The electromagnetic-hydrodynamic analogy: an approach to vortex dynamics and preservation in tornadic simulations

A fundamental challenge to numerically simulating tornadoes is the tendency for models to over-produce turbulent diffusion in the vicinity of the vortex edge. While several methods have been developed to combat this numerical loss of kinetic energy (including ‘vortex confinement' and other antidiffusion methods), it seems desirable to find physical reasoning for this artificial enhancing of the vorticity (and energy) gradients.

There exists a growing body of literature examining the analogous relationship between the equations of electromagnetism (EM – Maxwell's equations) and hydrodynamics (HD – Navier-Stokes). In this presentation, we present a brief review of some of the more recent work using EM-HD analogies. Distilling from these various perspectives, a consistent, practical list of isomorphic variables is available for diagnostic use, aimed specifically toward atmospheric applications. We then invoke this “analogous thinking” to extend this EM-HD framework in order to explain two modes of self-organization observed to occur: self-alignment and upgradient merging of smaller-scale intense vortices into the main tornadic vortex. By merging the small-scale 'vortons' (from differing source regions) into the main vortex, the tornado is both strengthened and sharpened (see Tripoli and Büker, 2010, this conference). We examine these diagnostics in an idealized simulation, and then provide reasoning to support a physically-based, energy-conserving means of vorticity preservation, or ‘recycling', when simulating a tornadic environment.