Wave Height Extraction From the First-Order Bragg Peaks in High-Frequency Radars

The conventional second-order Bragg-spectrum-based wave height extraction method is often susceptible to external noise and spatial aliasing. To improve the wave height estimate, we turn to the first-order Bragg peaks and propose a new method which directly estimates the wave height from them. The key point is to confirm and use the unsaturated property of the first-order Bragg spectral power. The quantitative relation between the first-order Bragg peak power and the significant wave height can be established with the help of an in situ wave buoy, and consequently, the wave height is to be read out from the curve via the maximum Bragg peak power on one range cell. The first-order method is validated by a two-month-long data set collected by the OSMAR-S radar at 13 MHz. Compared with the second-order method, the improvement is obvious under low and moderate sea states. The new method opens the way for wider use of the first-order Bragg peaks in wave height extraction by high-frequency radars.