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| Value | RESOL equivalent | Description | ||
|---|---|---|---|---|
| NONE | - | Disables the use of an intermediate grid
| ||
| AUTO | - | An intermediate FULL Gaussian grid is used, derived from the output GRID, by looking at the equivalent resolution. This is the default behaviour | ||
Onumber | Onumber | Use the specified Octahedral Gaussian grid as an intermediate grid | ||
| Fnumber | Fnumber | Use the specified Full (regular) Gaussian grid as an intermediate grid | ||
| Nnumber | Nnumber | Use the specified Reduced Gaussian grid as an intermediate grid | ||
| OFF | OFF | reserved MARS value that resets the value inherited, effectively removing the keyword from the request. In this case results in AUTO being applied. |
Different treatment for RESOL=AV
The concept of "RESOL=AV" ("Archived Value") when going to a lower resolution is different. With MIR, RESOL=AV specifies that the transformation is made first to the corresponding octahedral reduced Gaussian grid (i.e., T1279 → O1280 or T639 → O640) followed by grid point interpolation to the user-specified grid.
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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This diagram illustrates an example transformation going from T1279 to a regular lat-lon 1.0/1.0 grid. Depending on the values of RESOL and GRID, MIR will follow different paths. As a reference, the original EMOSLIB behaviour is also shown for each case:
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