Diagnosing Energy and Potential Enstrophy Transfers in Dynamical Cores of Gcms

Abstract:

The dynamical core of a GCM usually solves the governing fluid dynamics equations on a fixed grid. Due to the non-linearity of the equations there are transfers of energy and potential enstrophy between scales. This means that energy and enstrophy are transferred between the resolved scales (i.e. larger than the grid spacing) and the subgrid terms. It is important that the dynamical core can accurately model these transfers, as the effect of the subgrid terms can have a large impact on the resolved scale flow.

We investigate the energy and potential enstrophy transfers between the resolved and subgrid scales using both spectral and grid point analysis. The spectral analysis shows at which wave numbers energy and potential energy is being added to or removed from the resolved scale flow by the subgrid terms. The grid point analysis compares the dissipative effects of the diffusion in the model with the actual subgrid terms. As a first step we make use of simplified models solving the shallow water equations. We then extend this methodology to investigate atmospheric dynamical cores.