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| Path | Keywords | MIR Behaviour | EMOSLIB Behaviour |
|---|---|---|---|
| Red | RESOL=AUTO, GRID=1.0/1.0 | Default Behaviour. Transformation from T1279 to an intermediate F90 full (regular) Gaussian grid (with an automatic truncation to T179) followed by a grid-to-grid interpolation from the F90 grid to 1.0/1.0. | Default Behaviour. Direct transformation from T1279 to 1.0/1.0, with an automatic truncation to T213 according to EMOSLIB's truncation table |
| Green | RESOL=AV, GRID=1.0/1.0 | Transformation from T1279 to the corresponding intermediate reduced octahedral Gaussian O1280, before going to 1.0/1.0. See Known issues | Direct transformation from T1279 to 1.0/1.0, with no truncation. |
| Blue | RESOL=179, GRID=F90, and then GRID=1.0/1.0 | Transformation from T1279 to the F90 full (regular) Gaussian grid (with a user-specified truncation to T179) followed by a grid-to-grid interpolation from the F90 grid to 1.0/1.0. | Same as in MIR, but a separate MARS request is needed for each of the two steps. |
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MIR does not support the 12-point interpolation method, used by EMOSLIB for rotated grids. Therefore, the default interpolation method used is the linear. Rotated spherical harmonics are not supported in MIR or EMOSLIB.
Known Issues
RESOL=AV uses wrong intermediate Gaussian grid
When using RESOL=AV and transforming from spectral to grid, the corresponding intermediate Gaussian grid to be used should be the cubic reduced Gaussian grid by default (i.e., O = T+1), as described above. However, at this point MIR uses a full (regular) gaussian grid with linear truncation (i.e., F = (T+1)/2).
Winds on rotated grids
There are known issues with wind fields when working with rotated grids. In particular, wind speeds are correct but the direction is wrong due to a problem in computing the angles.
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