Multiple westward propagating signals in South Pacific sea level anomalies

A. M. Maharaj, N. J. Holbrook, P. Cipollini

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    The characteristics of multiple westward propagating signals in the satellite observed South Pacific sea level anomalies (SLA) between 10°S and 50°S are analyzed using the two-dimensional Radon transform (2D-RT). We test the hypothesis that these signals are most likely to be the signature of the first few baroclinic Rossby wave modes. This involves a comparison of the estimated phase speeds of the 2D-RT peaks against the first four baroclinic mode Rossby wave speeds predicted from the extended theory. The 2D-RT analysis typically identified up to three propagating signals in the SLA and very occasionally, a fourth. The first Radon transform (RT) peak phase speeds corresponded very well with first baroclinic mode Rossby wave phase speed estimates from linear theory between 15°S and 25°S and the extended theory phase speed estimates poleward of 25°S. RT peak 2 speeds were less coherent but fell within the range of extended theory estimates of the first four baroclinic Rossby wave modes, consistent with large-scale Rossby wave dynamics. The relationship between peaks 3 and 4 and the extended theory higher-order baroclinic mode speed estimates varied markedly across the basin. Regional variability in the spectral characteristics of the peaks suggests that different dynamical regimes dominate north and south of 30°S in the South. Pacific basin. The presence of secondary peaks in the middle to high latitudes suggests that higher-order modes may play a role in these regions.

    Original languageEnglish
    Article numberC12016
    Pages (from-to)1-14
    Number of pages14
    JournalJournal of Geophysical Research
    Issue number12
    Publication statusPublished - 8 Dec 2009


    • Rossby waves
    • sea level anomalies
    • Radon transform


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