Symmetric Stability of Vertical Baroclinic Vortices with a Warm Core

Abstract

An attempt has been made to relate the morphological characteristics of intense convective vortices, such as waterspouts and dust devils, to their hydrodynamic stability. The symmetric stability of cyclostrophically balanced vertical baroclinic vortices, whose radius of maximum wind depends on height, is considered. It shows the stability of narrow vortices, nearly cylindrical at the bottom, with a radius that then increases with height at an increasing rate and becomes infinite at a finite level above the Earth’s surface. On the contrary, wider conical vortices satisfy the necessary condition of instability, and it is hypothesized that this partly explains the more diffuse, disorganized nature of this kind of dust devils. The possibility of taking into account the general rotation in the problem is considered.