esmf_regrid.esmf_regridder module#

Provides ESMF representations of grids/UGRID meshes and a modified regridder.

class esmf_regrid.esmf_regridder.GridInfo(lons, lats, lonbounds, latbounds, crs=None, circular=False, areas=None, center=False)[source]#

Bases: SDO

Class for handling structured grids.

This class holds information about lat-lon type grids. That is, grids defined by lists of latitude and longitude values for points/bounds (with respect to some coordinate reference system i.e. rotated pole). It contains methods for translating this information into ESMF objects. In particular, there are methods for representing as a ESMF.api.grid.Grid and as a ESMF.api.field.Field containing that Grid. This ESMF Field is designed to contain enough information for area weighted regridding and may be inappropriate for other ESMF regridding schemes.

Create a GridInfo object describing the grid.

Parameters

  • lons (ArrayLike) – A 1D or 2D array or list describing the longitudes of the grid points.

  • lats (ArrayLike) – A 1D or 2D array or list describing the latitudes of the grid points.

  • lonbounds (ArrayLike) – A 1D or 2D array or list describing the longitude bounds of the grid. Should have length one greater than lons.

  • latbounds (ArrayLike) – A 1D or 2D array or list describing the latitude bounds of the grid. Should have length one greater than lats.

  • crs (cartopy.crs.CRS, optional) – Describes how to interpret the above arguments. If None, defaults to Geodetic.

  • circular (bool, default=False) – Describes if the final longitude bounds should be considered contiguous with the first.

  • areas (ArrayLike, optional) – Array describing the areas associated with each face. If None, then ESMF will use its own calculated areas.

  • center (bool, default=False) – Describes if the center points of the grid cells are used in regridding calculations.

class esmf_regrid.esmf_regridder.Regridder(src, tgt, method='conservative', precomputed_weights=None)[source]#

Bases: object

Regridder for directly interfacing with ESMF.

Create a regridder from descriptions of horizontal grids/meshes.

Weights will be calculated using ESMF and stored as a scipy.sparse.csr_matrix for use in regridding. If precomputed weights are provided, these will be used instead of calculating via ESMF.

Parameters

  • src (MeshInfo or GridInfo) – Describes the source mesh/grid. Data supplied to this regridder should be in a numpy.ndarray whose shape is compatible with src.

  • tgt (MeshInfo or GridInfo) – Describes the target mesh/grid. Data output by this regridder will be a numpy.ndarray whose shape is compatible with tgt.

  • method (str) – Either “conservative” or “bilinear”. Corresponds to the ESMF methods CONSERVE or BILINEAR used to calculate weights.

  • precomputed_weights (scipy.sparse.spmatrix, optional) – If None, ESMF will be used to calculate regridding weights. Otherwise, ESMF will be bypassed and precomputed_weights will be used as the regridding weights.

regrid(src_array, norm_type='fracarea', mdtol=1)[source]#

Perform regridding on an array of data.

Parameters

  • src_array (ArrayLike) – Array whose shape is compatible with self.src

  • norm_type (str) – Either fracarea or dstarea, defaults to fracarea. Determines the type of normalisation applied to the weights. Normalisations correspond to ESMF constants FRACAREA and DSTAREA.

  • mdtol (float, default=1) – A number between 0 and 1 describing the missing data tolerance. Depending on the value of mdtol, if a cell in the target grid is not sufficiently covered by unmasked cells of the source grid, then it will be masked. mdtol=1 means that only target cells which are not covered at all will be masked, mdtol=0 means that all target cells that are not entirely covered will be masked, and mdtol=0.5 means that all target cells that are less than half covered will be masked.

Returns

An array whose shape is compatible with self.tgt.

Return type

ArrayLike