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On the impact of mispointing error and hamming filtering on altimeter waveform retracking and skewness retrieval

On the impact of mispointing error and hamming filtering on altimeter waveform retracking and skewness retrieval
On the impact of mispointing error and hamming filtering on altimeter waveform retracking and skewness retrieval
Ground-based processing of radar altimeter signals has improved the accuracy of geophysical information retrieved from the shape of the waveforms over the ocean. Information about the nonlinear nature of ocean waves (wave skewness) can now be extracted (Gómez-Enri et al. 2006), but first estimates of wave skewness returned a large percentage of negative values, which have no physical meaning. Here, we investigate two possible causes of these negative skewness values using simulations of ocean waveforms for the Envisat RA-2 altimeter: the Hamming filter applied in the altimeter on-board processing and discrepancies between the real mispointing of the altimeter and the value assumed by the retracking algorithm. The Hamming filter strongly affects the retrieval of the parameters at low wave conditions, but it is not the responsible for the negative skewness. It is the second effect that plays a key role in the value of the skewness retrieved.
Radar altimetry, retracking, attitude, signal processing, wave-skewness
0149-0419
217-233
Gomez-Enri, J.
52626f7d-16f6-4d53-99bc-82ea43d90aef
Srokosz, M.A.
1e0442ce-679f-43f2-8fe4-9a0f0174d483
Gommenginger, C.P.
f0db32be-34bb-44da-944b-c6b206ca4143
Challenor, P.G.
a7e71e56-8391-442c-b140-6e4b90c33547
Milagro-Pérez, M.P.
39e849d2-218f-4027-b88f-f316718ac0cb
Gomez-Enri, J.
52626f7d-16f6-4d53-99bc-82ea43d90aef
Srokosz, M.A.
1e0442ce-679f-43f2-8fe4-9a0f0174d483
Gommenginger, C.P.
f0db32be-34bb-44da-944b-c6b206ca4143
Challenor, P.G.
a7e71e56-8391-442c-b140-6e4b90c33547
Milagro-Pérez, M.P.
39e849d2-218f-4027-b88f-f316718ac0cb

Gomez-Enri, J., Srokosz, M.A., Gommenginger, C.P., Challenor, P.G. and Milagro-Pérez, M.P. (2007) On the impact of mispointing error and hamming filtering on altimeter waveform retracking and skewness retrieval. Marine Geodesy, 30 (3), 217-233. (doi:10.1080/01490410701438166).

Record type: Article

Abstract

Ground-based processing of radar altimeter signals has improved the accuracy of geophysical information retrieved from the shape of the waveforms over the ocean. Information about the nonlinear nature of ocean waves (wave skewness) can now be extracted (Gómez-Enri et al. 2006), but first estimates of wave skewness returned a large percentage of negative values, which have no physical meaning. Here, we investigate two possible causes of these negative skewness values using simulations of ocean waveforms for the Envisat RA-2 altimeter: the Hamming filter applied in the altimeter on-board processing and discrepancies between the real mispointing of the altimeter and the value assumed by the retracking algorithm. The Hamming filter strongly affects the retrieval of the parameters at low wave conditions, but it is not the responsible for the negative skewness. It is the second effect that plays a key role in the value of the skewness retrieved.

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More information

Published date: July 2007
Keywords: Radar altimetry, retracking, attitude, signal processing, wave-skewness

Identifiers

Local EPrints ID: 44068
URI: http://eprints.soton.ac.uk/id/eprint/44068
ISSN: 0149-0419
PURE UUID: 50534d9a-3ce7-487b-ac7f-7879f07af6f7

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Date deposited: 12 Feb 2007
Last modified: 15 Mar 2024 09:00

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Contributors

Author: J. Gomez-Enri
Author: M.A. Srokosz
Author: C.P. Gommenginger
Author: P.G. Challenor
Author: M.P. Milagro-Pérez

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