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 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/main/data/sigmet/SUR210819000227.RAWKPJV' to '/home/runner/work/wradlib-notebooks/wradlib-notebooks/wradlib-data'.
Inspect RadarVolume#
[3]:
display(vol)
<xarray.DatasetView> Size: 248B Dimensions: (sweep: 1) Dimensions without coordinates: sweep Data variables: 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' longitude float64 8B 25.52 altitude float64 8B 157.0 latitude float64 8B 58.48 sweep_fixed_angle (sweep) float64 8B 0.5 sweep_group_name (sweep) int64 8B 0 Attributes: Conventions: None instrument_name: Surgavere, Radar version: None title: None institution: None references: None source: Sigmet history: None comment: Dual pol 250km hybrid surveillance task 0.5 deg 2.5minu... scan_name: PPI1_H
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: 248B Dimensions: (sweep: 1) Dimensions without coordinates: sweep Data variables: 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' longitude float64 8B 25.52 altitude float64 8B 157.0 latitude float64 8B 58.48 sweep_fixed_angle (sweep) float64 8B 0.5 sweep_group_name (sweep) int64 8B 0 Attributes: Conventions: None instrument_name: Surgavere, Radar version: None title: None institution: None references: None source: Sigmet history: None comment: Dual pol 250km hybrid surveillance task 0.5 deg 2.5minu... scan_name: PPI1_H
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: (sweep: 1, 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 Dimensions without coordinates: sweep 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) sweep_mode <U20 80B 'azimuth_surveillance' 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 ... ... 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: long_name: Equivalent reflectivity factor H standard_name: radar_equivalent_reflectivity_factor_h units: dBZ
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 0x7f93a0a15d60>

[9]:
fig = plt.figure(figsize=(5, 5))
pm = swp.DBZH.wrl.vis.plot(crs={"latmin": 3e3}, fig=fig)

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 ... Attributes: source: Sigmet scan_name: PPI1_H instrument_name: Surgavere, Radar comment: Dual pol 250km hybrid surveillance task 0.5 deg 2.5minu...