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COSIMA / access-om3

ACCESS-OM3 global ocean-sea ice-wave coupled model
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Inconsistent physical constants #53

Open micaeljtoliveira opened 1 year ago

micaeljtoliveira commented 1 year ago

The default values for the latent heat of fusion and the latent heat of evaporation in MOM6 are taken from the corresponding values FMS defined here. On the other hand, when using the CESM coupler, CICE takes the default values from csm_share (see here and here).

Unfortunately these values are inconsistent. CESM solves the problem by replacing the FMS source file with a different one. This approach does not work well for us, as we are treating FMS as an external dependency. Instead, we can set the values in the input (e.g., using the LATENT_HEAT_FUSION and LATENT_HEAT_VAPORIZATION options of MOM6).

aekiss commented 1 year ago

If we set these parameters manually, we need to have some way to check/guarantee they are consistent between model components. Perhaps the payu driver could do this, and abort (or at least warn) if there are inconsistencies?

anton-seaice commented 4 months ago

CICE sets the (initial?) density of sea-water to 1026 km/m3 however MOM uses 1035 kg/m3. In OM2, this only caused an issue with diagnostics.

There is a _SHR_CONSTRHOSW, which could be used by all model components, within the CESM share repository, but MOM doesn't use it

ofa001 commented 4 months ago

Hi @anton-seaice. Yes we had to live with this density difference last time, the MOM ocean one is set in relation to sigma2 levels in the ocean, whilst the ice only interacts with ocean surface density and we set it to retain CICE values, otherwise it would be very strange, in terms of the T/S properties of water it was adjacent too.

ofa001 commented 4 months ago

There are many other parameter differences across ACCESS-CM2 when you account for the parameter settings in the UM/CABLE. I am not sure if there is a plan to rationalise these in warning messages, common space, we did discuss the possibility of doing something for CM2.

MartinDix commented 4 months ago

UM uses 

! latent heat of condensation of water at 0degc
REAL, PARAMETER :: lc                  = 2.501e6
! latent heat of fusion of water at 0degc
REAL, PARAMETER :: lf                  = 0.334e6

lc agrees with the CESM version! At the moment CABLE values are slightly different too.

aekiss commented 3 weeks ago

Earth's radius is also inconsistent between components https://github.com/COSIMA/access-om3/issues/240#issuecomment-2458750489