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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.


Documents
Version cycle 42 367.7 kb / PDF

Version cycle 43 370.9 kb / PDF

Version cycle 44 357.3 kb / PDF

Version cycle 45 357.4 kb / PDF

Version cycle 46 355.4 kb / PDF

Version cycle 46t1 360.4 kb / PDF

Version cycle 46t1r1 360.3 kb / PDF