"""
Front end to the University of Washington 4DD code for Doppler dealiasing.
"""
import numpy as np
from ..config import get_field_name, get_fillvalue, get_metadata
try:
from ..io import _rsl_interface
from . import _fourdd_interface
_FOURDD_AVAILABLE = True
except ImportError:
_FOURDD_AVAILABLE = False
from ..exceptions import MissingOptionalDependency
from ._common_dealias import _parse_gatefilter, _set_limits
[docs]def dealias_fourdd(
radar,
last_radar=None,
sonde_profile=None,
gatefilter=False,
filt=1,
rsl_badval=131072.0,
keep_original=False,
set_limits=True,
vel_field=None,
corr_vel_field=None,
last_vel_field=None,
debug=False,
max_shear=0.05,
sign=1,
**kwargs
):
"""
Dealias Doppler velocities using the 4DD algorithm.
Dealias the Doppler velocities field using the University of Washington
4DD algorithm utilizing information from a previous volume scan and/or
sounding data. Either last_radar or sonde_profile must be provided.
For best results provide both a previous volume scan and sounding data.
Radar and last_radar must contain the same number of rays per sweep.
Additional arguments are passed to
:py:func:`_fourdd_interface.fourdd_dealias`.
These can be used to fine tune the behavior of the FourDD algorithm.
See the documentation of Other Parameters for details. For the default
values of these parameters see the documentation of
:py:func:`_fourdd_interface.fourdd_dealias`.
Parameters
----------
radar : Radar
Radar object to use for dealiasing. Must have a Nyquist defined in
the instrument_parameters attribute and have a
reflectivity_horizontal and mean_doppler_velocity fields.
last_radar : Radar, optional
The previous radar volume, which has been successfully
dealiased. Using a previous volume as an initial condition can
greatly improve the dealiasing, and represents the final dimension
in the 4DD algorithm.
sonde_profile : HorizontalWindProfile, optional
Profile of horizontal winds from a sonding used for the initial
condition of the dealiasing.
Other Parameters
----------------
gatefilter : GateFilter, optional.
A GateFilter instance which specifies which gates should be
ignored when performing velocity dealiasing. A value of None will
create this filter from the radar moments using any additional
arguments by passing them to :py:func:`moment_based_gate_filter`. The
default value assumes all gates are valid.
filt : int, optional
Flag controlling Bergen and Albers filter, 1 = yes, 0 = no.
rsl_badval : float, optional
Value which represents a bad value in RSL.
keep_original : bool, optional
True to keep original doppler velocity values when the dealiasing
procedure fails, otherwise these gates will be masked. NaN values
are still masked.
set_limits : bool, optional
True to set valid_min and valid_max elements in the returned
dictionary. False will not set these dictionary elements.
vel_field : str, optional
Field in radar to use as the Doppler velocities during dealiasing.
None will use the default field name from the Py-ART configuration
file.
corr_vel_field : str, optional
Name to use for the dealiased Doppler velocity field metadata. None
will use the default field name from the Py-ART configuration file.
last_vel_field : str, optional
Name to use for the dealiased Doppler velocity field metadata in
last_radar. None will use the corr_vel_field name.
maxshear : float, optional
Maximum vertical shear which will be incorporated into the created
volume from the sounding data. Parameter not used when no
sounding data is provided.
sign : int, optional
Sign convention which the radial velocities in the volume created
from the sounding data will will. This should match the convention
used in the radar data. A value of 1 represents when positive values
velocities are towards the radar, -1 represents when negative
velocities are towards the radar.
compthresh : float, optional
Fraction of the Nyquist velocity to use as a threshold when performing
continuity (initial) dealiasing. Velocities differences above this
threshold will not be marked as gate from which to begin unfolding
during spatial dealiasing.
compthresh2 : float, optional
The same as compthresh but the value used during the second pass of
dealiasing. This second pass is only performed in both a sounding
and last volume are provided.
thresh : float, optional
Fraction of the Nyquist velocity to use as a threshold when performing
spatial dealiasing. Horizontally adjacent gates with velocities above
this threshold will count against assigning the gate in question the
velocity value being tested.
ckval : float, optional
When the absolute value of the velocities are below this value they
will not be marked as gates from which to begin unfolding during
spatial dealiasing.
stdthresh : float, optional
Fraction of the Nyquist velocity to use as a standard deviation
threshold in the window dealiasing portion of the algorithm.
epsilon : float, optional
Difference used when comparing a value to missing value, changing this
from the default is not recommended.
maxcount : int, optional
Maximum allowed number of fold allowed when unfolding velocities.
pass2 : int, optional
Controls weather unfolded gates should be removed (a value of 0)
or retained for unfolding during the second pass (a value of 1) when
both a sounding volume and last volume are provided.
rm : int, optional
Determines what should be done with gates that are left unfolded
after the first pass of dealiasing. A value of 1 will remove these
gates, a value of 0 sets these gates to their initial velocity. If
both a sounding volume and last volume are provided this parameter is
ignored.
proximity : int, optional
Number of gates and rays to include of either side of the current gate
during window dealiasing. This value may be doubled in cases where
a standard sized window does not capture a sufficient number of
good valued gates.
mingood : int, optional
Number of good valued gates required within the window before the
current gate will be unfolded.
ba_mincount : int, optional
Number of neighbors required during Bergen and Albers filter for
a given gate to be included, must be between 1 and 8, 5 recommended.
ba_edgecount : int, optional
Same as ba_mincount but used at ray edges, must be between 1 and 5,
3 recommended.
debug : bool, optional
Set True to return RSL Volume objects for debugging:
usuccess, radialVelVolume, lastVelVolume, unfoldedVolume, sondVolume
Returns
-------
vr_corr : dict
Field dictionary containing dealiased Doppler velocities. Dealiased
array is stored under the 'data' key.
Notes
-----
Due to limitations in the C code do not call with sounding arrays over
999 elements long.
References
----------
C. N. James and R. A Houze Jr, A Real-Time Four-Dimensional Doppler
Dealising Scheme, Journal of Atmospheric and Oceanic Technology, 2001, 18,
1674.
"""
# check that FourDD is available (requires TRMM RSL)
if not _FOURDD_AVAILABLE:
raise MissingOptionalDependency(
"Py-ART must be build with support for TRMM RSL to use"
+ " the dealias_fourdd function."
)
# verify that sounding data or last_volume is provided
if (sonde_profile is None) and (last_radar is None):
raise ValueError("sonde_profile or last_radar must be provided.")
# parse the field parameters
if vel_field is None:
vel_field = get_field_name("velocity")
if corr_vel_field is None:
corr_vel_field = get_field_name("corrected_velocity")
if last_vel_field is None:
last_vel_field = get_field_name("corrected_velocity")
# get fill value
fill_value = get_fillvalue()
# parse radar gate filter
gatefilter = _parse_gatefilter(gatefilter, radar, **kwargs)
excluded = gatefilter.gate_excluded
# create RSL volumes containing the doppler velocity and
# doppler velocity in the last radar (if provided)
vel_volume = _create_rsl_volume(radar, vel_field, 1, rsl_badval, excluded)
if last_radar is not None:
last_vel_volume = _create_rsl_volume(last_radar, last_vel_field, 1, rsl_badval)
else:
last_vel_volume = None
# create an RslVolume containing the sounding data if it available
if sonde_profile is not None:
# convert the sounding data to 1D float32 arrays
height = np.ascontiguousarray(sonde_profile.height, dtype=np.float32)
speed = np.ascontiguousarray(sonde_profile.speed, dtype=np.float32)
wdir = np.ascontiguousarray(sonde_profile.direction, dtype=np.float32)
if len(height) > 999:
raise ValueError("Too many sounding heights, maximum is 999")
success, sound_volume = _fourdd_interface.create_soundvolume(
vel_volume, height, speed, wdir, sign, max_shear
)
if success == 0:
raise ValueError("Error when loading sounding data.")
else:
sound_volume = None
# perform dealiasing
if debug:
return _fourdd_interface.fourdd_dealias(
vel_volume, last_vel_volume, sound_volume, filt, debug=True, **kwargs
)
_, data = _fourdd_interface.fourdd_dealias(
vel_volume, last_vel_volume, sound_volume, filt, debug=False, **kwargs
)
# prepare data for output, set bad values and mask data
is_bad_data = np.logical_or(np.isnan(data), data == rsl_badval)
if keep_original:
vel_array = radar.fields[vel_field]["data"]
data = np.where(is_bad_data, vel_array, data)
else:
data[is_bad_data] = fill_value
data = np.ma.masked_equal(data, fill_value)
# return field dictionary containing dealiased Doppler velocities
vr_corr = get_metadata(corr_vel_field)
vr_corr["data"] = data
vr_corr["_FillValue"] = data.fill_value
if set_limits:
nyquist_vel = radar.instrument_parameters["nyquist_velocity"]["data"]
_set_limits(data, nyquist_vel, vr_corr)
return vr_corr
def _create_rsl_volume(radar, field_name, vol_num, rsl_badval, excluded=None):
"""
Create a RSLVolume containing data from a field in radar.
"""
fill_value = get_fillvalue()
fdata = np.copy(radar.fields[field_name]["data"]).astype(np.float32)
fdata = np.ma.filled(fdata, fill_value)
is_bad = np.logical_or(fdata == fill_value, np.isnan(fdata))
fdata[is_bad] = rsl_badval
if excluded is not None:
fdata[excluded] = rsl_badval
rays_per_sweep = (
radar.sweep_end_ray_index["data"] - radar.sweep_start_ray_index["data"] + 1
)
rays_per_sweep = rays_per_sweep.astype(np.int32)
rsl_volume = _rsl_interface.create_volume(fdata, rays_per_sweep, vol_num)
_rsl_interface._label_volume(rsl_volume, radar)
return rsl_volume