Analysis of oceanic long wave refraction at the Gulf Stream boundary using RADARSAT synthetic aperture radar during Hurricane Bonnie

Abstract

In this study, we analyze the Gulf Stream's effect on the refraction of ocean waves observed in data obtained from the RADARSAT synthetic aperture radar (SAR). The ocean waves observed on this SAR image have very long wavelengths and are mainly generated by Hurricane Bonnie which was located to the east of the Gulf Stream when the SAR image was taken. 256 by 256 pixel sub-images are extracted from the SAR image, and the SAR image spectrum is calculated from these sub-images. The SAR image spectrum should represent the directional ocean wave spectrum in this case, because the dominant wavelength is very long at about 400 m. A wave-current interaction model is used to simulate the wave refraction and reflection at the Gulf Stream boundary. We find that wave refraction is the dominant mechanism at the Gulf Stream boundary for these very long oceanic waves, while wave reflection is not a dominant factor. The waves turn about 15 degrees from their original direction.