Source code for pyart.aux_io.rxm25

"""
Routines for Ridgeline Instruments RXM-25 formatted NetCDF files.

"""

import datetime

try:
    import pytz

    _PYTZ_AVAILABLE = True
except ImportError:
    _PYTZ_AVAILABLE = False

import netCDF4
import numpy as np

import pyart

from ..config import get_metadata
from ..exceptions import MissingOptionalDependency
from ..testing import make_empty_ppi_radar


def read_rxm25(filename, cfradial_outfile=None, heading=None):
    """
    Read in Ridgeline Instruments RXM-25 formatted NetCDF data.

    Parameters
    ----------
    filename : str
        Name of Ridgeline Instruments (RLI) RXM-25 formatted NetCDF file
        from which to read data.
    cfradial_outfile : str, optional
        If file is to be converted to CF-Radial format, specify the output
        filename here.
    heading : float, optional
        If a heading offset exists, enter it here (in degrees).

    Returns
    -------
    radar : Radar
        Radar object.

    """
    if not _PYTZ_AVAILABLE:
        raise MissingOptionalDependency(
            "Pytz is required to use read_rxm25 but is " + "not installed"
        )

    data = netCDF4.Dataset(filename, "r")

    ngates = data.dimensions["Gate"].size
    rays_per_sweep = data.dimensions["Radial"].size
    radar = make_empty_ppi_radar(ngates, rays_per_sweep, 1)

    # Time needs to be converted from nss1970 to nss1989 and added to
    # Radar object.
    nineteen89 = datetime.datetime(1989, 1, 1, 0, 0, 1, tzinfo=pytz.utc)
    baseTime = np.array(
        [
            datetime.datetime.fromtimestamp(t, tz=pytz.UTC)
            for t in data.variables["Time"][:]
        ]
    )
    radar.time["data"] = np.array([t.total_seconds() for t in baseTime - nineteen89])

    if heading is not None:
        radar.heading = heading
        radar.azimuth["data"] = np.mod(data["Azimuth"][:] - radar.heading, 360.0)
    else:
        radar.azimuth["data"] = data["Azimuth"][:]

    radar.longitude["data"] = np.array([data.Longitude], dtype="float64")
    radar.latitude["data"] = np.array([data.Latitude], dtype="float64")
    radar.elevation["data"] = data["Elevation"][:]
    radar.altitude["data"] = np.array([data.Height], dtype="float64")

    fixed_agl_data = np.empty((1,), dtype="float32")
    fixed_agl_data[:] = np.mean(radar.elevation["data"][:rays_per_sweep])

    radar.fixed_angle["data"] = fixed_agl_data

    radar.range["data"] = np.linspace(
        data["StartRange"][0] / 1000,
        (ngates - 1) * data["GateWidth"][0] / 1000 + data["StartRange"][0] / 1000,
        ngates,
    )

    ref = data["Reflectivity"][:]
    norm_pow = data["NormalizedCoherentPower"][:]
    spec_w = data["SpectralWidth"][:]
    vel = data["Velocity"][:]
    corr_ref = data["CorrectedReflectivity"][:]
    diff_ref = data["DifferentialReflectivity"][:]
    diff_phase = data["DifferentialPhase"][:]
    spec_phase = data["SpecificPhase"][:]
    corr_diff_ref = data["CorrectedDifferentialReflectivity"][:]
    sig_noise = data["SignalToNoiseRatio"][:]
    rain_rate = data["RainfallRate"][:]
    cross_ra = data["CrossPolCorrelation"][:]

    fields = {
        "reflectivity": get_metadata("reflectivity"),
        "normalized_coherent_power": get_metadata("normalized_coherent_power"),
        "spectral_width": get_metadata("spectral_width"),
        "velocity": get_metadata("velocity"),
        "corrected_reflectivity": get_metadata("correct_reflectivity"),
        "differential_reflectivity": get_metadata("differential_reflectivity"),
        "differential_phase": get_metadata("differential_phase"),
        "specific_differential_phase": get_metadata("specific_differential_phase"),
        "corrected_differential_reflectivity": get_metadata(
            "corrected_differential_reflectivity"
        ),
        "signal_to_noise_ratio": get_metadata("signal_to_noise_ratio"),
        "rain_rate": get_metadata("rain_rate"),
        "cross_correlation_ratio": get_metadata("cross_correlation_ratio"),
    }

    radar.fields = fields
    radar.fields["reflectivity"]["data"] = ref
    radar.fields["normalized_coherent_power"]["data"] = norm_pow
    radar.fields["spectral_width"]["data"] = spec_w
    radar.fields["velocity"]["data"] = vel
    radar.fields["corrected_reflectivity"]["data"] = corr_ref
    radar.fields["differential_reflectivity"]["data"] = diff_ref
    radar.fields["differential_phase"]["data"] = diff_phase
    radar.fields["specific_differential_phase"]["data"] = spec_phase
    radar.fields["corrected_differential_reflectivity"]["data"] = corr_diff_ref
    radar.fields["signal_to_noise_ratio"]["data"] = sig_noise
    radar.fields["rain_rate"]["data"] = rain_rate
    radar.fields["cross_correlation_ratio"]["data"] = cross_ra

    radar.metadata["instrument_name"] = "RXM-25"

    if cfradial_outfile is not None:
        pyart.io.write_cfradial(cfradial_outfile, radar, arm_time_variables=True)

    return radar