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Open AccessArticle

Sensitivity of Altimeter Wave Height Assessment to Data Selection

Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, Devon PL1 3DH, UK
Author to whom correspondence should be addressed.
Remote Sens. 2020, 12(16), 2608;
Received: 14 July 2020 / Revised: 7 August 2020 / Accepted: 8 August 2020 / Published: 13 August 2020
(This article belongs to the Special Issue Calibration and Validation of Satellite Altimetry)
This paper addresses the issue of how the selection of buoys and the calculation of altimeter averages affect the metrics characterising the errors of altimetric wave height estimates. The use of a 51-point median reduces the sensitivity to occasional outliers, but the quality of this measure can be improved by demanding that there is a minimum number of valid measurements. This had a marked impact in both the open ocean and the coastal zone. It also affected the relative ordering of algorithms’ performances, as some fared poorly when a representative value was gleaned from a single waveform inversion, but had a much better ranking when a minimum of 20 values were used. Validation procedures could also be improved by choosing altimeter-buoy pairings that showed a good consistency. This paper demonstrated an innovative procedure using the median of the different retrackers analysed, which can be easily extended to other data validation exercises. This led to improved comparison statistics for all algorithms in the open ocean, with many showing errors less than 0.2 m, but there was only one strong change in the relative performance of the 11 Jason-3 retrackers. For Sentinel-3A, removing the inconsistent coastal buoys showed that all of the new algorithms had similar errors of just over 0.2 m. Thus, although improvements were found in the procedure used for the Sea State Round Robin exercise, the relative rankings for the buoy calibrations are mostly unaffected. View Full-Text
Keywords: altimeter; validation; buoys; ocean; coastal zone; data-flagging; sensitivity studies; Jason-3; Sentinel-3A altimeter; validation; buoys; ocean; coastal zone; data-flagging; sensitivity studies; Jason-3; Sentinel-3A
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Quartly, G.D.; Kurekin, A.A. Sensitivity of Altimeter Wave Height Assessment to Data Selection. Remote Sens. 2020, 12, 2608.

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