Remove coord discontinuity check in regrid (#2119)

Author: sloosvel

doc/recipe/preprocessor.rst

@@ -1015,13 +1015,6 @@ scheme available in :doc:`iris-esmf-regrid:index`:
           reference: esmf_regrid.schemes:regrid_rectilinear_to_rectilinear
           mdtol: 0.7
 
-Since version 0.6 of :doc:`iris-esmf-regrid:index`, the regridder is able
-to ignore discontinuities in the source grids if the data defined in the
-discontiguous points is masked.
-The :func:`~esmvalcore.preprocessor.regrid` preprocessor automatically detects
-if discontinuities are present, and configures the regridding scheme in order to take
-into account the mask of the source grid to ignore them.
-
 .. _ensemble statistics:
 
 Ensemble statistics

esmvalcore/preprocessor/_regrid.py

@@ -384,21 +384,6 @@ def extract_location(cube, location, scheme):
                          scheme)
 
 
-def _check_grid_discontiguities(cube, scheme):
-    """Check if there are grid discontiguities and set use_src_mask to True."""
-    scheme = dict(scheme)
-    try:
-        discontiguities = iris.util.find_discontiguities(cube)
-    except NotImplementedError:
-        pass
-    else:
-        if discontiguities.any():
-            scheme['use_src_mask'] = True
-            logger.debug('Grid discontinuities were found in the source grid. '
-                         'Setting scheme argument `use_src_mask` to True.')
-    return scheme
-
-
 def extract_point(cube, latitude, longitude, scheme):
     """Extract a point, with interpolation.
 
@@ -577,12 +562,6 @@ def regrid(cube, target_grid, scheme, lat_offset=True, lon_offset=True):
             scheme:
               reference: esmf_regrid.schemes:ESMFAreaWeighted
 
-    Since version 0.6 of :doc:`iris-esmf-regrid:index`, the regridder is able
-    to ignore discontinuities in the source grids if the data defined in the
-    discontiguous points is masked.
-    The preprocessor automatically detects if discontinuities are present,
-    and configures the regridding scheme in order to take into account
-    the mask of the source grid to ignore them.
     """
     if is_dataset(target_grid):
         target_grid = target_grid.copy()
@@ -637,8 +616,6 @@ def regrid(cube, target_grid, scheme, lat_offset=True, lon_offset=True):
             scheme['src_cube'] = cube
         if 'grid_cube' in scheme_args:
             scheme['grid_cube'] = target_grid
-        if 'use_src_mask' in scheme_args:
-            scheme = _check_grid_discontiguities(cube, scheme)
 
         loaded_scheme = obj(**scheme)
     else:

tests/unit/preprocessor/_regrid/test_regrid.py

@@ -1,7 +1,6 @@
 """Unit tests for the :func:`esmvalcore.preprocessor.regrid.regrid`
 function."""
 
-import logging
 import unittest
 from unittest import mock
 
@@ -16,7 +15,6 @@
 from esmvalcore.preprocessor._regrid import (
     _CACHE,
     HORIZONTAL_SCHEMES,
-    _check_grid_discontiguities,
     _horizontal_grid_is_close,
     _rechunk,
 )
@@ -269,62 +267,6 @@ def test_regrid_is_skipped_if_grids_are_the_same():
     assert expected_different_cube is not cube
 
 
-def test_no_discontiguities_in_coords():
-    """Test that no mask is used if there are no discontinuities in coords."""
-    cube = _make_cube(lat=LAT_SPEC1, lon=LON_SPEC1)
-    scheme = {}
-    scheme = _check_grid_discontiguities(cube, scheme)
-    assert scheme == {}
-
-
-def test_use_mask_if_discontiguities_in_coords(caplog):
-    """Test use_src_mask is added to the scheme."""
-    lat_bounds = np.array(
-        [[[-43.48076211, -34.01923789, -22.00961894, -31.47114317],
-          [-34.01923789, -10.0, 2.00961894, -22.00961894],
-          [-10.0, -0.53847577, 11.47114317, 2.00961894]],
-         [[-31.47114317, -22.00961894, -10.0, -19.46152423],
-          [-22.00961894, 2.00961894, 14.01923789, -10.0],
-          [2.00961894, 11.47114317, 23.48076211, 14.01923789]]])
-    lat_coord = iris.coords.AuxCoord(
-        [[-40.0, -20.0, 0.0], [-20.0, 0.0, 20.0]],
-        var_name='lat',
-        standard_name='latitude',
-        units='degrees_north',
-        bounds=lat_bounds,
-    )
-    lon_bounds = np.array([[[140.625, 99.375, 99.375, 140.625],
-                            [99.375, 140.625, 140.625, 99.375],
-                            [140.625, 99.375, 99.375, 140.625]],
-                           [[140., 99.375, 99.375, 140.],
-                            [99.375, 140.625, 140.625, 99.375],
-                            [140., 99.375, 99.375, 140.]]])
-    lon_coord = iris.coords.AuxCoord(
-        [[100.0, 140.0, 180.0], [80.0, 100.0, 120.0]],
-        var_name='lon',
-        standard_name='longitude',
-        units='degrees_east',
-        bounds=lon_bounds,
-    )
-    data = np.ma.array(
-        [[-40.0, -20.0, 0.0], [-20.0, 0.0, 20.0]],
-        mask=[[True, False, True], [False, True, False]],
-    )
-    cube = iris.cube.Cube(
-        data,
-        aux_coords_and_dims=[(lat_coord, (0, 1)), (lon_coord, (0, 1))],
-    )
-
-    scheme = {}
-    with caplog.at_level(logging.DEBUG):
-        scheme = _check_grid_discontiguities(cube, scheme)
-    assert scheme == {'use_src_mask': True}
-
-    msg = ('Grid discontinuities were found in the source grid. '
-           'Setting scheme argument `use_src_mask` to True.')
-    assert msg in caplog.text
-
-
 def make_test_cube(shape):
     data = da.empty(shape, dtype=np.float32)
     cube = iris.cube.Cube(data)