Numerical simulation of dust devil-scale vortices

A high-resolution (2 m grid) large-eddy simulation of the convective boundary layer is performed for the purpose of comparing physical characteristics of simulated convective vertical vortices to those of observed dust devils. This study is a necessary part of a larger effort to examine the possible formation and maintenance mechanisms for vertical vortices in the convective boundary layer. The case of convective vertical vortex formation in environments without imposed mean winds or wind shears is considered in this paper. Simulated vertical vortices and observations of dust devils compare favourably overall. Other findings include the detection of ‘bookend’ vortex patterns embedded within the convergence branches of the simulated cellular convective pattern, which is different from prior results in which vortices were found only at cell vertices. Lastly, the theoretical Rankine and Burgers–Rott vortex models are compared to the simulated vortices. It is found that the Burgers–Rott model matches the high-resolution simulated vortex data better than the often used Rankine model.