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#1877 (Issues with NEMO tracer trends diagnostics to be used for CMIP6) – NEMO

Opened 7 years ago

Closed 4 years ago

#1877 closed Enhancement (fixed)

Issues with NEMO tracer trends diagnostics to be used for CMIP6

Reported by: davestorkey Owned by: jcastill
Priority: normal Milestone:
Component: OCE Version: trunk
Severity: minor Keywords: CMIP6 tracer trends
Cc: agn



Before Christmas I did some work on the NEMO tracer trend diagnostics to
ensure that they worked with VVL and that we could use them to recover the
tracer content trend as required by CMIP6. George Nurser has recently
reviewed the code and pointed out a couple of mistakes. In particular the
total trend (ttrd_tot) and (impure) vertical diffusion trend (ttrd_zdf) are currently
formulated to give the trend in the tracer concentration rather than the
tracer content. There is also a problem with the Asselin time-filter trend if
VVL is switched on.

We intend to update the code in 3.6_stable and the trunk to correct this.
However we still have outstanding questions about how the Asselin filter
trend contributes to the sum of trends. George is going to discuss with
Gurvan at Barcelona next week and we will hopefully put in some code updates
shortly after that.





Commit History (5)


Branch to add tracer advection modifications that are already in newer versions of the trunk. The modifications to be included are, in this order: branches/2015/nemo_v3_6_STABLE@8102 branches/2015/nemo_v3_6_STABLE@8305 ticket #1877 (bug fixes) ticket #2004 (bug fixes)


#1911 (ENHANCE-09): PART I.3 - phasing with trunk: tracer trends output (see #1877 trunk change from 86666 to 8698)


Bug fixes for tracer trends diagnostics in trunk. See ticket #1877. These fixes correspond to the changes to the 3.6 branch at revisions 8102 and 8305.


3.6_stable: fix for bug in Asselin filter trend diagnostic. See comment on ticket #1877.


NEMO 3.6_stable: tracer trends diagnostics. See ticket #1877 for more details.

  1. Correct bugs in calculation of total trends and trends due to vertical diffusion.
  2. Output component trends every second timestep so that sum of component trends plus Asselin filter trend equals total trend.
  3. Layer-integrated versions of trends (as per CMIP6 definition) available in field_def.xml.

Change History (14)

comment:1 Changed 7 years ago by clevy

  • Type changed from Bug to Task

comment:2 Changed 7 years ago by davestorkey

Update for nemo_v3_6_STABLE branch at rev 8102. This includes corrections for the bugs to the total trend and the vertical diffusion trend mentioned above. Also the component trends and the Asselin filter trend have been modified so that they are only passed from NEMO to XIOS every second timestep. For the Asselin filter trend there is a lag of one timestep. This ensures that the sum of the component trends plus the Asselin filter trend equals the total trend. The total trend is calculated using the difference (ta - tn), which ensures that the time-mean total trend multiplied by the total integration period equals the model end state minus start state. With this update NEMO passes these two checks to a good degree of accuracy.

Thanks to George and Gurvan for figuring out how to code the trends with the leapfrog timestepping.

comment:3 Changed 7 years ago by davestorkey

There is a bug in the implementation of the Asselin filter trend if VVL is switched on. The trend is calculated in tra_nxt_vvl which is called from NEMO and TOP and the current implementation doesn't take account of this. This can cause the model to pass garbage to XIOS if TOP is switched on. A fix to be implemented shortly.

comment:4 Changed 7 years ago by davestorkey

Asselin filter trend bug fixed in nemo_v3_6_STABLE at revision 8305.

NB. All of these updates to the tracer trends diagnostics are not yet implemented in the trunk. To be done before this ticket is closed.

comment:5 Changed 6 years ago by timgraham

  • Version changed from v3.6 to trunk

As this has been fixed in 3.6 STABLE but not yet fixed in the trunk I've changed the version of the ticket to remind us to fix it.

comment:6 Changed 6 years ago by davestorkey

Bug fixes corresponding to fixes 8102 and 8305 in 3.6_stable branch now committed to the trunk at revision 8698.

Remaining issues (noticed in tests in eORCA1):

  1. The salinity advection and salinity lateral diffusion trends have odd values at the northern and eastern boundaries in both the 3.6 and trunk versions of the code. Possibly missing lbc_lnk calls?
  1. The ttrd_evd_li diagnostic has strange north-south stripes in the 3.6 version of the code, not present in the output from the trunk.

comment:7 Changed 6 years ago by nemo

  • Keywords changed from tracer trends CMIP6 to CMIP6 tracer trends

comment:8 Changed 6 years ago by nemo

  • Keywords Misc. added

comment:9 Changed 6 years ago by nemo

  • Keywords Misc. removed

comment:10 Changed 6 years ago by nicolasmartin

  • Type changed from Task to Enhancement

comment:11 Changed 6 years ago by nicolasmartin

  • Milestone Unscheduled deleted

comment:12 Changed 6 years ago by jcastill

In 9294:

Error: Failed to load processor CommitTicketReference
No macro or processor named 'CommitTicketReference' found

comment:13 Changed 6 years ago by nemo

  • Owner changed from davestorkey to jcastill
  • Status changed from new to assigned

comment:14 Changed 4 years ago by smasson

  • Resolution set to fixed
  • Status changed from assigned to closed
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