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The new MARS client with the MIR interpolation library is currently in BETA, and it is meant for tests only. Do not use it for any operational purpose. You can try the new MIR-enabled MARS client on any ECMWF computing platform with:
You are encouraged to test this new version of the MARS client and report any issues to advisory@ecmwf.int . Testing MARS/MIR through the ECMWF WebAPI will also be possible soon.If you are using the the ECMWF WebAPI you can test it by adding an extra keyword to your requests:
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MIR stands for Meteorological Interpolation and Regridding and is a library of routines for interpolation and regridding of meteorological fields. This new piece of software is replacing the veteran EMOSLIB when it comes to perform those operations in MARS. Beyond this, MIR’s flexible design facilitates scalability improvements and additional features. These include efficiency gains, a high degree of user configurability, and support for a wider range of grids than in the current package. See the related article in the ECMWF newsletter no.152 for a more complete description of this new library.
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By default, MIR does not use land-sea mask processing for any parameters. However, users will be able to specify the land-sea mask to use LSM processing for both input and output grids with a new set of MARS keywords.the new LSM keyword:
| No Format |
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LSM=ON |
To disable for subsequent requests, once it is enabled:
| No Format |
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LSM=OFF |
| Info |
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| Info |
Note that as a consequence, MIR does not apply land-sea mask processing when using the nearest neighbour method, which was the case in EMOSLIB. |
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Spectral to grid point transformations
New keywords to control truncation and intermediate grids
Two new MARS keywords, TRUNCATION and INTGRID, are introduced which superseed the RESOL keyword. RESOL is still supported, but will eventually considered deprecated.
TRUNCATION
Describes how to treat the incoming SH, before the transformation is passed to TRANS library.
| Value | RESOL equivalent | Description |
|---|---|---|
| NONE | AV | Disables any truncation before the transformation |
| AUTO | AUTO | Truncation is derived from the intermediate grid. This is the default behaviour |
number | number | Specific truncation to be applied, e.g. TRUNCATION=179 truncates input SH field to T179 |
| 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. |
INTGRID
Describes the intermediate grid to which the transform is performed. It may be coincident with the target grid, in which case there isn't a second interpolation and the transform is direct to target grid.
| 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
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.
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| MIR Behaviour | EMOSLIB Behaviour | ||||||||||||||||
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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 to EMOSLIB's truncation table |
| Green | RESOL=AV, GRID=1.0/1.0 | TRUNCATION=NONE, INTGRID=AUTO, 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 | 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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