Abstract
Synthetic aperture radar (SAR) is an important method for observing ocean waves, and inversion of the ocean wave spectrum is an important part of SAR ocean wave detection. For most wave spectrum inversion methods, the first guess spectrum is crucial to the accuracy of SAR wave spectrum inversion. The first guess spectrum can be provided by some existing fixed wave spectrum models, but the applicability of these wave spectrum models as the first guess spectrum has not been systematically studied. This paper focused on the applicability of the Elfouhaily spectrum (E spectrum) as a full wavenumber spectrum and the Pierson-Moscowitz spectrum (PM spectrum) as a wind wave spectrum as the first guess spectrum for inverting the wave spectrum. Based on the SENTINEL-1A and RADARSAT-2 SAR satellite data of the Maritime Silk Road, using the E spectrum and PM spectrum as the first guess spectrum by the Max Planck Institute (MPI) method, the ability of the E spectrum and PM spectrum as the first guess spectrum to retrieve the wave spectrum and wave parameters was systematically evaluated. The significant wave height (HS) and zero-crossing period (TZ) wave parameters obtained from SAR inversion were compared with the European Center for Medium-Range Weather Forecasts (ECMWF) wave data. By the comparison results, we analyzed the best wind speed and significant wave height ranges for the inversion of the PM spectrum and E spectrum as the first guess spectrum. The results showed that the E spectrum as the first guess spectrum had a good effect on the inversion at medium sea situation. It was suitable as the first guess spectrum of the SAR wave spectrum inversion.
Highlights
Ocean waves are an important marine dynamic process
Based on the SENTINEL-1A and RADARSAT-2 Synthetic aperture radar (SAR) satellite data, this paper systematically evaluated the ability of the E spectrum and PM spectrum as the first guess spectrum to retrieve the wave spectrum by Max Planck Institute (MPI) method
The significant wave height and zero-crossing period wave parameters obtained from SAR inversion were compared with European Center for Medium-Range Weather Forecasts (ECMWF) wave data, and the applicability of the PM spectrum and E spectrum as the first guess spectrum to invert the wave spectrum and wave parameters was analyzed
Summary
Ocean waves are an important marine dynamic process. They are small-scale wind-generated gravity waves that occur on the ocean surface, including wind waves and swells. This paper mainly used the ECMWF ERA-Interim dataset, 10 m wind speed, 10 m wind direction, significant wave height and mean zero-crossing period corresponding to the SAR data observation area and time, with a resolution of 0.125◦. The wind speed and direction provided by ECMWF were used as inputs to construct the first guess spectrum, and the significant wave height and zero-crossing period data were used to verify the accuracy of the wave parameters obtained from the inversion. Minimizing the value function means that the wave spectrum obtained from the inversion is closest to the first guess spectrum, and the simulated SAR image spectrum is closest to the observed SAR image spectrum. From 1955-1960, Moscowitz researched observational data obtained from the North Atlantic Ocean, compared and analyzed 54 fully developed wind and wave spectra, and divided them into 5 groups based on wind speed. The E spectrum is a full wavenumber spectrum and a non-empirical ocean spectrum
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