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Comment: Corrected INTGRID value corresponding to RESOL=AV

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ValueRESOL equivalentDescription
NONE-

Disables the use of an intermediate grid

Warning

Use of INTGRID=NONE in combination with the ROTATION keyword is very expensive in resources and is not recommended.


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

OnumberUse the specified Octahedral Gaussian grid as an intermediate grid
FnumberFnumberUse the specified Full (regular) Gaussian grid as an intermediate grid
NnumberNnumberUse the specified Reduced Gaussian grid as an intermediate grid
OFFOFFreserved 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:

MIR BehaviourEMOSLIB Behaviour
Gliffy Diagram
chromemin
namespectral-to-grid
pagePin10

 


Gliffy Diagram
chromemin
namespectral-to-grid-EMOSLIB
pagePin3

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PathKeywordsNew keywordsMIR BehaviourEMOSLIB Behaviour
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=AUTOO1280,

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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