[MITgcm-support] potential density

[Matthew Mazloff]

Hi Bruno,

The goal of potential (or neutral) density is to remove the non- 
dynamically relevant change from adiabatic compression.  Derivatives  
of in situ and potential density should be the same when taken at  
constant pressure -- so sigmaX and sigmaY are equivalent to the  
gradient of potential density.

Sorry, but I still haven't looked into what WRHOMASS is exactly,  
hopefully someone else can answer that one

-Matt




On Mar 23, 2011, at 9:19 AM, Bruno Deremble wrote:

> Hi Matt,
>
> I agree for drhodz. but what about sigmaX and sigmaY that are  
> computed using rhoinsitu? (cf grad_sigma.F) I am probably  
> misunderstanding the meaning of 'rhoinsitu' here.
>
> Thanks
> bruno
>
>>
>> Hi Bruno,
>>
>> Not sure about (U,V,W)RHOMASS -- I would assume those are the
>> transport of in situ density since the model uses in situ density.
>>
>> Derivatives of density (e.g. drhodz) are computed with a local
>> reference pressure -- so they are the gradient of potential (or
>> neutral) density. Therefore I believe sigmax and sigmay are the
>> gradients of pot. density.
>>
>> -Matt
>>
>>
>>
>> On Mar 22, 2011, at 6:20 AM, Bruno Deremble wrote:
>>
>>> Good morning,
>>>
>>> In do_oceanic_phys, are sigmax and sigmay the gradients of
>> potential
>>> density (as stated in the manual in the gmredi section)? I ask
>> this
>>> because they are computed using 'rhoinsitu' which I presume is
>> the
>>> in situ density and not the potential density.
>>>
>>> in the diagnostic package WRHOMASS is associated to Vertical
>>> Transport of Potential Density whereas URHOMASS and VRHOMASS are
>> the
>>> horizontal transport of density. Is it correct in both cases?
>>>
>>> thank you
>>> bruno
>>>
>
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