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+Add a better variant of add_LOTW_BBL_diffusivity #671

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Jul 10, 2024
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+Add a better variant of add_LOTW_BBL_diffusivity #671

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34 changes: 30 additions & 4 deletions src/parameterizations/vertical/MOM_set_diffusivity.F90
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Original file line number Diff line number Diff line change
Expand Up @@ -157,7 +157,12 @@ module MOM_set_diffusivity
integer :: answer_date !< The vintage of the order of arithmetic and expressions in this module's
!! calculations. Values below 20190101 recover the answers from the
!! end of 2018, while higher values use updated and more robust forms
!! of the same expressions.
!! of the same expressions. Values above 20240630 use more accurate
!! expressions for cases where USE_LOTW_BBL_DIFFUSIVITY is true.
integer :: LOTW_BBL_answer_date !< The vintage of the order of arithmetic and expressions
!! in the LOTW_BBL calculations. Values below 20240630 recover the
!! original answers, while higher values use more accurate expressions.
!! This only applies when USE_LOTW_BBL_DIFFUSIVITY is true.

character(len=200) :: inputdir !< The directory in which input files are found
type(user_change_diff_CS), pointer :: user_change_diff_CSp => NULL() !< Control structure for a child module
Expand Down Expand Up @@ -1426,6 +1431,7 @@ subroutine add_LOTW_BBL_diffusivity(h, u, v, tv, fluxes, visc, j, N2_int, Rho_bo

! Local variables
real :: dz(SZI_(G),SZK_(GV)) ! Height change across layers [Z ~> m]
real :: dz_above(SZK_(GV)+1) ! Distance from each interface to the surface [Z ~> m]
real :: TKE_column ! net TKE input into the column [H Z2 T-3 ~> m3 s-3 or W m-2]
real :: TKE_remaining ! remaining TKE available for mixing in this layer and above [H Z2 T-3 ~> m3 s-3 or W m-2]
real :: TKE_consumed ! TKE used for mixing in this layer [H Z2 T-3 ~> m3 s-3 or W m-2]
Expand Down Expand Up @@ -1500,7 +1506,15 @@ subroutine add_LOTW_BBL_diffusivity(h, u, v, tv, fluxes, visc, j, N2_int, Rho_bo
TKE_column = CS%BBL_effic * TKE_column ! Only use a fraction of the mechanical dissipation for mixing.

TKE_remaining = TKE_column
total_depth = ( sum(dz(i,:)) + GV%dz_subroundoff ) ! Total column thickness [Z ~> m].
if (CS%LOTW_BBL_answer_date > 20240630) then
dz_above(1) = GV%dz_subroundoff ! This could perhaps be 0 instead.
do K=2,GV%ke+1
dz_above(K) = dz_above(K-1) + dz(i,k-1)
enddo
total_depth = dz_above(GV%ke+1)
else
total_depth = ( sum(dz(i,:)) + GV%dz_subroundoff ) ! Total column thickness [Z ~> m].
endif
ustar_D = ustar * total_depth
h_bot = 0.
z_bot = 0.
Expand All @@ -1525,7 +1539,11 @@ subroutine add_LOTW_BBL_diffusivity(h, u, v, tv, fluxes, visc, j, N2_int, Rho_bo

z_bot = z_bot + dz(i,k) ! Distance between upper interface of layer and the bottom [Z ~> m].
h_bot = h_bot + h(i,j,k) ! Thickness between upper interface of layer and the bottom [H ~> m or kg m-2].
D_minus_z = max(total_depth - z_bot, 0.) ! Thickness above layer [H ~> m or kg m-2].
if (CS%LOTW_BBL_answer_date > 20240630) then
D_minus_z = dz_above(K)
else
D_minus_z = max(total_depth - z_bot, 0.) ! Distance from the interface to the surface [Z ~> m].
endif

! Diffusivity using law of the wall, limited by rotation, at height z [H Z T-1 ~> m2 s-1 or kg m-1 s-1].
! This calculation is at the upper interface of the layer
Expand Down Expand Up @@ -2191,7 +2209,7 @@ subroutine set_diffusivity_init(Time, G, GV, US, param_file, diag, CS, int_tide_
"law of the form c_drag*|u|*u. The velocity magnitude "//&
"may be an assumed value or it may be based on the actual "//&
"velocity in the bottommost HBBL, depending on LINEAR_DRAG.", default=.true.)
if (CS%bottomdraglaw) then
if (CS%bottomdraglaw) then
call get_param(param_file, mdl, "CDRAG", CS%cdrag, &
"The drag coefficient relating the magnitude of the "//&
"velocity field to the bottom stress. CDRAG is only used "//&
Expand Down Expand Up @@ -2231,6 +2249,14 @@ subroutine set_diffusivity_init(Time, G, GV, US, param_file, diag, CS, int_tide_
else
CS%use_LOTW_BBL_diffusivity = .false. ! This parameterization depends on a u* from viscous BBL
endif
call get_param(param_file, mdl, "LOTW_BBL_ANSWER_DATE", CS%LOTW_BBL_answer_date, &
"The vintage of the order of arithmetic and expressions in the LOTW_BBL "//&
"calculations. Values below 20240630 recover the original answers, while "//&
"higher values use more accurate expressions. This only applies when "//&
"USE_LOTW_BBL_DIFFUSIVITY is true.", &
default=20190101, do_not_log=.not.CS%use_LOTW_BBL_diffusivity)
!### Set default as default=default_answer_date, or use SET_DIFF_ANSWER_DATE.

CS%id_Kd_BBL = register_diag_field('ocean_model', 'Kd_BBL', diag%axesTi, Time, &
'Bottom Boundary Layer Diffusivity', 'm2 s-1', conversion=GV%HZ_T_to_m2_s)

Expand Down
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