[MITgcm-support] time-dep-wind-file

[Stefano Querin]

Hi Matt and Ming,
just few hints about the time dependent wind stess problem (as Matt said, this may NOT be the only and rightest solution...!!!).
You can prescribe time dependent wind stress either using  periodicExternalForcing  in the data namelist or activating the exf package (exf needs also the cal package, they must be used together).
The first method is simpler (no exf and cal) but less adaptable. When you set periodicExternalForcing=.TRUE. (then you can set externForcingPeriod=.... and  externForcingCycle=....  in the same namelist) the model reads the windstress file that is specified in data (zonalWindFile and meridWindFile in PARM05). You don't need any data.exf, data.exf_clim, data.cal namelist.

Personally, I would suggest you to use the second method: you can add the packages exf and cal in packages.conf, or create a new package group in pkg_groups and then specify the new group using the pkg_default file when launching genmake2 (as you prefer...). With this configuration, the namelist data has nothing to deal with external forcing any more (just set periodicExternalForcing=.FALSE.). Now you have to specify external forcing files and periods in the data.exf file. The exf routine can also interpolate spatially the gridded wind stress data, can compute wind stress from wind velocity (always splitted in meridional and zonal components), can calculate heat fluxes... It is a bit more complicated but much more useful than the previous method!
I attach some of the files I used for my runs (just take a look, they should be clearer than long -and boring- explanations).
Just some remarks:
- I don't think that the ecco pkg is compulsory if you use exf (and cal): I only cut and paste some CPP options I was intrerested in from ECCO_CPPOPTIONS.h file to CPP_OPTIONS.h, it works!
- there is some obcs related stuff in some files, if you don't need open boundaries, just comment it out and remove obcs from the package group (in pkg_groups).

I tried to be as clear as possible (at least I hope so!).
Good luck!

Stefano

P.S.: the interpolation in time is linear in both cases but (if I remember well) in the first one the value read from file is assumed in the middle of the external forcing time interval, in the second one, it is assumed at the beginning of the interval (i.e.: if you read exf data every hour, you need 25 records to complete a 1 day simulation)
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