[MITgcm-devel] Re: [MITgcm-cvs] MITgcm/pkg/exf CVS Commit

[Martin Losch]

Hi Dimitris,

yes, you are right, but not quite, because seaice_growth.F uses  
ug=sqrt(uwind^2+vwind^2). In order to remove the last dependence on  
uwind and vwind I would opt for uncomment the "CML" lines in  
seaice_growth:
C THERMAL WIND OF ATMOSPHERE
         DO J=1,sNy
          DO I=1,sNx
CML#ifdef SEAICE_EXTERNAL_FORCING
CMLC     this seems to be more natural as we do compute the wind  
speed in
CMLC     pkg/exf/exf_wind.F, but it changes the results
CML          UG(I,J) = MAX(SEAICE_EPS,wspeed(I,J,bi,bj))
CML#else
           SPEED_SQ = UWIND(I,J,bi,bj)**2 + VWIND(I,J,bi,bj)**2
           IF ( SPEED_SQ .LE. SEAICE_EPS_SQ ) THEN
              UG(I,J)=SEAICE_EPS
           ELSE
              UG(I,J)=SQRT(SPEED_SQ)
           ENDIF
CML#endif /* SEAICE_EXTERNAL_FORCING */
          ENDDO
         ENDDO
But that changes the results of lab_sea, plus wspeed is computed from  
stress if #undef ALLOW_ATM_WIND, unless it is read from a file.

In addition I would like exf to prepare all input files (including  
uwind an vwind), in case they are need somewhere.

Here comes the catch: There is something strange going on in  
(exf_wind.F):
           if ( ustar .eq. 0. _d 0 ) then
              us(i,j,bi,bj) = 0. _d 0
           else if ( ustar .lt. ustofu11 ) then
              tmp1 = -cquadrag_2/cquadrag_1/2
              tmp2 = sqrt(tmp1*tmp1 + ustar*ustar/cquadrag_1)
              us(i,j,bi,bj) = sqrt(tmp1 + tmp2)
           else
              tmp3 = clindrag_2/clindrag_1/3
              tmp4 = ustar*ustar/clindrag_1/2 - tmp3**3
              tmp5 = sqrt(ustar*ustar/clindrag_1*
      &            (ustar*ustar/clindrag_1/4 - tmp3**3))
              us(i,j,bi,bj)   = (tmp4 + tmp5)**(1/3) +
      &            tmp3**2 * (tmp4 + tmp5)**(-1/3) - tmp3
           endif
1. If I read the stress compute the wind and then the stress from the  
wind, the new stress is generally much smaller than the original one  
(factor 4 or so)
2. Whereever ustar .ge. ustofu11 (that is, uwind > 11m/s) the results  
wind is much too small, so that it appears that the two formulae do  
not have a smooth transistion. I have not yet figured out why.

Martin

On 8 Mar 2007, at 13:41, Dimitris Menemenlis wrote:

> Martin, I am trying to follow latest mods.  Doesn't this:
>
>> Modified Files:
>> 	seaice_dynsolver.F seaice_ocean_stress.F Log Message:
>> if ALLOW_ATM_WIND is undefined, use the wind stress directly to drive
>> the ice model
>
> remove requirement for this:
>
>> Modified Files:
>> 	exf_wind.F Log Message:
>> put back computation of uwind/vwind from stress from now, because it
>> is needed in seaice. There are doubts about the reliability of this
>> computation.
>
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