The documentation for iris-grib¶
iris-grib provides functionality for converting between weather and
climate datasets that are stored as GRIB files and
GRIB files can be loaded as Iris cubes using
iris-grib so that you can use Iris
for analysing and visualising the contents of the GRIB files. Iris cubes can be saved to
GRIB files using
The contents of
iris-grib represent the former grib loading and saving capabilities
Iris itself. These capabilities have been separated into a discrete library
so that Iris becomes less monolithic as a library.
iris-grib to load existing GRIB files we can make use of the
>>> import os >>> import iris_sample_data >>> import iris_grib >>> cubes = iris_grib.load_cubes(os.path.join(iris_sample_data.path, 'polar_stereo.grib2')) >>> print cubes <generator object load_cubes at 0x7f69aba69d70>
As we can see, this returns a generator object. The generator object may be iterated over to access all the Iris cubes loaded from the GRIB file, or converted directly to a list:
>>> cubes = list(cubes) >>> print cubes [<iris 'Cube' of air_temperature / (K) (projection_y_coordinate: 200; projection_x_coordinate: 247)>]
There is no functionality in iris-grib that directly replicates
iris.load_cube (that is, load a single cube directly rather than returning
a length-one CubeList. Instead you could use the following, assuming that the
GRIB file you have loaded contains data that can be loaded to a single cube:
>>> cube, = list(cubes) >>> print cube air_temperature / (K) (projection_y_coordinate: 200; projection_x_coordinate: 247) Dimension coordinates: projection_y_coordinate x - projection_x_coordinate - x Scalar coordinates: forecast_period: 6 hours forecast_reference_time: 2013-05-20 00:00:00 pressure: 101500.0 Pa time: 2013-05-20 06:00:00
This makes use of an idiom known as variable unpacking.
iris-grib to save Iris cubes to a GRIB file we can make use of the
>>> iris_grib.save_grib2(my_cube, 'my_file.grib2')
As the function name suggests, only saving to GRIB2 is supported.
Interconnectivity with Iris¶
You can use the functionality provided by
iris-grib directly within Iris
without having to explicitly import
iris-grib, as long as you have both Iris
iris-grib available to your Python interpreter.
>>> import iris >>> import iris_sample_data >>> cube = iris.load_cube(iris.sample_data_path('polar_stereo.grib2'))
Similarly, you can save your cubes to a GRIB file directly from Iris
>>> iris.save(my_cube, 'my_file.grib2')