Jason-1 Altimeter Ground Processing Look-Up Correction Tables

Thibaut, P.; Amarouche, L.; Zanifé, O. Z.; Steunou, N.; Vincent, Patrick; Raizonville, P.

doi:10.1080/01490410490902133

Cited by 32 publications

(17 citation statements)

References 16 publications

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“…Figure 2 shows corresponding data at C-band. As is well known (e.g., Thibaut et al, 2004), the C-band altimetric wave data are considerably noisier; the RMS difference in this case between Jason-1 and Jason-2 is 44 cm. For the remainder of this paper, only the more precise Ku-band data will be considered.…”

Section: Example Profilesmentioning

confidence: 56%

“…Thibaut et al (2004) present H s histograms for Jason-1 with a large spike at zero, implying a fairly significant number of these zero values. For the period of the verification campaign we find 0.56% of the Jason-2 data and 0.39% of the Jason-1 data are exactly zero.…”

Section: Example Profilesmentioning

confidence: 99%

“…Thibaut et al (2004) state that such zeroes arise from waves estimated as negative but truncated to zero. Aside from deleting such data entirely, which would tend to limit severely the data returns in some regions such as the Mediterranean, it is not always clear how best to handle such problems.…”

Section: Example Profilesmentioning

confidence: 99%

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

Ray

Beckley

2012

Marine Geodesy

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The calibration and validation of ocean wave height measurements by the TOPEX, Jason-1, and Jason-2 satellite altimeters is addressed by comparing the measurements internally among themselves and against independent wave measurements at moored buoys. The two six-month verification campaigns, when two of the satellites made near-simultaneous measurements along the same ground track, are invaluable for such work and reveal subtle aspects that otherwise might go undetected.The two Jason satellites are remarkably consistent; Topex reports waves generally 1-2% larger. External calibration is complicated by some systematic errors in the buoy data. We confirm a recent report by Durrant et al. that Canadian buoys underestimate significant wave heights by about 10% relative to U.S. buoys. Wave heights from all three altimetric satellites require scaling upwards by 5-6% to be consistent with U.S. buoys.

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Section: Example Profilesmentioning

confidence: 56%

Section: Example Profilesmentioning

confidence: 99%

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

Ray

Beckley

2012

Marine Geodesy

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“…Consequently, errors might arise. One effective way to compensate these errors (at least the systemic bias) was to generate look-up tables (LUTs) for further correction [23], [24].…”

Section: Introductionmentioning

confidence: 99%

Compensating the PTR and LPF Features of the HY-2A Satellite Altimeter Utilizing Look-Up Tables

Wang

et al. 2015

IEEE J. Sel. Top. Appl. Earth Observations Remote Sensing

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The point target response (PTR) and low-pass filter (LPF) features of the altimeter (ALT) onboard China's HY-2A satellite are presented and analyzed. Via Monte-Carlo simulation, the look-up tables (LUTs) of the range (epoch), significant wave height (SWH), and backscatter (Sigma0) biases with respect to SWH and attitude angle (ATT) are calculated accounting for the instrument PTR and LPF features using two distinct retracking algorithms (MLE3 and MLE4). The performance of both retracking algorithms are also evaluated in terms of the size of the biases (corrections) produced, and MLE4 is found better. The actual PTR and the Bessel-expression flat surface impulse response (FSIR) are integrated in the simulation procedure to achieve more accurate results. The simulated biases are tabulated by very fine grids of SWH and ATT so that they can be used as corrections in the ground preprocessing procedure (processing prior to Level 2 product) to get better operational ocean products. As verified by the crossover analysis with the Jason-2 ALT, the corrections pertaining to the instrument features significantly improve the accuracy of HY-2A ALT sea level products.Index Terms-Low-pass filter (LPF), maximum likelihood estimation, measurement errors, Monte Carlo methods, radar altimetry.

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“…where T is the onboard tracking range in the Ku band, E is the retracked offset (with time dimension), the factor "c/2 (c is light velocity)" is the scaling factor from traveling time to range, D is the Doppler correction in Ku band, M is the instrument bias due to PTR and LPF features ( [23,24] and 0.180 is a bias (in meters) due to wrong altimeter antenna reference point [25].…”

Section: Altimetry Data Processingmentioning

confidence: 99%

Evaluation of Coastal Sea Level Offshore Hong Kong from Jason-2 Altimetry

Birol

Cazenave

2018

Remote Sensing

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Abstract:As altimeter satellites approach coastal areas, the number of valid sea surface height measurements decrease dramatically because of land contamination. In recent years, different methodologies have been developed to recover data within 10-20 km from the coast. These include computation of geophysical corrections adapted to the coastal zone and retracking of raw radar echoes. In this paper, we combine for the first time coastal geophysical corrections and retracking along a Jason-2 satellite pass that crosses the coast near the Hong-Kong tide gauge. Six years and a half of data are analyzed, from July 2008 to December 2014 (orbital cycles 1-238). Different retrackers are considered, including the ALES retracker and the different retrackers of the PISTACH products. For each retracker, we evaluate the quality of the recovered sea surface height by comparing with data from the Hong Kong tide gauge (located 10 km away). We analyze the impact of the different geophysical corrections available on the result. We also compute sea surface height bias and noise over both open ocean (>10 km away from coast) and coastal zone (within 10 km or 5 km coast-ward). The study shows that, in the Hong Kong area, after outlier removal, the ALES retracker performs better in the coastal zone than the other retrackers, both in terms of noise level and trend uncertainty. It also shows that the choice of the ocean tide solution has a great impact on the results, while the wet troposphere correction has little influence. By comparing short-term trends computed over the 2008.5-2014 time span, both in the coastal zone and in the open ocean (using the Climate Change Initiative sea level data as a reference), we find that the coastal sea level trend is about twice the one observed further offshore. It suggests that in the Hong Kong region, the short-term sea level trend significantly increases when approaching the coast.

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Jason-1 Altimeter Ground Processing Look-Up Correction Tables

Cited by 32 publications

References 16 publications

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

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

Compensating the PTR and LPF Features of the HY-2A Satellite Altimeter Utilizing Look-Up Tables

Evaluation of Coastal Sea Level Offshore Hong Kong from Jason-2 Altimetry

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