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Limited-area ensembles using targeted SVs from ECMWF

Limited-area ensembles using targeted SVs from ECMWF. Inger-Lise Frogner Norwegian Meteorological Institute. Topics. Experiments using targeted SVs for perturbing HIRLAM (QJRMS (2002) 128 , pp 1321-1341) Targeted vs. not targeted perturbations Two case studies Summary/Plans.

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Limited-area ensembles using targeted SVs from ECMWF

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  1. Limited-area ensembles using targeted SVs from ECMWF Inger-Lise Frogner Norwegian Meteorological Institute

  2. Topics • Experiments using targeted SVs for perturbing HIRLAM (QJRMS (2002) 128, pp 1321-1341) • Targeted vs. not targeted perturbations • Two case studies • Summary/Plans

  3. Verification area Target area SVs Integration area HIRLAM

  4. SET-UP LAMTEPS • LAMTEPS - Limited Area Model Targeted Ensemble Prediction System • HIRLAM perturbed with targeted EPS from ECMWF (TEPS) • 48h optimization interval for TSVs. • HIRLAM analyses used • Two different approaches: • Perturbed ini. and boundary conditions (PB) • Perturbed only initial conditions (NP) • Test periods in June and Feb. 1997 • 28 km, 31 levels, 20+1 ensemble members

  5. Comparison of TEPS and operational EPS

  6. Thin lines: winter Heavy lines: summer

  7. THR = 20mm/24h TOTAL PRECIP. WINTER PERIOD Verification time: 40h TEPS LAMTEPS (PB) Verified against “superobservations”

  8. THR = 30mm/24h TOTAL PRECIP. WINTER PERIOD Verification time: 40h TEPS LAMTEPS (PB)

  9. TEPS LAMTEPS (PB) LAMTEPS (NP) THR = 2m temp. colder than -6K compared to climatology. WINTER

  10. TEPS LAMTEPS (PB) LAMTEPS (NP) THR = 2m temp. colder than -6K compared to climatology. WINTER

  11. TEPS LAMTEPS (PB) LAMTEPS (NP) THR = 2m temp. warmer than 4K compared to climatology. SUMMER

  12. TEPS LAMTEPS (PB) LAMTEPS (NP) THR = 2m temp. warmer than 4K compared to climatology. SUMMER

  13. Targeted vs. not targeted perturbations • Motivation: • TEPS perturbations initially small inside the HIRLAM integration area. • EPS perturbations more uniformly spread around the hemisphere • Two different approaches: • Perturbing using TEPS -> LAMTEPS • Perturbing using “operational” EPS -> LAMEPS • Test period in September 1999 (23 – 30) • Lateral boundary conditions perturbed

  14. EPS TEPS LAMEPS LAMTEPS THR = 15mm/24h TOTAL PRECIPITATION Verification time: 66h Autumn

  15. EPS TEPS LAMEPS LAMTEPS THR = 15mm/24h TOTAL PRECIPITATION Verification time: 90h Autumn

  16. Two case studies from Sept. 1999 with heavy precipitation • Case 1: 42 hours forecast from 30 September 1999 • Case 2: 42 hours forecast from 25 September 1999 • “super-observations” representative of the HIRLAM grid constructed (Ghelli and Lalaurette, 2000) • Kriging method used to obtain estimated area precipitation from point observations

  17. Case 1: 24h accumulated precipitation, valid at 2 October 1999 Analysis HIRLAM 50km (MSLP) L

  18. Observed 24h accumulated precipitation

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