Source code for satpy.readers.fy4_base

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Copyright (c) 2019 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 <>.
"""Base reader for the L1 HDF data from the AGRI and GHI instruments aboard the FengYun-4A/B satellites.

The files read by this reader are described in the official Real Time Data Service:


import logging
from datetime import datetime

import dask.array as da
import numpy as np
import xarray as xr

from satpy._compat import cached_property
from satpy.readers._geos_area import get_area_definition, get_area_extent
from satpy.readers.hdf5_utils import HDF5FileHandler

logger = logging.getLogger(__name__)

RESOLUTION_LIST = [250, 500, 1000, 2000, 4000]

[docs] class FY4Base(HDF5FileHandler): """The base class for the FengYun4 AGRI and GHI readers.""" def __init__(self, filename, filename_info, filetype_info): """Init filehandler.""" super(FY4Base, self).__init__(filename, filename_info, filetype_info) self.sensor = filename_info['instrument'] # info of 250m, 500m, 1km, 2km and 4km data self._COFF_list = [21983.5, 10991.5, 5495.5, 2747.5, 1373.5] self._LOFF_list = [21983.5, 10991.5, 5495.5, 2747.5, 1373.5] self._CFAC_list = [163730199.0, 81865099.0, 40932549.0, 20466274.0, 10233137.0] self._LFAC_list = [163730199.0, 81865099.0, 40932549.0, 20466274.0, 10233137.0] self.PLATFORM_NAMES = {'FY4A': 'FY-4A', 'FY4B': 'FY-4B', 'FY4C': 'FY-4C'} try: self.PLATFORM_ID = self.PLATFORM_NAMES[filename_info['platform_id']] except KeyError: raise KeyError(f"Unsupported platform ID: {filename_info['platform_id']}") self.CHANS_ID = 'NOMChannel' self.SAT_ID = 'NOMSatellite' self.SUN_ID = 'NOMSun'
[docs] @staticmethod def scale(dn, slope, offset): """Convert digital number (DN) to calibrated quantity through scaling. Args: dn: Raw detector digital number slope: Slope offset: Offset Returns: Scaled data """ ref = dn * slope + offset ref = ref.clip(min=0) ref.attrs = dn.attrs return ref
[docs] def apply_lut(self, data, lut): """Calibrate digital number (DN) by applying a LUT. Args: data: Raw detector digital number lut: the look up table Returns: Calibrated quantity """ # append nan to the end of lut for fillvalue lut = np.append(lut, np.nan) = da.where( > lut.shape[0], lut.shape[0] - 1, res =, lut, dtype=lut.dtype) res = xr.DataArray(res, dims=data.dims, attrs=data.attrs, coords=data.coords) return res
[docs] @staticmethod def _getitem(block, lut): return lut[block]
@cached_property def reflectance_coeffs(self): """Retrieve the reflectance calibration coefficients from the HDF file.""" # using the corresponding SCALE and OFFSET if self.PLATFORM_ID == 'FY-4A': cal_coef = 'CALIBRATION_COEF(SCALE+OFFSET)' elif self.PLATFORM_ID == 'FY-4B': cal_coef = 'Calibration/CALIBRATION_COEF(SCALE+OFFSET)' else: raise KeyError(f"Unsupported platform ID for calibration: {self.PLATFORM_ID}") return self.get(cal_coef).values
[docs] def calibrate(self, data, ds_info, ds_name, file_key): """Calibrate the data.""" # Check if calibration is present, if not assume dataset is an angle calibration = ds_info.get('calibration') # Return raw data in case of counts or no calibration if calibration in ('counts', None): data.attrs['units'] = ds_info['units'] ds_info['valid_range'] = data.attrs['valid_range'] ds_info['fill_value'] = data.attrs['FillValue'].item() elif calibration == 'reflectance': channel_index = int(file_key[-2:]) - 1 data = self.calibrate_to_reflectance(data, channel_index, ds_info) elif calibration == 'brightness_temperature': data = self.calibrate_to_bt(data, ds_info, ds_name) elif calibration == 'radiance': raise NotImplementedError("Calibration to radiance is not supported.") # Apply range limits, but not for counts or we convert to float! if calibration != 'counts': data = data.where((data >= min(data.attrs['valid_range'])) & (data <= max(data.attrs['valid_range']))) else: data.attrs['_FillValue'] = data.attrs['FillValue'].item() return data
[docs] def calibrate_to_reflectance(self, data, channel_index, ds_info): """Calibrate to reflectance [%].""" logger.debug("Calibrating to reflectances") # using the corresponding SCALE and OFFSET if self.sensor != 'AGRI' and self.sensor != 'GHI': raise ValueError(f'Unsupported sensor type: {self.sensor}') coeffs = self.reflectance_coeffs num_channel = coeffs.shape[0] if self.sensor == 'AGRI' and num_channel == 1: # only channel_2, resolution = 500 m channel_index = 0 = da.where( == data.attrs['FillValue'].item(), np.nan, data.attrs['scale_factor'] = coeffs[channel_index, 0].item() data.attrs['add_offset'] = coeffs[channel_index, 1].item() data = self.scale(data, data.attrs['scale_factor'], data.attrs['add_offset']) data *= 100 ds_info['valid_range'] = (data.attrs['valid_range'] * data.attrs['scale_factor'] + data.attrs['add_offset']) ds_info['valid_range'] = ds_info['valid_range'] * 100 return data
[docs] def calibrate_to_bt(self, data, ds_info, ds_name): """Calibrate to Brightness Temperatures [K].""" logger.debug("Calibrating to brightness_temperature") if self.sensor not in ['GHI', 'AGRI']: raise ValueError("Error, sensor must be GHI or AGRI.") # The key is sometimes prefixes with `Calibration/` so we try both options here lut_key = ds_info.get('lut_key', ds_name) try: lut = self[lut_key] except KeyError: lut_key = f'Calibration/{ds_info.get("lut_key", ds_name)}' lut = self[lut_key] # the value of dn is the index of brightness_temperature data = self.apply_lut(data, lut) ds_info['valid_range'] = lut.attrs['valid_range'] return data
@property def start_time(self): """Get the start time.""" start_time = self['/attr/Observing Beginning Date'] + 'T' + self['/attr/Observing Beginning Time'] + 'Z' try: return datetime.strptime(start_time, '%Y-%m-%dT%H:%M:%S.%fZ') except ValueError: # For some data there is no sub-second component return datetime.strptime(start_time, '%Y-%m-%dT%H:%M:%SZ') @property def end_time(self): """Get the end time.""" end_time = self['/attr/Observing Ending Date'] + 'T' + self['/attr/Observing Ending Time'] + 'Z' try: return datetime.strptime(end_time, '%Y-%m-%dT%H:%M:%S.%fZ') except ValueError: # For some data there is no sub-second component return datetime.strptime(end_time, '%Y-%m-%dT%H:%M:%SZ')
[docs] def get_area_def(self, key): """Get the area definition.""" # Coordination Group for Meteorological Satellites LRIT/HRIT Global Specification # res = key['resolution'] pdict = {} begin_cols = float(self.file_content['/attr/Begin Pixel Number']) end_lines = float(self.file_content['/attr/End Line Number']) pdict['coff'] = self._COFF_list[RESOLUTION_LIST.index(res)] - begin_cols + 1 pdict['loff'] = -self._LOFF_list[RESOLUTION_LIST.index(res)] + end_lines + 1 pdict['cfac'] = self._CFAC_list[RESOLUTION_LIST.index(res)] pdict['lfac'] = self._LFAC_list[RESOLUTION_LIST.index(res)] try: pdict['a'] = float(self.file_content['/attr/Semimajor axis of ellipsoid']) except KeyError: pdict['a'] = float(self.file_content['/attr/dEA']) if pdict['a'] < 10000: pdict['a'] = pdict['a'] * 1E3 # equator radius (m) try: pdict['b'] = float(self.file_content['/attr/Semiminor axis of ellipsoid']) except KeyError: pdict['b'] = pdict['a'] * (1 - 1 / self.file_content['/attr/dObRecFlat']) # polar radius (m) pdict['h'] = self.file_content['/attr/NOMSatHeight'] # the altitude of satellite (m) if pdict['h'] > 42000000.0: pdict['h'] = pdict['h'] - pdict['a'] pdict['ssp_lon'] = float(self.file_content['/attr/NOMCenterLon']) pdict['nlines'] = float(self.file_content['/attr/RegLength']) pdict['ncols'] = float(self.file_content['/attr/RegWidth']) pdict['scandir'] = 'N2S' pdict['a_desc'] = "FY-4 {} area".format(self.filename_info['observation_type']) pdict['a_name'] = f'{self.filename_info["observation_type"]}_{res}m' pdict['p_id'] = f'FY-4, {res}m' area_extent = get_area_extent(pdict) area_extent = (area_extent[0], area_extent[1], area_extent[2], area_extent[3]) area = get_area_definition(pdict, area_extent) return area