improver.metadata.forecast_times module

Utilities to manipulate forecast time coordinates

improver.metadata.forecast_times._calculate_forecast_period(time_coord, frt_coord, dim_coord=False)

Calculate a forecast period from existing time and forecast reference time coordinates.

Parameters

• time_coord (iris.coords.Coord) – Time coordinate

• frt_coord (iris.coords.Coord) – Forecast reference coordinate

• dim_coord (bool) – If true, create an iris.coords.DimCoord instance. Default is to create an iris.coords.AuxCoord.

Returns

Forecast period coordinate corresponding to the input times and forecast reference times specified

Return type

iris.coords.Coord

Warns

UserWarning – If any calculated forecast periods are negative

improver.metadata.forecast_times.find_latest_cycletime(cubelist)

Find the latest cycletime from the cubes in a cubelist and convert it into a datetime object.

Parameters

cubelist (iris.cube.CubeList or list of iris.cube.Cube) – A list of cubes each containing single time step from different forecast cycles.

Returns

A datetime object corresponding to the latest forecast reference time in the input cubelist.

Return type

datetime.datetime

improver.metadata.forecast_times.forecast_period_coord(cube, force_lead_time_calculation=False)

Return the lead time coordinate (forecast_period) from a cube, either by reading an existing forecast_period coordinate, or by calculating the difference between time and forecast_reference_time.

Parameters

• cube (iris.cube.Cube) – Cube from which the lead times will be determined.

• force_lead_time_calculation (bool) – Force the lead time to be calculated from the forecast_reference_time and the time coordinate, even if the forecast_period coordinate exists. Default is False.

Returns

New forecast_period coord. A DimCoord is returned if the forecast_period coord is already present in the cube as a DimCoord and this coord does not need changing, otherwise it will be an AuxCoord.

Return type

iris.coords.Coord

improver.metadata.forecast_times.rebadge_forecasts_as_latest_cycle(cubes, cycletime=None)

Function to update the forecast_reference_time and forecast_period on a list of input forecasts to match either a given cycletime, or the most recent forecast in the list (proxy for the current cycle).

Parameters

• cubes (iris.cube.CubeList or list of iris.cube.Cube) – Cubes that will have their forecast_reference_time and forecast_period updated.

• cycletime (str or None) – Required forecast reference time in a YYYYMMDDTHHMMZ format e.g. 20171122T0100Z. If None, the latest forecast reference time is used.

Returns

Updated cubes

Return type

iris.cube.CubeList

improver.metadata.forecast_times.unify_cycletime(cubes, cycletime)

Function to unify the forecast_reference_time and update forecast_period. The cycletime specified is used as the forecast_reference_time, and the forecast_period is recalculated using the time coordinate and updated forecast_reference_time.

Parameters

• cubes (iris.cube.CubeList or list of iris.cube.Cube) – Cubes that will have their forecast_reference_time and forecast_period updated. Any bounds on the forecast_reference_time coordinate will be discarded.

• cycletime (datetime.datetime) – Datetime for the cycletime that will be used to replace the forecast_reference_time on the individual cubes.

Returns

Updated cubes

Return type

iris.cube.CubeList

Raises

ValueError – if forecast_reference_time is a dimension coordinate