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| MIR Behaviour | EMOSLIB Behaviour | ||||||||||||||||
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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. | 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. |
| Note | ||
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When doing spectral to grid transformations, MIR may produce smoother Using the intermediate gausian grid can smooth the fields compared to EMOSLIB, which was going direct. This is due to the fact that MIR uses the intermediate gaussian grid, while EMOSLIB does this transformation directly. |
Usage of IFS spectral transform library
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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
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Winds on rotated grids
There are known issues with wind fields when working with rotated grids.
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In particular, wind speeds are correct but the direction is wrong
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due to a problem in computing the angles.
Performance for small subareas
When defining small subareas, MIR tends to be slower compared to EMOSLIB. At the moment, MIR does the interpolation on a global grid and performs the cropping operation later, whereas EMOSLIB will only interpolate on the subarea defined. This may be optimised in future versions.
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