Coarse Dust Emissions From Dry Playas: The Dominant Role of Saltation Bombardment Over Aerodynamic Entrainment

In R1, six traps were deployed at mid-inlet heights of 0.025, 0.155, 0.325, 0.635, 1.155, and 2.175 m; corresponding heights in R2 were 0.025, 0.14, 0.415, 0.725, 1.255, and 2.275 m. To minimize mutual interference during rotation, traps at 0.155 m (R1) and 0.14 m (R2) were horizontally offset from the main array. Non-rotating traps at 0.025 m were set flush with the surface to capture near-bed saltation flux.

Saltation particle counts and kinetic energy profiles were measured using a vertical array of five Sensit H14-LIN impact sensors (1 Hz sampling rate) at geometric mean heights of 0.05, 0.12, 0.38, and 0.80 m, recorded with a Campbell CR1000 datalogger. Dust concentration profiles were monitored at 1 Hz using five DustTrak Aerosol Monitors (TSI Inc., model 8533EP) at heights of 0.2, 0.3, 0.6, 1, and 2 m (adjusted to 0.3, 0.6, 1, 2, and 3 m during two runs in R1 on 20240519).

The instruments measured mass concentrations (range: 0.001–150 mg·m⁻³) for PM₁₅, PM₁₀, PM₄, PM₂.₅, and PM₁. Units with elevated error during pre-campaign performance tests were excluded. All dust and saltation measurements were synchronized.

Instrument arrays were aligned orthogonal to the predominant sand-driving wind directions: ENE in R1 and WNW in R2. An inlet measurement point (N1) for dust emission rate using control volume method was constructed in the upwind of the main instrument array (N2) with a distance of 73.7 m. The R1 site extended approximately 94.5 m eastward from the toe of a barchan dune serving as a sand source.

Field campaigns captured two dust events (May 19th and 20th, 2024) in R1 and three in R2 (May 25th , 26th, and 27th, 2024).