Current numerical weather prediction and climate models are largely based on legacy code, which is becoming more and more difficult to port and optimize for upcoming HPC architectures. The BMBF PreWarmWorld project aims at developing a blueprint describing how the modeling system ICON developed by the German Weather Service (DWD) and the Max Planck Institute for Meteorology can be rewritten to enable agile development and execution of coupled storm and ocean eddy-resolving simulations in a computationally diverse, fast-evolving exascale compute environment.

PreWarmWorld is tasked with the development of a software blueprint driven by scientific requirements focusing on modularization, interfaces and responsibilities. The expected outcome of the project will include the design of a software prototype of the blueprint, consisting of a gross refactoring of the existing ICON code to enable autonomous development of major computational components such as sub-grid scale atmospheric processes, land, or radiation. The prototype will demonstrate a performance portable and maintainable implementation of one major physical and one infrastructural component. During the project, an update of the software blueprint based on evolving best practices, hardware requirements and evaluation of initial implementation will be provided and further options for a software development management strategy alongside the actual software development will be discussed.

PreWarmWorld is concerned with improvements of the technical software infrastructure for the ICON model and related tools for the scientific use cases targeted by the upcoming WarmWorld projects. At the same time, the project will foster effective and scalable developments of the code base. As a result of the two-year PreWarmWorld project, the software blueprint and an initial implementation should be in place to yield more scalable development in the BMBF WarmWorld initiative.