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Spectral transforms in the cycle 46t1r1 of ARPEGE/IFS.
Article published on 12 February 2019

by Karim Yessad

 Abstract:

ARPEGE/IFS, ALADIN and AROME are spectral models, so this documentation has for purpose to describe the spectral transforms done. The present note has for aim to give a brief summary of the spectral method (how to compute Legendre polynomials, spectral transforms) and to describe parts of the code performing spectral transforms (organigramme).


 RESUME:

ARPEGE/IFS, ALADIN ET AROME SONT DES MODELES SPECTRAUX, EN CONSEQUENCE CETTE DOCUMENTATION A POUR BUT DE DECRIRE LES TRANSFORMEES SPECTRALES NECESSAIRES POUR PASSER DE L’ESPACE SPECTRAL VERS L’ESPACE POINT DE GRILLE. ON Y FAIT UN BREF RAPPEL DE LA METHODE SPECTRALE (COMMENT CALCULER LES POLYNOMES DE LEGENDRE ET LES TRANSFORMEES SPECTRALES). ON Y DECRIT LES PARTIES DE CODE FAISANT DES TRANSFORMEES SPECTRALES, AVEC FOURNITURE DE QUELQUES ORGANIGRAMMES.


 Contents:

  • 1/ Introduction.
  • 2/ Theoretical aspects.
  • 3/ Set-up routines.
  • 4/ Spectral transforms routines: the general routines (E)DIR_TRANS and (E)INV_TRANS.
  • 5/ Spectral transforms routines for general application.
  • 6/ Spectral transforms used in the model under routine STEPO and for specific applications.
  • 7/ Some distributed memory features.
  • 8/ Specific variables in modules and namelists.
  • 9/ Bibliography.

 Appendices:

  • A1/ Expression of the laplacian in spectral space (spherical geometry).
  • A2/ Computation of Gaussian latitudes and Gaussian weights (spherical geometry).
  • A3/ Computation of the normalized Legendre polynomials (spherical geometry).
  • A4/ Fair numbers between 1 and 50000 writing 2**(1+p) 3**q 5**r.


Version cycle 44 357.3 KiB / PDF

Version cycle 45 357.4 KiB / PDF

Version cycle 46 355.4 KiB / PDF

Version cycle 46t1 360.4 KiB / PDF

Version cycle 46t1r1 360.3 KiB / PDF