[MITgcm-devel] merged budget_ice

[Patrick Heimbach]

Hi Ian,
could you address these concerns please
as soon as possible.
Thanks
-Patrick

On Sep 21, 2010, at 12:10 PM, Jean-Michel Campin wrote:

> Hi Ian,
>
> I did not get the confirmation from Gael, but looks like the problem
> he was having (getting NaNs) with the MITgcm_contrib version of
> seaice_growth_if.F is quite similar to what I was getting (division  
> by zero)
> in the same routine. The lines of code where we have a pb are:
> 1268                   IF  (salt(I,J,kSurface,bi,bj) .GE.
> 1269      &               SEAICE_salinity_fixed)  THEN
> 1270
> 1271                      FreshwaterContribFromIce(I,J) =
> 1272      &                  - ActualIceVolumeChange(I,J)*
> 1273      &                  SEAICE_rhoICE/ RHOFW* (ONE -
> 1274      &                  SEAICE_salinity_fixed/salt 
> (I,J,kSurface,bi,bj))
>
> I personally don't understand what this formulation means.
>
> In addition, it introduces a sharp discontinuity around
> salt() = SEAICE_salinity_fixed:
> a) if salt() = -1.e-16 + SEAICE_salinity_fixed, then
>  FreshwaterContribFromIce is the full delta ice-volume
> b) if salt() = SEAICE_salinity_fixed, then
>  FreshwaterContribFromIce = 0 even if there is a large
>  change of ice volume (from melting or freezing)
>
> I have a 3rd remark: did not see any contribution to saltFlux,
> which seems strange for the case where SEAICE_salinity(_fixed) is > 0
>
> Thanks,
> Jean-Michel
>
> On Tue, Sep 21, 2010 at 02:27:07AM -0400, Ian Fenty wrote:
>> Merging SEAICE_BUDGET_ICE and SEAICE_BUDGET_ICE_IF
>>
>> Fenty_Thermo_Code_Updates/code_updates/seaice_budget_ice.F
>>
>> The routine seaice_budget_ice.F is merged with  
>> seaice_budget_ice_if.F in
>> a file which continues to be called seaice_budget_ice.F.  The newly
>> merged routine can use either the original "default" method for
>> calculating fluxes between snow-ice and air by including "#define
>> USE_ORIGINAL_SBI" in SEAICE_OPTIONS.h.
>>
>> The method used in seaice_budget_ice_if.F is set to be the default.
>> Invoking the original flux calculations should give the same  
>> results as
>> using the original seaice_budget_ice routine.  The difference between
>> the two methods is due to 1) alternative formulation of saturation  
>> vapor
>> pressure over the ice 2) truncation errors stemming from  
>> differences in
>> the ordering of some calculation 3) difference in the iterative  
>> search
>> scheme ( the original method uses an approximate derivative of the
>> surface energy balance w.r.t. the snow/ice surface temperature  
>> while the
>> _if codes uses the full derivative.).
>>
>>
>>
>
> _______________________________________________
> MITgcm-devel mailing list
> MITgcm-devel at mitgcm.org
> http://mitgcm.org/mailman/listinfo/mitgcm-devel

---
Patrick Heimbach | heimbach at mit.edu | http://www.mit.edu/~heimbach
MIT | EAPS 54-1518 | 77 Massachusetts Ave | Cambridge MA 02139 USA
FON +1-617-253-5259 | FAX +1-617-253-4464 | SKYPE patrick.heimbach