[MITgcm-devel] ICE workshop - recap and homework!

[Hong Zhang]

Martin Losch wrote:
> Hi Hong,
>
> this is something I introduced. It really should be the default, because without this flag, you will not be able to get a consistent long wave radiation budget. See this thread:
> <http://mitgcm.org/pipermail/mitgcm-devel/2011-December/005079.html>
> especially:
> <http://mitgcm.org/pipermail/mitgcm-devel/2011-December/005080.html>
> I am not surprised that it leads to different ice thicknesses, because the flag changes the radiation budget. You might be able to recover somethings similar as before with setting the ice_emissivity=0.97 in data.exf. Now you use the default, which is 0.95
>
>   
Hi Martin,
thanks for the reply and the clarification.
In addition to ice_emissivity (0.97 or 0.95) in seaice_solve4temp.F,
another piece of code could cause the difference with this flag
is exf_radiation.F
>             lwflux(i,j,bi,bj) =
>      &          ocean_emissivity*stefanBoltzmann*
>      &          ((theta(i,j,k,bi,bj)+cen2kel)**4)
>      &          - lwdown(i,j,bi,bj)
> #ifdef EXF_LWDOWN_WITH_EMISSIVITY
>      &           *ocean_emissivity  !!!0.97
> C     the lw exitance (= out-going long wave radiation) is
> C     emissivity*stefanBoltzmann*T^4 + rho*lwdown, where the
> C     reflectivity rho = 1-emissivity for conservation reasons:
> C     the sum of emissivity, reflectivity, and transmissivity must be
> C     one, and transmissivity is zero in our case (long wave radiation
> C     does not penetrate the ocean surface)
> #endif /* EXF_LWDOWN_WITH_EMISSIVITY */
I'll try to see if we could recover the old result
by just changing ice_emissivity without touching the code above.

cheers
hong