It can be noticed, from the description of the two constituents
of the ocean dynamics total correction (oceanic
tide and DAC), that both of them contain all or part of
the S2 wave. Indeed, the S2 wave predicted from the COMAPI
tide model contains both the radiational and the gravitational
parts as the radiational part is introduced via the
altimetry data assimilation. Concerning the DAC, it naturally
contains the S2 radiational part. This means that the
radiational component of the S2 wave must be reintroduced
in the SSH, otherwise it would be removed twice.
There are actually (at least) three solutions to deal with
the S2 wave component in the DAC correction. The first
solution consists in retrieving the S2 contribution from
the atmospheric forcing used in the simulations for the
computation of the DAC (CLS method, used in the AVISO
products). In the second technique, the S2 wave is kept in
the atmospheric forcing and the model outputs are filtered
in order to eliminate the S2 wave contribution from the
DAC correction (CTOH/LEGOS method). The third
method, which was considered in this study, is based on
the second technique, but the model outputs are not filtered.
Instead, the S2 wave is reintroduced in the SSH by
predicting a radiational S2 from a mean radiational S2
wave computed over seven years of simulation of the
TUGO model using 3h ECMWF atmospheric forcing (in
the framework of the SLOOP Project funded by CNES,
Lamouroux et al., 2010). Finally, the total ocean dynamics
correction can be written as follows