INTRODUCTION

This work is a multidisciplinary research carried out by several CNR Institutes (ISMAR, ISSIA, ISAC, IBF) and ENEA and it is supported by the European projects MFSTEP and MERSEA.

The project aims to study the influence of the atmospheric variability on the mesoscale oceanic structures and on the response of the surface stratification with respect to the atmospheric forcing by means of measurements acquired from fixed and moving platforms. The Ligurian Sea is a very suitable working area for this type of research. The main hydrodynamic feature of this basin [Astraldi and Gasperini (1992),Vignudelli et al.(1999)] consists in a well defined cyclonic circulation that is affected by a strong variability at different time and space scales depending on the air-sea interaction. Thus, it is necessary to analyse if this variability may be ascribed only to the atmospheric forcing or also to possible horizontal advection phenomena. On the other side, the sea surface affects the overhanging atmosphere, especially for what relates the principal thermodynamical mechanism of the hydrological cycle. The joint use of a fixed and a moving platform allows the investigation of the interaction processes at all the different time scales in the basin. The fixed platform is the ODAS Italia 1 meteo-oceanographic buoy [Bozzano (2003)] located at the centre of the Ligurian Sea (Fig.1).

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Figure 1: ISSIA-CNR's ODAS-Italia 1 Buoy.

This buoy collects the main surface meteo-marine parameters involved in the energy exchanges. An instrumental mooring placed nearby the buoy fulfils the data set by furnishing hydrological and current meter measurements at the deeper levels. The use of the R/V Urania during the winter season was requested for the in-situ data acquisition and for the servicing of the ODAS buoy and of current meter moorings in the area. The cruise would complement the one carried out on summer 2004 (MFSTEP1), when the air-sea fluxes were measured in the same area by shipborne and balloon radiosounding measurement systems, other than by several hydrological casts. In addition to the above tasks, measurements of sea radiance for satellite "sea-truth" and of the optical properties of the upper watercolumn were perfomed.

It is known that NW Mediterranean Sea and particularly the Ligurian Sea are sites of primary interest for the study and observations of Cetaceans (whales and dolphins). The area is populated by many species of marine mammals, probably due to the peculiar topography and hydrology that favour the growth of consistent prey populations and communities for cetacean predation. The use of ship-of-opportunity [Evans et al.(2004)],[Brereton and Williams (2000)] is both cost-saving and efficient, mainly for first estimates of distribution and abundance. After the MFSTEP1 Cruise of 2004, R/V Urania was employed also in this cruise for Cetacean Observations. Moreover, as a ship-of-opportunity, the transit times were used for swath bathymetry mapping.

The activities and initial results of the research cruise MFSTEP2 in the Ligurian Sea aboard CNR's R/V Urania are presented.

During 10 days in the area

• air-sea fluxes and thermal structure were investigated by continuously recording instrumentation,
• the water physical and optical properties were studied by CTD casts and profilers (water samples were filtered and stored for other physical and biological investigations), and by ADCP current meter profiling,
• the ODAS buoy and other moorings were serviced,
• and, on transit and when time was made available by scheduled operations, multibeam swath bathymetry and SBP was performed.

Cruise started in Civitavecchia 2005-04-13. Ship left the work area on 2005-04-22 morning, heading to Livorno, where it docked 2005-04-22 09:00 local time.

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Figure 2: Geographical area setting, Ligurian Sea. Bathymetry from GEBCO.