The Experts below are selected from a list of 1803 Experts worldwide ranked by ideXlab platform

Christopher E Naimie - One of the best experts on this subject based on the ideXlab platform.

  • Hindcasting the georges bank circulation part ii wind band inversion
    Continental Shelf Research, 2002
    Co-Authors: Daniel R Lynch, Christopher E Naimie
    Abstract:

    Abstract Nonlinear inversion of velocity observations to produce limited-area circulation hindcasts is examined in the context of the USGLOBEC-Georges Bank surveys. Two linear inverses representing tide- and wind-band responses are used serially in an iteration with a nonlinear forward model. Both inverses are linearized about the nonlinear model. The objective is generalized least-squares fit; the controls are sea level elevation on the boundary of a limited-area mesh. The iteration converges rapidly provided a good prior estimate is available. Observational system simulation experiments address prediction skill for an idealized shelf regime and for an isolated wind event on Georges Bank. The idealized shelf inversion shows the limitations of extrapolative skill. For the wind event, skill is sensitive to the space-time locations of the observations. A real Georges Bank cruise, ENDEAVOR 261, is studied and the hindcast based on shipboard ADCP and moored data is assessed. The prior estimate based on climatology plus observed wind captured much of the tidal variability, most of the time-mean circulation, and little of the wind-band variability. The inversion improved the tidal fit, captured the wind-band variability, and did not degrade the mean.

  • Hindcasting the georges bank circulation part i detiding
    Continental Shelf Research, 1998
    Co-Authors: Daniel R Lynch, Christopher E Naimie, Charles G Hannah
    Abstract:

    Abstract Detiding of ADCP observations on Georges Bank is addressed using 3D circulation models and an iterative inversion strategy. The forward model is a nonlinear, time-domain finite element model with advanced turbulence closure. The inverse model is its linearized frequency domain counterpart. The inversion is focused on the deduction of boundary conditions for a limited-area model. Two different inversion strategies are described and tested. Robust smoothing parameters are selected based on the variance of boundary condition estimates. Test cases using model-generated output as “data” show the possibility of near-perfect inversion given realistic sampling of the bank; portions of the boundary which are poorly constrained by the sampling; and various sources of imperfection. The mismatched physics between forward and inverse models is shown to be diminished by iteration such that a nonlinear inverse is constructed. Inversion of real data – a 12-day cruise in April 1995 – is demonstrated. Prior error generated by climatology-based model solutions is 15 cm/s RMS.The inversion reduces this error to 8 cm/s, close to the minimum achievable based on tidal analysis of moored time series. The hindcast circulation shows important departures from the climatology, including a meander in the Northern Flank jet; a northward, off-bank transport from the Central Bank and Northeast Peak; and an on-bank intrusion along the Southern Flank.

Daniel R Lynch - One of the best experts on this subject based on the ideXlab platform.

  • Hindcasting the georges bank circulation part ii wind band inversion
    Continental Shelf Research, 2002
    Co-Authors: Daniel R Lynch, Christopher E Naimie
    Abstract:

    Abstract Nonlinear inversion of velocity observations to produce limited-area circulation hindcasts is examined in the context of the USGLOBEC-Georges Bank surveys. Two linear inverses representing tide- and wind-band responses are used serially in an iteration with a nonlinear forward model. Both inverses are linearized about the nonlinear model. The objective is generalized least-squares fit; the controls are sea level elevation on the boundary of a limited-area mesh. The iteration converges rapidly provided a good prior estimate is available. Observational system simulation experiments address prediction skill for an idealized shelf regime and for an isolated wind event on Georges Bank. The idealized shelf inversion shows the limitations of extrapolative skill. For the wind event, skill is sensitive to the space-time locations of the observations. A real Georges Bank cruise, ENDEAVOR 261, is studied and the hindcast based on shipboard ADCP and moored data is assessed. The prior estimate based on climatology plus observed wind captured much of the tidal variability, most of the time-mean circulation, and little of the wind-band variability. The inversion improved the tidal fit, captured the wind-band variability, and did not degrade the mean.

  • Hindcasting the georges bank circulation part i detiding
    Continental Shelf Research, 1998
    Co-Authors: Daniel R Lynch, Christopher E Naimie, Charles G Hannah
    Abstract:

    Abstract Detiding of ADCP observations on Georges Bank is addressed using 3D circulation models and an iterative inversion strategy. The forward model is a nonlinear, time-domain finite element model with advanced turbulence closure. The inverse model is its linearized frequency domain counterpart. The inversion is focused on the deduction of boundary conditions for a limited-area model. Two different inversion strategies are described and tested. Robust smoothing parameters are selected based on the variance of boundary condition estimates. Test cases using model-generated output as “data” show the possibility of near-perfect inversion given realistic sampling of the bank; portions of the boundary which are poorly constrained by the sampling; and various sources of imperfection. The mismatched physics between forward and inverse models is shown to be diminished by iteration such that a nonlinear inverse is constructed. Inversion of real data – a 12-day cruise in April 1995 – is demonstrated. Prior error generated by climatology-based model solutions is 15 cm/s RMS.The inversion reduces this error to 8 cm/s, close to the minimum achievable based on tidal analysis of moored time series. The hindcast circulation shows important departures from the climatology, including a meander in the Northern Flank jet; a northward, off-bank transport from the Central Bank and Northeast Peak; and an on-bank intrusion along the Southern Flank.

Reddy Nemalidinne - One of the best experts on this subject based on the ideXlab platform.

  • wave resource assessment for scottish waters using a large scale north atlantic spectral wave model
    Renewable Energy, 2015
    Co-Authors: Vengatesan Venugopal, Reddy Nemalidinne
    Abstract:

    This paper reports the methodology established in the application of a numerical wave model for Hindcasting of wave conditions around the United Kingdom, in particular for Scottish waters, for the purpose of wave energy resource assessment at potential device development sites. The phase averaged MIKE 21 Spectral wave model has been adopted for this study and applied to the North Atlantic region bounded by latitudes 10° N–70° N and longitudes 10° E−75° W. Spatial and temporal wind speeds extracted from the European Centre for Medium Range Weather Forecast (ECMWF) have been utilised to drive the wave model. A rigorous calibration and validation of the model has been carried out by comparing model results with buoy measurements for different time periods and locations around Scotland. Significant wave height, peak wave period and peak wave direction obtained from the model correlated very well with measurements. Spatially varying statistical mean and maximum values of the significant wave height and wave power obtained based on a one-year wave Hindcasting are in good agreement with the UK Marine Atlas values. The wave model can be used with high level of confidence for wave Hindcasting and even forecasting of various wave parameters and wave power at any desired point locations or for regions. The wave model could also be employed for generating boundary conditions to small scale regional wave and tidal flow models.

Charles G Hannah - One of the best experts on this subject based on the ideXlab platform.

  • Hindcasting the georges bank circulation part i detiding
    Continental Shelf Research, 1998
    Co-Authors: Daniel R Lynch, Christopher E Naimie, Charles G Hannah
    Abstract:

    Abstract Detiding of ADCP observations on Georges Bank is addressed using 3D circulation models and an iterative inversion strategy. The forward model is a nonlinear, time-domain finite element model with advanced turbulence closure. The inverse model is its linearized frequency domain counterpart. The inversion is focused on the deduction of boundary conditions for a limited-area model. Two different inversion strategies are described and tested. Robust smoothing parameters are selected based on the variance of boundary condition estimates. Test cases using model-generated output as “data” show the possibility of near-perfect inversion given realistic sampling of the bank; portions of the boundary which are poorly constrained by the sampling; and various sources of imperfection. The mismatched physics between forward and inverse models is shown to be diminished by iteration such that a nonlinear inverse is constructed. Inversion of real data – a 12-day cruise in April 1995 – is demonstrated. Prior error generated by climatology-based model solutions is 15 cm/s RMS.The inversion reduces this error to 8 cm/s, close to the minimum achievable based on tidal analysis of moored time series. The hindcast circulation shows important departures from the climatology, including a meander in the Northern Flank jet; a northward, off-bank transport from the Central Bank and Northeast Peak; and an on-bank intrusion along the Southern Flank.

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

  • wave Hindcasting off the coast of portugal
    Coastal Engineering, 2000
    Co-Authors: P Sebastiao, Guedes C Soares, N Booij
    Abstract:

    Abstract A study was conducted applying a second-generation wave model to predictions in coastal zones. The model was calibrated with wave measurements conducted off the Portuguese coast, for a period of 6 months. The wind fields used in the calculation were supplied by the European Centre for Medium Range Weather Forecast (ECMRWF). The calibrated model allows good predictions of significant wave height. Satisfactory comparisons have been made with predictions of the WAM model