Freese, Jan PhilipJan PhilipFreeseGötschel, SebastianSebastianGötschelLunet, ThibautThibautLunetRuprecht, DanielDanielRuprechtSchreiber, MartinMartinSchreiber2025-12-172025-12-172025-12-13The International Journal of High Performance Computing Applications (in Press): (2025)https://hdl.handle.net/11420/60349We investigate the parallel performance of Parallel Spectral Deferred corrections, a numerical approach that provides small-scale parallelism for the numerical solution of initial value problems. The scheme is applied to the shallow-water equation and uses an implicit-explicit splitting that, in order to be efficient, integrates fast modes implicitly and slow modes explicitly. We describe parallel OpenMP-based implementations of parallel Spectral Deferred Corrections for two well established simulation codes: the finite volume based operational ocean model ICON-O and the spherical harmonics based research code SWEET. We also develop a performance model and benchmark our implementations on a single node of the JUSUF (SWEET) and JUWELS (ICON-O) system at Jülich Supercomputing Centre. A reduction of time-to-solution across a range of accuracies is demonstrated. For ICON-O, we show speedup over the currently used Adams–Bashforth-2 integrator with OpenMP loop parallelization. For SWEET, we show speedup over serial Spectral Deferred Corrections and a second order implicit-explicit integrator.en1741-28462025SAGENatural Sciences and Mathematics::510: MathematicsJournal Article10.1177/10943420251400406Journal Article