ENVIRONMENTAL INFLUENCES ON DUST DEVIL GENERATION RATE, BASED ON FIELD STUDIES AT SMITH CREEK VALLEY, NEVADA, USA

Dust-laden vortices (i.e., dust devils) in the buoyantly unstable daytime convective boundary layer (CBL) of Earth and Mars are among the few visible markers of the structured turbulent eddies that comprise convective atmospheric motions. Because dust devil occurrence (and likely their spatial and temporal characteristics) is controlled by environmental conditions, their study has the potential to reveal much about patterns/modulation of convective structures and areas of enhanced dust lifting. This, in turn, has implications for the contribution of dust devils to the atmospheric mineral dust budget on both planets.

Field studies conducted at the Smith Creek Valley playa in June 2019 and 2021 produced a large dataset that includes time-lapse stereo observations of dust devils obtained simultaneously with meteorological measurements using a weather tower and ceilometer. These data have been placed in a mesoscale and synoptic context using observational data and the Weather Research and Forecasting (WRF) model.

Investigation of one of the clearest days (11 June 2019) reveals several factors influencing dust devil generation. Dust devil onset occurred at 10:22 local time, abruptly increasing in number to a peak from 10:45-11:30. Dust devil activity then decreased until 14:30, rose again to a second peak at 14:30-15:15, and then declined until the last noted occurrence at 18:03. The first peak in activity coincided with a sudden increase in both eddy heat flux and wind stress, as well as a jump in the CBL height. WRF results indicate that this abrupt shift is likely caused by the playa’s high albedo (~0.4), high thermal inertia (~1150 J m^-2 K^-1 s^½), and the nearby presence of standing water on the playa, which locally suppressed CBL growth until late morning. Both WRF results and ceilometer returns indicated the incursion of anomalously dry air ≥ 3 km above the ground that was entrained into the CBL from 12:00-14:00 – the weaker buoyancy of this air may have suppressed dust devil activity during this period. Dust devil generation at a given location thus appears to be highly sensitive to many factors, ranging from local surface properties to synoptic weather patterns. This highlights the need for similar studies conducted under a variety of environmental conditions to fully understand how dust devils form and loft dust.