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32 st / March 2015 www.sea-technology.com which covers an approximately 70-kilometer range offshore, with a 1.6-kilometer radial and 5ยบ angular resolution. The HF radar system was installed at the begin- ning of 2012, and it has been collecting surface ve- locity data continuously since June 2012. Radial velocities are processed from the 15-min- ute-average spectra of the received echoes from the sea surface every 10 minutes. The hourly radial ve- locities are then obtained after applying a centered 75 minutes running mean average. Therefore, each hourly radial velocity is a running mean of 75 min- utes. The radial velocities from each station are trans- ferred to the central combine station where they are converted to total felds, using a least-mean square algorithm with a spatial interpolation radius of 6 ki- lometers into a 3-by-3 kilometer resolution rectan- gular grid. Quality Control Procedures Radial data from each antenna, as well as the com- bined total surface currents, are analyzed through a battery of tests to ensure that the data being produced and available through SOCIB Thredds data server are of the highest quality and follow international stan- dards, as those of MARACOOS or NOAA. Prior to the automated battery of tests implement- ed at SOCIB, the standard quality control procedures in CODAR proprietary software were adapted by es- tablishing velocity threshold values to prevent anom- alous large vectors. In order to avoid bearing estimation errors due to dis- tortions on the pattern of the receiver, pattern calibrations were undertaken for both antennas. The frst order limit settings, which defne the region of the spectra that is processed into radial ve- locities, were carefully adjusted with the aim of preventing interferences and errant high-radial velocities. With the aim of identifying addi- tional sources of errors in the HF radar data, further post-processing quality checks, based on system diagnostics at the radial level and on temporal evolu- tion of total vector velocities, are auto- mated in the data-stream procedures. Hourly radial data fles are associat- ed with system performance diagnostic metrics, some of which can be used as proxies for quality of the radial vector feld. These radial quality metrics se- lected are briefy detailed. Signal-to-Noise Ratio. This ra- tio gives an indication of the signal strength received from the sea echo at each antenna from which radials are computed. If they are too low, radial quality is not reliable. Total Number of Radial Vector So- lutions. Representing the total num- ber of radial vectors found at different bearings and ranges, this parameter is a (Top) (a) Temporal evolution of the signal-to-noise ratio, (b) number of radial vectors and (c) average ra- dial bearing for the Ibiza antenna in 2013. These values are obtained every 10 minutes from CODAR diag- nostic fles, and are analyzed to eval- uate the system performance and to check the nonfunctioning system pe- riods. (Bottom) Difference between HF radial velocity and drifter-derived radial current data at each drifter po- sition for (a) Ibiza station and (b) For- mentera station. With these kinds of maps, it is possible to identify those areas with lower agreement between drifters and HF radar values and pos- sible sources of errors in the HF radar performance.