To do surface ocean flux ajustment or flux correction in CESM, the first step is to restore model SST and SSS to observational seasonal climatology in a fully coupled setting. In order to use “restoring” settings in a fully coupled run, the better way is to set pop2 forcing_pt/s_interior_nml instead of forcing_shf/sfwf_nml, which is only for ocean-alone model in regard to “restoring”.
Let’s first check the defualt settings in a forcing_pt/s_interior_nml
/
&forcing_pt_interior_nml
pt_interior_data_inc = 24.
pt_interior_data_renorm = 20*1.
pt_interior_data_type = 'none'
pt_interior_file_fmt = 'bin'
pt_interior_filename = 'unknown-pt_interior'
pt_interior_formulation = 'restoring'
pt_interior_interp_freq = 'every-timestep'
pt_interior_interp_inc = 72.
pt_interior_interp_type = 'linear'
pt_interior_restore_file_fmt = 'bin'
pt_interior_restore_filename = 'unknown-pt_interior_restore'
pt_interior_restore_max_level = 0
pt_interior_restore_tau = 365.
pt_interior_surface_restore = .false.
pt_interior_variable_restore = .false.
/
&forcing_s_interior_nml
s_interior_data_inc = 24.
s_interior_data_renorm = 20*1.
s_interior_data_type = 'none'
s_interior_file_fmt = 'bin'
s_interior_filename = 'unknown-s_interior'
s_interior_formulation = 'restoring'
s_interior_interp_freq = 'every-timestep'
s_interior_interp_inc = 72.
s_interior_interp_type = 'linear'
s_interior_restore_file_fmt = 'bin'
s_interior_restore_filename = 'unknown-s_interior_restore'
s_interior_restore_max_level = 0
s_interior_restore_tau = 365.
s_interior_surface_restore = .false.
s_interior_variable_restore = .false.
/
Explianation:
Check pop2 namelist here
pt_interior_data_renorm
Renormalization constants for components in interior potential temperature forcing file. Default: 20*1.. If the unit of the potenT forcing data is degC, then we set it as a defualt number or as 1.
pt_interior_formulation
Interior potential temperature formulation. Default: ‘restoring’
pt_interior_data_type
Type or periodicity of interior potential temperature forcing.
Valid Values: ‘none’, ‘annual’, ‘monthly’, ‘monthly-equal’, ‘monthly-calendar’, ‘n-hour’
Default: ‘none’
pt_interior_restore_max_level
Maximum level for interior potential temperature restoring. (Default: 0)
pt_interior_restore_tau
Restoring timescale (days) if pt_interior_formulation=’restoring’. (LANL Default: 1e20; CESM Default: 365)
pt_interior_interp_freq
How often to temporally interpolate interior potential temperature data to current time.
Valid Values: ‘never’, ‘n-hour’, ‘every-timestep’
LANL Default: ‘never’
CESM Default: ‘every-timestep’
pt_interior_interp_inc
Increment (hours) between interpolation times if interp_freq=’n-hour’. (Note that this is only for ‘n-hour’ type)
LANL Default: 1e20; CESM Default: 72
pt_interior_data_inc
Increment (hours) between forcing times if pt_interior_data_type=’n-hour’. (Note that this is only for ‘n-hour’ type)
LANL Default: 1e20; CESM Default: 24
e.g. Setting pt_interior_data_type = monthly-calendar and pt_interior_restore_max_level = 1 and pt_interior_restore_tau = 10 means model global SST restored to observational monthly cliamtology with a restoring time scale (or e-floding time scale) of 10 days to a prescribed data settled in pt_interior_filename.
If one is to set different restoring time scales and levels in different regions, or to perform a regional restoring, *pt_interior_variable_restore = true and pt_interior_restore_filename should be set. Note that data settled in pt_interior_restore_filename should be an integer corresponding to the restoring time scale and deepest level you want to mix at (for each point). For a gx3v7 grid, if you want to mix everywhere, you can set it to 60 at every point.
Note:
When I finished pre-processing forcing data and setting the nml, I start running the case but to my surprise, SST and SSS have no change in restoring run compared to the control run, even if I though I did restoring. It puzzled me until I touched someone who encountered the same problem. He told me to modify the one line of the code in forcing_pt/s_interior.F90. Thanks so much to him!
For forcing_pt_interior.F90,
!-----------------------------------------------------------------------
!
! do interior restoring if required (no surface restoring for any)
!
!-----------------------------------------------------------------------
if ((k > 1 .or.pt_interior_surface_restore).and. &
pt_interior_data_type.ne.'none') then
bid = this_block%local_id
This code segment indicates that the model only restore temperature with levels larger than 1. That’s why restoring didn’t work to surface level. The first solution is to include the first level in code. Copy the scripts to {case}/SourcemMods directory and modify the code before compiling the model.
if ((k >= 1 .or.pt_interior_surface_restore).and. &
pt_interior_data_type.ne.'none') then
The second solution is to set the nml from s_interior_surface_restore = .false. to s_interior_surface_restore = .ture.
Now rebuild the model and running the case, we get the restored SST and SSS successfuly!
An other good way for restoring:
CESM air-sea decoupling
Last update: 08/08/2020