Opened 8 years ago
Last modified 4 years ago
#1646 assigned Defect
pit falls of choosing parameters in the F-S sigma code — at Version 7
| Reported by: | jamesharle | Owned by: | jamesharle |
|---|---|---|---|
| Priority: | low | Milestone: | |
| Component: | OCE | Version: | v4.0.* |
| Severity: | minor | Keywords: | DOM SCO |
| Cc: | jamesharle |
Description (last modified by jamesharle)
Having had a look at the NOCL set up of a high resolution AMM60 configuraton I've come across a possible pit fall concerning the choice of parameters in the Furner-Siddorn vertical coordinates. See the attached figures of the top grid box depth (e3t) using the Siddorn-Furner sigma coords for hc=150 and hc=50 (50 being the default shipped with NEMO for the AMM12 domain). Spot the discontinuity!
From reading the code - it looks like the fixed surface grid box depth (rn_zs=1m in AMM60) and stretched coordinates come into play at depths > hc. Anything less than the hc depth and we're in pure sigma - so as AMM60 has only 50 wet vertical levels - top grid box (e3t) is going to just under 3m at depths approaching 150m (i.e. hc=150). And that's why hc = 50 looks as it should!
If hc < jpk you'd have the reverse scenario: a very sudden shallowing of the depth of the top grid box.
So I guess the guidance for this is to make hc = jpk (for rn_zs=1m)!
Or more generally hc = jpk * rn_zs
To avoid users selecting inappropriate combinations of these parameters, perhaps 'hc' should be set in the furner-siddorn subroutine and a WARNING issued if it differs from the one in the namelist?
Commit History (0)
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Change History (9)
Changed 8 years ago by jamesharle
Changed 8 years ago by jamesharle
comment:1 Changed 8 years ago by jamesharle
- Owner changed from NEMO team to jamesharle
comment:2 Changed 8 years ago by nicolasmartin
- Keywords DOM added; zgr removed
comment:3 Changed 8 years ago by nicolasmartin
- Keywords domzgr removed
comment:4 Changed 8 years ago by nicolasmartin
- Keywords SCO added; sco removed
comment:5 Changed 7 years ago by clevy
- Cc jamesharle added
- Status changed from new to assigned
comment:6 Changed 7 years ago by nicolasmartin
- Description modified (diff)
comment:7 Changed 5 years ago by jamesharle
- Description modified (diff)
- Severity set to minor
- Version changed from v3.6 to v4.0
