Modelling the main features of the Algarve coastal circulation during July 2004: A downscaling approach

This article presents a methodology for simulating the Algarve coastal circulation using realistic forcing (e.g. low-frequency circulation, tide, high-resolution atmospheric forcing). Low-frequency open boundary conditions are defined via a downscaling of the HYCOM-US operational solution for the Gulf of Cadiz. Atmospheric forcing is imposed using the MM5 high-resolution mesoscale model (9 km resolution near the coast). A 3-level nesting system based on the MOHID numerical system is implemented. The higher nesting level has a horizontal resolution of 0.02° along the Algarve coast. The methodology is first validated qualitatively. A comparison between the numerical results and the conceptual model of the circulation described in the literature is presented. A quantitative validation is also performed, based mainly on remote sensing data (sea surface temperature and altimetry) available for July 2004. The numerical system is able to reproduce many of the circulation features described in the literature (e.g. Azores current recirculation in the Gulf of Cadiz, the upwelling jet, Mediterranean Water undercurrent, Mediterranean Outflow splitting, generation of meddies) and observed with remote-sensing data (e.g. the signature in sea surface temperature (SST) during a regime of upwelling relaxation).