Add regridding option to fileio

unseen/fileio.py

@@ -27,6 +27,8 @@ def open_dataset(
     chunks=None,
     metadata_file=None,
     variables=[],
+    regrid_name=None,
+    regrid_method="conservative",
     point_selection=None,
     lat_bnds=None,
     lon_bnds=None,
@@ -72,6 +74,12 @@ def open_dataset(
         YAML file path specifying required file metadata changes
     variables : list, optional
         Subset of variables of interest
+    regrid_name : str, optional
+        Name of grid for sptial regridding in AUSXXXi format.
+        e.g. AUS005i is a 0.05 x 0.05 lat/lon grid
+        e.g. AUS300i is a 3.00 x 3.00 lat/lon grid
+    regrid_method : {"conservative", "bilinear", "nearest_s2d", "nearest_d2s"}, default "conservative"
+        Name of grid for sptial regridding in AUSXXXi format.
     point_selection : list, optional
         Point coordinates: [lat, lon]
     lat_bnds : list, optional
@@ -182,6 +190,11 @@ def open_dataset(
         for var, target_units in units.items():
             ds[var] = general_utils.convert_units(ds[var], target_units)
 
+    # Spatial regridding
+    if regrid_name:
+        new_grid = general_utils.create_grid(regrid_name)
+        ds = general_utils.regrid(ds, new_grid, method=regrid_method)
+
     # Spatial subsetting and aggregation
     if point_selection:
         ds = spatial_selection.select_point(
@@ -709,6 +722,19 @@ def _parse_command_line():
         choices=["month"],
         help="Anomaly can monthly (month) or all times (none)",
     )
+    parser.add_argument(
+        "--regrid_name",
+        type=str,
+        default=None,
+        help="Name of grid for sptial regridding in AUSXXXi format",
+    )
+    parser.add_argument(
+        "--regrid_method",
+        type=str,
+        default="conservative",
+        choices=["conservative", "bilinear", "nearest_s2d", "nearest_d2s"],
+        help="Regridding method",
+    )
     parser.add_argument(
         "--point_selection",
         type=float,
@@ -855,6 +881,8 @@ def _main():
         "chunks": args.input_chunks,
         "metadata_file": args.metadata_file,
         "variables": args.variables,
+        "regrid_name": args.regrid_name,
+        "regrid_method": args.regrid_method,
         "point_selection": args.point_selection,
         "lat_bnds": args.lat_bnds,
         "lon_bnds": args.lon_bnds,

unseen/general_utils.py

@@ -4,6 +4,7 @@
 from matplotlib.ticker import AutoMinorLocator
 import matplotlib.pyplot as plt
 import numpy as np
+import xarray as xr
 from xarray import Dataset
 from xclim.core import units
 from xesmf import Regridder
@@ -76,6 +77,67 @@ def convert_units(da, target_units):
     return da
 
 
+def create_grid(grid_name):
+    """Create a regular lat/lon grid.
+
+    Parameters
+    ----------
+    grid_name : str
+        Name of the grid.
+
+    Returns
+    -------
+    ds_grid : xarray.Dataset
+        Dataset with desired lat/lon axes.
+
+    Notes
+    -----
+    The only valid grids are in the AUSXXi format. e.g:
+      - AUS005i is a 0.05 x 0.05 grid across Australia.
+      - AUS050i is a 0.50 x 0.50 grid across Australia.
+      - AUS300i is a 3.00 x 3.00 grid across Australia.
+    """
+
+    assert len(grid_name) == 7, "grid_name must be AUSXXXi format"
+    assert grid_name[0:3] == "AUS", "AUSXXXi grids only"
+    # AGCD bounds
+    south_lat = -44.5
+    north_lat = -10
+    west_lon = 112
+    east_lon = 156.25
+
+    step_start = grid_name[3]
+    step_end = grid_name[4:6]
+    step = float(f"{step_start}.{step_end}")
+
+    ds_grid = xr.Dataset(
+        {
+            "lat": (
+                ["lat"],
+                np.round(np.arange(south_lat, north_lat + step, step), decimals=2),
+            ),
+            "lon": (
+                ["lon"],
+                np.round(np.arange(west_lon, east_lon + step, step), decimals=2),
+            ),
+        }
+    )
+    ds_grid["lat"].attrs = {
+        "standard_name": "latitude",
+        "long_name": "latitude",
+        "units": "degrees_north",
+        "axis": "Y",
+    }
+    ds_grid["lon"].attrs = {
+        "standard_name": "longitude",
+        "long_name": "longitude",
+        "units": "degrees_east",
+        "axis": "X",
+    }
+
+    return ds_grid
+
+
 def regrid(ds, ds_grid, method="conservative", **kwargs):
     """Regrid `ds` to the grid of `ds_grid` using xESMF.