The couple discrete deep-water wave model (WINCH) run at the Norwegian Meteorological Institute has been tested with wind input from the coarse- and the fine-meshed Norwegian Limited Area Atmospheric models, with 150 and 50 km grid resolution respectively. The systems are called LAM150 and LAM50.
The present study shows wave hindcast results for January 1987 compared to measurements performed with a directional wave buoy (WAVEC) and a microwave radar (MIROS).
The two measurement series were generally in agreement concerning significant wave height, peak period and peak wave direction in that period. A comparison between model results and observation shows that, for northerly winds, the model overestimates the waves in the northern North Sea, probably due to a combined effect of too slow damping of swell in the wave model and an overestimation of the wind.
Study of a sudden easterly outflow of cold air over southern Scandinavia that occurred on 9 and 10 January 1987, both in hindcast and forecast mode, shows the effectiveness of the finer scale atmospheric model to capture mesoscale phenomena. Underestimation of the wind speed in LAM150 causes underestimation of the wave height, while results using LAM50 winds are in good agreement with observations.
This chapter presents a validation of the WINCH operational wave model at the Norwegian Meteorological Institute. The model has been tested with wind input from two Limited Area Atmospheric models with different grid resolutions.
Validation of the model has been performed for grid points where directional wave measurements were available. This confines the study to two grid points of the wave model (1415 and 1361, see Fig 1), the first in the northern North Sea, approximately 11km from North Cormorant, where wave data from a WAVEC direction buoy were available, and 44 km from Gullfaks A, where wave data from a MIROS microwave radar were available. Wind observations were also obtained from the Statfjord A platform (see Fig 1). The wave model results from the second grid point are compared to MIROD data from the Statpipe platform 16/11.
Fig 1 Positions of grid points and measurement sites used for the validation study (available in full paper)
This study has concentrated on hindcast for January 1987 for several reasons.
the fine-meshed atmospheric model has been stored only since January 1987
the availability of directional data
January 1987 was a stormy month with several special events such as sudden 180° wind shifts and small-scaled intense low-pressure systems- a wave height of 4m was exceeded in the northern North Sea on seven occasions, and in three of these the height was about 7 m
One example of a run of the wave model in forecast mode is also presented.
The WINCH wave model implemented at DNMI is similar to the SAIL model which participated in the SWAMP experiment (SWAMP Group, 1984). It is of the discrete couple type with 15 frequency bands (0.04-0.239 Hz) and 24 directional bands (15° bandwidth).