The COSMOLEPS system at ECMWF

1
The COSMO-LEPS system at ECMWF

• Chiara Marsigli, Andrea Montani, Tiziana
  Paccagnella
• ARPA-SIM, Bologna, Italy

2
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

3
COSMO-LEPSlate-short early-medium range (3-5
days)
boundary conditions
downscaling ensemble
initial conditions
LAM ensemble
ECMWF EPS
LM run
LM run
LM run
4
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
d4
d3
d-1
d
d5
d1
d2
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)
• ?x 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
5
COSMOLEPS verification (SON 2004)

• 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

6
Average values - boxes 1.5x1.5 deg
tp gt 10mm/24h
tp gt 10mm/24h
tp gt 20mm/24h
tp gt 20mm/24h
7
Maximum values - boxes 1.5x1.5 deg
tp gt 10mm/24h
tp gt 10mm/24h
tp gt 20mm/24h
tp gt 20mm/24h
8
COSMO-LEPS box size
New verification!
9
Research priorities

• member representativeness in terms of
  precipitation (weighting problem)
• addition of model perturbations
• short-range ensemble gt SREPS

10
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?

11
ARPAL, D. Sacchetti
12
representativness
different clusters
different clusters
same cluster
same cluster
(mm)
Brute force (51 members) 12/11/2002
13
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
• Iabs(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(p1p2)mi/(p1p2)mj

14
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!
15
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
16
2. Addition of model perturbations
boundary conditions
initial conditions
LAM ensemble
model (LAM) parameters, schemes, tendencies,
surface forcing
17
Parameter list (COSMO)
18
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 -gt runtime perturbations
• Forecast range 72h
• 10 members

09/04/2005 12UTC
19
clope 24-30
gt10mm/6h
gt20mm/6h
gt30mm/6h
gt40mm/6h
20
clpert 24-30
gt10mm/6h
gt20mm/6h
gt30mm/6h
gt40mm/6h
21
clope30-36
gt10mm/6h
gt20mm/6h
gt30mm/6h
gt40mm/6h
22
clpert 30-36
gt10mm/6h
gt20mm/6h
gt30mm/6h
gt40mm/6h
23
Spread-skill
24
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

25
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) gt 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
26
COSMO-SREPS (Short-Range Ensemble Prediction
System) short range (up to 3 days)
IFS ECMWF global
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
27
ensemble spread
12/05 12UTC
13/05 00UTC
13/05 12UTC
28
Requirements

• 3-hourly post-processing of ECMWF deterministic
  run up to fc144h (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)