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TR-BDF2 Timestepper #379

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530706c
fix plotting scripts
tommbendall Dec 17, 2025
6240f47
add myself to contributors
tommbendall Dec 18, 2025
16cc17c
first attempted implementation of TR-BDF2
tommbendall Jan 4, 2026
d9db20f
trbdf2 compiles and runs, but is unstable
tommbendall Jan 5, 2026
57abec4
Merge remote-tracking branch 'upstream/main' into TBendall/gungho_plo…
tommbendall Jan 13, 2026
9d3d28b
hopefully this fixes my CLA failure
tommbendall Jan 13, 2026
15f69ed
various tr-bdf2 fixes. Runs a gravity wave but has problems with more
tommbendall Jan 20, 2026
b566c2e
it might be working
tommbendall Jan 25, 2026
aa7a6f1
Merge branch 'TBendall/gungho_plot_fix' into TBendall/tr_bdf2
tommbendall Jan 25, 2026
e44d6bf
set tests to use tr-bdf2
tommbendall Jan 26, 2026
e165ad7
allow different inner iterations on different outer iterations
tommbendall Jan 28, 2026
acd4b5e
TR-BDF2 for physics
tommbendall Feb 5, 2026
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3 changes: 2 additions & 1 deletion CONTRIBUTORS.md
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Expand Up @@ -7,4 +7,5 @@
| mo-marqh | mark Hedley | Met Office | 2025-12-11 |
| yaswant | Yaswant Pradhan | Met Office | 2025-12-16 |
| oakleybrunt | Oakley Brunt | Met Office | 2025-12-19 |
| harry-shepherd | Harry Shepherd | Met Office | 2026-01-08 |
| harry-shepherd | Harry Shepherd | Met Office | 2026-01-08 |
| tommbendall | Thomas Bendall | Met Office | 2026-01-13 |
10 changes: 8 additions & 2 deletions applications/gungho_model/example/configuration.nml
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Expand Up @@ -175,7 +175,7 @@ write_fluxes=.false.,
write_minmax_tseries=.false.,
/
&logging
run_log_level='info',
run_log_level='debug',
/
&mixed_solver
eliminate_variables='discrete',
Expand Down Expand Up @@ -276,14 +276,20 @@ timestep_start='1',
alpha=0.55,
dt=3600,
inner_iterations=2,
method='semi_implicit',
method='tr_bdf2',
outer_iterations=2,
runge_kutta_method='forward_euler',
spinup_alpha=.false.,
tau_r=1.0,
tau_t=1.0,
tau_u=0.55,
/
&tr_bdf2
bdf2_inner_iterations=2,
bdf2_outer_iterations=2,
tr_inner_iterations=2,
tr_outer_iterations=2,
/
&transport
adjust_theta=.false.,
adjust_vhv_wind=.true.,
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2 changes: 1 addition & 1 deletion rose-stem/app/gungho_model/opt/rose-app-agnesi_hyd_cart.conf
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Expand Up @@ -27,7 +27,7 @@ smp_init_wind=.true.
u0=20.0

[namelist:io]
diagnostic_frequency=750
diagnostic_frequency=375

[namelist:orography]
orog_init_option='analytic'
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2 changes: 1 addition & 1 deletion rose-stem/app/gungho_model/opt/rose-app-agnesi_nhyd_cart.conf
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Expand Up @@ -24,7 +24,7 @@ smp_init_wind=.true.
u0=10.0

[namelist:io]
diagnostic_frequency=1800
diagnostic_frequency=900

[namelist:orography]
orog_init_option='analytic'
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2 changes: 1 addition & 1 deletion rose-stem/app/gungho_model/opt/rose-app-baroclinic.conf
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Expand Up @@ -13,4 +13,4 @@ test='deep_baroclinic_wave'
profile='deep_baroclinic_perturbed'

[namelist:io]
diagnostic_frequency=240
diagnostic_frequency=120
2 changes: 1 addition & 1 deletion rose-stem/app/gungho_model/opt/rose-app-bell_3d_cart.conf
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Expand Up @@ -27,7 +27,7 @@ smp_init_wind=.true.
u0=10.0

[namelist:io]
diagnostic_frequency=900
diagnostic_frequency=450

[namelist:orography]
orog_init_option='analytic'
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2 changes: 1 addition & 1 deletion rose-stem/app/gungho_model/opt/rose-app-bryan_fritsch-dry.conf
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Expand Up @@ -13,7 +13,7 @@ rotating=.false.
test='bryan_fritsch'

[namelist:io]
diagnostic_frequency=100
diagnostic_frequency=50

[namelist:partitioning]
panel_decomposition='row'
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2 changes: 1 addition & 1 deletion rose-stem/app/gungho_model/opt/rose-app-bryan_fritsch-moist.conf
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Expand Up @@ -16,7 +16,7 @@ use_physics=.true.
test='bryan_fritsch'

[namelist:io]
diagnostic_frequency=100
diagnostic_frequency=50

[namelist:partitioning]
partitioner='planar'
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2 changes: 1 addition & 1 deletion rose-stem/app/gungho_model/opt/rose-app-dcmip200.conf
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Expand Up @@ -13,7 +13,7 @@ test='const_lapse_rate'
profile='constant_uv'

[namelist:io]
diagnostic_frequency=144
diagnostic_frequency=72

[namelist:orography]
orog_init_option='analytic'
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2 changes: 1 addition & 1 deletion rose-stem/app/gungho_model/opt/rose-app-dcmip200_realorog.conf
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Expand Up @@ -16,7 +16,7 @@ test='const_lapse_rate'
profile='constant_uv'

[namelist:io]
diagnostic_frequency=72
diagnostic_frequency=36

[namelist:orography]
orog_init_option='ancil'
2 changes: 1 addition & 1 deletion rose-stem/app/gungho_model/opt/rose-app-dcmip301.conf
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Expand Up @@ -9,7 +9,7 @@ profile='dcmip301'
u0=20.0

[namelist:io]
diagnostic_frequency=36
diagnostic_frequency=18

[namelist:planet]
scaling_factor=125.0
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2 changes: 1 addition & 1 deletion rose-stem/app/gungho_model/opt/rose-app-deep-hot-jupiter.conf
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Expand Up @@ -67,7 +67,7 @@ profile_heights=0.0
profile_size=1

[namelist:io]
diagnostic_frequency=360
diagnostic_frequency=180
write_conservation_diag=.true.

[namelist:physics]
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2 changes: 1 addition & 1 deletion rose-stem/app/gungho_model/opt/rose-app-force_profile.conf
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Expand Up @@ -46,7 +46,7 @@ profile='constant_uv'
smp_init_wind=.true.

[namelist:io]
diagnostic_frequency=10
diagnostic_frequency=5

[!!namelist:multigrid]

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2 changes: 1 addition & 1 deletion rose-stem/app/gungho_model/opt/rose-app-geostrophic.conf
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Expand Up @@ -50,7 +50,7 @@ profile='constant_uv'
smp_init_wind=.true.

[namelist:io]
diagnostic_frequency=144
diagnostic_frequency=72

[!!namelist:multigrid]

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2 changes: 1 addition & 1 deletion rose-stem/app/gungho_model/opt/rose-app-grabowski-clark.conf
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Expand Up @@ -23,7 +23,7 @@ surface_pressure=850.0e2
theta_surf=296.446

[namelist:io]
diagnostic_frequency=50
diagnostic_frequency=25

[namelist:mixed_solver]
fail_on_non_converged=.false.
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2 changes: 1 addition & 1 deletion rose-stem/app/gungho_model/opt/rose-app-io_nwp.conf
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@@ -1,2 +1,2 @@
[namelist:io]
diagnostic_frequency=240
diagnostic_frequency=120
2 changes: 1 addition & 1 deletion rose-stem/app/gungho_model/opt/rose-app-lfric-real-domain.conf
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Expand Up @@ -26,7 +26,7 @@ profile='deep_baroclinic_perturbed'
zero_w2v_wind=.true.

[namelist:io]
diagnostic_frequency=24
diagnostic_frequency=12

[namelist:orography]
orog_init_option='ancil'
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2 changes: 1 addition & 1 deletion rose-stem/app/gungho_model/opt/rose-app-moist_baroclinic_orog.conf
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Expand Up @@ -20,7 +20,7 @@ profile='deep_baroclinic_steady'
zero_w2v_wind=.true.

[namelist:io]
diagnostic_frequency=24
diagnostic_frequency=12

[namelist:orography]
orog_init_option='analytic'
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2 changes: 1 addition & 1 deletion rose-stem/app/gungho_model/opt/rose-app-relax_theta.conf
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Expand Up @@ -43,7 +43,7 @@ profile='constant_uv'
smp_init_wind=.true.

[namelist:io]
diagnostic_frequency=10
diagnostic_frequency=5

[!!namelist:multigrid]

Expand Down
2 changes: 1 addition & 1 deletion rose-stem/app/gungho_model/opt/rose-app-robert-moist-lam.conf
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Expand Up @@ -40,7 +40,7 @@ theta_surf=303.05
lbc_option='analytic'

[namelist:io]
diagnostic_frequency=216
diagnostic_frequency=108

[namelist:mixed_solver]
# The test is initially out of balance, so the solver may not converge to the
Expand Down
2 changes: 1 addition & 1 deletion rose-stem/app/gungho_model/opt/rose-app-robert-moist-smag-l300.conf
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Expand Up @@ -20,7 +20,7 @@ test='warm_bubble'
theta_surf=303.05

[namelist:io]
diagnostic_frequency=432
diagnostic_frequency=216

[namelist:mixed_solver]
# The test is initially out of balance, so the solver may not converge to the
Expand Down
2 changes: 1 addition & 1 deletion rose-stem/app/gungho_model/opt/rose-app-robert-moist-smag.conf
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Expand Up @@ -20,7 +20,7 @@ test='warm_bubble'
theta_surf=303.05

[namelist:io]
diagnostic_frequency=216
diagnostic_frequency=108

[namelist:mixed_solver]
# The test is initially out of balance, so the solver may not converge to the
Expand Down
2 changes: 1 addition & 1 deletion rose-stem/app/gungho_model/opt/rose-app-sbr.conf
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Expand Up @@ -14,4 +14,4 @@ profile='solid_body_rotation_alt'
u0=40.0

[namelist:io]
diagnostic_frequency=120
diagnostic_frequency=60
2 changes: 1 addition & 1 deletion rose-stem/app/gungho_model/opt/rose-app-sbr_lam.conf
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Expand Up @@ -35,7 +35,7 @@ u0=40.
lbc_option='analytic'

[namelist:io]
diagnostic_frequency=24
diagnostic_frequency=12

[namelist:mixed_solver]
si_method='prec_only'
Expand Down
2 changes: 1 addition & 1 deletion rose-stem/app/gungho_model/opt/rose-app-schar3d_cart.conf
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Expand Up @@ -27,7 +27,7 @@ smp_init_wind=.true.
u0=10.0

[namelist:io]
diagnostic_frequency=2250
diagnostic_frequency=1125

[namelist:orography]
orog_init_option='analytic'
Expand Down
2 changes: 1 addition & 1 deletion rose-stem/app/gungho_model/opt/rose-app-schar_cart.conf
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Expand Up @@ -27,7 +27,7 @@ smp_init_wind=.true.
u0=10.0

[namelist:io]
diagnostic_frequency=900
diagnostic_frequency=450

[namelist:orography]
orog_init_option='analytic'
Expand Down
2 changes: 1 addition & 1 deletion rose-stem/app/gungho_model/opt/rose-app-schar_cart_8s.conf
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Expand Up @@ -27,7 +27,7 @@ smp_init_wind=.true.
u0=10.0

[namelist:io]
diagnostic_frequency=2250
diagnostic_frequency=1125

[namelist:orography]
orog_init_option='analytic'
Expand Down
2 changes: 1 addition & 1 deletion rose-stem/app/gungho_model/opt/rose-app-shallow-hot-jupiter.conf
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Expand Up @@ -17,7 +17,7 @@ test='isot_atm'
theta_surf=1800.0

[namelist:io]
diagnostic_frequency=240
diagnostic_frequency=120
write_conservation_diag=.true.

[namelist:mixed_solver]
Expand Down
2 changes: 1 addition & 1 deletion rose-stem/app/gungho_model/opt/rose-app-skamarock_klemp_gw_p0.conf
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Expand Up @@ -14,7 +14,7 @@ profile='constant_uv'
u0=20.0

[namelist:io]
diagnostic_frequency=100
diagnostic_frequency=50

[namelist:partitioning]
partitioner='planar'
Expand Down
2 changes: 1 addition & 1 deletion rose-stem/app/gungho_model/opt/rose-app-straka_100m.conf
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Expand Up @@ -14,7 +14,7 @@ rotating=.false.
test='cold_bubble_x'

[namelist:io]
diagnostic_frequency=900
diagnostic_frequency=450

[namelist:mixing]
viscosity=.true.
Expand Down
2 changes: 1 addition & 1 deletion rose-stem/app/gungho_model/opt/rose-app-straka_25m.conf
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Expand Up @@ -14,7 +14,7 @@ rotating=.false.
test='cold_bubble_x'

[namelist:io]
diagnostic_frequency=720
diagnostic_frequency=360

[namelist:mixing]
viscosity=.true.
Expand Down
2 changes: 1 addition & 1 deletion rose-stem/app/gungho_model/opt/rose-app-straka_50m.conf
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Expand Up @@ -14,7 +14,7 @@ rotating=.false.
test='cold_bubble_x'

[namelist:io]
diagnostic_frequency=360
diagnostic_frequency=180

[namelist:mixing]
viscosity=.true.
Expand Down
2 changes: 1 addition & 1 deletion rose-stem/app/gungho_model/opt/rose-app-tidally-locked-earth.conf
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Expand Up @@ -19,7 +19,7 @@ use_physics=.true.
test='isot_atm'

[namelist:io]
diagnostic_frequency=240
diagnostic_frequency=120

[namelist:physics]
limit_drag_incs=.false.
Expand Down
2 changes: 1 addition & 1 deletion rose-stem/app/gungho_model/opt/rose-app-warm3dbubble.conf
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Expand Up @@ -14,7 +14,7 @@ rotating=.false.
test='warm_bubble_3d'

[namelist:io]
diagnostic_frequency=80
diagnostic_frequency=40

[namelist:partitioning]
partitioner='planar'
Expand Down
10 changes: 9 additions & 1 deletion rose-stem/app/gungho_model/rose-app.conf
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Expand Up @@ -79,6 +79,7 @@ source=namelist:base_mesh
= namelist:time
= namelist:timestepping
= namelist:transport
= (namelist:tr_bdf2)
= (namelist:vapour_forcing)
= (namelist:vertadvect)
= (namelist:wind_forcing)
Expand Down Expand Up @@ -1302,7 +1303,7 @@ timestep_start='$RESTART_START'
alpha=0.55
dt=$DT
inner_iterations=2
method='semi_implicit'
method='tr_bdf2'
outer_iterations=2
runge_kutta_method='forward_euler'
spinup_alpha=.false.
Expand All @@ -1311,6 +1312,13 @@ tau_r=1.0
tau_t=1.0
tau_u=0.55

[namelist:tr_bdf2]
bdf2_inner_iterations=1,1
bdf2_outer_iterations=2
tr_inner_iterations_even=2,1
tr_inner_iterations_odd=1,1
tr_outer_iterations=2

[namelist:transport]
adjust_theta=.false.
!!adjust_theta_above=30000.0
Expand Down
2 changes: 1 addition & 1 deletion rose-stem/app/lfric_atm/opt/rose-app-C224_MG.conf
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Expand Up @@ -8,4 +8,4 @@ file_prefix='mesh_C224_MG'
!!fplane=

[namelist:radiation]
n_radstep=5
n_radstep=3
2 changes: 1 addition & 1 deletion rose-stem/app/lfric_atm/opt/rose-app-C896_MG.conf
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Expand Up @@ -29,4 +29,4 @@ orography_mesh_name='dynamics'
physics_mesh_name='dynamics'

[namelist:radiation]
n_radstep=15
n_radstep=6
2 changes: 1 addition & 1 deletion rose-stem/app/lfric_atm/opt/rose-app-ral3.conf
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Expand Up @@ -136,7 +136,7 @@ liu_bparam=-0.14
n_horiz_ang=16
n_horiz_layer=1
n_inc_radstep=5
n_radstep=15
n_radstep=5
scatter_method_lwinc='approx'
spectral_file_lwinc='spec/sp_lw_cloud9'
spectral_file_swinc='spec/sp_sw_cloud9'
Expand Down
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