Grid: supply a valid string or list of numbers in the Grid parameter (see below)
Lambert Conformal or Lambert Azimuthal Equal Area: supply details of the output grid in the set of Lambert grid definition parameters
Template: supply a template GRIB file, whose grid structure will be used to generate the output GRIB;
- Note 1: use either Template Source or Template Data to specify the template (not both)
.
- Note
that
- 2: only GRIB fields on regular lat/lon or regular/reduced Gaussian grids may currently be used as templates
.
Lambert Conformal: supply details of Filter: in this mode, the output grid in the set of Lambert grid definition parameters
Lambert Azimuthal Equal Area: supply details of the output grid in the set of Lambert grid definition parameters
Filter: in this mode, the output grid will be the same as the input grid, with k-nearest neighbours interpolation supporting the filtering

Grid Definition Mode: Grid

Grid

will be the same as the input grid, with interpolation acting as a filter
- Note 1: this is equivalent to Template, with the input serving as the template (same input format limitations apply)
- Note 2: Interpolation as k-nearest neighbours is the only method able to support filtering

Grid

Supply a grid definition as described here: grid - keyword in MARS/Dissemination request.

...

This parameter can be left empty to preserve the grid properties (regular/reduced lat/lon or Gaussian) while performing other kinds of post-processing (changing bits per value, calculation of gradients, etc.).

Template Source

If Grid Definition Mode

...

This mode configures regridding to output the same grid as the provided template, using one of the following parameters:

...

is Template, set path to a GRIB file to be used as template.

Template Data

...

If Grid Definition Mode
...
is Template, set a GRIB-based data object to be used as template.

Lambert Conformal or Lambert Azimuthal Equal Area parameters

These projections require setting several parameters, named following the convention in their descriptions:

...

Code Block

language	py

regrid_lambert_conformal = mv.regrid(
    grid_definition_mode = "lambert_conformal",
    first_point          = [50.88,-1.66],
    dx_in_metres         = 2500,
    dy_in_metres         = 2500,
    nx                   = 739,
    ny                   = 949,
    lad_in_degrees       = 63,
    lov_in_degrees       = 15,
    data                 = t_2m_rgg
    )

language

Code Block

py

regrid_lambert_azimuthallaea = mv.regrid(
    grid_definition_mode         = "lambert_azimuthal_equal_area",
    first_point                  = [5066.88982143,-135.66034024],
    dx_in_metres                 = 25005000,
    dy_in_metres                 = 25005000,
    nx                           = 7391000,
    ny                           = 949950,
    standard_parallel_in_degrees = 052,
    central_longitude_in_degrees = 010,
    data                         = t_2m_rgg
    )

Grid Definition Mode: Filter

This mode is similar to Template (see above), except the template is set to the input grid (the resulting output grid is the same as the input grid); In addition, interpolation k-nearest neighbours acts as a filter to the input values.

Wind processing

Wind Processing

Wind processing

...

Wind Processing

Activates processing that is particular to wind fields. Activates processing that is particular to wind fields. Winds are represented by its vector Cartesian components u/v (gridded) or U/V (spectral) and, typically, they are archived as (spectral) vorticity/divergence (vo/d.) The relation between the spectral and gridded wind components is u = U / cos(latitude) and v = V / cos(latitude).

It is up to the user to specify if the input consists of wind fields. Set this appropriatelly in order to perform the correct processing.

Possible options are:

U/V to u/v

...

Converts pairs of Cartesian components vector fields (spectral) U/V to (gridded) u/v. This option is required if regridding wind fields on/to a rotated grid.

Note: assumes that the input come in pairs of alternating U/V.

vo/d to u/v

...

Converts pairs of (spectral) vo/d

...

fields into (spectral) U/V or (gridded) u/v

...

Wind Processing: U/V to u/v

...

. In case of gridded output, scaling by the cosine of their latitudes is applied (as above.)

Note: assumes that the input come in pairs of alternating

...

vo/

...

d.
Off (default)	Each processed field is treated individually.

Spectral to grid inverse transform

...

If the input files are spectral, the following parameters are used to fine-tune the conversion to grid points. The general workflow is:

spectral data (input)
if Truncation is not None (default Automatic), spectral data is truncated (intermediate spectral field, controlled by Truncation)
if Intgrid is not None,
1. inverse transform produces an (intermediate gridded field, controlled by Intgrid),
2. interpolation to (final) grid
if Intgrid is None, inverse transform produces the (final) grid
Note: if the intended (final) grid is rotated, or a given projection (eg. Lambert Conformal, LAEA, etc.), is very expensive computationally
final gridded data (see Grid Definition Mode)

Wind Processing: vo/d to u/v

Converts pairs of vorticity and divergence fields into U/V (spectral) or u/v (gridded.) Assumes that the input come in pairs of alternating vo/d. The resulting values will be scaled by the cosine of their latitudes (as mentioned above).

Wind Processing: Off

No special processing is performed (default). It is assumed there are no wind fields in the input, each processed field is treated individually.

Spectral to grid inverse transform

If the input files are spectral, the following parameters are used to fine-tune the conversion to grid points.

Truncation

Spherical harmonics truncation, as described here: truncation - keyword in MARS/Dissemination request.

...

Available for any of the 'nearest' interpolation methods; Supports Interpolation K-Nearest Neighbours or Nearest LSM. Possible values are:

Distance	input points with radius (option Distance) of output point
Nclosest	n-closest input points (option Nclosest) to output point (default 4)
Distance and nclosest	input points respecting Distance ∩ Nclosest
Distance or nclosest	input points respecting Distance U Nclosest
Nclosest or nearest	n-closest input points (option Nclosest), if all are at the same distance (within option Distance Tolerance) return all points within that distance (robust interpolation of pole values)
Nearest neighbour with lowest index	nearest input point, if at the same distance to other points (option Nclosest) chosen by lowest index
Sample	Sample of n-closest points (option Nclosest) out of input points with radius (option Distance) of output point, not sorted by distance
Sorted sample	as above, sorted by distance

Associated options supporting Nearest Method (described above):

Distance: in [m] choice of closest points by disntace distance to input point
Nclosest: choice of n-closest input points to input point
Distance Tolerance: tolerance in [m] tolerance checking the farthes farthest from nearest points (when Nearest Method is Nclosest or nearest)
Nclosest: choice of n-closest input points to input point

Distance Weighting

Only available if Interpolation is K Nearest Neighbours. General way on how to interpolate input neighbouring point values to output points, including the Inverse Distance Weighting (IDW) class methods (see Wikipedia), which operates over input points returned by Nearest Method. Possible values are:

...

Most of the options avaiable concern modyfing the set of input points weights pertaining to a specific output point. When removing interpolation weights (pe. because they point to a missing value) all the remaining interpolation weights are re-normalised (linearly) to sum(w_i) = 1.

Possible values are:

Missing If All Missing	if all input point values (contributing to an output point) are missing, set output value to missing (it requires all input point values to be missing)
Missing If Any Missing	if any input point values (contributing to an output point) are missing, set output value to missing (it suffices one input missing value)
Missing If Heaviest Missing (default)	if the most significant point for interpolation (largest interpolation weight) is missing, set output value to missing

;
Typically

(

but

typically, not generally

)

, this corresponds to the nearest input point)
Simulated Missing Value^*	allows a user-specified value (option Simulated Missing Value) with a tolerance (option Simulated Missing Value Epsilon)
Heaviest	emulate Interpolation as Nearest Neighbour by selecting the most significant point for interpolation to each output point (discarding the other contributions)
No^*	no non-linear corrections are applied

* In the presence of missing values this can can create wrong results.

...

LSM Weight Adjustment

Only available if Distance Weighting With Lsm is not Off.

LSM Selection Input/Output

LSM is On, this is the factor adjusting input point weights if they are not of the same type (land/sea) as related output point; On application, all contributing input point weights are re-normalised (linearly) to sum(w_i) = 1.

LSM Selection Input/Output

Specifies whether the input/output LSM file Specifies whether the input/output LSM file will come from LSM Named Input/Output (named, default) or LSM File Input/Output (file).

...

Select one of the predefined names from the following list:

1km (default)

...

binary-based LSM sourced from MODIS Land Water Mask MOD44W (see reference)
10min	binary-based LSM at high resolution (legacy, pre-climate files version 15)
O1280	GRIB-based IFS supporting climate files version 15, on this specific grid
O640	(as above, for this grid)
O320	(as above, for this grid)
N320	(as above, for this grid)
N256	(as above, for this grid)
N128	(as above, for this grid)

LSM File Input/Output

Provide the path to an input/output LSM GRIB file.

LSM Interpolation Input/Output

If input/output is not on the same grid (geometry) as provided input/output LSM (respectively), interpolate with this method to a temporary LSM with required geometry.

LSM Value Threshold Input/Output

For GRIB-based LSM (so excluding

LSM File Input/Output

Provide the path to an input/output LSM GRIB file.

LSM Interpolation Input/Output

If input/output is not the same geometry (grid) as provided input/output LSM (respectively), interpolate with this method to a temporary LSM with required geometry.

LSM Value Threshold Input/Output

For GRIB-based LSM (this excludes '1km' and '10min'), the threshold for condition (value ≥ threshold) to distinguish land (true) from sea (false).

...

the threshold for condition (value ≥ threshold) to distinguish land (true) from sea (false).

Nabla differential operators

...

This options allows application of differential operators to input fields. The current available approach is similar as used in the Finite Volume Module of the IFS, specifically:

It employs an edge-based, median-dual finite-volume method, with field values interpreted as averaged quantities of the supporting "dual cells".

There is support for both scalar and vector (u/v) fields; Due to the geometrical interpretation being ill-posed at the poles (singularities) there is an additional option to force missing values at the poles.

Nabla

Activates a nabla (differential) operator processing on the fields. Possible functions options are:

Scalar Gradient

Scalar

...

field gradient (∇)
Scalar Laplacian	Scalar field Laplacian (∇²)
UV Gradient	Vector (u/v) field gradient (∇)
UV Divergence

...

Vector (u/v) field divergence (∇⋅)
UV Vorticity	Vector (u/v) field vorticity or curl (∇×)
Off (default)	no differential processing

Nabla Poles Missing Values

Due to the supporting differential operators calculation method, values aren't well defined at the poles (singularities); This option allows forcing missing value at the poles. Possible values are On and Off.

...

Space shortcuts

Page tree

Versions Compared

Old Version 50

New Version 51

Key

Grid Definition Mode: Grid

Grid

Grid

Template Source

Template Data

If Grid Definition Mode
...
is Template, set a GRIB-based data object to be used as template.

Lambert Conformal or Lambert Azimuthal Equal Area parameters

Grid Definition Mode: Filter

Wind processing

Wind Processing

Wind processing

Wind Processing

Wind Processing: U/V to u/v

Spectral to grid inverse transform

Wind Processing: vo/d to u/v

Wind Processing: Off

Spectral to grid inverse transform

Truncation

Distance Weighting

LSM Weight Adjustment

LSM Selection Input/Output

LSM Selection Input/Output

LSM File Input/Output

LSM Interpolation Input/Output

LSM Value Threshold Input/Output

LSM File Input/Output

LSM Interpolation Input/Output

LSM Value Threshold Input/Output

Nabla differential operators

Nabla

Nabla Poles Missing Values

Space shortcuts

Page tree

Page History

Versions Compared

Old Version 50

New Version 51

Key

Grid Definition Mode: Grid

Grid

Grid

Template Source

Template Data

If Grid Definition Mode... is Template, set a GRIB-based data object to be used as template.

Lambert Conformal or Lambert Azimuthal Equal Area parameters

Grid Definition Mode: Filter

Wind processing

Wind Processing

Wind processing

Wind Processing

Wind Processing: U/V to u/v

Spectral to grid inverse transform

Wind Processing: vo/d to u/v

Wind Processing: Off

Spectral to grid inverse transform

Truncation

Distance Weighting

LSM Weight Adjustment

LSM Selection Input/Output

LSM Selection Input/Output

LSM File Input/Output

LSM Interpolation Input/Output

LSM Value Threshold Input/Output

LSM File Input/Output

LSM Interpolation Input/Output

LSM Value Threshold Input/Output

Nabla differential operators

Nabla

Nabla Poles Missing Values

If Grid Definition Mode
...
is Template, set a GRIB-based data object to be used as template.