[MITgcm-devel] pkg/exf main options

[Martin Losch]

Hi Jean-Michel,

thanks for disentangling these exf options. As far as I can understand exf, your changes are a step forward! I assume that the TAF recomputations with “useAtmWind” can be fixed with some store directives (for “sh”)?

Martin

> On 24 Jan 2017, at 18:25, Jean-Michel Campin <jmc at mit.edu> wrote:
> 
> Hi all,
> 
> I was looking at the different main options in pkg/exf (in EXF_OPTIONS.h).
> 
> Currently, pkg/exf supports the option of prescribing net radiative
> fluxes while computing turbulent heat flux (latent and sensible) 
> but the reverse can also be useful, meaning a mixed set-up where:
> - we specify turbulent heat flux as well as precip and evap [+ run off].
> and
> - we compute net radiative fluxes (LW & SW) from downward radiative component.
> 
> Apart form adding the loading from files of Sensible and Latent heat flux,
> there are few changes needed to make this works:
> 1) ALLOW_ATM_TEMP has to be defined to compute net heat-flux from 4 components
>  (SW,LW,SH,LW). This feature is not well documented, but does not prevent to
>  implement the new mixed setting.
> 2) EXF_RADIATION and EXF_WIND are called only if ALLOW_BULKFORMULAE is defined.
> This is a problem for this mixed setting implementation because the simplest 
> way to not recompute/overwrite the Sensible and Latent heat fluxes would be 
> to skip the call to EXF_BULKFORMULAE ; this would be also safer since
> atemp & aqh don't need to be read-in for this mixed setting to work.
> 
> A little bit on the side (but related):
> I've recently updated the table of option in EXF_OPTIONS.h
> to reflect the fact that 2 documented combinations (ALLOW_ATM_TEMP defined 
> with ALLOW_BULKFORMULAE undef) are indeed not currently working as assumed.
> In fact, the way pkg/exf works well is when ALLOW_BULKFORMULAE is always
> set according to (EXF_OPTIONS.h, lines 164-167): 
>> #if (defined (ALLOW_ATM_TEMP) || defined (ALLOW_ATM_WIND))
>> # define ALLOW_BULKFORMULAE
>> # undef  ALLOW_BULK_LARGEYEAGER04
>> #endif
> 
> So, I propose to make the following changes:
> 1) document what ALLOW_ATM_TEMP does.
> 2) make the call to EXF_RADIATION independent of ALLOW_BULKFORMULAE,
>   always called when ALLOW_DOWNWARD_RADIATION is defined.
>   This is very easy, not much to change, no TAF recomp. issues.
> 3)  make the call to EXF_WIND independent of ALLOW_BULKFORMULAE:
>  From my point of view, this would be nice since it would make
>  wind-stress options available even with simplest buoyancy forcing.
>  This is a little bit more tricky, because I have to move a short piece
>  of code from exf_bulkformulae.F (case ALLOW_ATM_TEMP undef) to exf_wind.F
>  and the replacement of ALLOW_ATM_WIND with run-time parameter "useAtmWind"
>  introduces some TAF recomputations (as a quick fix, I can avoid this 
>  problem by using again the CPP option ALLOW_ATM_WIND).
> With those changes, the CPP option ALLOW_BULKFORMULAE will only be used
> to call (or not) S/R EXF_BULKFORMULAE.
> 
> Note that none of these proposed changes will affect the 2 most used settings
> (and the only ones tested), i.e., direct sea-surface forcing fluxes
> (like in global_with_exf/) of the full bulk-formulae + downward radiation.
> case (e.g, in lab_sea/).
> 
> Any suggestion/comment ?
> 
> Cheers,
> Jean-Michel
> 
> _______________________________________________
> MITgcm-devel mailing list
> MITgcm-devel at mitgcm.org
> http://mitgcm.org/mailman/listinfo/mitgcm-devel