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 awesome figure by Kate Evans (Unlicensed) demonstrates the timesteps used for each level of substepping in the SE dycore:
| Here's a simpler/less complete version from Peter Caldwell:
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- se_ftype=0 (default): the physics tendency is included as a constant source term in each remap timestep
- se_ftype=1: the impact of physics is applied entirely before dynamics is run. In other words, dynamics sees the state after physics. This prevents conservation errors but pushes the model state too far away from where dynamics wants it, resulting in a shock and resulting gravity wave propagation every time dynamics is called.
- se_ftype=2: A blend of ftype=0 and ftype=1... The model state is updated to include the effect of physics on temperature and winds before dynamics is called, but the effect of other quantities is dribbled into dynamics every remap substep.
Discussions/Links Relevant to This Page:
- 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