Use of the 3D radon transform to examine the properties of oceanic Rossby waves
Use of the 3D radon transform to examine the properties of oceanic Rossby waves
One of the most successful applications of satellite-borne radar altimeter data over the oceans in recent years has been the extraction of information about long-wavelength baroclinic Rossby (or planetary) waves, which play a significant role in ocean circulation and climate dynamics. These waves cross ocean basins from east to west at speeds of few centimetres per second at mid-latitudes. The cross-basin propagation time may therefore be several months or even years and an accurate estimation of the speed of the waves is important. We review the methods for obtaining information on Rossby wave velocity from altimetry data, particularly the two-dimensional Radon transform. Unfortunately the use of longitude-time plots, although it allows the estimation of the zonal phase speeds, does not give any information on the speed vector when the propagation of the waves is not purely zonal (east-west). We show how the two-dimensional Radon Transform can be generalised to three dimensions, enabling not only the true propagation velocity component to be determined, but also the direction of the waves and thus any deviation from the pure-westward case. As examples of the application of this extended technique, we show maps of direction, speed and energy of Rossby waves in the North Atlantic Ocean.
planetary waves, rossby waves, radon transform, north atlantic ocean
1558-1566
Challenor, P.G.
a7e71e56-8391-442c-b140-6e4b90c33547
Cipollini, P.
276e356a-f29e-4192-98b3-9340b491dab8
Cromwell, D.
29efcc84-7f42-4fec-921c-18115a22be9a
2001
Challenor, P.G.
a7e71e56-8391-442c-b140-6e4b90c33547
Cipollini, P.
276e356a-f29e-4192-98b3-9340b491dab8
Cromwell, D.
29efcc84-7f42-4fec-921c-18115a22be9a
Abstract
One of the most successful applications of satellite-borne radar altimeter data over the oceans in recent years has been the extraction of information about long-wavelength baroclinic Rossby (or planetary) waves, which play a significant role in ocean circulation and climate dynamics. These waves cross ocean basins from east to west at speeds of few centimetres per second at mid-latitudes. The cross-basin propagation time may therefore be several months or even years and an accurate estimation of the speed of the waves is important. We review the methods for obtaining information on Rossby wave velocity from altimetry data, particularly the two-dimensional Radon transform. Unfortunately the use of longitude-time plots, although it allows the estimation of the zonal phase speeds, does not give any information on the speed vector when the propagation of the waves is not purely zonal (east-west). We show how the two-dimensional Radon Transform can be generalised to three dimensions, enabling not only the true propagation velocity component to be determined, but also the direction of the waves and thus any deviation from the pure-westward case. As examples of the application of this extended technique, we show maps of direction, speed and energy of Rossby waves in the North Atlantic Ocean.
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Published date: 2001
Keywords:
planetary waves, rossby waves, radon transform, north atlantic ocean
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Local EPrints ID: 120
URI: http://eprints.soton.ac.uk/id/eprint/120
ISSN: 0739-0572
PURE UUID: 953ec119-094e-4e57-b926-e435ab636380
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Date deposited: 14 Jan 2004
Last modified: 15 Mar 2024 04:36
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Author:
P.G. Challenor
Author:
P. Cipollini
Author:
D. Cromwell
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