Versions Compared

Key

  • This line was added.
  • This line was removed.
  • Formatting was changed.

There are lots of different timesteps and substepping going on in the ACME v1 model (much of which is inherited from v0). This page is an attempt to clarify what values we typically use for these substeps. Note that most of the substep values for dynamics are illustrated in this slide:


This table provides the values we've been using and explanation of what each quantity means.


ne30

v0

ne30

v1

ne120 before 8/10/16ne120 after 8/10/16Explanation
dtime30 min30min15 min15 min

Timestep used for most physics processes and for coupling between physics and dynamics

For se_ftype=1, physics tendencies are applied as a hard adjustment every dtime seconds.

se_nsplit2 dt_remap=15m

3

dt_remap=10m

4

dt_remap=225s

6*

dtime/se_nsplit = time between vertical remaps of the semi-Lagrangian vertical coordinate.

For se_ftype=0, physics tendencies are "dribbled" into the dynamics every dt_remap seconds.

se_rsplit

3

dt_tracer=300s

2

dt_tracer=300s

3

dt_tracer=75s

2*

dtime/(se_nsplit*se_rsplit) = timestep used for tracer timestep

For ne30, dt_tracers = 360s is probably stable, but we usually use 300s

For ne120, dt_tracers = 90s is probably stable, but we usually use 75s.

se_qsplit

1

dt_dyn=300s

1

dt_dyn=300s

1

dt_dyn=75s

1

dtime/(se_nsplit*se_qsplit*se_rsplit) = timestep used for dynamics calculations

This should always be 1, so that dt_dyn = dt_tracers.

hypervis_subcycle

3

dt_vis = 100s

3

dt_vis=100s

4

dt_vis=18.75s

4dtime/(se_nsplit_se_qsplit*se_rsplit*hypervis_subcycle) = timestep used for hyperviscosity calculation
hypervis_subcycle_q1111dtime/(se_nsplit_se_qsplit*se_rsplit*hypervis_subcycle_q) = timestep used for hyperviscosity calculation in tracer advection (namelist_definition.xml indicates that only '1' is supported in CAM?)
cld_macmic_num_steps663*3Number of times the code surrounding macrophysics + microphysics is subcycled. This means that dtime/cld_macmic_num_steps = timestep used for macrophysics and microphysics.
clubb_timestep300 sec
300 sec300 secI'm not sure what this means or how it relates to cld_macmic_num_steps
IRADSW2 steps
4 steps (1 hr)4 steps (1 hr)How frequently to compute SW radiation (in multiples of dtime). Radiation tendencies are taken from previous steps for steps when radiation is not recalculated. I think some scaling is made to account for zenith angle changes?
IRADLW2 steps
4 steps4 stepsHow frequently to compute LW radiation (in multiples of dtime). Radiation tendencies are taken from previous steps for steps when radiation is not recalculated. 



*since AV1C-04*suggest to use