[MITgcm-support] external forcing wind

Thu Jul 6 07:11:26 EDT 2023

Dear all,

I don't know how it is handled exactly in Darwin, but I think it is 
similar to the DIC package.

The point here is that biogeochemical packages need wind speed for 
calculating the gas exchange rate of carbon (possibly also for other 
gases, like O2). That is why you have the possibility to read in a field 
of wind speed (note, the speed, not the u and v components). This field 
is then solely used for gas exchange, not for physics.

The physics forcing by wind is either described in data (if you use wind 
stress files), or data.exf (if you use 10m winds).

Why is this treated searately? One could also use the components, to 
calculate wind speed, of course. But especially if one uses monthly 
averaged winds, the wind speed calculated from these averages 
underestimates the averaged true wind speed, which also contains a 
contribution from the deviations from the average (u'*u' and v'*v').

Cheers, Christoph

On 06.07.23 12:26, Dattilo, Francesco wrote:
> Thank you very much for the answer Manfredi,
> 
> However, still having set the same options you provided to me, if I run 
> the model like this I receive this warning:
> 
> "** WARNING ** DARWIN_EXF_READPARMS: default constant wind speed 
> ',windconst <https://gud.mit.edu/darwin3/ident?v=darwin3;i=windconst>,' 
> m/s is used'"
> 
> This seems because I have to set "darwin_useEXFwind = .TRUE." and 
> "DARWIN_haveWind = .FALSE" in data.darwin.
> 
> My confusion comes from this, because in the example mentioned before 
> there is no reference to these two boolean values.
> 
> Do you have any ideas about it?
> 
> Thank you very much
> 
> Francesco
> 
> Il giorno mer 5 lug 2023 alle ore 17:42 Manfredi Manizza 
> <mmanizza at ucsd.edu <mailto:mmanizza at ucsd.edu>> ha scritto:
> 
>     Hi Francesco,
> 
>     it depends on the files and the set-up.
> 
>     Normally on a 3D domain set-up you would use "data.exf" where you
>     specify the input file of wind speed if you use interannual winds
>     as in ECCO.
>     So you do not read that from the "data" file but it seems not to be
>     your case....
> 
>     You might want to check this 1-D set-up of the ross sea:
> 
>     https://github.com/MITgcm-contrib/ecco_darwin/tree/master/idealized/1D_darwin/ross_sea/run <https://github.com/MITgcm-contrib/ecco_darwin/tree/master/idealized/1D_darwin/ross_sea/run>
> 
>     It might give you a hint about how to read the wind in your 1-D case.
> 
>     In this experiment the wind forcing is read in the "data" file.
> 
>     Here a file where to follow the correct options:
> 
>     https://github.com/MITgcm-contrib/ecco_darwin/blob/master/idealized/1D_darwin/ross_sea/code/EXF_OPTIONS.h <https://github.com/MITgcm-contrib/ecco_darwin/blob/master/idealized/1D_darwin/ross_sea/code/EXF_OPTIONS.h>
> 
>     I never used it but I hope this can be useful for you to set-up
>     yours correctly.
> 
>     Good luck.
> 
>     Manfredi
> 
> 
> 
> 
> 
>     On Wed, Jul 5, 2023 at 2:15 AM Dattilo, Francesco <fdattilo at ogs.it
>     <mailto:fdattilo at ogs.it>> wrote:
> 
>         Hi everyone,
> 
>         I'm working with the Darwin package. I'm a bit confused about
>         how to set wind as external forcing.
>         I saw that it is possible to specify the zonal wind and the
>         meridional wind in the "data" file, and this seems to be
>         consistent with the example
>         <https://urldefense.com/v3/__https://mitgcm.readthedocs.io/en/latest/examples/barotropic_gyre/barotropic_gyre.html*sec-eg-baro__;Iw!!Mih3wA!F0NpPv7kBp5gSoyJ2jM9Iva1V7k3g7RPj8LMYuP_v6xziAU6aZe1H0hJG2K2LEr1zkauGJQzZoIqHFirQA$> . However, it seems that I have also another way, by modifying the "data.darwin" file, specifying the windFile and "darwin_useEXFwind = .TRUE." and "DARWIN_haveWind = .FALSE."
>           but in this case it is not clear to me:
> 
>         1) which kind of file has to be the "windFile"
>         2) if it is correct to set "darwin_useEXFwind = .TRUE."  and
>         "DARWIN_haveWind = .FALSE."
> 
>         Using a 1D model I also don't know what's the proper choice.
> 
>         Thank you very much for every suggestion
> 
>         Best regards
> 
>         Francesco Dattilo
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> 
> 
> 
>     -- 
> 
>     Dr. Manfredi Manizza
>     Geosciences Research Division
>     Scripps Institution of Oceanography
>     University of California San Diego
>     9500 Gilman Drive La Jolla, CA 92093-0244
>     email :mmanizza at ucsd.edu  <mailto:mmanizza at ucsd.edu>
>     tel   : +1-858-534-7094
>     web   :http://bluemoon.ucsd.edu/mmanizza/  <http://bluemoon.ucsd.edu/mmanizza/>  
> 
>     web   :https://mmanizza.scrippsprofiles.ucsd.edu/  <https://mmanizza.scrippsprofiles.ucsd.edu/>
> 
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-- 
Christoph Völker
Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research
Am Handelshafen 12
27570 Bremerhaven

+49 (0)471-4831-1848
christoph.voelker at awi.de
https://orcid.org/0000-0003-3032-114X