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-LEPSlate-short early-medium range (3-5 days)

LAM ensemble

boundary conditions

initial conditions

ECMWF EPS

“downscaling” ensemble

LM run

LM run

LM run

COSMO-LEPS suite at ECMWF (running from 5/11/2002, new suite from 5/2/2006)

d-1 d d+5d+1 d+2 d+4d+3

oldest EPS

youngest EPS

clustering period

00

12

Cluster Analysis + selection of 16 RMs

4 variables

Z U V Q

3 levels

500 700 850 hPa

2 time steps

European Area

Complete Linkage

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)

COSMO-LEPS

clustering area

• 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

Recent changes

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

COSMO-LEPS

10-MEMBER EPS

51-MEMBER EPS

tp > 10mm/24h

tp > 20mm/24htp > 20mm/24h

Maximum values - boxes 1.5x1.5 degtp > 10mm/24h

tp > 20mm/24h tp > 20mm/24h

tp > 10mm/24h

COSMO-LEPS

10-MEMBER EPS

51-MEMBER EPS

COSMO-LEPS

box size

MED 0.5

MED 1.0

MED 1.5

1mm/24h

10mm/24h

20mm/24hNew verification!

Research priorities

1. member representativeness in terms of precipitation (weighting problem)

2. addition of model perturbations

3. 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

(mm)

same cluster same cluster

different clustersdifferent clusters

“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).

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!

ope alp

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

LAM ensemble

boundary conditions

initial conditions

model (LAM):

parameters, schemes,

tendencies, surface forcing

Parameter list (COSMO)parameter name parameter description range default value usedPHYSICS

crsminminimal stomata resistance (part of 'terra'; sensible for much vegetation and not too dry soil [50,200] s/m 150 50, 200

c_soilsurface area index of the evaporating soil (part of 'terra'; sensible for less vegetation and not too dry soil ]0,c:lnd[ 0, clnd (=2)

plcovplant cover (part of 'terra' and 'turbtran'; controls transpiration) [0,1]

laileave area index (part of 'terra' and 'turbtran', controls transpiration) [0,10]

rlam_heat scaling factor of the laminar layer depth [0.1,50] 0.1, 50

c_difffactor for turbulent diffusion of TKE (may influence mixing at an inversion top) [0,2] 1 0, 2

pat_lenlength scale of thermal surface patterns (influences mixing in the stable stratified atmosphere) [0,10000] m 500 0, 10000

tur_lenmaximal turbulent length scale (influences mainly stratospheric mixing) [100,1000] m 1000

rat_canscaling parameter for the diagnosed canopy height (rather big influence on Td2m, but will be obsolete shortly) [0,10]

z0m_diaroughness length at a synop station (rather big influence on V10m, will very likely be obsolete in future) [0.05,0.5] m

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

clope30-36

>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

Courtesy of INM

UM LM 25 km

COSMO-SREPS (Short-Range Ensemble

Prediction System) short range (up to 3 days)

16 LM runs at 10 km

LM at 25 km on IFS

IFS – ECMWF globalb

y I

NM

Sp

ain LM at 25 km on GME

GME – DWD global

LM at 25 km on UM

UM – UKMO global

LM at 25 km on NCEP

AVN – NCEP global

P1

P2

P3

P4

4 different parameter perturbations (kept fix during the whole integration)

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)