[MITgcm-support] EmPmRfile, EmPmR

Thu Mar 22 14:11:23 EDT 2007

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
> >>>>> _______________________________________________
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