Interoperability of Direction-Finding and Beam-Forming High-Frequency Radar Systems: An Example from the Australian High-Frequency Ocean Radar Network.

Direction-finding SeaSonde (4.463 MHz; 5.2625 MHz) and phased-array WEllen RAdar WERA (9.33 MHz; 13.5 MHz) High-frequency radar (HFR) systems are routinely operated in Australia for scientific research, operational modeling, coastal monitoring, fisheries, and other applications. Coverage of WERA and SeaSonde HFRs in Western Australia overlap. Comparisons with subsurface currents show that both HFR types agree well with current meter records. Correlation (R), root-mean-squares differences (RMSDs), and mean bias (bias) for hourly-averaged radial currents range between R = (-0.03, 0.78), RMSD = (9.2, 30.3) cm/s, and bias = (-5.2, 5.2) cm/s for WERAs; and R = (0.1, 0.76), RMSD = (17.4, 33.6) cm/s, bias = (0.03, 0.36) cm/s for SeaSonde HFRs. Pointing errors (theta) are in the range theta = (1 degrees, 21 degrees) for SeaSonde HFRs, and theta = (3 degrees, 8 degrees) for WERA HFRs. For WERA HFR current components, comparison metrics are R-U = (-0.12, 0.86), RMSDU = (12.3, 15.7) cm/s, bias(U) = (-5.1, -0.5) cm/s; and, R-V = (0.61, 0.86), RMSDV = (15.4, 21.1) cm/s, and bias(V) = (-0.5, 9.6) cm/s for the zonal (u) and the meridional (v) components. Magnitude and phase angle for the vector correlation are rho = (0.58, 0.86), phi = (-10 degrees, 28 degrees). Good match was found in a direct comparison of SeaSonde and WERA HFR currents in their overlap (rho = (0.19, 0.59), phi = (-4 degrees, +54 degrees)). Comparison metrics at the mooring slightly decrease when SeaSonde HFR radials are combined with WERA HFR: scalar (vector) correlations for R-U,R- V, (rho) are in the range R-U = (-0.20, 0.83), R-V = (0.39, 0.79), rho = (0.47, 0.72). When directly compared over the same grid, however, vectors from WERA HFR radials and vectors from merged SeaSonde-WERA show R-U (R-V) exceeding 0.9 (0.7) within the HFR grid. Despite the intrinsic differences between the two types of radars used here, findings show that different HFR genres can be successfully merged, thus increasing current mapping capability of the existing HFR networks, and minimising operational downtime, however at a likely cost of slightly decreased data quality.