regrid

../../_images/REGRID.png

Takes data from a GRIB source and performs a variety of operations on it, including spectral to grid conversion, regridding using a large variety of powerful and flexible interpolation techniques, nabla operators and special consideration of wind fields. regrid() is designed with re-use in mind. The first time a particular interpolation is performed, it might take some time to compute, but it will create cache files that can be re-used, meaning that the same interpolation will be much faster on subsequent runs.

Tip

There is a in-depth introduction available on the use of various Regrid parameters.

Note

This function performs the same task as the Regrid icon in Metview’s user interface. It accepts its parameters as keyword arguments, described below.

regrid(**kwargs)

Performs a variety of operations on GRIB data, including spectral to grid conversion, regridding using a large variety of powerful and flexible interpolation techniques, nabla operators and special consideration of wind fields.

Parameters

  • source (str) –

  • data (Fieldset) –

  • grid_definition_mode ({"grid", "lambert_azimuthal_equal_area", "lambert_conformal", "template", "filter"}, default: "grid") –

  • template_source (str) – Specifies the path to the template data. When it is defined it takes precedence over template_data. Enabled when grid_definition_mode is “template”.

  • template_data (Fieldset) – Specifies the template data object. Enabled when grid_definition_mode is “template”.

  • grid (str or list[str]) –

  • first_point (number or list[number], default: [0, 0]) –

  • dx_in_metres (number) –

  • dy_in_metres (number) –

  • nx (number) –

  • ny (number) –

  • lad_in_degrees (number) –

  • lov_in_degrees (number) –

  • latin_1_in_degrees (number, default: 0) –

  • latin_2_in_degrees (number, default: 0) –

  • standard_parallel_in_degrees (number) –

  • central_longitude_in_degrees (number) –

  • wind_processing ({"off", "uv_to_uv", "vod_to_uv"}, default: "off") –

  • nabla (str, default: "off") –

  • nabla_poles_missing_values ({"on", "off"}, default: "off") – 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.

  • area (list[number], default: [-90, -180, 90, 180]) – Supply a grid definition as described here: area - keyword in MARS/Dissemination request (swapping north/south). Specifies the geographical area as [south, west, north, east] that the output fields will cover, the default being for the whole globe.

  • rotation (list[number], default: [-90, 0]) – Position of the South Pole (as [lat, lon]) of the intended rotated grid as lat/lon in degree, as described here: rotation - keyword in MARS/Dissemination request. This is applicable to regular lat/lon or regular/reduced Gaussian grids.

  • truncation (str, default: "automatic") –

  • intgrid (str, default: "automatic") –

  • frame (number) – Specifies the width of a frame within a given sub-area, as described here frame - keyword in MARS/Dissemination request. The width of the frame is specified as an (integer) number of grid points inwards from a given area.

  • interpolation (str, default: "automatic") –

    The possible values are as follows:

    • ”linear”

    • ”bilinear”

    • ”grid_box_average”

    • ”grid_box_statistics”

    • ”voronoi_statistics”

    • ”k_nearest_neighbours”

    • ”k_nearest_neighbours_statistics”

    • ”nearest_lsm”

    • ”nearest_neighbour”

    • ”structured_bicubic”

    • ”structured_bilinear”

    • ”structured_biquasicubic”

    • ”automatic”

  • interpolation_statistics (str, default: "automatic") –

    The possible values are as follows:

    • ”count”

    • ”count_above_upper_limit”

    • ”count_below_lower_limit”

    • ”maximum”

    • ”minimum”

    • ”mode_real”

    • ”mode_integral”

    • ”mode_boolean”

    • ”median_integral”

    • ”median_boolean”

    • ”mean”

    • ”variance”

    • ”skewness”

    • ”kurtosis”

    • ”stddev”

    • ”automatic”

  • nearest_method (str, default: "automatic") –

    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 \(\cap\) nclosest.

    • ”distance_or_nclosest”: input points respecting distance \(\cup\) 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

    • ”automatic”

  • distance_weighting (str, default: "inverse_distance_weighting_squared") –

  • nclosest (number, default: 4) –

  • distance (number, default: 1) –

  • climate_filter_delta (number, default: 1000) –

  • distance_weighting_gaussian_stddev (number, default: 1) –

  • distance_weighting_shepard_power (number, default: 2) –

  • distance_tolerance (number, default: 1) –

  • distance_weighting_with_lsm ({"nearest_lsm", "nearest_lsm_with_lowest_index", "off"}, default: "off") –

    Only available if interpolation is “nearest_lsm”. Possible values are:

    • ”nearest_lsm”: chose the closest input point (no disambiguation if there is more than one closest point at the same distance)

    • ”nearest_lsm_with_lowest_index”: cross-platform compatible version (of the above Nearest LSM) with disambiguation of closest input points at the same distance of output points

    • ”off”: use internal defaults (currently set to “nearest_lsm_with_lowest_index”)

  • lsm_weight_adjustment (number, default: 0.2) – Only available if 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 \(\sum_{i}w_{i}=1\).

  • lsm_interpolation_input (str, default: "nearest_neighbour") – If input is not on the same grid (geometry) as provided input LSM (respectively), interpolate with this method to a temporary LSM with required geometry.

  • lsm_selection_input ({"file", "named"}, default: "named") – Specifies whether input LSM file will come from lsm_named_input (“named”) or lsm_file_input (“file”).

  • lsm_named_input ({"1km", "10min", "o1280", "o640", "o320", "n320", "n256", "n128"}, default: "1km") –

    Select one of the predefined names from the following:

    • ”1km”: 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 (str) – Provide the path to an input LSM GRIB file.

  • lsm_value_threshold_input (number, default: 0.5) – For GRIB-based LSM (so excluding ‘1km’ and ‘10min’), the threshold for condition (value ≥ threshold) to distinguish land (true) from sea (false).

  • lsm_interpolation_output (str, default: "nearest_neighbour") – If output is not on the same grid (geometry) as provided output LSM (respectively), interpolate with this method to a temporary LSM with required geometry.

  • lsm_selection_output ({"file", "named"}, default: "named") – Specifies whether output LSM file will come from lsm_named_output (“named”) or lsm_file_output (“file”).

  • lsm_named_output ({"1km", "10min", "o1280", "o640", "o320", "n320", "n256", "n128"}, default: "1km") –

    Select one of the predefined names from the following:

    • ”1km”: 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_output (str) – Provide the path to an output LSM GRIB file.

  • lsm_value_threshold_output (number, default: 0.5) – For GRIB-based LSM (so excluding ‘1km’ and ‘10min’), the threshold for condition (value ≥ threshold) to distinguish land (true) from sea (false).

  • non_linear (str, default: "missing_if_heaviest_missing") –

  • simulated_missing_value (number, default: 9999) –

  • simulated_missing_value_epsilon (number, default: 0) –

  • accuracy (number) – Specifies the output GRIB bitsPerValue, as described here: accuracy - keyword in MARS/Dissemination request. If left empty, this will take the value from the input fields. This option can also be used to simply change the number of bits per value in a Fieldset if no other processing options are given. Note that if packing is set to “ieee”, then the only valid values for this parameter are 32 and 64.

  • packing ({"av", "co", "grid_jpeg", "so", "simple", "ieee", "as_input"}, default: "as_input") –

    Specifies the output GRIB packingType, as described here: accuracy - keyword in MARS/Dissemination request. Possible values are depending on build-time configuration.

  • basic_angle ({"decimal", "fraction", "as_input"}, default: "decimal") – Specifies how geographical values (e.g. bounding box and lat/lon increments) are encoded in the resulting GRIB file. Considering the numeric limits of GRIB encodings, some values are not correctly representable as decimal numbers (e.g. a longitude increment of one third of a degree, which has an infinitely repeating ‘3’). In these cases, it may be more accurate to encode these numbers as fractions, e.g. 1/3. If this option is set to ‘fraction’, this conversion is taken care of automatically when encoding the resulting GRIB, and you should still provide your output grid parameters as decimal numbers.

  • edition ({"1", "2", "as_input"}, default: "as_input") – Specifies the output GRIB edition (or format). Note that format conversion is not supported.

  • vector_space (str) –

    The possible values are as follows:

    • ”1d_angle_degree_asymmetric”

    • ”1d_angle_degree_symmetric”

    • ”1d_angle_radian_asymmetric”

    • ”1d_angle_radian_symmetric”

    • ”1d_linear”

    • ”1d_logarithmic”

  • target (str) – If specified, the resulting file will be written directly to that path and no temporary file will be generated.

Return type

Fieldset

Notebooks using metview.regrid

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Advanced regridding of data