Add reader for CAMEL emissivity datasets.

satpy/etc/readers/camel_l3_nc.yaml

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+reader:
+  name: camel_l3_nc
+  short_name: CAMEL L3
+  long_name: CAMEL emissivity level 3 data in netCDF4 format.
+  description: >
+    Reader for the CAMEL emissivity product, produced from various L2/L3
+    datasets on a monthly basis. More details
+    `here <https://lpdaac.usgs.gov/products/cam5k30emv002/>`_.
+  status: Nominal
+  supports_fsspec: false
+  sensors: [combined]
+  reader: !!python/name:satpy.readers.yaml_reader.FileYAMLReader
+
+file_types:
+    camel_emis_file:
+        file_reader: !!python/name:satpy.readers.camel_l3_nc.CAMELL3NCFileHandler
+        file_patterns:
+         - 'CAM5K30EM_emis_{start_period:%Y%m}_V{version:3s}.nc'
+
+
+datasets:
+  # QA products
+  aster_ndvi:
+    name: aster_ndvi
+    file_key: aster_ndvi
+    file_type: [ camel_emis_file ]
+  aster_qflag:
+    name: aster_qflag
+    file_key: aster_qflag
+    file_type: [ camel_emis_file ]
+  bfemis_qflag:
+    name: bfemis_qflag
+    file_key: bfemis_qflag
+    file_type: [ camel_emis_file ]
+  camel_qflag:
+    name: camel_qflag
+    file_key: camel_qflag
+    file_type: [ camel_emis_file ]
+  snow_fraction:
+    name: snow_fraction
+    file_key: snow_fraction
+    file_type: [ camel_emis_file ]
+
+  # Emissivity bands
+  camel_emis_b1:
+    name: camel_emis_b1
+    file_key: camel_emis
+    band_id: 0
+    file_type: [ camel_emis_file ]
+    wavelength: 3.6
+    resolution: 0.05
+
+  camel_emis_b2:
+    name: camel_emis_b2
+    file_key: camel_emis
+    band_id: 1
+    file_type: [ camel_emis_file ]
+    wavelength: 4.3
+    resolution: 0.05
+
+  camel_emis_b3:
+    name: camel_emis_b3
+    file_key: camel_emis
+    band_id: 2
+    file_type: [ camel_emis_file ]
+    wavelength: 5.0
+    resolution: 0.05
+
+  camel_emis_b4:
+    name: camel_emis_b4
+    file_key: camel_emis
+    band_id: 3
+    file_type: [ camel_emis_file ]
+    wavelength: 5.8
+    resolution: 0.05
+
+  camel_emis_b5:
+    name: camel_emis_b5
+    file_key: camel_emis
+    band_id: 4
+    file_type: [ camel_emis_file ]
+    wavelength: 7.6
+    resolution: 0.05
+
+  camel_emis_b6:
+    name: camel_emis_b6
+    file_key: camel_emis
+    band_id: 5
+    file_type: [ camel_emis_file ]
+    wavelength: 8.3
+    resolution: 0.05
+
+  camel_emis_b7:
+    name: camel_emis_b7
+    file_key: camel_emis
+    band_id: 6
+    file_type: [ camel_emis_file ]
+    wavelength: 8.6
+    resolution: 0.05
+
+  camel_emis_b8:
+    name: camel_emis_b8
+    file_key: camel_emis
+    band_id: 7
+    file_type: [ camel_emis_file ]
+    wavelength: 9.1
+    resolution: 0.05
+
+  camel_emis_b9:
+    name: camel_emis_b9
+    file_key: camel_emis
+    band_id: 8
+    file_type: [ camel_emis_file ]
+    wavelength: 10.6
+    resolution: 0.05
+
+  camel_emis_b10:
+    name: camel_emis_b10
+    file_key: camel_emis
+    band_id: 9
+    file_type: [ camel_emis_file ]
+    wavelength: 10.8
+    resolution: 0.05
+
+  camel_emis_b11:
+    name: camel_emis_b11
+    file_key: camel_emis
+    band_id: 10
+    file_type: [ camel_emis_file ]
+    wavelength: 11.3
+    resolution: 0.05
+
+  camel_emis_b12:
+    name: camel_emis_b12
+    file_key: camel_emis
+    band_id: 11
+    file_type: [ camel_emis_file ]
+    wavelength: 12.1
+    resolution: 0.05
+
+  camel_emis_b13:
+    name: camel_emis_b13
+    file_key: camel_emis
+    band_id: 12
+    file_type: [ camel_emis_file ]
+    wavelength: 14.3
+    resolution: 0.05

satpy/readers/camel_l3_nc.py

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+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+# Copyright (c) 2024 Satpy developers
+#
+# This file is part of satpy.
+#
+# satpy is free software: you can redistribute it and/or modify it under the
+# terms of the GNU General Public License as published by the Free Software
+# Foundation, either version 3 of the License, or (at your option) any later
+# version.
+#
+# satpy is distributed in the hope that it will be useful, but WITHOUT ANY
+# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+# A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along with
+# satpy.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Reader for CAMEL Level 3 emissivity files in netCDF4 format.
+
+For more information about the data, see: <https://lpdaac.usgs.gov/products/cam5k30emv002/>.
+
+NOTE: This reader only supports the global 0.05 degree grid data.
+"""
+
+
+import datetime as dt
+import logging
+
+import xarray as xr
+from pyresample import geometry
+
+from satpy.readers.file_handlers import BaseFileHandler
+
+logger = logging.getLogger(__name__)
+
+# Area extent for the CAMEL product (global)
+GLOB_AREA_EXT = [-180, -90, 180, 90]
+
+
+class CAMELL3NCFileHandler(BaseFileHandler):
+    """File handler for Himawari L2 NOAA enterprise data in netCDF format."""
+
+    def __init__(self, filename, filename_info, filetype_info):
+        """Initialize the reader."""
+        super().__init__(filename, filename_info, filetype_info)
+        self.nc = xr.open_dataset(self.filename,
+                                  decode_cf=True,
+                                  mask_and_scale=True,
+                                  chunks={"xc": "auto", "yc": "auto"})
+
+        if self.nc.attrs["geospatial_lon_resolution"] != "0.05 degree grid ":
+            raise ValueError("Only 0.05 degree grid data is supported.")
+        if self.nc.attrs["geospatial_lat_resolution"] != "0.05 degree grid ":
+            raise ValueError("Only 0.05 degree grid data is supported.")
+
+        self.nlines = self.nc.sizes["latitude"]
+        self.ncols = self.nc.sizes["longitude"]
+        self.area = None
+
+
+    @property
+    def start_time(self):
+        """Start timestamp of the dataset."""
+        date_str = self.nc.attrs["time_coverage_start"]
+        return dt.datetime.strptime(date_str, "%Y-%m-%d %H:%M:%SZ")
+
+    @property
+    def end_time(self):
+        """End timestamp of the dataset."""
+        date_str = self.nc.attrs["time_coverage_end"]
+        return dt.datetime.strptime(date_str, "%Y-%m-%d %H:%M:%SZ")
+
+
+    def get_dataset(self, key, info):
+        """Load a dataset."""
+        var = info["file_key"]
+        logger.debug("Reading in get_dataset %s.", var)
+        variable = self.nc[var]
+
+        # For the emissivity there are multiple bands, so we need to select the correct one
+        if var == "camel_emis":
+            if info["band_id"] >= variable.shape[2]:
+                raise ValueError("Band id requested is larger than dataset.")
+            variable = variable[:, :, info["band_id"]]
+
+        # Rename the latitude and longitude dimensions to x and y
+        variable = variable.rename({"latitude": "y", "longitude": "x"})
+
+        variable.attrs.update(key.to_dict())
+        return variable
+
+
+    def get_area_def(self, dsid):
+        """Get the area definition, a global lat/lon area for this type of dataset."""
+        proj_param = "EPSG:4326"
+
+        area = geometry.AreaDefinition("gridded_camel",
+                                       "A global gridded area",
+                                       "longlat",
+                                       proj_param,
+                                       self.ncols,
+                                       self.nlines,
+                                       GLOB_AREA_EXT)
+        self.area = area
+        return area

satpy/tests/reader_tests/test_camel_l3_nc.py

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+"""Tests for the CAMEL L3 netCDF reader."""
+
+import datetime as dt
+
+import numpy as np
+import pytest
+import xarray as xr
+
+from satpy.readers.camel_l3_nc import CAMELL3NCFileHandler
+from satpy.tests.utils import make_dataid
+
+rng = np.random.default_rng()
+ndvi_data = rng.integers(0, 1000, (3600, 7200), dtype=np.int16)
+emis_data = rng.integers(0, 1000, (3600, 7200, 5), dtype=np.int16)
+
+lon_data = np.arange(-180, 180, 0.05)
+lat_data = np.arange(-90, 90, 0.05)
+
+start_time = dt.datetime(2023, 8, 1, 0, 0, 0)
+end_time = dt.datetime(2023, 9, 1, 0, 0, 0)
+
+fill_val = -999
+scale_val = 0.001
+
+dimensions = {"longitude": 7200, "latitude": 3600, "spectra": 13}
+
+exp_ext = (-180.0, -90.0, 180.0, 90.0)
+
+global_attrs = {"time_coverage_start": start_time.strftime("%Y-%m-%d %H:%M:%SZ"),
+                "time_coverage_end": end_time.strftime("%Y-%m-%d %H:%M:%SZ"),
+                "geospatial_lon_resolution": "0.05 degree grid ",
+                "geospatial_lat_resolution": "0.05 degree grid ",
+                }
+
+bad_attrs1 = global_attrs.copy()
+bad_attrs1["geospatial_lon_resolution"] = "0.1 degree grid "
+bad_attrs2 = global_attrs.copy()
+bad_attrs2["geospatial_lat_resolution"] = "0.1 degree grid "
+
+
+def _make_ds(the_attrs, tmp_factory):
+    """Make a dataset for use in tests."""
+    fname = f'{tmp_factory.mktemp("data")}/CAM5K30EM_emis_202308_V003.nc'
+    ds = xr.Dataset({"aster_ndvi": (["Rows", "Columns"], ndvi_data),
+                     "camel_emis": (["latitude", "longitude", "spectra"], emis_data)},
+                    coords={"latitude": (["Rows"], lat_data),
+                            "longitude": (["Columns"], lon_data)},
+                    attrs=the_attrs)
+    ds.to_netcdf(fname)
+    return fname
+
+
+def camel_l3_filehandler(fname):
+    """Instantiate a Filehandler."""
+    fileinfo = {"start_period": "202308",
+                "version": "003"}
+    filetype = None
+    fh = CAMELL3NCFileHandler(fname, fileinfo, filetype)
+    return fh
+
+
+@pytest.fixture(scope="session")
+def camel_filename(tmp_path_factory):
+    """Create a fake camel l3 file."""
+    return _make_ds(global_attrs, tmp_path_factory)
+
+
+@pytest.fixture(scope="session")
+def camel_filename_bad1(tmp_path_factory):
+    """Create a fake camel l3 file."""
+    return _make_ds(bad_attrs1, tmp_path_factory)
+
+
+@pytest.fixture(scope="session")
+def camel_filename_bad2(tmp_path_factory):
+    """Create a fake camel l3 file."""
+    return _make_ds(bad_attrs2, tmp_path_factory)
+
+
+def test_startend(camel_filename):
+    """Test start and end times are set correctly."""
+    fh = camel_l3_filehandler(camel_filename)
+    assert fh.start_time == start_time
+    assert fh.end_time == end_time
+
+
+def test_camel_l3_area_def(camel_filename, caplog):
+    """Test reader handles area definition correctly."""
+    ps = "+proj=longlat +datum=WGS84 +no_defs +type=crs"
+
+    # Check case where input data is correct size.
+    fh = camel_l3_filehandler(camel_filename)
+    ndvi_id = make_dataid(name="aster_ndvi")
+    area_def = fh.get_area_def(ndvi_id)
+    assert area_def.width == dimensions["longitude"]
+    assert area_def.height == dimensions["latitude"]
+    assert np.allclose(area_def.area_extent, exp_ext)
+
+    assert area_def.proj4_string == ps
+
+
+def test_bad_longitude(camel_filename_bad1):
+    """Check case where longitude grid is not correct."""
+    with pytest.raises(ValueError, match="Only 0.05 degree grid data is supported."):
+        camel_l3_filehandler(camel_filename_bad1)
+
+
+def test_bad_latitude(camel_filename_bad2):
+    """Check case where latitude grid is not correct."""
+    with pytest.raises(ValueError, match="Only 0.05 degree grid data is supported."):
+        camel_l3_filehandler(camel_filename_bad2)
+
+
+def test_load_ndvi_data(camel_filename):
+    """Test that data is loaded successfully."""
+    fh = camel_l3_filehandler(camel_filename)
+    ndvi_id = make_dataid(name="aster_ndvi")
+    ndvi = fh.get_dataset(ndvi_id, {"file_key": "aster_ndvi"})
+    assert np.allclose(ndvi.data, ndvi_data)
+
+
+def test_load_emis_data(camel_filename):
+    """Test that data is loaded successfully."""
+    fh = camel_l3_filehandler(camel_filename)
+    emis_id = make_dataid(name="camel_emis")
+
+    # This is correct data
+    emis = fh.get_dataset(emis_id, {"file_key": "camel_emis", "band_id": 2})
+    assert np.allclose(emis.data, emis_data[:, :, 2])
+
+    # This will fail as we are requesting a band too high data
+    with pytest.raises(ValueError, match="Band id requested is larger than dataset."):
+        fh.get_dataset(emis_id, {"file_key": "camel_emis", "band_id": 12})