On the homogeneity of the wave field in coastal areas as determined from ERS-2 and RADARSAT synthetic aperture radar images of the ocean surface

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.