DEMETER Development of a European Multi-model Ensemble System for Seasonal to Interannual Prediction Just to remind you of the meaning of DEMETER  Tim Palmer Renate Hagedorn Francisco Doblas-Reyes

Outline Hindcast production  Summary of all models  Estimate of ERA-40 production • Verification  Automatic diagnostics on web  First multi-model results Just the outline…

Multi-model assessment Hindcast verification End users, applications DEMETER Hindcast production Multi-model assessment Hindcast verification Downscaling End users, applications ERA40 EU and WMO programmes Diagram to summarize the basic structure of DEMETER and its main components as well as the interactions with other projects. ERA-40 is used as starting point for the hindcast production, hindcast verification and downscaling. Together with the important part of the multi-model assessment all these moduls “feed” into the DEMETER endusers applications as well as to other EU and WMO programmes.

DEMETER: Hindcast production • 9 member ensembles, 6 month hindcasts, 4 hindcasts per year ERA-40 initial conditions SST and wind perturbations • Main focus: 1987-1998 (1969-1986) 09/86 ERA40 fluxes 11/86 Ocean model integration (strong relaxation to observed SSTs) No SST Pert No WP + SST Pert Overview slide showing the participating DEMETER model components as well as a summary of the way of producing the DEMETER hindcast. In DEMETER ERA-40 is used as atmospheric forcing for the ocean analysis which are used as ocean initial conditions for the coupled integrations. Furthermore ERA-40 is also used directly as atmospheric initial conditions for the coupled integrations. The 6-month long coupled DEMETER hindcasts start 4 times per year (Feb, May, Aug, Nov). Each hindcast consists of 9 ensemble members which are created in applying wind stress and SST perturbations in the way shown in the sketch. - SST Pert + SST Pert + WP - SST Pert - WP

DEMETER: Hindcast production ERA-40: 10 years and 7 months ECMWF: 10*4 + 2 = 42 hindcasts LODYC: 10*4 + 1 = 41 hindcasts UKMO: 9*4 + 2 = 38 hindcasts CNRM: 8*4 + 2 = 34 hindcasts MPI: 6*4 + 1 = 25 hc Diagram to show the status of the DEMETER hindcasts, archived in MARS. 5 models are currently running at ECMWF and archiving into MARS. The limiting factor for producing new hindcasts is mainly the ERA-40 production. Additionally CERFACS is running a version of ARPEGE coupled to OPA (slightly different version of the ocean model than Meteo France is using) and is going to archive the results into MARS soon. The official sixth DEMETER model (Italian partner INGV) is running their model in Rome. They have produced the first years and going to archive the results into MARS (hopefully) soon. 09/86 04/97 11/86 11/92 02/95 02/96 02/97

Estimate of ERA-40 Production Stream 2 Stream 3 Stream 1 Diagram to show a (rough) estimate of the expected ERA-40 production. Due to unexpected problems (mainly in the handling of satellite data) we are experiencing a non negligible delay in the production of ERA-40 reanalysis data. This in turn slows down the DEMETER production dramatically. In DEMETER it was intended to produce a continuous set of 30 years hindcasts (1969-1998). This is not very likely (or should we say impossible?) to be achieved until the official end of the project (March 2003). As this diagram is showing, the crucial gaps in the DEMETER period won’t be closed until late 2003. However, we are currently working on a very user friendly tool for the data distribution of the available data. It is envisaged (and very likely) that at the end of 2002 there will be a facility at ECMWF to download free (!) and online(!) monthly means of the DEMETER hindcasts. By the way, this facility is very likely to be used as well for a subset of ERA-40 data. Finally, we are very confident that the “GRIB problem” will be solved as well, as we are planning to give the choice to download GRIB or NetCDF data!

Verification System Bias Indices Deterministic Scores Probabilistic Scores Single vs. multi-model results Additionally to the production of the DEMETER hindcasts, an automatic verification system has been installed at ECMWF. In this verification system a wide range of diagnostics are calculated, ranging from basic Bias and anomaly indices, deterministic and probabilistic scores (ACC, RMSSS, ROC, Reliability, RPSS) up to summarizing comparisons of the single vs. multi-model results. All results are freely accessible via the public DEMETER website. www.ecmwf.int/research/demeter/verification

Bias Example of an entry to the web site.

Value Example of an entry to the web site.

Anomaly Correlation Coefficient Further example of the diagnostics produced with the automatic verification system. Shown is the anomaly correlation coefficient at the gridpoint level for precipitation, calculated on the basis of the 2-4 month hindcasts from 1987-1995 (starting dates May -> hindcast JJA). All individual models show a kind of similar structure of distribution of skill, though on the regional scale remarkable differences can occur (see e.g. differences over India, Caribean, West Africa). The multi-model, mostly, is able to pick up the feature of the “best model”.

Multi-model DEMETER hindcasts ACC for Niño3 SST for Multimodel, ECMWF, MetFr, MetOf, and LODYC Diagram to compare the multi-model (comprising ECMWF, Meteo France, Met-Office, and LODYC) results vs. single model skill. Shown is the anomaly correlation coefficient for Nino3 SSTs over the 6 months hindcasts from 1987-1994. From lead time 2 months onwards the multi-model results outperform all single model results.

Multi-model DEMETER hindcasts Tropical RPSS (JJA) for Multimodel, ECMWF, MetFr, MetOf, and LODYC SST Precipitation The PDFs of the RPSS calculated over the tropical region (+- 30 degree Latitude, 0-360 degree Longitude) for SST or precipitation shows a shift of the multi-model PDF towards positive values. This implies a reduction of cases with negative skill in the multi-model, which is demonstrated as well by the larger value of the average over the region (number on the top right in the plots).

Multi-model DEMETER hindcasts Value (Tropics, JJA) for Multimodel, ECMWF, MetFr, MetOf, and LODYC SST Precipitation Anom> Anom> Anom>0 Anom>0 Comparison of the potential economic value depending on different event thresholds shows the added value in case of the multi-model.

Summary 5 DEMETER models are archiving into MARS  Hindcasts from 1987 – 1996 are available  Full DEMETER data set (1969-1998) not available before end of 2003  free (!) online (!) data retrieval very likely to be installed and working at the end of 2002 Wide range of diagnostic plots freely accessible on the DEMETER web site: www.ecmwf.int/research/verification Just a summary… First results demonstrate value of multi-model approach