In this work the parallel-in-time algorithm Parareal was applied to the ocean-circulation and sea-ice model FESOM2 developed by the Alfred-Wegener Institut (AWI). The climate model provides one time integration method and hence, the coarse and fine propagators were defined by time step width. The coarse method was executed at the CFL condition limit, while fine step-sizes where gradually refined. As a first assessment of the performance of Parareal a low-resolution test mesh was used with default settings provided by the AWI. An introduction to FESOM2 and the straightforward implementation of Parareal on the DKRZ cluster is given. The evaluation of numerical results for different simulation intervals and fine propagator configurations shows strong dependence on the simulation time and time step-size of the fine propagator. Increasing the latter leads to stagnation and eventually divergence of the Parareal algorithm.
翻译:在这项工作中,Alfred-Wegener Institute(AWI)开发的海洋环流和海冰模型FESOM2应用了平行时间算法Parareal。气候模型提供了一次性集成方法,因此粗糙和细微的推进器按时间步宽加以界定。粗糙方法在CFL条件限度内实施,而细步尺寸则逐步改进。作为对Parareal性能的第一次评估,在AWI提供的默认设置中使用了低分辨率测试网块。介绍了FESOM2,并在DKRZ组群中直接应用了Parareal。对不同模拟间隔和细细推进器配置的数字结果的评估显示,对精细推进器的模拟时间和时间梯度的高度依赖性。增加后者导致Parareal算法的停滞和最终差异。