An analysis of Rossby waves in the Pacific Ocean from GEOSAT altimetry data

Quasigeostrophic Rossby waves are solutions to the unforced simplified dynamics of the ocean. The measurement of Rossby waves would add to the confidence that the simplified quasigeostrophic dynamics can represent oceanic processes of large time and space scale.; Rossby waves are defined by a particular relation (a dispersion relation) between their propagation direction and wavelength (characterized by their wavenumber), and their frequency. There are two methods for searching the GEOSAT data for phenomena consistent with this unique relation. The first method fits the dispersion relation to the data by calculating the amplitude of Rossby waves from a least squares fit of the waves to the GEOSAT sea surface variability. This fitting of Rossby waves is carried out over the entire Pacific Ocean in 10 degree squares. Both barotropic and first baroclinic mode Rossby waves are fit to the GEOSAT data. It is shown that there is variability in the GEOSAT data significantly above the data noise level which can be explained by Rossby wave dynamics. The amplitudes in the squares obey expected dynamics of Rossby waves and compare well to previous studies.; The second method of observing Rossby waves in the GEOSAT data involves computing the spatial patterns of sea surface height at particular frequencies. The spatial variations at each frequency are examined for Rossby waves. This is done over a region of the Pacific between San Francisco and Hawaii because this particular region has been used for many previous studies of Rossby waves. Wave propagation may be seen in the phase maps of the spatial variability at the frequencies. These waves are propagating in the directions and with the wavelengths indicated by the least squares Rossby wave fit.; These analyses provide evidence of the existence of Rossby waves throughout the Pacific Ocean. Rossby waves may be generated at the eastern boundary, most probably from changes in the strength of basin scale gyres. Other Rossby waves observed by the linear dispersion relation are probably generated by wind with some resonant interaction. New results show barotropic waves generated along the equator sending energy propagating toward the poles. (Abstract shortened with permission of author.)...