Variations in Dust Devil Characteristics Across Spatially Varying Terrain: Results from a Field Study in Smith Creek Valley, Nevada, USA

Dust devils (DDs) are dust-filled vortices that loft dust from the surface to the atmosphere in dry daytime convective conditions. Although they are a common sight in many arid regions on Earth, as well as Mars and possibly Titan, little is known about surface properties and atmospheric processes that influence the vortices’ dust-lofting capacity, thus limiting what is known about their contribution to the atmospheric dust budget. We present measurements of DD width, relative dustiness, and shape from a 1.67 h long data sample obtained during a field campaign conducted in Smith Creek Valley, Nevada USA. DDs were localized through stereogrammetric triangulation from time-lapse stereo images. A total of 245 individual DDs were found, consisting of 220 sequences and 25 solo instances. DDs translated downwind ~1.9 times faster than that of the 10 m mean wind speed, a ratio higher than that measured in previous studies. DD widths did not vary significantly over the study period, contrasting with various hypotheses regarding DD response to a growing convective boundary layer (CBL). Rather, the measured DD characteristics were most influenced by changes in surface properties, which varied considerably over the study area. Notably, DDs were most likely to broaden, increase in dustiness, and develop a coherent cylindrical shape as they traversed from a vegetated hummocky area onto a bare compact playa. Observed episodes of growth, dustiness, and coherence were limited to <~1 min periods that were often a small fraction of a DD’s lifetime. As a result, instantaneous observations of DDs should be used with caution when estimating size distributions and vertical dust fluxes. Finally, DD width measurements are dependent on instantaneous DD structure, which can vary considerably at timescales of seconds or less. Previous studies have used conflicting or unspecified criteria to make width measurements, affecting DD size statistics and estimations of vertical dust flux—both of which are necessary to determine atmospheric dust loading from DDs. In summary, we find that DD physical characteristics are more variable and more reliant on surface properties than have previously been reported.