An archive of convection-permitting limited-area model ensembles of European countries has been established at ECMWF, as part of the cooperation within the SRNWP–EPS (Short-Range Numerical Weather Prediction – Ensemble Prediction System) project of EUMETNET. The main goal of the SRNWP-EPS project is to foster and coordinate research and collaborations on limited-area model ensembles (LAM-EPS) to improve convection-permitting ensembles. The focus of these collaborations is on improved prediction of high-impact weather events (HIW) in the context of a European framework bringing together all European LAM-NWP consortia (ALADIN, HIRLAM, COSMO, LACE, Met Office partners, etc.).
ECMWF has been chosen for hosting the archive since it provides many facilities to access its archiving system (ECFS), which is accessible to all the SRNWP-EPS participants. Furthermore, ECMWF provides user support for its Member and Co-operating States, and access to all the necessary tools and support for archives and retrievals as well as other useful tools, such as clipping and re-gridding onto common overlapping areas and grid types.
Participants in the LAM-EPS archive
MOGREPS (UK Met Office)
MEPS (MetCoOp of the Finnish Meteorological Institute, Norwegian Meteorological Institute and Swedish Meteorological and Hydrological Institute)
γSREPS (AEMET – Spanish State Meteorological Agency)
IT-EPS (ItAF-REMET – Italian Air Force, Department of Meteorology)
IREPS (Met Éireann – Irish National Meteorological Service)
COMEPS (DMI – Danish Meteorological Institute)
RMI-EPS (RMI – Belgian Royal Meteorological Institute) – not running currently
ICON-D2-EPS (DWD – German Weather Service) – not yet archiving
The decision to create an off-line LAM-EPS database was proposed during the annual workshop of SRNWP-EPS in October 2019 by the Expert Team. The main requirements for this common, flexible set of archives are: i) complete domains to maximise overlapping; ii) GRIB format; iii) two daily cycles with all members; and iv) the most relevant near-surface meteorological parameters (see table). The archive was first set up to cover a three-month period (June–July–August 2020) plus some HIW selected cases.
At the time of writing, nine participants have agreed to archive their ensembles (see list). The first seven participants have already successfully archived the first three-month period. The figure shows and highlights the different domain locations and sizes of the LAM-EPSs.
The database will facilitate different research activities to be carried out: benefits of multi-model ensembles on ensemble spread, inter-comparison, diagnostic studies of physics perturbations, and case study analysis. At the last Joint EPS-Postprocessing Workshop in October 2020, it was decided that research groups with common domains and/or common research interests would coordinate their research activities and form sub-groups. Two main sub-projects were presented in the workshop. They are the first pieces of research using the database: a) the Met Office, Météo-France, DMI and Met Éireann identified 11 high-profile and difficult cases to test the value of using multi-model ensemble data; and b) Météo-France performed an ensemble verification inter-comparison between the French AROME-EPS and the UK’s MOGREPS-UK in their overlapping zone.
This EUMETNET SRNWP-EPS convection-permitting LAM-EPS database is a much-simplified continuation of the former TIGGE-LAM archive, with two main differences: the LAM-EPS is based on high-resolution (around 2.5 km) non-hydrostatic convection-permitting NWP models, and the archive has been set up only for European LAM-EPSs. The database has been made possible due to the very lively cooperation in the field of ensemble forecasting in Europe. Since 2013, EUMETNET has supported LAM-EPS cooperation through different phases. It formally started the SRNWP-EPS project in July 2015, where tasks dealing with ensemble calibration and post-processing are performed. On top of the plans for this research database, additional coordinated experiments aim to understand the behaviour of the different LAM ensembles, particularly with respect to model perturbations. Annual meetings offer the opportunity to exchange results and open new lines of research. The archive is aimed to be open to other EUMETNET projects, such as C-SRNWP, for verification, post-processing and nowcasting, and to the European and international research communities. For instance, a collaboration with the WMO HIWeather project is envisaged.
Main near-surface parameters archive
Pmsl Mean sea level pressure
Psurf Surface pressure
T2m Screen level temperature
T2mMAX and T2mMAX Daily maximum and minimum 2 m temperature
U10m and V10m The two components of 10 m wind
G10m Wind gust speed at 10 m
RH2m and/or Q2m Relative and/or specific humidity at 2 m
AccPcp Total accumulated precipitation from lead time 0
TCC Total cloud cover
Additionally, there are convection related parameters, such as hail and graupel, and constant ones, such as orography and land-sea mask.
A look to the future
The LAM-EPS database is being extended to archive continuously from 1 June of 2020 to 31 December 2023 (i.e. until the end of the current EUMETNET 2019–2023 third phase). On top of relevant surface variables, and fostered by the first research activities, a few isobaric vertical levels will be archived at the discretion of each centre to diagnose differences in upper-level forcings. These could drive on some occasions distinct LAM-EPS in a different way. It is expected that this database will keep on growing in the future, for instance by more European LAM-EPSs participating. Finally, other research activities are expected to take shape, such as common verification guidelines and benchmarking new LAM-EPS configurations to improve ensemble spread for HIW phenomena such as fog, storms, winter cases, etc.