Comparisons of Numerical Aspects in POM and ROMS


Tal Ezer

Princeton University



Different numerical aspects have been evaluated through a comparison between the Princeton Ocean Model (POM) and the Regional Ocean Modeling System (ROMS). While both models aim at modeling coastal to basin-scale problems with similar horizontal and vertical grids and similar subgrid-scale parameterizations, their numerical algorithms, model configuration and code size are very different. Sensitivity studies with an idealized channel flow and a steep seamount configuration demonstrate how different time stepping algorithms, different advection schemes and different pressure gradient schemes may affect the solution and the cpu requirement. The computational efficiency and numerical stability of the two models were compared and quantified for a range of different time step choices. It is shown for example, that while the simpler Leap-Frog time stepping in POM is more stable for small time steps, the more sophisticated Predictor-Corrector time stepping in ROMS becomes more stable for large time steps.