The National Wave Forecasting System in the Mediterranean and Italian Seas L. Bertotti, L. Cavaleri Institute of Marine Sciences, CNR, Venezia, Italy luciana.bertotti@ismar.cnr.it Abstract We describe the structure and the results of the national wave forecasting system, set-up by the Italian Meteorological Service CNMCA and ISMAR, operational since July 2008. After outlining the needs for an accurate prediction of the wind and wave conditions on the sea and the characteristics of the Mediterranean basin, we briefly describe the meteorological and wave models used for the purpose, and in greater details the quality of the results and what is presently available to the users. We conclude showing maps of the very severe storm that hit the western coasts of Italy in January 2009.
1
The need
The recent winter seasons, and in particular 2009, have seen a substantial increment of the severity of the sea storms that hit the Italian peninsula (see The Medatlas Group, 2004 for long term statistics). In the western part of the Mediterranean Sea, following the action of mistral, we have repetitively seen significant wave heights larger than 7 or 8 m. During the storm of 2425 January 2009 waves higher than 11 metres have been estimated in the basin (see later), with single wave heights larger than 20 m. Seven metre wave heights have been reached also in the Ligurian Sea, and similarly and repetitively also in the Ionian Sea. In the eastern Mediterranean violent storms have hit the area of the Nile delta. The correct prediction of the these events, particularly if extreme, is obviously a basic need for the safety of navigation and more in general for all the marine activities. Given the geometry of the basin, such information must be distributed with a very
high resolution to be able to consider its sometime cumbersome spatial variations, see [1, 2, 3]. The aim of this paper is to provide a compact, but clear, description of the highly accurate wave prediction system set-up through the collaborative action of the Italian Meteorological Service CNMCA and the Institute of Marine Sciences, ISMAR, of the Italian National Research Council. At this aim, after providing in Section 2 a compact description of the area of interest, namely the Mediterranean Sea, in 3 we briefly describe the models, meteorological and wave, we used. The results, both as statistics and examples, are given in Section 4. We summarise the situation in the final Section 5.
2
The Mediterranean Sea
The Mediterranean Sea is the largest enclosed basin in the world. It spans about 3,600 km in longitude and more than 1,600 in latitude. However, this large expanse