[MITgcm-support] EmPmRfile, EmPmR

Thu Mar 22 14:29:13 EDT 2007

Why would you not have salt conservation if you turn off salt  
flux...if anything it seems the opposite?

And I was under the assumption that exactConserv forces the global  
net empmr flux to zero by adding a constant freswater flux to every  
cell...and one would not want this if you want to see a change in  
mean eta..am I wrong in what exactConserve does?

(I think the fresh water is added in the top in solve_for_pressure  
which calculates eta to make flow non-divergent...)

matt

On Mar 22, 2007, at 2:11 PM, <Martin.Losch at awi.de> wrote:

> I do not recommend turning off the salt flux. After all you want  
> salt conservation. The model is doing everything correctly
> (salt and volume conservation), if you useRealFreshWaterFlux  
> = .true. Additionally exactConserv=.true., makes the
> whole thing a little more accurate, but you do not need to change  
> the code. The fresh water is added elsewhere (would
> need to search for it myself, but it's somewhere in  
> integr_continuity/solve_for_pressure/integr_for_w).
>
> Just use
>  useRealFreshWaterFlux = .true.,
> and maybe
>  exactConserv = .true.,
> and things should work.
>
> Bye, I am off to vacation now.
>
> M.
>
> Martin Losch
> Alfred Wegener Institute
> Postfach 120161, 27515 Bremerhaven, Germany;
> Tel./Fax: ++49(0471)4831-1872/1797
>
>
>
> ----- Original Message -----
> From: Matthew Mazloff <mmazloff at mit.edu>
> Date: Thursday, March 22, 2007 5:11 pm
> Subject: Re: [MITgcm-support] EmPmRfile, EmPmR
>
>> Hi Patrick,
>>
>> I use real fresh water flux and do not use exact conserv and
>> everything is fine.  The mean sea level does change and this is OK
>> too.  The best way to do it would be to use non-linear free surface
>>
>> and turn off all salt flux....this is done by setting
>> convertFW2Salt
>> = 0.,
>>
>> I think you can also use  rhoConstFresh=1000. to set the density of
>>
>> the rain water...not sure..check in external_forcing_surf.F
>>
>> -matt
>>
>>
>>
>>
>> On Mar 22, 2007, at 11:39 AM, Patrick Rosendahl wrote:
>>
>>> Hi Martin,
>>>
>>> thanks! I use the non-hydrostatic formulation. I think you are
>>> referring to this
>>>>> http://mitgcm.org/pelican/code_reference/vdb/code/167.htm#192_L
>>> section of the code, where the Temp & Salt is actually added in a
>>
>>> way that is correct for the rainy surface height increase.
>> (Please
>>> scroll up a few lines until you see the "#ifdef EXACT_CONSERV").
>>>
>>> Do you think I can change the code to execute it anyway (it is
>> not
>>> executed because of
>>>>> nonlinFreeSurf.GT.0 .OR. usingPCoords
>>> is false)?
>>> Additionally, I probably have to change the eta-code, so that the
>>
>>> rain is increasing the surface level. But I cannot find a good
>>> place in the code to do it.
>>>
>>> best,
>>> Patrick
>>>
>>> Martin Losch wrote:
>>>> Patrick,
>>>> there is a flag called "useRealFreshWaterFlux", that makes the
>>>> model  add volume to the topmost grid cell. I recommend to use
>> it
>>>> along with  exactConserv = .true. (you need to have the
>>>> corresponding CPP flag  compiled with it). That should prevent
>>>> your surface cells from  getting negative salinities.
>>>> If you feel really adventurous turn on the non-linear free
>>>> surface  with r*-coordinates (global_ocean.cs32x15 has an
>> example
>>>> of this),  but that's not really required for the model use
>> actual
>>>> freshwater  flux (just makes is even more "physical" and stable
>>>> for the kind of  forcing that you are trying to apply).
>>>> Martin
>>>> PS. the EmPmR variable is used always (with or without seaice,
>>>> virtual salt flux or not).
>>>> On 22 Mar 2007, at 15:17, Patrick Rosendahl wrote:
>>>>> Hi!
>>>>>
>>>>> I want to simulate rain that actually increases the waterlevel.
>>
>>>>> If  I understand all the rain implementations in mitgcm, the
>> rain
>>>>> is  translated into a salt-flux. so after a while I will have
>>>>> negative  salt values in the upper layer...
>>>>>
>>>>> model configuration is a closed water bassin that is partially
>>
>>>>> rained on. non-hs.
>>>>>
>>>>> I do not want to diagnose the aim package.
>>>>>
>>>>> best,
>>>>> Patrick
>>>>>
>>>>> Andrea Molod wrote:
>>>>>
>>>>>> hi patrick,
>>>>>> can you be a little more specific about what you mean?
>>>>>> what kind of model configuration, and what do you mean
>>>>>> by 'do rain'? a diagnostic for it in an aim package run?
>>>>>> something else? then maybe we can answer.
>>>>>> andrea
>>>>>> ---------------------------------------------------------------
>> -
>>>>>> Andrea M. Molod, PhD.
>>>>>> Department of Earth, Atmospheric & Planetary Sciences
>>>>>> MIT
>>>>>> Tel: (617) 253-5458, Email: amolod at mit.edu
>>>>>> WWW:http://paoc.mit.edu/paoc/people/person.asp?
>>>>>> position=Postdoc&who=molod
>>>>>> ---------------------------------------------------------------
>> -
>>>>>> On Mon, 12 Feb 2007, Patrick Rosendahl wrote:
>>>>>>
>>>>>>> Hello all,
>>>>>>>
>>>>>>> the variable EmPmR is only used in the seaice and the
>>>>>>> aim_compon_interf package, the web-sourcecode tells me.
>>>>>>>
>>>>>>> What is the best way to do "rain" (neglecting the vertical
>>>>>>> velocities at the moment)?
>>>>>>>
>>>>>>> Best regards,
>>>>>>> Patrick Rosendahl
>>>>>>> _______________________________________________
>>>>>>> MITgcm-support mailing list
>>>>>>> MITgcm-support at mitgcm.org
>>>>>>> http://mitgcm.org/mailman/listinfo/mitgcm-support
>>>>>>>
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