improver.metadata.forecast_times module

Utilities to manipulate forecast time coordinates

improver.metadata.forecast_times.find_latest_cycletime(cubelist)[source]

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

Parameters

cubelist (iris.cube.CubeList) – 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, result_units='seconds')[source]

Return or calculate the lead time coordinate (forecast_period) within a cube, either by reading the forecast_period coordinate, or by calculating the difference between the time (points and bounds) and the forecast_reference_time. The units of the forecast_period, time and forecast_reference_time coordinates are converted, if required. The final coordinate will have units of seconds.

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.

  • result_units (str or cf_units.Unit) – Desired units for the resulting forecast period coordinate.

Returns

Describing the points and their units for ‘forecast_period’. 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. Units are result_units.

Return type

iris.coords.Coord

improver.metadata.forecast_times.rebadge_forecasts_as_latest_cycle(cubes, cycletime)[source]

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) – 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)[source]

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) – 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