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We propose to apply the elevation class scheme to the ACME model in two stages. The first three stages. In the first stage, targeting ACME V2.0, elevation classes are added to the land model but not the atmosphere model. Land forcing fields (temperature, precipitation, downward longwave) from the atmosphere are lapsed with surface elevation at prescribed rates. Adjustments to ensure conservation of the grid cell mean are applied. Fluxes returned from land to atmosphere are aggregated to form grid cell mean. No changes in the coupler or atmosphere are needed.
The second stage, targeting ACME V3.0, will assume the atmosphere and land models operate on the same grid and adopt the same elevation classification algorithm. This results in a one-to-one mapping between elevation classes in the land and atmosphere, so that no interpolation is required to couple the land and atmosphere for each elevation class. Although we expect this configuration to yield spectacular results, it does not allow the land model to distinguish subgrid watersheds.
In stage twothree, targeting ACME V4.0, the land model will represent watersheds, so that interpolation will be required to couple elevation classes in the land and atmosphere. Conservation will require normalizing fields to preserve grid cell means.
There are numerous challenges with implementing elevation classes in ACME that did not exist in the first implementations in MM5 and CAM3, mostly because a coupler was not used to couple the atmosphere and land in MM5 or CAM3.
A design document that identifies the challenges, describes methods to address them, and specifies tests to determine whether the scheme is working properly in the ACME model, has been prepared. While some of the work has been done as March 2017, staffing limitations have been a bottleneck and need to be resolved. Completing development for each stage will require involvement of ACME staff from the land, atmosphere, and coupling teams.
An estimate of staffing for completing stage one is listed in the tableis listed below.
| name | group | tasks | person-months |
|---|---|---|---|
| Peter Thornton | land | ||
| Teklu Tesfa | land | ||
| Ruby Leung | land |
An estimate of staffing for completing stage two is listed below.
| name | group | tasks | person-months |
|---|---|---|---|
| Steve Ghan | atmosphere | lead and manage activity, develop post-processor | 3 |
| Steve Goldhaber | software | ||
| Peter Thornton | land | ||
| Teklu Tesfa | land | ||
| Rob Jacob | coupler | ||
| Ruby Leung | land |
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