New parameterizations of source terms in the NEDWAM wave model

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New parameterizations of source terms in the
NEDWAM wave model
Masters Thesis

• Marianne den Ouden
• KNMI and IMAU

Supervisors V.K. Makin, J.W. de Vries, and P.J.
van Leeuwen
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Overview

• Introduction
• Background information
• Experimental set up
• Results
• Conclusion

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Introduction

• Wave modelling
• NEDWAM
• Research

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Introduction-Wave modeling
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Introduction-NEDWAM

• Grid spacing
• 1/3 in latitudinal direction
• 1/2 in longitudinal direction
• (grid size 32 km)

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Introduction-Research

• Wind-over-waves coupling theory (WOWC)
• New parameterization sea drag, wind input source
  term, and dissipation source term.
• Analysis of several wave parameters.

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Background information

• General physics
• Original vs new NEDWAM parameterizations
• Sea drag
• Wind input source term
• Dissipation souce term
• Wave parameters
• Statistics

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Background information

• Statistical description wave field
• Two scale approach

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Background information - General physicsWave
variance spectrum

• Covariance function
• Wave variance spectrum
• Frequency-directional spectrum
• Dispersion relation or for deep water
• Energy density

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Background information Original NEDWAM
parameterizationsWind input

• with
• and

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Background information Original NEDWAM
parameterizationsDissipation

• with
• and

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Background information Original NEDWAM
parameterizationsBottom dissipation

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Background information Original NEDWAM
parameterizationsNon-linear interaction

• Redistribute energy to smooth wave spectrum
• Parameterization based on a general perturbation
  theory

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Background information New physicsDrag
coefficient

• with
• and

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Background information New physicsWind input
source term

• with
• and

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Background information New physicsDissipation
source term

• with
• and

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Background information Wave parameters

• Significant wave height Hs

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Background information Wave parametersSeparatio
n frequency

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Background information Statistics

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Experimental set up

• Set up
• Wind input

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Experimental set up

• Period
• Stations

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Experimental set up-Wind

• HIRLAM 4.3
• HIRLAM 5.0
• HIRLAM 6.3

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Experimental set up-Wind
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Results

• Establishing a representative data set
• Model comparison
• Specific circumstances
• Different time periods
• Different wind input

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Results-Establishing a representative data
setTotal spectrum
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Results-Establishing a representative data
setSwell
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Results-Establishing a representative data
setSwell
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Results-Establishing a representative data
setSwell
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Results-Establishing a representative data
setWind waves
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Results-Establishing a representative data
setWind waves
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Results-Model comparisonSignificant wave height
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Results-Model comparisonSwell
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Results-Model comparisonWind waves
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Results-Specific circumstances

• Scenario a
• Scenario b
• Scenario c
• Scenario d

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Results-Specific circumstances
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Results-Specific circumstances
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Conclusion

• Wind input responsible for forecasting error
• Swell difficult to forecast
• New parameterizations desirable

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Bibliography (1)
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Bibliography (2)