Retrieval of ocean surface wave fields using marine radar-image sequences

This paper describes and validates an empirical method for inversion of marine radar-image sequences to time series of ocean surface wave fields without calibration. External sensors are not required. The radar system can measure as a stand-alone device. The method has been developed within the framework of the European project "MaxWave" and is based on a local description of the RCS in space and time, whereby the ocean surface is subdivided into local facets. A local transfer function between local RCS and ocean surface is determined for each facet. The inversion scheme is applied to radar-image sequences acquired by a marine X-band radar, operating at grazing incidence and horizontal polarization in transmit and receive. The system is mounted aboard an offshore platform in the North Sea. The ocean-surface image sequences are validated by comparison of the calculated significant wave heights with values from co-located wave records of three in-situ sensors. It is shown that the accuracy of the radar-retrieved significant wave height is within the accuracy of the in-situ sensors