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EMOSLIB cannot handle interpolations from a regular latitude-longitude grid to a reduced gaussianGaussian, but MIR does not have that limitation. Interpolations from any global regular or reduced gaussian or latitude-longitude grids to regular or reduced gaussian or regular latitude longitude grids are now supported in MIR.
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Default truncation values for "RESOL=AUTO" (Automatic Truncation) have also changed. MIR uses a formula to truncate the spectral series to correspond to the equivalent linear Gaussian grid, replacing the fixed table used in EMOSLIB. Transformations to regular latitude-longitude grids then use an intermediate full (regular) Gaussian grid.
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| Path | Keywords | New keywords | MIR Behaviour | EMOSLIB Behaviour |
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| Red | RESOL=AUTO, GRID=1.0/1.0 | TRUNCATION=AUTO, INTGRID=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 |
| Green | RESOL=AV, GRID=1.0/1.0 | TRUNCATION=NONE, INTGRID=O1280, 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 | TRUNCATION=179, INTGRID=F90, 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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With EMOSLIB spectral fields are by default automatically truncated before interpolation to grid fields to reduce data volumes and spurious aliased values. When automatic truncation is applied MARS issues a warning message like INTFB: Resolution automatically set to .... The truncation can be controlled using the keywords truncation and intgrid. Users wanting to post-process at the full archived resolution can specify truncation = none in the request.
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When doing spectral to grid transformations, MIR may produce smoother fields compared to EMOSLIB. This is due to the fact that MIR uses the intermediate gaussian grid, while EMOSLIB does this transformation directly. |
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