[MITgcm-support] WTHMASS vs WVELTH

[Jean-Michel Campin]

Hi,

Just to clarify: WVELTH and WTHMASS are expected to be very similar
(same units, same scaling, no hFac and no grid-cell area),
event exactly identical when staggerTimeStep=.FALSE.

However, with staggerTimeStep=.TRUE. they will be different.
staggerTimeStep=T sequence:
 a) fill diag: WVELTH  = wVel*(theta(k-1)+theta(k))/2
 b) --> solve momentum and update uVel,vVel,wWel
 c) fill diag: WTHMASS = wVel*(theta(k-1)+theta(k))/2
 d) --> solve tracer equation and update theta, salt

whereas with staggerTimeStep=F:
 a) fill diag: WVELTH  = wVel*(theta(k-1)+theta(k))/2
    fill diag: WTHMASS = wVel*(theta(k-1)+theta(k))/2
 b) --> solve tracer equation and solve momentum 
    and update uVel,vVel,wWel and update theta, salt

So for tracer budget, I would rather use WTHMASS ; but sometime
when trying to evaluate [w'theta']{time-mean}, I might feel more
convenient to use WVELTH.

Cheers,
Jean-Michel

On Sat, Mar 10, 2018 at 03:07:04PM +0100, Paola Cessi wrote:
> I wonder if WTHMASS is already multiplied by the appropriate hfac, while WVELTH is not?
> 
> Paola Cessi
> 
> > On Mar 10, 2018, at 1:06 PM, Martin Losch <Martin.Losch at awi.de> wrote:
> > 
> > Ivana,
> > 
> > have a look at diagnostics_state_fill.F
> > To my eye, the diagnostics WVELTH and WTHMASS are exactly the same.
> > 
> > Martin
> > 
> >> On 10. Mar 2018, at 03:58, Ivana Cerovecki <icerovecki at ucsd.edu> wrote:
> >> 
> >> Hi guys (and girls),
> >> 
> >> I am analyzing output of a model run with a linear free surface,
> >> for which WVELTH was saved, but WTHMASS was not saved.
> >> What is exactly the difference between WVELTH and WTHMASS, 
> >> can I use WVELTH to obtain surface correction and if so, how can I do that? 
> >> 
> >> Can I use WVELTH instead of WTHMASS, the way it is described in 
> >> a document that is attached? Or I just define the surface flux to
> >> be
> >> flux(:,:,1)=WVELTH(:,:,1).*RAC  ?
> >> Any help is highly appreciated!
> >> 
> >> Thank you very much,
> >> cheers,
> >> Ivana
> >> 
> >> 
> >> 
> >> 
> >> http://mitgcm.org/public/r2_manual/latest/online_documents/node269.html
> >> 
> >> 
> >> WTHMASS		Nr	
> >> Vertical Mass-Weight Transp of Pot Temp
> >> WVELTH		Nr	
> >> Vertical Transp of Pot Temp
> >> 
> >> 
> >> <Heat_Salt_Budget_MITgcm.pdf>_______________________________________________
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> > 
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