AROME (Application of Research to Operational at Meso-Scale) model is a new NWP system built in order to improve the forecast of mesoscale phenomena and extreme weather events (thunderstorms, mountain forecasts, coastal winds, immediate forecasts). It is planned to be used operationally by the end of 2008 over mainland France. With a 2.5 km horizontal grid mesh and a time step of 60s, this model is designed for short range forecasts. It merges research outcomes and operational progress : the physical package used is extracted from the Meso-NH research model and has been interfaced into the Non-Hydrostactic version of the ALADIN software. AROME also has its own mesoscale data assimilation system based on 3DVar with a 3hours RUC (Rapid Update Cycle).

Physical parameterizations used in AROME are:

-the ICE3 Meso-NH microphysical scheme with 5 prognostic species of condensed water. It contains 3 precipitating species (rain, snow and graupel) and 2 non precipitating ones (ice crystals and cloud droplets)

-the Meso-NH 1D turbulence parameterization with Bougeault Lacarrere mixing lengths.

-the externalized version of the Meso-NH detailed surface scheme

-the operational ECMWF radiation code (called every 15 min).

-the KFB (Kein-Fritsch Bechtold) shallow convection scheme is also switched on.

We daily performed 30 hours forecasts with Non-Hydrostatic AROME 2.5 km model, starting from 00 TU. We ran with a time step of 60s over a domain of 400x320 points.AROME is coupled every 3 hours with ALADIN-France (ALADFR) 10km operational model. The post-processing in GRIB files is done on a regular LAT-LON Grid with a 0.025 degree resolution on a DPHASE domain (346x288 points), centered at 46.5N, 9.6E. This domain is smaller than the full DPHASE domain, and on the COPS domain (47-50 N, 6-11 E).

Grid description:

CDOM and DDOM:xinc/yinc:0.025 xnpole/ynpole:0.0

CDOM:xfirst:6.0 yfirst:47.0 xsize:202.0 ysize:122.0

DDOM:xfirst:5.2875 yfirst:42.9125 xsize:346.0 ysize:288.0