Abstract
A HF ocean radar is useful to observe sea states near coast. Okinawa Radio Observatory, Communications Research Laboratory has developed the radar in 1988, firstly in Japan. This article describes principles to deduce ocean current, sea surface wind direction and wave height from Doppler spectra detected by HF radar, and shows examples of them. Ocean current is calculated by Doppler shift of first order echo from Bragg frequency, and sea surface wind direction is obtained by the ratio of two first order echo intensities. But it is necessary to use second order echo for calculation of wave height. Comparison between sea states deduced by the radar and those by in-situ measurements shows good agreement.
