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Fix backscatter divide by zero #62

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Merged
marshallward merged 3 commits into from
Jan 25, 2022
Merged

Fix backscatter divide by zero #62

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f7fd4e4
Avoid divide by zero in horizontal_viscosity() with better_bound_kh
adcroft Jan 21, 2022
fc3e3ac
Fix soft-conventional index capitalization in horizontal_viscosity()
adcroft Jan 21, 2022
d3e8970
Merge branch 'dev/gfdl' into fix-backscatter-divide-by-zero
marshallward Jan 24, 2022
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65 changes: 33 additions & 32 deletions src/parameterizations/lateral/MOM_hor_visc.F90
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Original file line number Diff line number Diff line change
Expand Up @@ -1003,6 +1003,7 @@ subroutine horizontal_viscosity(u, v, h, diffu, diffv, MEKE, VarMix, G, GV, US,
visc_bound_rem(i,j) = 0.0
Kh(i,j) = hrat_min(i,j) * CS%Kh_Max_xx(i,j)
else
! ### NOTE: The denominator could be zero here - AJA ###
visc_bound_rem(i,j) = 1.0 - Kh(i,j) / (hrat_min(i,j) * CS%Kh_Max_xx(i,j))
endif
enddo ; enddo
Expand Down Expand Up @@ -1194,7 +1195,7 @@ subroutine horizontal_viscosity(u, v, h, diffu, diffv, MEKE, VarMix, G, GV, US,
if (CS%better_bound_Ah .or. CS%better_bound_Kh) then
do J=js-1,Jeq ; do I=is-1,Ieq
h_min = min(h_u(I,j), h_u(I,j+1), h_v(i,J), h_v(i+1,J))
hrat_min(i,j) = min(1.0, h_min / (hq(I,J) + h_neglect))
hrat_min(I,J) = min(1.0, h_min / (hq(I,J) + h_neglect))
enddo ; enddo

if (CS%better_bound_Kh) then
Expand All @@ -1217,11 +1218,11 @@ subroutine horizontal_viscosity(u, v, h, diffu, diffv, MEKE, VarMix, G, GV, US,
(G%mask2dCv(i,J) + G%mask2dCv(i+1,J)) == 0.0) then
! Only one of hu and hv is nonzero, so just add them.
hq(I,J) = hu + hv
hrat_min(i,j) = 1.0
hrat_min(I,J) = 1.0
else
! Both hu and hv are nonzero, so take the harmonic mean.
hq(I,J) = 2.0 * (hu * hv) / ((hu + hv) + h_neglect)
hrat_min(i,j) = min(1.0, min(hu, hv) / (hq(I,J) + h_neglect) )
hrat_min(I,J) = min(1.0, min(hu, hv) / (hq(I,J) + h_neglect) )
endif
endif
endif
Expand All @@ -1234,11 +1235,11 @@ subroutine horizontal_viscosity(u, v, h, diffu, diffv, MEKE, VarMix, G, GV, US,
do J=js-1,Jeq ; do I=is-1,Ieq
grad_vort = grad_vort_mag_q(I,J) + grad_div_mag_q(I,J)
grad_vort_qg = 3. * grad_vort_mag_q_2d(I,J)
vert_vort_mag(i,j) = min(grad_vort, grad_vort_qg)
vert_vort_mag(I,J) = min(grad_vort, grad_vort_qg)
enddo ; enddo
else
do J=js-1,Jeq ; do I=is-1,Ieq
vert_vort_mag(i,j) = grad_vort_mag_q(I,J) + grad_div_mag_q(I,J)
vert_vort_mag(I,J) = grad_vort_mag_q(I,J) + grad_div_mag_q(I,J)
enddo ; enddo
endif
endif
Expand All @@ -1254,23 +1255,23 @@ subroutine horizontal_viscosity(u, v, h, diffu, diffv, MEKE, VarMix, G, GV, US,
if (CS%Smagorinsky_Kh) then
if (CS%add_LES_viscosity) then
do J=js-1,Jeq ; do I=is-1,Ieq
Kh(i,j) = Kh(i,j) + CS%Laplac2_const_xx(i,j) * Shear_mag(i,j)
Kh(I,J) = Kh(I,J) + CS%Laplac2_const_xx(i,j) * Shear_mag(i,j)
enddo ; enddo
else
do J=js-1,Jeq ; do I=is-1,Ieq
Kh(i,j) = max(Kh(i,j), CS%Laplac2_const_xy(I,J) * Shear_mag(i,j) )
Kh(I,J) = max(Kh(I,J), CS%Laplac2_const_xy(I,J) * Shear_mag(i,j) )
enddo ; enddo
endif
endif

if (CS%Leith_Kh) then
if (CS%add_LES_viscosity) then
do J=js-1,Jeq ; do I=is-1,Ieq
Kh(i,j) = Kh(i,j) + CS%Laplac3_const_xx(i,j) * vert_vort_mag(i,j) * inv_PI3
Kh(I,J) = Kh(I,J) + CS%Laplac3_const_xx(i,j) * vert_vort_mag(I,J) * inv_PI3 ! Is this right? -AJA
enddo ; enddo
else
do J=js-1,Jeq ; do I=is-1,Ieq
Kh(i,j) = max(Kh(i,j), CS%Laplac3_const_xy(I,J) * vert_vort_mag(i,j) * inv_PI3)
Kh(I,J) = max(Kh(I,J), CS%Laplac3_const_xy(I,J) * vert_vort_mag(I,J) * inv_PI3)
enddo ; enddo
endif
endif
Expand All @@ -1281,40 +1282,40 @@ subroutine horizontal_viscosity(u, v, h, diffu, diffv, MEKE, VarMix, G, GV, US,
! stack size has been reduced.
do J=js-1,Jeq ; do I=is-1,Ieq
if (rescale_Kh) &
Kh(i,j) = VarMix%Res_fn_q(i,j) * Kh(i,j)
Kh(I,J) = VarMix%Res_fn_q(I,J) * Kh(I,J)

if (CS%res_scale_MEKE) &
meke_res_fn = VarMix%Res_fn_q(i,j)
meke_res_fn = VarMix%Res_fn_q(I,J)

! Older method of bounding for stability
if (legacy_bound) &
Kh(i,j) = min(Kh(i,j), CS%Kh_Max_xy(i,j))
Kh(I,J) = min(Kh(I,J), CS%Kh_Max_xy(I,J))

Kh(i,j) = max(Kh(i,j), CS%Kh_bg_min) ! Place a floor on the viscosity, if desired.
Kh(I,J) = max(Kh(I,J), CS%Kh_bg_min) ! Place a floor on the viscosity, if desired.

if (use_MEKE_Ku) then
! *Add* the MEKE contribution (might be negative)
Kh(i,j) = Kh(i,j) + 0.25*( (MEKE%Ku(i,j) + MEKE%Ku(i+1,j+1)) + &
Kh(I,J) = Kh(I,J) + 0.25*( (MEKE%Ku(i,j) + MEKE%Ku(i+1,j+1)) + &
(MEKE%Ku(i+1,j) + MEKE%Ku(i,j+1)) ) * meke_res_fn
endif

! Older method of bounding for stability
if (CS%anisotropic) &
! *Add* the shear component of anisotropic viscosity
Kh(i,j) = Kh(i,j) + CS%Kh_aniso * CS%n1n2_q(I,J)**2
Kh(I,J) = Kh(I,J) + CS%Kh_aniso * CS%n1n2_q(I,J)**2

! Newer method of bounding for stability
if (CS%better_bound_Kh) then
if (Kh(i,j) >= hrat_min(i,j) * CS%Kh_Max_xy(I,J)) then
if (Kh(i,j) >= hrat_min(I,J) * CS%Kh_Max_xy(I,J)) then
visc_bound_rem(i,j) = 0.0
Kh(i,j) = hrat_min(i,j) * CS%Kh_Max_xy(I,J)
elseif (CS%Kh_Max_xy(I,J)>0.) then
visc_bound_rem(i,j) = 1.0 - Kh(i,j) / (hrat_min(i,j) * CS%Kh_Max_xy(I,J))
Kh(i,j) = hrat_min(I,J) * CS%Kh_Max_xy(I,J)
elseif (hrat_min(I,J)*CS%Kh_Max_xy(I,J)>0.) then
visc_bound_rem(I,J) = 1.0 - Kh(I,J) / (hrat_min(I,J) * CS%Kh_Max_xy(I,J))
endif
endif

if (CS%id_Kh_q>0 .or. CS%debug) &
Kh_q(I,J,k) = Kh(i,j)
Kh_q(I,J,k) = Kh(I,J)

if (CS%id_vort_xy_q>0) &
vort_xy_q(I,J,k) = vort_xy(I,J)
Expand Down Expand Up @@ -1352,37 +1353,37 @@ subroutine horizontal_viscosity(u, v, h, diffu, diffv, MEKE, VarMix, G, GV, US,
if (CS%Smagorinsky_Ah) then
if (CS%bound_Coriolis) then
do J=js-1,Jeq ; do I=is-1,Ieq
AhSm = Shear_mag(i,j) * (CS%Biharm_const_xy(I,J) &
+ CS%Biharm_const2_xy(I,J) * Shear_mag(i,j) &
AhSm = Shear_mag(I,J) * (CS%Biharm_const_xy(I,J) &
+ CS%Biharm_const2_xy(I,J) * Shear_mag(I,J) &
)
Ah(i,j) = max(Ah(I,J), AhSm)
enddo ; enddo
else
do J=js-1,Jeq ; do I=is-1,Ieq
AhSm = CS%Biharm_const_xy(I,J) * Shear_mag(i,j)
Ah(i,j) = max(Ah(I,J), AhSm)
AhSm = CS%Biharm_const_xy(I,J) * Shear_mag(I,J)
Ah(I,J) = max(Ah(I,J), AhSm)
enddo ; enddo
endif
endif

if (CS%Leith_Ah) then
do J=js-1,Jeq ; do I=is-1,Ieq
AhLth = CS%Biharm6_const_xy(I,J) * abs(Del2vort_q(I,J)) * inv_PI6
Ah(i,j) = max(Ah(I,J), AhLth)
Ah(I,J) = max(Ah(I,J), AhLth)
enddo ; enddo
endif

if (CS%bound_Ah .and. .not.CS%better_bound_Ah) then
do J=js-1,Jeq ; do I=is-1,Ieq
Ah(i,j) = min(Ah(i,j), CS%Ah_Max_xy(I,J))
Ah(I,J) = min(Ah(I,J), CS%Ah_Max_xy(I,J))
enddo ; enddo
endif
endif ! Smagorinsky_Ah or Leith_Ah

if (use_MEKE_Au) then
! *Add* the MEKE contribution
do J=js-1,Jeq ; do I=is-1,Ieq
Ah(i,j) = Ah(i,j) + 0.25 * ( &
Ah(I,J) = Ah(I,J) + 0.25 * ( &
(MEKE%Au(i,j) + MEKE%Au(i+1,j+1)) + (MEKE%Au(i+1,j) + MEKE%Au(i,j+1)) &
)
enddo ; enddo
Expand All @@ -1391,31 +1392,31 @@ subroutine horizontal_viscosity(u, v, h, diffu, diffv, MEKE, VarMix, G, GV, US,
if (CS%Re_Ah > 0.0) then
do J=js-1,Jeq ; do I=is-1,Ieq
KE = 0.125 * ((u(I,j,k) + u(I,j+1,k))**2 + (v(i,J,k) + v(i+1,J,k))**2)
Ah(i,j) = sqrt(KE) * CS%Re_Ah_const_xy(i,j)
Ah(I,J) = sqrt(KE) * CS%Re_Ah_const_xy(i,j)
enddo ; enddo
endif

if (CS%better_bound_Ah) then
if (CS%better_bound_Kh) then
do J=js-1,Jeq ; do I=is-1,Ieq
Ah(i,j) = min(Ah(i,j), visc_bound_rem(i,j) * hrat_min(i,j) * CS%Ah_Max_xy(I,J))
Ah(I,J) = min(Ah(i,j), visc_bound_rem(i,j) * hrat_min(I,J) * CS%Ah_Max_xy(I,J))
enddo ; enddo
else
do J=js-1,Jeq ; do I=is-1,Ieq
Ah(i,j) = min(Ah(i,j), hrat_min(i,j) * CS%Ah_Max_xy(I,J))
Ah(I,J) = min(Ah(i,j), hrat_min(I,J) * CS%Ah_Max_xy(I,J))
enddo ; enddo
endif
endif

if (CS%id_Ah_q>0 .or. CS%debug) then
do J=js-1,Jeq ; do I=is-1,Ieq
Ah_q(I,J,k) = Ah(i,j)
Ah_q(I,J,k) = Ah(I,J)
enddo ; enddo
endif

! Again, need to initialize str_xy as if its biharmonic
do J=js-1,Jeq ; do I=is-1,Ieq
d_str = Ah(i,j) * (dDel2vdx(I,J) + dDel2udy(I,J))
d_str = Ah(I,J) * (dDel2vdx(I,J) + dDel2udy(I,J))

str_xy(I,J) = str_xy(I,J) + d_str

Expand Down