Surface current patterns in front of the Venice Lagoon

Abstract: Surface patterns of the low-frequency current in a 20×30km region in front of the Venice Lagoon were analysed from a 13-month-long HF radar data set. Surface circulation was related to prevalent wind regimes in the area and to the tidal flow through the lagoon inlet. Three different categories of wind-forcing were defined: bora (NE wind), sirocco (SE wind), and finally the category containing all other wind directions and calms (winds lower than 3m/sec). Mean flow and vorticity spatial distributions were discussed for different wind conditions. The coastal area about 5km wide is characterized by a flow field with maximum vorticity. Outside the coastal boundary layer the interior flow is part of the Adriatic basin-wide cyclonic circulation. Two counter-rotating vortices of the dimension of about 4–5km were evidenced in the average flow field in front of the lagoon inlet (Malamocco inlet) in all situations except for the bora. The vortex-pair is probably associated with the tidal flow through the inlet. The bora wind induces a strong southward coastal jet detached from the coast by about 5km homogenizing the flow and eliminating the dipole. The average coastal flow pattern in calm wind conditions was also analysed as a function of the strong inflow/outflow (currents in the inlet>0.7ms−1) from the lagoon inlet. In both cases the vorticity pattern is similar, with the negative vorticity to the left of the inlet and positive to the right looking seaward. [Copyright &y& Elsevier]