Source code for satpy.readers.seviri_l2_bufr

#!/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 <http://www.gnu.org/licenses/>.

"""SEVIRI L2 BUFR format reader.

References:
    EUMETSAT Product Navigator
    https://navigator.eumetsat.int/

"""

import datetime as dt
import logging

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

from satpy.readers._geos_area import get_geos_area_naming
from satpy.readers.eum_base import get_service_mode, recarray2dict
from satpy.readers.file_handlers import BaseFileHandler
from satpy.readers.seviri_base import mpef_product_header
from satpy.resample import get_area_def
from satpy.utils import get_legacy_chunk_size

try:
    import eccodes as ec
except ImportError:
    raise ImportError(
        "Missing eccodes-python and/or eccodes C-library installation. Use conda to install eccodes")

CHUNK_SIZE = get_legacy_chunk_size()
logger = logging.getLogger("SeviriL2Bufr")

data_center_dict = {55: {"ssp": "E0415", "name": "08"}, 56: {"ssp": "E0455", "name": "09"},
                    57: {"ssp": "E0095", "name": "10"}, 70: {"ssp": "E0000", "name": "11"}}

seg_size_dict = {"seviri_l2_bufr_asr": 16, "seviri_l2_bufr_cla": 16,
                 "seviri_l2_bufr_csr": 16, "seviri_l2_bufr_gii": 3,
                 "seviri_l2_bufr_thu": 16, "seviri_l2_bufr_toz": 3,
                 "seviri_l2_bufr_amv": 24}


[docs] class SeviriL2BufrFileHandler(BaseFileHandler): """File handler for SEVIRI L2 BUFR products. **Loading data with AreaDefinition** By providing the `with_area_definition` as True in the `reader_kwargs`, the dataset is loaded with an AreaDefinition using a standardized AreaDefinition in areas.yaml. By default, the dataset will be loaded with a SwathDefinition, i.e. similar to how the data are stored in the BUFR file: scene = satpy.Scene(filenames, reader='seviri_l2_bufr', reader_kwargs={'with_area_definition': False}) **Defining dataset recticifation longitude** The BUFR data were originally extracted from a rectified two-dimensional grid with a given central longitude (typically the sub-satellite point). This information is not available in the file itself nor the filename (for files from the EUMETSAT archive). Also, it cannot be reliably derived from all datasets themselves. Hence, the rectification longitude can be defined by the user by providing `rectification_longitude` in the `reader_kwargs`: scene = satpy.Scene(filenames, reader='seviri_l2_bufr', reader_kwargs={'rectification_longitude': 0.0}) If not done, default values applicable to the operational grids of the respective SEVIRI instruments will be used. """ def __init__(self, filename, filename_info, filetype_info, with_area_definition=False, rectification_longitude="default", **kwargs): """Initialise the file handler for SEVIRI L2 BUFR data.""" super(SeviriL2BufrFileHandler, self).__init__(filename, filename_info, filetype_info) if ("server" in filename_info): # EUMETSAT Offline Bufr product self.mpef_header = self._read_mpef_header() else: # Product was retrieved from the EUMETSAT Data Center timeStr = self.get_attribute("typicalDate")+self.get_attribute("typicalTime") buf_start_time = dt.datetime.strptime(timeStr, "%Y%m%d%H%M%S") sc_id = self.get_attribute("satelliteIdentifier") self.mpef_header = {} self.mpef_header["NominalTime"] = buf_start_time self.mpef_header["SpacecraftName"] = data_center_dict[sc_id]["name"] self.mpef_header["RectificationLongitude"] = data_center_dict[sc_id]["ssp"] if rectification_longitude != "default": self.mpef_header["RectificationLongitude"] = f"E{int(rectification_longitude * 10):04d}" self.with_adef = with_area_definition if self.with_adef and filetype_info["file_type"] == "seviri_l2_bufr_amv": logging.warning("AMV BUFR data cannot be loaded with an area definition. Setting self.with_def = False.") self.with_adef = False self.seg_size = seg_size_dict[filetype_info["file_type"]] @property def start_time(self): """Return the repeat cycle start time.""" return self.mpef_header["NominalTime"] @property def end_time(self): """Return the repeat cycle end time.""" return self.start_time + dt.timedelta(minutes=15) @property def platform_name(self): """Return spacecraft name.""" return "MET{}".format(self.mpef_header["SpacecraftName"]) @property def ssp_lon(self): """Return subsatellite point longitude.""" # e.g. E0415 ssp_lon = self.mpef_header["RectificationLongitude"] return float(ssp_lon[1:])/10.
[docs] def get_area_def(self, key): """Return the area definition.""" try: return self._area_def except AttributeError: raise NotImplementedError
[docs] def _read_mpef_header(self): """Read MPEF header.""" hdr = np.fromfile(self.filename, mpef_product_header, 1) return recarray2dict(hdr)
[docs] def get_attribute(self, key): """Get BUFR attributes.""" # This function is inefficient as it is looping through the entire # file to get 1 attribute. It causes a problem though if you break # from the file early - dont know why but investigating - fix later fh = open(self.filename, "rb") while True: # get handle for message bufr = ec.codes_bufr_new_from_file(fh) if bufr is None: break ec.codes_set(bufr, "unpack", 1) attr = ec.codes_get(bufr, key) ec.codes_release(bufr) fh.close() return attr
[docs] def get_array(self, key): """Get all data from file for the given BUFR key.""" with open(self.filename, "rb") as fh: msgCount = 0 while True: bufr = ec.codes_bufr_new_from_file(fh) if bufr is None: break ec.codes_set(bufr, "unpack", 1) # if is the first message initialise our final array if (msgCount == 0): arr = da.from_array(ec.codes_get_array( bufr, key, float), chunks=CHUNK_SIZE) else: tmpArr = da.from_array(ec.codes_get_array( bufr, key, float), chunks=CHUNK_SIZE) arr = da.concatenate((arr, tmpArr)) msgCount = msgCount+1 ec.codes_release(bufr) if arr.size == 1: arr = arr[0] return arr
[docs] def get_dataset(self, dataset_id, dataset_info): """Create dataset. Load data from BUFR file using the BUFR key in dataset_info and create the dataset with or without an AreaDefinition. """ arr = self.get_array(dataset_info["key"]) if self.with_adef: xarr = self.get_dataset_with_area_def(arr, dataset_id) # coordinates are not relevant when returning data with an AreaDefinition if "coordinates" in dataset_info.keys(): del dataset_info["coordinates"] else: xarr = xr.DataArray(arr, dims=["y"]) if "fill_value" in dataset_info: xarr = xarr.where(xarr != dataset_info["fill_value"]) self._add_attributes(xarr, dataset_info) return xarr
[docs] def get_dataset_with_area_def(self, arr, dataset_id): """Get dataset with an AreaDefinition.""" if dataset_id["name"] in ["latitude", "longitude"]: self.__setattr__(dataset_id["name"], arr) xarr = xr.DataArray(arr, dims=["y"]) else: lons_1d, lats_1d, data_1d = da.compute(self.longitude, self.latitude, arr) self._area_def = self._construct_area_def(dataset_id) icol, irow = self._area_def.get_array_indices_from_lonlat(lons_1d, lats_1d) data_2d = np.empty(self._area_def.shape) data_2d[:] = np.nan data_2d[irow.compressed(), icol.compressed()] = data_1d[~irow.mask] xarr = xr.DataArray(da.from_array(data_2d, CHUNK_SIZE), dims=("y", "x")) ntotal = len(icol) nvalid = len(icol.compressed()) if nvalid < ntotal: logging.warning(f"{ntotal-nvalid} out of {ntotal} data points could not be put on " f"the grid {self._area_def.area_id}.") return xarr
[docs] def _construct_area_def(self, dataset_id): """Construct a standardized AreaDefinition based on satellite, instrument, resolution and sub-satellite point. Returns: AreaDefinition: A pyresample AreaDefinition object containing the area definition. """ res = dataset_id["resolution"] area_naming_input_dict = {"platform_name": "msg", "instrument_name": "seviri", "resolution": res, } area_naming = get_geos_area_naming({**area_naming_input_dict, **get_service_mode("seviri", self.ssp_lon)}) # Datasets with a segment size of 3 pixels extend outside the original SEVIRI 3km grid (with 1238 x 1238 # segments a 3 pixels). Hence, we need to use corresponding area defintions in areas.yaml if self.seg_size == 3: area_naming["area_id"] += "_ext" area_naming["description"] += " (extended outside original 3km grid)" # Construct AreaDefinition from standardized area definition in areas.yaml. stand_area_def = get_area_def(area_naming["area_id"]) return stand_area_def
[docs] def _add_attributes(self, xarr, dataset_info): """Add dataset attributes to xarray.""" xarr.attrs["sensor"] = "SEVIRI" xarr.attrs["platform_name"] = self.platform_name xarr.attrs["ssp_lon"] = self.ssp_lon xarr.attrs["seg_size"] = self.seg_size xarr.attrs.update(dataset_info)