A brief descripton of the available ocean tide models
Last updated: 2 November 2022
For a broad overview, status of 2014, see Stammer
et al. (2014).
The Schwiderski model is the oldest (1980) model in this collection and is included because it has been the standard for so many years. It is a hydrodynamic model, given on a 1 by 1 degree grid and uses an interpolation scheme to fit the tide gauges.
NAO.99b is based on the same hydrodynamics as the Schwiderski model but has TOPEX/Poseidon data assimilated into it and is given on a 0.5 by 0.5 degree grid.
FES94.1 is a pure
hydrodynamic tide model tuned to fit tide gauges globally.
It has been calculated on a finite element grid with very
fine resolution near the coast but the version used here
is given on a 0.5 by 0.5 degree grid. In FES95.2 the tides
in the Arctic were improved and TOPEX/Poseidon data has
been used to adjust the long wavelength behaviour of
FES94.1. FES98 is again a pure
hydrodynamic model that has assimilated a set of roughly
700 carefully selected tide gauges into it. Another
improvement is the fact that is has been computed on a
global grid instead of computing the ocean tides in a few
ocean basins separately and then glueing the solutions
is an update of FES98 and has TOPEX/Poseidon data
assimilated into it. Both FES98 and FES99 are given on a
0.25 by 0.25 degree grid.
FES2004 is a further
development in the FES series. Letellier
is shown in our reference list as responsible for both;
the thesis (in French) produced FES2004 and discusses
FES99. FES2004 has a 0.125 degree resolution. It
assimilates TOPEX/POSEIDON altimetry into a
hydrodynamic tide model. The thesis also presents
higher-harmonic waves (M3, M4, M6) which so far have not
been adapted to the loading provider site.
has a still higher resolution (1/16×1/16
degree). In the tradition of its predecessors (including
FES2012) it emphasizes ocean hydrodynamics and especially
keeps impact from assimilation of altimetry low, thus
avoiding a fallacy of biased consistency in these
missions. FES2014 has gained endorsement from a.o. IERS.
CSR3.0 and CSR4.0 are long wavelength adjustments of FES94.1 using TOPEX/Poseidon data and are given on a 0.5 by 0.5 degree grid. Unfortunately, these two models have spurious gridcells over land that have been removed using the grid of GOT00.2 as a mask. At the same time GOT00.2 has been used to add extra tidal values in the Weddell and Ross Sea in the Antarctic. For the other tidal values below and above the 66S and 66N latitude (the limits of the TOPEX/Poseidon satellite), these models become equal to FES94.1.
GOT99.2b and GOT00.2
is again long wavelength adjustments of FES94.1 using
TOPEX/Poseidon data and are given on a 0.5 by 0.5 degree
grid. GOT99.2b also becomes equal to FES94.1 outside the
66 degree latitudes. GOT00.2 is different from FES94.1 in
the polar region because ERS1/2 data is used in the
assimilation process. Follow-up models GOT4.7
are based primarily on evolving satellite altimetry
missions with refined adjustments for global tidal mass
and mass-centre, and atmospheric corrections. GOT4.10 is
the latest version of Richard Ray's tide models and is
solely based on Jason1&2 altimetry. GOT4.8 has become
one of the standard tide models, besides FES2004, that is
used for Satellite Altimetry corrections and for
GNSS software and data products from JPL.
HAMTIDE is based on the generalized inverse methods for tides developed at the University of Hamburg. DGFI altimeter data bank obtained from 15 years time series observed by TOPEX and Jason-1 was used in the assimilation process. It is hoped that more information can be found in the future publication of Taguchi et al.
TPXO.5 through TPXO.7.1 have been
computed using inverse theory using tide gauge and
TOPEX/Poseidon data. It finds the optimum balance between
observations and hydrodynamics. TPXO.5 is given on a 0.5
by 0.5 degree grid while TPXO.6.2 and successors are given
on a 0.25 by 0.25 degree grid. TPXO.7.0 and TPXO.7.1
differ only in the constituents P1 and S2. The latest
version TPXO.7.2 also includes GRACE data. The TPXO_Atlas
version is a combination of the global solution TPXO.7.2,
patched with local tide models.
EOT08a and EOT11a
are based on harmonic analysis of multi-mission altimetry
(TOPEX, Jason-1, ERS1, ERS2, ENVISAT, GFO) which implies a
13 year time base. The tides are represented on a 0.125
AG06a is an adjustment of the FES94.1 model to multi-mission altimetry ((TOPEX, Jason-1, ERS1, ERS2, ENVISAT, GFO). The tides are represented on a 0.5 degree grid. This model has been superseded by DTU10 which is an adjustment of FES2004.
OSU12 is a pure empirical tide model based on satellite altimetry data from TOPEX, Jason-1/-2, Envisat, and GFO that have been interpolated using least-squares collocation onto a 0.25x0.25 degree grid. The covariance matrix used in this procedure varies from place to place and depends on the depth of the ocean. Only diurnal and semi-diurnal harmonics are provided.
Not all models come with long-period tides. In order to
cover the whole spectral range, recognising that
long-period tide loading effects are generally at the
millimetre level, the models have been supplemented as
shown in Table 1.
Next, one must be aware that some ocean tide models miss certain shallow water areas. This could lead to erroneous ocean loading values if your station is close to a sea that your chosen ocean tide model is lacking. These areas are given in Figure 1. Each coloured area is associated with the names in the same colour. For example, the Mediterranean Sea is missing in Schwiderski (SCHW) and FES94.1.The ocean tides are small in the Mediterranean Sea and very small in the Baltic and Black Sea. Omision of these particular areas in the models is therefore not a big problem.