DMI wave model predictions are compared with observed wave height at 3 sites: One off the Jutland west coast (Horns Rev 2), and two south of Lolland (Rødsand, Nysted).

We compare three versions of WAM:

• cycle 4.0, which has been running operationally at DMI since 1999
• cycle 4.5, which was installed in late 2008 and rerun from medio 2008
• cycle 4.5_fmin, where a lower spectral limit of 0.0001 ws imposed in order to ensure fast wave growth. This corresponds to a minimum wave height of 7 cm. Such a limiter is also present in cycle4.0.

The validation period is primo March 2009 - medio April 2009.

This is the first DMI validation of WAM in very shallow water. The water depth at Rødsand is about 5 meter. The results are depicted below.

Conclusions: 1) cycle4.0 and cycle4.5 are of similar quality, 2) the spectral limiter is crucial when waves have to build up from calm.

Jacob Woge - May 19th 2009