Comparison between HF radar current data and moored ADCP currentmeter

A preliminary assessment of accuracy of a two-sites shore-basedHF Radar network along the Venice Lagoon littoral was attempted by means ofcomparison with a 57.5 day-long ADCP current time series for the period September-October 2002. Results showed that radar measurements were accurate (< 7 cm/s)in more than 50% of the times, since more than 50% of the differences betweenboth E-W (U)and N-S (V )comp onents were under 7 cm/s, and more than 50% ofdirection differences were under 35◦. The main differences between the HF radar and surface ADCP currents can be explained in terms of random errors affecting themeasurement technique and the daily sea breeze forcing, since low-pass filtering ofcurrent time series significantly improved the correlation and decreased the RMS of the differences between the two measured data set. Comparison of the semidiurnal (M2, S2)tidal band suggested good agreement between tidal ellipse amplitudes.Wind forcing on a daily time-scale (sea-breeze)was associated with larger differences between radar and ADCP currents at a diurnal band due to the presence of a vertical shear in the surface layer.