For achieving progress in weather and climate prediction it is crucial to overcome the performance wall for Earth-System model simulations at kilometre-scale spatial resolutions. This is not a matter of simply increasing computing power measured in theoretical floating-point operation rates. Addressing Europe's grand societal challenges such as climate change adaptation, especially under continued budgetary constraints for many European countries, it is imperative to identify, apply and implement flexible software engineering design principles for current and future weather and climate models.
Our vision is to implement the so-called separation of concerns, where domain science and multi-disciplinary abstractions are separated by a formal interface that facilitates rapid and simultaneous developments of the key weather and climate model algorithms together with hardware adaptation avoiding conflicting choices made in one or the other. This approach is orthogonal to the existing manual and inflexible code adaptation paradigm, and therefore moves far beyond the state of the art.
However, the separation of concerns also needs to build on a flexible framework so that scientific accuracy and numerical stability can be traded off against computational performance through viable mathematical or algorithmic choices. ESCAPE-2 achieves this by combining world-leading mathematical and algorithmic expertise in efficient forward-in-time computing to enhance algorithmic robustness and resilience to failure at scale, while minimizing time- and energy-to-solution for highly scalable, high-order algorithms, thus opening novel pathways for efficient use of future HPC architectures and providing a foundation for subsequent advances in scalability, and potentially time-parallelism. Eventually, this transformational research will be tested in a new class of weather and climate prediction community benchmarks, facilitating co-design and promoting a standardized, objective and widely accepted HPC hardware evaluation for this application domain.
ESCAPE-2 also combined research on an open-source, trans-disciplinary and (exa-)scalable VVUQ package, typically used outside the weather and climate community, with Earth-system modeling applications and associated uncertainty estimation expertise. This transfer aims to investigate the suitability of a simple package for higher-order and complex problems for which uncertainty quantification can presently only be done through very computing and data intensive simulations.
