MPTRAC: Domain-decomposed Massively-Parallel Trajectory Calculations

Models for the calculation of Lagrangian particle dispersion in the atmosphere or the ocean are indispensable tools for understanding natural and anthropogenic processes. These processes range from volcanic ash clouds, through cloud microphysics to the study of the ozone layer on climate scales. With exascale machines at our disposal, such calculations can now be performed at significantly higher resolutions, both in terms of the driving wind field and particle number density.Massive-Parallel Trajectory Calculations (MPTRAC) is a library designed to enable Lagrangian particle dispersion analysis for atmospheric transport processes in the free troposphere and stratosphere. It is optimized for modern high-performance computing infrastructure. MPTRAC was developed with contemporary high-performance computing (HPC) systems in mind, ensuring high scalability across GPU and CPU clusters through an MPI-OpenMP/ACC hybrid parallelization approach. Its data structures are tailored to the multi-layered cache systems of modern compute nodes. MPTRAC is routinely executed on the JUWELS-Booster supercomputer and is planned for deployment on the JUPITER exascale machine.This contribution outlines ongoing developments in MPTRAC. A central aspect of the presented work is the implementation of domain decomposition, which partitions wind field data and associated tracer particles across distributed subdomains. This methodology promises to enhance computational efficiency and scalability, particularly in the context of large-scale atmospheric transport simulations. Furthermore, we detail the integration of MPTRAC with the ICON modeling framework through its community interface. This extension enables the direct application of particle-based transport methods within ICON, supporting high-resolution climate and weather simulations.The described developments are conducted within the scope of the WarmWorld Project, which aims to enable high-resolution calculations using ICON.MPTRAC is available under an open-source licence: https://github.com/slcs-jsc/mptrac