g.e23_a17c.GJRAv4.TL319_t232_zstar_N75.2024.031

[fobryan3]

Test a version of the Ohlmann (2003) shortwave penetration scheme in MOM6, replacing the Manizza scheme.

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See discussion #34 for background motivation.

This version modifies MOM_opacity.F90 to add the new option OPACITY_SCHEME = "OHLMANN_03". It is a simple implementation of the functional form of the parameterization rather than a table lookup as used in POP. If it seems this scheme is the preferred choice a more efficient table lookup approach may be needed.

To be compared to case 2024.030 (75 layer zstar)

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Case directory:

• Locally (if still available):
  /glade/work/bryan/cesm3.runs/g.e23_a17c.GJRAv4.TL319_t232_zstar_N75.2024.031

• On github:
  https://github.com/NCAR/omwg_dev/tree/$CASE

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Sandbox:

• Locally (if still available): /glade/work/gmarques/cesm.sandboxes/cesm2_3_alpha17c

• On github: https://github.com/ESCOMP/cesm/tree/cesm2_3_alpha16c

MOM6 tag: dev/ncar_240311

MOM_interface tag: mi_240311

CICE6 tag: cice_20230707

CESM_CICE tag: cesm_cice6_4_1_10

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Diagnostics:

• Diags (if available):
  TODO

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Output:

• Raw output on derecho (if still available): /glade/derecho/scratch/bryan/archive/$CASE/

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Contacts:
@fobryan3 , @gustavo-marques

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Extra details:
The following included in user_nl_mom
! set OHLMANN_03
OPACITY_SCHEME = "OHLMANN_03"
PEN_SW_NBANDS = 2
! new zstar with 75 layers
NK = 75
ALE_COORDINATE_CONFIG = "FILE:zstar_75layer_2.5m_248.4m-2024-03-29.nc,dz"
! background visc/diff
KD = 0.
KV = 0.
KD_MIN = 2.0E-07
! interp/remap scheme
INTERPOLATION_SCHEME = "PPM_CW"
REMAPPING_SCHEME = "PPM_CW"
VELOCITY_REMAPPING_SCHEME = "PPM_CW"
!!! topo and channel edits !!!
TOPO_EDITS_FILE = "TopoEdit_tx2_3v2_024.nc"
CHANNEL_CONFIG = "list"
CHANNEL_LIST_FILE = "Channels_tx2_3v2_024"
FATAL_UNUSED_CHANNEL_WIDTHS = True
! others
INPUTDIR = "INPUT"
STOCH_EOS=True
STANLEY_COEFF=0.5
USE_STANLEY_PGF=True
USE_STANLEY_ML=True
USE_STANLEY_ISO=True
USE_STANLEY_GM=True
USE_NEUTRAL_DIFFUSION = True
NDIFF_TAPERING = True
KHTR_USE_EBT_STRUCT = True
MEKE_KHTR_FAC = 1.0
DO_GEOTHERMAL = True
GEOTHERMAL_SCALE = 1.0
GEOTHERMAL_FILE = "geothermal_davies2013_tx2_3_20231120_cdf5.nc"
GEOTHERMAL_VARNAME = "geothermal_hf"

[fobryan3]

The impact of the change is generally as expected. The results shown below are from the first year of a cold-start JRA forced case. The profile of penetrating solar output from the model agrees with the analytical form of the parameterization from the paper (black dashed), with larger downwelling irradiance below 2.5m. The solar heating rate (divergence of the flux) in the surface layer is decreased by ~0.2 degC/day.

The mean SST averaged over the first year of the integration is lowered by 0.1 to 0.25 degC in the subtropics of both hemispheres. This is in the desired direction for mitigating SST bias we see in recent coupled runs.

The SST response is entirely in the summer months as expected. There is a small mixed layer deepening that lasts throughout most of the year however. This plot is for the location of the Stratus mooring (85W,20S).

Overall the response magnitude is rather small, but it will be interesting to see if there are amplifying feedbacks in a coupled integration.