HF radar measurements of long ocean waves

Abstract

Sea‐echo data from three separate narrow‐beam HF radar experiments on the Pacific Ocean are analyzed here by techniques presented in Lipa and Barrick (1980). Only those wave spectral components whose periods exceeded 10 s were included. Close agreement of radar‐deduced wave field parameters with surface observations confirms the validity of the second‐order theoretical solution for the echo Doppler spectrum, upon which this analysis is based. Depending on the particular experiment, a variety of wave parameters are extracted, including rms wave height, mean wave direction, dominant period, angular spread of the wave field, the nondirectional wave height spectrum, and higher Fourier angular coefficients versus wave frequency. The radar‐deduced wave parameters fall within the combined error bounds estimated for the radar and buoy wave observations; consequently, we contend that the primary source of error for radar data is finite sample size. Typical accuracies for specific parameters resulting from observations averaged over a 2‐hour period are ±5% for wave height, ±0.5 s for wave period, and ±7° for wave direction. Hence the utility of HF radars for long‐wave measurements has been validated.