adding unit and name attributes to layers

src/openmethane_prior/outputs.py

@@ -27,7 +27,10 @@
 from openmethane_prior.layers import layer_names
 from openmethane_prior.utils import SECS_PER_YEAR
 
-coordNames = ["TSTEP", "LAY", "ROW", "COL"]
+COORD_NAMES = ["TSTEP", "LAY", "ROW", "COL"]
+REQUIRED_ATTRIBUTES = {"units": "kg/m^2/s"}
+TOTAL_LAYER_NAME = "OCH4_TOTAL"
+TOTAL_LAYER_LONG_NAME = "total methane flux"
 
 
 def convert_to_timescale(emission, cell_area):
@@ -75,7 +78,11 @@ def write_layer(
         # coerce to four dimensions if it's not
         for i in range(layer_data.ndim, 4):
             copy = np.expand_dims(copy, 0)  # should now have four dimensions
-        ds[layer_name] = (coordNames[:], copy)
+        ds[layer_name] = (COORD_NAMES[:], copy)
+
+    for k, v in REQUIRED_ATTRIBUTES.items():
+        ds[layer_name].attrs[k] = v
+    ds[layer_name].attrs["long_name"] = layer_name
 
     output_path.parent.mkdir(parents=True, exist_ok=True)
     ds.to_netcdf(output_path)
@@ -112,5 +119,8 @@ def sum_layers(output_path: pathlib.Path):
             summed += ds[layerName].values  # it will broadcast time dimensions of 1 correctly
 
     if summed is not None:
-        ds["OCH4_TOTAL"] = (["date", "LAY", *coordNames[-2:]], summed)
+        ds[TOTAL_LAYER_NAME] = (["date", "LAY", *COORD_NAMES[-2:]], summed)
+        for k, v in REQUIRED_ATTRIBUTES.items():
+            ds[TOTAL_LAYER_NAME].attrs[k] = v
+        ds[TOTAL_LAYER_NAME].attrs["long_name"] = TOTAL_LAYER_LONG_NAME
         ds.to_netcdf(output_path)

src/openmethane_prior/raster.py

@@ -1,9 +1,10 @@
 import os
 
 import rasterio as rio
-from openmethane_prior.config import PriorConfig
 from rasterio.warp import Resampling, calculate_default_transform, reproject
 
+from openmethane_prior.config import PriorConfig
+
 
 def reproject_tiff(image, output, dst_crs="EPSG:4326", resampling="nearest", **kwargs):
     """Reprojects an image.

tests/test_om_prior.py

@@ -6,7 +6,6 @@
 import pandas as pd
 import requests
 import xarray as xr
-
 from openmethane_prior.layers.omGFASEmis import download_GFAS
 from openmethane_prior.utils import SECS_PER_YEAR
 
@@ -104,3 +103,14 @@ def test_compare_out_domain_with_cro_dot_files(output_domain, cro_xr, dot_xr):
 
     assert cro_xr.NCOLS == output_domain.COL.size
     assert cro_xr.NROWS == output_domain.ROW.size
+
+
+def test_required_attributes(output_domain):
+    assert output_domain.variables["OCH4_TOTAL"].attrs == {
+        "units": "kg/m^2/s",
+        "long_name": "total methane flux",
+    }
+    assert output_domain.variables["OCH4_WETLANDS"].attrs == {
+        "units": "kg/m^2/s",
+        "long_name": "OCH4_WETLANDS",
+    }