The focus of the work is the validation of HF radar observations using comparisons with in situ measurements. Data is provided from twenty-two surface drifters deployed in four batches over a period of one year, and near-surface current profiles acquired by a vessel-mounted Acoustic Doppler Current Profiler station (ADCP) at six selected locations. The analysis comprises radar site-to-site baseline analyses, providing quantitative assessments on the accuracy of the HF radar total velocity fields. External radio-frequency interferences lead to significant gaps in the HFR coverage, which were minimised by an interpolation technique applied to the surface current fields. The validation of HFR velocities was first performed for each individual station in the network, using data generated with both the ideal and the measured antenna patterns. The validation was then repeated with pairs of HFR stations using the site-to-site baseline error analysis. The analysis confirms that the baseline error estimations and the full validation metrics for this HFR frequency band are consistent, and in some aspects superior, when compared to results from similar studies in other regions.

This work was partially funded by the CALYPSO series of Italia-Malta Interreg V-A projects comprising a consortium of Maltese and Sicilian partners led by the Physical Oceanography Research Group of the Dept. of Geosciences at the University of Malta.