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• the atmospheric forecast model at all configurations (ensemble control forecast, medium range ensemble, sub-seasonal range ensemble, seasonal ensemble) with resolution matching each model.
• the dynamic ocean model NEMO and SI3 sub-program.   (Note: the IFS analysis and the short range forecasts that are part of the IFS analysis cycle are not coupled with ECWAM).
  

ECWAM is solely concerned with ocean wave forecasting.  It does not model the ocean itself.  Dynamical modelling of the ocean is done by NEMO.

Ensemble structure

ECWAM evaluates the 2-dimensional surface wave spectrum for both oceanic and coastal (but not inshore) waters.  The wave information is output in 36 directions of propagation and 29 wave frequencies at 6hr intervals.  These describe the extent, severity and timing of the forecast wave energy and highlight risk areas.

The horizontal resolutions of ECWAM versions are the same as each of the atmospheric models with which they interact (~9km with ensemble control forecast and medium range forecasts, ~36km with sub-seasonal range and seasonal models).  Heat, moisture and momentum fluxes between atmosphere and ocean are included, depending on the sea state.  The land-sea masks match up with the atmospheric model versions in Cy50r1.

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ECWAM has two-way interaction with the Atmospheric models:

• ECWAM supplies surface roughness (according to the forecast sea state) which is used in the evaluation of boundary layer winds.
• Atmospheric models supply surface wind conditions, via surface stress, and this dominates sea-surface wave development.

ECWAM has two-way interaction with NEMO and sub-program SI3:

• ECWAM supplies surface stress, Stokes drift, and turbulent energy flux to the ocean surface.
• NEMO and sub-program SI3 supply information on the concentration and thickness of ice.

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Wavegram output on ecCharts

Wavegrams are available to show a time series of significant wave height, mean wave direction, and mean wave period for any sea location.

Fig2.3-4: Wavegrams for any oceanic location are available on ecCharts.  Choose location using the Probe icon (1); Click on "Views" (2); Select "Meteograms" option on the dropdown menu (3); Select "More" on the option page that appears(4); input Wave into the "Meteogram select" box (5); select desired chart(s) by clicking on the icon (6).

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Fig2.3-6: Sample wave chart. Click on any point to produce a meteogram and/or wavegram.

Fig2.3-7:  Wavegram on Opencharts associated with Fig2.3-6 at location near 52N 27W.

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Fig2.3-12:  Chart showing forecast significant wave heights for several ranges of wave periods (Blue,10-12s; Green,12-14s; Yellow,14-17s; Red,17-21s).  Forecast data based on data time 00UTC 25 October 2017.  The faster southward propagation of the long period waves over the shorter period waves from their source off NW Africa is clear.

The Extreme Forecast Index (EFI) can be used to indicate the significance of forecast significant wave heights when compared with the range of wave heights that might usually be expected as defined by the wave M-climate.

Fig2.3-13: In this example the colours west of Ireland denote a low-point in wave heights, or potentially a form of 'weather window' for certain types of marine/shipping operations.  Equally this EFI can signify periods with anomalously big waves (yellow to red shading).

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• Definitive information on the ECMWF WAVE MODEL products and availability can be found:
  • for Ensemble Control Forecast WAM in the Catalogue of ECMWF real-time products (Set II).
  • for Ensemble WAM in the Catalogue of ECMWF real-time products (Set IV)
• See IFS documentation part VII for extensive information on ECWAM model.
• Read more on ocean wave modelling and model output parameters.
• Read an in depth view of the structure of ECWAM which gives a description of the theory behind the ECWAM model.  Old but still relevant paper.
• Fact sheet - Ocean wave forecasting.
• ECMWF - Lead centre for wave forecast verification and information on national models and wave verification results. 
• Read about techniques regarding satellite measurement of wave height.
• Watch a comprehensive lecture on ocean wave forecasting at ECMWF or air-sea Interaction and earth system modelling.

(FUG Associated associated with Cy50r1)