Sphere to sphere transforms in spectral space in the cycle 46t1r1 of ARPEGE/IFS: configuration 911.

This documentation describes configuration formerly numbered 911 which performs dilatation/contraction matrices: these matrices allow to do spectral transformation between a stretched spectral space and between its unstretched counterpart. Some algorithmic aspects and technical aspects are described. Some namelists are provided to use the configuration 911, which is now externalised in the project UTILITIES. Such transformations can be used in spherical geometry only, and for METEO-FRANCE purpose only (not at ECMWF).

CETTE DOCUMENTATION DECRIT LA CONFIGURATION ANCIENNEMENT NUMEROTEE 911 QUI FABRIQUE DES MATRICES DE DILATATION/ROTATION. CES MATRICES PERMETTENT DE FAIRE DES TRANSFORMATIONS SPECTRALES ENTRE UN ESPACE SPECTRAL ETIRE ET SA CONTREPARTIE NON ETIREE. ON DECRIT QUELQUES ASPECTS ALGORITHMIQUES ET TECHNIQUES. ON FOURNIT UN EXEMPLE DE NAMELIST POUR UTILISER CETTE CONFIGURATION, QUI EST MAINTENANT EXTERNALISEE DANS LA LIBRAIRIE ``UTILITIES". CETTE TRANSFORMATION N’EST UTILISEE QU’A METEO-FRANCE.

• 1/ Introduction.
• 2/ Dilatation and contraction matrices.
• 3/ References.