Sea-surface currents measured by coastal HF radar off-shore Ancona

The CODAR (Coastal Ocean Dynamics Application Radar) system, was installed for the first time in the Adriatic Sea off the Ancona coast (Italy). The system operated continuously, from September 1997 through February 2000. Some results of the data analysis on a monthly time-scale for one whole year (September 1997-August 1998) are shown. They corroborate a presence of a 10-15 km wide coastal flow, known as WAC (Western Adriatic Current), prevalently flowing towards the south-east. Its variability on a seasonal time scale is clearly evident. A possible influence on the WAC of the freshwater discharge from the Po River (acting through a horizontal pressure gradient) and its spreading in the Northern Adriatic basin is documented. A freshwater discharge confined to the western coast is associated to a stronger horizontal pressure gradient which then reinforces the WAC. On the contrary, fresh water dissipated in the surface layer towards the eastern coast and trapped in the northernmost sub-basin of the Adriatic, as may occur during summer, is associated to the much weaker WAC. Some hints of a synoptic time scale variability in the current field are reported, putting into evidence a reversal of the prevalent south-eastward current observed in some meteorological situations characterized by a SE (sirocco) wind.