[MITgcm-support] Confusion about Anelastic Option

[Walters, Gage S.]

Hello all,



I have been trying to do a comparison between a simulation with and without the anelastic formulation and was wondering if someone could clarify a few things.



Looking through the documentation, one implements the anelastic option via rhoRefFile. The deep_anelastic example has this implementation:



# Continuous equation parameters

#-note: rhoRefFile is used to turn on the anelastic formulation

&PARM01

rhoRefFile='rhoLin_x2.bin',

tRefFile='TRefFile.bin',

.

.

rhoConst=1000.,

.

.

eosType='LINEAR',



In this example 'rhoLin_x2.bin' has variable density with depth, whereas 'TRefFile.bin' is a constant temperature profile. If the reference temperature is constant and my EOS is constant, then the 'RhoRef.data' and 'RhoRef.meta' are constant. In fact when you run the example those two files report a density of 999.8 when rhoConst is 1000 and a rhoRefFile is given.



Reading the Fortran code in the MITgcm/model/src/set_ref_state.F file, all rhoRefFile does is set rhoFacC and rhoFacF. I realize that this then scales the density in the adv equations. However, I am confused why this does not change the rho reference of the output. I see that it doesn't do that in the code, so maybe I am misunderstanding the difference between the reference density set from the EOS and the reference density file I give the code.



Is it not fair to do a comparison where



1.       I vary the reference temperature with depth (salinity constant) and use the linear EOS to get my density versus depth.

2.       Use that same density versus depth output from RhoRef.data as my rhoRefFile.bin and turn off my EOS.



Or in the second option do I still need to give it the varying temperature profile AND the varying rhoRefFile.bin.



Some explanation would be greatly appreciated.



All the best,

Gage

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