Opened 23 months ago

Last modified 23 months ago

#1984 assigned Bug

Error in the online momentum trend diagnostic

Reported by: Robin_Waldman Owned by: gm
Priority: normal Milestone:
Component: OCE Version: release-3.6
Severity: minor Keywords: Momentum ln_dyn_trd namtrd trends

Description (last modified by nemo)


I am using the online 3D momentum trend diagnostic (ln_dyn_trd = .true.) to compute offline vorticity budgets. The model version is NEMO v3.6, downloaded a few months ago from NEMO website. I am working on a Mediterranean configuration (NEMOMED12).


I have first checked on 1 month of simulation that the total trend stored (utrd_tot and vtrd_tot) corresponded to the sum of individual trend terms (which is the case) and was equal to the actual trend deduced from restart files (un, vn in the restart of the end minus beginning of month). This latter point is not verified. The error is typically low (a few percents) but it can reach very high No image "Ztrend_tot_test_LION.png" attached to Ticket #1984values at localized points on the map, especially at intermediate depths (~70-300m). The error is even larger when computing the curl of the momentum trend in order to retreive the vertical relative vorticity trend.


Changeset r8102 (by Dave Storkey) has recently debugued the online tracer trend diagnostic, in particular by separating between trend contributions in even and odd timesteps. I am thinking that maybe the error on the momentum trend diagnostic also comes from that.

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Change History (6)

comment:1 Changed 23 months ago by nemo

  • Description modified (diff)

comment:2 Changed 23 months ago by clevy

  • Owner set to gm
  • Status changed from new to assigned

comment:3 Changed 23 months ago by Robin_Waldman

I have also saved the instantaneous velocities at the end of January and February instead of extracting un,vn from the restarts. In this case I get a similar (although not same) result: the online trend diagnostic (utrd_tot+utrd_atf) has a typical error of a few percents as compared to the u difference between beginning and end of month.

comment:4 Changed 23 months ago by nemo

  • Keywords trends added; trend removed

comment:5 Changed 23 months ago by nemo

  • Keywords release-3.6* added

comment:6 Changed 23 months ago by nemo

  • Keywords release-3.6* removed
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