Ocean forecasting in narrow shelf seas: application to the Spanish coasts

The continental shelf surrounding the Spanish coast is very narrow. This is of great importance when studying the wave and surge dynamics in the regio n and contrasts with other well-studied legions like the North Sea, both in the physics and in the modelling techniques applied to obtain predictions of waves and sea surface elevation at the coastline. This paper describes t hose differences and presents the approach to the problem implemented in th e wave and surge prediction system operational at Clima Maritimo (CM). The narrowness of the Spanish continental shelf requires very high resoluti on grids to be applied to localised regions near the coast. The usual confi guration of a local system nested to a global system (e.g. grids covering t he North Sea nested to the European Centre for Medium Range Weather Forecas ting global model) cannot be used in this case. Interpolation and coarse gr id errors from boundary conditions provided by a global grid very near the coast will not be corrected by a small-scale local application. It was foun d that self-contained systems, solving in the same run the basin and local scales by means of variable grid spacing techniques, were the optimal solut ion. Some new techniques were developed in the process (two-way nesting for the wave generation model, a transfer function technique for the wave spec tra) and implemented in the system. Although some of these developments hav e been already published [Gomez, M., Carretero, J.C., 1997. A two-way nesti ng procedure for the WAM model: application to the Spanish coast. J. Offsho re Mech. Arctic Eng. 119 (February 1997).], the final set-up of both system s is presented here for the first time. Both systems are regularly verified with experimental data from the Spanish network of buoy and tide gauges. R esults from this intercomparison are discussed in this paper. The PROMISE Spanish Coast Data Set was used to carry out much of the work p resented here (i.e. the forcing and validation of the surge prediction syst em). This is a collection of physical oceanographic and meteorological data in the Bay of Biscay during stormy periods from November 1995 to March 199 6. (C) 2000 Elsevier Science B.V. All rights reserved.