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LAMEPS – Limited area ensemble forecasting in Norway, using targeted EPS

LAMEPS – Limited area ensemble forecasting in Norway, using targeted EPS. Marit Helene Jensen, Inger-Lise Frogner, Trond Iversen and Ole Vignes. Limited area ensemble forecasting in Norway - outline. Ensembles using Norway’s operational version of the HIRLAM model – LAMEPS

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LAMEPS – Limited area ensemble forecasting in Norway, using targeted EPS

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  1. LAMEPS – Limited area ensemble forecasting in Norway, using targeted EPS Marit Helene Jensen, Inger-Lise Frogner, Trond Iversen and Ole Vignes

  2. Limited area ensemble forecasting in Norway - outline • Ensembles using Norway’s operational version of the HIRLAM model – LAMEPS • Perturbing initial state and lateral boundary conditions with a dedicated version of EPS from ECMWF - TEPS • Combining these two systems gives NORLAMEPS • Main focus is precipitation, especially extreme precipitation events • Running storm surge from EPS,TEPS and LAMEPS

  3. TEPS – Targeted EPS • A dedicated version of ECMWF EPS. • 20 + 1 ensemble members, as opposed to 50 +1 for EPS • Target area Northern Europe and adjacent sea areas, as opposed to NH north of 30°N • Starts at 12 UTC every day • Runs to +72h, as opposed to +240h for EPS • T255L40(~80 km), Since Feb 1st: T399L62(~55 km)

  4. LAMEPS • HIRLAM in ensemble set-up • Quasi-operational at met.no since 14 February 2005 • 20 members + Control, • Control based on Norwegian HIRLAM analysis • 20 Initial and open boundary perturbations from TEPS • Starts at 18UTC every day (fresh HIRLAM analysis), i.e. a 6 hour delay compared to TEPS and EPS • Forecast Range: +60h • Resolution: 0.2 deg (20km), 40 levels

  5. NORLAMEPS • Combines simply IFS TEPS and HIRLAM LAMEPS • A simple multi-model, multi-initial-state ensemble • 41 + 1 ensemble members

  6. Verification area Target area for TEPS SVs Integration area HIRLAM

  7. Running TEPS to +72h 20 + 1 members Generation of perturbations ECMWF 12 UTC TEPS is automatically transferred to met.no TEPS is made ready to run in the Norwegian model environment ~22 UTC TEPS is transferred to Trondheim Generation of HIRLAM perturbations ~02 UTC Results from LAMEPS transferred back to met.no Generation of products for users/customers LAMEPS running 18 UTC, to +60h 50 minutes

  8. Reliability diagrams, percentiles - precip 80% 70% LAMEPS Norw. synop sites Sep05-April06 90% 95% Precip, + 12 - +36

  9. Reliability diagrams, percentiles -wind 70% 80% LAMEPS Norw. synop sites Sep05-April06 90% 95% Wind +24

  10. Verification of Precip. • Verify precipitation against “super-observations”. (Ghelli and Lalaurette): • All precipitation sites in Norway inside the verification area are aggregated using the method of Kriging • Distribution of precipitation in Norway is dominated by sharp gradients • We verify in sub-regions with grossly different precipitation climatology separately. • Inside each sub-region precipitation climatology is ”fairly” uniform

  11. Average annual precipitation amounts in Norway from 1961 – 90 (mm). 3 North 1 West 2 East

  12. Reliability diagrams, 20mm, 60h LAMEPS TEPS Annual Feb05-Feb06 NORLAMEPS EPS

  13. BRIER SKILL SCOREall three regions Annual Feb05-Feb06

  14. ROC and Value(C/L), all three regions5 mm/24h Annual Feb05-Feb06 LAMEPS TEPS EPS NORLAMEPS

  15. ROC and Value(C/L), all three regions20mm/24h Annual Feb05-Feb06 LAMEPS TEPS EPS NORLAMEPS

  16. Area under ROC-curveall three regions Annual Feb05-Feb06

  17. Rms error and bias errorof control forecast Jan.-April 2006 PRECIP.

  18. Spread around ensemble mean (Jan-Apr 2006)

  19. >90mm/24h 130mm/24h “100 year precipitation event” in the middle part of Norway 30-31. January 2006

  20. LAMEPS P24 > 50mm +12h - +36h TEPS P24 > 50mm +18h - +42h

  21. LAMEPS P24 > 60mm TEPS P24 > 60mm

  22. Future developments • Contribute to HIRLAM Ensemble Predictions (GLAMEPS) • Include perturbations of model physics in LAMEPS • Increase the time resolution of the boundary fields (now every 6 hour) • Develop a range of probability products • Compute meso-scale initial perturbations in HIRLAM-domain • Increase resolution (0.1 degrees or finer) • Non-hydrostatic downscaling

  23. Test LAMEPS on a new configuration for TEPS • A system that combines targeted SVs and hemispheric SVs (Martin Leutbecher, ECMWF) • 10 leading targeted singular vectors • 40 leading hemispheric singular vectors computed in the subspace orthogonal to the targeted singular vectors • Ensemble size 20 + 1 • Initial perturbations constructed with (revised) Gaussian sampling • Results in increased spread for TEPS after day 2, without increasing the error of the ensemble mean

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