The XIOM: 20 years of a regional coastal observatory in the Spanish Catalan coast

Abstract

The importance of coasts and the need for improving knowledge of their environment through the observation and modelling of processes is evident from human activities and ecosystems that they support. This paper presents the coastal observatory in the Spanish Catalan coast and its contribution to a better understanding of processes that take place in this area. The XIOM network for oceanographic and coastal meteorological measurements (Xarxa d'Instrumentació Oceanogràfica I Meteorològica) is owned by the Catalan regional government. XIOM buoys collect wave height data at local receiving stations, which is then validated statistically, and the subsequent results are displayed on the website. Water level recordings are based on pressure measurements and atmospheric variables recorded with typical meteorological stations. At present, there is not a continuous measurement of currents or temperatures in the Catalan shelf-slope region, but several moorings have been deployed in the area. The coastal wind field is highly heterogeneous with main components from E, NW and S. This will have some implication for the coastal wind waves. Even with the relatively short fetch in the NW Mediterranean, the Catalan coast can be impacted by damaging waves during storms. At the Ebro delta the complex winds develop bimodal spectral wave features. In the central and north coast typical unimodal spectra are found. The most important variations in sea level in the Catalan coast are due to meteorological conditions and in some areas the resonant effect of bays and harbours. Storm surges may be of the order of 1 m, a magnitude much larger than tidal range. This sea level variation has a very important effect on storm risk and coastal flooding and it is a very important factor when modelling coastal dynamics in extreme events. The continental shelf slope dynamics are dominated by a quasi-permanent slope current. The mean current intensity is not very strong (~ 10 cm/s at 100 m depth) but it presents a seasonal intensification in winter where velocities can reach higher values. Over the shelf, little work has been previously done over long time series. The measurements obtained allowed the identification of the relative influence of winds, Ebro river outflow and open sea dynamics on the shelf dynamics. An oil spill drift forecasting system has also been developed in which measurements will be used for the short forecast of oil transport. The XIOM is still growing and in a short term period meteorological buoys with current meters will be deployed and scalar buoys will be replaced by directional ones. © 2008 Elsevier B.V. All rights reserved.