Proceedings - C-SRNWP Project

In Budapest, dynamical downscaling of ECMWF EPS with
• 10 clusters with representative members from 51 and then 102 EPS members,
clustering at +60h and 84h
• ALADIN integration: 84h
• Verification: 3 case studies (precipitation events)
has been done. The results show that on the basis of the first subjective and objective
evaluations of the ALADIN downscaling ECMWF EPS system, the ALADIN EPS
system in the examined limited number of cases could bring benefit on top of the global
ECMWF EPS system (Fig.8)
Fig. 8. ROC diagrams for 5mm/24h threshold for +66h forecasts calculated from the
first three case studies. Thick solid line is relative to ECMWF EPS (100 members),
dashed line is relative to ECMWF/ALADIN (10 representative members from the
100 global members, bigger domain), the diagonal line represents the climate. The
black dots represent the different probability thresholds. ROC areas: 0.6 (ECMWF
EPS); 0.77 (ECMWF/ALADIN).
2.4 Downscaling of ARPEGE EPS (by R. Mladek)
In Prag, evaluation of 18 cases with the largest model errors in precipitation forecast
over Czech republic from the period 2003-2006 has been started. It was found that no
real improvement in the recent studies related to the direct dynamic downscaling of
global EPS by the ALADIN with high resolution.
3. Conclusions and future plan
Within LACE works have been done for developing ALADIN LAMEPS (LAEF). Focuses
have been put on dealing with uncertainties in initial conditions, lateral boundary conditions
and model physics, Also the dynamical downscaling of global EPS system, like ECMWF and
ARPEG has been investigated. The results can be summarized as follows:
a. ETKF with 10 members has very similar performance to Breeding. It is also true for
ET perturbation. The reason is might be due to the small ensemble size.
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