+Use answer_date to specify remapping

  Replace answers_2018 arguments with answer_date arguments to specify the
version of expressions used in a number of vertical or horizontal regridding
calls.  In some cases, this also involves replacing one of the elements in an
opaque type.  It can also involve reading (but not yet logging) the new runtime
parameter DEFAULT_ANSWER_DATE, but if it not set the results are unchanged from
before.  There is also a new optional argument, remap_answer_date, to
wave_speed_init and wave_speed_set_param.  Some comments were also added to
describe real variables in VarMix_init.  All answers are bitwise identical.

src/core/MOM_open_boundary.F90

@@ -321,9 +321,10 @@ module MOM_open_boundary
   real :: ramp_value                        !< If ramp is True, where we are on the ramp from
                                             !! zero to one [nondim].
   type(time_type) :: ramp_start_time        !< Time when model was started.
-  logical :: answers_2018   !< If true, use the order of arithmetic and expressions for remapping
-                            !! that recover the answers from the end of 2018.  Otherwise, use more
-                            !! robust and accurate forms of mathematically equivalent expressions.
+  integer :: remap_answer_date  !< The vintage of the order of arithmetic and expressions to use
+                                !! for remapping.  Values below 20190101 recover the remapping
+                                !! answers from 2018, while higher values use more robust
+                                !! forms of the same remapping expressions.
 end type ocean_OBC_type
 
 !> Control structure for open boundaries that read from files.
@@ -371,7 +372,11 @@ subroutine open_boundary_config(G, US, param_file, OBC)
   character(len=1024) :: segment_str      ! The contents (rhs) for parameter "segment_param_str"
   character(len=200) :: config1          ! String for OBC_USER_CONFIG
   real               :: Lscale_in, Lscale_out ! parameters controlling tracer values at the boundaries [L ~> m]
-  logical :: answers_2018, default_2018_answers
+  logical :: answers_2018   ! If true, use the order of arithmetic and expressions for remapping
+                            ! that recover the answers from the end of 2018.  Otherwise, use more
+                            ! robust and accurate forms of mathematically equivalent expressions.
+  integer :: default_answer_date  ! The default setting for the various ANSWER_DATE flags.
+  logical :: default_2018_answers ! The default setting for the various 2018_ANSWERS flags.
   logical :: check_reconstruction, check_remapping, force_bounds_in_subcell
   character(len=64)  :: remappingScheme
   ! This include declares and sets the variable "version".
@@ -618,18 +623,26 @@ subroutine open_boundary_config(G, US, param_file, OBC)
           "If true, the values on the intermediate grid used for remapping "//&
           "are forced to be bounded, which might not be the case due to "//&
           "round off.", default=.false.,do_not_log=.true.)
+    call get_param(param_file, mdl, "DEFAULT_ANSWER_DATE", default_answer_date, &
+                 "This sets the default value for the various _ANSWER_DATE parameters.", &
+                 default=99991231, do_not_log=.true.)
     call get_param(param_file, mdl, "DEFAULT_2018_ANSWERS", default_2018_answers, &
                  "This sets the default value for the various _2018_ANSWERS parameters.", &
-                 default=.false.)
-    call get_param(param_file, mdl, "REMAPPING_2018_ANSWERS", OBC%answers_2018, &
+                 default=(default_answer_date<20190101))
+    call get_param(param_file, mdl, "REMAPPING_2018_ANSWERS", answers_2018, &
                  "If true, use the order of arithmetic and expressions that recover the "//&
                  "answers from the end of 2018.  Otherwise, use updated and more robust "//&
                  "forms of the same expressions.", default=default_2018_answers)
+    if (answers_2018) then
+      OBC%remap_answer_date = 20181231
+    else
+      OBC%remap_answer_date = 20190101
+    endif
 
     allocate(OBC%remap_CS)
     call initialize_remapping(OBC%remap_CS, remappingScheme, boundary_extrapolation = .false., &
                check_reconstruction=check_reconstruction, check_remapping=check_remapping, &
-               force_bounds_in_subcell=force_bounds_in_subcell, answers_2018=OBC%answers_2018)
+               force_bounds_in_subcell=force_bounds_in_subcell, answer_date=OBC%remap_answer_date)
 
   endif ! OBC%number_of_segments > 0
 
@@ -3718,7 +3731,7 @@ subroutine update_OBC_segment_data(G, GV, US, OBC, tv, h, Time)
 
   if (OBC%add_tide_constituents) time_delta = US%s_to_T * time_type_to_real(Time - OBC%time_ref)
 
-  if (.not. OBC%answers_2018) then
+  if (OBC%remap_answer_date >= 20190101) then
     h_neglect = GV%H_subroundoff ; h_neglect_edge = GV%H_subroundoff
   elseif (GV%Boussinesq) then
     h_neglect = GV%m_to_H * 1.0e-30 ; h_neglect_edge = GV%m_to_H * 1.0e-10

src/diagnostics/MOM_diagnostics.F90

@@ -1551,7 +1551,13 @@ subroutine MOM_diagnostics_init(MIS, ADp, CDp, Time, G, GV, US, param_file, diag
   character(len=40)  :: mdl = "MOM_diagnostics" ! This module's name.
   character(len=48) :: thickness_units, flux_units
   logical :: use_temperature, adiabatic
-  logical :: default_2018_answers, remap_answers_2018
+  integer :: default_answer_date  ! The default setting for the various ANSWER_DATE flags.
+  logical :: default_2018_answers ! The default setting for the various 2018_ANSWERS flags.
+  integer :: remap_answer_date    ! The vintage of the order of arithmetic and expressions to use
+                                  ! for remapping.  Values below 20190101 recover the remapping
+                                  ! answers from 2018, while higher values use more robust
+                                  ! forms of the same remapping expressions.
+  logical :: remap_answers_2018
 
   CS%initialized = .true.
 
@@ -1579,13 +1585,22 @@ subroutine MOM_diagnostics_init(MIS, ADp, CDp, Time, G, GV, US, param_file, diag
   call get_param(param_file, mdl, "INTERNAL_WAVE_SPEED_BETTER_EST", better_speed_est, &
                  "If true, use a more robust estimate of the first mode wave speed as the "//&
                  "starting point for iterations.", default=.true.)
+  call get_param(param_file, mdl, "DEFAULT_ANSWER_DATE", default_answer_date, &
+                 "This sets the default value for the various _ANSWER_DATE parameters.", &
+                 default=99991231, do_not_log=.true.)
   call get_param(param_file, mdl, "DEFAULT_2018_ANSWERS", default_2018_answers, &
                  "This sets the default value for the various _2018_ANSWERS parameters.", &
-                 default=.false.)
+                 default=(default_answer_date<20190101))
   call get_param(param_file, mdl, "REMAPPING_2018_ANSWERS", remap_answers_2018, &
                  "If true, use the order of arithmetic and expressions that recover the "//&
                  "answers from the end of 2018.  Otherwise, use updated and more robust "//&
                  "forms of the same expressions.", default=default_2018_answers)
+  if (remap_answers_2018) then
+    remap_answer_date = 20181231
+  else
+    remap_answer_date = 20190101
+  endif
+
   call get_param(param_file, mdl, "SPLIT", split, default=.true., do_not_log=.true.)
 
   if (GV%Boussinesq) then
@@ -1813,7 +1828,7 @@ subroutine MOM_diagnostics_init(MIS, ADp, CDp, Time, G, GV, US, param_file, diag
   if ((CS%id_cg1>0) .or. (CS%id_Rd1>0) .or. (CS%id_cfl_cg1>0) .or. &
       (CS%id_cfl_cg1_x>0) .or. (CS%id_cfl_cg1_y>0) .or. &
       (CS%id_cg_ebt>0) .or. (CS%id_Rd_ebt>0) .or. (CS%id_p_ebt>0)) then
-    call wave_speed_init(CS%wave_speed, remap_answers_2018=remap_answers_2018, &
+    call wave_speed_init(CS%wave_speed, remap_answer_date=remap_answer_date, &
                          better_speed_est=better_speed_est, min_speed=wave_speed_min, &
                          wave_speed_tol=wave_speed_tol)
   endif

src/diagnostics/MOM_wave_speed.F90

@@ -46,9 +46,11 @@ module MOM_wave_speed
                                        !! speeds [nondim]
   type(remapping_CS) :: remapping_CS   !< Used for vertical remapping when calculating equivalent barotropic
                                        !! mode structure.
-  logical :: remap_answers_2018 = .true.  !< If true, use the order of arithmetic and expressions that
-                                       !! recover the remapping answers from 2018.  If false, use more
-                                       !! robust forms of the same remapping expressions.
+  integer :: remap_answer_date = 20181231 !< The vintage of the order of arithmetic and expressions to use
+                                       !! for remapping.  Values below 20190101 recover the remapping
+                                       !! answers from 2018, while higher values use more robust
+                                       !! forms of the same remapping expressions.
+                      !### Change to 99991231?
   type(diag_ctrl), pointer :: diag     !< Diagnostics control structure
 end type wave_speed_CS
 
@@ -558,7 +560,7 @@ subroutine wave_speed(h, tv, G, GV, US, cg1, CS, full_halos, use_ebt_mode, mono_
             do k = 1,kc
               Hc_H(k) = GV%Z_to_H * Hc(k)
             enddo
-            if (CS%remap_answers_2018) then
+            if (CS%remap_answer_date < 20190101) then
               call remapping_core_h(CS%remapping_CS, kc, Hc_H(:), mode_struct, &
                                     nz, h(i,j,:), modal_structure(i,j,:), &
                                     1.0e-30*GV%m_to_H, 1.0e-10*GV%m_to_H)
@@ -1168,7 +1170,7 @@ end subroutine tridiag_det
 
 !> Initialize control structure for MOM_wave_speed
 subroutine wave_speed_init(CS, use_ebt_mode, mono_N2_column_fraction, mono_N2_depth, remap_answers_2018, &
-                           better_speed_est, min_speed, wave_speed_tol)
+                           remap_answer_date, better_speed_est, min_speed, wave_speed_tol)
   type(wave_speed_CS), intent(inout) :: CS  !< Wave speed control struct
   logical, optional, intent(in) :: use_ebt_mode  !< If true, use the equivalent
                                      !! barotropic mode instead of the first baroclinic mode.
@@ -1181,6 +1183,10 @@ subroutine wave_speed_init(CS, use_ebt_mode, mono_N2_column_fraction, mono_N2_de
   logical, optional, intent(in) :: remap_answers_2018 !< If true, use the order of arithmetic and expressions
                                      !! that recover the remapping answers from 2018.  Otherwise
                                      !! use more robust but mathematically equivalent expressions.
+  integer, optional, intent(in) :: remap_answer_date  !< The vintage of the order of arithmetic and expressions
+                                      !! to use for remapping.  Values below 20190101 recover the remapping
+                                      !! answers from 2018, while higher values use more robust
+                                      !! forms of the same remapping expressions.
   logical, optional, intent(in) :: better_speed_est !< If true, use a more robust estimate of the first
                                      !! mode speed as the starting point for iterations.
   real,    optional, intent(in) :: min_speed !< If present, set a floor in the first mode speed
@@ -1199,15 +1205,17 @@ subroutine wave_speed_init(CS, use_ebt_mode, mono_N2_column_fraction, mono_N2_de
 
   call wave_speed_set_param(CS, use_ebt_mode=use_ebt_mode, mono_N2_column_fraction=mono_N2_column_fraction, &
                             better_speed_est=better_speed_est, min_speed=min_speed, wave_speed_tol=wave_speed_tol)
+  !### Uncomment this?      remap_answers_2018=remap_answers_2018, remap_answer_date=remap_answer_date)
 
+  !### The remap_answers_2018 argument is irrelevant, because remapping is hard-coded to use PLM.
   call initialize_remapping(CS%remapping_CS, 'PLM', boundary_extrapolation=.false., &
-                            answers_2018=CS%remap_answers_2018)
+                            answer_date=CS%remap_answer_date)
 
 end subroutine wave_speed_init
 
 !> Sets internal parameters for MOM_wave_speed
 subroutine wave_speed_set_param(CS, use_ebt_mode, mono_N2_column_fraction, mono_N2_depth, remap_answers_2018, &
-                                better_speed_est, min_speed, wave_speed_tol)
+                                remap_answer_date, better_speed_est, min_speed, wave_speed_tol)
   type(wave_speed_CS), intent(inout)  :: CS
                                       !< Control structure for MOM_wave_speed
   logical, optional, intent(in) :: use_ebt_mode  !< If true, use the equivalent
@@ -1221,6 +1229,10 @@ subroutine wave_speed_set_param(CS, use_ebt_mode, mono_N2_column_fraction, mono_
   logical, optional, intent(in) :: remap_answers_2018 !< If true, use the order of arithmetic and expressions
                                       !! that recover the remapping answers from 2018.  Otherwise
                                       !! use more robust but mathematically equivalent expressions.
+  integer, optional, intent(in) :: remap_answer_date  !< The vintage of the order of arithmetic and expressions
+                                      !! to use for remapping.  Values below 20190101 recover the remapping
+                                      !! answers from 2018, while higher values use more robust
+                                      !! forms of the same remapping expressions.
   logical, optional, intent(in) :: better_speed_est !< If true, use a more robust estimate of the first
                                      !! mode speed as the starting point for iterations.
   real,    optional, intent(in) :: min_speed !< If present, set a floor in the first mode speed
@@ -1231,7 +1243,14 @@ subroutine wave_speed_set_param(CS, use_ebt_mode, mono_N2_column_fraction, mono_
   if (present(use_ebt_mode)) CS%use_ebt_mode = use_ebt_mode
   if (present(mono_N2_column_fraction)) CS%mono_N2_column_fraction = mono_N2_column_fraction
   if (present(mono_N2_depth)) CS%mono_N2_depth = mono_N2_depth
-  if (present(remap_answers_2018)) CS%remap_answers_2018 = remap_answers_2018
+  if (present(remap_answers_2018)) then
+    if (remap_answers_2018) then
+      CS%remap_answer_date = 20181231
+    else
+      CS%remap_answer_date = 20190101
+    endif
+  endif
+  if (present(remap_answer_date)) CS%remap_answer_date = remap_answer_date
   if (present(better_speed_est)) CS%better_cg1_est = better_speed_est
   if (present(min_speed)) CS%min_speed2 = min_speed**2
   if (present(wave_speed_tol)) CS%wave_speed_tol = wave_speed_tol

src/framework/MOM_diag_mediator.F90

@@ -3144,7 +3144,15 @@ subroutine diag_mediator_init(G, GV, US, nz, param_file, diag_cs, doc_file_dir)
   ! Local variables
   integer :: ios, i, new_unit
   logical :: opened, new_file
-  logical :: answers_2018, default_2018_answers
+  logical :: remap_answers_2018   ! If true, use the order of arithmetic and expressions that
+                                  ! recover the remapping answers from 2018.  If false, use more
+                                  ! robust forms of the same remapping expressions.
+  integer :: remap_answer_date    ! The vintage of the order of arithmetic and expressions to use
+                                  ! for remapping.  Values below 20190101 recover the remapping
+                                  ! answers from 2018, while higher values use more robust
+                                  ! forms of the same remapping expressions.
+  integer :: default_answer_date  ! The default setting for the various ANSWER_DATE flags.
+  logical :: default_2018_answers ! The default setting for the various 2018_ANSWERS flags.
   character(len=8)   :: this_pe
   character(len=240) :: doc_file, doc_file_dflt, doc_path
   character(len=240), allocatable :: diag_coords(:)
@@ -3171,13 +3179,21 @@ subroutine diag_mediator_init(G, GV, US, nz, param_file, diag_cs, doc_file_dir)
                  'The number of diagnostic vertical coordinates to use. '//&
                  'For each coordinate, an entry in DIAG_COORDS must be provided.', &
                  default=1)
+  call get_param(param_file, mdl, "DEFAULT_ANSWER_DATE", default_answer_date, &
+                 "This sets the default value for the various _ANSWER_DATE parameters.", &
+                 default=99991231, do_not_log=.true.)
   call get_param(param_file, mdl, "DEFAULT_2018_ANSWERS", default_2018_answers, &
                  "This sets the default value for the various _2018_ANSWERS parameters.", &
-                 default=.false.)
-  call get_param(param_file, mdl, "REMAPPING_2018_ANSWERS", answers_2018, &
+                 default=(default_answer_date<20190101))
+  call get_param(param_file, mdl, "REMAPPING_2018_ANSWERS", remap_answers_2018, &
                  "If true, use the order of arithmetic and expressions that recover the "//&
                  "answers from the end of 2018.  Otherwise, use updated and more robust "//&
                  "forms of the same expressions.", default=default_2018_answers)
+  if (remap_answers_2018) then
+    remap_answer_date = 20181231
+  else
+    remap_answer_date = 20190101
+  endif
   call get_param(param_file, mdl, 'USE_GRID_SPACE_DIAGNOSTIC_AXES', diag_cs%grid_space_axes, &
                  'If true, use a grid index coordinate convention for diagnostic axes. ',&
                  default=.false.)
@@ -3200,7 +3216,7 @@ subroutine diag_mediator_init(G, GV, US, nz, param_file, diag_cs, doc_file_dir)
     allocate(diag_cs%diag_remap_cs(diag_cs%num_diag_coords))
     ! Initialize each diagnostic vertical coordinate
     do i=1, diag_cs%num_diag_coords
-      call diag_remap_init(diag_cs%diag_remap_cs(i), diag_coords(i), answers_2018=answers_2018)
+      call diag_remap_init(diag_cs%diag_remap_cs(i), diag_coords(i), answer_date=remap_answer_date)
     enddo
     deallocate(diag_coords)
   endif