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Automatic dynamics-splitting defaults to the SE dycore + clean-up #1656

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0a5880a
Add automatic dynamics-splitting defaults to the SE dycore
PeterHjortLauritzen Aug 22, 2026
7dcab0a
remove un-used un-tested namelist options
PeterHjortLauritzen Aug 22, 2026
69f58f4
remove un-used variables
PeterHjortLauritzen Aug 22, 2026
bfb2951
clean-up and edit Changelog
PeterHjortLauritzen Aug 22, 2026
6071ff6
bug in SE dycore (from Haipeng/Claude)
PeterHjortLauritzen Aug 25, 2026
8f94303
improve ChangeLog
PeterHjortLauritzen Aug 25, 2026
56a9d3f
clean-up
PeterHjortLauritzen Aug 25, 2026
3e26f96
reviewer suggested change
PeterHjortLauritzen Aug 25, 2026
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3 changes: 0 additions & 3 deletions bld/build-namelist
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Original file line number Diff line number Diff line change
Expand Up @@ -4355,9 +4355,6 @@ if ($dyn =~ /se/) {
se_vert_remap_uvTq_alg
se_vert_remap_tracer_alg
se_fvm_supercycling
se_fvm_supercycling_jet
se_kmin_jet
se_kmax_jet
se_molecular_diff
se_pgf_formulation
se_dribble_in_rsplit_loop
Expand Down
29 changes: 14 additions & 15 deletions bld/namelist_files/namelist_defaults_cam.xml
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Expand Up @@ -3240,17 +3240,13 @@

<se_hypervis_scaling se_refined_mesh="1" hypervis_type="tensor" >3.22D0 </se_hypervis_scaling>

<se_hypervis_subcycle > 3 </se_hypervis_subcycle>
<se_hypervis_subcycle >-1 </se_hypervis_subcycle>
<se_hypervis_subcycle waccm_phys="1" model_top="mt" > 3 </se_hypervis_subcycle>
<se_hypervis_subcycle waccm_phys="1" > 2 </se_hypervis_subcycle>
<se_hypervis_subcycle hgrid="ne16np4" > 3 </se_hypervis_subcycle>
<se_hypervis_subcycle hgrid="ne16np4" model_top="lt" > 1 </se_hypervis_subcycle>
<se_hypervis_subcycle hgrid="ne16np4" waccm_phys="1" model_top="none"> 10 </se_hypervis_subcycle>
<se_hypervis_subcycle hgrid="ne16np4" waccm_phys="1" waccmx="0" model_top="none"> 9 </se_hypervis_subcycle>
<se_hypervis_subcycle hgrid="ne30np4" waccm_phys="1" waccmx="0" model_top="none"> 8 </se_hypervis_subcycle>
<se_hypervis_subcycle hgrid="ne30np4" waccm_phys="1" waccmx="1" model_top="none"> 5 </se_hypervis_subcycle>
<se_hypervis_subcycle hgrid="ne30np4" model_top="lt" > 2 </se_hypervis_subcycle>
<se_hypervis_subcycle hgrid="ne30np4" model_top="mt" > 3 </se_hypervis_subcycle>
<se_hypervis_subcycle hgrid="ne0np4.ARCTIC.ne30x4" > 2 </se_hypervis_subcycle>
<se_hypervis_subcycle hgrid="ne0np4.POLARCAP.ne30x4" > 2 </se_hypervis_subcycle>
<se_hypervis_subcycle hgrid="ne0np4CONUS.ne30x8" > 1 </se_hypervis_subcycle>
Expand All @@ -3262,16 +3258,15 @@
<se_hypervis_subcycle hgrid="ne30np4" model_top="ht" > 18</se_hypervis_subcycle>
<se_hypervis_subcycle hgrid="ne30np4" model_top="xt" > 18</se_hypervis_subcycle>
<se_hypervis_subcycle waccmx="1" hgrid="ne120np4" nlev="273" > 30</se_hypervis_subcycle>
<se_hypervis_subcycle hgrid="ne120np4" model_top="mt" > 2 </se_hypervis_subcycle>
<se_hypervis_subcycle hgrid="ne3np4" > 3 </se_hypervis_subcycle>
<se_hypervis_subcycle hgrid="ne0np4TESTONLY.ne5x4" > 3 </se_hypervis_subcycle>

<se_hypervis_subcycle_sponge > 1 </se_hypervis_subcycle_sponge>
<se_hypervis_subcycle_sponge hgrid="ne30np4" model_top="mt" > 3 </se_hypervis_subcycle_sponge>
<se_hypervis_subcycle_sponge >-1 </se_hypervis_subcycle_sponge>
<se_hypervis_subcycle_sponge hgrid="ne30np4" model_top="mt" waccm_phys="1" > 3 </se_hypervis_subcycle_sponge>
<se_hypervis_subcycle_sponge hgrid="ne16np4" waccm_phys="1" waccmx="0" > 2 </se_hypervis_subcycle_sponge>
<se_hypervis_subcycle_sponge hgrid="ne30np4" waccm_phys="1" waccmx="0" > 4 </se_hypervis_subcycle_sponge>
<se_hypervis_subcycle_sponge waccmx="1" > 20 </se_hypervis_subcycle_sponge>
<se_hypervis_subcycle_sponge hgrid="ne30np4" waccmx="1" model_top="none" > 60 </se_hypervis_subcycle_sponge>
<se_hypervis_subcycle_sponge hgrid="ne120np4" > 4 </se_hypervis_subcycle_sponge>
<se_hypervis_subcycle_sponge hgrid="ne0np4.ARCTIC.ne30x4" > 2 </se_hypervis_subcycle_sponge>
<se_hypervis_subcycle_sponge hgrid="ne0np4.POLARCAP.ne30x4" > 2 </se_hypervis_subcycle_sponge>
<se_hypervis_subcycle_sponge hgrid="ne0np4CONUS.ne30x8" > 5 </se_hypervis_subcycle_sponge>
Expand All @@ -3282,12 +3277,13 @@
<se_hypervis_subcycle_sponge hgrid="ne30np4" model_top="ht" > 4 </se_hypervis_subcycle_sponge>
<se_hypervis_subcycle_sponge hgrid="ne30np4" model_top="xt" > 40 </se_hypervis_subcycle_sponge>
<se_hypervis_subcycle_sponge waccmx="1" hgrid="ne120np4" nlev="273" > 180</se_hypervis_subcycle_sponge>
<se_hypervis_subcycle_sponge hgrid="ne120np4" model_top="mt" > 10 </se_hypervis_subcycle_sponge>
<se_hypervis_subcycle_sponge hgrid="ne0np4.ARCTIC.ne30x4" model_top="mt" > 3 </se_hypervis_subcycle_sponge>
<se_hypervis_subcycle_sponge hgrid="ne0np4.POLARCAP.ne30x4" model_top="mt" > 3 </se_hypervis_subcycle_sponge>
<se_hypervis_subcycle_sponge hgrid="ne0np4CONUS.ne30x8" model_top="mt" > 6 </se_hypervis_subcycle_sponge>
<se_hypervis_subcycle_sponge hgrid="ne0np4.ARCTICGRIS.ne30x8" model_top="mt" > 6 </se_hypervis_subcycle_sponge>
<se_hypervis_subcycle_sponge hgrid="ne0np4.NATL.ne30x8" model_top="mt" > 6 </se_hypervis_subcycle_sponge>
<se_hypervis_subcycle_sponge hgrid="ne3np4" > 1 </se_hypervis_subcycle_sponge>
<se_hypervis_subcycle_sponge hgrid="ne0np4TESTONLY.ne5x4" > 1 </se_hypervis_subcycle_sponge>


<se_hypervis_subcycle_q>1 </se_hypervis_subcycle_q>
Expand Down Expand Up @@ -3372,25 +3368,28 @@
<se_nsplit hgrid="ne0np4.ARCTICGRIS.ne30x8" model_top="mt" > 4 </se_nsplit>
<se_nsplit hgrid="ne0np4.NATL.ne30x8" model_top="mt" > 4 </se_nsplit>

<se_rsplit > 3 </se_rsplit>
<se_rsplit >-1</se_rsplit>
<se_rsplit waccm_phys="1" model_top="mt" > 3 </se_rsplit>
<se_rsplit waccm_phys="1" waccmx="0" > 2 </se_rsplit>
<se_rsplit model_top="ht" > 2 </se_rsplit>
<se_rsplit waccmx="1" > 4 </se_rsplit>
<se_rsplit hgrid="ne16np4" waccmx="1" model_top="none" > 2 </se_rsplit>
<se_rsplit hgrid="ne0np4CONUS.ne30x8" waccm_phys="1" > 3 </se_rsplit>
<se_rsplit waccmx="1" hgrid="ne120np4" nlev="273" > 5 </se_rsplit>
<se_rsplit hgrid="ne120np4" model_top="mt" > 3 </se_rsplit>
<se_rsplit hgrid="ne0np4.ARCTIC.ne30x4" model_top="mt" > 6 </se_rsplit>
<se_rsplit hgrid="ne0np4.POLARCAP.ne30x4" model_top="mt" > 6 </se_rsplit>
<se_rsplit hgrid="ne0np4CONUS.ne30x8" model_top="mt" > 5 </se_rsplit>
<se_rsplit hgrid="ne0np4.ARCTICGRIS.ne30x8" model_top="mt" > 5 </se_rsplit>
<se_rsplit hgrid="ne0np4.NATL.ne30x8" model_top="mt" > 5 </se_rsplit>
<se_rsplit hgrid="ne3np4" > 3 </se_rsplit>
<se_rsplit hgrid="ne0np4CONUS.ne30x8" > 3 </se_rsplit>
<se_rsplit hgrid="ne0np4.ARCTIC.ne30x4" > 3 </se_rsplit>
<se_rsplit hgrid="ne0np4.POLARCAP.ne30x4" > 3 </se_rsplit>
<se_rsplit hgrid="ne0np4.ARCTICGRIS.ne30x8" > 3 </se_rsplit>
<se_rsplit hgrid="ne0np4.NATL.ne30x8" > 3 </se_rsplit>
<se_rsplit hgrid="ne0np4TESTONLY.ne5x4" > 3 </se_rsplit>

<se_fvm_supercycling>-1</se_fvm_supercycling>
<se_fvm_supercycling_jet>-1</se_fvm_supercycling_jet>
<se_kmin_jet>-1</se_kmin_jet>
<se_kmax_jet>-1</se_kmax_jet>

<se_statediag_numtrac>3</se_statediag_numtrac>

Expand Down
56 changes: 3 additions & 53 deletions bld/namelist_files/namelist_definition.xml
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Expand Up @@ -8601,12 +8601,14 @@ Default: 0 (i.e., not used)
<entry id="se_hypervis_subcycle" type="integer" category="se"
group="dyn_se_inparm" valid_values="" >
Number of hyperviscosity subcycles per dynamics timestep.
Set to -1 to have the value selected automatically at runtime from the CFL stability limits.
Default: Set by build-namelist
</entry>

<entry id="se_hypervis_subcycle_sponge" type="integer" category="se"
group="dyn_se_inparm" valid_values="" >
Number of hyperviscosity subcycles per dynamics timestep in sponge del2 diffusion.
Set to -1 to have the value selected automatically at runtime from the CFL stability limits.
Default: Set by build-namelist
</entry>

Expand Down Expand Up @@ -8756,31 +8758,6 @@ Number of SE rsplit time-steps CSLAM supercycles
rsplit/se_fvm_supercycling must be an integer
</entry>

<entry id="se_fvm_supercycling_jet" type="integer" category="se"
group="dyn_se_inparm" valid_values="" >
Number of SE rsplit time-steps CSLAM supercycles in the jet region
(which is specified by kmin_jet and kmax_jet)
rsplit/se_fvm_supercycling_jet must be an integer
se_fvm_supercycling_jet/se_fvm_supercyling must be an integer
</entry>

<entry id="se_kmin_jet" type="integer" category="se"
group="dyn_se_inparm" valid_values="" >
Min level index where CSLAM runs with se_fvm_supercycling_jet
(if se_fvm_supercycling_jet.ne.se_fvm_supercycling) or
min index where are Courant number increment is active
(se_large_Courant_incr=.true.)
</entry>

<entry id="se_kmax_jet" type="integer" category="se"
group="dyn_se_inparm" valid_values="" >
Max level index where CSLAM runs with se_fvm_supercycling_jet
(if se_fvm_supercycling_jet.ne.se_fvm_supercycling) or
max index where are Courant number increment is active
(se_large_Courant_incr=.true.)
</entry>


<entry id="se_qsplit" type="integer" category="se"
group="dyn_se_inparm" valid_values="" >
Tracer advection is done every qsplit dynamics timesteps.
Expand All @@ -8796,6 +8773,7 @@ Default: FALSE
<entry id="se_rsplit" type="integer" category="se"
group="dyn_se_inparm" valid_values="" >
Vertically lagrangian code vertically remaps every rsplit tracer timesteps.
Set to -1 to have the value selected automatically at runtime from the CFL stability limits.
Default: Set by build-namelist.
</entry>

Expand Down Expand Up @@ -8881,34 +8859,6 @@ differences into the simulation.
Default: .false.
</entry>

<!-- Nudging -->
<entry id="se_met_nudge_u" type="real" category="se"
group="dyn_se_inparm" valid_values="" >
Nudging factor for prescribed winds in SE dycore
Units: 1/sec
Default: 2e-5
</entry>

<entry id="se_met_nudge_t" type="real" category="se"
group="dyn_se_inparm" valid_values="" >
Nudging factor for prescribed temperature in SE dycore
Units: 1/sec
Default: 2e-5
</entry>

<entry id="se_met_nudge_p" type="real" category="se"
group="dyn_se_inparm" valid_values="" >
Nudging factor for prescribed surface pressure in SE dycore
Units: 1/sec
Default: 0.0
</entry>

<entry id="se_met_tevolve" type="integer" category="se"
group="dyn_se_inparm" valid_values="0,1" >
Switch to turn on/off time evolution of dynamics nudging
Default: 0
</entry>

<!-- Physics grid entries -->
<entry id="se_fv_nphys" type="integer" category="se"
group="dyn_se_inparm" valid_values="" >
Expand Down
114 changes: 114 additions & 0 deletions doc/ChangeLog
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@@ -1,5 +1,119 @@
===============================================================

Tag name:
Originator(s): pel
Date: August 22, 2026
One-line Summary: Automatic dynamics-splitting defaults for the SE dycore; remove unused SE namelist options
Github PR URL:

Purpose of changes (include the issue number and title text for each relevant GitHub issue):

- #1655 Add automatic dynamics-splitting defaults to the SE dycore

- #969 Clean-up unused and/or unsupported namelist options in SE dycore

Describe any changes made to build system:
- bld/build-namelist: removed se_fvm_supercycling_jet, se_kmin_jet, and
se_kmax_jet from the SE dycore namelist variable list.

Describe any changes made to the namelist:

Changed defaults (automatic dynamics splitting):
- se_rsplit, se_hypervis_subcycle, se_hypervis_subcycle_sponge default
changed to -1 ("automatic"); the effective value is computed at runtime
from the CFL stability limits. WACCM, WACCM-X, variable-resolution, and
ne3 grids are pinned to their previous explicit values, so those
configurations are unchanged.

Removed namelist options (unused/untested):
- se_fvm_supercycling_jet, se_kmin_jet, se_kmax_jet
- se_met_nudge_u, se_met_nudge_t, se_met_nudge_p, se_met_tevolve

List any changes to the defaults for the boundary datasets: N/A

Describe any substantial timing or memory changes: N/A

Code reviewed by:

List all files eliminated:

List all files added and what they do:

List all existing files that have been modified, and describe the changes:

M bld/build-namelist
- remove se_fvm_supercycling_jet/se_kmin_jet/se_kmax_jet from the
SE dycore variable list
M bld/namelist_files/namelist_definition.xml
- document the -1 "automatic" sentinel for the split variables;
remove the jet-supercycling and se_met_nudge_* entries
M bld/namelist_files/namelist_defaults_cam.xml
- set se_rsplit/se_hypervis_subcycle/se_hypervis_subcycle_sponge
defaults to -1; pin WACCM/WACCM-X/variable-resolution/ne3 to
their prior values; remove jet-supercycling defaults
M src/dynamics/se/dyn_comp.F90
- accept the rsplit == -1 sentinel in dyn_readnl; remove the
se_fvm_supercycling_jet / se_kmin_jet / se_kmax_jet and
variable_nsplit plumbing
M src/dynamics/se/dyn_grid.F90
- dyn_grid_init: resolve automatic (-1) rsplit and the fvm
supercycling default from the CFL stability limits
M src/dynamics/se/dycore/global_norms_mod.F90
- compute the automatic hyperviscosity subcycle counts from the
grid stability constants in print_cfl
M src/dynamics/se/dycore/prim_driver_mod.F90
- remove variable_nsplit machinery; the CFL dt computation is now
done in print_cfl
M src/dynamics/se/dycore/prim_state_mod.F90
- remove variable_nsplit / nsplit_baseline / rsplit_baseline
M src/dynamics/se/dycore/se_dyn_time_mod.F90
- remove variable_nsplit plumbing
M src/dynamics/se/dycore/control_mod.F90
- remove 'variable_nsplit' and other unused control variables.
M src/dynamics/se/dycore/dimensions_mod.F90
- remove kmin_jet, kmax_jet, and fvm_supercycling_jet declarations
M src/dynamics/se/dycore/fvm_mod.F90
- remove jet-supercycling logic
M src/dynamics/se/dycore/fvm_consistent_se_cslam.F90
- large_Courant_incr now operates over the full column (1..nlev)
instead of the removed [kmin_jet, kmax_jet] jet region

If there were any failures reported from running test_driver.sh on any test
platform, and checkin with these failures has been OK'd by the gatekeeper,
then copy the lines from the td.*.status files for the failed tests to the
appropriate machine below. All failed tests must be justified.

derecho/intel/aux_cam:

derecho/nvhpc/aux_cam:

izumi/nag/aux_cam:

izumi/gnu/aux_cam:

CAM tag used for the baseline comparison tests if different than previous
tag: cam6_4_196

Summarize any changes to answers, i.e.,
- what code configurations: SE dycore. Low/mid-top uniform-grid
configurations whose automatically selected se_hypervis_subcycle is smaller
than the previous hard-coded value change answers. Observed in the aux_cam
SE suite for:
ERI_D_Ln18.ne16pg3_ne16pg3_mt232.FHIST_C4 (hypervis_subcycle 3 -> 1)
ERP_Ln9.ne30pg3_ne30pg3_mg17.FCnudged (hypervis_subcycle 3 -> 2)
SMS_Ld1.ne30pg3_ne30pg3_mg17.FC2010climo (hypervis_subcycle 3 -> 2)
All other SE configurations (including all WACCM, WACCM-X,
variable-resolution, and ne3 grids, which are pinned) are bit-for-bit.
The namelist-option cleanup (#969) is bit-for-bit by construction (removal
of unused/dead code and orphaned definition entries).
- what platforms/compilers: derecho/intel
- nature of change: larger than roundoff (fewer hyperviscosity subcycles where
the CFL stability estimate permits); same climate <CONFIRM / describe any
climate evaluation>.

===============================================================
===============================================================

Tag name: cam6_4_197
Originator(s): jimmielin
Date: August 22, 2026
Expand Down
15 changes: 0 additions & 15 deletions src/dynamics/se/dycore/control_mod.F90
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Expand Up @@ -13,7 +13,6 @@ module control_mod

integer, public :: tstep_type= 0 ! 0 = leapfrog
! 1 = RK (foward-in-time)
integer, public :: rk_stage_user = 0 ! number of RK stages to use
integer, public :: ftype = 2 ! Forcing Type
integer, public :: ftype_conserve = 1 !conserve momentum (dp*u)
integer, public :: dribble_in_rsplit_loop = 0
Expand All @@ -22,38 +21,26 @@ module control_mod
integer, public :: qsplit = 1 ! ratio of dynamics tsteps to tracer tsteps
integer, public :: rsplit =-1 ! for vertically lagrangian dynamics, apply remap
! every rsplit tracer timesteps
logical, public :: variable_nsplit=.false.

logical, public :: refined_mesh

integer, public :: vert_remap_q_alg = 10


integer, public :: cubed_sphere_map = -1 ! -1 = chosen at run time
! 0 = equi-angle Gnomonic (default)
! 1 = equi-spaced Gnomonic (not yet coded)
! 2 = element-local projection (for var-res)
! 3 = parametric (not yet coded)

!tolerance to define smth small, was introduced for lim 8 in 2d and 3d
real (kind=r8), public, parameter :: tol_limiter=1.0e-13_r8

integer , public :: limiter_option = 0

integer , public :: partmethod ! partition methods
character(len=MAX_STRING_LEN) , public :: topology ! options: "cube" is supported
integer , public :: tasknum
integer , public :: remapfreq ! remap frequency of synopsis of system state (steps)
character(len=MAX_STRING_LEN) :: remap_type ! selected remapping option
integer , public :: statefreq ! output frequency of synopsis of system state (steps)
integer , public :: runtype
integer , public :: timerdetail
integer , public :: numnodes
integer , public :: multilevel

character(len=MAX_STRING_LEN) , public :: columnpackage

integer , public :: maxits ! max iterations of solver
real (kind=r8), public :: tol ! solver tolerance (convergence criteria)

integer , public :: fine_ne = -1 ! set for refined exodus meshes (variable viscosity)
Expand Down Expand Up @@ -83,8 +70,6 @@ module control_mod
integer, public :: hypervis_subcycle=1 ! number of subcycles for hyper viscsosity timestep
integer, public :: hypervis_subcycle_sponge=1 ! number of subcycles for hyper viscsosity timestep in sponge
integer, public :: hypervis_subcycle_q=1 ! number of subcycles for hyper viscsosity timestep on TRACERS
integer, public :: psurf_vis = 0 ! 0 = use laplace on eta surfaces
! 1 = use (approx.) laplace on p surfaces

real (kind=r8), public :: hypervis_power=0 ! if not 0, use variable hyperviscosity based on element area
real (kind=r8), public :: hypervis_scaling=0 ! use tensor hyperviscosity
Expand Down
4 changes: 1 addition & 3 deletions src/dynamics/se/dycore/dimensions_mod.F90
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Expand Up @@ -55,9 +55,7 @@ module dimensions_mod
integer, parameter, public :: ubc = nc+nhc
logical, public :: large_Courant_incr

integer, public :: kmin_jet,kmax_jet !min and max level index for the jet
integer, public :: fvm_supercycling
integer, public :: fvm_supercycling_jet
integer, public :: fvm_supercycling

integer, allocatable, public :: kord_tr(:), kord_tr_cslam(:)

Expand Down
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