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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)
/build/python-xarray-LlZKQX/python-xarray-2022.03.0/xarray/tutorial.py in open_dataset(name, cache, cache_dir, engine, **kws)
113 try:
--> 114 import pooch
115 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)
/tmp/ipykernel_1061160/3699872736.py in <module>
----> 1 ds = xr.tutorial.load_dataset("era5-2mt-2019-03-uk.grib", engine="cfgrib")
/build/python-xarray-LlZKQX/python-xarray-2022.03.0/xarray/tutorial.py in load_dataset(*args, **kwargs)
223 open_dataset
224 """
--> 225 with open_dataset(*args, **kwargs) as ds:
226 return ds.load()
227
/build/python-xarray-LlZKQX/python-xarray-2022.03.0/xarray/tutorial.py in open_dataset(name, cache, cache_dir, engine, **kws)
114 import pooch
115 except ImportError as e:
--> 116 raise ImportError(
117 "tutorial.open_dataset depends on pooch to download and manage datasets."
118 " To proceed please install pooch."
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)
/tmp/ipykernel_1061160/1072882670.py in <module>
----> 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)
/tmp/ipykernel_1061160/2626464068.py in <module>
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 )
NameError: name 'ds' is not defined
---------------------------------------------------------------------------
PermissionError Traceback (most recent call last)
/usr/lib/python3/dist-packages/IPython/core/formatters.py in __call__(self, obj)
339 pass
340 else:
--> 341 return printer(obj)
342 # Finally look for special method names
343 method = get_real_method(obj, self.print_method)
/usr/lib/python3/dist-packages/IPython/core/pylabtools.py in print_figure(fig, fmt, bbox_inches, base64, **kwargs)
149 FigureCanvasBase(fig)
150
--> 151 fig.canvas.print_figure(bytes_io, **kw)
152 data = bytes_io.getvalue()
153 if fmt == 'svg':
/usr/lib/python3/dist-packages/matplotlib/backend_bases.py in print_figure(self, filename, dpi, facecolor, edgecolor, orientation, format, bbox_inches, pad_inches, bbox_extra_artists, backend, **kwargs)
2293 )
2294 with getattr(renderer, "_draw_disabled", nullcontext)():
-> 2295 self.figure.draw(renderer)
2296
2297 if bbox_inches:
/usr/lib/python3/dist-packages/matplotlib/artist.py in 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()
/usr/lib/python3/dist-packages/matplotlib/artist.py in draw_wrapper(artist, renderer)
48 renderer.start_filter()
49
---> 50 return draw(artist, renderer)
51 finally:
52 if artist.get_agg_filter() is not None:
/usr/lib/python3/dist-packages/matplotlib/figure.py in draw(self, renderer)
2808
2809 self.patch.draw(renderer)
-> 2810 mimage._draw_list_compositing_images(
2811 renderer, self, artists, self.suppressComposite)
2812
/usr/lib/python3/dist-packages/matplotlib/image.py 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
/usr/lib/python3/dist-packages/matplotlib/artist.py in draw_wrapper(artist, renderer)
48 renderer.start_filter()
49
---> 50 return draw(artist, renderer)
51 finally:
52 if artist.get_agg_filter() is not None:
/usr/lib/python3/dist-packages/cartopy/mpl/geoaxes.py in draw(self, renderer, **kwargs)
556 self._done_img_factory = True
557
--> 558 return matplotlib.axes.Axes.draw(self, renderer=renderer, **kwargs)
559
560 def _update_title_position(self, renderer):
/usr/lib/python3/dist-packages/matplotlib/artist.py in draw_wrapper(artist, renderer)
48 renderer.start_filter()
49
---> 50 return draw(artist, renderer)
51 finally:
52 if artist.get_agg_filter() is not None:
/usr/lib/python3/dist-packages/matplotlib/axes/_base.py in draw(self, renderer)
3080 renderer.stop_rasterizing()
3081
-> 3082 mimage._draw_list_compositing_images(
3083 renderer, self, artists, self.figure.suppressComposite)
3084
/usr/lib/python3/dist-packages/matplotlib/image.py 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
/usr/lib/python3/dist-packages/matplotlib/artist.py in draw_wrapper(artist, renderer)
48 renderer.start_filter()
49
---> 50 return draw(artist, renderer)
51 finally:
52 if artist.get_agg_filter() is not None:
/usr/lib/python3/dist-packages/cartopy/mpl/feature_artist.py in draw(self, renderer, *args, **kwargs)
148 except ValueError:
149 warnings.warn('Unable to determine extent. Defaulting to global.')
--> 150 geoms = self._feature.intersecting_geometries(extent)
151
152 # Combine all the keyword args in priority order.
/usr/lib/python3/dist-packages/cartopy/feature/__init__.py in intersecting_geometries(self, extent)
295 """
296 self.scaler.scale_from_extent(extent)
--> 297 return super().intersecting_geometries(extent)
298
299 def with_scale(self, new_scale):
/usr/lib/python3/dist-packages/cartopy/feature/__init__.py in intersecting_geometries(self, extent)
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:
/usr/lib/python3/dist-packages/cartopy/feature/__init__.py in geometries(self)
277 key = (self.name, self.category, self.scale)
278 if key not in _NATURAL_EARTH_GEOM_CACHE:
--> 279 path = shapereader.natural_earth(resolution=self.scale,
280 category=self.category,
281 name=self.name)
/usr/lib/python3/dist-packages/cartopy/io/shapereader.py in natural_earth(resolution, category, name)
277 format_dict = {'config': config, 'category': category,
278 'name': name, 'resolution': resolution}
--> 279 return ne_downloader.path(format_dict)
280
281
/usr/lib/python3/dist-packages/cartopy/io/__init__.py in path(self, format_dict)
201 else:
202 # we need to download the file
--> 203 result_path = self.acquire_resource(target_path, format_dict)
204
205 return result_path
/usr/lib/python3/dist-packages/cartopy/io/shapereader.py in acquire_resource(self, target_path, format_dict)
327 target_dir = os.path.dirname(target_path)
328 if not os.path.isdir(target_dir):
--> 329 os.makedirs(target_dir)
330
331 url = self.url(format_dict)
/usr/lib/python3.9/os.py 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
/usr/lib/python3.9/os.py 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
/usr/lib/python3.9/os.py 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
/usr/lib/python3.9/os.py 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
/usr/lib/python3.9/os.py 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
/usr/lib/python3.9/os.py 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
/usr/lib/python3.9/os.py 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
PermissionError: [Errno 13] Permission denied: '/sbuild-nonexistent'
<Figure size 720x720 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)
/tmp/ipykernel_1061160/2485972357.py in <module>
----> 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