Two New Methods for the Extraction of Significant Wave Heights From Received HF-Radar Time Series

For close to half a century, the usual procedure to determine ocean surface information from HF-radar data has been to first form the Doppler spectrum from the received time series, and then process the result to extract important wave parameters, such as significant wave height, primary wave period, principal wave direction, or even the full directional ocean wave spectrum. In the current work, we bypass the calculation of the Doppler spectrum and still calculate the significant wave height (H
_s
) from the received radar data using two related proposed methods. The first calculates H
_s
from the variances of the short-time Fourier transform coefficients of the first-order received field. The second uses the estimated variance of the received electrical field signal to determine H
_s
. Both methods require an initial external calibration stage, which can be either performed analytically from the data or by deploying a wave buoy. The validity of the proposed methods is tested with field data from which a significant correlation with the values of H
_s
measured independently by a wave buoy is obtained.