Sentinel‐3A Views Ocean Variability More Accurately at Finer Resolution

Heslop, Emma; Román, Antonio Sánchez; Pascual, Ananda; Rodríguez, D.; Reeve, Krissy; Faugère, Yannice; Raynal, Matthias

doi:10.1002/2017gl076244

Cited by 25 publications

(21 citation statements)

References 27 publications

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“…The Sentinel‐3 altimeter (red lines in Figure ) uses delayed Doppler (or synthetic aperture radar) processing (European Organisation for the Exploitation of Meteorological Satellites, ; Raney, ), which is designed to achieve significantly higher signal‐to‐noise ratios (Heslop et al, ). However, Sentinel‐3's Sun‐synchronous orbit, with a 27‐day repeat, is distinct from that of previous altimeters (cf.…”

Section: Methodsmentioning

confidence: 99%

Characterizing the Transition From Balanced to Unbalanced Motions in the Southern California Current

et al. 2019

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As observations and models improve their resolution of oceanic motions at ever finer horizontal scales, interest has grown in characterizing the transition from the geostrophically balanced flows that dominate at large‐scale to submesoscale turbulence and waves that dominate at small scales. In this study we examine the mesoscale‐to‐submesoscale (100 to 10 km) transition in an eastern boundary current, the southern California Current System (CCS), using repeated acoustic Doppler current profiler transects, sea surface height from high‐resolution nadir altimetry and output from a (1/48)° global model simulation. In the CCS, the submesoscale is as energetic as in western boundary current regions, but the mesoscale is much weaker, and as a result the transition lacks the change in kinetic energy (KE) spectral slope observed for western boundary currents. Helmholtz and vortex‐wave decompositions of the KE spectra are used to identify balanced and unbalanced contributions. At horizontal scales greater than 70 km, we find that observed KE is dominated by balanced geostrophic motions. At scales from 40 to 10 km, unbalanced contributions such as inertia‐gravity waves contribute as much as balanced motions. The model KE transition occurs at longer scales, around 125 km. The altimeter spectra are consistent with acoustic Doppler current profiler/model spectra at scales longer than 70/125 km, respectively. Observed seasonality is weak. Taken together, our results suggest that geostrophic velocities can be diagnosed from sea surface height on scales larger than about 70 km in the southern CCS.

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Section: Methodsmentioning

confidence: 99%

Characterizing the Transition From Balanced to Unbalanced Motions in the Southern California Current

et al. 2019

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“…The main sources of noise come from the altimeter waveform retracking algorithms, instrumental noise, and geophysical variability within the altimeter footprint (Dibarboure et al, 2014;Sandwell & Smith, 2005;Thibaut et al, 2010). Analysis of fine-scale ocean dynamics then requires preliminary noise filtering (e.g., Heslop et al, 2017;Morrow et al, 2017). To analyze and filter the altimeter data, we use an approach described in Kopsinis and McLaughlin (2009), the key part of which is the nonparametric EMD (Huang et al, 1998;Wu & Huang, 2004).…”

Section: Methods: Emd Of Along-track Altimeter Datamentioning

confidence: 99%

Ocean Surface Wave‐Current Signatures From Satellite Altimeter Measurements

Quilfen

Chapron

2019

Geophysical Research Letters

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Ocean currents can strongly impact the propagation of swell systems. Satellite altimetry routinely provides measurements of ocean surface significant wave heights (Hs). A self‐consistent space‐scale decomposition is applied to Hs measurements obtained from different altimeters. This method helps reveal overlooked statistical properties at scales less than 100 km, where mesoscale and submesoscale upper ocean circulation drives a significant part of the variability in the coupled ocean‐atmosphere system. In particular, systematic signatures related to wave‐current interactions are clear at global and regional scales. In the Agulhas current system, the proposed space‐scale decomposition further reveals organized and persistent patterns. To leading order, the redistribution of swell energy follows the cumulative impact of the large‐scale current vorticity field on wave train kinematics. This relationship causes significant swell ray deflection and localized trapping phenomena, which are adequately captured by altimeter measurements.

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“…New generations of SAR altimeter missions have demonstrated that compared to conventional altimetry (or low-resolution mode), this technique significantly reduces the measurements level of noise and improves the along-track spatial resolution (Boy et al, 2017). The comparison between altimetry, ocean gliders and ADCP showed a significant improvement, order 30% in resolution and 42% in velocity accuracy using a synthetic aperture radar mode with respect to lower-resolution mode of conventional altimetry (Heslop et al, 2017). Integrating the three datasets provided valuable insight into the variability of oceanographic features, in an area of the Mediterranean that remains chronically under sampled and has demonstrated benefits to improve knowledge on coastal and fine-scale dynamics.…”

Section: Opportunities For Integrationmentioning

confidence: 98%

Requirements for a Coastal Hazards Observing System

et al. 2019

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Coastal zones are highly dynamical systems affected by a variety of natural and anthropogenic forcing factors that include sea level rise, extreme events, local oceanic and atmospheric processes, ground subsidence, etc. However, so far, they remain poorly monitored on a global scale. To better understand changes affecting world coastal zones and to provide crucial information to decision-makers involved in adaptation to and mitigation of environmental risks, coastal observations of various types need to be collected and analyzed. In this white paper, we first discuss the main forcing agents acting on coastal regions (e.g., sea level, winds, waves and currents, river runoff, sediment supply and transport, vertical land motions, land use) and the induced coastal response (e.g., shoreline position, estuaries morphology, land topography at Frontiers in Marine Science | www.frontiersin.org 1 July 2019 | Volume 6 | Article 348Benveniste et al.Requirements for a Coastal Zone Observing System the land-sea interface and coastal bathymetry). We identify a number of space-based observational needs that have to be addressed in the near future to understand coastal zone evolution. Among these, improved monitoring of coastal sea level by satellite altimetry techniques is recognized as high priority. Classical altimeter data in the coastal zone are adversely affected by land contamination with degraded range and geophysical corrections. However, recent progress in coastal altimetry data processing and multisensor data synergy, offers new perspective to measure sea level change very close to the coast. This issue is discussed in much detail in this paper, including the development of a global coastal sea-level and sea state climate record with mission consistent coastal processing and products dedicated to coastal regimes. Finally, we present a new promising technology based on the use of Signals of Opportunity (SoOp), i.e., communication satellite transmissions that are reutilized as illumination sources in a bistatic radar configuration, for measuring coastal sea level. Since SoOp technology requires only receiver technology to be placed in orbit, small satellite platforms could be used, enabling a constellation to achieve high spatio-temporal resolutions of sea level in coastal zones.

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Sentinel‐3A Views Ocean Variability More Accurately at Finer Resolution

Cited by 25 publications

References 27 publications

Characterizing the Transition From Balanced to Unbalanced Motions in the Southern California Current

Characterizing the Transition From Balanced to Unbalanced Motions in the Southern California Current

Ocean Surface Wave‐Current Signatures From Satellite Altimeter Measurements

Requirements for a Coastal Hazards Observing System

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