[MITgcm-devel] new salt_plume param?

[Gael Forget]

Hi Dimitris,

I am glad that you sympathize with the idea.

I appreciate the capability of turning off pkg/salt_plume by setting
useSALT_PLUME=.TRUE. and PlumeMethod=5. And, in the same 
logic, I see that I could modulate the intensity of saltplumeFlux by 
computing weighted averages of PlumeMethod=5 and the others.

But my suggested code would readily do this for any of the available
PlumeMethod's, at the expense of one code line. 

I don't see why we would want to make it more complicated than that.
I don't see either why applying the proposed factor to saltplumeFlux
in seaice_growth would be an inappropriate place, since this is 
precisely where saltplumeFlux is set. Seems transparent to me.

Anyway, I can leave this out of the main trunk if you prefer.

Cheers,
Gael

On May 27, 2011, at 12:20 AM, Menemenlis, Dimitris (3248) wrote:

> Gael, if I understand your suggestion correctly, you are trying to add a redistribution
> that would leave (1-SaltPlumeIntensity) in the surface level, in addition to whatever
> is left there by the particular "PlumeMethod" that has been selected.
> I think this is a good suggestion but a cleaner way to implement would be to
> add one or more PlumeMethod distributions to salt_plume_frac.F in addition
> to the ones that are already there.  For example, the current PlumeMethod=5
> is  equivalent to your SaltPlumeIntensity=0 and the other PlumeMethod
> distributions all leave behind some percentage of salt in the surface level.
> 
> Another argument against adding a constant SaltPlumeIntensity in seaice_growth.F
> is that conceptually this parameter should not be everywhere constant.  Instead it
> should probably be modulated by the fraction of lateral vs bottom freezing occurring
> in each grid cell at a particular moment in the integration.  Again, salt_plume_frac.F
> would be a better location to carry out such calculation rather than seaice_growth.F
> 
> Dimitris Menemenlis
> 
> On May 26, 2011, at 12:55 PM, Gael Forget wrote:
> 
>> Hi An and co,
>> 
>> my understanding is that the current set of parameters
>> allows various redistribution profiles shape and reach.
>> 
>> I was surprised not to find one to tune, not the shape, 
>> but the very intensity of the parameterization.  Did I miss it?
>> 
>> In my tests I added the following, which seems to provide for an 
>> easy tuning of the salt plume parameterization strength. 
>> I thought it could be of interest to other users. So, do you mind if 
>> I introduce a SaltPlumeEfficiency factor in seaice_growth.F to do
>>            saltPlumeFlux(I,J,bi,bj)=
>>    &            HEFFM(I,J,bi,bj)/SEAICE_deltaTtherm
>>    &            *(1-SIsalFRAC)*salt(I,j,kSurface,bi,bj)
>>    &            *tmpscal1*SEAICE_rhoIce
>>    &            *SaltPlumeIntensity
>> It would range from 0 to 1, and have a default of 1. I believe the 
>> above snippet would be a correct way to do this. Isn't it?
>> 
>> Cheers,
>> Gael
>> 
>> 
>> 
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> 
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