Remove latitude flipping in Grid

parcels/field.py

@@ -691,8 +691,6 @@ def _reshape(self, data):
         # Ensure that field data is the right data type
         if not isinstance(data, (np.ndarray)):
             data = np.array(data)
-        if self.grid._lat_flipped:
-            data = np.flip(data, axis=-2)
 
         if self.grid.xdim == 1 or self.grid.ydim == 1:
             data = np.squeeze(data)  # First remove all length-1 dimensions in data, so that we can add them below

parcels/grid.py

@@ -1,13 +1,11 @@
 import functools
-import warnings
 from enum import IntEnum
 
 import numpy as np
 import numpy.typing as npt
 
 from parcels._typing import Mesh, UpdateStatus, assert_valid_mesh
 from parcels.tools.converters import TimeConverter
-from parcels.tools.warnings import FieldSetWarning
 
 __all__ = [
     "CurvilinearSGrid",
@@ -68,7 +66,6 @@ def __init__(
         assert_valid_mesh(mesh)
         self._mesh = mesh
         self._zonal_periodic = False
-        self._lat_flipped = False
         self._defer_load = False
         self._lonlat_minmax = np.array(
             [np.nanmin(lon), np.nanmax(lon), np.nanmin(lat), np.nanmax(lat)], dtype=np.float32
@@ -251,16 +248,6 @@ def __init__(self, lon, lat, time, time_origin, mesh: Mesh):
         super().__init__(lon, lat, time, time_origin, mesh)
         self.tdim = self.time.size
 
-        if self.ydim > 1 and self.lat[-1] < self.lat[0]:
-            self._lat = np.flip(self.lat, axis=0)
-            self._lat_flipped = True
-            warnings.warn(
-                "Flipping lat data from North-South to South-North. "
-                "Note that this may lead to wrong sign for meridional velocity, so tread very carefully",
-                FieldSetWarning,
-                stacklevel=2,
-            )
-
     @property
     def xdim(self):
         return self.lon.size
@@ -379,8 +366,6 @@ def __init__(
             ), "depth dimension has the wrong format. It should be [zdim, ydim, xdim]"
         if not self.depth.dtype == np.float32:
             self._depth = self.depth.astype(np.float32)
-        if self._lat_flipped:
-            self._depth = np.flip(self.depth, axis=-2)
 
     @property
     def zdim(self):

tests/test_fieldset_sampling.py

@@ -382,15 +382,11 @@ def test_partialslip_nearland_vertical(boundaryslip):
         assert np.allclose([p.lat for p in pset], 0.1)
 
 
-@pytest.mark.parametrize("lat_flip", [False, True])
-def test_fieldset_sample_particle(lat_flip):
+def test_fieldset_sample_particle():
     """Sample the fieldset using an array of particles."""
     npart = 120
     lon = np.linspace(-180, 180, 200, dtype=np.float32)
-    if lat_flip:
-        lat = np.linspace(90, -90, 100, dtype=np.float32)
-    else:
-        lat = np.linspace(-90, 90, 100, dtype=np.float32)
+    lat = np.linspace(-90, 90, 100, dtype=np.float32)
     V, U = np.meshgrid(lon, lat)
     data = {"U": U, "V": V}
     dimensions = {"lon": lon, "lat": lat}

tests/tools/test_warnings.py

@@ -17,16 +17,6 @@
 from tests.utils import TEST_DATA
 
 
-def test_fieldset_warning_latflipped():
-    # flipping lats warning
-    lat = [0, 1, 5, -5]
-    lon = [0, 1, 5, 10]
-    u = [[1, 1, 1, 1] for _ in range(4)]
-    v = [[1, 1, 1, 1] for _ in range(4)]
-    with pytest.warns(FieldSetWarning, match="Flipping lat data from North-South to South-North.*"):
-        FieldSet.from_data(data={"U": u, "V": v}, dimensions={"lon": lon, "lat": lat})
-
-
 def test_fieldset_warning_pop():
     filenames = str(TEST_DATA / "POPtestdata_time.nc")
     variables = {"U": "U", "V": "V", "W": "W", "T": "T"}