Setting Up Your Dataset

climpred relies on a consistent naming system for xarray dimensions. This allows things to run more easily under-the-hood.

Prediction ensembles are expected at the minimum to contain dimensions init and lead. init is the initialization dimension, that relays the time steps at which the ensemble was initialized. init must be of type int, pd.DatetimeIndex, or xr.cftimeIndex. If init is of type int, it is assumed to be annual data. A user warning is issues when this assumption is made. lead is the lead time of the forecasts from initialization. The units for the lead dimension must be specified in as an attribute. Valid options are years, seasons, months, weeks, pentads, days. Another crucial dimension is member, which holds the various ensemble members. Any additional dimensions will be passed through climpred without issue: these could be things like lat, lon, depth, etc.

Verification products are expected to contain the time dimension at the minimum. For best use of climpred, their time dimension should cover the full length of init from the accompanying prediction ensemble, if possible. The time dimension must be of type int, pd.DatetimeIndex or xr.cftimeIndex. time dimension of type int is assumed to be annual data. A user warning is issued when this assumption is made. These products can also include additional dimensions, such as lat, lon, depth, etc.

See the below table for a summary of dimensions used in climpred, and data types that climpred supports for them.

Short Name	Types	Long Name	Attribute(s)
lead	int	lead timestep after initialization, [init]	units (str) [years, seasons, months, weeks, pentads, days]
init	int, pd.DatetimeIndex, xr.CFTimeIndex	initialization: start date of experiment	None
member	int, str	ensemble member	None