Ocean Science www.ocean-sci.net 1812-0784 1812-0792 5 2 2009 10.5194/os-5-73-2009 http://www.ocean-sci.net/5/73/2009/ http://www.ocean-sci.net/5/73/2009/os-5-73-2009.html http://www.ocean-sci.net/5/73/2009/os-5-73-2009.pdf 73 90 2009-04-27 "Scale oriented" embedded modeling of the North-Western Mediterranean in the frame of MFSTEP C. Estournel claude.estournel@aero.obs-mip.fr F. Auclair M. Lux C. Nguyen P. Marsaleix Pôle d'Océanographie Côtière de Toulouse – Laboratoire d'Aérologie, CNRS, Université de Toulouse, Toulouse, France Noveltis, Toulouse, France An embedded forecasting system was developed for the North-Western Mediterranean at 3-km resolution. The system is based on the Symphonie hydrodynamic free surface model and on the variational initialization and forcing platform VIFOP. The regional model is initialized and forced at its open lateral boundaries by the MFS GCM and forced at the surface by the ALADIN numerical weather prediction model. Once a week, a five-day forecast is produced after a hindcast of seven days. This pre-modeling period of 7 days before beginning the forecast allows the development of the small scale features associated to the high resolution. The relevance of the 5-day forecast strategy has been examined by comparing the forecasted fields to hindcast fields (forced by meteorological and oceanic analyses) considered as a reference. Mismatches remain at a very low level indicating a good quality of the forecasted forcing fields and also possibly to the strong wind conditions which prevailed during the period. The embedded forecasts have been compared to the MFS observing system (SST and MedArgo) during 6 forecast cycles between September 2004 and February 2005. 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