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Abstract
To expand the scope of ocean wave observations, a shipboard coherent S-band wave radar system was developed recently. The radar directly measures the wave orbital velocity from the Doppler shift of the received radar signal. The sources of this Doppler shift are analyzed. After removing the Doppler shifts caused by the ocean current and platform, the radial velocities of water particles of the surface gravity waves are retrieved. Subsequently, the wavenumber spectrum can be obtained based on linear wave theory. Later, the significant wave height and wave periods (including mean wave period and peak wave period) can be calculated from the wavenumber spectrum. This radar provides a calibration-free way to measure wave parameters and is a novel underway coherent microwave wave radar. From 9 September to 11 September, 2018, an experiment involving radar-derived and buoy-measured wave measurements was conducted in the South China Sea. The Doppler spectra obtained when the ship was in the state of navigation or mooring indicated that the quality of the radar echo was fairly good. The significant wave heights and wave periods measured using the radar are compared with those obtained from the wave buoy. The correlation coefficients of wave heights and mean wave periods between these two instruments both exceed 0.9 while the root mean square differences are respectively less than 0.15 m and 0.25 s, regardless of the state of motion of the ship. These results indicate that this radar has the capability to accurately measure ocean wave heights and wave periods.
Highlights
Understanding waves and their characteristics is crucial for marine research and oceanographic development
Typical coherent radar systems include the SM-050 MK III from the Norwegian MIROS and the shore-based S-band Doppler wave radar developed by the Radio Ocean Remote Sensing (RORSE) Laboratory at Wuhan University, China [9,10]
In order to accurately estimate the center frequency of the Doppler spectrum, a high-signal-to-noise ratio (SNR) rRaRedmeamortoeteeSceShnesno.s2.i02s10a91,9f1,u11n1FdOFOaRmRPPEeEEnERtRaRlREpEVrVIeEIrEWeWquisite for the signal processing of the shipboard coherent radar. 1313 (a(a) )
Summary
Understanding waves and their characteristics is crucial for marine research and oceanographic development. Typical coherent radar systems include the SM-050 MK III from the Norwegian MIROS and the shore-based S-band Doppler wave radar developed by the Radio Ocean Remote Sensing (RORSE) Laboratory at Wuhan University, China [9,10]. RiverRad measurements are calibrated following the procedure outlined by Plant et al [12,13] Another nautical X-band radar, which was developed based on the cooperation between Helmholtz Zentrum Geesthacht (HZG) and the Electrotechnical University of St. Petersburg in Russia, showed its ability to monitor ocean wave field [14]. In 2011, a data fusion algorithm was proposed by Stredulinsky and Thornhill [18] This method improved the accuracy of the wave parameter acquisition by modifying the empirical transfer function (ETF) based on the signal-to-noise ratio (SNR) of radar echo. WiwshhtheerereerCaCt0io0isoitfshtethhieentsirnuintrrfsiainccsepicthepanshseaiovsneelvtooeclitothyceiotwyf taohtfeetrchdaepecnialslpaitriylyl,aγwry=avw7e4a, vgcemi,s3t/ghse2i[as3ct0ch]e.elearcactieolenrdatuioentodgureavtoityg,raanvdityγ, and is the ratio of the surface tension to the water density, =74cm3 / s2 [30]
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