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ENH: optional rectangular window dims for velocity texture analysis a…
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…nd bug fixes to the load_kazr method (#1446)

* FIX: change deprecated np.str in arm_vpt to str

* Update default wind_size in calculate_velocity_texture from 4 to 3
Using an odd number prevents single index offsets in placement in
case of an even size

* ADD: optional rectangular window dims for velocity texture analysis.
Also, modify the default window size to 3 instead of the previous
value of 4 (even number resulting in a potential offset).

* FIX: nyquist velocity dtype in radar obj loaded with read_kazr

* pep8

* line reformatting per black

* TST: unit tests for rectangular texture window

* FIX: Add in linting fixes

---------

Co-authored-by: mgrover1 <[email protected]>
isilber and mgrover1 authored Aug 17, 2023

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MaferMazu María Fernanda Magallanes
1 parent 6d48f1b commit 70c314c
Showing 4 changed files with 41 additions and 13 deletions.
2 changes: 1 addition & 1 deletion pyart/aux_io/arm_vpt.py
Original file line number Diff line number Diff line change
@@ -176,7 +176,7 @@ def read_kazr(

v_nq = float(ncobj.nyquist_velocity.split()[0])
nyquist_velocity = filemetadata("nyquist_velocity")
nyquist_velocity["data"] = (v_nq * np.ones(ncvars["time"].size, dtype=np.float32),)
nyquist_velocity["data"] = v_nq * np.ones(ncvars["time"].size, dtype=np.float32)
samples = int(ncobj.num_spectral_averages)
n_samples = filemetadata("n_samples")
n_samples["data"] = samples * np.ones(ncvars["time"].size, dtype=np.int32)
18 changes: 11 additions & 7 deletions pyart/retrieve/simple_moment_calculations.py
Original file line number Diff line number Diff line change
@@ -240,7 +240,7 @@ def compute_cdr(radar, rhohv_field=None, zdr_field=None, cdr_field=None):


def calculate_velocity_texture(
radar, vel_field=None, wind_size=4, nyq=None, check_nyq_uniform=True
radar, vel_field=None, wind_size=3, nyq=None, check_nyq_uniform=True
):
"""
Derive the texture of the velocity field.
@@ -252,9 +252,11 @@ def calculate_velocity_texture(
vel_field : str, optional
Name of the velocity field. A value of None will force Py-ART to
automatically determine the name of the velocity field.
wind_size : int, optional
The size of the window to calculate texture from. The window is
defined to be a square of size wind_size by wind_size.
wind_size : int or 2-element tuple, optional
The size of the window to calculate texture from.
If an integer, the window is defined to be a square of size wind_size
by wind_size. If tuple, defines the m x n dimensions of the filter
window.
nyq : float, optional
The nyquist velocity of the radar. A value of None will force Py-ART
to try and determine this automatically.
@@ -274,6 +276,10 @@ def calculate_velocity_texture(
if vel_field is None:
vel_field = get_field_name("velocity")

# Set wind_size as a tuple if input is int
if isinstance(wind_size, int):
wind_size = (wind_size, wind_size)

# Allocate memory for texture field
vel_texture = np.zeros(radar.fields[vel_field]["data"].shape)

@@ -300,7 +306,5 @@ def calculate_velocity_texture(
vel_texture_field["standard_name"] = (
"texture_of_radial_velocity" + "_of_scatters_away_from_instrument"
)
vel_texture_field["data"] = ndimage.median_filter(
vel_texture, size=(wind_size, wind_size)
)
vel_texture_field["data"] = ndimage.median_filter(vel_texture, size=wind_size)
return vel_texture_field
16 changes: 11 additions & 5 deletions pyart/util/sigmath.py
Original file line number Diff line number Diff line change
@@ -18,9 +18,11 @@ def angular_texture_2d(image, N, interval):
image : 2D array of floats
The array containing the velocities in which to calculate
texture from.
N : int
This is the window size for calculating texture. The texture will be
calculated from an N by N window centered around the gate.
N : int or 2-element tuple
If int, this is the window size for calculating texture. The
texture will be calculated from an N by N window centered
around the gate. If tuple N defines the m x n dimensions of
the window centered around the gate.
interval : float
The absolute value of the maximum velocity. In conversion to
radial coordinates, pi will be defined to be interval
@@ -33,6 +35,10 @@ def angular_texture_2d(image, N, interval):
Texture of the radial velocity field.
"""
# Set N as a tuple if input is int
if isinstance(N, int):
N = (N, N)

# transform distribution from original interval to [-pi, pi]
interval_max = interval
interval_min = -interval
@@ -45,10 +51,10 @@ def angular_texture_2d(image, N, interval):
y = np.sin(im)

# Calculate convolution
kernel = np.ones((N, N))
kernel = np.ones(N)
xs = signal.convolve2d(x, kernel, mode="same", boundary="symm")
ys = signal.convolve2d(y, kernel, mode="same", boundary="symm")
ns = N**2
ns = np.prod(N)

# Calculate norm over specified window
xmean = xs / ns
18 changes: 18 additions & 0 deletions tests/retrieve/test_simple_moment_calculations.py
Original file line number Diff line number Diff line change
@@ -75,6 +75,10 @@ def test_calculate_velocity_texture():
radar, vel_field, wind_size=4, nyq=10
)
assert np.all(texture_field["data"] == 0)
texture_field = pyart.retrieve.calculate_velocity_texture(
radar, vel_field, wind_size=(5, 7), nyq=10
)
assert np.all(texture_field["data"] == 0)

# Test none parameters
radar2 = pyart.io.read(pyart.testing.NEXRAD_ARCHIVE_MSG31_FILE)
@@ -86,3 +90,17 @@ def test_calculate_velocity_texture():
[0.000363, 0.000363, 0.000363, 0.000363, 0.000363],
atol=1e-03,
)

# Test rectangular filter option consistency with default scalar
radar2 = pyart.io.read(pyart.testing.NEXRAD_ARCHIVE_MSG31_FILE)
radar2.fields["velocity"]["data"] = (
np.random.normal(scale=0.01, size=radar2.fields["velocity"]["data"].shape)
* radar2.fields["velocity"]["data"]
) # Generate value variability
texture_field2 = pyart.retrieve.calculate_velocity_texture(
radar2, vel_field="velocity", wind_size=3, nyq=10.0
)
texture_field3 = pyart.retrieve.calculate_velocity_texture(
radar2, vel_field="velocity", wind_size=(3, 3), nyq=10.0
)
assert_allclose(texture_field2["data"], texture_field3["data"], atol=1e-10)

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