OCEAN TIDES

The FES2014b (MSf corrected) model is available for download as spherical harmonic coefficients.

The original FES2014b documentation and  1/16° x 1/16° grid files can be found on the AVISO web site.

The original amplitude and phase grids of FES2014b have been processed in the following way (in order to deliver products usable by orbit computation softwares):

  • adoption of the corrected MSf wave instead of the original one (in the original MSf wave, only the non-linear part of this wave was given, whereas in the corrected MSf wave the complete wave amplitude is given – non-linear and quasi-equilibrium parts)
  • setting tide amplitude to zero on the land areas
  • conversion to spherical harmonics (SH) up to degree and order 100 x 100 for each wave
  • application of an ellipsoidal correction to the SH coefficients in order to pin the water heights to the ellipsoidal surface of the Earth
  • addition of the long-period Om1 and Om2 waves (only the C20 coefficient)
  • removal (or not) of the S1 wave (depending on the ocean dealiasing model used)

Explanation: In the TUGO dealiasing product, the atmospheric S1 wave cannot be distinguished from the astronomic S1 wave, so the TUGO products include the S1 astronomic wave and therefore this wave should not be taken into account in the ocean tide model.

The load Love numbers used for the conversion from water heights to geopotential coefficients have been computed by Pascal Gégout up to SH degree 250. They are given HERE (the values in the file are SH degree, h’, l’ and k’).

The FES2014b (MSf corrected) ocean tide model in spherical harmonics therefore comes in two versions (with or without S1 wave).

 

  • FES2014b Spherical harmonics in water height:

FES2014b with S1 wave

FES2014b without S1 wave

 

  • FES2014b Spherical harmonics in geopotential units:

FES2014b with S1 wave

FES2014b without S1 wave

 

CAVEAT

For those who retrieved the files from this site before December 7, 2019, we recommend to discart these files and reload the new ones, which are correct at present.

Short explanation:

The main differences of this new « FES2014.v1 » version with the version that was originally posted on October 21 are the following:

  • Correction of an error on the oceanic margins. There was a big mistake in the first release of the FES2014b in spherical harmonics: we had taken a version of the FES2014b grids extrapolated over the continents. This error was already corrected on November 12, 2019 and the correct files uploaded to the server the same day.
  • Full spherical harmonics development of the Om1 wave to degree/order 100.
  • Correction of the Doodson numbers of the Sa and S1 waves. The new Doodson numbers (056.555 and 164.555) are in accordance with the values used by the FES team (they differ from the values used in the IERS2010 Conventions).
  • Files in “potential unit” format:
    • Correction of an error on the χ phase convention for the MSf and MSq waves. There was a bug in our software which was giving a wrong value of 180° of χ for these waves.
    • Change of the χ phase convention for S1 to 180°, in order to be in accordance with its radiational nature.

More detailed explanations on these changes are given here: Explanations on FES2014b.v1