May 1995 Recommendation of TOPEX/POSEIDON Ocean Tide Model

Status of Tide Models within the T/P Project

In May 1995 a meeting of the Tides Committee of the T/P Science Working Team was held to discuss the merits of new ocean tide models. This meeting, chaired by C.K.Shum (with C.Le Provost and P.L.Woodworth), was a follow-on to an earlier exercise in January. Models considered totalled 10 (7 new models plus 3 models which were evaluated during the interm tide model evaluation period in January): 

   AG95.1  - KMS Andersen-Grenoble Model
   CSR3.0  - UT/CSR Eanes Model
   DW95.0  - CU Desai-Wahr Model
   FES95.1 - Grenoble LeProvost et al. Model
   KANTHA  - CU Kantha Model
   ORI     - U. of Tokyo Ocean Research Institute Matsumoto Model
   SR95.0  - Delft/GSFC Schrama-Ray Model
  *GSFC94A - GSFC Sanchez-Pavlis Model
  *RSC94   - GSFC Ray-Sanchez-Cartwright Model
  *TPXO.2  - OSU Egbert et al. Model
The evaluation tests conducted included: 

1. Crossover residual analysis.
2. Pelagic tide gauge analysis.
3. T/P sea level time series analysis.
4. Tide gauge time series analysis.
5. Examining model differences.
6. Comparison to gravity loading measurements.
7. Orbit tests.
In brief, the meeting decided to recommend that two of the new models be used for reprocessing of T/P data, including the generation of new T/P CDROMS. The recommendations were subsequently updated following further discussions between modellers. The two were:

CSR3.0 - developed by Richard Eanes and colleagues at the University of Texas. The model is basically a long wavelength adjustment to the Grenoble FES94.1 hydrodynamic model. Thereby, a tide model product is produced which preserves the long wavelength accuracy of T/P with the detailed resolution of the Grenoble model.

and FES95.2 (a development of 95.1) - developed by Christian Le Provost and colleagues at the University of Grenoble. This model is an assimilation of the earlier CSR2.0 T/P-derived model into the FES94.1 hydrodynomic scheme.

These two models therefore both contain altimetry and modelling and in some sense can be said to approach an optimum model from different directions. Unfortunately, neither of them is as yet documented in the literature.

For information contact:

Richard Eanes eanes@csr.utexas.edu

and Christian Le Provost clp@img.fr

It is important to realise that the choice of these two models does not mean that they are necessarily 'better' than the others. Several models are virtually identical, while each one has its odd features. As further years of T/P altimetry become available, then models might be expected to improve further.