Merge pull request #1 from nikizadehgfdl/obgc_obc_seg_data_update_period

Obgc obc seg data update period

src/core/MOM.F90

@@ -262,6 +262,10 @@ module MOM
                                      !! calculated, and if it is 0, dtbt is calculated every step.
   type(time_type) :: dtbt_reset_interval !< A time_time representation of dtbt_reset_period.
   type(time_type) :: dtbt_reset_time !< The next time DTBT should be calculated.
+  real            :: dt_obc_seg_period!< The time interval between OBC segment updates for OBGC tracers
+  type(time_type) :: dt_obc_seg_interval !< A time_time representation of dt_obc_seg_period.
+  type(time_type) :: dt_obc_seg_time !< The next time OBC segment update is applied to OBGC tracers.
+
   real, dimension(:,:), pointer :: frac_shelf_h => NULL() !< fraction of total area occupied
                                      !! by ice shelf [nondim]
   real, dimension(:,:,:), pointer :: &
@@ -1054,6 +1058,17 @@ subroutine step_MOM_dynamics(forces, p_surf_begin, p_surf_end, dt, dt_thermo, &
         CS%dtbt_reset_time = CS%dtbt_reset_time + CS%dtbt_reset_interval
       endif
     endif
+    !OBC segment data update for some fields can be less frequent than others 
+    if(associated(CS%OBC)) then
+      CS%OBC%update_OBC_seg_data = .false.
+      if (CS%dt_obc_seg_period == 0.0) CS%OBC%update_OBC_seg_data = .true.
+      if (CS%dt_obc_seg_period > 0.0) then
+       if (Time_local >= CS%dt_obc_seg_time) then  !### Change >= to > here.
+        CS%OBC%update_OBC_seg_data = .true.
+        CS%dt_obc_seg_time = CS%dt_obc_seg_time + CS%dt_obc_seg_interval
+       endif
+      endif
+    endif
 
     call step_MOM_dyn_split_RK2(u, v, h, CS%tv, CS%visc, Time_local, dt, forces, &
                 p_surf_begin, p_surf_end, CS%uh, CS%vh, CS%uhtr, CS%vhtr, &
@@ -1924,6 +1939,13 @@ subroutine initialize_MOM(Time, Time_init, param_file, dirs, CS, restart_CSp, &
                  "DTBT will be set every dynamics time step. The default "//&
                  "is set by DT_THERM.  This is only used if SPLIT is true.", &
                  units="s", default=default_val, do_not_read=(dtbt > 0.0))
+
+    CS%dt_obc_seg_period = -1.0
+    call get_param(param_file, "MOM", "DT_OBC_SEG_UPDATE_OBGC", CS%dt_obc_seg_period, &
+                 "The time between OBC segment data updates for OBGC tracers. "//&
+                 "The default is set to DT.  This is only used if SPLIT is true.", &
+                 units="s", default=CS%dt)
+
   endif
 
   ! This is here in case these values are used inappropriately.
@@ -2622,6 +2644,19 @@ subroutine initialize_MOM(Time, Time_init, param_file, dirs, CS, restart_CSp, &
         CS%dtbt_reset_time = CS%dtbt_reset_time - CS%dtbt_reset_interval
       endif
     endif
+    !Set OBC segment data update period
+    if (associated(CS%OBC) .and. CS%dt_obc_seg_period > 0.0) then
+      CS%dt_obc_seg_interval = real_to_time(CS%dt_obc_seg_period)
+      ! Set dt_obc_seg_time to be the next even multiple of dt_obc_seg_interval.
+      CS%dt_obc_seg_time = Time_init + CS%dt_obc_seg_interval * &
+                                 ((Time - Time_init) / CS%dt_obc_seg_interval)
+      if ((CS%dt_obc_seg_time > Time) .and. CS%OBC%update_OBC_seg_data) then
+        ! Back up dtbt_reset_time one interval to force dtbt to be calculated,
+        ! because the restart was not aligned with the interval to recalculate
+        ! dtbt, and dtbt was not read from a restart file.
+        CS%dt_obc_seg_time = CS%dt_obc_seg_time - CS%dt_obc_seg_interval
+      endif
+    endif
   elseif (CS%use_RK2) then
     call initialize_dyn_unsplit_RK2(CS%u, CS%v, CS%h, Time, G, GV, US,     &
             param_file, diag, CS%dyn_unsplit_RK2_CSp, restart_CSp,         &

src/core/MOM_open_boundary.F90

@@ -241,6 +241,8 @@ module MOM_open_boundary
   logical :: user_BCs_set_globally = .false.          !< True if any OBC_USER_CONFIG is set
                                                       !! for input from user directory.
   logical :: update_OBC = .false.                     !< Is OBC data time-dependent
+  logical :: update_OBC_seg_data = .false.           !< Is it the time for OBC segment data update for fields that 
+                                                      !! require less frequent update
   logical :: needs_IO_for_data = .false.              !< Is any i/o needed for OBCs
   logical :: zero_vorticity = .false.                 !< If True, sets relative vorticity to zero on open boundaries.
   logical :: freeslip_vorticity = .false.             !< If True, sets normal gradient of tangential velocity to zero
@@ -3897,6 +3899,10 @@ subroutine update_OBC_segment_data(G, GV, US, OBC, tv, h, Time)
     allocate(h_stack(GV%ke))
     h_stack(:) = 0.0
     do m = 1,segment%num_fields
+      !This field may not require a high frequency OBC segment update and might be allowed
+      !a less frequent update as set by the parameter update_OBC_period_max in MOM.F90.  
+      !Cycle if it is not the time to update OBC segment data for this field.
+      if (trim(segment%field(m)%genre) == 'obgc' .and. (.not. OBC%update_OBC_seg_data)) cycle  
       if (segment%field(m)%fid > 0) then
         siz(1)=size(segment%field(m)%buffer_src,1)
         siz(2)=size(segment%field(m)%buffer_src,2)