1. Preliminary test for the development of a 2.8km ensemble over Italy
Chiara Marsigli, Andrea Montani, Tiziana Paccagnella
ARPA-SIMC, Bologna, Italy
Servizio
IdroMeteoClima

2. Outline Aim of the work Description of the ensemble
The meteorological events
Results
Hymex implementation
Future plans

3. Aim of this work
Study the impact of initial state and boundary condition perturbations from global models
Study the impact of model perturbations at 2.8km
Have a reference ensemble against which comparing future developments

4. The 7 km ensembles
COSMO-LEPS: initial and boundary conditions from 16 members selected from the ECMWF EPS
COSMO-SREPS: initial and boundary conditions from 3 operational global models (IFS, GME, GFS) -> 16 members
Parameter perturbations applied to the 7km COSMO runs

5. The convection-permitting ensemble
COSMO model run at 2.8km, 45 levels
Downscaling of COSMO-LEPS and COSMO-SREPS 7km ensembles, providing IC and BCs perturbations
Model perturbations applied to COSMO run at 2.8 km (perturbed parameters)

6. The meteorological events
Liguria Cinque Terre - 25/10/2011
Genova – 04/11/2011

7. 25th October 2011

8. 2.8km ensemble on COSMO-LEPS i.t. 24/10/2011 12UTC +12-36h50
100
200
1500 1

9. Probability of tp>100mm/24h
24h observed precipitation – 25/10/2011
ens 24/10 12UTC h 10 30 60 90
100
ens 23/10 12UTC h
best member ens 24/10 12UTC h

10. Probability of tp>100mm/24h - 25/10/2011 00UTC +24h
COSMO-SREPS (7km)
2.8 km ensemble on COSMO-SREPS 10 30 60 90
100
24h observed precipitation – 25/10/2011

11. IFS driven
tp24h distribution m1 m2 m3 m4 m5
m16

12. GME driven
tp24h distribution m6 m7 m8 m9
m10

13. GFS driven
tp24h distribution
m11
m12
m13
m14
m15

14. Verification 25/11/2011 00UTC +24h nearest point average 0.2 x 0.2
maximum 0.2 x 0.2

15. 4th November 2011

16. 2.8km on COSMO-SREPS i.t. 04/11/2011 00UTC +24h10 30 60 90
100
24h tp 04/11/11
prob tp>100mm/24h 10 50
100
200
1500 1
IFS driven
GME driven
GFS driven
7km
2.8km

17. tp 24h distribution - 04/11/2011 00UTC - member 1
7km
2.8km

18. Summary of the results
Some gain in skill from simple downscaling of the 7km ensembles at 2.8km
Significant dependence of the small-scale precipitation structure on the driving model (influence of large scale perturbations)
Strong impact of the error of the model run at high resolution -> importance of the modelisation of the small-scale phenomena
“reasonable” effect of the parameter perturbations

19. Hymex implementation Hymex SOP: 6th Sept – 5th Nov 2012
Many models available, among which AROME-EPS 2.5km
Many observations available (and many deployed on IOPs)
COSMO-H2-EPS set-up:
2.8 km, 50 levels
10 members
IC and BC COSMO-LEPS
1 run daily at 12 UTC
36h forecast range

20. Plans Provide IC perturbations based on KENDA to the 2.8km ensemble
Re-run the ensemble on the Hymex period with the perturbed ICs (use of high density observations)
Test the perturbation of the physics tendencies in the 2.8km ensemble
Implement a suite over an italian domain