Abstract
Spatial variations of the wave field in coastal waters were determined from images obtained by synthetic aperture radar (SAR) on board the European satellites ERS-1 and 2. The capabilities of RADARSAT SAR to provide useful information for evaluating the wave field variation in nearshore waters are explored. Besides the different polarization between ERS and RADARSAT SARs, range to velocity ratios, signal to noise ratios and the acquisition swath are important issues to take into consideration in comparing the performance of the radar systems. In situ data from a coastal region in the north-west of Baja California are used to validate some of the remote observations and to provide relevant ground truth. Particular aspects of wave phenomena in finite depth waters such as refraction, diffraction and groupiness are considered. An appropriate method for analysing the radar images is applied to describe wave features as they originate from a non-homogeneous process. Wave field characteristics and their spatial variations as resolved by RADARSAT SAR are relevant variables for applications such as beach erosion and coastal management. Inclusion of specific modules to retrieve this type of information should be considered for operational software packages for the use and application of ocean surface data from SAR images. The differences of the two radar systems did not affect their capabilities to observe the wave field in coastal regions.
Highlights
Use of remote sensing data for ocean wave research has mainly focused on deep water conditions with the aim of improving global forecasts of sea-state and of directional wave spectra
synthetic aperture radar (SAR) are very important characteristics providing us with the ability of look at the wave field near the coast in a rather unique fashion, and to achieve a detailed description the evolution of wave as they approach the coast
Spatial variability of the wave field should be carefully taken into account when wave information retrieved from radar images is compared with the estimates from wave records in the time domain
Summary
Use of remote sensing data for ocean wave research has mainly focused on deep water conditions with the aim of improving global forecasts of sea-state and of directional wave spectra. The environmental and economic importance of sediment transport and erosion on coastal structures is well known. Activities such as navigation, recreation, aquaculture, fishing and others require a good knowledge of the wave field in coastal regions. The purpose of the present document is to demonstrate the capabilities of RADARSAT SAR for retrieving information that is valuable for studying in detail some ocean wave characteristics in the nearshore region. Since an important feature of SAR images is their spatial resolution, it will be shown that certain wave field features with scales of hundreds of metres can be measured. The issue of retrieving wave information and applying it to improve forecast systems in the coastal zone through data assimilation will be addressed
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