Arctic sea surface height maps from multi-altimeter combination

Prandi, Pierre; Poisson, Jean-Christophe; Faugère, Yannice; Guillot, Amandine; Dibarboure, Gérald

doi:10.5194/essd-2021-123

Cited by 3 publications

(5 citation statements)

References 26 publications

(39 reference statements)

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“…Whereas the circulation in these polar regions is at much smaller scales (e.g., Newton et al 1974) and higher resolution SSH products are required to address current oceanographic questions such as the Beaufort Gyre stability mechanisms (Doddridge et al 2019). Higher resolution datasets have been released (Prandi et al 2021) that leverage recent data processing advances with current altimeter constellation capabilities.…”

Section: Polar Ocean Circulationmentioning

confidence: 99%

“…In recent years, up to 4 satellites have been providing data at latitudes greater than 66° (CryoSat-2, SARAL/AltiKa, Sentinel-3A and 3B), and combining these observations through optimal interpolation (Pascual et al 2006) provides polar ocean fields with an unprecedented resolution. Typical sea level fields from a mono-mission product (from Armitage et al 2016) and a multi-mission product (from Prandi et al 2021) are shown on Fig. 14, from different periods since these products do not overlap in time.…”

Section: Polar Ocean Circulationmentioning

confidence: 99%

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Ocean Circulation from Space

Morrow

Rio

et al. 2023

Surv Geophys

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This paper reviews the recent progress in our estimation of ocean dynamic topography and the derived surface geostrophic currents, mainly based on multiple nadir radar altimeter missions. These altimetric observations provide the cornerstone of our ocean circulation observing system from space. The largest signal in sea surface topography is from the mean surface dominated by the marine geoid, and we will discuss recent progress in observing the mean ocean circulation from altimetry, once the geoid and other corrections have been estimated and removed. We then address the recent advances in our observations of the large-scale and mesoscale ocean circulation from space, and the particular challenges and opportunities for new observations in the polar regions. The active research in the ocean barotropic tides and internal tidal circulation is also presented. The paper also addresses how our networks of global multi-satellite and in situ observations are being combined and assimilated to characterize the four-dimensional ocean circulation, for climate research and ocean forecasting systems. For the future of ocean circulation from space, the need for continuity of our current observing system is crucial, and we discuss the exciting enhancement to come with global wide-swath altimetry, the extension into the coastal and high-latitude regions, and proposals for direct total surface current satellites in the 2030 period.

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Section: Polar Ocean Circulationmentioning

confidence: 99%

Section: Polar Ocean Circulationmentioning

confidence: 99%

Ocean Circulation from Space

Morrow

Rio

et al. 2023

Surv Geophys

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“…For both missions, the most drastic rejection occurs in the ice-contaminated areas; Indeed, the processing applied mainly focuses on the open ocean and is not adapted to the possible measurements available over leads. As described by (Prandi et al, 2021), the observation of the SSH in such narrow ice-free areas requires a specific 345 delay doppler processing not implemented here. Consequently, no efforts have been made to keep the measurements over leads.…”

Section: Data Availability and Gain Brought By The 5hz Altimeter Proc...mentioning

confidence: 99%

“…PISTACH (Mercier et al, 2010); X-TRACK (Birol et al, 2017;Roblou et al, 2011); X-TRACK-ALES (Birol et al, 2021), ESA EO4SIBS (Grégoire and EO4SIBS consortium (ESA project), 2021)). Others are dedicated to ice-contaminated areas, focusing on the sea surface over leads (Auger et al, 2022;Prandi et al, 2021). In this paper we focus on the DUACS high resolution L3 altimeter experimental regional products, primarily intended for high resolution regional model applications and 100 guided by the CMEMS requirements.…”

Section: Introduction 40mentioning

confidence: 99%

Refining the resolution of DUACS along track (level 3) altimeter Sea Level products

Pujol

Dupuy²,

Vergara³

et al. 2022

Preprint

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Abstract. This paper describes a high-resolution Level-3 (L3) altimeter Data Unification and Altimeter Combination System (DUACS) experimental regional product developed with support from the French space agency (CNES). Deduced from full rate (20 Hz to 40 Hz) Level-2 (L2) altimeter measurements, this product delivers Sea Level Anomalies (SLA) and other essential physical variables with a nearly 1-Km sampling over the North Atlantic 0cean. It allows us to resolve wavelengths from ~35 km to ~55 Km depending on the altimeter considered. This was made possible by recent advances in radar altimeter processing for both Synthetic aperture Radar (SAR) and Low-Resolution Mode (LRM) measurements, and improvements made to different stages of the DUACS processing chain. Firstly, the new adaptive and LR-RMC (Low Resolution with Range Migration Correction) processing techniques were considered for Jason and Sentinel-3 (S3A) respectively. They significantly reduce errors at short wavelengths and, for the adaptive processing, possible land contamination near the coast. Next, up-to-date geophysical and environmental corrections were selected for this production. This includes specific corrections intended to reduce the measurement noise on LRM measurement and thus enhance the observability at short wavelengths. Compared to the 1 Hz product, the observable wavelength reached with the experimental high-resolution product are reduced by up to one third, or up to half in the North-East Atlantic region. The residual noises were optimally filtered from full rate measurements taking into consideration the different observing capabilities of the altimeters processed. A specific data recovery strategy was applied, significantly optimizing the data availability both in the coastal and open ocean. This experimental L3 product is thus better resolved than the conventional 1 Hz product, especially near the coast where it is defined up to ~5 km against ~10 km for the 1 Hz version. The multi-mission cross-calibration processing was also optimized with an improved Long Wavelengths Error (LWE) correction leading to a better consistency between tracks with an 9–15 % reduction of SLA variance at cross-over. The experimental L3 product improves the overall consistency with tide gauge measurements with a reduction of the variance of the SLA differences by 5 and 17 % compared to the 1 Hz product from S3A and Jason-3 (J3) measurements respectively. Primarily intended for regional applications, this product can significantly contribute to improving high resolution numerical model outputs via data assimilation. It also opens new perspectives for a better understanding of regional sea surface dynamics, with an improved representation of the coastal currents and a refined spectral content that reveals the unbalanced signal.

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“…However, the temporal and spatial resolution of water level change monitoring using a single altimeter is limited, and synergistic multi-altimeter can achieve higher spatial and temporal resolution. Prandi et al (2021) combined Cryosat-2, SARAL and Sentinel-3 altimeter data to construct an Arctic sea level anomaly(SLA) dataset, improving the resolution of this class of products. Sun et al (2020) used multiple altimeter data to monitor sea level variability in the China sea and its vicinity.…”

Section: Introductionmentioning

confidence: 99%

Synergistic multi-altimeter for estimating water level in the coastal zone of Beibu Gulf using SEL, ALES + and BFAST algorithms

Qin

Yao

et al. 2023

Front. Mar. Sci.

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Accurately monitoring and predicting the large-scale dynamic changes of water levels in coastal zones is essential for its protection, restoration and sustainable development. However, there has been a challenge for achieving this goal using a single radar altimeter and retracking technique due to the diversity and complexity of coastal waveforms. To solve this issue, we proposed an approach of estimating water level of the coastal zone in Beibu Gulf, China, by combination of waveform classifications and multiple sub-waveform retrackers. This paper stacked Random Forest (RF), XGBoost and CatBoost algorithms for building an ensemble learning (SEL) model to classify coastal waveforms, and further evaluated the performance of three retracking strategies in refining waveforms using Cryosat-2, SARAL, Sentinel-3 altimeters. We compared the estimation accuracy of the coastal water levels between the single altimeter and synergistic multi-altimeter, and combined Breaks for Additive Season and Trend (BFAST), Mann-Kendall mutation test (MK) with Long Short-Term Memory (LSTM) algorithms to track the historical change process of coastal water levels, and predict its future development trend. This paper found that: (1) The SEL algorithm achieved high-precision classification of different coastal waveforms with an average accuracy of 0.959, which outperformed three single machine learning algorithms. (2) Combination of Threshold Retracker and ALES+ Retracker (TR_ALES+) achieved the better retracking quality with an improvement of correlation coefficient (R, 0.089~0.475) and root mean square error (RMSE, 0.008∼ 0.029 m) when comparing to the Threshold Retracker & Primary Peak COG Retracker and Threshold Retracker & Primary Peak Threshold Retracker. (3) The coastal water levels of Cryosat-2, SARAL, Sentinel-3 and multi-altimeter were in good agreement (R>0.66, RMSE<0.135m) with Copernicus Climate Change Service (C3S) water level. (4) The coastal water levels of the Beibu Gulf displayed a slowly rising trend from 2011 to 2021 with an average annual growth rate of 8mm/a, its lowest water level focused on May-August, the peak of water level was in October-November, and the average annual growth rate of water level from 2022-2031 was about 0.6mm/a. These results can provide guidance for scientific monitoring and sustainable management of coastal zones.

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Arctic sea surface height maps from multi-altimeter combination

Cited by 3 publications

References 26 publications

Ocean Circulation from Space

Ocean Circulation from Space

Refining the resolution of DUACS along track (level 3) altimeter Sea Level products

Synergistic multi-altimeter for estimating water level in the coastal zone of Beibu Gulf using SEL, ALES + and BFAST algorithms

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