Calibration of Ocean Wave Measurements by the TOPEX, <i>Jason-1</i>, and <i>Jason-2</i> Satellites

Ray, Richard D.; Beckley, B. D.

doi:10.1080/01490419.2012.718611

Cited by 22 publications

(18 citation statements)

References 30 publications

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“…These values are smaller than those for matchups of altimeters with buoys (e.g. Queffeulou, 2003;Abdalla et al, 2010;Ray and Beckley, 2012). However, they are similar to those found for inter-altimeter comparisons of Jason-1 with ERS-2 (Zieger et al, 2009) and a little larger than the Jason-2 matchups with Jason-1 during the tandem phase (Quartly, 2010a), when the time difference was negligible.…”

Section: Statistics Of Crossover Comparisonsmentioning

confidence: 52%

“…If the buoy data are taken as ground truth, the errors in wave height for Jason-2 are between 0.23 m and 0.39 m depending upon analytical approach (Abdalla et al, 2010;Ray and Beckley, 2012) and ~1.5 m s -1 for wind speed (Abdalla et al, 2010). However, given the above discussion on the nature of the causes of some of these errors, the discrepancies between two altimeters might be expected to be smaller.…”

Section: Data Sources and Match-up Requirementsmentioning

confidence: 98%

“…Similar values have been adopted for altimeter validation by other researchers (Cotton andCarter. 1994, Queffeulou 2004), whilst Ray and Beckley (2012) expanded the spatial threshold to 70 km. Matchups between altimeters in orbits of different inclination are likely to result in the tracks crossing one another i.e.…”

Section: Data Sources and Match-up Requirementsmentioning

confidence: 99%

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Metocean Comparisons of Jason-2 and AltiKa—A Method to Develop a New Wind Speed Algorithm

Quartly

2015

Marine Geodesy

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As well as range, the AltiKa altimeter provides estimates of wave height, H s and normalized backscatter, σ 0 , that need to be assessed prior to statistics based on them being included in climate databases. An analysis of crossovers with the Jason-2 altimeter shows AltiKa H s values to be biased high by only ~0.05m, with a standard deviation (s.d.) of ~0.1m for 7-point averages. AltiKa's σ 0 values are 2.5-3 dB less than those from Jason-2, with a s.d. of ~0.3 dB, with these relatively large mismatches to be expected as AltiKa measures a different part of the spectrum of sea surface roughness. A new wind speed algorithm is developed through matching a histogram of σ 0 values to that for Jason-2 wind speeds. The algorithm is robust to the use of short durations of data, with a consistency at roughly the 0.1 m/s level. Incorporation of H s as a secondary input reduces the assessed error at crossovers from 0.82 m/s to 0.71 m/s. A comparison across all altimeter frequencies used to date demonstrates that the lowest wind speeds preferentially develop the shortest scales of roughness.

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Section: Statistics Of Crossover Comparisonsmentioning

confidence: 52%

Section: Data Sources and Match-up Requirementsmentioning

confidence: 98%

Section: Data Sources and Match-up Requirementsmentioning

confidence: 99%

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Metocean Comparisons of Jason-2 and AltiKa—A Method to Develop a New Wind Speed Algorithm

Quartly

2015

Marine Geodesy

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“…(top) Original altimetric waves heights as collected by TOPEX and reported on the MGDR‐B data records. Figure is slightly modified from Ray and Beckley (). (bottom) Similar analysis using identical buoy data for the retracked TOPEX data of Callahan et al ().…”

Section: Topex Point Target Response Changesmentioning

confidence: 99%

On the “Cal‐Mode” Correction to TOPEX Satellite Altimetry and Its Effect on the Global Mean Sea Level Time Series

et al. 2017

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Comparison of satellite altimetry against a high‐quality network of tide gauges suggests that sea‐surface heights from the TOPEX altimeter may be biased by ±5 mm, in an approximate piecewise linear, or U‐shaped, drift. This has been previously reported in at least two other studies. The bias is probably caused by use of an internal calibration‐mode range correction, included in the TOPEX “net instrument” correction, which is suspect owing to changes in the altimeter's point target response. Removal of this correction appears to mitigate most of the drift problem. In addition, a new time series based on retracking the TOPEX waveforms, again without the calibration‐mode correction, also reduces the drift aside for a clear problem during the first 2 years. With revision, the TOPEX measurements, combined with successor Jason altimeter measurements, show global mean sea level rising fairly steadily throughout most of 24 year time period, with rates around 3 mm/yr, although higher over the last few years.

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“…For examples, see Durrant et al (2009), Queffeulou (2004, Ray and Beckley (2012), and Zieger et al (2009), and the references within. For examples, see Durrant et al (2009), Queffeulou (2004, Ray and Beckley (2012), and Zieger et al (2009), and the references within.…”

Section: ) Satellite Altimetermentioning

confidence: 99%

Wave Measurement Intercomparison and Platform Evaluation during the ITOP (2010) Experiment

Collins

Lund

Ramos

et al. 2014

Journal of Atmospheric and Oceanic Technology

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Spectral wave parameters from 11 platforms, measured during the recent Impact of Typhoons on the Ocean in the Pacific (ITOP) experiment, are intercompared. Two moorings, separated by ;180 km, were deployed in a section of ''typhoon alley'' off the coast of Taiwan for 4 months. Each mooring consisted of an Air-Sea Interaction Spar (ASIS) buoy that was tethered to a moored Extreme Air-Sea Interaction (EASI) buoy. EASI, the design of which is based on the hull of a 6-m Navy Oceanographic Meteorological Automatic Device (NOMAD) buoy, is validated as a 1D wave sensor against the established ASIS. Also, during this time three drifting miniature wave buoys, a wave-measuring marine radar on the Research Vessel Roger Revelle, and several overpasses of Jason-1 (C and Ku bands) and Jason-2 (Ku band) satellite altimeters were within 100 km of either the northern or southern mooring site. These additional measurements were compared against both EASI buoys. Findings are in-line with previous wave parameter intercomparisons. A corroborated measurement of mean wave direction and direction at the peak of the spectrum from the EASI buoy is presented. Consequently, this study is the first published account of directional wave information that has been successfully gathered from a buoy with a 6-m NOMAD-type hull. This result may be applied to improve operational coverage of wave direction. A high level of confidence is established in the ITOP wave data. Advantages and disadvantages of the different sensor types are discussed, which may be useful for the design of future field experiments.

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Calibration of Ocean Wave Measurements by the TOPEX, Jason-1, and Jason-2 Satellites

Cited by 22 publications

References 30 publications

Metocean Comparisons of Jason-2 and AltiKa—A Method to Develop a New Wind Speed Algorithm

Metocean Comparisons of Jason-2 and AltiKa—A Method to Develop a New Wind Speed Algorithm

On the “Cal‐Mode” Correction to TOPEX Satellite Altimetry and Its Effect on the Global Mean Sea Level Time Series

Wave Measurement Intercomparison and Platform Evaluation during the ITOP (2010) Experiment

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