- Created by Helen Setchell on Dec 11, 2022
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Description of the upgrade
A new set of cluster products for the ENS has been introduced. The new system includes two applications of clustering methodology:
- A daily clustering of the forecast fields from the EPS, similar in principle to the old EPS clustering but using a different algorithm. The daily clustering determines weather scenarios, defined as the ensemble members closest to the centroid of each cluster.
- A set of fixed climatological regimes for each season, computed using 29 years of reanalysis data (ERA-Interim and ERA-40).
This combined approach provides the user with:
- a set of weather scenarios that appropriately represent the ensemble distribution
- an additional objective measure of the differences between scenarios in terms of large scale flow (by using the attribution of each weather scenario to the climatological regimes)
- easy computations of flow-dependent skill measures (under development)
The new products are computed on a new European domain (domain=H). For type cluster means they will replace the old products and a new type cluster representative (type=CR) will be added. Type cluster standard deviations will not be produced.
The new cluster products have been added to the Catalogue of ECMWF Real-Time Products Set III- Atmospheric Model low resolution 15-day forecast (ENS) on 8 Mar 2011.
The old cluster products have been discontinued on 6 Feb 2013.
Old cluster products
The old operational clustering algorithm is based on the RMS differences between the 500 hPa geopotential height ensemble forecasts, averaged from +120h to +168h taking the synoptic continuity into account.
The graphical products for the old clustering algorithm have been discontinued.
Products in GRIB code using local definition 2 are available from MARS and dissemination as follows:
The old cluster products have been discontinued on 6 Feb 2013.
The ENS cluster products replace the old Cluster means and introduce the new type Cluster representatives.
New cluster products
The new clustering method combines a daily clustering of ENS forecasts, similar in principle to the old ENS clustering, with a set of fixed climatological regimes for each season, computed from 29 years of reanalysis data (ERA-Interim and ERA-40). Weather scenarios derived from the daily clustering and defined as the ensemble members closest to the centroid of each cluster are called cluster representative members in MARS language (type=CR).
The new graphical cluster products are available for the time windows 72-96, 120-168, 192-240 and 264-360 hours.
Products in GRIB code using local definition 32 are available from MARS and dissemination as follows:
Note that the new products, based on 500 hPa geopotential, are computed in a new domain H (30°-75°N, 20°W-40°E).
Technical characteristics of the new cluster products
As the new products have been coded using local definition 32, they have to be handled with the following software versions:
- libemos 372 onwards
- grib_api 1.9.0 onwards
Implemented: 08 March 2011
Resolution
Unchanged
Contents of this page
All IFS cycles
- Terminology for IFS testing
- Implementation of IFS Cycle 49r1
- Implementation of IFS Cycle 48r1
- Implementation of IFS Cycle 47r3
- Implementation of IFS Cycle 47r2
- Implementation of IFS Cycle 47r1
- Implementation of IFS cycle 46r1
- Implementation of IFS cycle 45r1
- Implementation of Seasonal Forecast SEAS5
- Implementation of IFS cycle 43r3
- Implementation of IFS Cycle 43r1
- Implementation of IFS cycle 41r2
- Introducing the octahedral reduced Gaussian grid
- Horizontal resolution increase
- Boundary-Condition Programme ENS at 06 and 18 UTC
- Implementation of IFS Cycle 41r1
- IFS cycle upgrades pre 2015
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