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Notes of praise to this site are rare. I comfort myself with the few that have arrived.
However, I'm grateful for the plenty of acknowledgments that haven't passed unnoticed when I read articles or attend conferences.
Thank you all.
H-G.

Notes and comments to the ocean tide loading provider


[mailheader from:] Jim Ray
Dear Hans-Georg,

Thanks very much for making the changes, including the new tide models.

Concerning the ocean geocenter motion, you might be interested in this
feedback from John Ries:

    I did a quick check and found that including the tidal geocenter
    terms did produce a measurable reduction in the SLR residuals for
    both Lageos-1 and Lageos-2...about 5-8 mm2 in variance. So I guess
    it is doing some good.

I hope that we can update the future Conventions to be clear on which
techniques should/should not apply the geocenter offset.

...

Thanks again and best regards,
--Jim

From: Matt King,
      Department of Geomatics
      University of Newcastle,

Date: 2002-FEB-15

Dear Hans-Georg

I hope the following comments are helpful.

Researchers should be careful using global tide models for computations of
ocean loading parameters for the Antarctic continent and the sub ice shelf
regions. This is because most of these models either totally exclude the
ice shelf regions or have insufficient bathymetric and coastline
information. The lack of bathymetric data included in the models is due to
the difficulty in measuring bathymetry in the sub ice shelf regions rather
than a failure to include data in the model computations.

For example, the FES99 model is 90 degrees out of phase and has a
significantly increased amplitude in the Amery Ice Shelf (AIS) region
(70E). This error was determined by comparing FES99 with in situ GPS data.
In the case of the AIS region this is due to very little bathymetry
information under the Amery Ice Shelf, including no information in the case
of the southern 200km. The coastline (grounding zone) definition in the
Amery Ice Shelf is also incorrect by 200km in this region in most models.

For Antarctica it is recommend that a regional tidal model be used, where
extra data have been included and coastline definitions updated. Examples
are the Circum-Antarctic Tidal Simulation (CATS) and Circum-Antarctic Data
Assimilation (CADA) models developed by Laurence Padman (Padman, L., H. A.
Fricker, R. Coleman, S. L. Howard, and L. Erofeeva, A new tide model for
the Antarctic ice shelves and seas, Ann. Glaciol., 34, in press, 2002.).

As always, buyer beware!

Cheers
Matt