xcdat.regridder.accessor.RegridderAccessor

class xcdat.regridder.accessor.RegridderAccessor(dataset)

An accessor class that provides regridding attributes and methods on xarray Datasets through the .regridder attribute.

Examples

Import RegridderAccessor class:

>>> import xcdat  # or from xcdat import regridder

Use RegridderAccessor class:

>>> ds = xcdat.open_dataset("/path/to/file")
>>>
>>> ds.regridder.<attribute>
>>> ds.regridder.<method>
>>> ds.regridder.<property>

Parameters:

dataset (xr.Dataset) – A Dataset object.

__init__(dataset)

Methods

__init__(dataset)
horizontal(data_var, output_grid[, tool])	Apply horizontal regridding to data_var of the current xr.Dataset to output_grid.
horizontal_regrid2(data_var, output_grid, ...)	Pure python implementation of CDAT's regrid2 horizontal regridder.
horizontal_xesmf(data_var, output_grid, ...)	Extends the xESMF library for horizontal regridding between structured rectilinear and curvilinear grids.

Attributes

grid	Returns xr.Dataset containing grid information.

_ds

property grid

Returns xr.Dataset containing grid information.

Returns:

xr.Dataset – With data variables describing the grid.

Raises:

• ValueError – If axis dimension coordinate variable is not correctly identified.

• ValueError – If axis has multiple dimensions (only one is expected).

_get_axis_data(name)

horizontal_xesmf(data_var, output_grid, **options)

Extends the xESMF library for horizontal regridding between structured rectilinear and curvilinear grids.

This method extends xESMF by automatically constructing the xe.XESMFRegridder object, preserving source bounds, and generating missing bounds. It regrids data_var in the dataset to output_grid.

Option documentation xcdat.regridder.xesmf.XESMFRegridder()

Parameters:

• data_var (str) – Name of the variable in the xr.Dataset to regrid.

• output_grid (xr.Dataset) – Dataset containing output grid.

• options (Dict[str, Any]) – Dictionary with extra parameters for the regridder.

Returns:

xr.Dataset – With the data_var variable on the grid defined in output_grid.

Raises:

ValueError – If tool is not supported.

Examples

Generate output grid:

>>> output_grid = xcdat.create_gaussian_grid(32)

Regrid data to output grid using xesmf:

>>> ds.regridder.horizontal_xesmf("ts", output_grid)

horizontal_regrid2(data_var, output_grid, **options)

Pure python implementation of CDAT’s regrid2 horizontal regridder.

Regrids data_var in dataset to output_grid using regrid2’s algorithm.

Options documentation xcdat.regridder.regrid2.Regrid2Regridder()

Parameters:

• data_var (str) – Name of the variable in the xr.Dataset to regrid.

• output_grid (xr.Dataset) – Dataset containing output grid.

• options (Dict[str, Any]) – Dictionary with extra parameters for the regridder.

Returns:

xr.Dataset – With the data_var variable on the grid defined in output_grid.

Raises:

ValueError – If tool is not supported.

Examples

Generate output grid:

>>> output_grid = xcdat.create_gaussian_grid(32)

Regrid data to output grid using regrid2:

>>> ds.regridder.horizontal_regrid2("ts", output_grid)

horizontal(data_var, output_grid, tool='xesmf', **options)

Apply horizontal regridding to data_var of the current xr.Dataset to output_grid.

When might Regrid2 be preferred over xESMF?

If performing conservative regridding from a high/medium resolution lat/lon grid to a coarse lat/lon target, Regrid2 may provide better results as it assumes grid cells with constant latitudes and longitudes while xESMF assumes the cells are connected by Great Circles [1].

Supported tools, methods and grids:

• xESMF (https://pangeo-xesmf.readthedocs.io/en/latest/)

  • Methods:

    • Bilinear

    • Conservative

    • Conservative Normed

    • Patch

    • Nearest s2d

    • Nearest d2s

  • Grids:

    • Rectilinear

    • Curvilinear

  • Find options at xcdat.regridder.xesmf.XESMFRegridder()

• Regrid2

  • Methods:

    • Conservative

  • Grids:

    • Rectilinear

  • Find options at xcdat.regridder.regrid2.Regrid2Regridder()

Parameters:

• data_var (str) – Name of the variable in the xr.Dataset to regrid.

• output_grid (xr.Dataset) – Dataset containing output grid.

• tool (str) – Name of the regridding tool.

• **options (Dict[str, Any]) – These options are passed to the tool being used for regridding. See specific regridder documentation for available options.

Returns:

xr.Dataset – With the data_var variable on the grid defined in output_grid.

Raises:

ValueError – If tool is not supported.

References

[1]

https://earthsystemmodeling.org/docs/release/ESMF_8_1_0/ESMF_refdoc/node5.html#SECTION05012900000000000000

Examples

Create destination grid:

>>> output_grid = xcdat.create_uniform_grid(-90, 90, 4.0, -180, 180, 5.0)

Regrid variable using “xesmf”:

>>> ds.regridder.horizontal("ts", output_grid, tool="xesmf", method="bilinear")

Regrid variable using “regrid2”:

>>> ds.regridder.horizontal("ts", output_grid, tool="regrid2")

Use convenience methods:

>>> ds.regridder.horizontal_xesmf("ts", output_grid, method="bilinear")

>>> ds.regridder.horizontal_regrid2("ts", output_grid)