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

2. SLEPS Andre.Walser@MeteoSwiss.ch COSMO General Meeting, 2003, Langen 1 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.

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

4. SLEPS Andre.Walser@MeteoSwiss.ch COSMO General Meeting, 2003, Langen 3 SLEPS: current setup 50+1 members 5 representative members (RMs) 5 Lokal Modell (limited-area) integrations nested into 5 RMs SLEPS: Short-range limited-area Ensemble Prediction System 5 clusters 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 Representative Member Selection one per cluster: member nearest (3D) to the mean of its own cluster AND most distant to the other clusters’ means Global ECMWF EPS ensembles with moist singular vectors

5. SLEPS Andre.Walser@MeteoSwiss.ch COSMO General Meeting, 2003, Langen 4 SLEPS: model domain with topography 10 km mesh-size horizontally, 32 vertical levels.

6. SLEPS Andre.Walser@MeteoSwiss.ch COSMO General Meeting, 2003, Langen 5 Moist vs. operational singular vectors Coutinho 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.

7. SLEPS Andre.Walser@MeteoSwiss.ch COSMO General Meeting, 2003, Langen 6 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

8. SLEPS Andre.Walser@MeteoSwiss.ch COSMO General Meeting, 2003, Langen 7 Mean RMS error Z@850 hPa of ECMWF EPS to opr analysis in SLEPS domain RMS ENS [m] Forecast time [h] red: opr SVs EPS blue: moist SVs EPS solid: Storm Lothar dotted: Storm Martin y: predicted value o: values of analysis N: number of members I: number of grid points

9. SLEPS Andre.Walser@MeteoSwiss.ch COSMO General Meeting, 2003, Langen 8 Storm Lothar: probability forecast of SLEPS for 10 m wind gusts moist SVs opr SVs ECMWF opr analysis Lothar

10. SLEPS Andre.Walser@MeteoSwiss.ch COSMO General Meeting, 2003, Langen 9 Lothar: 6 hours later… moist SVs opr SVs

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

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

13. SLEPS Andre.Walser@MeteoSwiss.ch COSMO General Meeting, 2003, Langen 12 Lothar: probability forecast for 10 m wind gusts over the 24 hours storm period moist SVsopr SVs  Both ensemble quite similar.  Moist SVs SLEPS predicts a higher risk for strong wind gusts over northern France.

14. SLEPS Andre.Walser@MeteoSwiss.ch COSMO General Meeting, 2003, Langen 13 Lothar: ECMWF EPS using only LEPS representative members over the 24 hours storm period moist SVs opr SVs Rather reduced probabilities compared to SLEPS in particular over the Atlantic.  SLEPS downscaling seems to be beneficial in this case.

15. SLEPS Andre.Walser@MeteoSwiss.ch COSMO General Meeting, 2003, Langen 14 Lothar: ECMWF EPS using all 51 members over the 24 hours storm period moist SVs opr SVs Very similar  Effect of moist SVs not obvious.

16. SLEPS Andre.Walser@MeteoSwiss.ch COSMO General Meeting, 2003, Langen 15 Storm Martin: probability forecast of SLEPS for 10 m wind gusts opr SVsmoist SVs Martin

17. SLEPS Andre.Walser@MeteoSwiss.ch COSMO General Meeting, 2003, Langen 16 Storm Martin: 6 hours later… moist SVsopr SVs

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

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

20. SLEPS Andre.Walser@MeteoSwiss.ch COSMO General Meeting, 2003, Langen 19 Storm Martin: probability forecast for 10 m wind gusts over the 24 hours storm period moist SVsopr SVs  moist SVs SLEPS predicts a risk in south-western France and northern Mediterranean Sea.  opr SVs SLEPS misses the storm.

21. SLEPS Andre.Walser@MeteoSwiss.ch COSMO General Meeting, 2003, Langen 20 Martin: ECMWF EPS using only LEPS RMs over the 24 hours storm period moist SVsopr SVs  Provided risk from moist SVs ECMWF EPS lower over southwestern France and northern Mediterranean sea.  Opr SVs ECMWF EPS also misses the storm.

22. SLEPS Andre.Walser@MeteoSwiss.ch COSMO General Meeting, 2003, Langen 21 Martin: ECMWF EPS using all 51 members over the 24 hours storm period moist SVsopr SVs Using all EPS members, differences between moist and opr SVs EPS smaller  moist SVs SLEPS additionally favoured by the clustering procedure.

23. SLEPS Andre.Walser@MeteoSwiss.ch COSMO General Meeting, 2003, Langen 22 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.