The Central European limited area ensemble forecasting system: ALADIN-LAEF
Central Institute for Meteorology and Geodynamics
The Central European limited area ensemble forecasting system
ALADIN-LAEF (Aire Limitée Adaptation dynamique
Développement InterNational – Limited Area Ensemble
Forecasting) has been developed at ZAMG in frame of the international
cooperation ALADIN/LACE. It runs with 16 perturbed members and in 18km
horizontal resolution. In the ALADIN-LAEF, two new ideas for dealing
with the initial uncertainties have been proposed. Those are: 1)
Blending method is used for perturbations to initial conditions by
combining the large scale perturbation generated by global Singular
Vector and the small scale perturbation generated by regional Breeding;
2) NCSB (Non-Cycling Surface Breeding) technique is employed for
perturbations to initial surface conditions.
In this talk, the idea of Blending, which is based
on the digital filter and spectral analysis for generation of initial
perturbation in regional EPS, will be presented in detail. The
performance of Blending will be compared with Breeding and dynamical
The lack or inadequate representation of
uncertainties in the initial surface conditions is quite known in the
ensemble forecasting. In the last few years, various approaches
are employed for dealing with the uncertainties that are related to the
initial state of the atmosphere, but hardly any methods for perturbing
the initial state of the land surface in the ensemble systems. In this
talk, the new strategy for perturbing surface initial conditions (NCSB)
will be discussed and evaluated.
The performance of the ALADIN-LAEF has been
evaluated by a comprehensive comparison with ECMWF EPS and a
verification against the operational deterministic forecast with higher
resolution for answering the questions:
What is the more added value of regional EPS to its counterpart global EPS?
Comparison between ALADIN-LAEF (16 perturbed members, 18 km resolution) and ECMWF EPS (50 perturbed members, 45 km resolution)
Is a regional EPS adding value to its existing
higher resolution deterministic Limited Area Model (LAM) forecast?
Comparison between ALADIN-LAEF and an ensemble system based on time
lagged higher resolution (9.6 km) deterministic LAM forecasts
The verification results will be shown in the talk too.