Correct multi-PE velocity truncation counts (mom-ocean#955)

Modified the conditions that determine when to increment the count of velocity
truncations to use the thickness as interpolated to velocity points to determine
whether layers are thick enough to be counted, rather than the arithmetic mean
thickness, and only count truncations that occur in the non-symmetric
computational domain to avoid double counting.  The filtering thicknesses
should be very similar in the ocean interior, but they will differ at open
boundary condition points.  The corrected counting was verified by running the
sloshing/layer test case with a maximum CFL set to 0.01 to create lots of
truncations, and then verifying that the truncation count is now the same on 1
and 10 PEs, whereas before it was not.  All solutions are bitwise identical, but
the reported truncation counts in the ocean.stats files can change in
multiple-PE cases with velocity truncations.

Author: Hallberg-NOAA

src/parameterizations/vertical/MOM_vert_friction.F90

@@ -2922,8 +2922,9 @@ subroutine find_coupling_coef(a_cpl, hvel, do_i, h_harm, bbl_thick, kv_bbl, z_i,
   endif
 end subroutine find_coupling_coef
 
-!> Velocity components which exceed a threshold for physically reasonable values
-!! are truncated. Optionally, any column with excessive velocities may be sent
+!> Velocity components which exceed a threshold for physically reasonable values are truncated,
+!! and the running sum of the number of trunctionas within the non-symmetric memory computational
+!! domain is incremmented.  Optionally, any column with excessive velocities may be sent
 !! to a diagnostic reporting subroutine.
 subroutine vertvisc_limit_vel(u, v, h, ADp, CDp, forces, visc, dt, G, GV, US, CS)
   type(ocean_grid_type),   intent(in)    :: G      !< Ocean grid structure
@@ -2953,7 +2954,7 @@ subroutine vertvisc_limit_vel(u, v, h, ADp, CDp, forces, visc, dt, G, GV, US, CS
   is = G%isc ; ie = G%iec ; js = G%jsc ; je = G%jec ; nz = GV%ke
   Isq = G%IscB ; Ieq = G%IecB ; Jsq = G%JscB ; Jeq = G%JecB
 
-  H_report = 6.0 * GV%Angstrom_H
+  H_report = 3.0 * GV%Angstrom_H
 
   if (len_trim(CS%u_trunc_file) > 0) then
     !$OMP parallel do default(shared) private(trunc_any,CFL)
@@ -2983,10 +2984,12 @@ subroutine vertvisc_limit_vel(u, v, h, ADp, CDp, forces, visc, dt, G, GV, US, CS
         do k=1,nz ; do I=Isq,Ieq
           if ((u(I,j,k) * (dt * G%dy_Cu(I,j))) * G%IareaT(i+1,j) < -CS%CFL_trunc) then
             u(I,j,k) = (-0.9*CS%CFL_trunc) * (G%areaT(i+1,j) / (dt * G%dy_Cu(I,j)))
-            if (h(i,j,k) + h(i+1,j,k) > H_report) CS%ntrunc = CS%ntrunc + 1
+            if (((I >= G%isc) .and. (I <= G%iec) .and. (j >= G%jsc) .and. (j <= G%jec)) .and. &
+                (CS%h_u(I,j,k) > H_report)) CS%ntrunc = CS%ntrunc + 1
           elseif ((u(I,j,k) * (dt * G%dy_Cu(I,j))) * G%IareaT(i,j) > CS%CFL_trunc) then
             u(I,j,k) = (0.9*CS%CFL_trunc) * (G%areaT(i,j) / (dt * G%dy_Cu(I,j)))
-            if (h(i,j,k) + h(i+1,j,k) > H_report) CS%ntrunc = CS%ntrunc + 1
+            if (((I >= G%isc) .and. (I <= G%iec) .and. (j >= G%jsc) .and. (j <= G%jec)) .and. &
+                (CS%h_u(I,j,k) > H_report)) CS%ntrunc = CS%ntrunc + 1
           endif
         enddo ; enddo
       endif
@@ -2997,10 +3000,12 @@ subroutine vertvisc_limit_vel(u, v, h, ADp, CDp, forces, visc, dt, G, GV, US, CS
       if (abs(u(I,j,k)) < CS%vel_underflow) then ; u(I,j,k) = 0.0
       elseif ((u(I,j,k) * (dt * G%dy_Cu(I,j))) * G%IareaT(i+1,j) < -CS%CFL_trunc) then
         u(I,j,k) = (-0.9*CS%CFL_trunc) * (G%areaT(i+1,j) / (dt * G%dy_Cu(I,j)))
-        if (h(i,j,k) + h(i+1,j,k) > H_report) CS%ntrunc = CS%ntrunc + 1
+        if (((I >= G%isc) .and. (I <= G%iec) .and. (j >= G%jsc) .and. (j <= G%jec)) .and. &
+            (CS%h_u(I,j,k) > H_report)) CS%ntrunc = CS%ntrunc + 1
       elseif ((u(I,j,k) * (dt * G%dy_Cu(I,j))) * G%IareaT(i,j) > CS%CFL_trunc) then
         u(I,j,k) = (0.9*CS%CFL_trunc) * (G%areaT(i,j) / (dt * G%dy_Cu(I,j)))
-        if (h(i,j,k) + h(i+1,j,k) > H_report) CS%ntrunc = CS%ntrunc + 1
+        if (((I >= G%isc) .and. (I <= G%iec) .and. (j >= G%jsc) .and. (j <= G%jec)) .and. &
+            (CS%h_u(I,j,k) > H_report)) CS%ntrunc = CS%ntrunc + 1
       endif
     enddo ; enddo ; enddo
   endif
@@ -3041,10 +3046,12 @@ subroutine vertvisc_limit_vel(u, v, h, ADp, CDp, forces, visc, dt, G, GV, US, CS
         do k=1,nz ; do i=is,ie
           if ((v(i,J,k) * (dt * G%dx_Cv(i,J))) * G%IareaT(i,j+1) < -CS%CFL_trunc) then
             v(i,J,k) = (-0.9*CS%CFL_trunc) * (G%areaT(i,j+1) / (dt * G%dx_Cv(i,J)))
-            if (h(i,j,k) + h(i,j+1,k) > H_report) CS%ntrunc = CS%ntrunc + 1
+            if (((i >= G%isc) .and. (i <= G%iec) .and. (J >= G%jsc) .and. (J <= G%jec)) .and. &
+                (CS%h_v(i,J,k) > H_report)) CS%ntrunc = CS%ntrunc + 1
           elseif ((v(i,J,k) * (dt * G%dx_Cv(i,J))) * G%IareaT(i,j) > CS%CFL_trunc) then
             v(i,J,k) = (0.9*CS%CFL_trunc) * (G%areaT(i,j) / (dt * G%dx_Cv(i,J)))
-            if (h(i,j,k) + h(i,j+1,k) > H_report) CS%ntrunc = CS%ntrunc + 1
+            if (((i >= G%isc) .and. (i <= G%iec) .and. (J >= G%jsc) .and. (J <= G%jec)) .and. &
+                (CS%h_v(i,J,k) > H_report)) CS%ntrunc = CS%ntrunc + 1
           endif
         enddo ; enddo
       endif
@@ -3055,10 +3062,12 @@ subroutine vertvisc_limit_vel(u, v, h, ADp, CDp, forces, visc, dt, G, GV, US, CS
       if (abs(v(i,J,k)) < CS%vel_underflow) then ; v(i,J,k) = 0.0
       elseif ((v(i,J,k) * (dt * G%dx_Cv(i,J))) * G%IareaT(i,j+1) < -CS%CFL_trunc) then
         v(i,J,k) = (-0.9*CS%CFL_trunc) * (G%areaT(i,j+1) / (dt * G%dx_Cv(i,J)))
-        if (h(i,j,k) + h(i,j+1,k) > H_report) CS%ntrunc = CS%ntrunc + 1
+        if (((i >= G%isc) .and. (i <= G%iec) .and. (J >= G%jsc) .and. (J <= G%jec)) .and. &
+            (CS%h_v(i,J,k) > H_report)) CS%ntrunc = CS%ntrunc + 1
       elseif ((v(i,J,k) * (dt * G%dx_Cv(i,J))) * G%IareaT(i,j) > CS%CFL_trunc) then
         v(i,J,k) = (0.9*CS%CFL_trunc) * (G%areaT(i,j) / (dt * G%dx_Cv(i,J)))
-        if (h(i,j,k) + h(i,j+1,k) > H_report) CS%ntrunc = CS%ntrunc + 1
+        if (((i >= G%isc) .and. (i <= G%iec) .and. (J >= G%jsc) .and. (J <= G%jec)) .and. &
+            (CS%h_v(i,J,k) > H_report)) CS%ntrunc = CS%ntrunc + 1
       endif
     enddo ; enddo ; enddo
   endif