Opened 10 years ago
Last modified 3 years ago
#29 assigned enhancement
Parameters values : z0_over_height, height_displacement, ct_karman
Reported by: | dsolyga | Owned by: | fcheruy |
---|---|---|---|
Priority: | minor | Milestone: | Not scheduled yet |
Component: | Physical processes | Version: | trunc |
Keywords: | cleaning, constantes | Cc: |
Description
Jan suggested to modify the following parameters values :
- z0_over_height : from 0.0625 to 0.046
- height_displacement : from 0.75 to 0.67
- ct_karman : from 0.35 to 0.40
To note: z0_over_height and height_displacement are externalized, so if needed these parameters can be reset before validation.
See Branches/MergeHydro/logz0_note.
Tests
Sensitivity tests need to be done for evaluation and validation (off-line/coupled).
Change History (8)
comment:1 in reply to: ↑ description Changed 10 years ago by aducharne
comment:2 Changed 10 years ago by peylin
- Owner changed from somebody to jpolcher
- Status changed from new to assigned
comment:3 Changed 5 years ago by jgipsl
height_displacement and ct_karma were changed in revision [3524]. They are now:
height_displacement = 0.66 ct_karman = 0.41
In the same commit, z0_over_height were extened to be dependent of the pft. It is now:
REAL(r_std), PARAMETER, DIMENSION(nvmc) :: z0_over_height_mtc = & ! Factor to calculate roughness height from & (/ 0.0, 0.0625, 0.0625, 0.0625, 0.0625, 0.0625, 0.0625, & !! vegetation height (unitless) & 0.0625, 0.0625, 0.0625, 0.0625, 0.0625, 0.0625 /)
comment:4 Changed 5 years ago by jgipsl
z0_over_height is only used in subroutine condveg_z0cdrag which is only called when rough_dyn=false.
comment:5 Changed 5 years ago by jgipsl
- Cc jpolcher removed
- Milestone changed from ORCHIDEE 2.0 to ORCHIDEE 3.0
- Owner changed from jpolcher to fcheruy
- Version changed from orchidee_1_9_6 to trunc
comment:6 Changed 3 years ago by fcheruy
For now the default for the computation of the roughness lengths is rough_dyn=y and these values are not used. The request could be reconsidered if the default is changed in Orchidee.
The Von Karman constant has been updated already. However in LMDZ it is set to 0.40, I suggest to do the same in Orchidee.
comment:7 Changed 3 years ago by jgipsl
- Milestone changed from ORCHIDEE 3.0 to ORCHIDEE 4.0
Decided during ORCH meeting today:
- Frederique has done simulations with Ionela Musat. She'll add more information in this ticket.
- for short terme: a patch to be done in LMDZ so that q2m never becomes negative
- for longer terme: Nicolas Vuichard would like to look into ROUGH_DYN parametrization to see what can be done. For this part, the ticket is changed to milestone 4.0
comment:8 Changed 3 years ago by luyssaert
- Milestone changed from ORCHIDEE 4.0 to Not scheduled yet
ct_karman is the von Karman constant, established from turbulence similarity analysis.
Its value is usually assumed to close to 0.4, and often set to 0.41
Note that increasing ct_karman will decrease the aerodynamic resistance, thus increase evapotranspiration (ET). It might be a good thing since ET is smaller in ORCHIDEE than in other LSMs in intercomparison projects. It could also help reducing the warm bias over land in teh extra-tropics.
Replying to dsolyga: