FES 2014, a new tidal model on the global ocean

Loren Carrere (CLS Space Oceanography Division, France)


Florent Lyard (Legos, France); Mathilde Cancet (Noveltis, France); Amandine Guillot (CNES, France)

Event: 2014 Ocean Surface Topography Science Team Meeting

Session: Tides, internal tides and high-frequency processes

Presentation type: Type Oral

Thanks to its current accuracy and maturity, altimetry is considered as a fully operational observing system dedicated to scientific and operational applications. In order to access the targeted ocean signal, altimeter measurements are corrected for several geophysical parameters among which the ocean tide correction is one of the most critical. Global ocean and loading tide models GOT and FES are operationally used in present altimeter GDRs. FES is a finite elements hydrodynamic model which assimilates altimeter and in situ data, while GOT model is build as an empirical adjustment based on altimeter data and a prior atlas (such as FES). The accuracy of tidal models has been much improved during the last 20 years. Still, significant errors remain mainly in shelf seas and in polar regions. A new global tidal model FES 2012 has been developed in 2012 taking advantage of longer altimeter time series, improved modelling and data assimilation techniques. Compared to other global tidal models, FES 2012 showed very good performances in all shallow water regions, but the validation diagnostics have also pointed out a few regions were the model tends to raise the residual variance; these problems can be partly explained by some local bathymetric issues, such as the Hudson bay for example.

An improved FES 2014 version is being developed in 2014. First, FES 2014 benefits from recent developments in the physical and numerical modelling (T-UGO model) which already allow for dividing the error of the pure hydrodynamic model by a factor two.
As several issues have been detected in FES2012 bathymetry, these have been corrected for FES2014 version. Moreover the grid resolution has been increased in areas of interest like shallow waters and on the slope of the continental shelves.
Additional upgrades are carried out, such as the use of longer altimeter time series (TP-J1-J2) and new altimeter standards (instrumental and geophysical corrections, and orbits). Moreover a larger assimilation dataset is considered including tidal gauges and more data all over the ocean and particularly in the high latitudes regions; a specific processing is used to get more accurate tide estimations from ERS-EN data at these latitudes.
Some validation results of FES2014 are presented here and particularly the scores of the pure hydrodynamic simulation, and of the assimilated final atlas.

Oral presentation show times:

RoomStart DateEnd Date
Red salon Wed, Oct 29 2014,11:15 Wed, Oct 29 2014,11:30
Loren Carrere
CLS Space Oceanography Division