[MITgcm-devel] ocean_emissivity consistency

[Jean-Michel Campin]

Hi Dimitris,

I think some constants are "constant" enough that having them set
in model/src make sense. I tried a long time ago to put some
in COMMON /PARM_ATM/ (PARAMS.h), like celsius2K, but it did not
propagate as default for other pkg (exf is using cen2kel, set to
a different value), may be because it was not possible to change
it in file "data" ?
In the same way, stefanBoltzmann, Latent heat (fusion, evap), 
air heat capacity (this one is already there: atm_Cp) could be 
defined in PARAMS.h

But regarding albedo, since it can be computed in many different
ways (fct of temp/age of snow, zenit angle ...), it's less clear to me 
what benefit we would get from setting some default in model/src.
The drag coeffs are not so universal neither (are they ?) but
some surface emissivities might be. My point here is that if
one constant is used only once to computed a derived quantity 
(e.g., a flux), it's probably better to keep it in the pkg
which compute this flux.

The case of SEAICE_waterAlbedo is little bit different, and
would be better to have it set to UNSET_RL in case we use
pkg/exf, and stop if it set (in data.seaice) to something else.

Cheers,
Jean-Michel

On Mon, Dec 19, 2011 at 08:35:17AM -0800, Menemenlis, Dimitris (3248) wrote:
> Just thinking aloud: I wonder whether parameters that are common to more than one package, e.g., albedos, drag coefficients, emissivities, latent heats, should (eventually) all acquire default values from model/src/set_defaults.F?
> 
> More than once I have seen folks adjust parameters in packages where they never get used, e.g., ocean albedo in pkg/seaice when it is really obtained from pkg/exf.
> 
> If you agree that this is a problem, we could start this set_default.F behavior with emissivity, and then slowly propagate to other variables ...
> 
> Dimitris Menemenlis
> 
> On Dec 19, 2011, at 8:25 AM, Jean-Michel Campin wrote:
> 
> > Hi Martin,
> > 
> > I know this long-wave surface thing can be mis-leading 
> > (in AIM, I think there is only one surface emissivity, and 
> > when using thsice, not sure that we check if everything is
> > consistent, but all can be set as run-time params and made
> > consistent).
> > Since this has been in place for long time, I propose to wait 
> > a little bit for others feedback on this issue.
> > But it would be good to fix this at some point.
> > 
> > Cheers,
> > Jean-Michel
> 
> 
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