Monday 17 Nov 2014: The dynamical influence of eddy fluxes
Dr James Maddison - University of Edinburgh
Harrison 103 15:00-16:00
The interpretation of eddy fluxes is often complicated by the need to consider the presence of rotational fluxes. Since only the divergence of eddy fluxes play a direct dynamical role, these rotational fluxes, which may be very large, are dynamically inactive. It is therefore natural to attempt to extract an underlying ``divergent'' component of the fluxes. Unfortunately it is well known that such a decomposition is non-unique, and is subject to a boundary condition choice.
Here the decomposition of eddy potential vorticity fluxes is considered. The residual-mean quasi-geostrophic equations are used to select a unique boundary condition for the decomposition, and it follows that the potential associated with the divergent eddy PV flux has a clear physical interpretation. Mathematically this decomposition can be further shown to satisfy a key optimality property, yielding the divergent eddy PV flux with smallest possible norm.