terms which appear as time-dependent coefficients in the new Galerkin model. These coefficients need to be pre-computed for prescribed motion, or worse, to be computed at each time step for non-prescribed motion. The extra computational cost gets expensive in some cases and eventually undermines the value of using reduced-order models. One solution is to decompose the moving boundary/domain to orthogonal modes and derive another low-order model with fixed coefficients for boundary motion. Further study shows that the most expensive integrations resulted from the unsteady motion (in both original and domain-decomposition approaches) have almost negligible impact on the overall dynamics. Dropping these expensive terms reduces the computation cost by at least one order while no obvious effect on model accuracy is noticed. Supported by ARL.

  17. Quantifying melt production and degassing rate at mid-ocean ridges from global mantle convection models with plate motion history

    NASA Astrophysics Data System (ADS)

    Li, Mingming; Black, Benjamin; Zhong, Shijie; Manga, Michael; Rudolph, Maxwell L.; Olson, Peter

    2016-07-01

    The Earth's surface volcanism exerts first-order controls on the composition of the atmosphere and the climate. On Earth, the majority of surface volcanism occurs at mid-ocean ridges. In this study, based on the dependence of melt fraction on temperature, pressure, and composition, we compute melt production and degassing rate at mid-ocean ridges from three-dimensional global mantle convection models with plate motion history as the surface velocity boundary condition. By incorporating melting in global mantle convection models, we connect deep mantle convection to surface volcanism, with deep and shallow mantle processes internally consistent. We compare two methods to compute melt production: a tracer method and an Eulerian method. Our results show that melt production at mid-ocean ridges is mainly controlled by surface plate motion history, and that changes in plate tectonic motion, including plate reorganizations, may lead to significant deviation of melt production from the expected scaling with seafloor production rate. We also find a good correlation between melt production and degassing rate beneath mid-ocean ridges. The calculated global melt production and CO2 degassing rate at mid-ocean ridges varies by as much as a factor of 3 over the past 200 Myr. We show that mid-ocean ridge melt production and degassing rate would be much larger in the Cretaceous, and reached maximum values at ˜150-120 Ma. Our results raise the possibility that warmer climate in the Cretaceous could be due in part to high magmatic productivity and correspondingly high outgassing rates at mid-ocean ridges during that time.

  18. Parameterized reduced-order models using hyper-dual numbers.

    SciTech Connect

    Fike, Jeffrey A.; Brake, Matthew Robert

    2013-10-01

    The goal of most computational simulations is to accurately predict the behavior of a real, physical system. Accurate predictions often require very computationally expensive analyses and so reduced order models (ROMs) are commonly used. ROMs aim to reduce the computational cost of the simulations while still providing accurate results by including all of the salient physics of the real system in the ROM. However, real, physical systems often deviate from the idealized models used in simulations due to variations in manufacturing or other factors. One approach to this issue is to create a parameterized model in order to characterize the effect of perturbations from the nominal model on the behavior of the system. This report presents a methodology for developing parameterized ROMs, which is based on Craig-Bampton component mode synthesis and the use of hyper-dual numbers to calculate the derivatives necessary for the parameterization.

  19. The Ocean Construct: A Model for Maritime Education

    ERIC Educational Resources Information Center

    Allin, Lawrence C.

    1977-01-01

    Described is an organizational construct to help teachers integrate the oceanographic and maritime disciplines within a comprehensible framework. The construct considers three areas: aquasphere, human adaptation to the ocean, and integrative prospects. (Author/AV)

  20. Adaptive Error Estimation in Linearized Ocean General Circulation Models

    NASA Technical Reports Server (NTRS)

    Chechelnitsky, Michael Y.

    1999-01-01

    representation error, i.e. the dominance of the mesoscale eddies in the T/P signal, which are not part of the 21 by 1" GCM. Therefore, the impact of the observations on the assimilation is very small even after the adjustment of the error statistics. This work demonstrates that simult&neous estimation of the model and measurement error statistics for data assimilation with global ocean data sets and linearized GCMs is possible. However, the error covariance estimation problem is in general highly underdetermined, much more so than the state estimation problem. In other words there exist a very large number of statistical models that can be made consistent with the available data. Therefore, methods for obtaining quantitative error estimates, powerful though they may be, cannot replace physical insight. Used in the right context, as a tool for guiding the choice of a small number of model error parameters, covariance matching can be a useful addition to the repertory of tools available to oceanographers.

  1. Development of a global ocean mercury model with a methylation cycle: Outstanding issues

    NASA Astrophysics Data System (ADS)

    Semeniuk, Kirill; Dastoor, Ashu

    2017-02-01

    We present a newly developed global ocean mercury (Hg) transport and biogeochemistry model and use preanthropogenic equilibrium simulations to highlight physical and chemical processes which reveal significant knowledge gaps that need to be addressed. As with previous 3-D ocean Hg model work we use a bulk chemistry scheme based on particulate organic carbon remineralization. We also include an explicit methylation cycle based on available reaction rates. The methylation to demethylation rate ratio based on various field studies is found to be inconsistent with the concentration ratios measured in the Southern Ocean around Antarctica and in the Arctic. There is also model-measurement disagreement in the old waters of the tropical and North Pacific Ocean. The model produces an intermediate water maximum in total Hg in this region reflecting the higher age of water which is absent in observations. The model also underestimates total Hg concentrations in the deepest waters in this region. These disagreements in depth profile shape point to an inadequate representation of scavenging and sedimentation and possibly seabed emission or remobilization of Hg. In addition, the total Hg distribution differences compared to previous model work reflect sensitivity to ocean model transport characteristics and in particular the tracer diffusion. The residence time of Hg in the global ocean and the surface evasion flux of elemental Hg is sensitive to such model aspects. We find a global ocean Hg turnover time against sediment burial to be about 1100 years which is within the range of previous studies.

  2. Energetics of a Global Ocean Circulation Model Compared to Observations

    DTIC Science & Technology

    2011-08-09

    in the dynamics of the ocean circulation with instabilities of the strong mean currents generating eddies in the upper ocean. Interactions between...obser- vations from surface drifters, geostrophic currents from satellite altimetry, subsurface floats and deep current meter moorings. HYCOM...rings of the boundary currents [Stammer, 1997; Ferrari and Wunsch, 2009, 2010], is generated by instabilities of the mean flow and direct wind forcing

  3. Accuracy Assessment of Global Barotropic Ocean Tide Models

    DTIC Science & Technology

    2014-08-07

    Denmark, 4Department of Earth and Environmental Science, University of Michigan, Ann Arbor, Michigan, USA, 5Deutsches Geodätisches Forschungsinstitut...and Technology, Nanjing, China, 8SGT Inc., NASA/GSFC, Greenbelt, Maryland, USA, 9College of Earth , Ocean, and Atmospheric Sciences, Oregon State... Earth Sciences, Ohio State University, Columbus, Ohio, USA, 12School of Ocean Sciences, Bangor University, Menai Bridge, UK, 13Department of Applied

  4. Numerical modeling of higher order magnetic moments in UXO discrimination

    USGS Publications Warehouse

    Sanchez, V.; Yaoguo, L.; Nabighian, M.N.; Wright, D.L.

    2008-01-01

    The surface magnetic anomaly observed in unexploded ordnance (UXO) clearance is mainly dipolar, and consequently, the dipole is the only magnetic moment regularly recovered in UXO discrimination. The dipole moment contains information about the intensity of magnetization but lacks information about the shape of the target. In contrast, higher order moments, such as quadrupole and octupole, encode asymmetry properties of the magnetization distribution within the buried targets. In order to improve our understanding of magnetization distribution within UXO and non-UXO objects and to show its potential utility in UXO clearance, we present a numerical modeling study of UXO and related metallic objects. The tool for the modeling is a nonlinear integral equation describing magnetization within isolated compact objects of high susceptibility. A solution for magnetization distribution then allows us to compute the magnetic multipole moments of the object, analyze their relationships, and provide a depiction of the anomaly produced by different moments within the object. Our modeling results show the presence of significant higher order moments for more asymmetric objects, and the fields of these higher order moments are well above the noise level of magnetic gradient data. The contribution from higher order moments may provide a practical tool for improved UXO discrimination. ?? 2008 IEEE.

  5. Assimilation of TOPEX/POSEIDON Altimeter Data into a Global Ocean Circulation Model: Are the Results Any Good?

    NASA Technical Reports Server (NTRS)

    Fukumori, I.; Fu, L. L.; Chao, Y.

    1998-01-01

    The feasibility of assimilating satellite altimetry data into a global ocean general ocean general circulation model is studied. Three years of TOPEX/POSEIDON data is analyzed using a global, three-dimensional, nonlinear primitive equation model.

  6. Global Bathymetric Prediction For Ocean Modeling and Marine Geophysics

    NASA Technical Reports Server (NTRS)

    Sandwell, David T.; Smith, Walter H. F.; Sichoix, Lydie; Frey, Herbert V. (Technical Monitor)

    2001-01-01

    We proposed to construct a complete bathymetric map of the oceans at a 3-10 km resolution by combining all of the available depth soundings collected over the past 30 years with high resolution marine gravity information provided by the Geosat, ERS-1/2, and Topex/Poseidon altimeters. Detailed bathymetry is essential for understanding physical oceanography and marine geophysics. Currents and tides are controlled by the overall shapes of the ocean basins as well as the smaller sharp ocean ridges and seamounts. Because erosion rates are low in the deep oceans, detailed bathymetry reveals the mantle convection patterns, the plate boundaries, the cooling/subsidence of the oceanic lithosphere, the oceanic plateaus, and the distribution of off-ridge volcanoes. We proposed to: (1) Accumulate all available depth soundings collected over the past 30 years; (2) Use the short wavelength (< 160 km) satellite gravity information to interpolate between sparse ship soundings; (3) Improve the resolution of the marine gravity field using enhanced estimates along repeat altimeter profiles together with the dense altimeter measurements; (4) Refine/improve bathymetric predictions using the improved resolution gravity field and also by investigating computer-intensive methods for bathymetric prediction such as inverse theory; and (5) Produce a 'Globe of the Earth' similar to the globe of Venus prepared by the NASA Magellan investigation. This will also include the best available digital land data.

  7. Reduced-order models of the coagulation cascade

    NASA Astrophysics Data System (ADS)

    Hansen, Kirk B.; Shadden, Shawn C.

    2015-11-01

    Previous models of flow-mediated thrombogenesis have generally included the transport and reaction of dozens of biochemical species involved in the coagulation cascade. Researchers have shown, however, that thrombin generation curves can be accurately reproduced by a significantly smaller system of reactions. These reduced-order models are based on the system of ordinary differential equations representative of a well-mixed system, however, not the system of advection-diffusion-reaction equations required to model the flow-mediated case. Additionally, they focus solely on reproducing the thrombin generation curve, although accurate representation of certain intermediate species may be required to model additional aspects of clot formation, e.g. interactions with activated and non-activated platelets. In this work, we develop a method to reduce the order of a coagulation model through optimization techniques. The results of this reduced-order model are then compared to those of the full system in several representative cardiovascular flows. This work was supported by NSF grant 1354541, the NSF GRFP, and NIH grant HL108272.

  8. Atmospheric Turbulence Modeling for Aero Vehicles: Fractional Order Fits

    NASA Technical Reports Server (NTRS)

    Kopasakis, George

    2010-01-01

    Atmospheric turbulence models are necessary for the design of both inlet/engine and flight controls, as well as for studying coupling between the propulsion and the vehicle structural dynamics for supersonic vehicles. Models based on the Kolmogorov spectrum have been previously utilized to model atmospheric turbulence. In this paper, a more accurate model is developed in its representative fractional order form, typical of atmospheric disturbances. This is accomplished by first scaling the Kolmogorov spectral to convert them into finite energy von Karman forms and then by deriving an explicit fractional circuit-filter type analog for this model. This circuit model is utilized to develop a generalized formulation in frequency domain to approximate the fractional order with the products of first order transfer functions, which enables accurate time domain simulations. The objective of this work is as follows. Given the parameters describing the conditions of atmospheric disturbances, and utilizing the derived formulations, directly compute the transfer function poles and zeros describing these disturbances for acoustic velocity, temperature, pressure, and density. Time domain simulations of representative atmospheric turbulence can then be developed by utilizing these computed transfer functions together with the disturbance frequencies of interest.

  9. Atmospheric Turbulence Modeling for Aero Vehicles: Fractional Order Fits

    NASA Technical Reports Server (NTRS)

    Kopasakis, George

    2015-01-01

    Atmospheric turbulence models are necessary for the design of both inlet/engine and flight controls, as well as for studying coupling between the propulsion and the vehicle structural dynamics for supersonic vehicles. Models based on the Kolmogorov spectrum have been previously utilized to model atmospheric turbulence. In this paper, a more accurate model is developed in its representative fractional order form, typical of atmospheric disturbances. This is accomplished by first scaling the Kolmogorov spectral to convert them into finite energy von Karman forms and then by deriving an explicit fractional circuit-filter type analog for this model. This circuit model is utilized to develop a generalized formulation in frequency domain to approximate the fractional order with the products of first order transfer functions, which enables accurate time domain simulations. The objective of this work is as follows. Given the parameters describing the conditions of atmospheric disturbances, and utilizing the derived formulations, directly compute the transfer function poles and zeros describing these disturbances for acoustic velocity, temperature, pressure, and density. Time domain simulations of representative atmospheric turbulence can then be developed by utilizing these computed transfer functions together with the disturbance frequencies of interest.

  10. Robust simulation of buckled structures using reduced order modeling

    NASA Astrophysics Data System (ADS)

    Wiebe, R.; Perez, R. A.; Spottswood, S. M.

    2016-09-01

    Lightweight metallic structures are a mainstay in aerospace engineering. For these structures, stability, rather than strength, is often the critical limit state in design. For example, buckling of panels and stiffeners may occur during emergency high-g maneuvers, while in supersonic and hypersonic aircraft, it may be induced by thermal stresses. The longstanding solution to such challenges was to increase the sizing of the structural members, which is counter to the ever present need to minimize weight for reasons of efficiency and performance. In this work we present some recent results in the area of reduced order modeling of post- buckled thin beams. A thorough parametric study of the response of a beam to changing harmonic loading parameters, which is useful in exposing complex phenomena and exercising numerical models, is presented. Two error metrics that use but require no time stepping of a (computationally expensive) truth model are also introduced. The error metrics are applied to several interesting forcing parameter cases identified from the parametric study and are shown to yield useful information about the quality of a candidate reduced order model. Parametric studies, especially when considering forcing and structural geometry parameters, coupled environments, and uncertainties would be computationally intractable with finite element models. The goal is to make rapid simulation of complex nonlinear dynamic behavior possible for distributed systems via fast and accurate reduced order models. This ability is crucial in allowing designers to rigorously probe the robustness of their designs to account for variations in loading, structural imperfections, and other uncertainties.

  11. Cloud-radiative effects on implied oceanic energy transports as simulated by atmospheric general circulation models

    SciTech Connect

    Gleckler, P.J.; Randall, D.A.; Boer, G.

    1994-03-01

    This paper reports on energy fluxes across the surface of the ocean as simulated by fifteen atmospheric general circulation models in which ocean surface temperatures and sea-ice boundaries are prescribed. The oceanic meridional energy transport that would be required to balance these surface fluxes is computed, and is shown to be critically sensitive to the radiative effects of clouds, to the extent that even the sign of the Southern Hemisphere ocean energy transport can be affected by the errors in simulated cloud-radiation interactions.

  12. Higher-Order Item Response Models for Hierarchical Latent Traits

    ERIC Educational Resources Information Center

    Huang, Hung-Yu; Wang, Wen-Chung; Chen, Po-Hsi; Su, Chi-Ming

    2013-01-01

    Many latent traits in the human sciences have a hierarchical structure. This study aimed to develop a new class of higher order item response theory models for hierarchical latent traits that are flexible in accommodating both dichotomous and polytomous items, to estimate both item and person parameters jointly, to allow users to specify…

  13. Time Ordering in Frontal Lobe Patients: A Stochastic Model Approach

    ERIC Educational Resources Information Center

    Magherini, Anna; Saetti, Maria Cristina; Berta, Emilia; Botti, Claudio; Faglioni, Pietro

    2005-01-01

    Frontal lobe patients reproduced a sequence of capital letters or abstract shapes. Immediate and delayed reproduction trials allowed the analysis of short- and long-term memory for time order by means of suitable Markov chain stochastic models. Patients were as proficient as healthy subjects on the immediate reproduction trial, thus showing spared…

  14. Sensitivity of a climatologically-driven sea ice model to the ocean heat flux

    NASA Technical Reports Server (NTRS)

    Parkinson, C. L.; Good, M. R.

    1982-01-01

    Ocean heat flux sensitivity was studied on a numerical model of sea ice covering the Weddell Sea region of the southern ocean. The model is driven by mean monthly climatological atmospheric variables. For each model run, the ocean heat flux is uniform in both space and time. Ocean heat fluxes below 20 W m to the minus 2 power do not provide sufficient energy to allow the ice to melt to its summertime thicknesses and concentrations by the end of the 14 month simulation, whereas ocean heat fluxes of 30 W m to the minus 2 power and above result in too much ice melt, producing the almost total disappearance of ice in the Weddell Sea by the end of the 14 months. These results are dependent on the atmospheric forcing fields.

  15. Scaling of atmosphere and ocean temperature correlations in observations and climate models.

    PubMed

    Fraedrich, Klaus; Blender, Richard

    2003-03-14

    Power-law scaling of near surface air temperature fluctuations and its geographical distribution is analyzed in 100-yr observations and in a 1000-yr simulation of the present-day climate with a complex atmosphere-ocean model. In observations and simulation detrended fluctuation analysis leads to the scaling exponent alpha approximately 1 over the oceans, alpha approximately 0.5 over the inner continents, and alpha approximately 0.65 in transition regions [spectrum S(f) approximately f(-beta),beta=2alpha-1]. Scaling up to decades is demonstrated in observations and coupled atmosphere-ocean models with complex and mixed-layer oceans. Only with the complex ocean model the simulated power laws extend up to centuries.

  16. Upper ocean model of dissolved atmospheric gases. Annual report, 1 August 1991--31 July 1992

    SciTech Connect

    Schudlich, R.; Emerson, S.

    1992-12-31

    The goal of this project is to estimate the rate of biological oxygen production at Hawaiian Ocean Time-series station ALOHA in the central North Pacific ocean. Our approach is to use an upper ocean model together with measurements to interpret an annual cycle of temperature, salinity, dissolved oxygen, argon, nitrogen, and the stable isotope ratio of oxygen at station ALOHA. This project represents the first upper ocean geochemical study in which model predictions are verifiable by independent measurements. Using the model, we will be able to assess the relative roles played by physical processes (air-sea gas exchange, air injection by bubbles, temperature-induced changes in gas solubility, trapping below the mixed layer, and diffusion) and biological processes (photosynthesis, respiration, and nutrient recycling) in producing the observed distribution of dissolved atmospheric gases. The long term goal of this project is to understand the utility of chemical tracers for quantifying biological processes in the ocean.

  17. Role of the Ocean-Atmosphere interactions for the Atlantic Multidecadal Variability in an idealized coupled model

    NASA Astrophysics Data System (ADS)

    Jamet, Quentin; Huck, Thierry; de Verdière, Alain Colin; Arzel, Olivier; Campin, Jean-Michel

    2015-04-01

    The role of the ocean-atmosphere interactions in the multidecadal variability of the Atlantic Meridional Overturning Circulation (AMOC) is investigated in an idealized coupled configuration of the MIT General Circulation Model. The flat-bottom ocean, composed of an Atlantic-like small basin, a Pacific-like large basin, and an unblocked Antarctic-like circumpolar channel, is coupled to a global atmospheric model (SPEEDY). In order to better represent the atmospheric dynamics and its interactions with the ocean, three set-ups, with horizontal resolution of about 4°, 2° and 1° (at the equator) in both the ocean and atmosphere models, are compared. They show a linearly increasing North Atlantic Oscillation-like variability. At all resolutions, the AMOC undergoes a spontaneous variability on multidecadal time scales between 30-40 yr, with an additional higher frequency in the highest resolution set-up. The AMOC variability responds to temperature anomalies along the western boundary through the thermal wind relationship. These temperature anomalies result from the propagation of large-scale baroclinic Rossby waves across the small basin. The unstable region responsible for the growth of Rossby waves through baroclinic instability, diagnosed using a temperature variance budget, shifts from the eastern boundary at coarse resolution (4°) to the western boundary at higher resolution (2° and 1°). An earlier study, performed with the same coarse resolution set-up (4°), has shown that the AMOC does not participate to the growth of Rossby waves, but passively reacts to these waves. The AMOC being mainly connected to the western boundary dynamics, its role in setting large scale baroclinic Rossby waves might be different between the coarse resolution set-ups (4°) and the higher resolution set-ups (2° and 1°). The ocean-atmosphere interactions are strongly enhanced in the highest resolution set-up (1°), with the development of a significant correlation of about 0

  18. Detection and Modeling of Non-Tidal Oceanic Effects on the Earth's Rotation Rate

    NASA Technical Reports Server (NTRS)

    Marcus, S. L.; Chao, Y.; Dickey, J. O.; Gegout, P.

    1998-01-01

    Sub-decadal changes in the Earth's rotation rate, and hence in the length-of-day (LOD), are largely controlled by variations in atmospheric angular momentum. Results from two oceanic general circulation models (OGCMs), forced by observed wind stress and heat flux for the years 1992-1994, show that ocean current and mass distribution changes also induce detectable LOD variations.

  19. Customised search and comparison of in situ, satellite and model data for ocean modellers

    NASA Astrophysics Data System (ADS)

    Hamre, Torill; Vines, Aleksander; Lygre, Kjetil

    2014-05-01

    For the ocean modelling community, the amount of available data from historical and upcoming in situ sensor networks and satellite missions, provides an rich opportunity to validate and improve their simulation models. However, the problem of making the different data interoperable and intercomparable remains, due to, among others, differences in terminology and format used by different data providers and the different granularity provided by e.g. in situ data and ocean models. The GreenSeas project (Development of global plankton data base and model system for eco-climate early warning) aims to advance the knowledge and predictive capacities of how marine ecosystems will respond to global change. In the project, one specific objective has been to improve the technology for accessing historical plankton and associated environmental data sets, along with earth observation data and simulation outputs. To this end, we have developed a web portal enabling ocean modellers to easily search for in situ or satellite data overlapping in space and time, and compare the retrieved data with their model results. The in situ data are retrieved from a geo-spatial repository containing both historical and new physical, biological and chemical parameters for the Southern Ocean, Atlantic, Nordic Seas and the Arctic. The satellite-derived quantities of similar parameters from the same areas are retrieved from another geo-spatial repository established in the project. Both repositories are accessed through standard interfaces, using the Open Geospatial Consortium (OGC) Web Map Service (WMS) and Web Feature Service (WFS), and OPeNDAP protocols, respectively. While the developed data repositories use standard terminology to describe the parameters, especially the measured in situ biological parameters are too fine grained to be immediately useful for modelling purposes. Therefore, the plankton parameters were grouped according to category, size and if available by element. This grouping

  20. Arctic Amplification Feedback Analysis in CMIP5 Models: Land Surfaces, Arctic Ocean and Seasonality

    NASA Astrophysics Data System (ADS)

    Laine, A.; Yoshimori, M.; Abe-Ouchi, A.

    2014-12-01

    The Arctic region is the region where surface warming associated with atmospheric green-house gas concentration increase is expected to be the greatest. This particularity is already being observed currently and is also simulated by climate models. Feedback mechanisms associated with this particularly strong warming, or Artic Amplification, are multiple. The relative role of the different feedbacks are not easy to evaluate precisely using direct model outputs. In this study, we use the "radiative kernels" method (Soden et al, 2008) to perform a multi-model intercomparison analysis. The radiative decomposition is performed at the surface instead of the top of atmosphere in order to consider surface temperature changes specifically. The kernels are derived from the MIROC3.2 model. The intercomparison includes 32 CMIP5 coupled models, whose outputs are analyzed for changes from the late 20th to the late 21st centuries following the rcp4.5 scenario. We consider results separately for land and oceanic surfaces, as the mechanisms and orders of magnitude differ substantially for these two types of surface. We also consider seasons separately as we show that seasonality in the feedback processes is determinant.

  1. A comprehensive validation toolbox for regional ocean models - Outline, implementation and application to the Baltic Sea

    NASA Astrophysics Data System (ADS)

    Jandt, Simon; Laagemaa, Priidik; Janssen, Frank

    2014-05-01

    The systematic and objective comparison between output from a numerical ocean model and a set of observations, called validation in the context of this presentation, is a beneficial activity at several stages, starting from early steps in model development and ending at the quality control of model based products delivered to customers. Even though the importance of this kind of validation work is widely acknowledged it is often not among the most popular tasks in ocean modelling. In order to ease the validation work a comprehensive toolbox has been developed in the framework of the MyOcean-2 project. The objective of this toolbox is to carry out validation integrating different data sources, e.g. time-series at stations, vertical profiles, surface fields or along track satellite data, with one single program call. The validation toolbox, implemented in MATLAB, features all parts of the validation process - ranging from read-in procedures of datasets to the graphical and numerical output of statistical metrics of the comparison. The basic idea is to have only one well-defined validation schedule for all applications, in which all parts of the validation process are executed. Each part, e.g. read-in procedures, forms a module in which all available functions of this particular part are collected. The interface between the functions, the module and the validation schedule is highly standardized. Functions of a module are set up for certain validation tasks, new functions can be implemented into the appropriate module without affecting the functionality of the toolbox. The functions are assigned for each validation task in user specific settings, which are externally stored in so-called namelists and gather all information of the used datasets as well as paths and metadata. In the framework of the MyOcean-2 project the toolbox is frequently used to validate the forecast products of the Baltic Sea Marine Forecasting Centre. Hereby the performance of any new product

  2. Ocean rogue waves and their phase space dynamics in the limit of a linear interference model

    NASA Astrophysics Data System (ADS)

    Birkholz, Simon; Brée, Carsten; Veselić, Ivan; Demircan, Ayhan; Steinmeyer, Günter

    2016-10-01

    We reanalyse the probability for formation of extreme waves using the simple model of linear interference of a finite number of elementary waves with fixed amplitude and random phase fluctuations. Under these model assumptions no rogue waves appear when less than 10 elementary waves interfere with each other. Above this threshold rogue wave formation becomes increasingly likely, with appearance frequencies that may even exceed long-term observations by an order of magnitude. For estimation of the effective number of interfering waves, we suggest the Grassberger-Procaccia dimensional analysis of individual time series. For the ocean system, it is further shown that the resulting phase space dimension may vary, such that the threshold for rogue wave formation is not always reached. Time series analysis as well as the appearance of particular focusing wind conditions may enable an effective forecast of such rogue-wave prone situations. In particular, extracting the dimension from ocean time series allows much more specific estimation of the rogue wave probability.

  3. Ocean rogue waves and their phase space dynamics in the limit of a linear interference model

    PubMed Central

    Birkholz, Simon; Brée, Carsten; Veselić, Ivan; Demircan, Ayhan; Steinmeyer, Günter

    2016-01-01

    We reanalyse the probability for formation of extreme waves using the simple model of linear interference of a finite number of elementary waves with fixed amplitude and random phase fluctuations. Under these model assumptions no rogue waves appear when less than 10 elementary waves interfere with each other. Above this threshold rogue wave formation becomes increasingly likely, with appearance frequencies that may even exceed long-term observations by an order of magnitude. For estimation of the effective number of interfering waves, we suggest the Grassberger-Procaccia dimensional analysis of individual time series. For the ocean system, it is further shown that the resulting phase space dimension may vary, such that the threshold for rogue wave formation is not always reached. Time series analysis as well as the appearance of particular focusing wind conditions may enable an effective forecast of such rogue-wave prone situations. In particular, extracting the dimension from ocean time series allows much more specific estimation of the rogue wave probability. PMID:27731411

  4. Ocean rogue waves and their phase space dynamics in the limit of a linear interference model.

    PubMed

    Birkholz, Simon; Brée, Carsten; Veselić, Ivan; Demircan, Ayhan; Steinmeyer, Günter

    2016-10-12

    We reanalyse the probability for formation of extreme waves using the simple model of linear interference of a finite number of elementary waves with fixed amplitude and random phase fluctuations. Under these model assumptions no rogue waves appear when less than 10 elementary waves interfere with each other. Above this threshold rogue wave formation becomes increasingly likely, with appearance frequencies that may even exceed long-term observations by an order of magnitude. For estimation of the effective number of interfering waves, we suggest the Grassberger-Procaccia dimensional analysis of individual time series. For the ocean system, it is further shown that the resulting phase space dimension may vary, such that the threshold for rogue wave formation is not always reached. Time series analysis as well as the appearance of particular focusing wind conditions may enable an effective forecast of such rogue-wave prone situations. In particular, extracting the dimension from ocean time series allows much more specific estimation of the rogue wave probability.

  5. Use of weather research and forecasting model outputs to obtain near-surface refractive index structure constant over the ocean.

    PubMed

    Qing, Chun; Wu, Xiaoqing; Li, Xuebin; Zhu, Wenyue; Qiao, Chunhong; Rao, Ruizhong; Mei, Haipin

    2016-06-13

    The methods to obtain atmospheric refractive index structure constant (Cn2) by instrument measurement are limited spatially and temporally and they are more difficult and expensive over the ocean. It is useful to forecast Cn2 effectively from Weather Research and Forecasting Model (WRF) outputs. This paper introduces a method that WRF Model is used to forecast the routine meteorological parameters firstly, and then Cn2 is calculated based on these parameters by the Bulk model from the Monin-Obukhov similarity theory (MOST) over the ocean near-surface. The corresponding Cn2 values measured by the micro-thermometer which is placed on the ship are compared with the ones forecasted by WRF model to determine how this method performs. The result shows that the forecasted Cn2 is consistent with the measured Cn2 in trend and the order of magnitude as a whole, as well as the correlation coefficient is up to 77.57%. This method can forecast some essential aspects of Cn2 and almost always captures the correct magnitude of Cn2, which experiences fluctuations of two orders of magnitude. Thus, it seems to be a feasible and meaningful method that using WRF model to forecast near-surface Cn2 value over the ocean.

  6. Empirical and modeled synoptic cloud climatology of the Arctic Ocean

    NASA Technical Reports Server (NTRS)

    Barry, R. G.; Newell, J. P.; Schweiger, A.; Crane, R. G.

    1986-01-01

    A set of cloud cover data were developed for the Arctic during the climatically important spring/early summer transition months. Parallel with the determination of mean monthly cloud conditions, data for different synoptic pressure patterns were also composited as a means of evaluating the role of synoptic variability on Arctic cloud regimes. In order to carry out this analysis, a synoptic classification scheme was developed for the Arctic using an objective typing procedure. A second major objective was to analyze model output of pressure fields and cloud parameters from a control run of the Goddard Institue for Space Studies climate model for the same area and to intercompare the synoptic climatatology of the model with that based on the observational data.

  7. Wind driven general circulation of the Mediterranean Sea simulated with a Spectral Element Ocean Model

    NASA Astrophysics Data System (ADS)

    Molcard, A.; Pinardi, N.; Iskandarani, M.; Haidvogel, D. B.

    2002-05-01

    This work is an attempt to simulate the Mediterranean Sea general circulation with a Spectral Finite Element Model. This numerical technique associates the geometrical flexibility of the finite elements for the proper coastline definition with the precision offered by spectral methods. The model is reduced gravity and we study the wind-driven ocean response in order to explain the large scale sub-basin gyres and their variability. The study period goes from January 1987 to December 1993 and two forcing data sets are used. The effect of wind variability in space and time is analyzed and the relationship between wind stress curl and ocean response is stressed. Some of the main permanent structures of the general circulation (Gulf of Lions cyclonic gyre, Rhodes gyre, Gulf of Syrte anticylone) are shown to be induced by permanent wind stress curl structures. The magnitude and spatial variability of the wind is important in determining the appearance or disappearance of some gyres (Tyrrhenian anticyclonic gyre, Balearic anticyclonic gyre, Ionian cyclonic gyre). An EOF analysis of the seasonal variability indicates that the weakening and strengthening of the Levantine basin boundary currents is a major component of the seasonal cycle in the basin. The important discovery is that seasonal and interannual variability peak at the same spatial scales in the ocean response and that the interannual variability includes the change in amplitude and phase of the seasonal cycle in the sub-basin scale gyres and boundary currents. The Coriolis term in the vorticity balance seems to be responsible for the weakening of anticyclonic structures and their total disappearance when they are close to a boundary. The process of adjustment to winds produces a train of coastally trapped gravity waves which travel around the eastern and western basins, respectively in approximately 6 months. This corresponds to a phase velocity for the wave of about 1 m/s, comparable to an average velocity of

  8. Oceanic influence on seasonal malaria outbreaks over Senegal and Sahel. Predictability using S4CAST model

    NASA Astrophysics Data System (ADS)

    Diouf, Ibrahima; Deme, Abdoulaye; Rodriguez-Fonseca, Belen; Suárez-Moreno, Roberto; Cisse, Moustapha; Ndione, Jacques-André; Thierno Gaye, Amadou

    2014-05-01

    Senegal and, in general, West African regions are affected by important outbreaks of diseases with destructive consequences for human population, livestock and country's economy. The vector-borne diseases such as mainly malaria, Rift Valley Fever and dengue are affected by the interanual to decadal variability of climate. Analysis of the spatial and temporal variability of climate parameters and associated oceanic patterns is important in order to assess the climate impact on malaria transmission. In this study, the approach developed to study the malaria-climate link is predefined by the QWeCI project (Quantifying Weather and Climate Impacts on Health in Developing Countries). Preliminary observations and simulations results over Senegal Ferlo region, confirm that the risk of malaria transmission is mainly linked to climate parameters such as rainfall, temperature and relative humidity; and a lag of one to two months between the maximum of malaria and the maximum of climate parameters as rainfall is observed. As climate variables are able to be predicted from oceanic SST variability in remote regions, this study explores seasonal predictability of malaria incidence outbreaks from previous sea surface temperatures conditions in different ocean basins. We have found causal or coincident relationship between El Niño and malaria parameters by coupling LMM UNILIV malaria model and S4CAST statistiscal model with the aim of predicting the malaria parameters with more than 6 months in advance. In particular, El Niño is linked to an important decrease of the number of mosquitoes and the malaria incidence. Results from this research, after assessing the seasonal malaria parameters, are expected to be useful for decision makers to better access to climate forecasts and application on health in the framework of rolling back malaria transmission.

  9. Carbon dioxide induced ocean climatic change and tracer experiment with an atmosphere-ocean general circulation model

    SciTech Connect

    Jiang, Xingjian.

    1991-01-01

    The principal objective of this study is to determine whether or not the penetration of a passive tracer is analogous to the penetration of a greenhouse-gas-induced heating. The Atmosphere Ocean General Circulation Model (A-O GCM) has been used to study CO2-induced climate change and the penetration of passive tracers into the world ocean. The present climate and a 2 x CO2 climate have been simulated. The passive tracers tritium, CFC-11, CFC-12 and a 'passive CO2- induced heating' are simulated. The CO2-induced active and passive warmings are larger in the subtropics and high latitudes than in the tropics. The largest difference between the active and passive CO2-induced heatings occur in the North Atlantic deep ocean, with maximum cooling about -1.5C for the active case in layer four of the ocean (1150m). There is no hemispherically asymmetric warming as that found by Manabe et al. (1990) and Stouffer et al. (1990). The convective overturning and large-scale sinking motion are responsible for the large penetration of CO2-induced warming in high latitudes. The CO2-induced circulation changes show that the North Atlantic thermohaline circulation is significantly weakened due to the penetration of CO2-induced heating. Associated with this change, the strength of North Atlantic conveyor belt is reduced, which results in a large warming in the upper ocean and cooling in the deep layers. The characteristic response time ranges from 40-50 years for the active CO2-induced climate change, and 70-160 years for passive CO2-induced climate change. The physical processes controlling the geochemical tracer penetration are very similar to those for the CO2-induced heating. There is not a single tracer which penetrates into the ocean exactly like the active CO2-induced heating in terms of distribution, transport or physical process. CFC's may be the best candidate as a surrogate for the CO2-induced oceanic climate study.

  10. Distribution of carbon isotopes in the glacial ocean: A model study

    NASA Astrophysics Data System (ADS)

    Crucifix, Michel

    2005-12-01

    A series of simulations are conducted with a global climate model of intermediate complexity (MoBidiC). This model includes ocean circulation dynamics, including the carbon cycle, coupled to a zonally averaged atmosphere. Oceanic distributions of nutrients, apparent oxygen utilization, radiocarbon, and carbon 13 are discussed for the preindustrial era (validation) as well as three states of the glacial ocean, termed interstadial (very active formation of deep water in the North Atlantic Ocean), stadial (moderate convection and important flow of Antarctic Deep Water in the Atlantic), and Heinrich (no formation of North Atlantic Deep Water). The stadial and interstadial states are stable. The Heinrich state is forced by a continuous freshwater discharge into the North Atlantic. The model exhibits significant changes in the isotopic composition of the ocean between the three modeled glacial states. Results for δ13C tend to be in qualitative agreement with paleoceanographic data, except that the model fails at representing the strong depletion in δ13C in the Southern Ocean. The Heinrich Atlantic Ocean is older than the stadial ocean at all depths (up to 1500 years). The "interstadial" ocean has younger deep water and older intermediate water than the "stadial." It is recognized that the simulated changes in intermediate water age are less reliable because of the structure of the model. Color tracers are used to show that changes in the isotopic composition of Atlantic bottom water are mainly related to a redistribution of water masses. A simple method is tested, by which it is possible to reconstruct the North Atlantic water flow from the zonal profiles of salinity and Δ14C. Finally, dividing artificially the gas exchange rate in the Southern Ocean by four results in a 0.4‰ decrease in the δ13C of Antarctic Bottom Water. Changes in new production are, comparatively, less effective at altering the δ13C ratio.

  11. Integrating functional diversity, food web processes, and biogeochemical carbon fluxes into a conceptual approach for modeling the upper ocean in a high-CO2 world

    NASA Astrophysics Data System (ADS)

    Legendre, Louis; Rivkin, Richard B.

    2005-09-01

    Marine food webs influence climate by channeling carbon below the permanent pycnocline, where it can be sequestered. Because most of the organic matter exported from the euphotic zone is remineralized within the "upper ocean" (i.e., the water column above the depth of sequestration), the resulting CO2 would potentially return to the atmosphere on decadal timescales. Thus ocean-climate models must consider the cycling of carbon within and from the upper ocean down to the depth of sequestration, instead of only to the base of the euphotic zone. Climate-related changes in the upper ocean will influence the diversity and functioning of plankton functional types. In order to predict the interactions between the changing climate and the ocean's biology, relevant models must take into account the roles of functional biodiversity and pelagic ecosystem functioning in determining the biogeochemical fluxes of carbon. We propose the development of a class of models that consider the interactions, in the upper ocean, of functional types of plankton organisms (e.g., phytoplankton, heterotrophic bacteria, microzooplankton, large zooplankton, and microphagous macrozooplankton), food web processes that affect organic matter (e.g., synthesis, transformation, and remineralization), and biogeochemical carbon fluxes (e.g., photosynthesis, calcification, respiration, and deep transfer). Herein we develop a framework for this class of models, and we use it to make preliminary predictions for the upper ocean in a high-CO2 world, without and with iron fertilization. Finally, we suggest a general approach for implementing our proposed class of models.

  12. Quantifying Key Climate Parameter Uncertainties Using an Earth System Model with a Dynamic 3D Ocean

    NASA Astrophysics Data System (ADS)

    Olson, R.; Sriver, R. L.; Goes, M. P.; Urban, N.; Matthews, D.; Haran, M.; Keller, K.

    2011-12-01

    Climate projections hinge critically on uncertain climate model parameters such as climate sensitivity, vertical ocean diffusivity and anthropogenic sulfate aerosol forcings. Climate sensitivity is defined as the equilibrium global mean temperature response to a doubling of atmospheric CO2 concentrations. Vertical ocean diffusivity parameterizes sub-grid scale ocean vertical mixing processes. These parameters are typically estimated using Intermediate Complexity Earth System Models (EMICs) that lack a full 3D representation of the oceans, thereby neglecting the effects of mixing on ocean dynamics and meridional overturning. We improve on these studies by employing an EMIC with a dynamic 3D ocean model to estimate these parameters. We carry out historical climate simulations with the University of Victoria Earth System Climate Model (UVic ESCM) varying parameters that affect climate sensitivity, vertical ocean mixing, and effects of anthropogenic sulfate aerosols. We use a Bayesian approach whereby the likelihood of each parameter combination depends on how well the model simulates surface air temperature and upper ocean heat content. We use a Gaussian process emulator to interpolate the model output to an arbitrary parameter setting. We use Markov Chain Monte Carlo method to estimate the posterior probability distribution function (pdf) of these parameters. We explore the sensitivity of the results to prior assumptions about the parameters. In addition, we estimate the relative skill of different observations to constrain the parameters. We