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2 nd SRNWP Workshop on Short Range Ensemble Prediction Systems Bologna, 7-8 April 2005

The COSMO-LEPS system: recent developments and plans Andrea Montani, Chiara Marsigli and Tiziana Paccagnella ARPA-SIM. 2 nd SRNWP Workshop on Short Range Ensemble Prediction Systems Bologna, 7-8 April 2005. COSMO-LEPS (developed at ARPA-SIM). What is it?

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2 nd SRNWP Workshop on Short Range Ensemble Prediction Systems Bologna, 7-8 April 2005

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  1. The COSMO-LEPS system: recent developments and plansAndrea Montani, Chiara Marsigli and Tiziana PaccagnellaARPA-SIM 2nd SRNWP Workshop on Short Range Ensemble Prediction SystemsBologna, 7-8 April 2005 A.Montani; The COSMO-LEPS system: recent developments and plans 2nd Workshop on Short-Range EPS, Bologna, 7-8 April 2005

  2. COSMO-LEPS (developed at ARPA-SIM) What is it? It is a Limited-area Ensemble Prediction System (LEPS), based on Lokal Modell and developed within COSMO (COnsortium for Small-scale MOdelling, which includes Germany, Greece, Italy, Poland and Switzerland). Why? Because the horizontal resolution of global-model ensemble systems is limited by computer time constraints and does not allow a detailed description of mesoscale and orographic-related processes. The forecast of heavy precipitation events is still inaccurate (in terms of both locations and intensity) after the short range. A.Montani; The COSMO-LEPS system: recent developments and plans 2nd Workshop on Short-Range EPS, Bologna, 7-8 April 2005

  3. COSMO-LEPS project combine the advantages of global-model ensembles with the high-resolution details gained by the LAMs, so as to identify the possible occurrence of intense and localised weather events (heavy rainfall, strong winds, temperature anomalies, snowfall, …); generation of COSMO-LEPS in order to improve the Late-Short (48hr)to Early-Medium (120hr) range forecast of the so-called “severe weather events”. A.Montani; The COSMO-LEPS system: recent developments and plans 2nd Workshop on Short-Range EPS, Bologna, 7-8 April 2005

  4. LAM Nesting Ensemble Size Reduction COSMO LEPS approach Global Ensemble LAM members GCM members Representative Members Downscaling LAM Nesting Total Downscaling (BFA) Global Ensemble GCM members LAM members A.Montani; The COSMO-LEPS system: recent developments and plans 2nd Workshop on Short-Range EPS, Bologna, 7-8 April 2005

  5. The COSMO-LEPS suite @ ECMWFNovember 2002 – May 2004 3 levels 500 700 850 hPa 4 variables Z U V Q d+3 d+4 d d+5 d+1 d+2 d-1 5 Representative Members Driving the 5 Lokal Modell integrations oldest EPS oldest EPS Cluster Analysis and RM identification Cluster Analysis and RM identification 12 middle EPS 00 2 time steps youngest EPS 12 European area clustering period Complete Linkage COSMO-LEPS Integration Domain COSMO-LEPS clustering area A.Montani; The COSMO-LEPS system: recent developments and plans 2nd Workshop on Short-Range EPS, Bologna, 7-8 April 2005

  6. The COSMO-LEPS suite @ ECMWFsince June 2004 10 Representative Members driving the 10 Lokal Modell integrations (weighted according to the cluster populations) employing either Tiedtke or Kain-Fristch convection scheme (randomly choosen) 3 levels 500 700 850 hPa 4 variables Z U V Q d+3 d+4 d d+5 d+1 d+2 d-1 Cluster Analysis and RM identification Cluster Analysis and RM identification middle EPS 00 2 time steps youngest EPS 12 European area clustering period Complete Linkage • suite running every day at ECMWF managed by ARPA-SIM; • Δx ~ 10 km; 32 ML; • fc length: 120h; • Computer time provided by the COSMO partners which are ECMWF member states. COSMO-LEPS Integration Domain COSMO-LEPS clustering area A.Montani; The COSMO-LEPS system: recent developments and plans 2nd Workshop on Short-Range EPS, Bologna, 7-8 April 2005

  7. Operational COSMO-LEPS set-up • Additional products: • 1 reference run (ICs and 6-hourly BCs from the high-resolution deterministic ECMWF forecast) to assess the relative merits between deterministic and probabilistic approach (start at 12UTC; t = 120h); • 1 proxy run (ICs and 3-hourly BCs from ECMWF analyses) to “downscale” ECMWF information (start at 00UTC; t = 36h). Core products: 10 perturbed LM runs (ICs and 6-hourly BCs from 10 EPS members) to generate probabilistic output (start at 12UTC; t = 120h); A.Montani; The COSMO-LEPS system: recent developments and plans 2nd Workshop on Short-Range EPS, Bologna, 7-8 April 2005

  8. Dissemination to the COSMO community A.Montani; The COSMO-LEPS system: recent developments and plans 2nd Workshop on Short-Range EPS, Bologna, 7-8 April 2005

  9. Operational COSMO-LEPS vs Operational EPS “Friuli case” S.E. 153 5 RMs The youngest EPS A.Montani; The COSMO-LEPS system: recent developments and plans 2nd Workshop on Short-Range EPS, Bologna, 7-8 April 2005

  10. Operational COSMO-LEPSvs Operational EPS(Friuli case) probability maps – fc. range: +96h >20mm/24h >50mm/24h COSMOLEPS EPS 51 members A.Montani; The COSMO-LEPS system: recent developments and plans 2nd Workshop on Short-Range EPS, Bologna, 7-8 April 2005

  11. COSMO-LEPS ongoing activities EVALUATION OF THE METHODOLOGY with respect to: • ENSEMBLE SIZE REDUCTION • SUPER-ENSEMBLE SIZE • CLUSTERING SETTING (parameters, time range, areas) • impact of weighting • ADDED VALUE WITH RESPECT TO EPS OBJECTIVE VERIFICATION OF COSMO-LEPS • ADDED VALUE WITH RESPECT TO EPS • evaluated at different spatial scales • evaluated over different geographical regions • evaluated for two different convection schemes 2 related ECMWF Special Projects ongoing: • SPITLAEF in cooperation with UGM (for general research) • SPCOLEPS in cooperation with Meteo-Swiss (to improve the operational suite) A.Montani; The COSMO-LEPS system: recent developments and plans 2nd Workshop on Short-Range EPS, Bologna, 7-8 April 2005

  12. 51 51 51 Ensemble Size Reduction Different Ensemble reductions Lokal Modell Nesting 20 20 Ensemble Size Reduction Lokal Modell Nesting 10 10 Ensemble Size Reduction Lokal Modell Nesting 5 5 ENSEMBLE SIZE REDUCTION: Friuli case study set-up Lokal Modell Nesting 1 EPS Total Downscaling (BFA) 51 51 A.Montani; The COSMO-LEPS system: recent developments and plans 2nd Workshop on Short-Range EPS, Bologna, 7-8 April 2005

  13. ENSEMBLE SIZE REDUCTIONIMPACT EVALUATED ON CASE STUDIES (1) A.Montani; The COSMO-LEPS system: recent developments and plans 2nd Workshop on Short-Range EPS, Bologna, 7-8 April 2005

  14. TP24h > 20 mm TP24h > 100 mm 2003082512 Friuli (fc+72-96h) 5 RMs 10 RMs All 51 A.Montani; The COSMO-LEPS system: recent developments and plans 2nd Workshop on Short-Range EPS, Bologna, 7-8 April 2005

  15. RMs vs ECMWF Proxy rain EVALUATION OF SUPER-ENSEMBLE (S.E.) SIZE & ENSEMBLE SIZE REDUCTION 1 EPS 51 members Ensemble Size Reduction 2 EPS 102 members Lokal Modell Nesting 10 10 RMs Ensemble Size Reduction 3 EPS 153 members Lokal Modell Nesting 5 5 RMs A.Montani; The COSMO-LEPS system: recent developments and plans 2nd Workshop on Short-Range EPS, Bologna, 7-8 April 2005

  16. EVALUATION OF S.E. SIZE (either 51, or 102, or 153) & ENSEMBLE SIZE REDUCTION (either 5 or 10 RMs) BSS outliers • Regarding the impact of the ensemble size, the difference between each 5-member ensemble and the correspondent 10-member ensemble is remarkable. The impact of doubling the ensemble size is almost the same for every configuration and is larger than the impact of changing the number of EPSs on which the Cluster Analysis is performed (either 2 or 3). • Regarding the 5-member ensembles, results seem to suggest that the use of just two EPSs in the super-ensemble can be a reasonable compromise, permitting to decrease the percentage of outliers significantly (with respect to the use of 1 EPS), “paying” only a small decrease of the skill. old suite new suite A.Montani; The COSMO-LEPS system: recent developments and plans 2nd Workshop on Short-Range EPS, Bologna, 7-8 April 2005

  17. TEST OF DIFFERENT CLUSTERING INTERVALS • Consider a fixed configuration in terms of ensemble size (10 RMs selected out of 2 EPS sets, 2eps-10rm) and the properties of the “reduced” (10-member) global ensemble in 4 different cases: • OPE: the 10 members are selected like in the operational set-up (clustering variables: z,u,v,q; clustering levels: 500, 700, 850 hPa; clustering times: fc+96h, fc+120h); • D2: like OPE, but clustering times: fc+24h, fc+48h; • D3: like OPE, but clustering times: fc+48h, fc+72h; • D4: like OPE, but clustering times: fc+72h, fc+96h. outliers BSS Brier Skill Score: OPE has slightly better scores at all verification ranges (less evident for ROC area .. not shown); Outliers percentage: results heavily depend on the verification range. A.Montani; The COSMO-LEPS system: recent developments and plans 2nd Workshop on Short-Range EPS, Bologna, 7-8 April 2005

  18. OBJECTIVE VERIFICATION OF COSMO-LEPS A verification package was developed keeping into account two measures of precipitation: • the cumulative volume of water deployed over a specific region, • the rainfall peaks which occur within that region. COSMO-LEPS (10 km) vs ECMWF EPS (80 km) COSMO observations The verification package includes the traditional probabilistic scores: • Brier Skill Score (Wilks, 1995) • ROC area (Mason and Graham, 1999) • Cost-loss Curve (Richardson, 2000) • Percentage of Outliers (Buizza, 1997) A.Montani; The COSMO-LEPS system: recent developments and plans 2nd Workshop on Short-Range EPS, Bologna, 7-8 April 2005

  19. COSMO-LEPS 5-MEMBER EPS 51-MEMBER EPS Precipitation: average over 1.5 x 1.5 boxes ROC area tp > 10mm/24h tp > 20mm/24h • As regards AVERAGE precipitation above these two thresholds, EPS wins. • Worsening due to the ensemble-size reduction. • Positive impact of LM downscaling. SON 2003 A.Montani; The COSMO-LEPS system: recent developments and plans 2nd Workshop on Short-Range EPS, Bologna, 7-8 April 2005

  20. COSMO-LEPS 5-MEMBER EPS 51-MEMBER EPS maximaover 1.5 x 1.5 boxes ROC area tp > 20mm/24h • COSMO-LEPS is more skilful than EPS in forecasting correctly high precipitation values over a rather large area. Number of occurrences: 600 (20 mm threshold) and 150 (50 mm). tp > 50mm/24h SON 2003 A.Montani; The COSMO-LEPS system: recent developments and plans 2nd Workshop on Short-Range EPS, Bologna, 7-8 April 2005

  21. Main results • Experimental-operational suite running at ECMWF since November 2002 over Central and Southern Europe. • Products delivered on a daily basis to National and Regional Weather centres. • Positive impact of COSMO-LEPS with respect to EPS in forecasting precipitation maxima; • Good performance of the ensemble size reduction technique (on case studies); • the use of 2 EPSs and 10 RMs seems to be the “best” configuration. A.Montani; The COSMO-LEPS system: recent developments and plans 2nd Workshop on Short-Range EPS, Bologna, 7-8 April 2005

  22. Future plans • COSMO-LEPS suite as “time-critical” application at ECMWF: • stronger involvement of ECMWF in the operational management of the system (+ MARS archiving of COSMO-LEPS products). • Participation to EURORISK-PREVIEW project: • integration domain will be enlarged to include Northern Europe; • clustering on different areas will be tested to focus better on different scenarios (Central-North & Central-Mediterranean). • Participation to MAP D-PHASE project: • further downscaling (around 2 km hor. res.) on specific areas where severe events are likely to occur (→ methodology to be evaluated also for TIGGE); • introduction of model perturbations to reveal uncertainty on smaller scales. • Test “Alpine” suite. • Carry on tests on clustering (impact of different time ranges and different variables). • Verification will be further developed → new variables verified. A.Montani; The COSMO-LEPS system: recent developments and plans 2nd Workshop on Short-Range EPS, Bologna, 7-8 April 2005

  23. Thank you ! A.Montani; The COSMO-LEPS system: recent developments and plans 2nd Workshop on Short-Range EPS, Bologna, 7-8 April 2005

  24. COSMO-LEPSReal time products A.Montani; The COSMO-LEPS system: recent developments and plans 2nd Workshop on Short-Range EPS, Bologna, 7-8 April 2005

  25. COSMO-LEPS vs ECMWF 5 RM detscores average on 1.5 x 1.5 boxes false alarm rate observed forecast A.Montani; The COSMO-LEPS system: recent developments and plans 2nd Workshop on Short-Range EPS, Bologna, 7-8 April 2005

  26. ENSEMBLE SIZE REDUCTIONIMPACT EVALUATED ON CASE STUDIES (2) Observed precipitation between 15-11-2002 12UTC and 16-11-2002 12 UTC Piedmont case A.Montani; The COSMO-LEPS system: recent developments and plans 2nd Workshop on Short-Range EPS, Bologna, 7-8 April 2005

  27. 20 mm 150 mm 2002111212 Piedmont(fc+72-96) 5 RMs 10 RMs All 51 A.Montani; The COSMO-LEPS system: recent developments and plans 2nd Workshop on Short-Range EPS, Bologna, 7-8 April 2005

  28. Main results • Positive impact of COSMO-LEPS with respect to EPS in forecasting precipitation maxima; • good performance of the ensemble size reduction technique (on case studies); • the use of 2 EPSs and 10 RMs seems to be the “best” configuration; and (not shown): • no positive impact of the weighting procedure as regards high resolution precipitation; • no relevant impact when using either Tiedtke or Kain-Fritsch convection scheme; • differences in the scores computed in different areas (results still too preliminary but supporting the idea that Limited Area Ensemble System set-up should be designed taking into account the features of each area). A.Montani; The COSMO-LEPS system: recent developments and plans 2nd Workshop on Short-Range EPS, Bologna, 7-8 April 2005

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