Trapped planetary (Rossby) waves observed in the Indian Ocean by satellite borne altimeters
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.,...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-06-01
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| Series: | Ocean Science |
| Online Access: | http://www.ocean-sci.net/13/483/2017/os-13-483-2017.pdf |
| Summary: | 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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| ISSN: | 1812-0784 1812-0792 |