Abstract

A thermal is a convective structure generated from a localized buoyancy anomaly, say, released from the surface. Since it evolves into a donuts-shaped vorticity, the vortex ring, it may be more precisely called the thermal vortex ring. Thermals are often considered basic elements of fully-developed convection in astrophysical and geophysical flows, as most vividly visualized by a cauliflower-like structure of cumulus-convective clouds. This talk revisits the problem of the thermal vortex ring from a point of view of the vortex dynamics. More specifically, I present: 1) a modon solution of a thermal vortex ring as an extension of Hill’s vortex; 2) a concise description based on the volume integrals of the vorticity weighted by a power of the distance from the vortex-ring axis; 3) derivation of a classical similarity solution based on it, as well as 4) a development of a closed system based on an explicit simulation. Those investigations as a whole suggest that the thermal vortex ring could be interpreted as a type of two-dimensional turbulence.