Add Lambert Conformal Conic (LCC) Grid Utility

src/xregrid/utils.py

@@ -778,6 +778,62 @@ def create_grid_from_ioapi(
     return ds
 
 
+def create_lcc_grid(
+    extent: Tuple[float, float, float, float],
+    res: Union[float, Tuple[float, float]],
+    lat_1: float,
+    lat_2: float,
+    lat_0: float,
+    lon_0: float,
+    add_bounds: bool = True,
+    chunks: Optional[Union[int, Dict[str, int]]] = None,
+) -> xr.Dataset:
+    """
+    Create a structured grid dataset with a Lambert Conformal Conic (LCC) projection.
+
+    Commonly used for regional meteorological models (e.g., HRRR, NAM, CORDEX).
+
+    Parameters
+    ----------
+    extent : Tuple[float, float, float, float]
+        Grid extent in projection units (meters): (min_x, max_x, min_y, max_y).
+    res : float or Tuple[float, float]
+        Grid resolution in meters. If float, same resolution in x and y.
+    lat_1 : float
+        First standard parallel.
+    lat_2 : float
+        Second standard parallel.
+    lat_0 : float
+        Latitude of projection origin.
+    lon_0 : float
+        Longitude of projection origin (central meridian).
+    add_bounds : bool, default True
+        Whether to add cell boundary coordinates.
+    chunks : int or Dict[str, int], optional
+        Chunk sizes for the resulting dask-backed dataset.
+
+    Returns
+    -------
+    xr.Dataset
+        The grid dataset containing 'lat', 'lon' and projected coordinates 'x', 'y'.
+    """
+    crs = (
+        f"+proj=lcc +lat_1={lat_1} +lat_2={lat_2} +lat_0={lat_0} "
+        f"+lon_0={lon_0} +x_0=0 +y_0=0 +datum=WGS84 +units=m +no_defs"
+    )
+    ds = create_grid_from_crs(crs, extent, res, add_bounds=add_bounds, chunks=chunks)
+
+    # Backend detection for provenance
+    is_lazy = chunks is not None
+    backend = "Lazy" if is_lazy else "Eager"
+
+    update_history(
+        ds,
+        f"Created Lambert Conformal Conic grid (lat_1={lat_1}, lat_2={lat_2}, lat_0={lat_0}, lon_0={lon_0}) using xregrid ({backend}).",
+    )
+    return ds
+
+
 def create_sinusoidal_grid(
     extent: Tuple[float, float, float, float],
     res: Union[float, Tuple[float, float], str],

tests/test_aero_grid_lcc.py

@@ -0,0 +1,78 @@
+import xarray as xr
+import pytest
+from xregrid.utils import create_lcc_grid
+
+
+def test_lcc_grid_backend_consistency():
+    """Verify that LCC grid generation yields identical results for NumPy and Dask."""
+    pytest.importorskip("pyproj")
+
+    # Define a small LCC grid
+    extent = (-100000, 100000, -100000, 100000)
+    res = 20000
+    lat_1, lat_2 = 33, 45
+    lat_0, lon_0 = 40, -97
+
+    ds_eager = create_lcc_grid(
+        extent=extent,
+        res=res,
+        lat_1=lat_1,
+        lat_2=lat_2,
+        lat_0=lat_0,
+        lon_0=lon_0,
+        chunks=None,
+    )
+
+    ds_lazy = create_lcc_grid(
+        extent=extent,
+        res=res,
+        lat_1=lat_1,
+        lat_2=lat_2,
+        lat_0=lat_0,
+        lon_0=lon_0,
+        chunks={"x": 5, "y": 5},
+    )
+
+    # 1. Numerical Consistency
+    xr.testing.assert_allclose(ds_eager, ds_lazy.compute())
+
+    # 2. Laziness Check
+    # In xarray, dimension coordinates are eager.
+    # Non-dimension coordinates and DataArrays should be lazy.
+    assert hasattr(ds_lazy.lat.data, "dask")
+    assert hasattr(ds_lazy.lon.data, "dask")
+    assert hasattr(ds_lazy.lat_b.data, "dask")
+    assert hasattr(ds_lazy.lon_b.data, "dask")
+
+    # 3. Metadata and CF-compliance
+    assert "lat" in ds_eager.coords
+    assert "lon" in ds_eager.coords
+    assert ds_eager.lat.attrs["standard_name"] == "latitude"
+    assert ds_eager.lon.attrs["standard_name"] == "longitude"
+    assert "crs" in ds_eager.attrs
+    assert "Lambert Conic Conformal" in ds_eager.attrs["crs"]
+
+    # 4. Provenance
+    assert "history" in ds_eager.attrs
+    assert "Created Lambert Conformal Conic grid" in ds_eager.attrs["history"]
+    assert "(Eager)" in ds_eager.attrs["history"]
+    assert "(Lazy)" in ds_lazy.attrs["history"]
+
+
+def test_lcc_grid_resolution_tuple():
+    """Verify LCC grid works with a tuple for resolution."""
+    pytest.importorskip("pyproj")
+    extent = (-10000, 10000, -10000, 10000)
+    res = (1000, 2000)
+
+    ds = create_lcc_grid(
+        extent=extent,
+        res=res,
+        lat_1=30,
+        lat_2=60,
+        lat_0=45,
+        lon_0=-100,
+    )
+
+    assert ds.x.size == 20  # 20000 / 1000
+    assert ds.y.size == 10  # 20000 / 2000