Cluster ParametersThe ECMWF offers additional information on their ensemble forecasts describing the behaviour of the individual ensemble forecast members with respect to each other. This comparison happens by grouping similar members into clusters.
The information offered can be grouped into two categories:
- Information about the whole set of clusters
- Information about a specific clusters
Information about the whole set of clusters
Number of ClustersThe number of clusters depends on the variability of the model and thus can vary over the course of a model run. Hence the number of clusters at a specific time step is of interest:
validdate;number_of_clusters:x 2020-10-23T00:00:00Z;4 2020-10-23T12:00:00Z;5 2020-10-24T00:00:00Z;6 2020-10-24T12:00:00Z;4 2020-10-25T00:00:00Z;4 2020-10-25T12:00:00Z;6 2020-10-26T00:00:00Z;2 2020-10-26T12:00:00Z;2 2020-10-27T00:00:00Z;2 2020-10-27T12:00:00Z;2 2020-10-28T00:00:00Z;5
Control ClusterNumber of the cluster containing the control run.
Deterministic ClustersNumber of the cluster containing the deterministic run.
- Showing all 3 values over the course of 10 days forecast:
Information about specific clustersPlease note that cluster-specific parameters need a
cluster_selectparameter (see Cluster Selection ) to specify the cluster for which to display the information. The following information can be queried:
Ensemble MembersNumber of ensemble members grouped into the specific cluster.
Representative Ensemble MembersReturns the id of the ensemble member of the selected cluster that is considered representative for the cluster
Climatological RegimeClimatological weather regimes are computed for cold (October to April) and warm (May to September) seasons. Four patterns, consistent with those documented in the literature (see for example Michelangeli et al. 1995) are considered:
- a strong positive anomaly over the Greenland area, together with a trough elongating from the southwest to the northeast Atlantic Ocean
- an east-west dipole, [...] associated with a pronounced wave structure
- a trough centered over Iceland together with a small-amplitude positive anomaly in southern part of the domain
- a ridge in mid-Atlantic
Start TimeFirst time step of the clusters existence (in hours since model start)
End TimeLast time step of the clusters existence (in hours since model start)
Geopotential Height ClusterSince the grouping of the ensemble members into clusters is based on the geopotential height at 500hPa, that parameter can also be queried for each cluster
- Display the 2 meteorological values over course of 10 days forecast for the first cluster: