improver.utilities.time_lagging module

Provide support utilities for time lagging ensembles

class GenerateTimeLaggedEnsemble(rebadge_realizations=False)

Bases: BasePlugin

Combine realizations from different forecast cycles into one cube.

• If a cube has no realization coordinate, one is added. For example: If you provide two deterministic cubes, the output will have realization coordinates [0, 1].

• For fully deterministic input (no realization coordinates on any cube), added realizations are assigned sequentially in input order (0, 1, 2, …).

• For mixed input (some cubes have realizations and others do not), missing coordinates are added only to cubes that need them. For example: If you provide one deterministic and one ensemble cube, the deterministic cube will be assigned a new realization, while the ensemble cube retains its original realization numbers.

• If this creates duplicate realization numbers across the combined inputs, all realization numbers are rebadged to a unique sequential set in input order before merging. For example: If two cubes both have realization 0, the output will have realizations [0, 1] (rebadged).

• If rebadge_realizations=True is set, the final output cube’s realization coordinate will always be sequentially numbered from 0. For example: If the merged cube has 3 realizations, they will be numbered [0, 1, 2] regardless of their original values.

__init__(rebadge_realizations=False)

Initialise plugin.

Parameters:

rebadge_realizations (bool) – If True, rebadge realization points on the final merged cube to sequential values starting at 0.

_abc_impl = <_abc._abc_data object>

_check_validity_times_match(cubelist)

Raise ValueError if cubes have mismatched validity times.

Parameters:

cubelist (CubeList) – List of input forecasts.

Raises:

ValueError – If input cubes have mismatched validity times.

Return type:

None

_rebadge_duplicate_realizations(cubelist)

If duplicate realization numbers exist across the cubelist, rebadge all realization numbers to a unique sequential set in input order.

Parameters:

cubelist (CubeList) – List of input forecasts.

Return type:

CubeList

Returns:

Cubelist with unique realization numbers across all cubes.

add_realization_coord(cubelist)

Add a realization coordinate to each cube in the cubelist if not already present. This facilitates the creation of a time-lagged ensemble from deterministic forecasts.

Parameters:

cubelist (CubeList) – List of input forecasts.

Return type:

Cube

Returns:

Cubelist with a realization coordinate added to each cube if not already present.

process(*cubes)

Take an input cubelist containing forecasts from different cycles and merges them into a single cube.

The steps taken are:

1. Update forecast reference time and period to match the latest contributing cycle.

2. Check for duplicate realization numbers. If a duplicate is found, renumber all of the realizations uniquely.

3. Concatenate into one cube along the realization axis.

Parameters:

cubelist – List of input forecasts

Return type:

Cube

Returns:

Concatenated forecasts

Warns:

• UserWarning – If only a single cube is provided, so time lagging will have

• no effect.