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1. Training Neural Mapping Schemes for Satellite Altimetry With Simulation Data.

Author

Febvre, Q., Le Sommer, J., Ubelmann, C., and Fablet, R.

Subjects
*DEEP learning, *STANDARD deviations, *ALTIMETRY, *GULF Stream, *SURFACE dynamics, *ARTIFICIAL intelligence
Abstract

Satellite altimetry combined with data assimilation and optimal interpolation schemes have deeply renewed our ability to monitor sea surface dynamics. Recently, deep learning schemes have emerged as appealing solutions to address space‐time interpolation problems. However, the training of state‐of‐the‐art neural schemes on real‐world case‐studies is hindered by the sparse space‐time coverage of the sea surface of real altimetry data set. Here, we introduce an innovative approach that leverages state‐of‐the‐art ocean models to train simulation‐based neural schemes for the mapping of sea surface height and demonstrate their performance on real altimetry data sets. We analyze further how the ocean simulation data set used during the training phase impacts this performance. This experimental analysis covers both the resolution from eddy‐present configurations to eddy‐rich ones, forced simulations versus reanalyzes using data assimilation and tide‐free versus tide‐resolving simulations. Our benchmarking framework focuses on a Gulf Stream region for a realistic 5‐altimeter constellation using NEMO ocean simulations and 4DVarNet mapping schemes. All simulation‐based 4DVarNets outperform the operational observation‐driven and reanalysis products, namely DUACS and GLORYS. The more realistic the ocean simulation data set used during the training phase, the better the mapping. The best 4DVarNet mapping was trained from an eddy‐rich and tide‐free simulation data sets. It improves the resolved longitudinal scale from 151 km for DUACS and 241 km for GLORYS to 98 km and reduces the root mean square error by 23% and 61%. These results open research avenues for new synergies between ocean modeling and ocean observation using learning‐based approaches. Plain Language Summary: To train an artificial intelligence (AI) model, one need to describe a task using data and an evaluation procedure. Here we aim at constructing images related to the ocean surface currents. The satellite data we use provide images of the ocean surface with a lot of missing data (around 95% of missing pixels for a given day), and we aim at finding the values of the missing pixels. Because we don't know the full image, it is challenging to train an AI on this task using only the satellite data. However, today's physical knowledge makes it possible to numerically simulate oceans on big computers. For these simulated oceans, we have access to the gap‐free image, so we can train AI models by first hiding some pixels and checking if the model fill the gaps with the correct values. Here, we explore under which conditions AIs trained on simulated oceans are useful for the real ocean. We show that today's simulated oceans work well for training an AI on this task and that training on more realistic simulated oceans improve the performance of the AI! Key Points: We suggest utilizing ocean simulation data sets to train neural schemes for mapping real altimeter dataThe trained neural scheme improves the spatial scales resolved over the operational mapping product on a GulfStream case study by 30%Using more realistic simulation data sets improves the resulting neural mapping scheme by up to 20% in the spatial scales resolved [ABSTRACT FROM AUTHOR]

Published
2024
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2. Inversion of Sea Surface Currents From Satellite‐Derived SST‐SSH Synergies With 4DVarNets.

Author

Fablet, R., Chapron, B., Le Sommer, J., and Sévellec, F.

Subjects
OCEAN surface topography, DEEP learning, GULF Stream, SURFACE dynamics, OCEAN dynamics, OCEAN temperature, GEOSTROPHIC currents
Abstract

Satellite altimetry offers a unique approach for direct sea surface current observation, but it is limited to measuring the surface‐constrained geostrophic component. Ageostrophic dynamics, prevalent at horizontal scales below 100 km and time scales below 10 days, are often underestimated by ocean reanalyzes employing data assimilation schemes. To address this limitation, we introduce a novel deep learning scheme, rooted in a variational data assimilation formulation with trainable observations and a priori terms, that harnesses the synergies between satellite‐derived sea surface observations, namely sea surface height (SSH) and sea surface temperature (SST), to enhance sea surface current reconstruction. Numerical experiments, conducted using realistic simulations, in a case study area of the Gulf Stream, demonstrate the potential of the proposed scheme to capture ageostrophic dynamics at time scales of 2.5–3.0 days and horizontal scales of 0.5°–0.7°. The analysis of diverse observation configurations, encompassing nadir along‐track altimetry, wide‐swath SWOT (Surface Water and Ocean Topography) altimetry, and SST data, highlights the pivotal role of SST features in retrieving a significant portion of the ageostrophic dynamics (approximately 47%). These findings underscore the potential of deep learning and 4DVarNet schemes in improving ocean reanalyzes and enhancing our understanding of ocean dynamics. Plain Language Summary: Satellite altimetry provides a unique means for direct observation of sea surface currents, but it is confined to the geostrophic component, limiting the recovery of a substantial portion of mesoscale sea surface currents in operational products. To address this limitation, we present a novel deep learning framework, rooted in a variational data assimilation paradigm, that unlocks new avenues for leveraging the synergistic relationships between satellite‐derived sea surface observations, namely sea surface height and sea surface temperature. This innovative scheme demonstrates its remarkable potential to enhance sea surface current reconstruction and recover a substantial portion of the elusive ageostrophic dynamics. Numerical experiments, employing realistic simulations, in a case study area along the Gulf Stream, underscore the efficacy of our proposed approach. These findings support the pivotal role of physics‐informed deep learning in maximizing the utilization of available multimodal observation data sets and numerical simulations to elucidate partially observed sea surface dynamics. Key Points: We present end‐to‐end deep learning schemes to improve the reconstruction of total sea surface currents from satellite‐derived observationsExperiments in a region of the Gulf Stream support the synergistic analysis of sea surface temperature and sea surface height dataThe strain of sea surface dynamics is a proxy of the uncertainty of the retrieved estimation [ABSTRACT FROM AUTHOR]

Published
2024
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8. On Energy Cascades in General Flows: A Lagrangian Application

Author

Jamet, Q., Ajayi, A., Le Sommer, J., Penduff, T., Hogg, Andy, Dewar, William K, Jamet, Q., Ajayi, A., Le Sommer, J., Penduff, T., Hogg, Andy, and Dewar, William K

Abstract

An important characteristic of geophysically turbulent flows is the transfer of energy between scales. Balanced flows pass energy from smaller to larger scales as part of the well-known upscale cascade, while submesoscale and smaller scale flows can transfer energy eventually to smaller, dissipative scales. Much effort has been put into quantifying these transfers, but a complicating factor in realistic settings is that the underlying flows are often strongly spatially heterogeneous and anisotropic. Furthermore, the flows may be embedded in irregularly shaped domains that can be multiply connected. As a result, straightforward approaches like computing Fourier spatial spectra of nonlinear terms suffer from a number of conceptual issues. In this paper, we develop a method to compute cross-scale energy transfers in general settings, allowing for arbitrary flow structure, anisotropy, and inhomogeneity. We employ Green's function approach to the kinetic energy equation to relate kinetic energy at a point to its Lagrangian history. A spatial filtering of the resulting equation naturally decomposes kinetic energy into length-scale-dependent contributions and describes how the transfer of energy between those scalestakes place. The method is applied to a doubly periodic simulation of vortex merger, resulting in the demonstration of the expected upscale energy cascade. Somewhat novel results are that the energy transfers are dominated by pressure work, rather than kinetic energy exchange, and dissipation is a noticeable influence on the larger scale energy budgets. We also describe, but do not employ here, a technique for developing filters to use in complex domains.

Published
2020

12. Reconstruction of the 3-D Dynamics From Surface Variables in a High-Resolution Simulation of North Atlantic

Author

Fresnay, S., Ponte, Aurelien, Le Gentil, Sylvie, Le Sommer, J., Fresnay, S., Ponte, Aurelien, Le Gentil, Sylvie, and Le Sommer, J.

Abstract

Several methods that reconstruct the three-dimensional ocean dynamics from sea level are presented and evaluated in the Gulf Stream region with a 1/60° realistic numerical simulation. The use of sea level is motivated by its better correlation with interior pressure or quasigeostrophic potential vorticity (PV) compared to sea surface temperature and sea surface salinity, and, by its observability via satellite altimetry. The simplest method of reconstruction relies on a linear estimation of pressure at depth from sea level. Another method consists in linearly estimating PV from sea level first and then performing a PV inversion. The last method considered, labeled SQG for surface quasigeostrophy, relies on a PV inversion but assumes no PV anomalies. The first two methods show comparable skill at levels above -800∼m. They moderately outperform SQG which emphasizes the difficulty of estimating interior PV from surface variables. Over the 250-1000∼m depth range, the three methods skillfully reconstruct pressure at wavelengths between 500 and 200 km whereas they exhibit a rapid loss of skill between 200 and 100 km wavelengths. Applicability to a real case scenario and leads for improvements are discussed.

Published
2018
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13. Up to What Extent Can We Characterize Ocean Eddies Using Present-Day Gridded Altimetric Products?

Author

Ministerio de Economía y Competitividad (España), Govern de les Illes Balears, Amores, A., Jordá, Gabriel, Arsouze, T., Le Sommer, J., Ministerio de Economía y Competitividad (España), Govern de les Illes Balears, Amores, A., Jordá, Gabriel, Arsouze, T., and Le Sommer, J.

Abstract

The most common methodology used to detect and characterize mesoscale eddies in the global ocean is to analyze altimetry-based sea-level gridded products with an automatic eddy detection and tracking algorithm. However, a careful look at the location of altimetry tracks shows that their separation is often larger than the Rossby radius of deformation. This implies that gridded products based on the information obtained along track would potentially be unable to characterize the mesoscale variability and, in particular, the eddy field. In this study, we analyze up to what extent sea-level gridded products are able to characterize mesoscale eddies with a special focus on the North Atlantic Ocean and the Mediterranean Sea. In order to perform this task, we have generated synthetic sea level anomaly maps using along-track data extracted from realistic high-resolution ocean model simulations and applying an optimal interpolation procedure. Then, we have used an eddy detection and tracking algorithm to the gridded synthetic product and to the original model outputs and compared the characteristics of the resulting eddy fields. Our results suggest that gridded products largely underestimate the density of eddies, capturing only between 6% and 16% of the total number of eddies. The main reason is that the spatial resolution of the gridded products is not enough to capture the small-scale eddies that are the most abundant. Also, the unresolved structures are aliased into larger structures in the gridded products, so those products show an unrealistic number of large eddies with overestimated amplitudes.

Published
2018

14. NEMO–ICB (v1.0): interactive icebergs in the NEMO ocean model globally configured at eddy-permitting resolution

Author

Marsh, R., Ivchenko, V.O., Skliris, N., Alderson, S., Bigg, G.R., Madec, G., Blaker, A.T., Aksenov, Y., Sinha, B., Coward, A.C., Le Sommer, J., Merino, N., Zalesny, V.B., Marsh, R., Ivchenko, V.O., Skliris, N., Alderson, S., Bigg, G.R., Madec, G., Blaker, A.T., Aksenov, Y., Sinha, B., Coward, A.C., Le Sommer, J., Merino, N., and Zalesny, V.B.

Abstract

An established iceberg module, ICB, is used interactively with the Nucleus for European Modelling of the Ocean (NEMO) ocean model in a new implementation, NEMO–ICB (v1.0). A 30-year hindcast (1976–2005) simulation with an eddy-permitting (0.25°) global configuration of NEMO–ICB is undertaken to evaluate the influence of icebergs on sea ice, hydrography, mixed layer depths (MLDs), and ocean currents, through comparison with a control simulation in which the equivalent iceberg mass flux is applied as coastal runoff, a common forcing in ocean models. In the Southern Hemisphere (SH), drift and melting of icebergs are in balance after around 5 years, whereas the equilibration timescale for the Northern Hemisphere (NH) is 15–20 years. Iceberg drift patterns, and Southern Ocean iceberg mass, compare favourably with available observations. Freshwater forcing due to iceberg melting is most pronounced very locally, in the coastal zone around much of Antarctica, where it often exceeds in magnitude and opposes the negative freshwater fluxes associated with sea ice freezing. However, at most locations in the polar Southern Ocean, the annual-mean freshwater flux due to icebergs, if present, is typically an order of magnitude smaller than the contribution of sea ice melting and precipitation. A notable exception is the southwest Atlantic sector of the Southern Ocean, where iceberg melting reaches around 50% of net precipitation over a large area. Including icebergs in place of coastal runoff, sea ice concentration and thickness are notably decreased at most locations around Antarctica, by up to ~ 20% in the eastern Weddell Sea, with more limited increases, of up to ~ 10% in the Bellingshausen Sea. Antarctic sea ice mass decreases by 2.9%, overall. As a consequence of changes in net freshwater forcing and sea ice, salinity and temperature distributions are also substantially altered. Surface salinity increases by ~ 0.1 psu around much of Antarctica, due to suppressed coastal runoff

Published
2015

15. Anisotropy of eddy variability in the global ocean

Author

Stewart, Kial, Spence, P., Waterman, Stephanie, Le Sommer, J., Molines, J.-M., Lilly, J. M., England, Matthew Heathcote, Stewart, Kial, Spence, P., Waterman, Stephanie, Le Sommer, J., Molines, J.-M., Lilly, J. M., and England, Matthew Heathcote

Abstract

The anisotropy of eddy variability in the global ocean is examined in geostrophic surface velocities derived from satellite observations and in the horizontal velocities of a 1/12° global ocean model. Eddy anisotropy is of oceanographic interest as it is through anisotropic velocity fluctuations that the eddy and mean-flow fields interact dynamically. This study is timely because improved observational estimates of eddy anisotropy will soon be available with Surface Water and Ocean Topography (SWOT) altimetry data. We find there to be good agreement between the characteristics and distributions of eddy anisotropy from the present satellite observations and model ocean surface. In the model, eddy anisotropy is found to have significant vertical structure and is largest close to the ocean bottom, where the anisotropy aligns with the underlying isobaths. The highly anisotropic bottom signal is almost entirely contained in the barotropic variability. Upper-ocean variability is predominantly baroclinic and the alignment is less sensitive to the underlying bathymetry. These findings offer guidance for introducing a parameterization of eddy feedbacks, based on the eddy kinetic energy and underlying bathymetry, to operate on the barotropic flow and better account for the effects of barotropic Reynolds stresses unresolved in coarse-resolution ocean models.

Published
2015

16. DRAKKAR: developing high resolution ocean components for European Earth system models

Author

Barnier, B., Blaker, A. T., Biastoch, Arne, Böning, Claus W., Coward, A., Deshayes, J., Duchez, A., Hirschi, J., Le Sommer, J., Madec, G., Maze, G., Molines, Joan-Marc, New, A., Penduff, T., Scheinert, Markus, Talandier, C., Treguier, A.-M., Barnier, B., Blaker, A. T., Biastoch, Arne, Böning, Claus W., Coward, A., Deshayes, J., Duchez, A., Hirschi, J., Le Sommer, J., Madec, G., Maze, G., Molines, Joan-Marc, New, A., Penduff, T., Scheinert, Markus, Talandier, C., and Treguier, A.-M.

Published
2015

18. NEMO–ICB (v1.0): interactive icebergs in the NEMO ocean model globally configured at eddy-permitting resolution

Author

Marsh, R., primary, Ivchenko, V. O., additional, Skliris, N., additional, Alderson, S., additional, Bigg, G. R., additional, Madec, G., additional, Blaker, A. T., additional, Aksenov, Y., additional, Sinha, B., additional, Coward, A. C., additional, Le Sommer, J., additional, Merino, N., additional, and Zalesny, V. B., additional

Published
2015
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19. Influence of numerical schemes on current-topography interactions in 1/4 degrees global ocean simulations

Author

Penduff, T., Le Sommer, J., Barnier, B., Anne Marie Treguier, Molines, Jm, and Madec, G.

Abstract

The combined use of partial steps and of an energy-enstrophy conserving momentum advection scheme was shown by Barnier et al. (2006) to yield substantial improvements in the surface solution of the DRAKKAR 4 global sea-ice/ocean model. The present study extends this investigation below the surface with a special focus on the Atlantic and reveals many improvements there as well: e.g. more realistic path, structure and transports of major currents (Gulf Stream, North Atlantic Current, Confluence region, Zapiola anticyclone), behavior of shedded rings, narrower subsurface boundary currents, stronger mean and eddy flows (MKE and EKE) at depth, beneficial enhancement of cyclonic (anticyclonic) flows around topographic depressions (mountains). Interestingly, adding a no-slip boundary condition to this improved model setup cancels most of these improvements, bringing back the biases diagnosed without the improved momentum advection scheme and partial steps (these biases are typical of other models at comparable or higher resolutions). This shows that current-topography interactions and full-depth eddy-admitting model solutions can be seriously deteriorated by near-bottom sidewall friction, either explicit or inherent to inadequate numerical schemes.

Published
2007

20. DRAKKAR: developing high resolution ocean components for European Earth system models

Author

Barnier, B., Blaker, A.t., Biatosch, A., Böning, C.w., Coward, A., Deshayes, Julie, Hirshi, J., Le Sommer, J., Madec, G., Maze, Guillaume, Molines, J.m., New, A., Penduff, T., Scheinert, M., Talandier, Claude, Treguier, Anne-marie, Barnier, B., Blaker, A.t., Biatosch, A., Böning, C.w., Coward, A., Deshayes, Julie, Hirshi, J., Le Sommer, J., Madec, G., Maze, Guillaume, Molines, J.m., New, A., Penduff, T., Scheinert, M., Talandier, Claude, and Treguier, Anne-marie

Abstract

DRAKKAR is a consortium of European ocean modelling teams. It was “created to take up the challenges of developing realistic global eddy-resolving/ permitting ocean/sea-ice models, and of building an ensemble of high resolution model hindcasts representing the ocean circulation from the 1960s to present” (quoting the DRAKKAR Group, 2007, in a CLIVAR Exchanges paper where the DRAKKAR strategy was presented for the first time). Now in the second decade of its existence, the DRAKKAR Group is active and thriving, and it is now timely to present recent developments and future plans in this special issue of CLIVAR Exchanges.

Published
2014

21. Meridional transport of salt in the global ocean from an eddy-resolving model

Author

Treguier, A.M., Deshayes, J., Le Sommer, J., Lique, C., Madec, G., Penduff, T., Molines, J.-M., Barnier, B., Bourdalle-Badie, R., Talandier, C., Treguier, A.M., Deshayes, J., Le Sommer, J., Lique, C., Madec, G., Penduff, T., Molines, J.-M., Barnier, B., Bourdalle-Badie, R., and Talandier, C.

Abstract

The meridional transport of salt is computed in a global eddy-resolving numerical model (1/12° resolution) in order to improve our understanding of the ocean salinity budget. A methodology is proposed that allows a global analysis of the salinity balance in relation to surface water fluxes, without defining a "freshwater anomaly" based on an arbitrary reference salinity. The method consists of a decomposition of the meridional transport into (i) the transport by the time–longitude–depth mean velocity, (ii) time–mean velocity recirculations and (iii) transient eddy perturbations. Water is added (rainfall and rivers) or removed (evaporation) at the ocean surface at different latitudes, which creates convergences and divergences of mass transport with maximum and minimum values close to ±1 Sv. The resulting meridional velocity effects a net transport of salt at each latitude (±30 Sv PSU), which is balanced by the time–mean recirculations and by the net effect of eddy salinity–velocity correlations. This balance ensures that the total meridional transport of salt is close to zero, a necessary condition for maintaining a quasi-stationary salinity distribution. Our model confirms that the eddy salt transport cannot be neglected: it is comparable to the transport by the time–mean recirculation (up to 15 Sv PSU) at the poleward and equatorial boundaries of the subtropical gyres. Two different mechanisms are found: eddy contributions are localized in intense currents such as the Kuroshio at the poleward boundary of the subtropical gyres, while they are distributed across the basins at the equatorward boundaries. Closer to the Equator, salinity–velocity correlations are mainly due to the seasonal cycle and large-scale perturbations such as tropical instability waves.

Published
2014

23. Mechanisms maintaining southern ocean meridional heat transport under projected wind forcing

Author

Spence, P, Saenko, OA, Dufour, CO, Le Sommer, J, England, MH, Spence, P, Saenko, OA, Dufour, CO, Le Sommer, J, and England, MH

Abstract

Meridional heat transport (MHT) in the Southern Ocean (SO) and its components are analyzed with two eddy-permitting climate models. The two models present a consistent picture of the MHT response to projected 21st century changes in SO winds. In agreement with recent analysis based on an ocean data synthesis product, much of the MHT in the SO is found to be due to the time-mean fields of meridional velocity and temperature. The change in the net MHT tends to be small relative to the interannual variability at most SO latitudes. However, both models exhibit significant changes at most latitudes south of 30°S in individual components of MHT. A simple framework wherein changes in the eddy and mean heat transports tend to compensate each other is not supported by our results.Instead, the MHT response is composed of sizeable contributions from essentially all of the MHT components, with the eddy and mean heat transports often having the same sign.

Published
2012

24. Structure and causes of the pulsation mode in the Antarctic Circumpolar Current south of Australia

Author

Dufour, CO, Le Sommer, J, Penduff, T, Barnier, B, England, MH, Dufour, CO, Le Sommer, J, Penduff, T, Barnier, B, and England, MH

Abstract

The subsurface variability of potential temperature and salinity south of Australia along 130°E is studied over a 25-yr period (1980–2004). The study is done with fields provided by a global eddy-permitting model of the DRAKKAR project forced by atmospheric reanalysis. The analysis performed by C. Sun and D. R. Watts with in situ hydrographic data is repeated. Sun and Watts have investigated the EOF modes in streamfunction space along the World Ocean Circulation Experiment (WOCE) SR3 section. In particular, they found that an EOF mode, which they called the “pulsation mode,” strongly dominates subsurface thermohaline variations. Here, it is found that, in the model, an EOF mode with spatial structure similar to the Sun and Watts pulsation mode dominates subsurface thermohaline variations in streamfunction space. The mode displays a maximum of variability at the Subantarctic Front (SAF) between Subantarctic Mode Water (SAMW) and Antarctic Intermediate Water (AAIW). The associated time series exhibits an intermittent interseasonal frequency (3–6 months), especially during three periods (1983–84, 1990, and 1994–96). Some energy is also found with a 4-yr period.Further analyses reveal that the pulsation mode can also be observed in physical space. The pulsation mode is found to be related to movements of the SAF constrained by the bathymetry of the Southeast Indian Ridge. The pulsation mode displays many similarities with cold-core eddy events rather than being related to variations of the westerly wind stress, as previously proposed. The impact of those events on SAMW properties remains unclear.

Published
2011

28. Influence of numerical schemes on current-topography interactions in 1/4 degrees global ocean simulations

Author

Penduff, T, Le Sommer, J, Barnier, B, Treguier, Anne-marie, Molines, J, Madec, G, Penduff, T, Le Sommer, J, Barnier, B, Treguier, Anne-marie, Molines, J, and Madec, G

Abstract

The combined use of partial steps and of an energy-enstrophy conserving momentum advection scheme was shown by Barnier et al. (2006) to yield substantial improvements in the surface solution of the DRAKKAR 4 global sea-ice/ocean model. The present study extends this investigation below the surface with a special focus on the Atlantic and reveals many improvements there as well: e.g. more realistic path, structure and transports of major currents (Gulf Stream, North Atlantic Current, Confluence region, Zapiola anticyclone), behavior of shedded rings, narrower subsurface boundary currents, stronger mean and eddy flows (MKE and EKE) at depth, beneficial enhancement of cyclonic (anticyclonic) flows around topographic depressions (mountains). Interestingly, adding a no-slip boundary condition to this improved model setup cancels most of these improvements, bringing back the biases diagnosed without the improved momentum advection scheme and partial steps (these biases are typical of other models at comparable or higher resolutions). This shows that current-topography interactions and full-depth eddy-admitting model solutions can be seriously deteriorated by near-bottom sidewall friction, either explicit or inherent to inadequate numerical schemes.

Published
2007

29. Southern Ocean overturning across streamlines in an eddying simulation of the Antarctic Circumpolar Current

Author

Treguier, Anne-marie, England, M, Rintoul, S, Madec, G, Le Sommer, J, Molines, J, Treguier, Anne-marie, England, M, Rintoul, S, Madec, G, Le Sommer, J, and Molines, J

Abstract

An eddying global model is used to study the characteristics of the Antarctic Circumpolar Current (ACC) in a streamline-following framework. Previous model-based estimates of the meridional circulation were calculated using zonal averages: this method leads to a counter-intuitive pole-ward circulation of the less dense waters, and underestimates the eddy effects. We show that on the contrary, the upper ocean circulation across streamlines agrees with the theoretical view: an equatorward mean flow partially cancelled by a poleward eddy mass flux. Two model simulations, in which the buoyancy forcing above the ACC changes from positive to negative, suggest that the relationship between the residual meridional circulation and the surface buoyancy flux is not as straightforward as assumed by the simplest theoretical models: the sign of the residual circulation cannot be inferred from the surface buoyancy forcing only. Among the other processes that likely play a part in setting the meridional circulation, our model results emphasize the complex three-dimensional structure of the ACC (probably not well accounted for in streamline-averaged, two-dimensional models) and the distinct role of temperature and salinity in the definition of the density field. Heat and salt transports by the time-mean flow are important even across time-mean streamlines. Heat and salt are balanced in the ACC, the model drift being small, but the nonlinearity of the equation of state cannot be ignored in the density balance.

Published
2007

30. Southern Ocean overturning across streamlines in an eddying simulation of the Antarctic Circumpolar Current

Author

Treguier, A.M., England, M.H., Rintoul, S.R., Madec, G., Le Sommer, J., Molines, J-M., Treguier, A.M., England, M.H., Rintoul, S.R., Madec, G., Le Sommer, J., and Molines, J-M.

Abstract

An eddying global model is used to study the characteristics of the Antarctic Circumpolar Current (ACC) in a streamline-following framework. Previous model-based estimates of the meridional circulation were calculated using zonal averages: this method leads to a counter-intuitive poleward circulation of the less dense waters, and underestimates the eddy effects. We show that on the contrary, the upper ocean circulation across streamlines agrees with the theoretical view: an equatorward mean flow partially cancelled by a poleward eddy mass flux. Two model simulations, in which the buoyancy forcing above the ACC changes from positive to negative, suggest that the relationship between the residual meridional circulation and the surface buoyancy flux is not as straightforward as assumed by the simplest theoretical models: the sign of the residual circulation cannot be inferred from the surface buoyancy forcing only. Among the other processes that likely play a part in setting the meridional circulation, our model results emphasize the complex three-dimensional structure of the ACC (probably not well accounted for in streamline-averaged, two-dimensional models) and the distinct role of temperature and salinity in the definition of the density field. Heat and salt transports by the time-mean flow are important even across time-mean streamlines. Heat and salt are balanced in the ACC, the model drift being small, but the nonlinearity of the equation of state cannot be ignored in the density balance.

Published
2007

31. Eddy-Permitting Ocean Circulation Hindcasts of Past Decades

Author

Barnier, B., Brodeau, L., Le Sommer, J., Molines, J.-M., Penduff, T., Theetten, S., Treguier, A.-M., Madec, G., Biastoch, Arne, Böning, Claus W., Dengg, Joachim, Gulev, S., Bourdalle Badie, R., Chanut, J., Garric, G., Alderson, S., Coward, A., de Cuevas, B., New, A., Haines, K., Smith, G., Drijfhout, S., Hazeleger, W., Severijns, C., Myers, P., Barnier, B., Brodeau, L., Le Sommer, J., Molines, J.-M., Penduff, T., Theetten, S., Treguier, A.-M., Madec, G., Biastoch, Arne, Böning, Claus W., Dengg, Joachim, Gulev, S., Bourdalle Badie, R., Chanut, J., Garric, G., Alderson, S., Coward, A., de Cuevas, B., New, A., Haines, K., Smith, G., Drijfhout, S., Hazeleger, W., Severijns, C., and Myers, P.

Published
2007

32. Impact of partial steps and momentum advection schemes in a global ocean circulation model at eddy-permitting resolution

Author

Barnier, B, Madec, G, Penduff, T, Molines, J, Treguier, Anne-marie, Le Sommer, J, Beckmann, A, Biastoch, A, Boning, C, Dengg, J, Derval, C, Durand, E, Gulev, S, Remy, E, Talandier, Claude, Theetten, Sebastien, Maltrud, M, Mcclean, J, De Cuevas, B, Barnier, B, Madec, G, Penduff, T, Molines, J, Treguier, Anne-marie, Le Sommer, J, Beckmann, A, Biastoch, A, Boning, C, Dengg, J, Derval, C, Durand, E, Gulev, S, Remy, E, Talandier, Claude, Theetten, Sebastien, Maltrud, M, Mcclean, J, and De Cuevas, B

Abstract

Series of sensitivity tests were performed with a z-coordinate, global eddy-permitting (1/4 degrees) ocean/sea-ice model (the ORCA-R025 model configuration developed for the DRAKKAR project) to carefully evaluate the impact of recent state-of-the-art numerical schemes on model solutions. The combination of an energy-enstrophy conserving (EEN) scheme for momentum advection with a partial step (PS) representation of the bottom topography yields significant improvements in the mean circulation. Well known biases in the representation of western boundary currents, such as in the Atlantic the detachment of the Gulf Stream, the path of the North Atlantic Current, the location of the Confluence, and the strength of the Zapiola Eddy in the south Atlantic, are partly corrected. Similar improvements are found in the Pacific, Indian, and Southern Oceans, and characteristics of the mean flow are generally much closer to observations. Comparisons with other state-of-the-art models show that the ORCA-R025 configuration generally performs better at similar resolution. In addition, the model solution is often comparable to solutions obtained at 1/6 or 1/10 degrees resolution in some aspects concerning mean flow patterns and distribution of eddy kinetic energy. Although the reasons for these improvements are not analyzed in detail in this paper, evidence is shown that the combination of EEN with PS reduces numerical noise near the bottom, which is likely to affect current-topography interactions in a systematic way. We conclude that significant corrections of the mean biases presently seen in general circulation model solutions at eddy-permitting resolution can still be expected from the development of numerical methods, which represent an alternative to increasing resolution.

Published
2006
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33. Impact of partial steps and momentum advection schemes in a global ocean circulation model at eddy-permitting resolution

Author

Barnier, B., Madec, G., Penduff, T., Molines, J-M., Treguier, A-M., Le Sommer, J., Beckmann, A., Boning, C., Dengg, J., Derval, C., Durand, E., Gulev, S., Remy, E., Talandier, C., Theerren, S., Maltrud, M., McClean, J., de Cuevas, B., Barnier, B., Madec, G., Penduff, T., Molines, J-M., Treguier, A-M., Le Sommer, J., Beckmann, A., Boning, C., Dengg, J., Derval, C., Durand, E., Gulev, S., Remy, E., Talandier, C., Theerren, S., Maltrud, M., McClean, J., and de Cuevas, B.

Abstract

Series of sensitivity tests were performed with az-coordinate, global eddy-permitting (1/4?) ocean/sea-ice model (the ORCA-R025 model configuration developed for the DRAKKAR project) to carefully evaluate the impact of recent state-of-the-art numerical schemes on model solutions. The combination of an energy?enstrophy conserving (EEN) scheme for momentum advection with a partial step (PS) representation of the bottom topography yields significant improvements in the mean circulation. Well known biases in the representation of western boundary currents, such as in the Atlantic the detachment of the Gulf Stream, the path of the North Atlantic Current, the location of the Confluence, and the strength of the Zapiola Eddy in the south Atlantic, are partly corrected. Similar improvements are found in the Pacific, Indian, and Southern Oceans, and characteristics of the mean flow are generally much closer to observations. Comparisons with other state-of-the-art models show that the ORCA-R025 configuration generally performs better at similar resolution. In addition, the model solution is often comparable to solutions obtained at 1/6 or 1/10? resolution in some aspects concerning mean flow patterns and distribution of eddy kinetic energy. Although the reasons for these improvements are not analyzed in detail in this paper, evidence is shown that the combination of EEN with PS reduces numerical noise near the bottom, which is likely to affect current?topography interactions in a systematic way. We conclude that significant corrections of the mean biases presently seen in general circulation model solutions at eddy-permitting resolution can still be expected from the development of numerical methods, which represent an alternative to increasing resolution.

Published
2006

43. Meridional transport of salt in the global ocean from an eddy-resolving model.

Author

Treguier, A. M., Deshayes, J., Le Sommer, J., Lique, C., Madec, G., Penduff, T., Molines, J.-M., Barnier, B., Bourdalle-Badie, R., and Talandier, C.

Subjects
MERIDIONAL winds, OCEANOGRAPHY, FRESHWATER ecology, ECOLOGICAL disturbances, WIND speed, OCEAN currents
Abstract

The meridional transport of salt is computed in a global eddy-resolving numerical model (1/12° resolution) in order to improve our understanding of the ocean salinity budget. A methodology is proposed that allows a global analysis of the salinity balance in re- lation with surface water fluxes, without defining a "freshwater anomaly" based on an arbitrary reference salinity. The method consists in a decomposition of the meridional transport into (i) the transport by the time-longitude-depth mean velocity, (ii) time-mean velocity recirculations and (iii) transient eddy perturbations. Water is added (rainfall) or removed (evaporation) at the ocean surface at different latitudes, which creates convergences and divergences of mass tranport with maximum and minimum values close to ±1 Sv. The resulting meridional velocity effects a net transport of salt at each latitude (±30 Sv PSU), which is balanced by the time-mean recirculations and by the net effect of eddy salinity-velocity correlations. This balance ensures that the total meridional transport of salt is close to zero, a necessary condition to maintain a quasi-stationary salinity distribution. Our model confirms that the eddy salt transport cannot be neglected: it is comparable to the transport by the time-mean recirculation (up to 15 Sv PSU) at the poleward and equatorial boundaries of the subtropical gyres. Two different mechanisms are found: eddy contributions are localized in intense currents such as the Kuroshio at the poleward boundary of the subtropical gyres, while they are distributed across the basins at the equatorward boundaries. Closer to the equator, salinity-velocity correlations are mainly due to the seasonal cycle and large scale perturbations such as tropical instability waves. [ABSTRACT FROM AUTHOR]

Published
2013
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44. Influence of numerical schemes on current-topography interactions in ¼º global ocean simulations.

Author

Penduff, T., Le Sommer, J., Barnier, B., Treguier, A.-M., Molines, J.-M., and Madec, G.

Subjects
SUBMARINE topography, OCEAN, OCEAN waves, OCEAN currents, OCEANOGRAPHY, NUMERICAL analysis
Abstract

The combined use of partial steps and of an energy-enstrophy conserving momentum advection scheme was shown by Barnier et al. (2006) to yield substantial improvements in the surface solution of the DRAKKAR 1/4° global sea-ice/ocean model. The present study extends this investigation below the surface with a special focus on the Atlantic and reveals many improvements there as well: e.g. more realistic path, structure and transports of major currents (Gulf Stream, North Atlantic Current, Confluence region, Zapiola anticyclone), behavior of shedded rings, narrower subsurface boundary currents, stronger mean and eddy flows (MKE and EKE) at depth, beneficial enhancement of cyclonic (anticyclonic) flows around topographic depressions (mountains). Interestingly, adding a no-slip boundary condition to this improved model setup cancels most of these improvements, bringing back the biases diagnosed without the improved momentum advection scheme and partial steps (these biases are typical of other models at comparable or higher resolutions). This shows that current-topography interactions and full-depth eddy-admitting model solutions can be seriously deteriorated by near-bottom sidewall friction, either explicit or inherent to inadequate numerical schemes. [ABSTRACT FROM AUTHOR]

Published
2007
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45. DRAKKAR: developing high resolution ocean components for European Earth system models

Author

Barnier B., Blaker A.T., Biatosch A., Böning C.W., Coward A., Deshayes, Julie, Hirshi J., Le Sommer J., Madec G., Guillaume Maze, Molines J.M., New A., Penduff T., Scheinert M., Talandier, Claude, and Treguier, Anne-Marie

Abstract

DRAKKAR is a consortium of European ocean modelling teams. It was “created to take up the challenges of developing realistic global eddy-resolving/ permitting ocean/sea-ice models, and of building an ensemble of high resolution model hindcasts representing the ocean circulation from the 1960s to present” (quoting the DRAKKAR Group, 2007, in a CLIVAR Exchanges paper where the DRAKKAR strategy was presented for the first time). Now in the second decade of its existence, the DRAKKAR Group is active and thriving, and it is now timely to present recent developments and future plans in this special issue of CLIVAR Exchanges.

46. Altimetry for the future: Building on 25 years of progress

Author

Francesco d'Ovidio, Pierre Féménias, Sean Bruinsma, Felix Perosanz, Jerome Bouffard, S. Desai, Alexandre Couhert, Tatyana V. Belonenko, Sinead L. Farrell, Masafumi Kamachi, Rémi Laxenaire, Alexei V. Kouraev, M-Isabelle Pujol, Sandrine Mulet, Ciprian Spatar, Pablo Nilo Garcia, Loren Carrere, Vinca Rosmorduc, Michel Calzas, Marcello Passaro, Francesca Cirillo, Mathieu Hamon, Enrico Ser-Giacomi, Jida Wang, Raj Kumar, Stelios P. Mertikas, Luisella Giulicchi, Eric Jeansou, Benoit Legresy, Corinne Salaün, Donald Richardson, Martin Horwath, Sujit Basu, Rosemary Morrow, Jean-Damien Desjonquères, François Barlier, Cédric Brachet, Cécile Manfredi, Yves Morel, P. K. Gupta, Nicolas Taburet, Ferran Gibert, Anny Cazenave, Sung Yong Kim, Christopher Pearson, Lin Gilbert, Brian D. Dushaw, Johnny A. Johannessen, René Forsberg, Joël Dorandeu, Luciana Fenoglio, Denis Blumstein, C. K. Shum, Debadatta Swain, Stephan Paul, Valerii Vuglinskii, Marco Meloni, Hilary Wilson, Laurent Testut, Sebatian B. Simonsen, John Moyard, Fabien Léger, Andy Shaw, Abdolnabi Abdeh Kolahchi, Andrea Scozzari, Jan Even Øie Nilsen, Anna I. Bulczak, Valerio Poggiali, Rashmi Shah, John Wilkin, Steven Baker, Patrice Klein, Touati Benkouider, Claire Macintosh, Sarah T. Gille, Alexandre Guerin, Gilles Tavernier, Josh K. Willis, Jérôme Benveniste, Cedric Tourain, Emil V. Stanev, Praveen K. Thakur, Lionel Fichen, Céline Tison, Hans Ngodock, Shenfu Dong, Yuanyuan Jia, Sergey A. Lebedev, Nadia Ayoub, Constantin Mavrocordatos, Cédric H. David, Salvatore Dinardo, Yongjun Jia, Berguzar Oztunali Ozbahceci, Sara Fleury, Matthias Raynal, Yannice Faugère, Kathryn A. Kelly, Christian Schwatke, Craig Donlon, Etienne Poirier, Margaret Srinivasan, Remko Scharroo, Helena Antich, Barbara J. Ryan, Sergey V. Prants, Malcolm McMillan, Frédérique Rémy, David T. Sandwell, Annick Sylvestre-baron, Pascal Bonnefond, Fabien Blarel, Mounir Benkiran, Remi Tailleux, Marco Restano, Thierry Guinle, Stefano Vignudelli, Eric Leuliette, Madeleine Cahill, Ali Rami, Saulo Soares, Sophie Le Gac, Bàrbara Barceló-Llull, Claudia C. Carabajal, Veit Helm, Eva Alou-Font, Alejandro Blazquez, David Griffin, Habib B. Dieng, Prakash Chauhan, Albert Garcia-Mondejar, Christian Massari, Christopher J. Banks, Joana Fernandes, Blake A Walter, Nathalie Steunou, Karina Nielsen, Elena Zakharova, Bob Su, Stefania Camici, Frédérique Seyler, Fukai Peng, Denis L. Volkov, Wim Simons, Pieter Visser, Sophie Coutin-Faye, Lionel Gourdeau, Jesús Gómez-Enri, Andreas Schiller, Brian K. Arbic, Svetlana Karimova, Christine Gommenginger, Fanny Piras, Angélique Melet, Steve Coss, Meric Srokosz, Robert G. King, Frédéric Frappart, Fernando S. Paolo, Anna Klos, José Darrozes, Shannon Brown, Loreley Selene Lago, Susheel Adusumilli, Jay F. Shriver, Yves Quilfen, Martina Idžanović, Bernd Uebbing, Daniel Medeiros Moreira, Byron D. Tapley, R. Keith Raney, Frank G. Lemoine, Angelica Tarpanelli, Lara Díaz-Barroso, Jean-François Crétaux, Jean Tournadre, Tamlin M. Pavelsky, Sébastien Trilles, Carolina Nogueira Loddo, Léa Lasson, Stine Kildegaard Rose, Luc Lenain, Philip L. Woodworth, Marie-laure Frery, Saleh Abdalla, Bo Qiu, Stefan Hendricks, Mikhail A. Sokolovskiy, Antonio Sánchez-Román, Martin G. Scharffenberg, Per Knudsen, Andrew Shepherd, Michiel Otten, Sammie Buzzard, Philippe Schaeffer, Nicolas Picot, Luca Brocca, Michel Tsamados, Danielle De Staerke, Frederic Vivier, Nicole Bellefond, Jean-François Minster, Telmo Vieira, Brian D. Beckley, Stylianos Flampouris, Nadya Vinogradova Shiffer, Sergei Rudenko, Camille Noûs, Sabine Arnault, Frédéric Cyr, Liguang Jiang, Nicolas Bercher, Teresa K. Chereskin, Katsumi Takayama, Julienne Stroeve, Andrea Doglioli, Joanna Staneva, Stéphane Calmant, T. Moreau, Julien Le Sommer, David R. Donahue, Nadim Dayoub, Clement Ubelmann, Annie Richardson, Estelle Obligis, Laurent Brodeau, Catherine Prigent, Gérald Dibarboure, Simón Ruiz, LuAnne Thompson, Muriel Berge-Nguyen, Martina Ricko, Hugues Capdeville, Sammy Metref, Roshin P. Raj, Suchandra Aich Bhowmick, Andrey G. Kostianoy, Guillermina Paniagua, Mathilde Cancet, Eero Rinne, Sonia Ponce de León, Cédric Falco, Jianqiang Liu, Lucile Gaultier, Julia Gaudelli, Thierry Medina, Vadim Zinchenko, William Llovel, Eric P. Chassignet, Raymond Zaharia, Svetlana Y. Erofeeva, Lifeng Bao, Ole Baltazar Andersen, Emmanuel Cosme, Anna E. Hogg, Yohanes Budi Sulistioadi, Artur Gil, O. Laurain, Walter H. F. Smith, Ngan Tran, Pierre-Yves Le Traon, Laura Gomez-Navarro, Adrien Paris, Thomas W. K. Armitage, Alejandro Egido, Christopher Watson, João H. Bettencourt, Giuseppe Aulicino, Philippe Escudier, Fangfang Yao, Marco Fornari, Guoqi Han, Florent Lyard, Elisabeth Remy, Lotfi Aouf, Michele Scagliola, Martin Saraceno, Paolo Filippucci, Chao Wang, Zhongxiang Zhao, Juliette Lambin, Evan Mason, Ines Otosaka, Daniele Ciani, Raúl A. Guerrero, Ralf Bennartz, Michael Ablain, Fabrice Hernandez, Xiaoli Deng, John Lillibridge, Oscar Vergara, Marina Levy, Christine Drezen, Pierre Thibaut, Ronan Fablet, Bill Townsend, David Cotton, Sabrina Speich, Clara Lázaro, R. S. Nerem, Danièle Hauser, Pierre Exertier, Yuri Cotroneo, Henryk Dobslaw, Alessandro Di Bella, Karina von Schuckmann, Saskia Esselborn, Benjamin D. Gutknecht, Cecile Marie Margaretha Kittel, Rolf Koenig, Peter Bauer-Gottwein, Franck Borde, Alexander Braun, Christine Provost, Thomas Slater, Laiba Amarouche, Nikolai Maximenko, Raphael Schneider, Victor Zlotnicki, Jacques Verron, Sergei I. Badulin, Andreas Groh, Denise Dettmering, Mark R. Drinkwater, S. Cherchali, Marc Naeije, Fernando Niño, Alessio Domeneghetti, Kuo Hsin Tseng, François Boy, Rashmi Sharma, Laurent Soudarin, Peter A. E. M. Janssen, Robert Ricker, Frédéric Marin, Ananda Pascual, Eduard Makhoul Varona, Yongsheng Zhang, Pierrik Vuilleumier, Louise Sandberg Sørensen, Guillaume Dodet, Pascale Ferrage, Ramiro Ferrari, Yves Du Penhoat, Rodrigo Cauduro Dias de Paiva, S. Labroue, Camila Indira Artana, Joaquín Tintoré, David Brockley, Thierry Penduff, Paolo Cipollini, Augusto Getirana, Cecile Cheymol, Edward D. Zaron, Silvia Barbetta, Pierre Brasseur, Benoit Meyssignac, Matthias Becker, Kehan Yang, Juan Gabriel Fernández, Jean Paul Boy, European Centre for Medium-Range Weather Forecasts (ECMWF), Soil Conservation and Watershed Management Research Institute (SCWRMI), Agricultural Research, Education and Extension Organisation (AREEO ), Scripps Institution of Oceanography (SIO), University of California [San Diego] (UC San Diego), University of California-University of California, Space Applications Centre [Ahmedabad] (SAC), Indian Space Research Organisation (ISRO), Collecte Localisation Satellites (CLS), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Centre National d'Études Spatiales [Toulouse] (CNES), National Space Institute [Lyngby] (DTU Space), Technical University of Denmark [Lyngby] (DTU), Institut Mediterrani d'Estudis Avancats (IMEDEA), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC)-Universidad de las Islas Baleares (UIB), Météo France, Department of Earth and Environmental Sciences [Ann Arbor], University of Michigan [Ann Arbor], University of Michigan System-University of Michigan System, Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Variabilité de l'Océan et de la Glace de mer (VOG), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Institut de Recherche pour le Développement (IRD)-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Institut de Recherche pour le Développement (IRD)-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU), Mercator Océan, Société Civile CNRS Ifremer IRD Météo-France SHOM, Universita degli studi di Napoli 'Parthenope' [Napoli], Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), P.P. Shirshov Institute of Oceanology (SIO), Russian Academy of Sciences [Moscow] (RAS), Department of Space and Climate Physics [UCL London], Mullard Space Science Laboratory (MSSL), University College of London [London] (UCL)-University College of London [London] (UCL), National Oceanography Centre (NOC), Institute of Geodesy and Geophysics [Wuhan], Chinese Academy of Sciences [Wuhan Branch], Istituto di Ricerca per la Protezione Idrogeologica [Perugia] (IRPI), Consiglio Nazionale delle Ricerche [Roma] (CNR), Géoazur (GEOAZUR 7329), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud]), DTU Environment, Department of Environmental Engineering, Technische Universität Darmstadt (TU Darmstadt), Centre National d'Études Spatiales [Toulouse] (CNES), St Petersburg State University (SPbU), Agence Spatiale Algérienne = Algerian Space Agency (ASAL), Vanderbilt University [Nashville], European Space Research Institute (ESRIN), European Space Agency (ESA), Centre for Marine Technology and Ocean Engineering (CENTEC), Instituto Superior Técnico, Universidade Técnica de Lisboa (IST), Systèmes de Référence Temps Espace (SYRTE), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), European Space Research and Technology Centre (ESTEC), Ecole et Observatoire des Sciences de la Terre (EOST), Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), INSU Division Technique de l'INSU [Site de Brest], Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Queen's University [Kingston, Canada], OceanNext, Géosciences Environnement Toulouse (GET), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Institute of Oceanology, Polish Academy of Sciences (IO-PAN), Polska Akademia Nauk = Polish Academy of Sciences (PAN), Centre for Polar Observation and Modelling (CPOM), Natural Environment Research Council (NERC), Australian Institute of Marine Science [Townsville] (AIMS Townsville), Australian Institute of Marine Science (AIMS), NOVELTIS [Sté], Science Systems and Applications, Inc. [Hampton] (SSAI), International Space Science Institute [Bern] (ISSI), Center for Ocean-Atmospheric Prediction Studies (COAPS), Florida State University [Tallahassee] (FSU), Indian Institute of Remote Sensing (IIRS), Istituto di Science Marine (ISMAR ), Consiglio Nazionale delle Ricerche (CNR), European Centre for Space Applications and Telecommunications (ECSAT), Airbus Group [Germany], Airbus [France], School of Earth Sciences [Columbus], Ohio State University [Columbus] (OSU), Satellite Oceanographic Consultants Ltd (SATOC), Northwest Atlantic Fisheries Centre (NWAFC), Fisheries and Oceans Canada (DFO), Processus et interactions de fine échelle océanique (PROTEO), School of Engineering [Callaghan], University of Newcastle [Australia] (UoN), Deutsches Geodätisches Forschungsinstitut (DGFI-TUM), Technische Universität Munchen - Université Technique de Munich [Munich, Allemagne] (TUM), SOCIB Balearic Islands Coastal Ocean Observing and Forecasting System, German Research Centre for Geosciences - Helmholtz-Centre Potsdam (GFZ), Laboratoire d'Océanographie Physique et Spatiale (LOPS), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Institut méditerranéen d'océanologie (MIO), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Toulon (UTLN)-Centre National de la Recherche Scientifique (CNRS), Department of Civil Chemical Environmental and Materials Engineering [Bologna] (DICAM), University of Bologna, NOAA Office of Satellite and Product Operations (OSPO), NOAA National Environmental Satellite, Data, and Information Service (NESDIS), National Oceanic and Atmospheric Administration (NOAA)-National Oceanic and Atmospheric Administration (NOAA), NOAA Atlantic Oceanographic and Meteorological Laboratory (AOML), National Oceanic and Atmospheric Administration (NOAA), Oregon State University (OSU), IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT), Département Mathematical and Electrical Engineering (IMT Atlantique - MEE), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT), Equipe Observations Signal & Environnement (Lab-STICC_OSE), Laboratoire des sciences et techniques de l'information, de la communication et de la connaissance (Lab-STICC), École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS)-Université Bretagne Loire (UBL)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS)-Université Bretagne Loire (UBL)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Université de Perpignan Via Domitia (UPVD), Department of Geographical Sciences [College Park], University of Maryland [College Park], University of Maryland System-University of Maryland System, Institut für Geodäsie und Geoinformationstechnik, Technische Universität Berlin (TU), Interdisciplinary Centre of Marine and Environmental Research [Matosinhos, Portugal] (CIIMAR), Universidade do Porto, Centro de Investigaciones del Mar y la Atmósfera (CIMA), Facultad de Ciencias Exactas y Naturales [Buenos Aires] (FCEyN), Universidad de Buenos Aires [Buenos Aires] (UBA)-Universidad de Buenos Aires [Buenos Aires] (UBA)-Consejo Nacional de Investigaciones Científicas y Técnicas [Buenos Aires] (CONICET), Institut für Planetare Geodäsie, Lohrmann-Observatorium, Technische Universität Dresden = Dresden University of Technology (TU Dresden), Universidad Nacional de Mar del Plata [Mar del Plata] (UNMdP), SPACE - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Environmental Fluid Mechanics Laboratory [Daejeon] (EFML), Korea Advanced Institute of Science and Technology (KAIST), Ecole Normale Supérieure Paris-Saclay (ENS Paris Saclay), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA (UMR_8112)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-CY Cergy Paris Université (CY), Austral, Boréal et Carbone (ABC), Kansas State University, University of North Carolina [Chapel Hill] (UNC), University of North Carolina System (UNC), University of Tasmania [Hobart, Australia] (UTAS), Rutgers, The State University of New Jersey [New Brunswick] (RU), Rutgers University System (Rutgers), Institute of Arctic and Alpine Research (INSTAAR), University of Colorado [Boulder], Water Problems Institute (WPI), the Russian Academy of Sciences [Moscow, Russia] (RAS), Portland State University [Portland] (PSU), Applied Physics Laboratory [Seattle] (APL-UW), University of Washington [Seattle], Scripps Institution of Oceanography (SIO - UC San Diego), University of California (UC)-University of California (UC), Danmarks Tekniske Universitet = Technical University of Denmark (DTU), Météo-France Direction Interrégionale Sud-Est (DIRSE), Météo-France, Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Università degli Studi di Napoli 'Parthenope' = University of Naples (PARTHENOPE), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), National Research Council of Italy | Consiglio Nazionale delle Ricerche (CNR), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud]), Technische Universität Darmstadt - Technical University of Darmstadt (TU Darmstadt), Agence Spatiale Européenne = European Space Agency (ESA), University of Newcastle [Callaghan, Australia] (UoN), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), University of Bologna/Università di Bologna, IMT Atlantique (IMT Atlantique), École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS)-Université Bretagne Loire (UBL)-IMT Atlantique (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS)-Université Bretagne Loire (UBL)-IMT Atlantique (IMT Atlantique), Technical University of Berlin / Technische Universität Berlin (TU), Universidade do Porto = University of Porto, Consejo Nacional de Investigaciones Científicas y Técnicas [Buenos Aires] (CONICET)-Facultad de Ciencias Exactas y Naturales [Buenos Aires] (FCEyN), Universidad de Buenos Aires [Buenos Aires] (UBA)-Universidad de Buenos Aires [Buenos Aires] (UBA), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique et Atmosphères = Laboratory for Studies of Radiation and Matter in Astrophysics and Atmospheres (LERMA), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-CY Cergy Paris Université (CY), Group on Earth Observations (GEO), Institute of Arctic Alpine Research [University of Colorado Boulder] (INSTAAR), Department of Water Resources, UT-I-ITC-WCC, Faculty of Geo-Information Science and Earth Observation, Abdalla S., Abdeh Kolahchi A., Ablain M., Adusumilli S., Aich Bhowmick S., Alou-Font E., Amarouche L., Andersen O.B., Antich H., Aouf L., Arbic B., Armitage T., Arnault S., Artana C., Aulicino G., Ayoub N., Badulin S., Baker S., Banks C., Bao L., Barbetta S., Barcelo-Llull B., Barlier F., Basu S., Bauer-Gottwein P., Becker M., Beckley B., Bellefond N., Belonenko T., Benkiran M., Benkouider T., Bennartz R., Benveniste J., Bercher N., Berge-Nguyen M., Bettencourt J., Blarel F., Blazquez A., Blumstein D., Bonnefond P., Borde F., Bouffard J., Boy F., Boy J.-P., Brachet C., Brasseur P., Braun A., Brocca L., Brockley D., Brodeau L., Brown S., Bruinsma S., Bulczak A., Buzzard S., Cahill M., Calmant S., Calzas M., Camici S., Cancet M., Capdeville H., Carabajal C.C., Carrere L., Cazenave A., Chassignet E.P., Chauhan P., Cherchali S., Chereskin T., Cheymol C., Ciani D., Cipollini P., Cirillo F., Cosme E., Coss S., Cotroneo Y., Cotton D., Couhert A., Coutin-Faye S., Cretaux J.-F., Cyr F., d'Ovidio F., Darrozes J., David C., Dayoub N., De Staerke D., Deng X., Desai S., Desjonqueres J.-D., Dettmering D., Di Bella A., Diaz-Barroso L., Dibarboure G., Dieng H.B., Dinardo S., Dobslaw H., Dodet G., Doglioli A., Domeneghetti A., Donahue D., Dong S., Donlon C., Dorandeu J., Drezen C., Drinkwater M., Du Penhoat Y., Dushaw B., Egido A., Erofeeva S., Escudier P., Esselborn S., Exertier P., Fablet R., Falco C., Farrell S.L., Faugere Y., Femenias P., Fenoglio L., Fernandes J., Fernandez J.G., Ferrage P., Ferrari R., Fichen L., Filippucci P., Flampouris S., Fleury S., Fornari M., Forsberg R., Frappart F., Frery M.-L., Garcia P., Garcia-Mondejar A., Gaudelli J., Gaultier L., Getirana A., Gibert F., Gil A., Gilbert L., Gille S., Giulicchi L., Gomez-Enri J., Gomez-Navarro L., Gommenginger C., Gourdeau L., Griffin D., Groh A., Guerin A., Guerrero R., Guinle T., Gupta P., Gutknecht B.D., Hamon M., Han G., Hauser D., Helm V., Hendricks S., Hernandez F., Hogg A., Horwath M., Idzanovic M., Janssen P., Jeansou E., Jia Y., Jiang L., Johannessen J.A., Kamachi M., Karimova S., Kelly K., Kim S.Y., King R., Kittel C.M.M., Klein P., Klos A., Knudsen P., Koenig R., Kostianoy A., Kouraev A., Kumar R., Labroue S., Lago L.S., Lambin J., Lasson L., Laurain O., Laxenaire R., Lazaro C., Le Gac S., Le Sommer J., Le Traon P.-Y., Lebedev S., Leger F., Legresy B., Lemoine F., Lenain L., Leuliette E., Levy M., Lillibridge J., Liu J., Llovel W., Lyard F., Macintosh C., Makhoul Varona E., Manfredi C., Marin F., Mason E., Massari C., Mavrocordatos C., Maximenko N., McMillan M., Medina T., Melet A., Meloni M., Mertikas S., Metref S., Meyssignac B., Minster J.-F., Moreau T., Moreira D., Morel Y., Morrow R., Moyard J., Mulet S., Naeije M., Nerem R.S., Ngodock H., Nielsen K., Nilsen J.E.O., Nino F., Nogueira Loddo C., Nous C., Obligis E., Otosaka I., Otten M., Oztunali Ozbahceci B., P. Raj R., Paiva R., Paniagua G., Paolo F., Paris A., Pascual A., Passaro M., Paul S., Pavelsky T., Pearson C., Penduff T., Peng F., Perosanz F., Picot N., Piras F., Poggiali V., Poirier E., Ponce de Leon S., Prants S., Prigent C., Provost C., Pujol M.-I., Qiu B., Quilfen Y., Rami A., Raney R.K., Raynal M., Remy E., Remy F., Restano M., Richardson A., Richardson D., Ricker R., Ricko M., Rinne E., Rose S.K., Rosmorduc V., Rudenko S., Ruiz S., Ryan B.J., Salaun C., Sanchez-Roman A., Sandberg Sorensen L., Sandwell D., Saraceno M., Scagliola M., Schaeffer P., Scharffenberg M.G., Scharroo R., Schiller A., Schneider R., Schwatke C., Scozzari A., Ser-giacomi E., Seyler F., Shah R., Sharma R., Shaw A., Shepherd A., Shriver J., Shum C.K., Simons W., Simonsen S.B., Slater T., Smith W., Soares S., Sokolovskiy M., Soudarin L., Spatar C., Speich S., Srinivasan M., Srokosz M., Stanev E., Staneva J., Steunou N., Stroeve J., Su B., Sulistioadi Y.B., Swain D., Sylvestre-baron A., Taburet N., Tailleux R., Takayama K., Tapley B., Tarpanelli A., Tavernier G., Testut L., Thakur P.K., Thibaut P., Thompson L., Tintore J., Tison C., Tourain C., Tournadre J., Townsend B., Tran N., Trilles S., Tsamados M., Tseng K.-H., Ubelmann C., Uebbing B., Vergara O., Verron J., Vieira T., Vignudelli S., Vinogradova Shiffer N., Visser P., Vivier F., Volkov D., von Schuckmann K., Vuglinskii V., Vuilleumier P., Walter B., Wang J., Wang C., Watson C., Wilkin J., Willis J., Wilson H., Woodworth P., Yang K., Yao F., Zaharia R., Zakharova E., Zaron E.D., Zhang Y., Zhao Z., Zinchenko V., Zlotnicki V., Technical University of Munich (TUM), European Space Agency, National Aeronautics and Space Administration (US), Centre National D'Etudes Spatiales (France), Laboratoire des Écoulements Géophysiques et Industriels [Grenoble] (LEGI), Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Recherche pour le Développement (IRD)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA), Sorbonne Université (SU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Sorbonne Université (SU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Lab-STICC_IMTA_CID_TOMS, Université de Brest (UBO)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Université Bretagne Loire (UBL)-Centre National de la Recherche Scientifique (CNRS)-Université de Bretagne Sud (UBS)-École Nationale d'Ingénieurs de Brest (ENIB)-Université de Brest (UBO)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Université Bretagne Loire (UBL)-Centre National de la Recherche Scientifique (CNRS)-Université de Bretagne Sud (UBS)-École Nationale d'Ingénieurs de Brest (ENIB), Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)

Subjects
Cryospheric science, Atmospheric Science, Earth observation, 010504 meteorology & atmospheric sciences, UT-Hybrid-D, Oceanography, 01 natural sciences, Cryospheric sciences, SDG 13 - Climate Action, Aerospace & Aeronautics, Cryosphere, Satellite altimetry, 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, Geodetic datum, ddc, Ocean surface topography, Geophysics, Section (archaeology), [SDE]Environmental Sciences, Astronomical and Space Sciences, Geology, Altimetria espacial, Coastal oceanography, Meteorology, Hidrologia, Aerospace Engineering, ITC-HYBRID, 0103 physical sciences, Geoid, Oceonografia, Sea level, SDG 14 - Life Below Water, 14. Life underwater, Altimeter, Criosfera, Life Below Water, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, 0105 earth and related environmental sciences, Mechanical Engineering, Hydrology, Astronomy and Astrophysics, Climate Action, Earth system science, [SDU]Sciences of the Universe [physics], 13. Climate action, Space and Planetary Science, ITC-ISI-JOURNAL-ARTICLE, General Earth and Planetary Sciences
Abstract

International Altimetry Team., In 2018 we celebrated 25 years of development of radar altimetry, and the progress achieved by this methodology in the fields of global and coastal oceanography, hydrology, geodesy and cryospheric sciences. Many symbolic major events have celebrated these developments, e.g., in Venice, Italy, the 15th (2006) and 20th (2012) years of progress and more recently, in 2018, in Ponta Delgada, Portugal, 25 Years of Progress in Radar Altimetry. On this latter occasion it was decided to collect contributions of scientists, engineers and managers involved in the worldwide altimetry community to depict the state of altimetry and propose recommendations for the altimetry of the future. This paper summarizes contributions and recommendations that were collected and provides guidance for future mission design, research activities, and sustainable operational radar altimetry data exploitation. Recommendations provided are fundamental for optimizing further scientific and operational advances of oceanographic observations by altimetry, including requirements for spatial and temporal resolution of altimetric measurements, their accuracy and continuity. There are also new challenges and new openings mentioned in the paper that are particularly crucial for observations at higher latitudes, for coastal oceanography, for cryospheric studies and for hydrology. The paper starts with a general introduction followed by a section on Earth System Science including Ocean Dynamics, Sea Level, the Coastal Ocean, Hydrology, the Cryosphere and Polar Oceans and the “Green” Ocean, extending the frontier from biogeochemistry to marine ecology. Applications are described in a subsequent section, which covers Operational Oceanography, Weather, Hurricane Wave and Wind Forecasting, Climate projection. Instruments’ development and satellite missions’ evolutions are described in a fourth section. A fifth section covers the key observations that altimeters provide and their potential complements, from other Earth observation measurements to in situ data. Section 6 identifies the data and methods and provides some accuracy and resolution requirements for the wet tropospheric correction, the orbit and other geodetic requirements, the Mean Sea Surface, Geoid and Mean Dynamic Topography, Calibration and Validation, data accuracy, data access and handling (including the DUACS system). Section 7 brings a transversal view on scales, integration, artificial intelligence, and capacity building (education and training). Section 8 reviews the programmatic issues followed by a conclusion., At the forefront of this support, we must obviously mention the space agencies CNES, ESA and NASA which have played and still play a decisive role in the development and launch of several prominent altimetry missions from the outset. Other agencies such as DLR, EUMETSAT, ISRO, NOAA, NSOAS and organizations such as CMEMS, also contribute significantly to developments in all forms of altimetry.

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47. Effects of methylphenidate on mismatch negativity and P3a amplitude of initially psychostimulant-naïve, adult ADHD patients.

Author

le Sommer J, Low AM, Møllegaard Jepsen JR, Fagerlund B, Vangkilde S, Habekost T, Glenthøj B, and Oranje B

Subjects
Humans, Adult, Electroencephalography methods, Cognition, Methylphenidate pharmacology, Methylphenidate therapeutic use, Attention Deficit Disorder with Hyperactivity drug therapy
Abstract

Background: Deficient information processing in ADHD theoretically results in sensory overload and may underlie the symptoms of the disorder. Mismatch negativity (MMN) and P3a amplitude reflect an individual's detection and subsequent change in attention to stimulus change in their environment. Our primary aim was to explore MMN and P3a amplitude in adult ADHD patients and to examine the effects of methylphenidate (MPH) on these measures., Methods: Forty initially psychostimulant-naïve, adult ADHD patients without comorbid ASD and 42 matched healthy controls (HC) were assessed with an MMN paradigm at baseline. Both groups were retested after 6 weeks, in which patients were treated with MPH., Results: Neither significant group differences in MMN nor P3a amplitude were found at baseline. Although 6-week MPH treatment significantly reduced symptomatology and improved daily functioning of the patients, it did not significantly affect MMN amplitude; however, it did significantly reduce P3a amplitude compared to the HC. Furthermore, more severe ADHD symptoms were significantly associated with larger MMN amplitudes in the patients, both at baseline and follow-up., Conclusion: We found no evidence for early information processing deficits in patients with ADHD, as measured with MMN and P3a amplitude. Six-week treatment with MPH decreased P3a but not MMN amplitude, although more severe ADHD-symptoms were associated with larger MMN amplitudes in the patients. Given that P3a amplitude represents an important attentional process and that glutamate has been linked to both ADHD and MMN amplitude, future research should investigate augmenting MPH treatment of less responsive adults with ADHD with glutamatergic antagonists.

Published
2023
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48. Effects of methylphenidate on subjective sleep parameters in adults with ADHD: a prospective, non-randomized, non-blinded 6-week trial.

Author

Low AM, Vangkilde S, le Sommer J, Fagerlund B, Glenthøj B, Jepsen JRM, and Habekost T

Subjects
Adult, Humans, Follow-Up Studies, Prospective Studies, Sleep, Treatment Outcome, Attention Deficit Disorder with Hyperactivity drug therapy, Central Nervous System Stimulants adverse effects, Methylphenidate adverse effects, Sleep Wake Disorders drug therapy
Abstract

Objective: Methylphenidate is a first-line treatment for ADHD; its contribution to sleep problems in adult ADHD is currently unclear. This study investigates (a) subjective sleep disturbances in a group of initially stimulant medication-naïve adults with ADHD and (b) reported changes in sleep problems after 6 weeks of methylphenidate treatment., Method: A prospective, non-randomized, non-blinded, 6-week follow-up study utilising a self-report measure., Results: We found (1) a large difference in reported sleep quality between methylphenidate medication-naïve patients and controls at baseline, (2) a marked improvement in patients after methylphenidate medication, and (3) largest improvement for patients with the poorest reported sleep at baseline., Conclusion: The study indicates that treatment with methylphenidate increases subjective sleep quality for at least some adults with ADHD.

Published
2023
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49. Visual attention in adults with attention-deficit/hyperactivity disorder before and after stimulant treatment.

Author

Low AM, Vangkilde S, le Sommer J, Fagerlund B, Glenthøj B, Jepsen JRM, Bundesen C, Petersen A, and Habekost T

Subjects
Adult, Cognition, Denmark, Female, Humans, Male, Memory, Short-Term, Neuropsychological Tests, Prospective Studies, Reaction Time, Young Adult, Attention, Attention Deficit Disorder with Hyperactivity drug therapy, Attention Deficit Disorder with Hyperactivity psychology, Central Nervous System Stimulants therapeutic use, Methylphenidate therapeutic use
Abstract

Background: Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder which frequently persists into adulthood. The primary goal of the current study was to (a) investigate attentional functions of stimulant medication-naïve adults with ADHD, and (b) investigate the effects of 6 weeks of methylphenidate treatment on these functions., Methods: The study was a prospective, non-randomized, non-blinded, 6-week follow-up design with 42 stimulant medication-naïve adult patients with ADHD, and 42 age and parental education-matched healthy controls. Assessments included measures of visual attention, based on Bundesen's Theory of Visual Attention (TVA), which yields five precise measures of aspects of visual attention; general psychopathology; ADHD symptoms; dyslexia screening; and estimates of IQ., Results: At baseline, significant differences were found between patients and controls on three attentional parameters: visual short-term memory capacity, threshold of conscious perception, and to a lesser extent visual processing speed. Secondary analyses revealed no significant correlations between TVA parameter estimates and severity of ADHD symptomatology. At follow-up, significant improvements were found specifically for visual processing speed; this improvement had a large effect size, and remained when controlling for re-test effects, IQ, and dyslexia screen performance. There were no significant correlations between changes in visual processing speed and changes in ADHD symptomatology., Conclusions: ADHD in adults may be associated with deficits in three distinct aspects of visual attention. Improvements after 6 weeks of medication are seen specifically in visual processing speed, which could represent an improvement in alertness. Clinical symptoms and visual attentional deficits may represent separate aspects of ADHD in adults.

Published
2019
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50. Delay Aversion and Executive Functioning in Adults With Attention-Deficit/Hyperactivity Disorder: Before and After Stimulant Treatment.

Author

Low AM, le Sommer J, Vangkilde S, Fagerlund B, Glenthøj B, Sonuga-Barke E, Habekost T, and Jepsen JRM

Subjects
Adult, Cognition, Female, Follow-Up Studies, Humans, Male, Neuropsychological Tests, Patient Education as Topic, Prospective Studies, Psychiatric Status Rating Scales, Self Report, Treatment Outcome, Attention Deficit Disorder with Hyperactivity drug therapy, Attention Deficit Disorder with Hyperactivity psychology, Central Nervous System Stimulants therapeutic use, Executive Function, Methylphenidate therapeutic use, Motivation
Abstract

Background: Attention deficit hyperactivity disorder is a heterogeneous disorder, associated with deficits in motivation (e.g., delay aversion) and cognition. Methylphenidate is recommended as a first line treatment for attention deficit hyperactivity disorder symptoms, but little is known about its nonacute effects on motivational and cognitive deficits, particularly in adults with attention deficit hyperactivity disorder., Methods: We utilized a prospective, non-randomized, non-blinded, 6-week follow-up design with 42 initially stimulant medication-naïve adult patients with moderate to severe attention deficit hyperactivity disorder, and 42 age- and parental education-matched healthy controls. Delay aversion and executive functioning were assessed with 2 questionnaires and 5 performance-based tests., Results: At baseline, patients and controls differed significantly on performance-based measures (moderate to large effect sizes), and self-report of delay aversion and executive functioning (very large effect sizes). Treatment with methylphenidate medication (mean dose 65.54 mg/d, SD=10.39) was not associated with improvements in performance-based measures of delay aversion and executive functioning compared to controls, although improvements in self-report executive functioning and delay aversion were found. Self-reported delay aversion was most consistently associated with ADHD symptomatology at baseline and after medication., Conclusion: Methylphenidate treatment does not have an effect on performance-based measures of delay aversion and executive functioning, but may have significant effects on self-reported delay aversion and executive functioning. The latter finding should be interpreted cautiously, given the subjective nature of these measures and design limitations. Self-reported delay aversion is most consistently associated with attention deficit hyperactivity disorder symptomatology.

Published
2018
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