Ensemble activities in COSMO C. Marsigli, A. Montani, T. Paccagnella ARPA-SIM - HydroMeteorological Service of Emilia-Romagna, Bologna, Italy

Outline  COSMO-LEPS -> early medium range  5 year verification  re-forecasting (MeteoSwiss)  COSMO-SREPS -> short-range  error vs spread  role of the different perturbations  verification (HNMS, Greece)  future plans

The COSMO-LEPS ECMWF d-1 dd+5 d+1d+2 d+4d+3 older EPS younger EPS clustering period Cluster Analysis and RM identification 4 variables Z U V Q 3 levels hPa 2 time steps Cluster Analysis and RM identification European area Complete Linkage 16 Representative Members driving the 16 COSMO-model integrations (weighted according to the cluster populations) employing either Tiedtke or Kain- Fristch convection scheme (randomly choosen) COSMO- LEPS clustering area suite running as a ”time-critical application” managed by ARPA- SIM; Δx ~ 10 km; 40 ML; COSM0-LM 3.20 since Nov06; fc length: 132h; Computer time (4.3 million BU for 2007) provided by the COSMO partners which are ECMWF member states. COSMO- LEPS Integration Domain

5 year verification synop data - low density variable:12h cumulated precip (18-06, UTC); period:from Dec 2002 to Aug 2007; PHASE region:43-50N, 2-18E (MAP D-PHASE area); method:nearest grid point; no-weighted fcst; obs: synop reports (about 470 stations x day); fcst ranges: 6-18h, 18-30h, …, h, h; thresholds: 1, 5, 10, 15, 25, 50 mm/12h; both monthly and seasonal scores are computed. work is in progress for verification over the full domain (1500 stations)

Time series of Brier Skill Score fc. range 30-42h Jun04: 5m  10m Feb06: 10m  16m; 32ML  40 ML

Time series of Brier Skill Score fc. range 78-90h Jun04: 5m  10m Feb06: 10m  16m; 32ML  40 ML

Time series of ROC area Jun04: 5m  10m Feb06: 10m  16m; 32ML  40 ML fc. range 30-42h

Time series of ROC area Jun04: 5m  10m Feb06: 10m  16m; 32ML  40 ML fc. range 78-90h

Outliers: time series Jun04: 5m  10m Feb06: 10m  16m; 32ML  40 ML Theoretical value

COSMO-LEPS summer over the years

Comparison with EPS average maximum 95 th percentile MAM 2006 boxes

Comparison with EPS average maximum 95 th percentile h MAM 2006 boxes h

COSMO-LEPS Climatology Setup Reforecasts over a period of 30 years ( ) Deterministic run of COSMO-LEPS (1 member) (convective scheme = tiedtke) ERA40 Reanalysis as Initial/Boundary 42h lead time, 12:00 Initial time Calculated on hpce at ECMWF Archived on Mars at ECMWF (surf (30 parameters), 4 plev (8 parameters); 3h step) Post processing at CSCS Limitations Reforecasts with lead time of 42h are used to calibrate forecasts of up to 132h Only one convection scheme (COSMO-LEPS uses 2) New climatology needed with each model version change Building a climatology is slow and costly Currently only a monthly subset of the climatology is used for calibration (warning indices need to be interpreted with respect to the actual month) F. Fundel, A. Walser, M. Liniger, C. Appenzeller

Approach: fit a distribution function to the model climate (e.g. Gamma for precipitation) find the return levels according to a given return period find the number of forecasts exceeding the return level of a given return period Return Periods COSMO-PRP 2 PRP 1 = Event that happens once per September PRP 100 = Event that happens in one out of 100 Septembers Probability of Return Period exceedance F. Fundel, A. Walser, M. Liniger, C. Appenzeller

limited-area model error: schemes, parameters, surface forcings COSMO-SREPS  i.c. and b.c. perturbations -> INM multi-model multi- boundary (SREPS)  model perturbations -> parameter perturbation (fixed value throughout the integration to test the impact of the different parameter perturbations) LAM ensemble driving model error analysis error at the global model scale larger scale errors smaller scale errors

System set-up 16 COSMO runs 10 km hor. res. 40 vertical levels COSMO at 25 km on IFS IFS – ECMWF global by INM Spain COSMO at 25 km on GME GME – DWD global COSMO at 25 km on UM UM – UKMO global COSMO at 25 km on NCEP AVN – NCEP global P1: control (ope) P2: conv. scheme (KF) P3: tur_len=1000 P4: pat_len=10000

System applications  COSMO Priority Project -> Short-Range Ensemble  1D-Var DA of satellite data to provide retrievals to be nudged within 7km COSMO-I7: test of the use of COSMO-SREPS to estimate a flow-dependent B matrix  COSMO-SREPS provides boundary conditions for COSMO-DE-EPS, the 2.8 km ensemble system under development at DWD

Relationship between error and spread 12UTC runs Northern Italy observations Nearest grid point

intra-group distance 14 days (00UTC runs) 2mT whole domain

Daily precipitation - ROC area Northern Italy + Switzerland observations Average over 0.5 x 0.5 deg boxes - +42h fc range

Ensemble member verification Precipitation – mm / 6h IFS GME UKMO NCEP F. Gofa, P. Louka

Ensemble member verification Precipitation – mm / 6h Tiedtke, pat_len500 Kain-Fritsch, pat_len500 Tiedtke, tur_len1000, pat_len500 Tiedtke, pat_len10000 F. Gofa, P. Louka

On-going activities  COSMO-SREPS is running for the whole DOP MAP D- PHASE (6 months, June-November 2007)  test of different parameters (16 runs using only the IFS initial and boundary conditions): 3 month run IFS – ECMWF global P1: control (ope) P2: conv. scheme (KF) P3: parameter 1 P4: parameter 2 P5: …

Future plans  test perturbed parameters within COSMO-LEPS  possibility of using soil parameters from DWD  evaluate the benefit of a system calibration  MAP D-PHASE period runs:  statistical evaluation of the COSMO-SREPS system  verification  selection of the new parameters for COSMO-SREPS MAP D-PHASE: ensemble intercomparison!!!