improver.metadata.forecast_times module

Utilities to manipulate forecast time coordinates

_calculate_forecast_period(time_coord, frt_coord, dim_coord=False, coord_spec=TimeSpec(calendar=None, dtype=<class 'numpy.int32'>, units='seconds'))

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

Parameters:

• time_coord (Coord) – Time coordinate

• frt_coord (Coord) – Forecast reference coordinate

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

• coord_spec (TimeSpec) – Specification of units and dtype for the forecast_period coordinate.

Return type:

Coord

Returns:

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

Warns:

UserWarning – If any calculated forecast periods are negative

_create_frt_type_coord(cube, point, name='forecast_reference_time')

Create a new auxiliary coordinate based on forecast reference time

Parameters:

• cube (Cube) – Input cube with scalar forecast reference time coordinate

• points – Single datetime point for output coord

• name (str) – Name of aux coord to be returned

Return type:

DimCoord

Returns:

New auxiliary coordinate

_find_latest_cycletime(cubelist)

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

Parameters:

cubelist (Union[CubeList, List[Cube]]) – A list of cubes each containing single time step from different forecast cycles.

Return type:

datetime

Returns:

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

add_blend_time(cube, cycletime)

Function to add scalar blend time coordinate to a blended cube based on current cycle time. Modifies cube in place. :rtype: None

Args:

cubes:

Cube to add blend time coordinate

cycletime:

Required blend time in a YYYYMMDDTHHMMZ format e.g. 20171122T0100Z

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 or blend_time.

Parameters:

• 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 reference time and the time coordinates, even if the forecast_period coordinate exists. Default is False.

Return type:

Coord

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.

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 (Union[CubeList, List[Cube]]) – Cubes that will have their forecast_reference_time and forecast_period updated.

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

Return type:

CubeList

Returns:

Updated cubes

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 (Union[CubeList, List[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 for the cycletime that will be used to replace the forecast_reference_time on the individual cubes.

Return type:

CubeList

Returns:

Updated cubes

Raises:

ValueError – if forecast_reference_time is a dimension coordinate