Modelling tidal currents on the coast of Portugal

A tide circulation model of the Atlantic coast of the Iberian Peninsula has been constructed. This regional numerical model covers the whole continent al shelf. The finite element computational grid is made of some 16,300 tria ngular elements with sizes ranging between 13 km (on the offshore boundary) and 1 km (near the coast), with local refinements on the continental shelf and in the area of Figueira da Foz. This site was selected as experimental site for the study of waves and currents in the frame of the MAST2/WAVEMOD research project. Boundary conditions along the three oceanic limits of this widely open doma in are obtained from the North-Atlantic component of a World Ocean tidal nu merical model known as FES94 [Le Provost, C,, Genco, M,L., Lyard, F., Vince nt, P. and Canceil, P. (1994) Spectroscopy of the world ocean tides from a finite clement hydrodynamic model, Journal of Geophysical Research, Topex-P oseidon Special Issue]. A new radiation-like boundary condition has been in troduced in the modelling system used (Telemac-2D), which solves the Shallo w Water Equations (SWE), in order to inter face the two models and to allow for the tidal wave to leave the northern limit without reflection. Model c alibration has been performed on the dominating M-2 constituent. The introd uction of the astral static potential generating the tide in the SWE improv ed this regional model. A long duration run (1 month) has been performed, the model being forced by the eight major tide constituents. Harmonic analysis of results has been p erformed on 17 tide constituents, due to non-linear interactions of constit uents on the continental shelf. Comparisons with the FES94 model on one han d, and with a set of coastal tide gauges on the other hand, are good. A dat abase of tidal harmonics is now available fur forecasting sea levels and cu rrents in this area. This work has shown that diurnal shelf trapped tide waves exist in some pla ces along the Portuguese continental shelf, which induce diurnal dominant t idal currents in these places (North of Figueira da Foz). (C) 2000 Elsevier Science B.V. All rights reserved.