High Resolution Numerical Weather Prediction Project
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The ARPEGE/ALADIN System travels overseas ...
Article published on 10 April 2012
dernière modification le 16 September 2013

by Patricia
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On March 27, 2012 (5860 days since its first pre-operational run; 5100 days since its first operational run), ALADIN-France completed its last operational run. Since that day, the ALADIN reference version at Meteo-France is the ALADIN-Réunion model, one of the 4 Overseas ALADIN models operational at Météo-France.

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Orography of ALADIN-France

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Post processing domains of the 4 overseas Aladin models ; background : a global tropical cyclone climatology map

Some general features of this last version of ALADIN-France :

  • It was based on ALADIN cycle CY36T1 and was run on Meteo-France Nec-SX9 computer.
  • The centre of the domain was located at 46.47°N; 2.58°E.
  • Computations were performed in spectral bi-Fourier space with elliptic truncation at wave number 199. The equivalent grid had 7.5 Km gridmesh (400x400 points). The vertical dimension was discretized in 70 levels.
  • During a forecast, ALADIN-FRANCE was coupled with ARPEGE every 3 hours.
  • The timestep was 450 s (thus, it had an even number of iterations for 1 hour).
  • 4 runs were performed operationally each day at 00, 06, 12 and 18 UTC. Forecast terms were 54H for the 00 UTC forecast, 48H for 06 UTC, 42H for 12 UTC and 36H for 18 UTC.
  • The assimilation scheme was 3D-Var with a 6H window.
  • A continuous “long cut-off” cycle provided the guess for a “short cut-off” production which provided the operationally used analysis.
  • Coefficients for variational bias correction (applied to satellite observations) were computed by ARPEGE.
  • The last but remarkable improvement was realized thanks to the introduction of SURFEX in ALADIN (with the same SURFEX options used as in AROME :ECOCLIMAP, ISBA-3L, etc except TEB scheme).

4 Overseas Aladin Models : some general features

  • 4 Aladin models with 3D Var assimilation, called Overseas Aladin models, are in operations over the following French territories : La Réunion, French Antilles and Guiana, New Caledonia and Polynesia
  • Computations are performed in spectral bi-Fourier space with elliptic truncation. The equivalent grid has 8 Km gridmesh, and the vertical dimension is discretized in 70 levels.
  • During a forecast, these models are coupled with a global model (ARPEGE or IFS depending on the domain) every 3 hours.
  • The timestep is 450 s to have an even number of iterations for 1h.
  • 2 runs are performed operationally each day at 00 and 12 UTC.
  • Forecast terms go from 54H to 84H depending on the domain.

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