Observations of Rossby wave propagation in the Northeast Atlantic with TOPEX/POSEIDON altimetry

A technique is described to observe Rossby waves in the oceans using altimeter data, which makes use of longitude/time diagrams of sea surface height anomalies at a given latitude, relying on the zonal propagation of those waves. By means of the Fast Fourier and Radon Transforms of the longitude/time diagrams it is possible to locate the spectral components corresponding to wave propagation and to give an approximate estimation of some of their characteristics such as their height and speed. The results obtained by using data from the TOPEX/POSEIDON radar altimeters in the Northeast Atlantic highlight a narrow ‘preferred’ zonal band of propagation for Rossby waves around 33°–34° N. The speeds of the dominant signals at different latitudes have been computed both in Fourier space and in Radon space: they are in good agreement with the prediction of a revised theory of Rossby wave propagation, which has recently been introduced to explain the discrepancy between observed wave speeds and the speeds computed from the classical theory.