[MITgcm-support] Relaxation constant for salinity, tauSaltClimRelax in Global Ocean Simulation at 4deg resolution.

[Krishnakumar Rajagopalan]

Hi David,

Thanks a lot for your comments.

As you pointed out the units of ds/dt and  (1/tauSaltClimRelax)*(theta - theta*) 
are inconsistent.  I only wanted to suggest a relationship between 
(theta-theta*) and salinity.

Regards

Krishnakumar





________________________________
From: David Ferreira <dfer at mit.edu>
To: mitgcm-support at mitgcm.org
Sent: Tue, September 21, 2010 5:38:20 PM
Subject: Re: [MITgcm-support] Relaxation constant for salinity, tauSaltClimRelax 
in Global Ocean Simulation at 4deg resolution.

 Hi Krishnakumar,

My question is regarding the           relaxation constant for salinity in the 
tutorial           (tutorial_global_oce_latlon). In the case of potential           
temperature, we calculated the tauThetaClimRelax according to           the           
publication by Barnier et. al(Barnier et.           al :  Thermal forcing for a 
global           ocean circulation model using a three-year climatology of           
ECMWF analyses,           Journal of Marine Systems, 1995.) and are getting 
values in           the range of 60days, which is also the value chosen in  
tutorial. 

>For salinity, however, I am unable to get hold of any           
>reference/publication which discusses in detail the           calculation of           
>tauSaltClimRelax. Please let me know how this quantity           
>(tauSaltClimRelax) could be           calculated.
>
There is no physical justification to tauSaltClimRelax. The non-physical       
justification is that it "works", i.e it keeps the solution close       to S* 
(usually some observed climatology).
 

>Finally, I feel that the net fresh water surface flux, EmPmR,           would 
>depend primarily on temperature than on salinity. If           true, the 
>relaxation term in the salinity equation could look           like,
>
>dS/dt= (1/tauSaltClimRelax)*(theta - theta*) + flux (T*,S*)
>
This looks very strange. It doesn't have the right dimension. Also,     even if 
evaporation could be approximated as a function of SST, it     is less clear for 
precipitation. 


rather than
>
>dS/dt=(1/tauSaltClimRelax)*(S-S*) + flux(S*)
>
>But then, I am not sure whether the salinity solution would           converge 
>to S*. And of course the determination of           tauSaltClimRelax would still 
>require some reference. 
>
>
>


      
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