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Ocean Science An interactive open-access journal of the European Geosciences Union
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Volume 13, issue 3
Ocean Sci., 13, 483–494, 2017
https://doi.org/10.5194/os-13-483-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ocean Sci., 13, 483–494, 2017
https://doi.org/10.5194/os-13-483-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 22 Jun 2017

Research article | 22 Jun 2017

Trapped planetary (Rossby) waves observed in the Indian Ocean by satellite borne altimeters

Yair De-Leon and Nathan Paldor Yair De-Leon and Nathan Paldor
  • Fredy and Nadine Herrmann Institute of Earth Sciences, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem, 9190401, Israel

Abstract. Using 20 years of accurately calibrated, high-resolution observations of sea surface height anomalies (SSHAs) by satellite borne altimeters, we show that in the Indian Ocean south of the Australian coast the low-frequency variations of SSHAs are dominated by westward propagating, trapped, i.e., non-harmonic, Rossby (Planetary) waves. Our results demonstrate that the meridional-dependent amplitudes of the SSHAs are large only within a few degrees of latitude next to the southern Australian coast while farther in the ocean they are uniformly small. This meridional variation of the SSHA signal is typical of the amplitude structure in the trapped wave theory. The westward propagation speed of the SSHA signal is analyzed by employing three different methods of estimation. Each one of these methods yields speed estimates that can vary widely between adjacent latitudes but the combination of at least two of the three methods yields much smoother variation. The estimates obtained in this manner show that the observed phase speeds at different latitudes exceed the phase speeds of harmonic Rossby (planetary) waves by 140 to 200 % (which was also reported in previous studies). In contrast, the theory of trapped Rossby (planetary) waves in a domain bounded by a wall on its equatorward side yields phase speeds that approximate more closely the observed phase speeds in the study area.

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The paper analyzes sea surface height anomalies (SSHAs) observed in the Indian Ocean south of Australia by combining several known methods for phase speed determination. The observed speeds and the meridional variations of the amplitudes of these signals are compared with two theoretical expressions for the phase speed and meridional amplitude structure of Rossby waves. The paper concludes that both the meridional structure of the SSHAs and their phase speeds fit those of trapped Rossby waves.
The paper analyzes sea surface height anomalies (SSHAs) observed in the Indian Ocean south of...
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