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Operational Aladin-Belgium

Operational Aladin-Belgium. SGI Altix 3700 Bx2, 56 Itanium2 1.5 Ghz 6 Mbyte CPU’s Model version : AL29t2 Domain size : 240 x240 points Horizontal resolution : ~7km Number of layers : 46 Time step : 300 s ; 2-time level SISL advection scheme

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Operational Aladin-Belgium

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  1. Operational Aladin-Belgium • SGI Altix 3700 Bx2, 56 Itanium2 1.5 Ghz 6 Mbyte CPU’s • Model version : AL29t2 • Domain size : 240 x240 points • Horizontal resolution : ~7km • Number of layers : 46 • Time step : 300 s ; 2-time level SISL advection scheme • Forecast range 60h and 4 runs/day (0,6,12,18 UTC) • Lateral boundary conditions : Aladin-France and Arpege • LBC update : every 3 hours • Initialization : digital filter initialization • Hourly post processing

  2. Progress with the 3MT scheme in Alaro-0 • Alaro-0 was developed for operational forecasts at high resolution, with meshes between 10 and 2 km. • 3MT implements in Alaro-0 the package described by Gerard (2007) and ideas of Piriou • Tests have been performed at 9 and 4km resolution • The forecast at 4km, in the so–called grey zone of the convection, is consistent with the other scales.

  3. Monitoring the Coupling-Update Frequency • When a fast moving storm system crosses the border of a limited area model, the coupling frequency may be too low to capture this event adequately. An index has been developed to monitor the data loss due to the coupling. New approach to lateral boundary conditions • P. Termonia and F. Voitus propose an approach where the LBC’s are computed with a numerical finite-difference scheme that is different than the semi-implicit semi-lagrangian scheme of the dynamical core

  4. Including atmospheric layers in vegetation and urban offline surface schemes • A formulation to include prognostic atmospheric layers in offline surface schemes is derived from atmospheric equations. • Classic multi-layer surface schemes need complex coupling between atmospheric models levels and surface scheme levels • The proposed coupling remains simple because the atmospheric layers interacting with the surface scheme are independent of the atmospheric model that could be coupled above (Masson, 2007). • The Surface Boundary Layer (SBL) (both inside and just above the canopy) is resolved by a prognostic way, taking into account large-scale forcing, turbulence and, if any, drag and canopy forces and surfaces fluxes.

  5. Downscaling of the ERA-40 reanalysis • As a first approach, we opted for a double nesting strategy, with domain resolutions at 40 km and 10 km. • A third nesting at 2 km was also introduced, but this consisted only of a dynamical adaptation run (30' and limited physics) for a more detailed wind field (Zagar & Rakovec, 1999). This work is part of the ECMWF special project SPFRCOUP.

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