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GRIB Data Example¶
GRIB format is commonly used to disseminate atmospheric model data. With xarray and the cfgrib engine, GRIB data can easily be analyzed and visualized.
[1]:
import xarray as xr
import matplotlib.pyplot as plt
To read GRIB data, you can use xarray.load_dataset
. The only extra code you need is to specify the engine as cfgrib
.
[2]:
ds = xr.tutorial.load_dataset("era5-2mt-2019-03-uk.grib", engine="cfgrib")
---------------------------------------------------------------------------
ModuleNotFoundError Traceback (most recent call last)
File /build/python-xarray-dzg29i/python-xarray-2022.12.0/xarray/tutorial.py:132, in open_dataset(name, cache, cache_dir, engine, **kws)
131 try:
--> 132 import pooch
133 except ImportError as e:
ModuleNotFoundError: No module named 'pooch'
The above exception was the direct cause of the following exception:
ImportError Traceback (most recent call last)
Cell In [2], line 1
----> 1 ds = xr.tutorial.load_dataset("era5-2mt-2019-03-uk.grib", engine="cfgrib")
File /build/python-xarray-dzg29i/python-xarray-2022.12.0/xarray/tutorial.py:284, in load_dataset(*args, **kwargs)
247 def load_dataset(*args, **kwargs) -> Dataset:
248 """
249 Open, load into memory, and close a dataset from the online repository
250 (requires internet).
(...)
282 load_dataset
283 """
--> 284 with open_dataset(*args, **kwargs) as ds:
285 return ds.load()
File /build/python-xarray-dzg29i/python-xarray-2022.12.0/xarray/tutorial.py:134, in open_dataset(name, cache, cache_dir, engine, **kws)
132 import pooch
133 except ImportError as e:
--> 134 raise ImportError(
135 "tutorial.open_dataset depends on pooch to download and manage datasets."
136 " To proceed please install pooch."
137 ) from e
139 logger = pooch.get_logger()
140 logger.setLevel("WARNING")
ImportError: tutorial.open_dataset depends on pooch to download and manage datasets. To proceed please install pooch.
Let’s create a simple plot of 2-m air temperature in degrees Celsius:
[3]:
ds = ds - 273.15
ds.t2m[0].plot(cmap=plt.cm.coolwarm)
---------------------------------------------------------------------------
NameError Traceback (most recent call last)
Cell In [3], line 1
----> 1 ds = ds - 273.15
2 ds.t2m[0].plot(cmap=plt.cm.coolwarm)
NameError: name 'ds' is not defined
With CartoPy, we can create a more detailed plot, using built-in shapefiles to help provide geographic context:
[4]:
import cartopy.crs as ccrs
import cartopy
fig = plt.figure(figsize=(10, 10))
ax = plt.axes(projection=ccrs.Robinson())
ax.coastlines(resolution="10m")
plot = ds.t2m[0].plot(
cmap=plt.cm.coolwarm, transform=ccrs.PlateCarree(), cbar_kwargs={"shrink": 0.6}
)
plt.title("ERA5 - 2m temperature British Isles March 2019")
---------------------------------------------------------------------------
NameError Traceback (most recent call last)
Cell In [4], line 7
5 ax = plt.axes(projection=ccrs.Robinson())
6 ax.coastlines(resolution="10m")
----> 7 plot = ds.t2m[0].plot(
8 cmap=plt.cm.coolwarm, transform=ccrs.PlateCarree(), cbar_kwargs={"shrink": 0.6}
9 )
10 plt.title("ERA5 - 2m temperature British Isles March 2019")
NameError: name 'ds' is not defined
---------------------------------------------------------------------------
PermissionError Traceback (most recent call last)
File /usr/lib/python3/dist-packages/IPython/core/formatters.py:339, in BaseFormatter.__call__(self, obj)
337 pass
338 else:
--> 339 return printer(obj)
340 # Finally look for special method names
341 method = get_real_method(obj, self.print_method)
File /usr/lib/python3/dist-packages/IPython/core/pylabtools.py:151, in print_figure(fig, fmt, bbox_inches, base64, **kwargs)
148 from matplotlib.backend_bases import FigureCanvasBase
149 FigureCanvasBase(fig)
--> 151 fig.canvas.print_figure(bytes_io, **kw)
152 data = bytes_io.getvalue()
153 if fmt == 'svg':
File /usr/lib/python3/dist-packages/matplotlib/backend_bases.py:2295, in FigureCanvasBase.print_figure(self, filename, dpi, facecolor, edgecolor, orientation, format, bbox_inches, pad_inches, bbox_extra_artists, backend, **kwargs)
2289 renderer = _get_renderer(
2290 self.figure,
2291 functools.partial(
2292 print_method, orientation=orientation)
2293 )
2294 with getattr(renderer, "_draw_disabled", nullcontext)():
-> 2295 self.figure.draw(renderer)
2297 if bbox_inches:
2298 if bbox_inches == "tight":
File /usr/lib/python3/dist-packages/matplotlib/artist.py:73, in _finalize_rasterization.<locals>.draw_wrapper(artist, renderer, *args, **kwargs)
71 @wraps(draw)
72 def draw_wrapper(artist, renderer, *args, **kwargs):
---> 73 result = draw(artist, renderer, *args, **kwargs)
74 if renderer._rasterizing:
75 renderer.stop_rasterizing()
File /usr/lib/python3/dist-packages/matplotlib/artist.py:50, in allow_rasterization.<locals>.draw_wrapper(artist, renderer)
47 if artist.get_agg_filter() is not None:
48 renderer.start_filter()
---> 50 return draw(artist, renderer)
51 finally:
52 if artist.get_agg_filter() is not None:
File /usr/lib/python3/dist-packages/matplotlib/figure.py:2837, in Figure.draw(self, renderer)
2834 # ValueError can occur when resizing a window.
2836 self.patch.draw(renderer)
-> 2837 mimage._draw_list_compositing_images(
2838 renderer, self, artists, self.suppressComposite)
2840 for sfig in self.subfigs:
2841 sfig.draw(renderer)
File /usr/lib/python3/dist-packages/matplotlib/image.py:132, in _draw_list_compositing_images(renderer, parent, artists, suppress_composite)
130 if not_composite or not has_images:
131 for a in artists:
--> 132 a.draw(renderer)
133 else:
134 # Composite any adjacent images together
135 image_group = []
File /usr/lib/python3/dist-packages/matplotlib/artist.py:50, in allow_rasterization.<locals>.draw_wrapper(artist, renderer)
47 if artist.get_agg_filter() is not None:
48 renderer.start_filter()
---> 50 return draw(artist, renderer)
51 finally:
52 if artist.get_agg_filter() is not None:
File /usr/lib/python3/dist-packages/cartopy/mpl/geoaxes.py:538, in GeoAxes.draw(self, renderer, **kwargs)
533 self.imshow(img, extent=extent, origin=origin,
534 transform=factory.crs, *factory_args[1:],
535 **factory_kwargs)
536 self._done_img_factory = True
--> 538 return super().draw(renderer=renderer, **kwargs)
File /usr/lib/python3/dist-packages/matplotlib/artist.py:50, in allow_rasterization.<locals>.draw_wrapper(artist, renderer)
47 if artist.get_agg_filter() is not None:
48 renderer.start_filter()
---> 50 return draw(artist, renderer)
51 finally:
52 if artist.get_agg_filter() is not None:
File /usr/lib/python3/dist-packages/matplotlib/axes/_base.py:3091, in _AxesBase.draw(self, renderer)
3088 a.draw(renderer)
3089 renderer.stop_rasterizing()
-> 3091 mimage._draw_list_compositing_images(
3092 renderer, self, artists, self.figure.suppressComposite)
3094 renderer.close_group('axes')
3095 self.stale = False
File /usr/lib/python3/dist-packages/matplotlib/image.py:132, in _draw_list_compositing_images(renderer, parent, artists, suppress_composite)
130 if not_composite or not has_images:
131 for a in artists:
--> 132 a.draw(renderer)
133 else:
134 # Composite any adjacent images together
135 image_group = []
File /usr/lib/python3/dist-packages/matplotlib/artist.py:50, in allow_rasterization.<locals>.draw_wrapper(artist, renderer)
47 if artist.get_agg_filter() is not None:
48 renderer.start_filter()
---> 50 return draw(artist, renderer)
51 finally:
52 if artist.get_agg_filter() is not None:
File /usr/lib/python3/dist-packages/cartopy/mpl/feature_artist.py:151, in FeatureArtist.draw(self, renderer, *args, **kwargs)
149 except ValueError:
150 warnings.warn('Unable to determine extent. Defaulting to global.')
--> 151 geoms = self._feature.intersecting_geometries(extent)
153 # Combine all the keyword args in priority order.
154 prepared_kwargs = style_merge(self._feature.kwargs,
155 self._kwargs,
156 kwargs)
File /usr/lib/python3/dist-packages/cartopy/feature/__init__.py:303, in NaturalEarthFeature.intersecting_geometries(self, extent)
296 """
297 Returns an iterator of shapely geometries that intersect with
298 the given extent.
299 The extent is assumed to be in the CRS of the feature.
300 If extent is None, the method returns all geometries for this dataset.
301 """
302 self.scaler.scale_from_extent(extent)
--> 303 return super().intersecting_geometries(extent)
File /usr/lib/python3/dist-packages/cartopy/feature/__init__.py:106, in Feature.intersecting_geometries(self, extent)
103 if extent is not None:
104 extent_geom = sgeom.box(extent[0], extent[2],
105 extent[1], extent[3])
--> 106 return (geom for geom in self.geometries() if
107 geom is not None and extent_geom.intersects(geom))
108 else:
109 return self.geometries()
File /usr/lib/python3/dist-packages/cartopy/feature/__init__.py:285, in NaturalEarthFeature.geometries(self)
283 key = (self.name, self.category, self.scale)
284 if key not in _NATURAL_EARTH_GEOM_CACHE:
--> 285 path = shapereader.natural_earth(resolution=self.scale,
286 category=self.category,
287 name=self.name)
288 geometries = tuple(shapereader.Reader(path).geometries())
289 _NATURAL_EARTH_GEOM_CACHE[key] = geometries
File /usr/lib/python3/dist-packages/cartopy/io/shapereader.py:283, in natural_earth(resolution, category, name)
279 ne_downloader = Downloader.from_config(('shapefiles', 'natural_earth',
280 resolution, category, name))
281 format_dict = {'config': config, 'category': category,
282 'name': name, 'resolution': resolution}
--> 283 return ne_downloader.path(format_dict)
File /usr/lib/python3/dist-packages/cartopy/io/__init__.py:203, in Downloader.path(self, format_dict)
200 result_path = target_path
201 else:
202 # we need to download the file
--> 203 result_path = self.acquire_resource(target_path, format_dict)
205 return result_path
File /usr/lib/python3/dist-packages/cartopy/io/shapereader.py:333, in NEShpDownloader.acquire_resource(self, target_path, format_dict)
331 target_dir = os.path.dirname(target_path)
332 if not os.path.isdir(target_dir):
--> 333 os.makedirs(target_dir)
335 url = self.url(format_dict)
337 shapefile_online = self._urlopen(url)
File /usr/lib/python3.10/os.py:215, in makedirs(name, mode, exist_ok)
213 if head and tail and not path.exists(head):
214 try:
--> 215 makedirs(head, exist_ok=exist_ok)
216 except FileExistsError:
217 # Defeats race condition when another thread created the path
218 pass
File /usr/lib/python3.10/os.py:215, in makedirs(name, mode, exist_ok)
213 if head and tail and not path.exists(head):
214 try:
--> 215 makedirs(head, exist_ok=exist_ok)
216 except FileExistsError:
217 # Defeats race condition when another thread created the path
218 pass
[... skipping similar frames: makedirs at line 215 (3 times)]
File /usr/lib/python3.10/os.py:215, in makedirs(name, mode, exist_ok)
213 if head and tail and not path.exists(head):
214 try:
--> 215 makedirs(head, exist_ok=exist_ok)
216 except FileExistsError:
217 # Defeats race condition when another thread created the path
218 pass
File /usr/lib/python3.10/os.py:225, in makedirs(name, mode, exist_ok)
223 return
224 try:
--> 225 mkdir(name, mode)
226 except OSError:
227 # Cannot rely on checking for EEXIST, since the operating system
228 # could give priority to other errors like EACCES or EROFS
229 if not exist_ok or not path.isdir(name):
PermissionError: [Errno 13] Permission denied: '/sbuild-nonexistent'
<Figure size 1000x1000 with 1 Axes>
Finally, we can also pull out a time series for a given location easily:
[5]:
ds.t2m.sel(longitude=0, latitude=51.5).plot()
plt.title("ERA5 - London 2m temperature March 2019")
---------------------------------------------------------------------------
NameError Traceback (most recent call last)
Cell In [5], line 1
----> 1 ds.t2m.sel(longitude=0, latitude=51.5).plot()
2 plt.title("ERA5 - London 2m temperature March 2019")
NameError: name 'ds' is not defined