A numerical study on dust devils with implications to global dust budget estimates
1, Yaping Shao2
1USDA-ARS Jornada Experimental Range, Las Cruces, NM, USA, 2Institute for Geophysics and Meteorology, University of Cologne, Cologne, Germany
The contribution of dust devils (DDs) to the terrestrial and martian dust budgets has large uncertainties, because DDs are subgrid systems in global models and the dust emission mechanisms in DDs are not yet well understood. In this study, a large-eddy simulation model coupled with a dust emission 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. 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 background 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. Based on this method and regional model data, we estimate that about 0.07 Tg yr-1 of dust are emitted by DDs in Australia. Compared to the total annual dust emission in Australia, the contribution of DDs to the overall dust budget is small. However, particular areas show well above-average DD activity. In those areas, DDs can become a major dust event type and can contribute significantly to the local and regional dust budgets.