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14 páginas, 8 figuras, 3 tablas, [EN] A systematic Data Quality Checking Protocol for Vessel Mounted Acoustic Doppler Current Profiler observations is proposed. Previous-to-acquisition conditions are considered along with simultaneous ones. Independently of internal systems, location and misalignment, the auxiliary systems to acquisition determine the accuracy range of the current velocity profiles. Simultaneous-to-acquisition navigation conditions provide the physically descriptive weight (or reliability) of significance for each individual current profile. The formulation of the Data Quality Checking Protocol is followed by actual applications and examples from cruises aboard R/V "García del Cid" in the Western Mediterranean Sea, [ES] Se propone un protocolo sistemático para el control de calidad de los datos obtenidos con un perfilador acústico por efecto Doppler (ADCP) instalado en un buque. Se consideran las circunstancias previas a la adquisición y las simultáneas a la misma. Independientemente de las condiciones técnicas, de localización del instrumento y de su posible desalineamiento, los sistemas auxiliares a la adquisición determinan el rango de precisión de los perfiles de velocidad de la corriente. Las circunstancias de navegación simultáneas a la adquisición permiten determinar y atribuir un grado de significación (o fiabilidad) a cada uno de los perfiles individuales. La formulación del protocolo de control de calidad de los datos se complementa con su aplicación a una campaña realizada en otoño de 1992 a bordo del buque oceanográfico “García del Cid” en el Mediterráneo occidental, FE92 cruise was funded by the Spanish Interministerial Commission for Science and Technology CICYT (MAR89-0550) and Mphmed93 by the Commission of European Communities, Directorate General for Fisheries (DG XIV, MA 3730). This paper is a contribution to the European Union Marine Science and Technology (MAST) programme OMEGA project (contract MAS3-CT95-0001). E.G.-G. research was financially supported by a Generalitat de Catalunya Doctoral Grant “Formació de Personal Investigador”. The manuscript was finished during the postdoctoral appointment of E.G.-G. in JPL/Caltech with financial assistance of the Ministerio de Educación y Cultura (Spain) within “Plan de Formación de Doctores y Tecnólogos en el Extranjero”

The Liguro-Provenco-Catalan or Northern Current, which contours the continental slope of the north-western Mediterranean Sea, has been described as a permanent flow affected by important variability at different scales. Many observations indicate a higher flux in winter than in summer, while the occurrence of mesoscale events appears to be a common characteristic. The opportunity of examining several years of current meter data at a location close to the inner border of the Northern Current has definitively demonstrated the existence of a seasonality in the mesoscale variability. Although the records do not concern the core of this current, the consistency of the several characteristics we have determined with results found by other authors in the Ligurian Sea allows us to consider them as representative of its general trends. Three current meters moored at 15, 50 and 100 m depth from an oil drilling ring near the shelf break off the Ebro delta, with a considerable coverage from mid-1987 to mid-1992, provide a clear image of the current behaviour. The general flow is along-slope and presents occasional disruptions for periods of several days, described here as mesoscale events. Most of the motion we have recorded displays a marked barotropic character. The intensity of the current is relatively low, increasing suddenly in autumn at the three levels monitored, in a manner that appears not to be connected to the local wind regime. One of the most relevant pieces of information contained in the whole current data set concerns the repeated presence of clockwise rotations in a near-inertial frequency, even at 100 m. The principal objective of the present study was to investigate any seasonal signal in the appearance and characteristics of the mesoscale motion. The main observed feature in a low-passed time series below the thermocline, namely a rapid and strong autumn increase in mesoscale activity, is shown to be consistently present, with very small inter-annual temporal variability. This maximum of mesoscale activity is followed by a rapid decrease in winter and then by a continuous decline until the end of the summer. A complete characterization of the mesoscale motion in the Northern Current, including its origin and interaction with the main flow, requires extensive experimental and numerical work. Our results have demonstrated that this motion displays a clear seasonal cycle and provided evidence that the recorded mesoscale activity is linked far more to the shelf/slope front evolution than to local wind variability.