The COSMO-LEPS system at ECMWF Chiara Marsigli, Andrea Montani, Tiziana Paccagnella ARPA-SIM, Bologna, Italy

Outline The Limited-area Ensemble Prediction System COSMO-LEPS Research priorities and system development LAM ensemble for the short-range: COSMO-SREPS COSMO-LEPS requirements

COSMO-LEPS late-short early-medium range (3-5 days) boundary conditions “downscaling” ensemble initial conditions LAM ensemble ECMWF EPS LM run LM run LM run

COSMO-LEPS suite at ECMWF (running from 5/11/2002, new suite from 5/2/2006) 16 Representative Members driving the 16 Lokal Modell integrations (weighted according to the cluster population) Random choice of the convection scheme (Tiedtke or Kain-Fristch) 4 variables Z U V Q 3 levels 500 700 850 hPa d-1 d d+1 d+2 d+3 d+4 d+5 oldest EPS Cluster Analysis + selection of 16 RMs 00 youngest EPS 2 time steps European Area Complete Linkage 12 clustering period Recent changes suite running daily at ECMWF managed by ARPA-SIM (ECMWF time-critical application); Δx = 10 km - 40 ML; forecast range: 132h; computer time (4 million BU in 2006) provided by the COSMO partners which are ECMWF member states archived on MARS COSMO-LEPS integration domain COSMO-LEPS clustering area

COSMO–LEPS verification (SON 2004) Verification grid COSMO-LEPS (10 km) vs EPS (80 km) over 4500 stations box included in scores if at least 10 obs fall in the box verification of the distributions

Average values - boxes 1.5x1.5 deg tp > 10mm/24h tp > 10mm/24h COSMO-LEPS 10-MEMBER EPS 51-MEMBER EPS tp > 20mm/24h tp > 20mm/24h

Maximum values - boxes 1.5x1.5 deg tp > 10mm/24h tp > 10mm/24h COSMO-LEPS 10-MEMBER EPS 51-MEMBER EPS tp > 20mm/24h tp > 20mm/24h

COSMO-LEPS box size New verification! 1mm/24h MED 0.5 MED 1.0 MED 1.5

Research priorities member representativeness in terms of precipitation (weighting problem) addition of model perturbations short-range ensemble => SREPS

1. Representativness (weighting problem) no evidence of better scores obtained by the weighted COSMO-LEPS against the not weighted one in terms of precipitation except in a subjective evaluation (ARPAL, D. Sacchetti) problem of representativeness in precipitation? too large clustering area?

ARPAL, D. Sacchetti

representativness Brute force (51 members) 12/11/2002 different clusters different clusters same cluster same cluster (mm) Brute force (51 members) 12/11/2002

“islands” Compute p1 and p2 percentiles of the whole precipitation field Identify an island starting from a point where p2 is overcome and extending until not going under the p1 value Compute an index defined as I=a*bs+(1-a)*(dpd-1) where bs is the rms distance between the island masks (a field =1 where there is an island and =0 otherwise) and dpd=(p1+p2)mi/(p1+p2)mj

ALPINE suite (SPCOLEPS billing units) Experimental suite running daily from 15 July 2005 Same configuration as the operational COSMO-LEPS (red), but both clustering and integration domain are centred over the Alps (blue). ope alp On single events, differences between the 2 suites can be noticeable. Prob maps of 3-day rainfall exceeding 50 and 100 mm (fc24-96h); forecast starting at 20050905 12UTC Objective verification on-going!

NW Europe suite (SPCOWIND billing units) Generation of a new limited-area ensemble forecast system for the prediction of wind and wind gusts over North-Western Europe (EURORISK-PREVIEW project, WINDSTORM) Aim: provision of site-specific wind forecasts to be post-processed and combined with other products by UK Met. Office. Same configuration as the operational COSMO-LEPS (red), but both clustering and integration domain are shifted northwards (blue). Experimental suite will start on June 2006

2. Addition of model perturbations boundary conditions initial conditions LAM ensemble model (LAM): parameters, schemes, tendencies, surface forcing

Parameter list (COSMO)

Test of a perturbed COSMO-LEPS vs operational COSMO-LEPS Operational system (COSMO-LEPS): b.c. and i.c. perturbations from 10 Representative Members selected out of 2 ECMWF EPS; use of Tiedtke or Kain-Fritsch random Perturbed system: addition of perturbations of the parameters of the model physics -> runtime perturbations Forecast range: +72h 10 members 09/04/2005 12UTC

clope 24-30 >10mm/6h >20mm/6h >30mm/6h >40mm/6h

clpert 24-30 >10mm/6h >20mm/6h >30mm/6h >40mm/6h

clope 30-36 >10mm/6h >20mm/6h >30mm/6h >40mm/6h

clpert 30-36 >10mm/6h >20mm/6h >30mm/6h >40mm/6h

Spread-skill

3. Short-range ensemble (SREPS) test the model perturbations on a short-range limited-area ensemble (same LAM model, same domain) using a multi-model approach for ic and bc if working, use model perturbations also in COSMO-LEPS

ic and bc: multi-model approach a MUlti-Model MUlti-Boundaries ensemble is operational at INM (Spain): 4 different limited-area models (HIRLAM, HRM, MM5, UM) are nested on 4 different global models (IFS, GME, AVN, UM) => 16 members ensemble (25 km horizontal resolution) from May 2006 LM has been added IFS LM 25km GME LM 25km AVN LM 25 km UM LM 25 km Courtesy of INM

IFS – ECMWF global COSMO-SREPS (Short-Range Ensemble Prediction System) short range (up to 3 days) LM at 25 km on IFS GME – DWD global LM at 25 km on GME P1 P2 P3 P4 4 different parameter perturbations (kept fix during the whole integration) by INM Spain UM – UKMO global LM at 25 km on UM 16 LM runs at 10 km AVN – NCEP global LM at 25 km on NCEP

ensemble spread 12/05 12UTC 13/05 00UTC 13/05 12UTC

Requirements 3-hourly post-processing of ECMWF deterministic run up to fc+144h (like EPS members) so that both the LMDET run and the COSMO-LEPS runs have boundary conditions every 3 h assistance so as to be able to interpolate on a regular lat-lon grid (using MARS at ECMWF) grib files produced on a rotated grid (like the COSMO-LEPS one)