Characterization of storm events along the Gulf of Cadiz (eastern central Atlantic Ocean)

Abstract

The present work deals with the characterization and classification of storm events affecting Cadiz Gulf, i.e. the coast including Southern Portugal, SW Spain and Northern Morocco. The general morphology of the gulf and its location determine the exposition and trajectory of storms affecting the zone, producing significant energy gradients alongshore. This study focuses on the frequency and distribution of the different types of storms, in order to estimate their probability of occurrence. Storm classification was obtained by using wave data records from the HIPOCAS (Hindcast of dynamic Processes of the Ocean and Coastal Areas of Europe) network. The Storm Power Index was used to classify coastal storms. The investigated data sets covered 44 years, between 1958 and 2001. A significant gradient in energy (Storm Power and storm class frequency), approaching direction and storm duration was observed along the gulf, from the most exposed points (Cape San Vicente–Portimao) to the inner, more sheltered ones (Faro–Huelva–Cadiz) and to the southern moderately exposed ones (Bolonia–Tangier). The monthly distribution of number of storms, duration and sum of Storm Power were compared by means of multiple and independent regression analysis with values of different climatic and meteorological indexes. Multiple linear regression analysis between storminess indices and the teleconnection patterns points out that 45% of the change in monthly storminess indices calculated along the Cadiz Gulf are related to changes in the teleconnection patterns, especially North Atlantic Oscillation (NAO), Arctic Oscillation (AO) and East Atlantic (EA). Negative NAO and AO phases and positive EA phases correlate with storminess in the zone. Furthermore, when neutral to strong negative NAO–AO and positive EA phases occurred at the same time and/or when an abrupt change of theses indices occurred, then a greater number of storms with longer duration and higher Storm Power Index were recorded.