Retrieval of surface wave parameters from sar images and their validation in the coastal seas around Japan

We have developed a scheme to retrieve surface wave parameters (wave height and wave propagation direction) from European Remote-Sensing Satellite (ERS) Synthetic Aperture Radar (SAR) image mode data in coastal seas around Japanese coastlines. SAR spectra are converted to surface wave spectra of swell-dominated or wind-wave dominated cases. The SAR spectrum and SAR-derived wind speed are used to derive the surface wave spectrum. The wind-wave dominated case and swell-dominated case are differentiated by a wind speed of 6 m/s, and processed in different ways because of their different degree of nonlinearity. It is indicated that the cutoff wavelength for retrieval of the wind-wave dominated spectrum is proportional to the root of significant wave height, which is consistent with the results of previous studies. We generated 66 match-ups using the SAR sub-images and the in-situ surface wave parameters, which were measured by wave gauges installed in near-shore seas. Among them, there are 57 swell-dominated cases, and 9 wind-wave dominated cases. The significant wave heights derived from SAR and from in-situ observation agree with the bias of 0.09 m, the standard deviation of 0.61 m and the correlation coefficient of 0.78. The averaged absolute deviation of wave propagation directions is 18.4°, and the trend of the agreement does not depend on the wave height. These results demonstrate that the SAR surface wave spectrum retrieved by the present system can be used to observe the surface wave field in the coastal seas around Japan.

[1]  T. Barnett,et al.  Measurements of wind-wave growth and swell decay during the Joint North Sea Wave Project (JONSWAP) , 1973 .

[2]  J. Wright,et al.  Detection of ocean waves by microwave radar; The modulation of short gravity-capillary waves , 1978 .

[3]  J. Ewing,et al.  Directional Wave Spectra Observed during JONSWAP 1973 , 1980 .

[4]  D. Ross,et al.  On the detectability of ocean surface waves by real and synthetic aperture radar , 1981 .

[5]  K. Hasselmann,et al.  Spectral signal to clutter and thermal noise properties of ocean wave imaging synthetic aperture radars , 1982 .

[6]  Werner Alpers,et al.  Monte Carlo simulations for studying the relationship between ocean wave and synthetic aperture radar image spectra , 1983 .

[7]  R. Raney,et al.  Theory of synthetic aperture radar ocean imaging: A MARSEN view , 1985 .

[8]  M. Donelan,et al.  Directional spectra of wind-generated ocean waves , 1985, Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences.

[9]  Werner Alpers,et al.  Measurement of the ocean wave-radar modulation transfer function at 35 GHz from a sea-based platform in the North Sea , 1986 .

[10]  David Lyzenga,et al.  Numerical Simulation of Synthetic Aperture Radar Image Spectra for Ocean Waves , 1986, IEEE Transactions on Geoscience and Remote Sensing.

[11]  K. Hasselmann,et al.  On the nonlinear mapping of an ocean wave spectrum into a synthetic aperture radar image spectrum and its inversion , 1991 .

[12]  Paris W. Vachon,et al.  Airborne and spaceborne synthetic aperture radar observations of ocean waves , 1994 .

[13]  Steve Elgar,et al.  Reflection of Ocean Surface Gravity Waves from a Natural Beach , 1994 .

[14]  P. W. Vachon,et al.  Generalizations of the non‐linear ocean‐SAR transform and a simplified SAR inversion algorithm , 1994 .

[15]  Werner Alpers,et al.  Estimation of the ocean wave–radar modulation transfer function from synthetic aperture radar imagery , 1994 .

[16]  Harald Johnsen,et al.  SAR-ocean wave inversion using image cross spectra , 1995, IEEE Trans. Geosci. Remote. Sens..

[17]  P. Heimbach,et al.  An improved algorithm for the retrieval of ocean wave spectra from synthetic aperture radar image spectra , 1996 .

[18]  Werner Alpers,et al.  Katabatic wind fields in coastal areas studied by ERS-1 synthetic aperture radar imagery and numerical modeling , 1998 .

[19]  P. Vachon,et al.  Analysis of ERS-1/2 synthetic aperture radar wave mode imagettes , 1998 .

[20]  F. Monaldo,et al.  Comparison of SIR‐C SAR wavenumber spectra with WAM model predictions , 1998 .

[21]  Masanobu Shimada,et al.  Verification processor for SAR calibration and interferometry , 1999 .

[22]  Feifei Pan,et al.  Gap Winds and Wakes: SAR Observations and Numerical Simulations , 1999 .

[23]  C. Mastenbroek,et al.  A semiparametric algorithm to retrieve ocean wave spectra from synthetic aperture radar , 2000 .

[24]  A. C. Voorrips,et al.  Validation of two algorithms to retrieve ocean wave spectra from ERS synthetic aperture radar , 2001 .

[25]  Ola M. Johannessen,et al.  SAR-retrieved wind in polar regions-comparison with in situ data and atmospheric model output , 2002, IEEE Trans. Geosci. Remote. Sens..

[26]  Johannes Schulz-Stellenfleth,et al.  Spaceborne synthetic aperture radar observations of ocean waves traveling into sea ice , 2002 .

[27]  Masanobu Shimada,et al.  An L-band geophysical model function for SAR wind retrieval using JERS-1 SAR , 2003, IEEE Trans. Geosci. Remote. Sens..

[28]  Masanobu Shimada,et al.  Evaluation of JERS-1 SAR images from a coastal wind retrieval point of view , 2004, IEEE Transactions on Geoscience and Remote Sensing.

[29]  S. Lehner,et al.  A parametric scheme for the retrieval of two-dimensional ocean wave spectra from synthetic aperture radar look cross spectra , 2005 .

[30]  H. Kawamura,et al.  Influence of orographically steered winds on Mutsu Bay surface currents , 2005 .

[31]  H. Kawamura,et al.  Statistical compartmentalization of surface wind field over coastal seas using high‐resolution SAR‐derived winds , 2005 .

[32]  B. Chapron,et al.  Extraction of coastal ocean wave fields from SAR images , 2005, IEEE Journal of Oceanic Engineering.