A Portable and Efficient Lagrangian Particle Capability for Idealized Atmospheric Phenomena

The Cloud Model version 1 is an atmospheric model that allows for idealized studies of atmospheric phenomena. A new Lagrangian microphysics capability has been added, enabling a significantly more accurate representation than the traditional bulk or multi-moment approaches frequently found in mesoscale atmospheric models. We have utilized a directive-based approach to enable a single source code to efficiently support execution on both CPU and GPU-based computing platforms. In addition to the use of accelerator directives, changes to the data structures and the message-passing approach used by the Lagrangian particle-based microphysics module were necessary to enable efficient execution for a large number of particles. We focus on a configuration that will be used to investigate the impact of oceanic sea spray on the atmospheric boundary layer within a hurricane. We observe a factor of 5.1× reduction in time to the solution when comparing the execution time for 256 NVIDIA A100 GPUs versus 256 AMD EPYC™ Milan-based compute nodes using 1 billion particles.