E4.6 Improving MPAS-O Time-Stepping Algorithm

Abstract

Ocean models permit a wide range of time scales with the speed of surface gravity waves being ~100 m/s while that of the surface currents and internal gravity waves being two orders of magnitude less. It is not practical to advance the full 3D momentum equations with the smallest time step corresponding to the fastest waves due to the computational weight of the problem. So, a traditional approach is to split the momentum equations into two parts, a barotropic part for solving the depth independent fast 2D barotropic waves and a baroclinic part for solving the much slower 3D baroclinic waves. My research involves improving this barotropic-baroclinic splitting of the time-stepping algorithm of the MPAS-Ocean model. In this poster, I am going to present a simple test case of a surface gravity wave propagation especially its evolution during the intermediate barotropic time steps. I will examine the influence of a couple of filters for time-averaging these intermediate instantaneous barotropic solutions and arriving at a 'mean' solution to be included in the tendency for the next baroclinic (large) time step. The effects of different time-stepping schemes will also be considered in this study.