xarray IRIS backend#

In this example, we read IRIS (sigmet) data files using the xradar iris xarray backend.

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

warnings.filterwarnings("ignore")
import matplotlib.pyplot as plt
import numpy as np
import xradar as xd
import datatree as xt
import xarray as xr

try:
    get_ipython().run_line_magic("matplotlib inline")
except:
    plt.ion()

Load IRIS Volume Data#

[2]:
fpath = "sigmet/SUR210819000227.RAWKPJV"
f = wrl.util.get_wradlib_data_file(fpath)
vol = xd.io.open_iris_datatree(f, reindex_angle=False)
Downloading file 'sigmet/SUR210819000227.RAWKPJV' from 'https://github.com/wradlib/wradlib-data/raw/pooch/data/sigmet/SUR210819000227.RAWKPJV' to '/home/runner/work/wradlib/wradlib/wradlib-data'.

Inspect RadarVolume#

[3]:
display(vol)
<xarray.DatasetView> Size: 232B
Dimensions:              ()
Data variables:
    latitude             float64 8B 58.48
    longitude            float64 8B 25.52
    altitude             float64 8B 157.0
    volume_number        int64 8B 0
    platform_type        <U5 20B 'fixed'
    instrument_type      <U5 20B 'radar'
    time_coverage_start  <U20 80B '2021-08-19T00:02:28Z'
    time_coverage_end    <U20 80B '2021-08-19T00:02:49Z'
Attributes:
    Conventions:      None
    instrument_name:  None
    version:          None
    title:            None
    institution:      None
    references:       None
    source:           None
    history:          None
    comment:          im/exported using xradar

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.DatasetView> Size: 232B
Dimensions:              ()
Data variables:
    latitude             float64 8B 58.48
    longitude            float64 8B 25.52
    altitude             float64 8B 157.0
    volume_number        int64 8B 0
    platform_type        <U5 20B 'fixed'
    instrument_type      <U5 20B 'radar'
    time_coverage_start  <U20 80B '2021-08-19T00:02:28Z'
    time_coverage_end    <U20 80B '2021-08-19T00:02:49Z'
Attributes:
    Conventions:      None
    instrument_name:  None
    version:          None
    title:            None
    institution:      None
    references:       None
    source:           None
    history:          None
    comment:          im/exported using xradar

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["sweep_0"])
<xarray.DatasetView> Size: 13MB
Dimensions:            (azimuth: 359, range: 833)
Coordinates:
    elevation          (azimuth) float32 1kB ...
    time               (azimuth) datetime64[ns] 3kB 2021-08-19T00:02:31.10400...
  * range              (range) float32 3kB 150.0 450.0 ... 2.494e+05 2.498e+05
    longitude          float64 8B ...
    latitude           float64 8B ...
    altitude           float64 8B ...
  * azimuth            (azimuth) float32 1kB 0.03021 1.035 2.054 ... 358.0 359.0
Data variables: (12/16)
    DBTH               (azimuth, range) float32 1MB ...
    DBZH               (azimuth, range) float32 1MB ...
    VRADH              (azimuth, range) float32 1MB ...
    WRADH              (azimuth, range) float32 1MB ...
    ZDR                (azimuth, range) float32 1MB ...
    KDP                (azimuth, range) float32 1MB ...
    ...                 ...
    SNRH               (azimuth, range) float32 1MB ...
    sweep_mode         <U20 80B ...
    sweep_number       int64 8B ...
    prt_mode           <U7 28B ...
    follow_mode        <U7 28B ...
    sweep_fixed_angle  float64 8B ...

Georeferencing#

[6]:
swp = vol["sweep_0"].ds.copy()
swp = swp.assign_coords(sweep_mode=swp.sweep_mode)
swp = swp.wrl.georef.georeference()

Inspect radar moments#

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

[7]:
display(swp.DBZH)
<xarray.DataArray 'DBZH' (azimuth: 359, range: 833)> Size: 1MB
[299047 values with dtype=float32]
Coordinates: (12/15)
    elevation   (azimuth) float64 3kB 0.5054 0.5054 0.5054 ... 0.5054 0.5054
    time        (azimuth) datetime64[ns] 3kB 2021-08-19T00:02:31.104000 ... 2...
  * range       (range) float32 3kB 150.0 450.0 750.0 ... 2.494e+05 2.498e+05
    longitude   float64 8B 25.52
    latitude    float64 8B 58.48
    altitude    float64 8B 157.0
    ...          ...
    y           (azimuth, range) float64 2MB 150.0 450.0 ... 2.493e+05 2.496e+05
    z           (azimuth, range) float64 2MB 158.3 161.0 ... 6.023e+03 6.034e+03
    gr          (azimuth, range) float64 2MB 150.0 450.0 ... 2.493e+05 2.496e+05
    rays        (azimuth, range) float32 1MB 0.03021 0.03021 ... 359.0 359.0
    bins        (azimuth, range) float32 1MB 150.0 450.0 ... 2.494e+05 2.498e+05
    crs_wkt     int64 8B 0
Attributes:
    units:          dBZ
    long_name:      Equivalent reflectivity factor H
    standard_name:  radar_equivalent_reflectivity_factor_h

Create simple plot#

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

For more details on plotting radar data see under Visualization.

[8]:
swp.DBZH.sortby("time").plot(x="range", y="time", add_labels=False)
[8]:
<matplotlib.collections.QuadMesh at 0x7fb0b81efd10>
../../../_images/notebooks_fileio_backends_iris_backend_16_1.png
[9]:
fig = plt.figure(figsize=(5, 5))
pm = swp.DBZH.wrl.vis.plot(crs={"latmin": 3e3}, fig=fig)
../../../_images/notebooks_fileio_backends_iris_backend_17_0.png

Retrieve explicit group#

[10]:
swp_b = xr.open_dataset(
    f, engine="iris", group="sweep_0", backend_kwargs=dict(reindex_angle=False)
)
display(swp_b)
<xarray.Dataset> Size: 13MB
Dimensions:            (azimuth: 359, range: 833)
Coordinates:
    elevation          (azimuth) float32 1kB ...
    time               (azimuth) datetime64[ns] 3kB ...
  * range              (range) float32 3kB 150.0 450.0 ... 2.494e+05 2.498e+05
    longitude          float64 8B ...
    latitude           float64 8B ...
    altitude           float64 8B ...
  * azimuth            (azimuth) float32 1kB 0.03021 1.035 2.054 ... 358.0 359.0
Data variables: (12/16)
    DBTH               (azimuth, range) float32 1MB ...
    DBZH               (azimuth, range) float32 1MB ...
    VRADH              (azimuth, range) float32 1MB ...
    WRADH              (azimuth, range) float32 1MB ...
    ZDR                (azimuth, range) float32 1MB ...
    KDP                (azimuth, range) float32 1MB ...
    ...                 ...
    SNRH               (azimuth, range) float32 1MB ...
    sweep_mode         <U20 80B ...
    sweep_number       int64 8B ...
    prt_mode           <U7 28B ...
    follow_mode        <U7 28B ...
    sweep_fixed_angle  float64 8B ...