future work.2. High frequency (HF)

future work.
2. High frequency (HF) radar observations HF radars operate in the 3–30 MHz frequency range of the electromagnetic spectrum and are able to obtain information
about the ocean at ranges up to 150 km. The change in frequency between the transmitted and the backscattered signal due to the Doppler effect allows the determination of surface currents, wind direction and the oceanwave spectrum over a large area of the ocean surface (Barrick,1972). Therefore, the large coverage obtained by the radar is a major advantage over in-situ wavemeasurement tools, for examplewave buoys, where the spatial coverage is limited to a single point. The radar information is contained within the Doppler spectrum (Fig. 1), which is characterised by two large peaks known as the first order Bragg peaks that correspond to ocean waves of half the radar wavelength moving directly towards and away from the radar. The Bragg peaks are used to measure radial surface currents and wind direction.