convert_2hempa.py

from datetime import datetime
from datetime import timedelta
import struct
import numpy as np
from numpy import dtype
import netCDF4
from netCDF4 import stringtochar
import argparse
import warnings

warnings.simplefilter('ignore', DeprecationWarning)


def main():
    parser = argparse.ArgumentParser()
    parser.add_argument("grib")
    parser.add_argument("netcdf")
    args = parser.parse_args()
    converter = Converter()
    converter.convert(args)


class Converter:
    _FillValueF32 = np.array(9.999e20, "float32")
    _FillValueF64 = np.array(9.999e20, "float64")
    _FillValueI32 = np.array(-9999, "int32")

    def convert(self, args):
        self.gribpath = args.grib
        self.ncpath = args.netcdf
        self.read_grib()
        self.write_netcdf()

    def read_grib(self):
        with open(self.gribpath, "rb") as f:
            data = bytearray(f.read())

        offset = 0

        # Section 0
        offset += 16

        # Section 1
        year = read_int(data, 13, 14, offset)
        month = read_int(data, 15, 15, offset)
        day = read_int(data, 16, 16, offset)
        hour = read_int(data, 17, 17, offset)
        minute = read_int(data, 18, 18, offset)
        second = read_int(data, 19, 19, offset)
        tstr = f"{year:0>4}-{month:0>2}-{day:0>2}T{hour:0>2}:{minute:0>2}:{second:0>2}"
        self.time_reference = datetime.strptime(tstr, "%Y-%m-%dT%H:%M:%S")
        offset += read_int(data, 1, 4, offset)

        # The time(time) coordinate variable stores the time of each ray, in seconds, from a reference time,
        # which is normally the start of the volume (time_coverage_start)
        # but may be a specified reference time (time_reference)
        self.time = []

        # The elevation(time) coordinate variable stores the elevation angle for each ray.
        self.elevation = []

        # The azimuth(time) coordinate variable stores the azimuth angle for each ray
        self.azimuth = []

        # The number of the sweep, in the volume scan. 0-based.
        self.sweep_number = []

        # Options are: "sector", "coplane", rhi", "vertical_pointing", "idle", "azimuth_surveillance", "elevation_surveillance", "sunscan", "pointing", "manual_ppi", "manual_rhi"
        self.sweep_mode = []

        # Target angle for the sweep. elevation in most modes. azimuth in RHI mode.
        self.fixed_angle = []

        # Index of first ray in sweep, relative to start of volume. 0-based
        self.sweep_start_ray_index = []

        # Index of last ray in sweep, relative to start of volume. 0-based
        self.sweep_end_ray_index = []

        # Nbの最大値
        self.max_Nb = 0
        self.Nb_list = []
        self.Nr_list = []
        sweep_index = 0

        self.data = []

        while True:
            # Section 8 終端節
            if data[offset:offset + 4] == b"7777":
                break

            # Section 3 格子系定義節
            if data[offset + 4] == 3:
                template_number = read_int(data, 13, 14, offset)
                if template_number != 50121:
                    raise GRIBDecodeError(
                        f"template 3.{template_number}には対応していません")

                h_sweep_mode = read_int(data, 39, 39, offset)
                if h_sweep_mode != 0:
                    raise GRIBDecodeError(
                        f"：走査モード(水平極座標) {h_sweep_mode}には対応していません")

                Nb = read_int(data, 15, 18, offset)  # 径線に沿った資料ビン(data bins)の数
                Nr = read_int(data, 19, 22, offset)  # 径線の数
                Dx = read_int(data, 31, 34, offset) * 1e-3  # 径線に沿ったビンの間隔
                Dstart = read_int(data, 35, 38, offset)
                fixed_angle = read_int_sgn(data, 43, 44, offset) * 1e-2
                Fa = read_int(data, 53, 53, offset)
                Fe = read_int(data, 54, 54, offset)

                self.Nb_list.append(Nb)
                self.Nr_list.append(Nr)

                self.fixed_angle.append(fixed_angle)
                if fixed_angle < 90:
                    self.sweep_mode.append("azimuth_surveillance")
                else:
                    self.sweep_mode.append("vertical_pointing")

                radar_range = Dstart + np.arange(Nb) * Dx + Dx / 2
                if Nb > self.max_Nb:
                    self.max_Nb = Nb
                    self.radar_range = radar_range

                self.sweep_start_ray_index.append(len(self.azimuth))
                for x in range(1, Nr + 1):
                    i0 = (58 + 2 * x - 1) * Fa
                    i1 = (58 + 2 * x) * Fa
                    azimuth = read_int(data, i0, i1, offset) * 1e-2
                    self.azimuth.append(azimuth)

                    i0 = (58 + 2 * Nr * Fa + 2 * x - 1) * Fe
                    i1 = (58 + 2 * Nr * Fa + 2 * x) * Fe
                    elevation = read_int_sgn(data, i0, i1, offset) * 1e-2
                    self.elevation.append(elevation)
                self.sweep_end_ray_index.append(len(self.azimuth) - 1)

            # Section 4 プロダクト定義節
            if data[offset + 4] == 4:
                template_number = read_int(data, 8, 9, offset)
                if template_number != 51123:
                    raise GRIBDecodeError(
                        f"template 4.{template_number}には対応していません")

                self.parameter_number = read_int(data, 11, 11, offset)
                self.latitude = read_int(data, 14, 17, offset) * 1e-6
                self.longitude = read_int(data, 18, 21, offset) * 1e-6
                self.altitude = read_int(data, 22, 23, offset) * 1e-1
                self.site_id = read_int(data, 28, 29, offset)
                self.time_start = read_int_sgn(data, 33, 34, offset)
                self.time_end = read_int_sgn(data, 35, 36, offset)
                self.frequency = read_int(data, 37, 40, offset) * 1e3
                Fp = read_int(data, 56, 56, offset)
                Ft = read_int(data, 57, 57, offset)

                time_sum = self.time_start
                for x in range(1, Nr + 1):
                    i0 = (61 + 2 * Nr * Fp + 2 * x - 1) * Ft
                    i1 = (61 + 2 * Nr * Fp + 2 * x) * Ft
                    time = read_int(data, i0, i1, offset) * 1e-3
                    time_sum += time
                    self.time.append(time_sum - time / 2)

                self.sweep_number.append(len(self.sweep_number))
                sweep_index += 1

            # Section 5 資料表現節
            if data[offset + 4] == 5:
                template_number = read_int(data, 10, 11, offset)
                if template_number != 0:
                    raise GRIBDecodeError(
                        f"template 5.{template_number}には対応していません")

                total_points = read_int(data, 6, 9, offset)
                R = read_float(data, 12, 15, offset)
                E = read_int(data, 16, 17, offset)
                D = read_int(data, 18, 19, offset)
                data_byte = int(read_int(data, 20, 20, offset) / 8)

            # Section 7 資料節
            if data[offset + 4] == 7:
                if self.parameter_number in [206, 215]:  # QCI
                    for i in range(total_points):
                        i0 = 6 + i * data_byte
                        i1 = 6 + (i + 1) * data_byte - 1
                        Z = read_int(data, i0, i1, offset)
                        Y = int((R + Z * 2 ** E) * 10 ** (-D))
                        self.data.append(Y)
                    self.data = np.array(
                        self.data, dtype="uint8").reshape((Nr, Nb))
                else:
                    for i in range(total_points):
                        i0 = 6 + i * data_byte
                        i1 = 6 + (i + 1) * data_byte - 1
                        Z = read_int(data, i0, i1, offset)
                        if Z == 2 ** (data_byte * 8) - 1:
                            Y = self._FillValueF32
                        else:
                            Y = (R + Z * 2 ** E) * 10 ** (-D)
                        self.data.append(Y)
                    self.data = np.array(
                        self.data, dtype="float32").reshape((Nr, Nb))
            offset += read_int(data, 1, 4, offset)

    def write_netcdf(self):
        self.nc = netCDF4.Dataset(self.ncpath, "w", format="NETCDF4")
        self.write_global_attributes()  # Section 4.1
        self.write_dimensions()  # Section 4.2
        self.write_global_variables()  # Section 4.3
        self.write_coordinate_variables()  # Section 4.4
        # Section 4.5 Ray dimension variables: ommited
        self.write_location_variables()  # Section 4.6
        self.write_sweep_variables()  # Section 4.7
        self.write_sensor_pointing_variables()  # Section 4.8
        # Section 4.9 Moving platform geo-reference variables: omitted
        self.write_moments_field_data_variables()  # Section 4.10
        self.write_instrument_parameters()  # Section 5.1
        self.nc.close()

    def write_global_attributes(self):
        nc = self.nc

        # Conventions string will specify CF/Radial, plus selected sub-conventions as applicable
        nc.setncattr("Conventions", "CF/Radial instrument_parameters")

        # [optional] CF/Radial version number
        nc.setncattr("version", "1.3")

        # Short description of file contents
        nc.setncattr("title", "")

        # Where the original data were produced
        nc.setncattr("institution", "Japan Meteorological Agency")

        # Method of production of the original data
        nc.setncattr("source", "")

        # List of modifications to the original data
        nc.setncattr("history", "")

        # Miscellaneous information
        nc.setncattr("comment", "")

        # Name of radar or lidar
        nc.setncattr("instrument_name", "")

        # [optional] Name of site where data were gathered
        nc.setncattr("site_name", str(self.site_id))

        # [optional] Name of scan strategy used, if applicable
        nc.setncattr("scan_name", "")

        # [optional] Scan strategy id, if applicable. Assumed 0 if missing
        nc.setncattr("scan_id", "0")

        # [optional] "true" or "false" Assumed "false" if missing.
        nc.setncattr("platform_is_mobile", "false")

        # [optional] "true" or "false" Assumed "false" if missing.
        nc.setncattr("n_gates_vary", "false")

        # [optional] "true" or "false" Assumed "true”" if missing. This is set to false if the rays are not stored in time order.
        nc.setncattr("ray_times_increase", "true")

        # [optional] Comma-delimited list of field names included in this file.
        nc.setncattr("field_names", "")

    def write_dimensions(self):
        nc = self.nc

        # The number of rays. This dimension is optionally UNLIMITED
        nc.createDimension("time", len(self.time))

        # The number of range bin
        nc.createDimension("range", self.max_Nb)

        # The number of sweeps
        nc.createDimension("sweep", len(self.sweep_number))

        # [optional] Number of frequencies used
        nc.createDimension("frequency", 1)

        nc.createDimension("string_length", None)

    def write_global_variables(self):
        nc = self.nc

        # Volume numbers are sequential, relative to some arbitrary start time, and may wrap.
        volume_number = nc.createVariable("volume_number", dtype("int32").char)
        volume_number[:] = 0  # 暫定的に0を格納
        volume_number.long_name = "data_volume_index_number"
        volume_number.units = "unitless"

        # TC time of first ray in file. Resolution is integer seconds.
        # The time(time) variable is computed relative to this time.
        # Format is: yyyy-mm-ddThh:mm:ssZ
        time_coverage_start = nc.createVariable(
            "time_coverage_start", "S1", ('string_length'))
        t = self.time_reference + timedelta(seconds=self.time_start)
        tstr = t.strftime("%Y-%m-%dT%H:%M:%SZ")
        datain = np.array(tstr, dtype="S20")
        time_coverage_start[:] = stringtochar(datain)
        time_coverage_start.long_name = "data_volume_start_time_utc"
        time_coverage_start.units = "unitless"

        # UTC time of last ray in file. Resolution is integer seconds.
        # Format is: yyyy-mm-ddThh:mm:ssZ
        time_coverage_end = nc.createVariable(
            "time_coverage_end", "S1", ('string_length'))
        t = self.time_reference + timedelta(seconds=self.time_end)
        tstr = t.strftime("%Y-%m-%dT%H:%M:%SZ")
        datain = np.array(tstr, dtype="S20")
        time_coverage_end[:] = stringtochar(datain)
        time_coverage_end.long_name = "data_volume_end_time_utc"
        time_coverage_end.units = "unitless"

        # UTC time reference. Resolution is integer seconds.
        # If defined, the time(time) variable is computed relative to this time instead of relative to time_coverage_start.
        # Format is: yyyy-mm-ddThh:mm:ssZ
        time_reference = nc.createVariable(
            "time_reference", "S1", ('string_length'))
        tstr = self.time_reference.strftime("%Y-%m-%dT%H:%M:%SZ")
        datain = np.array(tstr, dtype="S20")
        time_reference[:] = stringtochar(datain)
        time_reference.long_name = "time_reference"
        time_reference.units = "unitless"

    def write_coordinate_variables(self):
        nc = self.nc

        # Coordinate variable for time.
        # Time at center of each ray, in fractional seconds since time_coverage_start.
        time = nc.createVariable("time",
                                 dtype("double").char,
                                 ("time"))
        time[:] = np.array(self.time)
        time.long_name = "time_in_seconds_since_volume_start"
        time.units = f"seconds since {self.time_reference.strftime('%Y-%m-%dT%H:%M:%SZ')}"
        time.calendar = "gregorian"

        # Coordinate variable for range. Range to center of each bin.
        radar_range = nc.createVariable("range",
                                        dtype("float32").char,
                                        ("range"))
        radar_range[:] = self.radar_range.astype("float32")
        radar_range.standard_name = "projection_range_coordinate"
        radar_range.long_name = "range_to_measurement_volume"
        radar_range.units = "meters"
        radar_range.spacing_is_constant = "true"
        radar_range.meters_to_center_of_first_gate = radar_range[0]
        radar_range.meters_between_gates = radar_range[1] - radar_range[0]
        radar_range.axis = "radial_range_coordinate"

    def write_location_variables(self):
        nc = self.nc

        # Latitude of instrument.
        # For a stationary platform, this is a scalar.
        # For a moving platform, this is a vector.
        latitude = nc.createVariable("latitude", dtype('double').char)
        latitude[:] = self.latitude
        latitude.long_name = "latitude"
        latitude.units = "degrees_north"

        # Longitude of instrument.
        # For a stationary platform, this is a scalar.
        # For a moving platform, this is a vector.
        longitude = nc.createVariable("longitude", dtype('double').char)
        longitude[:] = self.longitude
        longitude.long_name = "longitude"
        longitude.units = "degrees_east"

        # Altitude of instrument above mean sea level.
        # For a stationary platform, this is a scalar.
        # For a moving platform, this is a vector.
        altitude = nc.createVariable("altitude", dtype('double').char)
        altitude[:] = self.altitude
        altitude.long_name = "altitude"
        altitude.units = "meters"

    def write_sweep_variables(self):
        nc = self.nc

        # The number of the sweep, in the volume scan. 0-based.
        sweep_number = nc.createVariable(
            "sweep_number", dtype("int32").char, ("sweep"))
        sweep_number[:] = np.array(self.sweep_number, dtype="int32")
        sweep_number.long_name = "sweep_index_number_0_based"
        sweep_number.units = "unitless"

        # Options are: "sector", "coplane", rhi", "vertical_pointing", "idle", "azimuth_surveillance", "elevation_surveillance", "sunscan", "pointing", "manual_ppi", "manual_rhi"
        sweep_mode = nc.createVariable(
            "sweep_mode", "S1", ("sweep", "string_length"))
        datain = np.array(self.sweep_mode, dtype='S22')
        sweep_mode[:] = stringtochar(datain)
        sweep_mode.long_name = "scan_mode_for_sweep"
        sweep_mode.unit = "unitless"

        # Target angle for the sweep. elevation in most modes. azimuth in RHI mode.
        fixed_angle = nc.createVariable(
            "fixed_angle", dtype("float32").char, ("sweep"))
        fixed_angle[:] = np.array(self.fixed_angle, dtype="float32")
        fixed_angle.long_name = "target_fixed_angle"
        fixed_angle.units = "degrees"

        # Index of first ray in sweep, relative to start of volume. 0-based
        sweep_start_ray_index = nc.createVariable(
            "sweep_start_ray_index", dtype("int32").char, ("sweep"))
        sweep_start_ray_index[:] = np.array(
            self.sweep_start_ray_index, dtype="int32")
        sweep_start_ray_index.long_name = "index_of_first_ray_in_sweep"
        sweep_start_ray_index.units = "unitless"

        # Index of last ray in sweep, relative to start of volume. 0-based
        sweep_end_ray_index = nc.createVariable(
            "sweep_end_ray_index", dtype("int32").char, ("sweep"))
        sweep_end_ray_index[:] = np.array(
            self.sweep_end_ray_index, dtype="int32")
        sweep_end_ray_index.long_name = "index_of_last_ray_in_sweep"
        sweep_end_ray_index.units = "unitless"

    def write_sensor_pointing_variables(self):
        nc = self.nc

        # Azimuth of antenna, relative to true north.
        azimuth = nc.createVariable("azimuth", dtype("float32").char, ("time"))
        azimuth[:] = np.array(self.azimuth, dtype="float32")
        azimuth.standard_name = "ray_azimuth_angle"
        azimuth.long_name = "azimuth_angle_from_true_north"
        azimuth.units = "degrees"
        azimuth.axis = "radial_azimuth_coordinate"

        # Elevation of antenna, relative to the horizontal plane.
        elevation = nc.createVariable(
            "elevation", dtype("float32").char, ("time"))
        elevation[:] = np.array(self.elevation, dtype="float32")
        elevation.standard_name = "ray_elevation_angle"
        elevation.long_name = "elevation_angle_from_horizontal_plane"
        elevation.units = "degrees"
        elevation.axis = "radial_elevation_coordinate"

    def write_moments_field_data_variables(self):
        nc = self.nc
        if self.parameter_number in [0, 230]:
            short_name = "WIDTH"
            standard_name = "doppler_spectrum_width"
            units = "m/s"
        elif self.parameter_number == 1:
            short_name = "DBZ"
            standard_name = "equivalent_reflectivity_factor"
            units = "dBZ"
        elif self.parameter_number in [2, 228]:
            short_name = "VEL"
            standard_name = "radial_velocity_of_scatterers_away_from_instrument"
            units = "m/s"
        elif self.parameter_number == 194:
            short_name = "RRR" # in JMA RFI
            standard_name = "radar_estimated_rain_rate"
            units = "mm/h"
        elif self.parameter_number == 195:
            short_name = "DBZH"
            standard_name = "equivalent_reflectivity_factor_h"
            units = "dBZ"
        elif self.parameter_number == 196:
            short_name = "DBZV"
            standard_name = "equivalent_reflectivity_factor_v"
            units = "dBZ"
        elif self.parameter_number == 197:
            short_name = "ZDR"
            standard_name = "log_differential_reflectivity_hv"
            units = "dB"
        elif self.parameter_number == 198:
            short_name = "PSIDP"
            standard_name = "radar_total_differential_phase_hv"
            units = "degrees"
        elif self.parameter_number == 199:
            short_name = "RHOHV"
            standard_name = "cross_correlation_ratio_hv"
            units = "unitless"
        elif self.parameter_number == 201:
            short_name = "PHIDP"
            standard_name = "differential_phase_hv"
            units = "degrees"
        elif self.parameter_number == 202:
            short_name = "KDP"
            standard_name = "specific_differential_phase_hv"
            units = "degrees/km"
        elif self.parameter_number in [206, 215]:
            short_name = "QCI"
            standard_name = "quality_control_information"
            units = "unitless"
        else:
            raise GRIBDecodeError(f"未対応のパラメータ番号{self.parameter_number}です")
        if self.parameter_number in [206, 215]:
            variable = nc.createVariable(short_name,
                                         dtype("uint8").char,
                                         ("time", "range"))
        else:
            variable = nc.createVariable(short_name,
                                         dtype("float32").char,
                                         ("time", "range"),
                                         fill_value=self._FillValueF32)
        variable[:] = self.data
        variable.standard_name = standard_name
        variable.units = units

    def write_instrument_parameters(self):
        nc = self.nc

        # List of operating frequencies, in Hertz. In most cases, only a single frequency is used.
        frequency = nc.createVariable(
            "frequency", dtype("float32").char, ("frequency"))
        frequency[:] = np.array([self.frequency], dtype="float32")
        frequency.long_name = "radiation_frequency"
        frequency.units = "s-1"


def read_float(ary, i0, i1, offset):
    bl = ary[offset + i0 - 1:offset + i1]
    ba = bytearray(bl)
    return struct.unpack(">f", ba)[0]


def read_int(ary, i0, i1, offset):
    return int.from_bytes(ary[offset + i0 - 1:offset + i1], "big")


def read_int_sgn(ary, i0, i1, offset):
    l = 8 * (i1 - i0 + 1)
    result = read_int(ary, i0, i1, offset)
    if result & 1 << (l - 1) > 0:
        result = -(result & ~(1 << (l - 1)))
    return result


class GRIBDecodeError(Exception):
    pass


if __name__ == "__main__":
    main()