A numerical study on dust devils with implications to global dust budget estimates

The estimates of the contribution of dust devils (DDs) to the global dust budget have large uncertainties because the dust emission mechanisms in DDs are not yet well understood. In this study, a large-eddy simulation model coupled with a dust scheme is used to investigate DD dust entrainment. DDs are identified from the simulations using various threshold values for pressure drop and vorticity in the DD center. A vortex-tracking algorithm is presented, which automatically detects and tracks vortices based on different pressure drop and vorticity criteria. The results show that DD dust lifting can be largely explained by convective turbulent dust emission. DD dust entrainment varies strongly between individual DDs even for similar atmospheric conditions, but the maximum emissions are determined by atmospheric stability. By relating DD emission and counts to the Richardson number, we propose a new and simple method to estimate regional and global DD dust transport. (C) 2016 Elsevier B.V. All rights reserved.