Input data of HYCOM SSS

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Nov 4, 2020, 9:17:07 AM11/4/20
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I have a question about input data of HYCOM SSS.
Are there any satellite-based SSS (i.e., SMOS and SMAP) products used as input data to retrieve HYCOM SSS?
Thank you!

Alan Wallcraft

Nov 4, 2020, 10:18:58 AM11/4/20
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No satellite-based SSS observations are used in the assimilation, see

J. A. Cummings and O. M. Smedstad, 2014:
Ocean Data Impacts in Global HYCOM
Journal of Atmospheric and Oceanic Technology vol 31 doi:10.1175/JTECH-D-14-00011.1

which is for GOFS 3.0 but I think still relevant to the observation sources in GOFS 3.1.


E.J. Metzger, R.W. Helber, P.J. Hogan, P.G.Posey, P.G. Thoppil, T.L. Townsend, A.J. Wallcraft, O.M. Smedstad, and D.S. Franklin, 2017:
Global Ocean Forecast System 3.1 Validation Testing
NRL Report NRL/MR/7320--17-9722

Which compares the top 500 m salinity against unassimilated profiles.

GOFS 3.1 does relax SSS towards monthly climatology providing the model SSS is within 0.5 psu of climatology (otherwise it does no relaxation, e.g. near river mouths).


Luana F. Bueno

Mar 24, 2022, 9:33:23 AMMar 24
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Hi Alan,

Can you please tell me the difference between using the sssbal flag 1 or 2 (1=offset,2=scale)? 
I also would like to know if I can have access to the file that controls the relaxation near river mouths that you mentioned above?
I was not able to find it on github repositories.

Thank you in advance.
Best regards,

Luana Bueno

Alan Wallcraft

Apr 1, 2022, 10:47:42 AMApr 1
to Forum,, Alan Wallcraft
ssbal=1 applies a constant offset everywhere to make the region-wide sum of the flux zero.

ssbal=2 calculates the positive and negative flux sums and then scales up whichever is smaller in magnitude so that negative equals positive fluxes (i.e. zero net).  The maximum allowed scale factor is 5x, so if the ratio is too large the net is not exactly balanced.

The relaxation near river mouths is turned off "automatically" because in these regions model SSS is typically not within 0.5 psu of climatology.

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