Add VIIRS L2 Reader

AUTHORS.md

@@ -88,3 +88,4 @@ The following people have made contributions to this project:
 - [Xin Zhang (zxdawn)](/~https://github.com/zxdawn)
 - [Yufei Zhu (yufeizhu600)](/~https://github.com/yufeizhu600)
 - [Youva Aoun (YouvaEUMex)](/~https://github.com/YouvaEUMex)
+- [Will Sharpe (wjsharpe)](/~https://github.com/wjsharpe)

satpy/etc/readers/viirs_l2.yaml

@@ -0,0 +1,126 @@
+reader:
+  name: viirs_l2
+  short_name: VIIRS L2
+  long_name: SNPP VIIRS Level 2 data in netCDF4 format
+  description: Generic NASA VIIRS L2 Reader
+  status: Alpha
+  supports_fsspec: false
+  reader: !!python/name:satpy.readers.yaml_reader.GEOFlippableFileYAMLReader
+  sensors: [viirs]
+
+file_types:
+  cldprop_l2_viirs:
+    file_reader: !!python/name:satpy.readers.viirs_l2.VIIRSL2FileHandler
+    file_patterns:
+      - 'CLDPROP_L2_VIIRS_{spacecraft_name:s}.A{start_time:%Y%j.%H%M}.{collection:03d}.{production_time:%Y%j%H%M%S}.nc'
+  cldmsk_l2_viirs:
+    file_reader: !!python/name:satpy.readers.viirs_l2.VIIRSL2FileHandler
+    file_patterns:
+      - 'CLDMSK_L2_VIIRS_{spacecraft_name:s}.A{start_time:%Y%j.%H%M}.{collection:03d}.{production_time:%Y%j%H%M%S}.nc'
+  aerdb_l2_viirs:
+    file_reader: !!python/name:satpy.readers.viirs_l2.VIIRSL2FileHandler
+    file_patterns:
+      - 'AERDB_L2_VIIRS_{spacecraft_name:s}.A{start_time:%Y%j.%H%M}.{collection:03d}.{production_time:%Y%j%H%M%S}.nc'
+      - 'AERDB_L2_VIIRS_{spacecraft_name:s}.A{start_time:%Y%j.%H%M}.{collection:03d}.nrt.nc'
+  cldir_l2_viirs:
+    file_reader: !!python/name:satpy.readers.viirs_l2.VIIRSL2FileHandler
+    file_patterns:
+      - 'CLDIR_L2_VIIRS_{spacecraft_name:s}.A{start_time:%Y%j.%H%M}.{collection:03d}.{production_time:%Y%j%H%M%S}.hdf'
+  aerdt_l2_viirs:
+    file_reader: !!python/name:satpy.readers.viirs_l2.VIIRSL2FileHandler
+    file_patterns:
+      - 'AERDT_L2_VIIRS_{spacecraft_name:s}.A{start_time:%Y%j.%H%M}.{collection:03d}.{production_time:%Y%j%H%M%S}.nc'
+  fsnrad_l2_viirs:
+    file_reader: !!python/name:satpy.readers.viirs_l2.VIIRSL2FileHandler
+    file_patterns:
+      - 'FSNRAD_L2_VIIRS_CRIS_{spacecraft_name:s}.A{start_time:%Y%j.%H%M}.{collection:03d}.{production_time:%Y%j%H%M%S}.nc'
+      - 'FSNRAD_L2_VIIRS_CRIS_SS_{spacecraft_name:s}.A{start_time:%Y%j.%H%M}.{collection:03d}.{production_time:%Y%j%H%M%S}.nc'
+
+datasets:
+  cld_lon:
+    name: cld_lon
+    resolution: 1000
+    file_type: [cldmsk_l2_viirs, cldprop_l2_viirs]
+    file_key: geolocation_data/longitude
+    units: degrees
+    standard_name: longitude
+  cld_lat:
+    name: cld_lat
+    resolution: 1000
+    file_type: [cldmsk_l2_viirs, cldprop_l2_viirs]
+    file_key: geolocation_data/latitude
+    units: degrees
+    standard_name: latitude
+  aerdb_lon:
+    name: aerdb_lon
+    resolution: 1000
+    file_type: [aerdb_l2_viirs]
+    file_key: Longitude
+    units: degrees
+    standard_name: longitude
+  aerdb_lat:
+    name: aerdb_lat
+    resolution: 1000
+    file_type: [aerdb_l2_viirs]
+    file_key: Latitude
+    units: degrees
+    standard_name: latitude
+  aerdt_lon:
+    name: aerdt_lon
+    resolution: 1000
+    file_type: [aerdt_l2_viirs]
+    file_key: longitude
+    units: degrees
+    standard_name: longitude
+  aerdt_lat:
+    name: aerdt_lat
+    resolution: 1000
+    file_type: [aerdt_l2_viirs]
+    file_key: latitude
+    units: degrees
+    standard_name: latitude
+
+##################################
+# Datasets in file cldmsk_l2_viirs
+##################################
+  Clear_Sky_Confidence:
+    name: Clear_Sky_Confidence
+    long_name: VIIRS Clear Sky Confidence
+    units: "1"
+    coordinates: [cld_lon, cld_lat]
+    file_key: geophysical_data/Clear_Sky_Confidence
+    file_type: cldmsk_l2_viirs
+    standard_name: clear_sky_confidence
+
+###################################
+# Datasets in file cldprop_l2_viirs
+###################################
+  Cloud_Top_Height:
+    name: Cloud_Top_Height
+    long_name: Cloud Top Height from NOAA CLAVR-x AWG algorithm
+    units: m
+    coordinates: [cld_lon,cld_lat]
+    file_key: geophysical_data/Cloud_Top_Height
+    file_type: cldprop_l2_viirs
+    standard_name: cloud_top_height
+
+##########################################
+# Datasets in files aerdb_l2_viirs
+##########################################
+  Angstrom_Exponent_Land_Ocean_Best_Estimate:
+    name: Angstrom_Exponent_Land_Ocean_Best_Estimate
+    long_name: Deep Blue/SOAR Angstrom exponent over land and ocean
+    units: "1"
+    coordinates: [aerdb_lon,aerdb_lat]
+    file_key: Angstrom_Exponent_Land_Ocean_Best_Estimate
+    file_type: [aerdb_l2_viirs]
+    standard_name: angstrom_exponent_land_ocean_best_estimate
+
+  Aerosol_Optical_Thickness_550_Land_Ocean:
+    name: Aerosol_Optical_Thickness_550_Land_Ocean_Best_Estimate
+    long_name: Deep Blue/SOAR aerosol optical thickness at 550 nm over land and ocean
+    units: "1"
+    coordinates: [aerdb_lon,aerdb_lat]
+    file_key: Aerosol_Optical_Thickness_550_Land_Ocean_Best_Estimate
+    file_type: [aerdb_l2_viirs]
+    standard_name: aerosol_optical_thickness_550_land_ocean

satpy/readers/viirs_l2.py

@@ -0,0 +1,176 @@
+"""Interface to VIIRS L2 format.
+
+This reader implements the support of L2 files generated using the VIIRS instrument on SNPP and NOAA satellite files.
+The intent of this reader is to be able to reproduce images from L2 layers in NASA worldview with identical colormaps.
+
+Currently a subset of four of these layers are supported
+1. Deep Blue Aerosol Angstrom Exponent (Land and Ocean)
+2. Clear Sky Confidence
+3. Cloud Top Height
+4. Deep Blue Aerosol Optical Thickness (Land and Ocean)
+"""
+import logging
+from datetime import datetime
+
+import numpy as np
+
+from satpy.readers.netcdf_utils import NetCDF4FileHandler
+
+LOG = logging.getLogger(__name__)
+
+
+class VIIRSL2FileHandler(NetCDF4FileHandler):
+    """NetCDF File Handler for VIIRS L2 Products."""
+    def _parse_datetime(self, datestr):
+        """Parse datetime."""
+        return datetime.strptime(datestr, "%Y-%m-%dT%H:%M:%S.000Z")
+
+    @property
+    def start_time(self):
+        """Get start time."""
+        return self._parse_datetime(self["/attr/time_coverage_start"])
+
+    @property
+    def end_time(self):
+        """Get end time."""
+        return self._parse_datetime(self["/attr/time_coverage_end"])
+
+    @property
+    def start_orbit_number(self):
+        """Get start orbit number."""
+        try:
+            return int(self["/attr/orbit_number"])
+        except KeyError:
+            return int(self["/attr/OrbitNumber"])
+
+    @property
+    def end_orbit_number(self):
+        """Get end orbit number."""
+        try:
+            return int(self["/attr/orbit_number"])
+        except KeyError:
+            return int(self["/attr/OrbitNumber"])
+
+    @property
+    def platform_name(self):
+        """Get platform name."""
+        try:
+            res = self.get("/attr/platform", self.filename_info["platform_shortname"])
+        except KeyError:
+            res = "Unknown"
+
+        return {
+            "JPSS-1": "NOAA-20",
+            "NP": "Suomi-NPP",
+            "J1": "NOAA-20",
+            "J2": "NOAA-21",
+            "JPSS-2": "NOAA-21",
+        }.get(res, res)
+
+    @property
+    def sensor_name(self):
+        """Get sensor name."""
+        return self["/attr/instrument"].lower()
+
+    def _get_dataset_file_units(self, ds_info, var_path):
+        file_units = ds_info.get("units")
+        if file_units is None:
+            file_units = self.get(var_path + "/attr/units")
+        if file_units == "none" or file_units == "None":
+            file_units = "1"
+        return file_units
+
+    def _get_dataset_valid_range(self, ds_info, var_path):
+        valid_min = self.get(var_path + "/attr/valid_min")
+        valid_max = self.get(var_path + "/attr/valid_max")
+        if not valid_min and not valid_max:
+            valid_range = self.get(var_path + "/attr/valid_range")
+            if valid_range is not None:
+                valid_min = valid_range[0]
+                valid_max = valid_range[1]
+        scale_factor = self.get(var_path + "/attr/scale_factor")
+        scale_offset = self.get(var_path + "/attr/add_offset")
+        return valid_min, valid_max, scale_factor, scale_offset
+
+    def get_metadata(self, dataset_id, ds_info):
+        """Get metadata."""
+        var_path = ds_info.get("file_key", ds_info["name"])
+        file_units = self._get_dataset_file_units(ds_info, var_path)
+
+        # Get extra metadata
+        i = getattr(self[var_path], "attrs", {})
+        i.update(ds_info)
+        i.update(dataset_id.to_dict())
+        i.update(
+            {
+                "file_units": file_units,
+                "platform_name": self.platform_name,
+                "sensor": self.sensor_name,
+                "start_orbit": self.start_orbit_number,
+                "end_orbit": self.end_orbit_number,
+            }
+        )
+        i.update(dataset_id.to_dict())
+        return i
+
+    def adjust_scaling_factors(self, factors, file_units, output_units):
+        """Adjust scaling factors."""
+        if factors is None or factors[0] is None:
+            factors = [1, 0]
+        if file_units == output_units:
+            LOG.debug("File units and output units are the same (%s)", file_units)
+            return factors
+        factors = np.array(factors)
+        return factors
+
+    def available_datasets(self, configured_datasets=None):
+        """Generate dataset info and their availablity.
+
+        See
+        :meth:`satpy.readers.file_handlers.BaseFileHandler.available_datasets`
+        for details.
+
+        """
+        for is_avail, ds_info in configured_datasets or []:
+            if is_avail is not None:
+                yield is_avail, ds_info
+                continue
+            ft_matches = self.file_type_matches(ds_info["file_type"])
+            if ft_matches is None:
+                yield None, ds_info
+                continue
+            var_path = ds_info.get("file_key", ds_info["name"])
+            yield var_path in self, ds_info
+
+    def get_dataset(self, ds_id, ds_info):
+        """Get DataArray for specified dataset."""
+        var_path = ds_info.get("file_key", ds_info["name"])
+        metadata = self.get_metadata(ds_id, ds_info)
+        (
+            valid_min,
+            valid_max,
+            scale_factor,
+            scale_offset,
+        ) = self._get_dataset_valid_range(ds_info, var_path)
+        data = self[var_path]
+        # For aerdb Longitude and Latitude datasets have coordinates
+        # This check is needed to work with yaml_reader
+        if "long_name" in metadata and metadata["long_name"] == "Longitude":
+            data.coords["Latitude"].attrs["standard_name"] = "latitude"
+        elif "long_name" in metadata and metadata["long_name"] == "Latitude":
+            data.coords["Longitude"].attrs["standard_name"] = "longitude"
+
+        data.attrs.update(metadata)
+        if valid_min is not None and valid_max is not None:
+            data = data.where((data >= valid_min) & (data <= valid_max))
+        factors = (scale_factor, scale_offset)
+        factors = self.adjust_scaling_factors(
+            factors, metadata["file_units"], ds_info.get("units")
+        )
+        if factors[0] != 1 or factors[1] != 0:
+            data *= factors[0]
+            data += factors[1]
+        # rename dimensions to correspond to satpy's 'y' and 'x' standard
+        if "number_of_lines" in data.dims:
+            data = data.rename({"number_of_lines": "y", "number_of_pixels": "x"})
+        return data