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The National Oceanography Centre, Southampton Retracking Scheme: Measuring Global Ocean Tracker Bias

Jesus Gomez-Enri(1) , Christine Gommenginger(1) , Pilar Villares(2) , Peter Challenor(1) , Meric Srokosz(1) , Jerome Benveniste(3) , and Mark Drinkwater(4)

(1) National Oceanography Centre, Southampton, European Way, SO14 3ZH Southampton, United Kingdom
(2) University of Cadiz, Poligono Rio S.Pedro, s/n, 11510 Puerto Real, Spain
(3) ESRIN-European Space Agency, Via Galileo Galilei, 64, 00044 Frascati, Italy
(4) ESTEC-European Space Agency, Postbus 299, 2200 AG Noordwijk, Netherlands


The National Oceanography Centre, Southampton retracking algorithm has been optimized to retrieve geophysical information from Envisat RA-2 18-Hz ocean averaged waveforms in an operational way. The retracking algorithm is based on Maximum Likelihood Estimation. In its linear form, it retrieves the significant wave height and the time origin. Extra information can be retrieved from its non-linear form, regarding the non-linearity of the ocean waves, introducing a non-linear parameter: wave-skewness. The on-ground retracking of Envisat RA-2 18-Hz ocean averaged waveforms is developed under the assumption of linearity of the ocean waves. Thus, this approximation may introduce a bias in the estimation of the range. We made the first estimations of this tracker bias using Envisat RA-2 ocean waveforms. From the results obtained we estimated a mean tracker bias for the global ocean of 0.13±0.07SWH showing that temporal and regional dependent errors are introduced when using a linear retracker processing approach.


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                 Last modified: 07.10.03