[MITgcm-support] global simulations and resolution

[Samar Khatiwala]

Martin, found the scripts.

BTW: is there an automated way of customizing the code for my 
resolution/bathy
short of hand coding the mask data in mit_oceanmasks.m? Its a bit 
tedious :-)

Samar

On Sep 7, 2005, at 10:06 AM, Martin Losch wrote:

> Samar,
>
> I was afraid of that, but are the water masses really affected that 
> much by the asynchronous time step, that would be terrible.
>
> the matlab scripts are all available in 
> verification/global_ocean.90x40x15/diags_matlab
>
> Martin
> On Sep 7, 2005, at 3:54 PM, Samar Khatiwala wrote:
>
>> Hi Martin
>>
>> What is your momentum time step? I am guessing its pretty small (like 
>> 3600 s).
>> If so, the rather large tracer/momentum ratio in your integration 
>> (for async
>> timestepping) could really distort the equilibrium solution. I have 
>> run the
>> 2.8 deg 'OCMIP' configuration to equilibrium and found that the final 
>> solution
>> (after synchronous integration) differed markedly from the 
>> asynchronous
>> solution. I am not claiming this is the explanation for what you are 
>> seeing.
>>
>> It would actually be interesting to compare the solutions I have with 
>> yours.
>> I can send you the data files if you want (or you can send me the 
>> m-file you
>> used to make your pretty pictures).
>>
>> Samar
>>
>> On Sep 7, 2005, at 3:33 AM, Martin Losch wrote:
>>
>>> Hi there,
>>>
>>> I am running a 4x4 degree global simulation (almost identical to the 
>>> verification experiment global_ocean.90x40x15) in parallel to a 2x2 
>>> degree global simulation (180x80x23). These simulations differ 
>>> mainly in their respective horizontal and vertical resolution. Of 
>>> course, I had (initally) friction parameters adjusted, so that 
>>> viscAh=5e5 in the 4x4-run became 5e4 in the 2x2 run.
>>> Both experiments use trenberth winds, ncep heat flux (short wave and 
>>> the rest), SST and SSS restoring to Levitus, GM, KPP, no seaice, no 
>>> Arctic ... All runs are integrated for 3000 years with asynchronous 
>>> time stepping (deltaTtracer=172800 for the 4x4 and 43200 for the 2x2 
>>> runs).
>>> The solutions are broadly similar in terms of circulation (the 4x4 
>>> run is more sluggish, but I can tune the friction parameters so that 
>>> they give similar ACC transports, for example). What is really 
>>> different are the water masses, and I cannot see a way to make them 
>>> agree more closely:
>>> broadly speaking, in the 2x2-run: when compared to Levitus data, the 
>>> Southern Ocean (south off the ACC) is too cold and too salty. The 
>>> deep ocean (below 3000m) is far too cold. The 4x4-run is too cold 
>>> and too fresh below 3000m, but in the Southern Ocean theta is nearly 
>>> OK, but salinity is too low. (for pictures see 
>>> http://mitgcm.org/~mlosch/run2x2_ts.pdf and 
>>> http://mitgcm.org/~mlosch/run4x4_ts.pdf)
>>>
>>> I would like to know, how this difference can be explained, that is, 
>>> how I can tune either model (preferably the 2x2 degree model, 
>>> because is too cold) to be similar to the other. Is there any 
>>> experience with this out there? Is it possible that the vertical 
>>> resolution in combination with surface restoring is responsible for 
>>> this difference (the 4x4-top layer is 50m thick, whereas the  
>>> 2x2-top layer only 10m.)?
>>> Any suggestion is greatly appreciated.
>>>
>>> Martin
>>>
>>> _______________________________________________
>>> MITgcm-support mailing list
>>> MITgcm-support at mitgcm.org
>>> http://mitgcm.org/mailman/listinfo/mitgcm-support
>>
>> _______________________________________________
>> MITgcm-support mailing list
>> MITgcm-support at mitgcm.org
>> http://mitgcm.org/mailman/listinfo/mitgcm-support
>
> _______________________________________________
> MITgcm-support mailing list
> MITgcm-support at mitgcm.org
> http://mitgcm.org/mailman/listinfo/mitgcm-support