Variability of Rossby wave propagation in the North Atlantic from TOPEX/POSEIDON altimetry

This paper deals with the study of westward-travelling, long-wavelength Rossby waves in the North Atlantic from TOPEX/POSEIDON altimeter data. Nearly three years of altimeter data have been used, starting from November 1992, in order to investigate the variability of this phenomenon. Corrections which are applied to the data set are briefly described: they account for radar propagation effects and geophysical phenomena such as ocean tides. After applying these corrections, the authors analyse time series of sea surface height anomalies to find the signature of Rossby waves. This analysis is carried out in a hybrid spatial-temporal frequency domain. It allows the authors to determine the wavelength, period and phase speed of the various signals which are present in this region. The results show evidence of Rossby waves which are particularly noticeable in the latitude range 33-35/spl deg/ N. Detailed results are given in the paper for latitude 34/spl deg/ N. In particular, as the waves generated in the eastern basin traverse the Mid-Atlantic Ridge a change in the wavelength and speed of the propagating energy is observed.