[MITgcm-support] Re: single layer run

[Sergey Vinogradov]

Martin:
I think I will check the verification example of inv. barometer, with 1 
layer instead on 4. Maybe I had a bug somewhere in my configuration.
Thanks,
Sergey

Martin Losch wrote:

> Hi Sergey,
>
> I am convinced that even in the case of constant (in time) pressure 
> forcing you should end up with a steady state that is non-zero, also 
> in the case of a single layer.
>
> Try (possibly in an idealized configuration) starting from rest (ssh = 
> 0, single layer), without any forcing. The system should remain 
> motionless. Then add constant pressure forcing (pLoadFile) in pressure 
> units, after adjustment processes have faded away, the circulation 
> should be steady (and non-zero), according to the inverted barometer 
> effect. If this all works, you know at least that the model has no 
> serious problem.
>
> Martin
>
> On May 13, 2005, at 3:52 PM, Sergey Vinogradov wrote:
>
>> Martin:
>> I do initialize the experiment with prescribed SSH (which is computed 
>> as inverted barometer for the initial atm.pressure). Then the atm. 
>> pressure forcing evolves in time and space. I don't have problems 
>> with several layers configuration, but in a single-layer setup the 
>> model doesn't seem to "feel" the atm. pressure forcing at all, 
>> instead, it just solves the problem of the barotropic adjustment of 
>> the initial condition. I was thinking if the single layer is really 
>> applicable for this type of experiment?
>> Regards
>> Sergey
>>
>> Martin Losch wrote:
>>
>>> Sergey,
>>>
>>> if you apply pressure forcing that evolves in time, then your flow 
>>> field should also vary in time. Even if your pressure forcing is 
>>> constant in time (and variable in space), you should reach a 
>>> non-trivial steady state (inverted barometer effect), that should 
>>> have something like the following balance:
>>> f*v + g*d(ssh)/dx + (1/rho0)*dp/dx = 0 (and something similar for 
>>> the v-momentum equation, with p=atmospheric pressure), note that the 
>>> ssh can (and probably will) be zero in this case.
>>> There is  a verification experiment that does this with 4 layers 
>>> (inverted_barometer) and constant (in time) forcing. Maybe you can 
>>> modify this experiment, or try to see what's different in your case?
>>>
>>> What do you mean by initial sea-surface height? Do you prescribe an 
>>> initial SSH?
>>>
>>> Martin
>>>
>>> On May 10, 2005, at 10:47 PM, Sergey Vinogradov wrote:
>>>
>>>> Hi Ed:
>>>> The pressure loading is a realistic variable forcing.
>>>> Actually this raises the question if a single layer is a valid 
>>>> configuration for such experiment...
>>>> Regards
>>>> Sergey
>>>>
>>>> Ed Hill wrote:
>>>>
>>>>> Hi Sergey,
>>>>>
>>>>> I've subscribed you to the MITgcm-support email list so that any
>>>>> subsequent emails you send will get through.  And I've forwarded your
>>>>> email below.
>>>>>
>>>>> In regards to your question, wouldn't one expect the ocean to reach a
>>>>> quiescent (zero-velocity) solution if it were forced with a steady
>>>>> atmospheric pressure?  Or are you varying the atmospheric pressure 
>>>>> over
>>>>> time and space?
>>>>>
>>>>> Ed
>>>>>
>>>>> === original message ===
>>>>>
>>>>> Hello,
>>>>>
>>>>> After enough playing with a global baroclinic runs, I decided to 
>>>>> try a
>>>>> barotropic run for which I set eosType to 'linear' and specify a 
>>>>> single
>>>>> layer with delZ=5000. After several timesteps, the initial 
>>>>> sea-surface
>>>>> height in the open ocean just dies to zero, while the initial ssh 
>>>>> along
>>>>> the coasts stays the same. No other terms have been changed from the
>>>>> baroclinic experiment setup. Any suggestions how to make it run 
>>>>> will be
>>>>> greatly appreciated. I forgot to mention that I force the model with
>>>>> atmosperic pressure only.
>>>>>
>>>>> Regards,
>>>>> Sergey Vinogradov
>>>>>
>>>>>
>>>>>
>>>>
>>>> _______________________________________________
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>>>>
>>> Martin Losch // Alfred-Wegener-Institut für Polar- und Meeresforschung
>>> Postfach 120161, 27515 Bremerhaven, Germany
>>> mailto:mlosch at awi-bremerhaven.de // Tel./Fax: ++49(471)4831-1872/1797
>>> http://www.awi-bremerhaven.de/People/show?mlosch
>>>
>>>
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>>
>>
>>
>>
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