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*Refactor CORRECTION_INTX_PA
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  Refactored the CORRECTION_INTX_PA calculations to avoid multiple intermediate
steps, while also adding comments documenting the derivation of the final
expression.  Also calculate the pressures used in the equation of state calls
with the Boussinesq CORRECTION_INTX_PA and RESET_INTXPA_INTEGRAL options
consistently with the other terms.  These changes will change the answers when
either of those options are in use, but are bitwise identical when they are not.
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@Hallberg-NOAA @marshallward
Hallberg-NOAA authored and marshallward committed Sep 17, 2024
1 parent 7a9545a commit 4cf1590
Showing 1 changed file with 76 additions and 34 deletions.
110 changes: 76 additions & 34 deletions src/core/MOM_PressureForce_FV.F90
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Original file line number Diff line number Diff line change
Expand Up @@ -963,15 +963,15 @@ subroutine PressureForce_FV_Bouss(h, tv, PFu, PFv, G, GV, US, CS, ALE_CSp, p_atm
!$OMP parallel do default(shared) private(p_surf_EOS)
do j=Jsq,Jeq+1
! P_surf_EOS here is consistent with the pressure that is used in the int_density_dz routines.
do i=Isq,Ieq+1 ; p_surf_EOS(i) = -GxRho*(e(i,j,1) - G%Z_ref) ; enddo
do i=Isq,Ieq+1 ; p_surf_EOS(i) = -GxRho*(e(i,j,1) - Z_0p(i,j)) ; enddo
call calculate_density(T_t(:,j,1), S_t(:,j,1), p_surf_EOS, rho_top(:,j), &
tv%eqn_of_state, EOSdom, rho_ref=rho_ref)
enddo
elseif (use_EOS) then
!$OMP parallel do default(shared) private(p_surf_EOS)
do j=Jsq,Jeq+1
! P_surf_EOS here is consistent with the pressure that is used in the int_density_dz routines.
do i=Isq,Ieq+1 ; p_surf_EOS(i) = -GxRho*(e(i,j,1) - G%Z_ref) ; enddo
do i=Isq,Ieq+1 ; p_surf_EOS(i) = -GxRho*(e(i,j,1) - Z_0p(i,j)) ; enddo
call calculate_density(tv%T(:,j,1), tv%S(:,j,1), p_surf_EOS, rho_top(:,j), &
tv%eqn_of_state, EOSdom, rho_ref=rho_ref)
enddo
Expand Down Expand Up @@ -999,25 +999,23 @@ subroutine PressureForce_FV_Bouss(h, tv, PFu, PFv, G, GV, US, CS, ALE_CSp, p_atm
T5(1) = T_t(i,j,1) ; T5(5) = T_t(i+1,j,1)
S5(1) = S_t(i,j,1) ; S5(5) = S_t(i+1,j,1)
pa5(1) = pa(i,j,1) ; pa5(5) = pa(i+1,j,1)
! Pressure input to density EOS is the actual pressure not adjusted for rho_ref.
p5(1) = pa(i,j,1) - GxRho*(e(i,j,1) - G%Z_ref)
p5(5) = pa(i+1,j,1) - GxRho*(e(i+1,j,1) - G%Z_ref)
! Pressure input to density EOS is consistent with the pressure used in the int_density_dz routines.
p5(1) = -GxRho*(e(i,j,1) - Z_0p(i,j))
p5(5) = -GxRho*(e(i+1,j,1) - Z_0p(i,j))
do m=2,4
wt_R = 0.25*real(m-1)
T5(m) = T5(1) + (T5(5)-T5(1))*wt_R !Quadratic: + (T5(5)-T5(1))*B*wt_R*(wt_R-1);
S5(m) = S5(1) + (S5(5)-S5(1))*wt_R !+ (S5(5)-S5(1))*B*wt_R*(wt_R-1);
T5(m) = T5(1) + (T5(5)-T5(1))*wt_R
S5(m) = S5(1) + (S5(5)-S5(1))*wt_R
p5(m) = p5(1) + (p5(5)-p5(1))*wt_R
enddo !m
call calculate_density(T5, S5, p5, r5, tv%eqn_of_state, rho_ref=rho_ref)
do m=2,4
! Make pressure curvature a difference from the linear fit of pressure between the two points
! Do this by integrating pressure between each of the 5 points and adding up
! This way integration direction doesn't matter when adding up pressure from previous point
pa5(m) = pa5(m-1) + ((0.25*(pa5(5)-pa5(1)) + 0.125*(r5(5)+r5(1))*dz_geo_sfc) - &
0.125*(r5(m)+r5(m-1))*dz_geo_sfc)
enddo
! Get a correction from difference between this and linear average.
intx_pa_cor(I,j) = C1_90*((32.0*(pa5(2)+pa5(4)) + 12.0*pa5(3)) - 38.0*(pa5(1) + pa5(5)))

! Use a trapezoidal rule integral of the hydrostatic equation to determine the pressure
! anomalies at 5 equally spaced points along the interface, and then use Boole's rule
! quadrature to find the integrated correction to the integral of pressure along the interface.
! The derivation for this expression is shown below in the y-direction version.
intx_pa_cor(I,j) = C1_90 * (4.75*(r5(5)-r5(1)) + 5.5*(r5(4)-r5(2))) * dz_geo_sfc
! Note that (4.75 + 5.5/2) / 90 = 1/12, so this is consistent with the linear result below.
else ! Do not use 5-point quadrature.
intx_pa_cor(I,j) = C1_12 * (rho_top(i+1,j)-rho_top(i,j)) * dz_geo_sfc
endif
Expand All @@ -1040,25 +1038,64 @@ subroutine PressureForce_FV_Bouss(h, tv, PFu, PFv, G, GV, US, CS, ALE_CSp, p_atm
T5(1) = T_t(i,j,1) ; T5(5) = T_t(i,j+1,1)
S5(1) = S_t(i,j,1) ; S5(5) = S_t(i,j+1,1)
pa5(1) = pa(i,j,1) ; pa5(5) = pa(i,j+1,1)
! Pressure input to density EOS is the actual pressure not adjusted for rho_ref.
p5(1) = pa(i,j,1) - GxRho*(e(i,j,1) - G%Z_ref)
p5(5) = pa(i,j+1,1) - GxRho*(e(i,j+1,1) - G%Z_ref)
! Pressure input to density EOS is consistent with the pressure used in the int_density_dz routines.
p5(1) = -GxRho*(e(i,j,1) - Z_0p(i,j))
p5(5) = -GxRho*(e(i,j+1,1) - Z_0p(i,j))

do m=2,4
wt_R = 0.25*real(m-1)
T5(m) = T5(1) + (T5(5)-T5(1))*wt_R !Quadratic: + (T5(5)-T5(1))*B*wt_R*(wt_R-1);
S5(m) = S5(1) + (S5(5)-S5(1))*wt_R !+ (S5(5)-S5(1))*B*wt_R*(wt_R-1);
T5(m) = T5(1) + (T5(5)-T5(1))*wt_R
S5(m) = S5(1) + (S5(5)-S5(1))*wt_R
p5(m) = p5(1) + (p5(5)-p5(1))*wt_R
enddo !m
call calculate_density(T5, S5, p5, r5, tv%eqn_of_state, rho_ref=rho_ref)
do m=2,4
! Make pressure curvature a difference from the linear fit of pressure between the two points
! Do this by integrating pressure between each of the 5 points and adding up
! This way integration direction doesn't matter when adding up pressure from previous point
pa5(m) = pa5(m-1) + ((0.25*(pa5(5)-pa5(1)) + 0.125*(r5(5)+r5(1))*dz_geo_sfc) - &
0.125*(r5(m)+r5(m-1))*dz_geo_sfc)
enddo
! Get a correction from difference between this and linear average.
inty_pa_cor(i,J) = C1_90*((32.0*(pa5(2)+pa5(4)) + 12.0*pa5(3)) - 38.0*(pa5(1) + pa5(5)))

! Use a trapezoidal rule integral of the hydrostatic equation to determine the pressure
! anomalies at 5 equally spaced points along the interface, and then use Boole's rule
! quadrature to find the integrated correction to the integral of pressure along the interface.
inty_pa_cor(i,J) = C1_90 * (4.75*(r5(5)-r5(1)) + 5.5*(r5(4)-r5(2))) * dz_geo_sfc

! The derivation of this correction follows:

! Make pressure curvature a difference from the linear fit of pressure between the two points
! (which is equivalent to taking 4 trapezoidal rule integrals of the hydrostatic equation on
! sub-segments), with a constant slope that is chosen so that the pressure anomalies at the
! two ends of the segment agree with their known values.
! d_geo_8 = 0.125*dz_geo_sfc
! dpa_subseg = 0.25*(pa5(5)-pa5(1)) + &
! 0.25*d_geo_8 * ((r5(5)+r5(1)) + 2.0*((r5(4)+r5(2)) + r5(3)))
! do m=2,4
! pa5(m) = pa5(m-1) + dpa_subseg - d_geo_8*(r5(m)+r5(m-1)))
! enddo

! Explicitly finding expressions for the incremental pressures from the recursion relation above:
! pa5(2) = 0.25*(3.*pa5(1) + pa5(5)) + 0.25*d_geo_8 * ( (r5(5)-3.*r5(1)) + 2.0*((r5(4)-r5(2)) + r5(3)) )
! ! pa5(3) = 0.5*(pa5(1) + pa5(5)) + 0.25*d_geo_8 * &
! ! ( (r5(5)+r5(1)) + 2.0*((r5(4)+r5(2)) + r5(3)) + &
! ! (r5(5)-3.*r5(1)) + 2.0*((r5(4)-r5(2)) + r5(3)) - 4.*(r5(3)+r5(2)) )
! pa5(3) = 0.5*(pa5(1) + pa5(5)) + d_geo_8 * (0.5*(r5(5)-r5(1)) + (r5(4)-r5(2)) )
! ! pa5(4) = 0.25*(pa5(1) + 3.0*pa5(5)) + 0.25*d_geo_8 * &
! ! (2.0*(r5(5)-r5(1)) + 4.0*(r5(4)-r5(2)) + (r5(5)+r5(1)) + &
! ! 2.0*(r5(4)+r5(2)) + 2.0*r5(3) - 4.*(r5(4)+r5(3)))
! pa5(4) = 0.25*(pa5(1) + 3.0*pa5(5)) + 0.25*d_geo_8 * ( (3.*r5(5)-r5(1)) + 2.0*((r5(4)-r5(2)) - r5(3)) )
! ! pa5(5) = pa5(5) + 0.25*d_geo_8 * &
! ! ( (3.*r5(5)-r5(1)) + 2.0*((r5(4)-r5(2)) - r5(3)) + &
! ! ((r5(5)+r5(1)) + 2.0*((r5(4)+r5(2)) + r5(3))) - 4.*(r5(5)+r5(4)) )
! pa5(5) = pa5(5) ! As it should.

! From these:
! pa5(2) + pa5(4) = (pa5(1) + pa5(5)) + 0.25*d_geo_8 * &
! ( (r5(5)-3.*r5(1)) + 2.0*((r5(4)-r5(2)) + r5(3)) + (3.*r5(5)-r5(1)) + 2.0*((r5(4)-r5(2)) - r5(3))
! pa5(2) + pa5(4) = (pa5(1) + pa5(5)) + d_geo_8 * ( (r5(5)-r5(1)) + (r5(4)-r5(2)) )

! Get the correction from the difference between the 5-point quadrature integral of pa5 and
! its trapezoidal rule integral as:
! inty_pa_cor(i,J) = C1_90*(7.0*(pa5(1)+pa5(5)) + 32.0*(pa5(2)+pa5(4)) + 12.0*pa5(3)) - 0.5*(pa5(1)+pa5(5)))
! inty_pa_cor(i,J) = C1_90*((32.0*(pa5(2)+pa5(4)) + 12.0*pa5(3)) - 38.0*(pa5(1)+pa5(5)))
! inty_pa_cor(i,J) = C1_90*d_geo_8 * ((32.0*( (r5(5)-r5(1)) + (r5(4)-r5(2)) ) + &
! (6.*(r5(5)-r5(1)) + 12.0*(r5(4)-r5(2)) ))
! inty_pa_cor(i,J) = C1_90*d_geo_8 * ( 38.0*(r5(5)-r5(1)) + 44.0*(r5(4)-r5(2)) )

else ! Do not use 5-point quadrature.
inty_pa_cor(i,J) = C1_12 * (rho_top(i,j+1)-rho_top(i,j)) * dz_geo_sfc
endif
Expand Down Expand Up @@ -1118,8 +1155,11 @@ subroutine PressureForce_FV_Bouss(h, tv, PFu, PFv, G, GV, US, CS, ALE_CSp, p_atm
! the interface below this cell (it might have quadratic pressure dependence if sloped)
T_int_W(I,j) = T_b(i,j,k) ; T_int_E(I,j) = T_b(i+1,j,k)
S_int_W(I,j) = S_b(i,j,k) ; S_int_E(I,j) = S_b(i+1,j,k)
p_int_W(I,j) = pa(i,j,K+1) - GxRho*(e(i,j,K+1) - G%Z_ref)
p_int_E(I,j) = pa(i+1,j,K+1) - GxRho*(e(i+1,j,K+1) - G%Z_ref)
! These pressures are only used for the equation of state, and are only a function of
! height, consistent with the expressions in the int_density_dz routines.
p_int_W(I,j) = -GxRho*(e(i,j,K+1) - Z_0p(i,j))
p_int_E(I,j) = -GxRho*(e(i+1,j,K+1) - Z_0p(i,j))

intx_pa_nonlin(I,j) = intx_pa(I,j,K+1) - 0.5*(pa(i,j,K+1) + pa(i+1,j,K+1))
dgeo_x(I,j) = GV%g_Earth * (e(i+1,j,K+1)-e(i,j,K+1))
seek_x_cor(I,j) = .false.
Expand Down Expand Up @@ -1161,8 +1201,10 @@ subroutine PressureForce_FV_Bouss(h, tv, PFu, PFv, G, GV, US, CS, ALE_CSp, p_atm
! the interface below this cell (it might have quadratic pressure dependence if sloped)
T_int_S(i,J) = T_b(i,j,k) ; T_int_N(i,J) = T_b(i,j+1,k)
S_int_S(i,J) = S_b(i,j,k) ; S_int_N(i,J) = S_b(i,j+1,k)
p_int_S(i,J) = pa(i,j,K+1) - GxRho*(e(i,j,K+1) - G%Z_ref)
p_int_N(i,J) = pa(i,j+1,K+1) - GxRho*(e(i,j+1,K+1) - G%Z_ref)
! These pressures are only used for the equation of state, and are only a function of
! height, consistent with the expressions in the int_density_dz routines.
p_int_S(i,J) = -GxRho*(e(i,j,K+1) - Z_0p(i,j))
p_int_N(i,J) = -GxRho*(e(i,j+1,K+1) - Z_0p(i,j))
inty_pa_nonlin(i,J) = inty_pa(i,J,K+1) - 0.5*(pa(i,j,K+1) + pa(i,j+1,K+1))
dgeo_y(i,J) = GV%g_Earth * (e(i,j+1,K+1)-e(i,j,K+1))
seek_y_cor(i,J) = .false.
Expand Down

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