Unphysical values of ice age in SI3.

[skeeley]

Context

Ice age field in SI3 is producing NaN after some time.

Analysis

We suspect this may be similar to the problem seen in LIM3 in ticket #1508. Before the change the limthd.F90 had

      oa_i(:,:,:) = oa_i(:,:,:) + a_i(:,:,:) * rdt_ice /rday

which has changed to:

      DO jl  = 1, jpl
         DO jj = 1, jpj
            DO ji = 1, jpi
               rswitch = MAX( 0._wp , SIGN( 1._wp, a_i_b(ji,jj,jl) - epsi10 ) )
               oa_i(ji,jj,jl) = rswitch * oa_i(ji,jj,jl) * a_i(ji,jj,jl) / MAX( a_i_b(ji,jj,jl), epsi10 )
            END DO
         END DO
      END DO

but as far as we can see this change (and other changes in rev 5202) never made it to SI3.

Recommendation

Do the changes from LIM3 need to be propagated in SI3 or are we missing something?

[clem]

Ice age is a bit tricky.
I had to change a couple of routines to make it work (I think). The main issue comes from the advection scheme Ultimate-Macho which produces abnormal values that propagate into the domain. This is due to the definition of the ice age that we chose. It is surface based: o_i * a_i and not volume based: o_i * v_i. It seems that the other advection scheme available in the code (Prather) is not impacted and works fine.
So, I cheated a bit but with the new routines (attached) you should be able to have an OK ice age (at least compared to what Prather is doing).

Note: ice age is just a diagnostic that has no impact on the simulations, so I removed its calculation if the output is not requested.

[skeeley]

Thanks Clem.
Will get testing the code on Monday and will keep you posted.

[skeeley]

Seems to be working - now getting physical values for ice age after 10 months of a run.
If we switch ice age off in the io we are still writing a physical (but I guess meaningless) value of ice age into the restart.
Thanks for all your help with this!

[clem]

In 10785:

Error: Failed to load processor CommitTicketReference

No macro or processor named 'CommitTicketReference' found

[clem]

In 10786:

Error: Failed to load processor CommitTicketReference

No macro or processor named 'CommitTicketReference' found