Comparing wavelengths simulated by the coastal wave model CWAM and TerraSAR-X satellite data

Claus Gebhardt,Andrey Pleskachevsky,Wolfgang Rosenthal,Susanne Lehner,Peter Hoffmann,Jens Kieser,Thomas Bruns

doi:10.1016/j.ocemod.2015.10.003

Claus Gebhardt, Andrey Pleskachevsky + Show 5 more

Open Access

https://doi.org/10.1016/j.ocemod.2015.10.003

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Abstract

The accuracy of the high resolution coastal wave forecast model CWAM is validated on the basis of sea state information from satellite images of TerraSAR-X (TS-X). At the same time, the performance of the satellite retrieval of sea state parameters is demonstrated. Employing 2-dimensional spatial Fourier Transformation, image spectra are derived from TS-X and locally varying patterns of the peak wavelength are provided using state-of-the-art satellite retrieval. Subsequently, wavelength comparisons are performed between a typical set of TS-X scenes acquired in December 2013 over the German Bight and the model hindcasts. The results are mostly in reasonable agreement. Potential shortcomings of the wave model are discussed as well.

Highlights

Monitoring the sea state from space, including spectral quantities like the wavelength and travel direction, has started in 1978 with the synthetic aperture radar (SAR) on SeaSat (Beal et al, 1983)
The satellite data were useful for deep water areas
The results are presented together with their statistical properties such as the bias, root-mean-square difference (RMSE), scatter index (SI), and correlation. These are calculated from the pairs of all TS-X data for a certain image and their nearest model data points

Summary

Introduction

Monitoring the sea state from space, including spectral quantities like the wavelength and travel direction, has started in 1978 with the synthetic aperture radar (SAR) on SeaSat (Beal et al, 1983). Improvements were achieved with the ESA satellites ERS-1, ERS-2, and ENVISAT, operating in C-band (Li et al, 2008; 2011, and references therein). A recent historical overview on the SAR wave-mode being operated on these three satellites, and the use of the wavemode data at ECMWF to improve numerical wave predictions, is given in (Hasselmann et al, 2012). The resolution of the SAR wavemode of ENVISAT and the ERS-satellites was sufficient for measuring long waves (about 100 m and longer) and for the comparison to buoys for respective frequencies (0.12 Hz and shorter). The satellite data were useful for deep water areas (the dispersion relation for deep water waves was important for the comparison of wave number and frequency spectra). Beside Radarsat, operating in C-band since 2007, data are provided as well from high resolution

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