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Update to prevent divide by zero in future version of mstar #994

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Merged
Hallberg-NOAA merged 1 commit into from
Sep 6, 2019
Merged

Update to prevent divide by zero in future version of mstar #994

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32 changes: 18 additions & 14 deletions src/parameterizations/vertical/MOM_energetic_PBL.F90
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Original file line number Diff line number Diff line change
Expand Up @@ -1772,16 +1772,16 @@ subroutine find_mstar(CS, US, Buoyancy_Flux, UStar, UStar_Mean,&

if (CS%answers_2018) then
! The limit for the balance of rotation and stabilizing is f(L_Ekman,L_Obukhov)
MStar_S = CS%MStar_coef*sqrt(max(0.0,Buoyancy_Flux) / Ustar**2 / &
MStar_S = CS%MStar_coef*sqrt(max(0.0,Buoyancy_Flux) / UStar**2 / &
(Abs_Coriolis + 1.e-10*US%T_to_s) )
! The limit for rotation (Ekman length) limited mixing
MStar_N = CS%C_Ek * log( max( 1., Ustar / (Abs_Coriolis + 1.e-10*US%T_to_s) / BLD ) )
MStar_N = CS%C_Ek * log( max( 1., UStar / (Abs_Coriolis + 1.e-10*US%T_to_s) / BLD ) )
else
! The limit for the balance of rotation and stabilizing is f(L_Ekman,L_Obukhov)
mstar_S = CS%MSTAR_COEF*sqrt(max(0.0, Buoyancy_Flux) / (Ustar**2 * max(Abs_Coriolis, 1.e-20*US%T_to_s)))
MStar_S = CS%MSTAR_COEF*sqrt(max(0.0, Buoyancy_Flux) / (UStar**2 * max(Abs_Coriolis, 1.e-20*US%T_to_s)))
! The limit for rotation (Ekman length) limited mixing
mstar_N = 0.0
if (Ustar > Abs_Coriolis * BLD) mstar_N = CS%C_EK * log(Ustar / (Abs_Coriolis * BLD))
MStar_N = 0.0
if (UStar > Abs_Coriolis * BLD) Mstar_N = CS%C_EK * log(UStar / (Abs_Coriolis * BLD))
endif

! Here 1.25 is about .5/von Karman, which gives the Obukhov limit.
Expand All @@ -1792,39 +1792,43 @@ subroutine find_mstar(CS, US, Buoyancy_Flux, UStar, UStar_Mean,&
MStar_N = CS%RH18_MStar_cn1 * ( 1.0 - 1.0 / ( 1. + CS%RH18_MStar_cn2 * &
exp( CS%RH18_mstar_CN3 * BLD * Abs_Coriolis / UStar) ) )
else
MSN_term = CS%RH18_MStar_cn2 * exp( CS%RH18_mstar_CN3 * BLD * Abs_Coriolis / Ustar)
MSN_term = CS%RH18_MStar_cn2 * exp( CS%RH18_mstar_CN3 * BLD * Abs_Coriolis / UStar)
MStar_N = (CS%RH18_MStar_cn1 * MSN_term) / ( 1. + MSN_term)
endif
MStar_S = CS%RH18_MStar_CS1 * ( max(0.0, Buoyancy_Flux)**2 * BLD / &
( Ustar**5 * max(Abs_Coriolis,1.e-20*US%T_to_s) ) )**CS%RH18_mstar_cs2
( UStar**5 * max(Abs_Coriolis,1.e-20*US%T_to_s) ) )**CS%RH18_mstar_cs2
MStar = MStar_N + MStar_S
endif

!/ 2. Adjust mstar to account for convective turbulence
if (CS%answers_2018) then
MStar_Conv_Red = 1. - CS%MStar_Convect_coef * (-min(0.0,Buoyancy_Flux) + 1.e-10*US%T_to_s**3*US%m_to_Z**2) / &
( (-min(0.0,Buoyancy_Flux) + 1.e-10*US%T_to_s**3*US%m_to_Z**2) + &
2.0 *MStar * Ustar**3 / BLD )
2.0 *MStar * UStar**3 / BLD )
else
MSCR_term1 = -BLD * min(0.0, Buoyancy_Flux)
MSCR_term2 = 2.0*MStar * Ustar**3
MStar_Conv_Red = ((1.-CS%mstar_convect_coef) * MSCR_term1 + MSCR_term2) / (MSCR_term1 + MSCR_term2)
MSCR_term2 = 2.0*MStar * UStar**3
if ( abs(MSCR_term2) > 0.0) then
MStar_Conv_Red = ((1.-CS%mstar_convect_coef) * MSCR_term1 + MSCR_term2) / (MSCR_term1 + MSCR_term2)
else
MStar_Conv_Red = 1.-CS%mstar_convect_coef
endif
endif

!/3. Combine various mstar terms to get final value
MStar = MStar * MStar_Conv_Red

if (present(Langmuir_Number)) then
!### In this call, ustar was previously ustar_mean. Is this change deliberate?
call mstar_Langmuir(CS, US, abs_Coriolis, buoyancy_flux, ustar, BLD, Langmuir_number, mstar, &
mstar_LT, Convect_Langmuir_Number)
call mstar_Langmuir(CS, US, Abs_Coriolis, Buoyancy_Flux, UStar, BLD, Langmuir_Number, MStar, &
MStar_LT, Convect_Langmuir_Number)
endif

end subroutine Find_Mstar

!> This subroutine modifies the Mstar value if the Langmuir number is present
subroutine Mstar_Langmuir(CS, US, abs_Coriolis, buoyancy_flux, ustar, BLD, Langmuir_Number, &
mstar, mstar_LT, Convect_Langmuir_Number)
subroutine Mstar_Langmuir(CS, US, Abs_Coriolis, Buoyancy_Flux, UStar, BLD, Langmuir_Number, &
Mstar, MStar_LT, Convect_Langmuir_Number)
type(energetic_PBL_CS), pointer :: CS !< Energetic_PBL control structure.
type(unit_scale_type), intent(in) :: US !< A dimensional unit scaling type
real, intent(in) :: Abs_Coriolis !< Absolute value of the Coriolis parameter [T-1 ~> s-1]
Expand Down