possible bug: MITgcm_ocean potential temperature

[hkershaw-brown]

The mitgcm_ocean model_mod interpolates qty_temperature directly (no conversion from potential temp)

DART/models/MITgcm_ocean/model_mod.f90

Line 639 in 2d5882c

subroutine model_interpolate(state_handle, ens_size, location, quantity, interp_val, istatus)

The model appears to use potential temperature in the state:

DART/models/MITgcm_ocean/work/input.nml

Lines 190 to 191 in 2d5882c

	mitgcm_variables = 'PSAL', 'QTY_SALINITY', 'NA', 'NA', 'update',
	'PTMP', 'QTY_TEMPERATURE', 'NA', 'NA', 'update',

DART/models/MITgcm_ocean/trans_mitdart_mod.f90

Lines 382 to 383 in 2d5882c

	TVarID = define_variable(ncid,"PTMP", nf90_real, all_dimids, MITgcm_3D_FIELD)
	call add_attributes_to_variable(ncid, TVarID, "Potential Temperature", "C", "degrees celsius")

note also potential salinity vs salinity.

Possibly this is just a naming issue with the model state, but I figured I would note this rather than the comment getting buried in
#773