Elimination of the impact of vessels on ocean wave height inversion with X-band wave monitoring radar

Directional wave spectra and integrated wave parameters can be derived from X-band radar sea surface images. A vessel on the sea surface has a significant influence on wave parameter inversions that can be seen as intensive backscatter speckles in X-band wave monitoring radar sea surface images. A novel algorithm to eliminate the interference of vessels in ocean wave height inversions from X-band wave monitoring radar is proposed. This algorithm is based on the characteristics of the interference. The principal components (PCs) of a sea surface image sequence are extracted using empirical orthogonal function (EOF) analysis. The standard deviation of the PCs is then used to identify vessel interference within the image sequence. To mitigate the interference, a suppression method based on a frequency domain geometric model is applied. The algorithm framework has been applied to OSMAR-X, a wave monitoring system developed by Wuhan University, based on nautical X-band radar. Several sea surface images captured on vessels by OSMAR-X are processed using the method proposed in this paper. Inversion schemes are validated by comparisons with data from in situ wave buoys. The root-mean-square error between the significant wave heights (SWH) retrieved from original interference radar images and those measured by the buoy is reduced by 0.25 m. The determinations of surface gravity wave parameters, in particular SWH, confirm the applicability of the proposed method.