Wave refraction by warm core rings

Abstract

A numerical model for refraction of ocean swell by currents associated with a warm core ring was developed and tested with Seasat synthetic aperture radar (SAR) data. The wave field of SAR orbit 1232 was measured using optical Fourier transforms. The wave refraction model produced rays by simultaneous, numerical integration of the Hamiltonian ray equations applied to a moving medium. Wave orthogonals were constructed from wave number vectors calculated at each incremental time step. The flow field used by the model to simulate a warm ring was a steady, circular jet, with the radial profile of tangential velocity composed of a power function joined to a Gaussian. Initial wave conditions for simulation of refraction by the SAR‐imaged ring were determined from measurements outside the ring. No data were available from which to determine the current field of the SAR‐imaged ring, so the current field input to the model was adjusted until the output wave field most nearly resembled the SAR observations. The relative locations of convergence and divergence of rays were as observed on the SAR image, and the relative energy density in crossed seas was correctly predicted. However, predicted patterns of wavelength variation (presuming that incident waves were uniform in wavelength) were not observed.