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Tuesday 19 Oct 2021Tornado-like Vortices in Coriolis-Centrifugal Convection

Dr. Susanne Horn - Centre for Fluid and Complex Systems, Coventry University

Harrison 101 13:30-15:30

One of the most important mechanisms to generate turbulence in stars, in planetary interiors and in the atmosphere is rotating thermal convection. However, rotation has traditionally only been considered in terms of the Coriolis force, arguing that the centrifugal force is negligible in natural systems. But in doing so, one misses out on fascinating physics. In Coriolis-centrifugal convection, i.e. when the full inertial term is included, storm-like structures can develop, ranging from eyes and secondary eyewalls found in hurricanes and typhoons, to concentrated helical upflows characteristic of tornadoes.

In this talk, I will mainly focus on the tornado-like vortices. I will show that turbulent Coriolis-centrifugal convection in a cylindrical domain constitutes an idealised model system of tornadic storms, where the rotating cylinder represents the mesocyclone of a super- cell thunderstorm. Based on a suite of direct numerical simulations, I will discuss possible explanations for why seemingly similar mesocyclones may or may not spawn tornadoes. Tornado-like vortices are self-consistently generated, provided the flow is within the quasi-cyclostrophic regime, in which the dominant dynamical balance is between pressure gradient and centrifugal buoyancy forces. Hence, centrifugal buoyancy is highly relevant for the understanding of these geophysical vortices and more important than previously thought.

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