This paper was originally written by Mark Zagar, ever since updated by Claude Fischer with contributions by Gabor Radnoti, Martin Janousek and Alena Trojakova. The versions of December 2004 (al29t1), December 2006 (al32) are available.
The last version (al33) was prepared in December 2007 by Yann Seity.

It indeed aims at giving guidelines both for the pratical understanding and the detailed knowledge og the bi-Fourier limited area "patches" inside ARPEGE/IFS code.

This note focuses strongly on the features that are common to Arpege and Aladin in terms of functionality, but different in terms of actual coding.

Contents :
– duplicated routines
– physical (grid-point) space
– spectral transforms
– set-up
– modules, namelists, interfaces
– spectral space computations
– non-hydrostatic model
– observation operators
– input/output
– data distribution and parallelization