Preparing the weather and climate simulations community for ExaScale within ESiWACE3

In the framework of the European Center of Excellence in simulations for weather and climate ESiWACE3, one of the primary goals is to support modelers across Europe to optimally use HPC infrastructures. High fidelity weather and climate simulations are computationally expensive and produce a deluge of data which is often challenging to analyze. The high throughput of GPUs can be ideally suited to accelerate the simulation and distributed parallel data processing needed to perform statistical reductions on long time series of high-resolution model output. Meanwhile, careful consideration must be given to software sustainability and community engagement to strike a balance between performance and software sustainability. In this presentation, we focus on two examples: 1) GPU-acceleration of the Dutch Atmospheric Large Eddy Simulation (DALES) using OpenACC, which lead to a 5 to 10-fold speedup of the solver on multiple platforms (Nvidia and AMD) while maintaining a Fortran90 code base familiar to researchers; 2) performance optimization of ESMValTool, a community-driven package for evaluation and analysis of Earth System Model output, using distributed parallelism with Dask, achieving 10 times speedup for certain analysis workloads. These two examples showcase the benefits expert support can bring to the community in order to prepare the existing software infrastructure for the advent of ExaScale.