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Observing System Simulation Experiments (OSSEs) with the Mercator Ocean/Copernicus Marine global 1/12° data assimilation system has been carried out to compare and quantify the expected performance of two high resolution altimetry mission concepts envisioned for the long-term evolution (post-2032) of the Copernicus Sentinel-3 topography mission. The two mission concepts are a constellation of two wide-swath altimeters and a constellation of 12 nadir altimeters. These two configurations greatly improve ocean forecasting and monitoring capabilities. Compared to a constellation of three nadir altimeters (the present configuration), analysis and forecast errors are reduced by a factor of 2. Our results also show that a constellation of two wide-swath altimeters has better performance than a constellation of 12 nadirs. Compared to a constellation of 12 nadirs, the error of the Sea Surface Height (SSH) forecast of a two wide swath constellation will be reduced by 14 % overall. Improvements are also observed when analysing surface currents and Lagrangian diagnostics. A constellation of two wide-swath altimeters thus seems to be a very promising concept for the long-term evolution of the Sentinel-3 topography mission. [ABSTRACT FROM AUTHOR]

Soil Moisture and Ocean Salinity (SMOS) level 2 and level 3 products are simulated and characterized over a one-year time period. A simulator is first used to evaluate the sea surface salinity (SSS) error of level 2 SMOS products. An optimal interpolation method is then adapted to map the surface salinity in order to simulate a level 3 SMOS product. The quality of the simulated products is satisfactory. The mean error of the SSS at pixel scale is around 1 psu, and the error on the final gridded product fits the Global Ocean Data Assimilation Experiment requirements (0.2 psu). Index Terms--Brightness temperatures, microwave radiometry, optimal interpolation, remote sensing, sea surface salinity (SSS), Soil Moisture and Ocean Salinity (SMOS).

High-resolution numerical experiments of ocean mesoscale eddy turbulence show that the wind-driven mixed layer (ML) dynamics affects mesoscale motions in the surface layers at scales lower than O(60 km). At these scales, surface horizontal currents are still coherent to, but weaker than, those derived from sea surface height using geostrophy. Vertical motions, on the other hand, are stronger than those diagnosed using the adiabatic quasigeotrophic (QG) framework. An analytical model, based on a scaling analysis and on simple dynamical arguments, provides a physical understanding and leads to a parameterization of these features in terms of vertical mixing. These results are valid when the wind-driven velocity scale is much smaller than that associated with eddies and the Ekman number (related to the ratio between the Ekman and ML depth) is not small. This suggests that, in these specific situations, three-dimensional ML motions (including the vertical velocity) can be diagnosed from high-resolution satellite observations combined with a climatological knowledge of ML conditions and interior stratification. [ABSTRACT FROM AUTHOR]

The impact of Surface Water Ocean Topography (SWOT) satellite on the ocean horizontal and vertical velocities is investigated by means of OSSEs (observing system simulation experiments). These experiments are performed with a regional data assimilation system, implemented in the Iberian–Biscay–Ireland (IBI) region, at 1/12° resolution using simulated observations derived from a fully eddy-resolving free simulation at 1/36° resolution over the same region. The objective of the experiments is to assess the ability of SWOT to constrain the ocean analyses and forecasts with respect to conventional nadir altimeters (Jason 1, Jason 2 and Envisat). Previous analysis of these experiments conducted in Benkiran et al. (2016) have shown a great improvement (when using SWOT-like data rather than conventional altimeters) of the root-mean-squared-error (rmse) of the Sea Surface Height (SSH) calculated with respect to the true ocean. This Work further explores these results including the analysis of the horizontal and vertical velocities fields and their vertical structure. Preliminary analysis shows that SWOT data allows a better positioning of eddies on frontal zone and thus a better control of the horizontal and vertical velocities. Assimilation of SWOT data does not only improve the surface velocity; it also improves velocity field at the depth. There is a clear positive impact of the assimilation of SWOT up to 1000m of depth. [ABSTRACT FROM AUTHOR]