[MITgcm-support] global simulations and resolution

[Martin Losch]

Samar,
I am afraid not, sorry. It's a little painful, I agree.

Martin

On Sep 7, 2005, at 4:30 PM, Samar Khatiwala wrote:

> 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
>
> _______________________________________________
> MITgcm-support mailing list
> MITgcm-support at mitgcm.org
> http://mitgcm.org/mailman/listinfo/mitgcm-support