Numerical modelling of wind and wave conditions in the Red Sea

While wind and wave modelling is nowadys quite satisfactory in the open oceans, problems are still present in the enclosed seas, the more so the smaller the basin and the more complicated the surrounding orography. The Red Sea is an extreme example in this respect, especially because of its long and narrow shape. This deceivingly simple domain offers very interesting challenges for wind and wave modelling, not easily, if ever, found elsewhere. Depending on the season, opposite wind regimes, one direct to southeast, the other one to northwest, are present may coexist in the most northerly and southerly parts of the Red Sea. Where the two regimes meet, the wavespectra can be rather complicated and, crucially dependent on small details of the driving wind fields.

Using different meteorological products and wave models, we explored how well we could reproduce the general and unusual wind and wave patterns of the Red Sea. We obtained the best results using two rather opposite approaches; the high resolution Weather Research Forecasting (WRF) regional model and slightly enhanced surface winds from the global European Centre for Medium-Range Weather Forecasts (ECMWF) model. We discuss the reasons why this two approaches produce the best results and the implications on wave modelling in the Red Sea. The unusual wind and wave patterns in the Red Sea suggests that the currently available wave models source functions may not properly represent the evolution of local fields. However, within limits, the WAVEWATCH III wave model, based on Janssen's and also Ardhuin's wave model physics, provides in many cases very reasonable results.