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+Add LANGMUIR_STOKES_BACKGROUND runtime parameter
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  Added three new runtime parameters (LANGMUIR_STOKES_BACKGROUND,
SURFBAND_MIN_THICK_AVG and SURFBAND_OVERRIDE_LAND_SPEED) to replace previously
hard-coded dimensional parameter in the Langmuir number and Stokes drift
calculations. By default all answers are bitwise identical, but there are new
runtime parameters in some MOM_parameter_doc.all files.
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@Hallberg-NOAA
Hallberg-NOAA committed Jan 2, 2023
1 parent 890f84d commit 7cf89e0
Showing 1 changed file with 26 additions and 10 deletions.
36 changes: 26 additions & 10 deletions src/user/MOM_wave_interface.F90
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Original file line number Diff line number Diff line change
Expand Up @@ -125,6 +125,9 @@ module MOM_wave_interface
!! 1 if average value of Stokes drift over level.
!! If advecting with Stokes transport, 1 is the correct
!! approach.
real :: Stokes_min_thick_avg !< A layer thickness below which the cell-center Stokes drift is
!! used instead of the cell average [Z ~> m]. This is only used if
!! WAVE_INTERFACE_ANSWER_DATE < 20230101.
! Options if WaveMethod is Surface Stokes Drift Bands (1)
integer :: PartitionMode !< Method for partition mode (meant to check input)
!! 0 - wavenumbers
Expand All @@ -137,6 +140,9 @@ module MOM_wave_interface

! Options if using FMS DataOverride Routine
character(len=40) :: SurfBandFileName !< Filename if using DataOverride
real :: land_speed !< A large Stokes velocity that can be used to indicate land values in
!! a data override file [L T-1 ~> m s-1]. Stokes drift components larger
!! than this are set to zero in data override calls for the Stokes drift.
logical :: DataOver_initialized !< Flag for DataOverride Initialization

! Options for computing Langmuir number
Expand Down Expand Up @@ -177,11 +183,13 @@ module MOM_wave_interface
!! Horizontal -> V points
!! 3rd dimension -> Freq/Wavenumber

real :: La_min = 0.05 !< An arbitrary lower-bound on the Langmuir number [nondim].
real :: La_min !< An arbitrary lower-bound on the Langmuir number [nondim].
!! Langmuir number is sqrt(u_star/u_stokes). When both are small
!! but u_star is orders of magnitude smaller, the Langmuir number could
!! have unintended consequences. Since both are small it can be safely
!! capped to avoid such consequences.
real :: La_Stk_backgnd !< A small background Stokes velocity used in the denominator of
!! some expressions for the Langmuir number [L T-1 ~> m s-1]

! Parameters used in estimating the wind speed or wave properties from the friction velocity
real :: VonKar = -1.0 !< The von Karman coefficient as used in the MOM_wave_interface module [nondim]
Expand Down Expand Up @@ -390,6 +398,10 @@ subroutine MOM_wave_interface_init(time, G, GV, US, param_file, CS, diag, restar
units='m', default=50.0, scale=US%m_to_Z)
case (SURFBANDS_STRING)! Surface Stokes Drift Bands
CS%WaveMethod = SURFBANDS
call get_param(param_file, mdl, "SURFBAND_MIN_THICK_AVG", CS%Stokes_min_thick_avg, &
"A layer thickness below which the cell-center Stokes drift is used instead of "//&
"the cell average. This is only used if WAVE_INTERFACE_ANSWER_DATE < 20230101.", &
units="m", default=0.1, scale=US%m_to_Z) !, do_not_log=(CS%answer_date>=20230101))
call get_param(param_file, mdl, "SURFBAND_SOURCE", TMPSTRING2, &
"Choice of SURFACE_BANDS data mode, valid options include: \n"//&
" DATAOVERRIDE - Read from NetCDF using FMS DataOverride. \n"//&
Expand All @@ -403,6 +415,11 @@ subroutine MOM_wave_interface_init(time, G, GV, US, param_file, CS, diag, restar
CS%DataSource = DATAOVR
call get_param(param_file, mdl, "SURFBAND_FILENAME", CS%SurfBandFileName, &
"Filename of surface Stokes drift input band data.", default="StkSpec.nc")
call get_param(param_file, mdl, "SURFBAND_OVERRIDE_LAND_SPEED", CS%land_speed, &
"A large Stokes velocity that can be used to indicate land values in "//&
"a data override file. Stokes drift components larger than this are "//&
"set to zero in data override calls for the Stokes drift.", &
units="m s-1", default=10.0, scale=US%m_s_to_L_T)
case (COUPLER_STRING)! Reserved for coupling
CS%DataSource = COUPLER
! This is just to make something work, but it needs to be read from the wavemodel.
Expand Down Expand Up @@ -480,6 +497,10 @@ subroutine MOM_wave_interface_init(time, G, GV, US, param_file, CS, diag, restar
"but is likely only encountered when the wind is very small and "//&
"therefore its effects should be mostly benign.", &
units="nondim", default=0.05)
call get_param(param_file, mdl, "LANGMUIR_STOKES_BACKGROUND", CS%La_Stk_backgnd, &
"A small background Stokes velocity used in the denominator of some "//&
"expressions for the Langmuir number.", &
units="m s-1", default=1.0e-10, scale=US%m_s_to_L_T, do_not_log=(CS%WaveMethod==LF17))

! Allocate and initialize
! a. Stokes driftProfiles
Expand Down Expand Up @@ -688,7 +709,6 @@ subroutine Update_Stokes_Drift(G, GV, US, CS, h, ustar, dt, dynamics_step)
! Local Variables
real :: Top, MidPoint, Bottom ! Positions within the layer [Z ~> m]
real :: level_thick ! The thickness of each layer [Z ~> m]
real :: min_level_thick_avg ! A minimum layer thickness for inclusion in the average [Z ~> m]
real :: DecayScale ! A vertical decay scale in the test profile [Z ~> m]
real :: CMN_FAC ! A nondimensional factor [nondim]
real :: WN ! Model wavenumber [Z-1 ~> m-1]
Expand All @@ -700,9 +720,6 @@ subroutine Update_Stokes_Drift(G, GV, US, CS, h, ustar, dt, dynamics_step)

if (CS%WaveMethod==EFACTOR) return

! The following thickness cut-off would not be needed with the refactoring marked with '###' below.
min_level_thick_avg = 1.e-3*US%m_to_Z

if (allocated(CS%US_x) .and. allocated(CS%US_y)) then
call pass_vector(CS%US_x(:,:,:),CS%US_y(:,:,:), G%Domain)
endif
Expand Down Expand Up @@ -764,7 +781,7 @@ subroutine Update_Stokes_Drift(G, GV, US, CS, h, ustar, dt, dynamics_step)
MidPoint = Top - 0.5*level_thick
Bottom = Top - level_thick
! -> Stokes drift in thin layers not averaged.
if (level_thick>min_level_thick_avg) then
if (level_thick > CS%Stokes_min_thick_avg) then
do b = 1,CS%NumBands
if (CS%PartitionMode == 0) then
! In wavenumber we are averaging over level
Expand Down Expand Up @@ -816,7 +833,7 @@ subroutine Update_Stokes_Drift(G, GV, US, CS, h, ustar, dt, dynamics_step)
MidPoint = Top - 0.5*level_thick
Bottom = Top - level_thick
! -> Stokes drift in thin layers not averaged.
if (level_thick>min_level_thick_avg) then
if (level_thick > CS%Stokes_min_thick_avg) then
do b = 1,CS%NumBands
if (CS%PartitionMode == 0) then
! In wavenumber we are averaging over level
Expand Down Expand Up @@ -1060,7 +1077,7 @@ subroutine Surface_Bands_by_data_override(Time, G, GV, US, CS)
! Filter land values
do j = G%jsd,G%jed
do i = G%Isd,G%Ied
if ((abs(temp_x(i,j)) > 10.0*US%m_s_to_L_T) .or. (abs(temp_y(i,j)) > 10.0*US%m_s_to_L_T)) then
if ((abs(temp_x(i,j)) > CS%land_speed) .or. (abs(temp_y(i,j)) > CS%land_speed)) then
! Assume land-mask and zero out
temp_x(i,j) = 0.0
temp_y(i,j) = 0.0
Expand Down Expand Up @@ -1186,8 +1203,7 @@ subroutine get_Langmuir_Number( LA, G, GV, US, HBL, ustar, i, j, h, Waves, &
! This expression uses an arbitrary lower bound on Langmuir number.
! We shouldn't expect values lower than this, but there is also no good reason to cap it here
! other than to prevent large enhancements in unconstrained parts of the curve fit parameterizations.
! Note the dimensional constant background Stokes velocity of 10^-10 m s-1.
LA = max(Waves%La_min, sqrt(US%Z_to_L*ustar / (LA_STK + 1.e-10*US%m_s_to_L_T)))
LA = max(Waves%La_min, sqrt(US%Z_to_L*ustar / (LA_STK + Waves%La_Stk_backgnd)))
endif

if (Use_MA) then
Expand Down

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