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First Results from SLEPS

First Results from SLEPS. A. Walser, M. Arpagaus, C. Appenzeller, J. Quiby MeteoS wiss. SLEPS. SLEPS: Short-range limited-area ensemble prediction system. Within project ‘Extreme Events’ of the Swiss national research project NCCR.

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First Results from SLEPS

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  1. First Results from SLEPS A. Walser, M. Arpagaus, C. Appenzeller, J. Quiby MeteoSwiss

  2. SLEPS • SLEPS: Short-range limited-area ensemble prediction system. • Within project ‘Extreme Events’ of the Swiss national research project NCCR. • Strategy bases on an adapted COSMO-LEPS for the short-range. • Should be considered as a first step towards a short-range EPS. • The smaller scales resolved in SLEPS implies the consideration of alternative growth mechanisms beyond the baroclinic growth accounted for by the SV analysis.  Strategies for the definition of optimal small-scale perturbations have to be found. Andre.Walser@MeteoSwiss.ch COSMO General Meeting, 2003, Langen

  3. 12 n+2 12 n-1 12 n 12 n+1 12 n+3 12 n+4 12 n+5 00 00 00 00 00 00 day: SLEPS: Short-range adaptation of COSMO-LEPS Start of COSMO-LEPS integrations short-range clustering times COSMO-LEPS clustering times moist? EPS number of RMs? moist? EPS ? members horizontal resolution? moist? EPS Andre.Walser@MeteoSwiss.ch COSMO General Meeting, 2003, Langen

  4. SLEPS: current setup Global ECMWF EPS ensembles with moist singular vectors 50+1 members Hierarchical Cluster Analysis area: Europe fields: 4 variables (U,V,Q,Z) at 3 levels (500, 700, 850) for 3 time steps (24h, 48h, 72 h), number of clusters: fixed to 5 5 clusters Representative Member Selection one per cluster: member nearest (3D) to the mean of its own cluster AND most distant to the other clusters’ means Andre.Walser@MeteoSwiss.ch COSMO General Meeting, 2003, Langen 5 representative members (RMs) 5 Lokal Modell (limited-area) integrations nested into 5 RMs SLEPS: Short-range limited-area Ensemble Prediction System

  5. SLEPS: model domain with topography 10 km mesh-size horizontally, 32 vertical levels. Andre.Walser@MeteoSwiss.ch COSMO General Meeting, 2003, Langen

  6. Moist vs. operational singular vectorsCoutinho et al. (2003) • ‚opr‘ SVs (T42L31, OTI 48 h): linearized physics package with • surface drag • simple vertical diffusion • ‚moist‘ SVs (T63L31, OTI 24 h): linearized physics package includes additionally: • gravity wave drag • long-wave radiation • deep cumulus convection • large-scale condensation  moist SVs: use of moist processes during SV evolution, but same norm (‚total energy norm‘)  no humidity perturbations. Andre.Walser@MeteoSwiss.ch COSMO General Meeting, 2003, Langen

  7. 2 case studies: • Storm Lothar (“Christmas Storm”): 26 December 1999 • moist SV ECMWF EPS SLEPS 19991224 00 UTC, + 72 h • opr SV ECMWF EPS  SLEPS 19991224 00 UTC, + 72 h • Storm Martin: 27/28 December 1999 • moist SV EPS ECMWF SLEPS 19991226 00 UTC, + 72 h • opr SV EPS ECMWF  SLEPS 19991226 00 UTC, + 72 h Andre.Walser@MeteoSwiss.ch COSMO General Meeting, 2003, Langen

  8. RMSENS [m] Forecast time [h] Mean RMS error Z@850 hPa of ECMWF EPS to opr analysis in SLEPS domain y: predicted value o: values of analysis N: number of members I: number of grid points red: opr SVs EPS blue: moist SVs EPS solid: Storm Lothar dotted: Storm Martin Andre.Walser@MeteoSwiss.ch COSMO General Meeting, 2003, Langen

  9. Lothar Storm Lothar: probability forecast of SLEPS for 10 m wind gusts opr SVs moist SVs ECMWF opr analysis Andre.Walser@MeteoSwiss.ch COSMO General Meeting, 2003, Langen

  10. Lothar: 6 hours later… opr SVs moist SVs opr SVs Andre.Walser@MeteoSwiss.ch COSMO General Meeting, 2003, Langen

  11. Lothar: again 6 hours later… moist SVs opr SVs Andre.Walser@MeteoSwiss.ch COSMO General Meeting, 2003, Langen

  12. Lothar: again 6 hours later… moist SVs opr SVs Andre.Walser@MeteoSwiss.ch COSMO General Meeting, 2003, Langen

  13. Lothar: probability forecast for 10 m wind gusts over the 24 hours storm period moist SVs opr SVs Andre.Walser@MeteoSwiss.ch COSMO General Meeting, 2003, Langen • Both ensemble quite similar. • Moist SVs SLEPS predicts a higher risk for strong wind gusts over northern France.

  14. Lothar: ECMWF EPS using only LEPS representative members over the 24 hours storm period moist SVs opr SVs Andre.Walser@MeteoSwiss.ch COSMO General Meeting, 2003, Langen Rather reduced probabilities compared to SLEPS in particular over the Atlantic. SLEPS downscaling seems to be beneficial in this case.

  15. Lothar: ECMWF EPS using all 51 members over the 24 hours storm period opr SVs moist SVs Andre.Walser@MeteoSwiss.ch COSMO General Meeting, 2003, Langen Very similar  Effect of moist SVs not obvious.

  16. Martin Storm Martin: probability forecast of SLEPS for 10 m wind gusts moist SVs opr SVs Andre.Walser@MeteoSwiss.ch COSMO General Meeting, 2003, Langen

  17. Storm Martin: 6 hours later… moist SVs opr SVs Andre.Walser@MeteoSwiss.ch COSMO General Meeting, 2003, Langen

  18. Storm Martin: 6 hours later… moist SVs opr SVs Andre.Walser@MeteoSwiss.ch COSMO General Meeting, 2003, Langen

  19. Storm Martin: 6 hours later… moist SVs opr SVs Andre.Walser@MeteoSwiss.ch COSMO General Meeting, 2003, Langen

  20. Storm Martin: probability forecast for 10 m wind gusts over the 24 hours storm period moist SVs opr SVs Andre.Walser@MeteoSwiss.ch COSMO General Meeting, 2003, Langen • moist SVs SLEPS predicts a risk in south-western France and northern Mediterranean Sea. • opr SVs SLEPS misses the storm.

  21. Martin: ECMWF EPS using only LEPS RMsover the 24 hours storm period moist SVs opr SVs Andre.Walser@MeteoSwiss.ch COSMO General Meeting, 2003, Langen • Provided risk from moist SVs ECMWF EPS lower over southwestern France and northern Mediterranean sea. • Opr SVs ECMWF EPS also misses the storm.

  22. Martin: ECMWF EPS using all 51 members over the 24 hours storm period moist SVs opr SVs Andre.Walser@MeteoSwiss.ch COSMO General Meeting, 2003, Langen Using all EPS members, differences between moist and opr SVs EPS smaller  moist SVs SLEPS additionally favoured by the clustering procedure.

  23. Conclusions from first SLEPS simulations • Wind gust prediction for storm Lothar: • Effect of moist SVs in SLEPS and ECMWF EPS small. • Downscaling effect with SLEPS beneficial but not crucial. • Wind gust prediction for storm Martin: • Effect of moist SVs clearly positive both in SLEPS and ECMWF EPS. • opr SVs SLEPS does not provide a storm warning. • Downscaling effect with moist SVs SLEPS beneficial. Andre.Walser@MeteoSwiss.ch COSMO General Meeting, 2003, Langen

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