[MITgcm-support] what's the difference between _RL and _RS when definite parameters?

[Martin Losch]

Chun-Yan,

the variables and declarations starting with "_" are macros, that are expanded during the cpp step. Compare a .F to a .f file and you'll see that. The macros are mostly defined in model/inc/*.h
by default both _RL and _RS expand into real*8. You you can use a cpp-flag (LET_RS_BE_REAL?) to make _RL expand into real*4 (single precision), you normally you do not need that (and shouldn't have to worry about that)

Sign of uDragTerms: Not sure, but I think the convention in the code is that the "G"-terms are meant to be on the rhs side of the time stepping equation, so u(t+1) = u(t) + Gu(t). In this sense the sign appears correct (drag term reduces u(t+1)). The sign in the documentation does appear to be the other way around. Could be even a bug (in the documentation). Let's see what others say.

Martin


On Mar 28, 2011, at 12:40 PM, Chun-Yan Zhou wrote:

> Hi all,
>  The _RL and _RS seem to be related to parallel system, right? But what's the difference between _RL and _RS?
>  By the way,
>  in the file mom_u_bottomdrag.F as follows, there is "_"in front of the recip_hFacW(i,j,k,bi,bj), what is this signal for? And there is also a minus sign"-" in front of _recip_hFacW, but the formula in 2.14.6 of manual does not have "-". Can anyone help me out? Thanks in advance.
>  
>         uDragTerms(i,j)=
>      &   -_recip_hFacW(i,j,k,bi,bj)*recip_drF(k)
>      &   *(
>      &      2.*KappaRU(i,j,kDownC)*rdrckp1*viscFac
> #ifdef ALLOW_BOTTOMDRAG_CONTROL
>      &     + bottomdragfld(i,j,bi,bj)*dragFac
> #else
>      &     + bottomDragLinear*dragFac
> #endif
>      &    )*(1.-maskDown)*uFld(i,j)
>  
>  
> Chunyan Zhou
> Division of Civil Engineering
> School of Engineering, Physics and Mathematics
> College of Art, Science and Engineering
> Fulton Building
> University of Dundee
> Dundee DD1 4HN
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> 
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