Opened 4 years ago

Last modified 10 months ago

#1967 assigned Defect

Noise on vertical velocities when using UBS momemtum advection scheme

Reported by: ctlod Owned by: gm
Priority: normal Milestone: Unscheduled
Component: OCE Version:
Severity: minor Keywords:
Cc: Branch review:
MP ready?: Task progress:



Under few circumstances, that have to be clarified, noise on vertical velocities arises when using the UBS momentum advection scheme.
It has been observed in several configurations with various horizontal resolution (¼°, 1/12°). This noise seems to develop
close to sharp shelves and then expands offshore along either i or/and j grid direction. The attached figure illustrates this behavior in
a regional configuration over the Arctic basin. It represents a monthly mean vertical velocity field around 700m depth.
The noise emerges clearly in the Arctic area and is less visible within the north Atlantic region.


The origin of this noise is not yet identified and may also not be systematic.
It looks like the implicit viscosity associated to this scheme is not working or is not strong enough; yet the algorithm
itself may not be the source of the problem since 2 configurations using exactly the same module dynadv_ubs.F90
have different behavior: one with noise while the other without.
Below, a list of options that may not be responsible for this noise (deduced from an inter-comparison of 4 configurations namelist and CPP keys) :

  • the non linear free surface (VVL) or linear free surface
  • Partial or full steps
  • ln_logyer
  • ln_bfrimp
  • advective and/or diffusve BBL
  • GLS or TKE
  • Non Penetrative Convection (NPC) or Enhenced Vertical Diffusion (EVD)


No fix for the moment.

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Attachments (1)

UBS_Wnoise_z735m.png (563.3 KB) - added by ctlod 4 years ago.

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Change History (4)

Changed 4 years ago by ctlod

comment:1 Changed 4 years ago by clevy

  • Owner set to gm
  • Status changed from new to assigned
  • Type changed from Bug to Defect

comment:2 Changed 22 months ago by smasson

  • Milestone set to Unscheduled

comment:3 Changed 10 months ago by nemo

  • Version release-3.6 deleted
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