| The principal objective of this study is to develop a new method to detect wave motion from satellite altimetric measurements of sea surface height. The essence of the approach is to construct a two-dimensional Fourier series representation of the amplitude field in wavenumber space within a prespecified oceanic region. The method uses an iterative, nonlinear least-squares technique based on the Marquardt-Levenberg algorithm to solve for model parameters describing the position, shape, direction of propagation and dispersion characteristics of the wave system.;The Marquardt-Levenberg Fourier series (MLFS) algorithm was used to detect two prominent wave systems in the equatorial Pacific ocean using GEOSAT Exact Repeat Mission altimetry data during the two year period November, 1986 to January, 1989. Kelvin waves associated with the 1986-87 El Nino were investigated and its detected wave characteristics were found to be in accord with linear theory for baroclinic wave motion, earlier field measurements, and another set of satellite observations that employed a time series method of wave field detection. Shear-driven Legeckis waves were also investigated during their time of high activity in the fall of 1988 and characteristics for these eddies were found to be in accord with both linear stability theory and other independent field and satellite observations.;The advantage of the present detection scheme over previous methods lies in its ability to determine modal phase speeds which give the dispersion relation over a finite range of wavenumbers. The group velocity which determines the direction of wave energy transport may then be calculated from the dispersion relation. The variable phase speed decomposition allows reconstruction of the instantaneous spatial structure of the wave system thereby yielding a direct view of amplitude modulations between neighboring waves and structural changes such as the fusion and fission of individual waves. |
