Ocean wave spectrum and surface currents can be de- termined from a series of spatial wave images recorded by an X-band marine radar. In the absence of a surface current, the three-dimensional spectral energy found by using the series of images will be confined to a trajectory defined by the still water dispersion relationship. The presence of a surface current will make the three-dimensional spectral energy show a corresponding Doppler shift which may determine the current using the least squares method and obtain the directional wave spectrum. On the basis of conventional wave spectrum and directional function, the paper emulates a series of X-band radar images considering shadowing modulation and simulates numerically the three- dimensional image spectrum both with and without a surface cur- rent, calculates the current velocity by virtue of the Doppler shift, and obtains the two-dimensional image spectrum. Finally the pa- per analyzes measured wave level elevation—a function of time t to obtain one-dimensional image spectrum, and the data comes from an X-band radar in McMaster University.
WU Xiongbin WU Yanqin CHENG Feng OUYANG Wenjie KE Hengyu
OSMAR071 is the latest product of the OSMAR (ocean state monitor and analysis radar) series of high frequency surface wave radar (HFSWR), which was developed by the Radiowave Propagation Laboratory of Wuhan University. It adopts a modified Barrick waveheight inversion model. The modifications are introduced to improve the model's performances under the effect of noises and interferences and in the case of broad beam radar detection. The two unknown coefficients in the modified model are figured out by fitting the HFSWR significant waveheight results to those output from a wave buoy located in the radiating coverage of the radar site. The model is applied to inverse the waveheights from radar data for the duration from Dec. 1st, 2008 to Feb. 25th, 2009, and then the radar waveheights are compared with the buoy measurements. Results show that the rms difference between radar-derived significant waveheights and those from the buoy is 0.38 m and the correlation coefficient between the two series is 0.66. This study describes OSMAR071 observation of significant waveheight with relatively satisfactory accuracy during about three months.
