Add VolcanicAsh product to VIIRS EDR reader

satpy/etc/readers/viirs_edr.yaml

@@ -64,6 +64,12 @@ file_types:
         file_reader: !!python/name:satpy.readers.viirs_edr.VIIRSJRRFileHandler
         file_patterns:
             - 'JRR-IceAge_{version}_{platform_shortname}_s{start_time:%Y%m%d%H%M%S%f}_e{end_time:%Y%m%d%H%M%S%f}_c{creation_time}.nc'
+    jrr_volcanicash:
+        file_reader: !!python/name:satpy.readers.viirs_edr.VIIRSJRRFileHandler
+        drop_variables:
+          - Det_QF_Size
+        file_patterns:
+            - 'JRR-VolcanicAsh_{version}_{platform_shortname}_s{start_time:%Y%m%d%H%M%S%f}_e{end_time:%Y%m%d%H%M%S%f}_c{creation_time}.nc'
 
 
 datasets:

satpy/readers/viirs_edr.py

@@ -98,9 +98,11 @@ def __init__(self, filename, filename_info, filetype_info, **kwargs):
         # use entire scans as chunks
         row_chunks_m = max(get_chunk_size_limit() // 4 // M_COLS, 1)  # 32-bit floats
         row_chunks_i = row_chunks_m * 2
+        drop_variables = filetype_info.get("drop_variables", None)
         self.nc = xr.open_dataset(self.filename,
                                   decode_cf=True,
                                   mask_and_scale=True,
+                                  drop_variables=drop_variables,
                                   chunks={
                                       "Columns": -1,
                                       "Rows": row_chunks_m,

satpy/tests/reader_tests/test_viirs_edr.py

@@ -268,6 +268,24 @@ def _create_lst_variables() -> dict[str, xr.DataArray]:
     return data_vars
 
 
+@pytest.fixture(scope="module")
+def volcanic_ash_file(tmp_path_factory: TempPathFactory) -> Path:
+    """Generate fake *partial* Volcanic Ash VIIRs EDR file."""
+    fn = f"JRR-VolcanicAsh_v3r0_j01_s{START_TIME:%Y%m%d%H%M%S}0_e{END_TIME:%Y%m%d%H%M%S}0_c202307231023395.nc"
+    data_vars = _create_continuous_variables(
+        ("AshBeta",),
+        data_attrs={
+            "units": "1",
+            "_FillValue": -999.,
+        }
+    )
+    # The 'Det_QF_Size' variable is actually a scalar, but the there's no way to check it is dropped other than
+    # making it 2D
+    data_vars["Det_QF_Size"] = xr.DataArray(np.array([[1, 2]], dtype=np.int32),
+                                            attrs={"_FillValue": -999, "units": "1"})
+    return _create_fake_file(tmp_path_factory, fn, data_vars)
+
+
 def _create_continuous_variables(
         var_names: Iterable[str],
         data_attrs: None | dict = None
@@ -481,6 +499,17 @@ def test_get_platformname(self, surface_reflectance_file, filename_platform, exp
         scn.load(["surf_refl_I01"])
         assert scn["surf_refl_I01"].attrs["platform_name"] == exp_shortname
 
+    def test_volcanic_ash_drop_variables(self, volcanic_ash_file):
+        """Test that Det_QF_Size variable is dropped when reading VolcanicAsh products.
+
+        The said variable is also used as a dimension in v3r0 files, so the reading fails
+        if it is not dropped.
+        """
+        from satpy import Scene
+        scn = Scene(reader="viirs_edr", filenames=[volcanic_ash_file])
+        available = scn.available_dataset_names()
+        assert "Det_QF_Size" not in available
+
 
 def _check_surf_refl_qf_data_arr(data_arr: xr.DataArray, multiple_files: bool) -> None:
     _array_checks(data_arr, dtype=np.uint8, multiple_files=multiple_files)