A brief descripton of the available ocean tide modelsLast updated: 11 July 2012The 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 hydronamics 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
together. FES99
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
develompent 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
higherharmonic
waves (M3, M4, M6) which so far have not been adapted to
the loading
provider site. 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. GOT4.7 is the latest version of Richard Ray's tide models and has been derived from T/P, Jason1, ERS and GFO altimetry. It is one of the standard tide models, besides FES2004, that is used for Satellite Altimetry corrections. Since June 2012 we have included GOT4.8 which only differs from GOT4.7 for harmonic S2. 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 Jason1 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 multimission altimetry
(TOPEX,
Jason1, ERS1, ERS2, ENVISAT, GFO) which implies a 13 year
time base.
The tides are represented on a 0.125 degree grid. AG06a is an adjustment of the FES94.1 model to multimission altimetry ((TOPEX, Jason1, 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, Jason1/2, Envisat, and GFO that have been interpolated using leastsquares 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 semidiurnal harmonics are provided. Not all models come with longperiod tides. In order to
cover
the whole spectral range, recognising that longperiod
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.
