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This table provides the values we've been using and explanation of what each quantity means.
ne30 v0/v1 | ne30v1 alternative (was this ever used?) | ne30 small dtime option | ne120 before 8/10/16 | ne120 after 8/10/16 | ne120 small dtime option | Explanation | |
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dtime | 30 min | 30min | 15min | 15 min | 15 min | 450s | 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_nsplit | 2 dt_remap=15m | 3 dt_remap=10m | 1 dt_remap=15m | 4 dt_remap=225s | 6* dt_remap=150 | 2 dt_remap=225s | 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=300s | 3 dt_tracer=75s | 2* dt_tracer=75s | 3 dt_tracer=75s | 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=300s1 | 1 | dt_dyn=300s1 | 1dt_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 | 3 dt_vis=100s | 4 dt_vis=18.75s | 4 | 4 | dtime/(se_nsplit_se_qsplit*se_rsplit*hypervis_subcycle) = timestep used for hyperviscosity calculation |
hypervis_subcycle_q | 1 | 1 | 1 | 1 | 1 | 1 | dtime/(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_steps | 6 | 6 | 3 | 3* | 3 | Number of times the code surrounding macrophysics + microphysics is subcycled. This means that dtime/cld_macmic_num_steps = timestep used for macrophysics and microphysics. | |
clubb_timestep | 300 sec | 300 sec | 300 sec | 300 sec | I'm not sure what this means or how it relates to cld_macmic_num_steps | ||
IRADSW | 2 steps | 1 hr | 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? | ||
IRADLW | 2 steps | 1 hr | 4 steps | 4 steps | How 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 |
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- Discussion of the need to use more frequent vertical remap at high horizontal resolution when 72 vertical layers are used: Re: 2016-08-11 Meeting notes - general Meeting
- Discussion of the need to use ftype=0 or 2 to avoid gravity wave shocks when coupling physics and dynamics: Fixing the conservation problem in the dynamical core
- Controlling time steps in the HOMME dycore: EAM's HOMME dycore