[MITgcm-devel] inconsistencies with density conversion

[Jean-Michel Campin]

Hi Ian,

few comments:
1) the 3 other defaults (in several data.seaice) I had in mind were:
# for backward compatibility only:
 SEAICE_cpAir       = 1.0039560439560439e+03,
 SEAICE_lhSublim    = 2.8340219780219775e+06,
 SEAICE_rhoAir      = 1.3E0,

2) would be good to allow > 24.h between step.1 and step.2, so that we 
would get most of the testreport results.
 (and for west-coast people, if we can avoid to check-in things between
  mid-night and 1.am Eastern time, this the time when the daily tag is done
  + when most of the automatic test download the code).

3) renaming variables/CPP-options could be done separately from the 2 other 
 steps. 

4) not so much in favour of changing rhoConstFresh default, at least not
 now. But can re-consider it later.
 And if some of the experiment which will need updated output
 don't have rhoConstFreh set to a good value, it can be added in "data"

Cheers,
Jean-Michel

On Tue, Apr 19, 2011 at 11:00:04AM -0700, Ian Fenty wrote:
> Devel,
> 
> I will proceed as J-M proposes, first removing ICE2WATR from all the verification data.seaice files and then rewriting the saltFlux equation and, if possible, removing ICE2WATR altogether.  
> 
> I agree with the suggestion to take this as an opportunity to "use other meaningful defaults" and the use more transparent variable names.  
> 
> Specifically, the compile-time parameter SEAICE_SALINITY is misleading because it doesn't need to be defined for a nonzero ice salinity (e.g., SIsal0 specifies a constant ice salinity outside of SEAICE_SALINITY).  Also, Gael is quite right about the name of the run-time parameter SEAICE_salinity being misleading because it is not the seaice bulk salinity one might think, but actually a ratio.  Therefore, I propose changing SEAICE_SALINITY to SEAICE_VARIABLE_SALINITY (making a fixed seaice bulk salinity of SIsal0 the default) and using Gael's suggestion of changing SEAICE_salinity to SIsalFRAC.
> 
> Another example of using 'other meaningful defaults' is rhoConstFresh.  One of the reasons the sea ice salinity bug didn't pop up in budget-closing calculations is that the freshwater reference density is equal to seawater reference density by default.  From set_defaults.F:
> 
> C-- jmc : the default is to set rhoConstFresh to rhoConst (=rhoNil by default)
> C         (so that the default produces same results as before)
> c     rhoConstFresh       = 999.8 _d 0
> 
> And from ini_params.F:
>       IF ( rhoConstFresh .EQ. UNSET_RL ) rhoConstFresh=rhoConst
> 
> Perhaps it is also time to allow the default reference freshwater density to be 999.8 kg/m^3 (the actual freshwater density at about 20 deg C).  If old results need to be reproduced, a different rhoConstFresh value can just be set in 'data'.    rhoConstFresh is used in the bulk formula equations so one would expect that using a more accurate number would reduce errors in EmPmR and buoyancy forcing. 
> 
> what do we think about that? 
> 
> -Ian
> 

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