Accuracy of surface current mapping from High-Frequency (HF) ocean radars

An assessment of surface current mapping accuracy for oceanic High-Frequency (HF) radars is provided. Mapping accuracy is evaluated in terms of radar grid geometry, radial data density and radial velocity errors, and the current field. Mapping errors are derived comparing the original analytical flow pattern with the flow pattern reconstructed varying the error sources. In absence of external perturbations, radar grid geometry controls mapping accuracy and, in combination with asymmetric radial data density, biases both direction and magnitude of surface currents. Flow curvature is an additional source of errors in the surface current maps. Errors are negligible in case of pure zonal or meridional flows with no curvature, but become significant in magnitude and direction when current shears are present. Finally, external perturbations on radial data enhance magnitude and directional biases, thus further degrading vector mapping accuracy.