The Experts below are selected from a list of 114 Experts worldwide ranked by ideXlab platform

A D Kirwan - One of the best experts on this subject based on the ideXlab platform.

  • reconstruction of Oceanic Flow characteristics from quasi lagrangian data 1 approach and mathematical methods
    Journal of Geophysical Research, 1992
    Co-Authors: V N Eremeev, L M Ivanov, A D Kirwan
    Abstract:

    We describe a nontraditional method for processing data derived from quasi-Lagrangian tracers. The approach relies on a representation of the thermohydrodynamic field as a set of a finite number of functions (modes) with the subsequent computation of mode amplitudes from quasi-Lagrangian data. This requires special methods for calculating mode components of the thermohydrodynamic field from Lagrangian observations. Also, because of the quasi-Lagrangian nature of the data there are special problems caused by the need to filter in both space and time and to account for motions unresolved by such observations. The former problem is addressed by a filtering procedure based on a variational criteria and Pontryagin's principle. To handle the latter problem, a subgrid parameterization scheme appropriate for Lagrangian data is proposed.

  • reconstruction of Oceanic Flow characteristics from quasi lagrangian data 2 characteristics of the large scale circulation in the black sea
    Journal of Geophysical Research, 1992
    Co-Authors: V N Eremeev, L M Ivanov, A D Kirwan, Oleg Melnichenko, S V Kochergin, R R Stanichnaya
    Abstract:

    The circulation in the western portion of the Black Sea in 1987 is assessed from surface drifter trajectories, climatological data, and numerical modeling. These diverse data sources are combined by the paradigm reported in the companion article. The primary emphasis is on the low-frequency and wave number circulation characteristics. The analysis suggests that in the Black Sea there may be a seasonal change in the direction of the large-scale circulation.

V N Eremeev - One of the best experts on this subject based on the ideXlab platform.

  • reconstruction of Oceanic Flow characteristics from quasi lagrangian data 1 approach and mathematical methods
    Journal of Geophysical Research, 1992
    Co-Authors: V N Eremeev, L M Ivanov, A D Kirwan
    Abstract:

    We describe a nontraditional method for processing data derived from quasi-Lagrangian tracers. The approach relies on a representation of the thermohydrodynamic field as a set of a finite number of functions (modes) with the subsequent computation of mode amplitudes from quasi-Lagrangian data. This requires special methods for calculating mode components of the thermohydrodynamic field from Lagrangian observations. Also, because of the quasi-Lagrangian nature of the data there are special problems caused by the need to filter in both space and time and to account for motions unresolved by such observations. The former problem is addressed by a filtering procedure based on a variational criteria and Pontryagin's principle. To handle the latter problem, a subgrid parameterization scheme appropriate for Lagrangian data is proposed.

  • reconstruction of Oceanic Flow characteristics from quasi lagrangian data 2 characteristics of the large scale circulation in the black sea
    Journal of Geophysical Research, 1992
    Co-Authors: V N Eremeev, L M Ivanov, A D Kirwan, Oleg Melnichenko, S V Kochergin, R R Stanichnaya
    Abstract:

    The circulation in the western portion of the Black Sea in 1987 is assessed from surface drifter trajectories, climatological data, and numerical modeling. These diverse data sources are combined by the paradigm reported in the companion article. The primary emphasis is on the low-frequency and wave number circulation characteristics. The analysis suggests that in the Black Sea there may be a seasonal change in the direction of the large-scale circulation.

L M Ivanov - One of the best experts on this subject based on the ideXlab platform.

  • reconstruction of Oceanic Flow characteristics from quasi lagrangian data 1 approach and mathematical methods
    Journal of Geophysical Research, 1992
    Co-Authors: V N Eremeev, L M Ivanov, A D Kirwan
    Abstract:

    We describe a nontraditional method for processing data derived from quasi-Lagrangian tracers. The approach relies on a representation of the thermohydrodynamic field as a set of a finite number of functions (modes) with the subsequent computation of mode amplitudes from quasi-Lagrangian data. This requires special methods for calculating mode components of the thermohydrodynamic field from Lagrangian observations. Also, because of the quasi-Lagrangian nature of the data there are special problems caused by the need to filter in both space and time and to account for motions unresolved by such observations. The former problem is addressed by a filtering procedure based on a variational criteria and Pontryagin's principle. To handle the latter problem, a subgrid parameterization scheme appropriate for Lagrangian data is proposed.

  • reconstruction of Oceanic Flow characteristics from quasi lagrangian data 2 characteristics of the large scale circulation in the black sea
    Journal of Geophysical Research, 1992
    Co-Authors: V N Eremeev, L M Ivanov, A D Kirwan, Oleg Melnichenko, S V Kochergin, R R Stanichnaya
    Abstract:

    The circulation in the western portion of the Black Sea in 1987 is assessed from surface drifter trajectories, climatological data, and numerical modeling. These diverse data sources are combined by the paradigm reported in the companion article. The primary emphasis is on the low-frequency and wave number circulation characteristics. The analysis suggests that in the Black Sea there may be a seasonal change in the direction of the large-scale circulation.

Fitch Robert - One of the best experts on this subject based on the ideXlab platform.

  • 3D Ensemble-Based Online Oceanic Flow Field Estimation for Underwater Glider Path Planning
    2021
    Co-Authors: Kong, Felix H., To K. Y. Cadmus, Brassington Gary, Anstee Stuart, Fitch Robert
    Abstract:

    Estimating ocean Flow fields in 3D is a critical step in enabling the reliable operation of underwater gliders and other small, low-powered autonomous marine vehicles. Existing methods produce depth-averaged 2D layers arranged at discrete vertical intervals, but this type of estimation can lead to severe navigation errors. Based on the observation that real-world ocean currents exhibit relatively low velocity vertical components, we propose an accurate 3D estimator that extends our previous work in estimating 2D Flow fields as a linear combination of basis Flows. The proposed algorithm uses data from ensemble forecasting to build a set of 3D basis Flows, and then iteratively updates basis coefficients using point measurements of underwater currents. We report results from experiments using actual ensemble forecasts and synthetic measurements to compare the performance of our method to the direct 3D extension of the previous work. These results show that our method produces estimates with dramatically lower error metrics, with and without measurement noise.Comment: Submitted to IROS 202

  • Estimation of Spatially Correlated Ocean Currents from Ensemble Forecasts and Online Measurements
    2021
    Co-Authors: To K. Y. Cadmus, Kong, Felix H., Anstee Stuart, Lee, Ki Myung Brian, Yoo Chanyeol, Fitch Robert
    Abstract:

    We present a method to estimate two-dimensional, time-invariant Oceanic Flow fields based on data from both ensemble forecasts and online measurements. Our method produces a spatially coherent estimate in a computationally efficient manner suitable for use in marine robotics for path planning and related applications. We use kernel methods and singular value decomposition to find a compact model of the ensemble data that is represented as a linear combination of basis Flow fields and that preserves the spatial correlations present in the data. Online measurements of ocean current, taken for example by marine robots, can then be incorporated using recursive Bayesian estimation. We provide computational analysis, performance comparisons with related methods, and demonstration with real-world ensemble data to show the computational efficiency and validity of our method. Possible applications in addition to path planning include active perception methods for model improvement through intentional choice of measurement locations.Comment: 7 pages, 6 figures, accepted to IEEE ICRA 202

Madec Gurvan - One of the best experts on this subject based on the ideXlab platform.

  • Development of a 2-way coupled ocean-wave model: assessment on a global NEMO(v3.6)-WW3(v6.02) coupled configuration
    'Copernicus GmbH', 2020
    Co-Authors: Couvelard Xavier, Lemarié Florian, Samson Guillaume, Redelsperger Jean-luc, Ardhuin Fabrice, Benshila Rachid, Madec Gurvan
    Abstract:

    International audienceThis paper describes the implementation of a coupling between a three-dimensional ocean general circulation model (NEMO) and a wave model (WW3) to represent the interactions of the upper Oceanic Flow dynamics with surface waves. The focus is on the impact of such coupling on upper-ocean properties (temperature and currents) and mixed-layer depths (MLD) at global eddying scales. A generic coupling interface has been developed and the NEMO governing equations and boundary conditions have been adapted to include wave-induced terms following the approach of McWilliams et al. (2004) and Ardhuin et al. (2008). In particular, the contributions of Stokes-Coriolis, Vortex and surface pressure forces have been implemented on top of the necessary modifications of the tracer/continuity equation and turbulent closure scheme (a 1-equation TKE closure here). To assess the new developments, we perform a set of sensitivity experiments with a global Oceanic configuration at 1/4° resolution coupled with a wave model configured at 1/2° resolution. Numerical simulations show a global increase of wind-stress due to the interaction with waves (via the Charnock coefficient) particularly at high latitudes, resulting in increased surface currents. The modifications brought to the TKE closure scheme and the inclusion of a parameterization for Langmuir turbulence lead to a significant increase of the mixing thus helping to deepen the MLD. This deepening is mainly located in the Southern Hemisphere and results in reduced sea-surface currents and temperatures

  • Development of a two-way-coupled ocean–wave model: assessment on a global NEMO(v3.6)–WW3(v6.02) coupled configuration
    'Copernicus GmbH', 2020
    Co-Authors: Couvelard Xavier, Lemarié Florian, Samson Guillaume, Redelsperger Jean-luc, Ardhuin Fabrice, Benshila Rachid, Madec Gurvan
    Abstract:

    This paper describes the implementation of a coupling between a three-dimensional ocean general circulation model (NEMO) and a wave model (WW3) to represent the interactions of the upper Oceanic Flow dynamics with surface waves. The focus is on the impact of such coupling on upper-ocean properties (temperature and currents) and mixed-layer depths (MLD) at global eddying scales. A generic coupling interface has been developed and the NEMO governing equations and boundary conditions have been adapted to include wave-induced terms following the approach of McWilliams et al. (2004) and Ardhuin et al. (2008). In particular, the contributions of Stokes-Coriolis, Vortex and surface pressure forces have been implemented on top of the necessary modifications of the tracer/continuity equation and turbulent closure scheme (a 1-equation TKE closure here). To assess the new developments, we perform a set of sensitivity experiments with a global Oceanic configuration at 1/4° resolution coupled with a wave model configured at 1/2° resolution. Numerical simulations show a global increase of wind-stress due to the interaction with waves (via the Charnock coefficient) particularly at high latitudes. The modifications brought to the TKE closure scheme and the inclusion of a parameterization for Langmuir turbulence lead to a significant increase of the mixing thus helping to deepen the MLD. This deepening is mainly located in the Southern Hemisphere and results in reduced sea-surface currents and temperatures