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MOM_CFC_cap cleanup
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remove unused and unneeded local variables

correct unit-related comments

rework CFC_cap_fluxes to better align with Orr et al., GMD, 2017
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@klindsay28
klindsay28 committed Aug 24, 2021
1 parent f6524ad commit 197cd18
Showing 1 changed file with 46 additions and 68 deletions.
114 changes: 46 additions & 68 deletions src/tracer/MOM_CFC_cap.F90
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Original file line number Diff line number Diff line change
Expand Up @@ -84,9 +84,6 @@ function register_CFC_cap(HI, GV, param_file, CS, tr_Reg, restart_CS)
! This include declares and sets the variable "version".
#include "version_variable.h"
real, dimension(:,:,:), pointer :: tr_ptr => NULL()
real :: a11_dflt(4), a12_dflt(4) ! Default values of the various coefficients
real :: d11_dflt(4), d12_dflt(4) ! In the expressions for the solubility and
real :: e11_dflt(3), e12_dflt(3) ! Schmidt numbers.
character(len=200) :: dummy ! Dummy variable to store params that need to be logged here.
logical :: register_CFC_cap
integer :: isd, ied, jsd, jed, nz, m
Expand Down Expand Up @@ -442,11 +439,8 @@ subroutine CFC_cap_fluxes(fluxes, sfc_state, G, US, Rho0, Time, id_cfc11_atm, id

! Local variables
real, dimension(SZI_(G),SZJ_(G)) :: &
CFC11_Csurf, & ! The CFC-11 surface concentrations times the Schmidt number term [mol kg-1].
CFC12_Csurf, & ! The CFC-12 surface concentrations times the Schmidt number term [mol kg-1].
CFC11_alpha, & ! The CFC-11 solubility [mol kg-1 atm-1].
CFC12_alpha, & ! The CFC-12 solubility [mol kg-1 atm-1].
kw_wo_sc_no_term, & ! gas transfer velocity, without the Schmidt number term [Z T-1 ~> m s-1].
kw, & ! gas transfer velocity [Z T-1 ~> m s-1].
cair, & ! The surface gas concentration in equilibrium with the atmosphere (saturation concentration)
! [mol kg-1].
cfc11_atm, & !< CFC11 concentration in the atmopshere [pico mol/mol]
Expand All @@ -456,10 +450,10 @@ subroutine CFC_cap_fluxes(fluxes, sfc_state, G, US, Rho0, Time, id_cfc11_atm, id
real :: alpha_11 ! The solubility of CFC 11 [mol kg-1 atm-1].
real :: alpha_12 ! The solubility of CFC 12 [mol kg-1 atm-1].
real :: sc_11, sc_12 ! The Schmidt numbers of CFC 11 and CFC 12.
real :: sc_no_term ! A term related to the Schmidt number.
real :: kw_coeff ! A coefficient used to scale the piston velocity [Z T-1 T2 L-2 = Z T L-2 ~> s / m]
real :: kw_coeff ! A coefficient used to compute the piston velocity [Z T-1 T2 L-2 = Z T L-2 ~> s / m]
real :: Rho0_kg_m3 ! Rho0 in non-scaled units [kg m-3]
real, parameter :: pa_to_atm = 9.8692316931427e-6 ! factor for converting from Pa to atm.
real :: press_to_atm ! converts from model pressure units to atm
integer :: i, j, m, is, ie, js, je

is = G%isc ; ie = G%iec ; js = G%jsc ; je = G%jec
Expand Down Expand Up @@ -493,7 +487,9 @@ subroutine CFC_cap_fluxes(fluxes, sfc_state, G, US, Rho0, Time, id_cfc11_atm, id
! = 6.97e-7 m/s s^2/m^2 [Z T-1 T2 L-2 = Z T L-2 ~> s / m]
kw_coeff = (US%m_to_Z*US%s_to_T*US%L_to_m**2) * 6.97e-7

! set unit conversion factors
Rho0_kg_m3 = Rho0 * US%R_to_kg_m3
press_to_atm = US%R_to_kg_m3*US%L_T_to_m_s**2 * pa_to_atm

do j=js,je ; do i=is,ie
! ta in hectoKelvin
Expand All @@ -506,77 +502,59 @@ subroutine CFC_cap_fluxes(fluxes, sfc_state, G, US, Rho0, Time, id_cfc11_atm, id
! Calculate Schmidt numbers using coefficients given by
! Wanninkhof (2014); doi:10.4319/lom.2014.12.351.
call comp_CFC_schmidt(sfc_state%SST(i,j), sc_11, sc_12)
sc_no_term = sqrt(660.0 / sc_11)

CFC11_alpha(i,j) = alpha_11 * sc_no_term
CFC11_Csurf(i,j) = sfc_state%sfc_CFC11(i,j) * sc_no_term
sc_no_term = sqrt(660.0 / sc_12)
CFC12_alpha(i,j) = alpha_12 * sc_no_term
CFC12_Csurf(i,j) = sfc_state%sfc_CFC12(i,j) * sc_no_term

kw_wo_sc_no_term(i,j) = kw_coeff * ((1.0 - fluxes%ice_fraction(i,j))*fluxes%u10_sqr(i,j))
kw_wo_sc_no_term(i,j) = kw_coeff * ((1.0 - fluxes%ice_fraction(i,j))*fluxes%u10_sqr(i,j))

! air concentrations and cfcs BC's fluxes
! CFC flux units: mol kg-1 s-1 kg m-2
cair(i,j) = US%R_to_kg_m3*US%L_T_to_m_s**2*pa_to_atm * CFC11_alpha(i,j) * cfc11_atm(i,j) * fluxes%p_surf_full(i,j)
fluxes%cfc11_flux(i,j) = kw_wo_sc_no_term(i,j) * (cair(i,j) - CFC11_Csurf(i,j)) * Rho0_kg_m3
cair(i,j) = US%R_to_kg_m3*US%L_T_to_m_s**2*pa_to_atm * CFC12_alpha(i,j) * cfc12_atm(i,j) * fluxes%p_surf_full(i,j)
fluxes%cfc12_flux(i,j) = kw_wo_sc_no_term(i,j) * (cair(i,j) - CFC12_Csurf(i,j)) * Rho0_kg_m3
! CFC flux units: CU Z T-1 kg m-3 = mol kg-1 Z T-1 kg m-3 ~> mol m-2 s-1
kw(i,j) = kw_wo_sc_no_term(i,j) * sqrt(660.0 / sc_11)
cair(i,j) = press_to_atm * alpha_11 * cfc11_atm(i,j) * fluxes%p_surf_full(i,j)
fluxes%cfc11_flux(i,j) = kw(i,j) * (cair(i,j) - sfc_state%sfc_CFC11(i,j)) * Rho0_kg_m3

kw(i,j) = kw_wo_sc_no_term(i,j) * sqrt(660.0 / sc_12)
cair(i,j) = press_to_atm * alpha_12 * cfc12_atm(i,j) * fluxes%p_surf_full(i,j)
fluxes%cfc12_flux(i,j) = kw(i,j) * (cair(i,j) - sfc_state%sfc_CFC12(i,j)) * Rho0_kg_m3
enddo ; enddo

end subroutine CFC_cap_fluxes

!> Calculates the CFC's solubility function following Warner and Weiss (1985) DSR, vol 32.
subroutine get_solubility(alpha_11, alpha_12, ta, sal , mask)
real, intent(inout) :: alpha_11 !< The solubility of CFC 11 [mol kg-1 atm-1]
real, intent(inout) :: alpha_12 !< The solubility of CFC 12 [mol kg-1 atm-1]
real, intent(in ) :: ta !< Absolute sea surface temperature [hectoKelvin]
real, intent(in ) :: sal !< Surface salinity [PSU].
real, intent(in ) :: mask !< ocean mask
real, intent(inout) :: alpha_11 !< The solubility of CFC 11 [mol kg-1 atm-1]
real, intent(inout) :: alpha_12 !< The solubility of CFC 12 [mol kg-1 atm-1]
real, intent(in ) :: ta !< Absolute sea surface temperature [hectoKelvin]
real, intent(in ) :: sal !< Surface salinity [PSU].
real, intent(in ) :: mask !< ocean mask

! Local variables
real :: d11_dflt(4), d12_dflt(4) ! values of the various coefficients
real :: e11_dflt(3), e12_dflt(3) ! in the expressions for the solubility
real :: d1_11, d1_12 ! Coefficients for calculating CFC11 and CFC12 solubilities [nondim]
real :: d2_11, d2_12 ! Coefficients for calculating CFC11 and CFC12 solubilities [hectoKelvin-1]
real :: d3_11, d3_12 ! Coefficients for calculating CFC11 and CFC12 solubilities [log(hectoKelvin)-1]
real :: d4_11, d4_12 ! Coefficients for calculating CFC11 and CFC12 solubilities [hectoKelvin-2]
real :: e1_11, e1_12 ! Coefficients for calculating CFC11 and CFC12 solubilities [PSU-1]
real :: e2_11, e2_12 ! Coefficients for calculating CFC11 and CFC12 solubilities [PSU-1 hectoKelvin-1]
real :: e3_11, e3_12 ! Coefficients for calculating CFC11 and CFC12 solubilities [PSU-2 hectoKelvin-2]
real :: factor ! factor to use in the solubility conversion

!-----------------------------------------------------------------------
! Solubility coefficients for alpha in mol/(kg atm) for CFC11 (_11) and CFC12 (_12)

! Coefficients for calculating CFC11 solubilities
! from Table 5 in Warner and Weiss (1985) DSR, vol 32.

real, parameter :: d1_11 = -232.0411 ! [nondim]
real, parameter :: d2_11 = 322.5546 ! [hectoKelvin-1]
real, parameter :: d3_11 = 120.4956 ! [log(hectoKelvin)-1]
real, parameter :: d4_11 = -1.39165 ! [hectoKelvin-2]

real, parameter :: e1_11 = -0.146531 ! [PSU-1]
real, parameter :: e2_11 = 0.093621 ! [PSU-1 hectoKelvin-1]
real, parameter :: e3_11 = -0.0160693 ! [PSU-2 hectoKelvin-2]

! Coefficients for calculating CFC12 solubilities
! from Table 5 in Warner and Weiss (1985) DSR, vol 32.
!-----------------------------------------------------------------------
d11_dflt(:) = (/ -232.0411, 322.5546, 120.4956, -1.39165 /)
e11_dflt(:) = (/ -0.146531, 0.093621, -0.0160693 /)
d12_dflt(:) = (/ -220.2120, 301.8695, 114.8533, -1.39165 /)
e12_dflt(:) = (/ -0.147718, 0.093175, -0.0157340 /)

d1_11 = d11_dflt(1)
d2_11 = d11_dflt(2)
d3_11 = d11_dflt(3)
d4_11 = d11_dflt(4)

e1_11 = e11_dflt(1)
e2_11 = e11_dflt(2)
e3_11 = e11_dflt(3)

d1_12 = d12_dflt(1)
d2_12 = d12_dflt(2)
d3_12 = d12_dflt(3)
d4_12 = d12_dflt(4)

e1_12 = e12_dflt(1)
e2_12 = e12_dflt(2)
e3_12 = e12_dflt(3)

! Calculate solubilities using Warner and Weiss (1985) DSR, vol 32.
! The following is from Eq. 9 in Warner and Weiss (1985)
! The factor 1.0e+03 is for the conversion from mol/(l * atm) to mol/(m3 * atm)
! The factor 1.e-09 converts from mol/(l * atm) to mol/(m3 * pptv)

real, parameter :: d1_12 = -220.2120 ! [nondim]
real, parameter :: d2_12 = 301.8695 ! [hectoKelvin-1]
real, parameter :: d3_12 = 114.8533 ! [log(hectoKelvin)-1]
real, parameter :: d4_12 = -1.39165 ! [hectoKelvin-2]

real, parameter :: e1_12 = -0.147718 ! [PSU-1]
real, parameter :: e2_12 = 0.093175 ! [PSU-1 hectoKelvin-1]
real, parameter :: e3_12 = -0.0157340 ! [PSU-2 hectoKelvin-2]

real :: factor ! introduce units to result [mol kg-1 atm-1]

! Eq. 9 from Warner and Weiss (1985) DSR, vol 32.
factor = 1.0
alpha_11 = exp(d1_11 + d2_11/ta + d3_11*log(ta) + d4_11*ta**2 +&
sal * ((e3_11 * ta + e2_11) * ta + e1_11)) * &
Expand Down

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