[Mitgcm-support] RE: Momentum timestep

[mitgcm-support at dev.mitgcm.org]

Do we have to introduce the useCD flag? If so why can't it default to
true, which is closer to how it is now (with no flag)? 

Chris



> -----Original Message-----
> From: Jean-Michel Campin [mailto:jmc at gulf.mit.edu] 
> Sent: Wednesday, April 16, 2003 11:41 AM
> To: support at mitgcm.org
> Subject: Momentum timestep
> 
> 
> Hi,
> 
> I'am going to check-in some changes in the momentum timestepping,
> 1) store u*,v* in gU,V instead of in gu,vNm1 (tracers timestepping is 
>    already done in the same way). This affects several S/R
>    but has no impact on output.
> 2) move the forcing and the CD scheme from mom_fluxform & mom_vecinv 
>    to timestep.F 
> 
> The motivations for (2) are:
>  a) to allow to put the momForcing out of the Adams-Bashforth.
>   (since it seems logical to keep the AB in timestep.F, then 
> the forcing
>    has to follows).
>  b) CD scheme needs to be called after the forcing, so it has 
> to move also.
>    Anyway, uVelD & vVelD are step-forward in mom_cdscheme, 
> and seems logical 
>    to have also this call in timestep.F.
>    Doing like this allows to use the CD scheme with mom_vecinv.
>  c) this open the way for doing the AB on u,v instead of gU,gV.
>   [this improve the energy conservation and was actually used for the 
>    NLFS-conservation paper]
> 
> (2) affects the outputs (at the truncation level) since the sequence 
>   of addition to gU,gV (+Forcing , +Coriolis, + MetricTerm 
> ... ) is modified.
>   (will need to update the output.txt of the high sensitive test exp,
>    glob-ocean-pressure, lab_sea and nat_box)
> 
> Also I propose to add a running flag parameter for the CD-scheme,
>  (useCDscheme) default value =FALSE 
>  This means that when using the CD scheme, 
> "useCDscheme=.TRUE." will have 
>  to be added to the "data" file.
>  (I plan to add "WARNING" when useCDscheme=.TRUE. is missing)
> 
> Any comments ?
> 
> See you,
> 
> Jean-Michel
>