xarray Rainbow5 backend

In this example, we read Rainbow5 data files using the wradlib rainbow xarray backend.

[1]:
import glob
import gzip
import io
import wradlib as wrl
import warnings

warnings.filterwarnings("ignore")
import matplotlib.pyplot as pl
import numpy as np
import xarray as xr

try:
    get_ipython().run_line_magic("matplotlib inline")
except:
    pl.ion()
/home/runner/micromamba-root/envs/wradlib-notebooks/lib/python3.11/site-packages/tqdm/auto.py:22: TqdmWarning: IProgress not found. Please update jupyter and ipywidgets. See https://ipywidgets.readthedocs.io/en/stable/user_install.html
  from .autonotebook import tqdm as notebook_tqdm

Load Rainbow5 Volume Data

[2]:
fpath = "rainbow/2013051000000600dBZ.vol"
f = wrl.util.get_wradlib_data_file(fpath)
vol = wrl.io.open_rainbow_dataset(f, reindex_angle=False)
Downloading file 'rainbow/2013051000000600dBZ.vol' from 'https://github.com/wradlib/wradlib-data/raw/pooch/data/rainbow/2013051000000600dBZ.vol' to '/home/runner/work/wradlib-notebooks/wradlib-notebooks/wradlib-data'.

Inspect RadarVolume

[3]:
display(vol)
<wradlib.RadarVolume>
Dimension(s): (sweep: 14)
Elevation(s): (0.6, 1.4, 2.4, 3.5, 4.8, 6.3, 8.0, 9.9, 12.2, 14.8, 17.9, 21.3, 25.4, 30.0)

Inspect root group

The sweep dimension contains the number of scans in this radar volume. Further the dataset consists of variables (location coordinates, time_coverage) and attributes (Conventions, metadata).

[4]:
vol.root
[4]:
<xarray.Dataset>
Dimensions:              (sweep: 14)
Dimensions without coordinates: sweep
Data variables:
    volume_number        int64 0
    platform_type        <U5 'fixed'
    instrument_type      <U5 'radar'
    primary_axis         <U6 'axis_z'
    time_coverage_start  <U20 '2013-05-10T00:00:06Z'
    time_coverage_end    <U20 '2013-05-10 00:03:15Z'
    latitude             float64 ...
    longitude            float64 ...
    altitude             float64 ...
    sweep_group_name     (sweep) <U8 'sweep_0' 'sweep_1' ... 'sweep_13'
    sweep_fixed_angle    (sweep) float64 0.6 1.4 2.4 3.5 ... 17.9 21.3 25.4 30.0
Attributes:
    version:          None
    title:            None
    institution:      None
    references:       None
    source:           None
    history:          None
    comment:          im/exported using wradlib
    instrument_name:  None
    fixed_angle:      0.6

Inspect sweep group(s)

The sweep-groups can be accessed via their respective keys. The dimensions consist of range and time with added coordinates azimuth, elevation, range and time. There will be variables like radar moments (DBZH etc.) and sweep-dependend metadata (like fixed_angle, sweep_mode etc.).

[5]:
display(vol[0])
<xarray.Dataset>
Dimensions:            (azimuth: 361, range: 400)
Coordinates:
  * azimuth            (azimuth) float64 0.5492 1.505 2.549 ... 358.5 359.5
    elevation          (azimuth) float64 ...
  * range              (range) float32 125.0 375.0 625.0 ... 9.962e+04 9.988e+04
    rtime              (azimuth) datetime64[ns] 2013-05-10T00:00:15.530303500...
    sweep_mode         <U20 ...
    longitude          float64 ...
    latitude           float64 ...
    altitude           float64 ...
    time               datetime64[ns] 2013-05-10T00:00:06.015151500
Data variables:
    DBZH               (azimuth, range) float32 ...
    sweep_number       int64 ...
    prt_mode           <U7 ...
    follow_mode        <U7 ...
    sweep_fixed_angle  float64 0.6
Attributes:
    fixed_angle:  0.6

Goereferencing

[6]:
swp = vol[0].copy().pipe(wrl.georef.georeference_dataset)

Plotting

[7]:
swp.DBZH.plot.pcolormesh(x="x", y="y")
pl.gca().set_aspect("equal")
../../_images/notebooks_fileio_wradlib_rainbow_backend_14_0.png
[8]:
fig = pl.figure(figsize=(10, 10))
swp.DBZH.wradlib.plot_ppi(proj="cg", fig=fig)
[8]:
<matplotlib.collections.QuadMesh at 0x7f05f2c52f50>
../../_images/notebooks_fileio_wradlib_rainbow_backend_15_1.png
[9]:
import cartopy
import cartopy.crs as ccrs
import cartopy.feature as cfeature

map_trans = ccrs.AzimuthalEquidistant(
    central_latitude=swp.latitude.values, central_longitude=swp.longitude.values
)
[10]:
map_proj = ccrs.AzimuthalEquidistant(
    central_latitude=swp.latitude.values, central_longitude=swp.longitude.values
)
pm = swp.DBZH.wradlib.plot_ppi(proj=map_proj)
ax = pl.gca()
ax.gridlines(crs=map_proj)
print(ax)
< GeoAxes: +proj=aeqd +ellps=WGS84 +lon_0=6.379967 +lat_0=50.856633 +x_0=0.0 +y_0=0.0 +no_defs +type=crs >
../../_images/notebooks_fileio_wradlib_rainbow_backend_17_1.png
[11]:
map_proj = ccrs.Mercator(central_longitude=swp.longitude.values)
fig = pl.figure(figsize=(10, 8))
ax = fig.add_subplot(111, projection=map_proj)
pm = swp.DBZH.wradlib.plot_ppi(ax=ax)
ax.gridlines(draw_labels=True)
[11]:
<cartopy.mpl.gridliner.Gridliner at 0x7f05f2bc7290>
../../_images/notebooks_fileio_wradlib_rainbow_backend_18_1.png
[12]:
import cartopy.feature as cfeature


def plot_borders(ax):
    borders = cfeature.NaturalEarthFeature(
        category="physical", name="coastline", scale="10m", facecolor="none"
    )
    ax.add_feature(borders, edgecolor="black", lw=2, zorder=4)


map_proj = ccrs.Mercator(central_longitude=swp.longitude.values)
fig = pl.figure(figsize=(10, 8))
ax = fig.add_subplot(111, projection=map_proj)

DBZH = swp.DBZH
pm = DBZH.where(DBZH > 0).wradlib.plot_ppi(ax=ax)
plot_borders(ax)
ax.gridlines(draw_labels=True)
[12]:
<cartopy.mpl.gridliner.Gridliner at 0x7f05f2be48d0>
../../_images/notebooks_fileio_wradlib_rainbow_backend_19_1.png
[13]:
import matplotlib.path as mpath

theta = np.linspace(0, 2 * np.pi, 100)
center, radius = [0.5, 0.5], 0.5
verts = np.vstack([np.sin(theta), np.cos(theta)]).T
circle = mpath.Path(verts * radius + center)

map_proj = ccrs.AzimuthalEquidistant(
    central_latitude=swp.latitude.values,
    central_longitude=swp.longitude.values,
)
fig = pl.figure(figsize=(10, 8))
ax = fig.add_subplot(111, projection=map_proj)
ax.set_boundary(circle, transform=ax.transAxes)

pm = swp.DBZH.wradlib.plot_ppi(proj=map_proj, ax=ax)
ax = pl.gca()
ax.gridlines(crs=map_proj)
[13]:
<cartopy.mpl.gridliner.Gridliner at 0x7f05ea9e7dd0>
../../_images/notebooks_fileio_wradlib_rainbow_backend_20_1.png
[14]:
fig = pl.figure(figsize=(10, 8))
proj = ccrs.AzimuthalEquidistant(
    central_latitude=swp.latitude.values, central_longitude=swp.longitude.values
)
ax = fig.add_subplot(111, projection=proj)
pm = swp.DBZH.wradlib.plot_ppi(ax=ax)
ax.gridlines()
[14]:
<cartopy.mpl.gridliner.Gridliner at 0x7f05ea94fb10>
../../_images/notebooks_fileio_wradlib_rainbow_backend_21_1.png
[15]:
swp.DBZH.wradlib.plot_ppi()
[15]:
<matplotlib.collections.QuadMesh at 0x7f05e867fc50>
../../_images/notebooks_fileio_wradlib_rainbow_backend_22_1.png

Inspect radar moments

The DataArrays can be accessed by key or by attribute. Each DataArray has dimensions and coordinates of it’s parent dataset.

[16]:
display(swp.DBZH)
<xarray.DataArray 'DBZH' (azimuth: 361, range: 400)>
array([[24.5, 21. ,  1.5, ...,  nan,  nan,  nan],
       [25.5, 22.5,  0. , ...,  nan,  nan,  nan],
       [25.5, 22. , -3. , ...,  nan,  nan,  nan],
       ...,
       [24. , 30. , -5.5, ...,  nan,  nan,  nan],
       [25.5, 29.5, -5.5, ...,  nan,  nan,  nan],
       [24.5, 23. , 22. , ...,  nan,  nan,  nan]], dtype=float32)
Coordinates: (12/15)
  * azimuth     (azimuth) float64 0.5492 1.505 2.549 3.516 ... 357.5 358.5 359.5
    elevation   (azimuth) float64 0.6 0.6 0.6 0.6 0.6 ... 0.6 0.6 0.6 0.6 0.6
  * range       (range) float32 125.0 375.0 625.0 ... 9.962e+04 9.988e+04
    rtime       (azimuth) datetime64[ns] 2013-05-10T00:00:15.530303500 ... 20...
    sweep_mode  <U20 'azimuth_surveillance'
    longitude   float64 6.38
    ...          ...
    x           (azimuth, range) float64 1.198 3.594 5.99 ... -859.6 -861.8
    y           (azimuth, range) float64 125.0 375.0 ... 9.96e+04 9.985e+04
    z           (azimuth, range) float64 118.0 120.6 ... 1.744e+03 1.75e+03
    gr          (azimuth, range) float64 124.8 374.7 ... 9.96e+04 9.985e+04
    rays        (azimuth, range) float64 0.5492 0.5492 0.5492 ... 359.5 359.5
    bins        (azimuth, range) float32 125.0 375.0 ... 9.962e+04 9.988e+04
Attributes:
    units:          dBZ
    standard_name:  radar_equivalent_reflectivity_factor_h
    long_name:      Equivalent reflectivity factor H

Create simple plot

Using xarray features a simple plot can be created like this. Note the sortby('rtime') method, which sorts the radials by time.

[17]:
swp.DBZH.sortby("rtime").plot(x="range", y="rtime", add_labels=False)
[17]:
<matplotlib.collections.QuadMesh at 0x7f05e8669190>
../../_images/notebooks_fileio_wradlib_rainbow_backend_26_1.png
[18]:
fig = pl.figure(figsize=(5, 5))
pm = swp.DBZH.wradlib.plot_ppi(proj={"latmin": 3e3}, fig=fig)
../../_images/notebooks_fileio_wradlib_rainbow_backend_27_0.png

Mask some values

[19]:
dbzh = swp["DBZH"].where(swp["DBZH"] >= 0)
dbzh.plot(x="x", y="y")
[19]:
<matplotlib.collections.QuadMesh at 0x7f05e86c3c90>
../../_images/notebooks_fileio_wradlib_rainbow_backend_29_1.png
[20]:
vol[0]
[20]:
<xarray.Dataset>
Dimensions:            (azimuth: 361, range: 400)
Coordinates:
  * azimuth            (azimuth) float64 0.5492 1.505 2.549 ... 358.5 359.5
    elevation          (azimuth) float64 ...
  * range              (range) float32 125.0 375.0 625.0 ... 9.962e+04 9.988e+04
    rtime              (azimuth) datetime64[ns] 2013-05-10T00:00:15.530303500...
    sweep_mode         <U20 ...
    longitude          float64 ...
    latitude           float64 ...
    altitude           float64 ...
    time               datetime64[ns] 2013-05-10T00:00:06.015151500
Data variables:
    DBZH               (azimuth, range) float32 ...
    sweep_number       int64 ...
    prt_mode           <U7 ...
    follow_mode        <U7 ...
    sweep_fixed_angle  float64 0.6
Attributes:
    fixed_angle:  0.6

Export to ODIM and CfRadial2

[21]:
vol[0].DBZH.sortby("rtime").plot(y="rtime")
[21]:
<matplotlib.collections.QuadMesh at 0x7f05e852af50>
../../_images/notebooks_fileio_wradlib_rainbow_backend_32_1.png
[22]:
vol.to_odim("rainbow_as_odim.h5")
vol.to_cfradial2("rainbow_as_cfradial2.nc")

Import again

[23]:
vola = wrl.io.open_odim_dataset(
    "rainbow_as_odim.h5", reindex_angle=False, keep_elevation=True
)
display(vola.root)
display(vola[0])
vola[0].DBZH.sortby("rtime").plot(y="rtime")
<xarray.Dataset>
Dimensions:              (sweep: 14)
Dimensions without coordinates: sweep
Data variables:
    volume_number        int64 0
    platform_type        <U5 'fixed'
    instrument_type      <U5 'radar'
    primary_axis         <U6 'axis_z'
    time_coverage_start  <U20 '2013-05-10T00:00:06Z'
    time_coverage_end    <U20 '2013-05-10 00:03:15Z'
    latitude             float64 ...
    longitude            float64 ...
    altitude             float64 ...
    sweep_group_name     (sweep) <U8 'sweep_0' 'sweep_1' ... 'sweep_13'
    sweep_fixed_angle    (sweep) float64 0.6 1.4 2.4 3.5 ... 17.9 21.3 25.4 30.0
Attributes:
    version:          None
    title:            None
    institution:      None
    references:       None
    source:           None
    history:          None
    comment:          im/exported using wradlib
    instrument_name:  None
    fixed_angle:      0.6
<xarray.Dataset>
Dimensions:            (azimuth: 361, range: 400)
Coordinates:
  * azimuth            (azimuth) float64 0.5492 1.505 2.549 ... 358.5 359.5
    elevation          (azimuth) float64 ...
    rtime              (azimuth) datetime64[ns] 2013-05-10T00:00:15.530303488...
  * range              (range) float32 125.0 375.0 625.0 ... 9.962e+04 9.988e+04
    sweep_mode         <U20 ...
    longitude          float64 ...
    latitude           float64 ...
    altitude           float64 ...
    time               datetime64[ns] 2013-05-10T00:00:06.015151616
Data variables:
    DBZH               (azimuth, range) float32 ...
    sweep_number       int64 ...
    prt_mode           <U7 ...
    follow_mode        <U7 ...
    sweep_fixed_angle  float64 0.6
Attributes:
    fixed_angle:  0.6
[23]:
<matplotlib.collections.QuadMesh at 0x7f05e84e1050>
../../_images/notebooks_fileio_wradlib_rainbow_backend_35_3.png
[24]:
volb = wrl.io.open_cfradial2_dataset("rainbow_as_cfradial2.nc")
display(volb.root)
display(volb[0])
volb[0].DBZH.sortby("rtime").plot(y="rtime")
<xarray.Dataset>
Dimensions:              (sweep: 14)
Dimensions without coordinates: sweep
Data variables:
    volume_number        int64 0
    platform_type        <U5 'fixed'
    instrument_type      <U5 'radar'
    primary_axis         <U6 'axis_z'
    time_coverage_start  <U20 '2013-05-10T00:00:06Z'
    time_coverage_end    <U20 '2013-05-10 00:03:15Z'
    latitude             float64 ...
    longitude            float64 ...
    altitude             float64 ...
    sweep_group_name     (sweep) <U8 'sweep_0' 'sweep_1' ... 'sweep_13'
    sweep_fixed_angle    (sweep) float64 0.6 1.4 2.4 3.5 ... 17.9 21.3 25.4 30.0
Attributes:
    version:          None
    title:            None
    institution:      None
    references:       None
    source:           None
    history:          None
    comment:          im/exported using wradlib
    instrument_name:  None
    fixed_angle:      0.6
<xarray.Dataset>
Dimensions:            (azimuth: 361, range: 400)
Coordinates:
  * azimuth            (azimuth) float64 0.5492 1.505 2.549 ... 358.5 359.5
    elevation          (azimuth) float64 ...
  * range              (range) float32 125.0 375.0 625.0 ... 9.962e+04 9.988e+04
    rtime              (azimuth) datetime64[ns] 2013-05-10T00:00:15.530303500...
    sweep_mode         <U20 ...
    longitude          float64 ...
    latitude           float64 ...
    altitude           float64 ...
    time               datetime64[ns] 2013-05-10T00:00:06.015151500
Data variables:
    DBZH               (azimuth, range) float32 ...
    sweep_number       int64 ...
    prt_mode           object ...
    follow_mode        object ...
    sweep_fixed_angle  float64 0.6
Attributes:
    fixed_angle:  0.6
[24]:
<matplotlib.collections.QuadMesh at 0x7f05e2b05350>
../../_images/notebooks_fileio_wradlib_rainbow_backend_36_3.png

Check equality

We have to sort accordingly and drop the time variables when checking equality.

[25]:
xr.testing.assert_allclose(vol.root, vola.root)
xr.testing.assert_allclose(
    vol[0].drop(["rtime", "time"]), vola[0].drop(["rtime", "time"])
)
xr.testing.assert_allclose(vol.root, volb.root)
xr.testing.assert_allclose(
    vol[0].drop(["rtime", "time"]), volb[0].drop(["rtime", "time"])
)
xr.testing.assert_allclose(vola.root, volb.root)
xr.testing.assert_allclose(
    vola[0].drop(["rtime", "time"]), volb[0].drop(["rtime", "time"])
)

More Rainbow5 loading mechanisms

Use xr.open_dataset to retrieve explicit group

Warning

Since \(\omega radlib\) version 1.18 the xarray backend engines for polar radar data have been renamed and prepended with wradlib- (eg. rainbow -> wradlib-rainbow). This was necessary to avoid clashes with the new xradar-package, which will eventually replace the wradlib engines. Users have to make sure to check which engine to use for their use-case when using xarray.open_dataset. Users might install and test xradar, and check if it is already robust enough for their use-cases (by using xradar’s engine="rainbow".

Since \(\omega radlib\) version 1.19 the xarray backend engines for polar radar data have been deprecated. The functionality is kept until wradlib version 2.0, when the backend-code will be removed completely. wradlib is importing that functionality from xradar-package whenever and wherever necessary.

Below we use a compatibility layer in wradlib to give users the chance to adapt their code. The first minimal change is that for every backend the group-layout is conforming to the CfRadial-standard naming scheme (sweep_0, sweep_1, etc.).

Below you can inspect the main differences of the wradlib compatibility layer and the plain xradar implementation.

use wradlib compatibility layer

[26]:
swp_a = xr.open_dataset(
    f,
    engine="wradlib-rainbow",
    group="sweep_5",
    backend_kwargs=dict(reindex_angle=False),
)
display(swp_a)
<xarray.Dataset>
Dimensions:            (azimuth: 361, range: 400)
Coordinates:
  * azimuth            (azimuth) float64 0.5052 1.516 2.51 ... 357.5 358.5 359.5
    elevation          (azimuth) float64 ...
  * range              (range) float32 125.0 375.0 625.0 ... 9.962e+04 9.988e+04
    rtime              (azimuth) datetime64[ns] ...
    sweep_mode         <U20 ...
    longitude          float64 ...
    latitude           float64 ...
    altitude           float64 ...
    time               datetime64[ns] ...
Data variables:
    DBZH               (azimuth, range) float32 ...
    sweep_number       int64 ...
    prt_mode           <U7 ...
    follow_mode        <U7 ...
    sweep_fixed_angle  float64 ...
Attributes:
    fixed_angle:  6.3

use xradar-backend

[27]:
swp_b = xr.open_dataset(
    f, engine="rainbow", group="sweep_5", backend_kwargs=dict(reindex_angle=False)
)
display(swp_b)
<xarray.Dataset>
Dimensions:            (azimuth: 361, range: 400)
Coordinates:
  * azimuth            (azimuth) float64 0.5052 1.516 2.51 ... 357.5 358.5 359.5
    elevation          (azimuth) float64 ...
  * range              (range) float32 125.0 375.0 625.0 ... 9.962e+04 9.988e+04
    time               (azimuth) datetime64[ns] ...
    longitude          float64 ...
    latitude           float64 ...
    altitude           float64 ...
Data variables:
    DBZH               (azimuth, range) float32 ...
    sweep_mode         <U20 ...
    sweep_number       int64 ...
    prt_mode           <U7 ...
    follow_mode        <U7 ...
    sweep_fixed_angle  float64 ...
[ ]: