Ocean High Frequency Dynamics de-aliasing and related Geodetics

Author:

Florent Lyard - (LEGOS)

Co-Investigator(s):

Damien Allain (CLS/LEGOS)
Christian Bizouard (Observatoire de Paris/SYRTE)
Jean-Paul Boy (EOST/IPGS)
Mathilde Cancet (NOVELTIS)
Loren Carrère (CLS)
Pascal Gégout (GET)

Abstract:

High frequency corrections are a crucial contributor to the sea level error budget. During the last 30 years, continuous efforts and consecutive improvements have been made to reach the requested accuracy for ocean altimetry satellite missions. In most of the ocean surface, the present tidal and storm surges corrections are close to the targeted accuracy. However, the error budget is not homogeneous and shallow seas and high latitude/polar seas still remain an issue. In addition, some more demanding satellite data applications (such as mesoscale and sub-mesoscale investigations in the forthcoming SWOT mission observations) are challenging the former definition of error budget target levels and the needs for near-shore corrections. The LEGOS laboratory, in collaboration with CNES, CLS and Noveltis, has been and remains deeply involved in improving the tidal atlases (FES series) and providing storm surge simulations needed for the sea level dealiasing processing. A project supporting the upgrade of the FES tidal atlases will be launched shortly, with an official release scheduled in 2022.

We intend to continue this effort by focusing on reducing the geographical heterogeneity of the error budget and investigate on more subtle, but significant terms such as tidal and atmospheric loading in coastal regions, non-linear tides in deep oceans and internal tide surface signal. Main modelling efforts will be put on FES2022 unstructured mesh resolution, with a (close to) 1 km target in coastal regions, bathymetry improvements and improved loading and self-attraction.

Recent progress in physical parameterizations (non-hydrostatic pressure, mean sea level gradient, internal tide drag) will be assessed. Last but not least, renewed efforts will be put on the observation and analysis of tides with altimetry, especially in polar seas, using a multi-mission approach either to densify the spatial coverage of available assimilation/validation data (shelf/coastal ocean) or to aggregate altimetry time series in polar seas to consolidate the harmonic analysis accuracy. This project must be understood as a continuous effort toward homogenous, accurate and spatially comprehensive high frequency corrections. It is complementary to the COCTO-FO (SWOT project, see appendix) science investigations and the production-dedicated FES2022 project. Its specific objectives are to offer the scientific frame and meeting opportunities to interact closely within the OSTST community and provide dedicated expertise to the Jason series nadir altimetry missions and other altimeter missions listed as taking part in the ocean surface topography virtual constellation.

Supported by CNES.