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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)