An integrated forecast system over the Mediterranean basin: extreme surge prediction in the northern Adriatic Sea

A previsional system for the forecast of the state of the Mediterranean Sea and of surges in the northern Adriatic Sea has been designed and tested. The system consists of a limited area model (the Bologna Limited Area Model, BOLAM), which computes high-resolution pressure and surface wind fields, to serve as the input of a wave model (WAM) and of a shallow water model (two-dimensional Princeton Ocean Model, POM-2D). Results of two case studies are presented, chosen to test the ability of the system to predict extreme surge events originating from cyclonic circulation over the Mediterranean basin. The two case studies cover the periods 4-9 October 1998 and 11-22 November 1996. Comparison with observed buoy data shows that the results of the WAM simulations forced by the wind fields obtained from the high-resolution BOLAM model are significantly better than those obtained using a lower-resolution forcing from the ECMWF analyses. Two domains corresponding to the entire Mediterranean basin and to the Adriatic-Ionian basin, respectively, have been used to run the POM-2D model. It is found that, in the Adriatic-Ionian run, the simulated sea elevation shows some discrepances in the amplitudes of the main peaks and in their phases, which are removed by extending the domain of integration to the entire Mediterranean. This better performance is due to the correct representation of the principal barotropic modes and of the pressure forcing on the basin.