A maximum entropy parameterization for two-dimensional turbulence

B. Zwaal, Ministry of Infrastructure and the Environment, Royal Netherlands Meteorological Institute, University of Amsterdam
De Bilt : KNMI

In numerical weather and climate models, computational power limits their spatial resolution. This leads to a loss of accuracy, as subgrid, or unresolved, processes are left out of the description. To account for these unresolved processes, parameterization schemes are used to implicitly model the influence of the unresolved processes on the resolved processes. In this thesis, we test the performance of a maximum entropy parameterization scheme implemented in a two-dimensional fluid dynamical model. This maximum entropy parameterization is based on the information entropy of the unresolved scales and global constraints on their energy and enstrophy budgets. It requires no tuning as the formalism determines its dependence on the system parameters and the current state of the resolved scales. We diagnose this parameterization by studying the transfers of energy and enstrophy to and from the resolved scales due to the subgrid scales. We compare the maximum entropy parameterization with a conventional parameterization, in which the viscosity is increased to simulate the dissipation caused by the unresolved scales. Both the maximum entropy parameterization and the conventional parameterization are compared with a reference run, which is a simulation where both resolved and unresolved scales are computed explicitly.

59 p.
Fig., tab.
(Internal report ; IR 2016-02)
With a bibliogr.
Stageverslag De Bilt