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LM4-NUOPC-driver

This is the repository for the NUOPC driver of the GFDL Land Model version 4 (LM4), for use in the Unified Forecast System

LM4 itself is a submodule of this repository. More information and the LM4 project code is made available through GitHub at https://github.com/NOAA-GFDL/LM4, but is managed by NOAA-GFDL at https://gitlab.gfdl.noaa.gov.

Supported grids and resolutions

Currently in development, only the global C96 grids are supported

Namelist Options

namelist options for tests are set tests/parm/input_datm_lm4.nml.IN

It adds the namelist lm4_nml, along with several LM4 and a couple FMS coupler / flux exchange namelists

Defaults for the lm4_nml if not specified in the run directory input.nml are:

  lm4_debug   = 0           ! debug flag for lm4 (0=off, 1=low, 2=high)
  npx         = 0, npy = 0  ! for FMS domain
  ntiles      = 0           ! cubed sphere tiles
  layout(2)   = (/0,0/)     ! layout for decompostition
  grid        = 'none'
  blocksize   = -1          ! for FMS domain blocking
  dt_lnd_slow = 86400       ! time step for slow land processes (s)
  restart_interval = (/ 0, 0, 0, 0, 0, 0/) ! The time interval that write out intermediate restart file.
                                           ! The format is (yr,mo,day,hr,min,sec).  When restart_interval
                                           ! is all zero, no intermediate restart file will be written out

Additional, flux_exchange_nml and atmos_prescr_nml are existing namelists in input.nml at GFDL, and are needed by LM4 in UFS. They have been brought back in, only for the options used in LM4, and are read in by the land model.

  • flux_exchange_nml has the option z_ref_heat, the reference height for for temperature and relative humidity diagnostics (default 2 m )

  • atmos_prescr_nml has the options:

    • gust_to_use computed or prescribed gust for LM4 boundary layer ( default computed)
    • gustiness wind gustiness (default 5.0 m/s)
    • gust_min minimum gustiness used in computed gust calculation (default 0.0 m/s)

  • Finally surface_flux_nml is used by LM4 UFS. It's options are:

    logical :: no_neg_q              = .false. !< If a_atm_in (specific humidity) is negative (because of numerical truncation),
    !! then override with 0.0
    logical :: use_virtual_temp      = .true.  !< If .TRUE., use virtual potential temp to calculate the stability of the surface
    !! layer.  If .FALSE., use potential temp.
    logical :: alt_gustiness         = .false. !< An alternaive formulation for gustiness calculation.  A minimum bound on the wind
    !! speed used influx calculations, with the bound equal to gust_const
    logical :: old_dtaudv            = .false. !< The derivative of surface wind stress with respect to the zonal wind and meridional
    !! wind are approximated by the same tendency
    logical :: use_mixing_ratio      = .false. !< An option to provide capability to run the Manabe Climate form of the surface flux
    !! (coded for legacy purposes).
    real    :: gust_const            =  1.0 !< Constant for alternative gustiness calculation
    real    :: gust_min              =  0.0 !< Minimum gustiness used when alt_gustiness is .FALSE.
    logical :: ncar_ocean_flux       = .false. !< Use NCAR climate model turbulent flux calculation described by Large and Yeager,
    !! NCAR Technical Document, 2004
    logical :: ncar_ocean_flux_orig  = .false. !< Use NCAR climate model turbulent flux calculation described by Large and Yeager,
    !! NCAR Technical Document, 2004, using the original GFDL implementation, which
    !! contains a bug in the specification of the exchange coefficient for the sensible
    !! heat.  This option is available for legacy purposes, and is not recommended for
    !! new experiments.
    logical :: raoult_sat_vap        = .false. !< Reduce saturation vapor pressure to account for seawater
    logical :: do_simple             = .false.

In tests/parm/input_datm_lm4.nml.IN, these options are set to:

&lm4_nml
      lm4_debug = 1
      grid = 'CS'
      layout = @[INPES],@[JNPES]
      npx = @[NPX]
      npy = @[NPY]
      ntiles = 6
      blocksize = -1
      dt_lnd_slow = 3600
      restart_interval = 0,0,0,6,0,0
/

&surface_flux_nml
      alt_gustiness = .TRUE.
      !gust_min      = 0.0    ! m/s, min. gustiness used when alt_gustiness is .FALSE.
/

&atmos_prescr_nml
  gust_to_use  = 'prescribed'
      !gustiness    = 5.0     ! m/s, wind gustiness if gust_to_use = 'prescribed'
      !gust_min     = 0.01    ! m/s, min. gustiness when gust_to_use = 'computed'
/

Restarts

LM4 uses FMS to write and read restarts.

  • The following restart files are needed generated in the RESTART directory, and needed in the INPUT directory for a warm start
  cana.res.tile{1..6}.nc 
  glac.res.tile{1..6}.nc 
  lake.res.tile{1..6}.nc 
  land.res.tile{1..6}.nc 
  snow.res.tile{1..6}.nc 
  soil.res.tile{1..6}.nc 
  vegn1.res.tile{1..6}.nc
  vegn2.res.tile{1..6}.nc
  landuse.res

Intermediate restarts can be generate during the model run with the lm4_nml name list option:

restart_interval = Y,M,D,h,m,s in input.nml

The default is restart_interval = 0,0,0,6,0,0, ie, 6 hourly

Note that LM4.0 will not restart accurately unless restarts are at time 00z

Fast and Slow Land Timesteps

LM4 has fast and slow processes.

  • The fast timestep is obtained from the NUOPC run sequence.
  • The slow timstep is currently set by a namelist option in lm4_nml. The default is: dt_lnd_slow = 3600

Running with regression tests

There are currently 2 Data-atmosphere tests:

  • datm_cdeps_lm4_c96_gswp3

    • 48 hr test from 2000-01-01 00:00 with a cold start
    • using CDEPS with GSWP3 forcing

  • datm_cdeps_lm4_c96_gswp3_rst

    • a 24 hr restart test from 2000-01-02 00:00
    • warm start using restarts from datm_cdeps_lm4_c96_gswp3

For both, the LM4 restart files listed above are used for comparisons

These tests use the following unique files:

export UFS_CONFIGURE="ufs.configure.atm_lm4.IN"
export FV3_RUN="lm4_run.IN"
export DIAG_TABLE="diag_table_datm_lm4"
export FIELD_TABLE_ADDITIONAL=field_table_lm4
export INPUT_NML="input_datm_lm4.nml.IN"

Imports and Exports

The following are current import and export variables used for data atmosphere

Import Description Variable Name
Sa_z Bottom layer height lm4_model%atm_forc%z_bot
Sa_tbot Bottom layer temperature lm4_model%atm_forc%t_bot
Sa_pbot Bottom layer pressure lm4_model%atm_forc%p_bot
Sa_u Bottom layer zonal wind lm4_model%atm_forc%u_bot
Sa_v Bottom layer meridional wind lm4_model%atm_forc%v_bot
Sa_shum Bottom layer specific humidity lm4_model%atm_forc%q_bot
Sa_pslv Surface pressure lm4_model%atm_forc%p_surf
Faxa_lwdn Mean surface downward longwave radiation lm4_model%atm_forc%flux_lw
Faxa_swvdf Mean surface downward UV+visible diffuse flux lm4_model%atm_forc%flux_sw_down_vis_dif
Faxa_swvdr Mean surface downward UV+visible direct flux lm4_model%atm_forc%flux_sw_down_vis_dir
Faxa_swndf Mean surface downward NIR diffuse flux lm4_model%atm_forc%flux_sw_down_nir_dif
Faxa_swndr Mean surface downward NIR direct flux lm4_model%atm_forc%flux_sw_down_nir_dir
Export Description Variable Name
Sl_lfrin Land fraction for mediator lnd%sg_landfrac

Surface boundary layer and connection to Land

TODO: brief overview of call order:

      call sfc_boundary_layer(real(sec), lm4_model)
      call update_atmos_model_down(lm4_model)              ! for gust calculation with data atmosphere
      call flux_down_from_atmos(real(sec), lm4_model)