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Sea State Forecast System in IOLR
System Description

 The IOLR sea state forecasting system is based on the WAM model, which has been in development since 1984. World leading specialists in the field of sea waves (WAMDI group, 1988; Komen et al., 1994) participated in various stages of development.

 WAM is a phase averaging model, in other words WAM does not predict amplitudes and phases of individual waves but rather calculates the statistical description of the wave field in terms of the directional wave spectrum. WAM is considered as a third generation model, i. e. a model in which the investigators attempted to minimize ad hoc assumptions regarding the processes of energy transfer from wind to waves, as well as processes of wave energy dissipation. Only sea surface wind and topography are used as input for WAM. The model is intended to calculate the sea state both in deep water and in the shoaling zone outside the wave breaking area. The last WAM version (Cycle 4. Günter et al., 1991) is implemented in marine operational forecasting centers such as ECMWF and the University of Athens both on global and regional scales.

 At IOLR the model is used for hindcasting (Gertman et al., 2000) as well as for operational forecasting of wind waves in deep water regions of the Mediterranean. The model runs on a coarse space grid with a resolution of 0.5° for the entire Mediterranean Sea as well as on a fine grid with a resolution of 0.125° for the Eastern Mediterranean (east of 22°E). On both grids directional wave spectra are calculated using 25 frequencies between 0.042Hz and 0.42Hz; and 24 directions (every 15°). The system uses wind fields at 10 m above sea surface, provided by The University of Athens's Atmospheric Modeling and Weather Forecasting Group led by Prof. G. Kallos (SKIRON Regional meteorological model). WAM, governed by SKIRON's winds, runs daily on a LINUX workstation, and requires about 12 minutes to produce 120 hours wave forecast.

Acknowledgements

  • The development of the system has been partially funded by the Israel Ministry of Defense.
  • We gratefully acknowledge Prof. Kallos for his collaboration and the provision of wind fields in operational mode.
  • Special thanks for Prof. Günter for providing FORTRAN 90 WAM code and his explanations of the distinction between the wave fields calculated with different WAM codes.

References:

  • Günter, H., S. Hasselmann and P.A.E.M. Janssen. (1991). ”Wamodel cycle 4”, DKRZ report no. 4, Hamburg.
  • Komen, G.J., L. Cavaleri, M. Donelan, K. Hasselmann, S. Hasselmann and P.A.E.M. Janssen. (1994). “Dynamics and Modeling of Ocean Waves”, Cambridge Univ. Press., pp.532.
  • Gertman, I., A. Murashkovsky, V. Levin, G. Kallos, and D.S. Rosen, (2005). "Wave monitoring and wind input as key issues in operational wave forecasting systems". In "European Operational Oceanography: Present and Future", pp. 743-749
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