Directional wave spectra by inversion of ERS-1 synthetic aperture radar ocean imagery

1994 ◽  
Vol 32 (2) ◽  
pp. 340-352 ◽  
Author(s):  
G. Engen ◽  
H. Johnsen ◽  
H.E. Krogstad ◽  
S.F. Barstow
Keyword(s):  
Synthetic Aperture Radar ◽  
Synthetic Aperture ◽  
Wave Spectra ◽  
Directional Wave ◽  
Aperture Radar

On the Performance of the MPI Algorithm for the Retrieval of Significant Wave Height From ERS Synthetic Aperture Radar

2003 ◽  
Author(s):  
Nelson Violante-Carvalho ◽  
Ian S. Robinson
Keyword(s):  
Synthetic Aperture Radar ◽  
Wave Height ◽  
Significant Wave Height ◽  
Synthetic Aperture ◽  
Wave Spectra ◽  
Sar Images ◽  
Significant Wave ◽  
Directional Wave ◽  
Better Than ◽  
Aperture Radar

Spaceborne Synthetic Aperture Radar (SAR) is to date the only source of two dimensional directional wave spectra with continuous and global coverage when operated in the so-called SAR Wave Mode (SWM). Since the launch in 1991 of the first European Remote Sensing Satellite ERS-1 and more recently with ENVISAT millions of SWM imagettes containing detailed spectral information are now available in quasi-real time. This huge amount of directional wave data has opened up many exciting possibilities for the improvement of our knowledge of the dynamics of ocean waves. However the retrieval of wave spectra from SAR images is not a trivial exercise due to the nonlinearities involved in the mapping mechanism. The Max-Planck Institut (MPI) scheme was the first ever proposed and most widely used algorithm to retrieve directional wave spectra from SAR images. In this work significant wave height retrieved from SAR images using the MPI scheme are compared against one year of directional buoy measurements obtained in deep water and against WAM spectra. Our results show that for periods shorter than 12 seconds the WAM model performs better than the MPI method, even considering the fact that the model is used as first guess to the MPI scheme. However, for periods longer than 12 seconds (the part of the spectrum directly observed by SAR) the MPI method performs better than WAM. This is in contrast with the results obtained by Voorrips et al. (2001), who found that the performance of the WAM model is superior even when only the low wavenumber part of the spectrum is considered.

Remote sensing of ocean wave spectra by interferometric synthetic aperture radar

Nature ◽  
1990 ◽  
Vol 345 (6278) ◽  
pp. 793-795 ◽  
Author(s):  
M. Marom ◽  
R. M. Goldstein ◽  
E. B. Thornton ◽  
L. Shemer
Keyword(s):  
Remote Sensing ◽  
Synthetic Aperture Radar ◽  
Ocean Wave ◽  
Synthetic Aperture ◽  
Interferometric Synthetic Aperture Radar ◽  
Wave Spectra ◽  
Aperture Radar

scholarly journals On the retrieval of significant wave heights from spaceborne Synthetic Aperture Radar (ERS-SAR) using the Max-Planck Institut (MPI) algorithm

2005 ◽  
Vol 77 (4) ◽  
pp. 745-755 ◽  
Author(s):  
Nelson Violante-Carvalho
Keyword(s):  
Data Assimilation ◽  
Synthetic Aperture Radar ◽  
Synthetic Aperture ◽  
Wave Spectra ◽  
Max Planck ◽  
Sar Images ◽  
Significant Wave ◽  
Wave Heights ◽  
Significant Wave Heights ◽  
Directional Wave

Synthetic Aperture Radar (SAR) onboard satellites is the only source of directional wave spectra with continuous and global coverage. Millions of SAR Wave Mode (SWM) imagettes have been acquired since the launch in the early 1990's of the first European Remote Sensing Satellite ERS-1 and its successors ERS-2 and ENVISAT, which has opened up many possibilities specially for wave data assimilation purposes. The main aim of data assimilation is to improve the forecasting introducing available observations into the modeling procedures in order to minimize the differences between model estimates and measurements. However there are limitations in the retrieval of the directional spectrum from SAR images due to nonlinearities in the mapping mechanism. The Max-Planck Institut (MPI) scheme, the first proposed and most widely used algorithm to retrieve directional wave spectra from SAR images, is employed to compare significant wave heights retrieved from ERS-1 SAR against buoy measurements and against the WAM wave model. It is shown that for periods shorter than 12 seconds the WAM model performs better than the MPI, despite the fact that the model is used as first guess to the MPI method, that is the retrieval is deteriorating the first guess. For periods longer than 12 seconds, the part of the spectrum that is directly measured by SAR, the performance of the MPI scheme is at least as good as the WAM model.

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