ALADIN was entirely built on the notion of compatibility with its « mother » system, IFS/ARPEGE.
It was, therefore, absolutely necessary to copy the organization of the code from one system to the other. The key words for this organization are :
Furthermore, the duality between ARPEGE (global with the possibility of variable resolution) and ALADIN (LAM), sharing the same grid-point dynamics and physics, is a formidable advantage for tackling the NWP challenges of the coming years at high resolution. For example, inside the two projects, advanced (variational) data-assimilation aspects have mostly been tackled in the global framework, while high-resolution aspects (non-hydrostatism) were explored in the LAM framework, always keeping open the possibility of transfer from one side to the other.
The strict application of the integration-flexibility-modularity-generality (IFMG) rule inside the ALADIN part of the work is now a rather well-established practice. Of course, the compatibility with IFS/ARPEGE complicates matters. There are, for instance, four types of ALADIN routine :
This complexity is especially penalizing for the crucial maintenance process, which is copied from the IFS/ARPEGE one, i.e. it is organized around « cycles » (fully validated releases every six to nine months). The help of ECMWF staff in solving these complex problems is gratefully acknowledged her
Newsletter 8, published on January 31st, 2017