What’s new in Iris 1.8
|Date:||3rd June 2015
This document explains the new/changed features of Iris in version 1.8.
(View all changes.)
Iris 1.8 features
Showcase: Rotate winds
Iris can now rotate and unrotate wind vector data by transforming the wind
vector data to another coordinate system.
>>> from iris.analysis.cartography import rotate_winds
>>> u_cube = iris.load_cube('my_rotated_u_wind_cube.pp')
>>> v_cube = iris.load_cube('my_rotated_v_wind_cube.pp')
>>> target_cs = iris.coord_systems.GeogCS(6371229.0)
>>> u_prime, v_prime = rotate_winds(u_cube, v_cube, target_cs)
Showcase: Nearest-neighbour scheme
A nearest-neighbour scheme for interpolation and regridding has been added
to Iris. This joins the existing Linear and
AreaWeighted interpolation and regridding schemes.
>>> result = cube.interpolate(sample_points, iris.analysis.Nearest())
>>> regridded_cube = cube.regrid(target_grid, iris.analysis.Nearest())
Showcase: Slices over a coordinate
You can slice over one or more dimensions of a cube using iris.cube.Cube.slices_over().
This provides similar functionality to slices() but with
almost the opposite outcome.
Using slices() to slice a cube on a selected dimension returns
all possible slices of the cube with the selected dimension retaining its dimensionality.
Using slices_over() to slice a cube on a selected
dimension returns all possible slices of the cube over the selected dimension.
To demonstrate this:
>>> cube = iris.load(iris.sample_data_path('colpex.pp'))
air_potential_temperature / (K) (time: 6; model_level_number: 10; grid_latitude: 83; grid_longitude: 83)
>>> my_slice = next(cube.slices('time'))
>>> my_slice_over = next(cube.slices_over('time'))
air_potential_temperature / (K) (time: 6)
air_potential_temperature / (K) (model_level_number: 10; grid_latitude: 83; grid_longitude: 83)
- A cube’s lazy data payload will still be lazy after saving; the data will not
be loaded into memory by the save operation.
- Cubes with data payloads larger than system memory can now be saved to NetCDF
through biggus streaming the data to disk.
- ocean sigma coordinate,
- ocean s coordinate,
- ocean s coordinate, generic form 1, and
- ocean s coordinate, generic form 2.
- Fix in netCDF loader to correctly determine whether the longitude coordinate
(including scalar coordinates) is circular.
- iris.cube.Cube.intersection() now supports bounds that extend slightly beyond 360
- Lateral Boundary Condition (LBC) type FieldFiles are now handled correctly by the FF loader.
- Making a copy of a scalar cube with no data now correctly copies the data array.
- Height coordinates in NAME trajectory output files have been changed to match other
NAME output file formats.
- Fixed datatype when loading an integer_constants array from a FieldsFile.
- FF/PP loader adds appropriate cell methods for lbtim.ib = 3 intervals.
- An exception is raised if the units of the latitude and longitude coordinates
of the cube passed into iris.analysis.cartography.area_weights() are not
convertible to radians.
- GRIB1 loader now creates a time coordinate for a time range indicator of 2.
- NetCDF loader now loads units that are empty strings as dimensionless.
- The PP loader now carefully handles floating point errors in date time conversions to hours.
- The handling fill values for lazy data loaded from NetCDF files is altered, such that the
_FillValue set in the file is preserved through lazy operations.
- The risk that cube intersections could return incorrect results due to floating point
tolerances is reduced.
- The new GRIB2 loading code is altered to enable the loading of various data representation
templates; the data value unpacking is handled by the GRIB API.
- Saving cube collections to NetCDF, where multiple similar aux-factories exist within the cubes,
is now carefully handled such that extra file variables are created where required in some cases.
- A fix to prevent the error: AttributeError: ‘module’ object has no attribute ‘date2num’.
This was caused by the function netcdftime.date2num() being removed from the netCDF4
package in recent versions.
- The original GRIB loader has been deprecated and replaced with a new
template-based GRIB loader.
- Deprecated default NetCDF save behaviour of assigning the outermost
dimension to be unlimited. Switch to the new behaviour with no auto
assignment by setting iris.FUTURE.netcdf_no_unlimited to True.
- The former experimental method
“iris.experimental.regrid.regrid_bilinear_rectilinear_src_and_grid” has been removed, as
iris.analysis.Linear now includes this functionality.