[MITgcm-devel] horiVertRatio in forcing

[Alistair Adcroft]

The "r" are in the names because it is the "density" in "r" coordinates as
opposed to mass per unit physical volume.

A.
--
Dr Alistair Adcroft            http://www.mit.edu/~adcroft
MIT Climate Modeling Initiative        tel: (617) 253-5938
EAPS 54-1523,  77 Massachusetts Ave,  Cambridge,  MA,  USA

-----Original Message-----
From: mitgcm-devel-bounces at mitgcm.org
[mailto:mitgcm-devel-bounces at mitgcm.org] On Behalf Of Chris Hill
Sent: Friday, December 05, 2003 8:41 AM
To: MITgcm-devel at mitgcm.org
Subject: RE: [MITgcm-devel] horiVertRatio in forcing


J-M

Do we need the r in the names. Why not m2v(k) and v2m(k)? I always think of
the volume as dx*dy*dr and letting the units be whatever they are. Is that
bad? 

In general it would be really nice to tidy this up everywhere into a form we
all agree on. 
I've never liked horiVertRatio either (even though I created it!) but I've
never seen a better suggestion for how to encode what we need. I would
prefer something that we can apply consistently everywhere. Not sure what it
will be but I know it will make Alistair's blood pressure rise to discuss
it, which is always fun. 

Chris

> -----Original Message-----
> From: mitgcm-devel-bounces at mitgcm.org 
> [mailto:mitgcm-devel-bounces at mitgcm.org] On Behalf Of Jean-Michel 
> Campin
> Sent: Thursday, December 04, 2003 11:02 PM
> To: MITgcm-devel at mitgcm.org
> Subject: [MITgcm-devel] horiVertRatio in forcing
> 
> Hi,
> 
> I have a suggestion regarding horiVertRatio:
> 
> right now we have :
> 
> horiVertRatio = 1 (if r=z)
> horiVertRatio = gravity*rhoConst (if r=p)
> 
> Since non-boussinesq (p-coordinate) does not need any constant 
> (reference) density, it's a litle curious to see rhoConst in the 
> P-coordinate model, although, since horiVertRatio is (almost) always 
> used as horiVertRatio/rhoConst or rhoConst*recip_horiVertRatio, this
> is not a real problem.
> 
> I propose (in a first step in external_forcing_surf only) to use:
> 
> mass2rVolum :: convert mass unit (kg) to "model" volume unit ( 
> 1/"model density")
>                so that: (dx*dy*dr)_unit = mass2rVolum * dMass_unit
>                mass2rVolum = 1 / rhoConst (if r=z) ; =
> gravity (if r=p) ; rVolum2mass :: convert "model" volume unit 
> to mass unit (kg) (= "model density")
>                so that: dMass_unit = rVolum2mass * (dx*dy*dr)_unit
>                = rhoConst (if r=z) ; = 1/gravity (if r=p) ; 
> 
> The name for those 2 constants can change (althougth not too long 
> would be better). But I think it could help to clarify the forcing and 
> diagnostic units.
> 
> I looked to other places where horiVertRatio is used, and seems to be 
> only in NonHydrostatic parts:  ini_cg3d.F
>  cg3d.F
>  solve_for_pressure.F (NH part)
>  mom_u_coriolis_nh.F
>  mom_u_metric_nh.F mom_v_metric_nh.F
> 
> I think that we can leave those S/R as they are, because
> a) in z coordinate, it's easy to remember that horiVertRatio=1.
> b) it does not matter too much since P-coordinate cannot
>    really be used with NonHydrostatic. horiVertRatio is just there 
>    to make the units right, no more.
> 
> Any comment ?
> 
> Jean-Michel
> _______________________________________________
> MITgcm-devel mailing list
> MITgcm-devel at mitgcm.org
> http://dev.mitgcm.org/mailman/listinfo/mitgcm-devel
> 

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