Definition and measurement of dust aeolian thresholds

[1] Dust suspension and particle saltation threshold'' speeds were measured in an environmental boundary layer wind tunnel located at the University of California, Davis. The results indicate that dust suspension threshold speeds occur at substantially lower friction speeds than saltation threshold'' speeds. Many of the dust suspension threshold values are half of the saltation threshold'' values. For example, surface soils from the most erodible areas of Owens ( dry) Lake were tested in the wind tunnel, and we found that dust suspension thresholds varied from 50 to 75% of conventional saltation threshold'' values. Current regulatory models relying on visual threshold'' for estimating suspended dust may be incorrect and may lead to substantial underestimates of suspended material yield over large, expansive, erodible areas. Wind environments with average wind speeds at or around the saltation threshold'' speed values are especially susceptible to underestimation. Though this study focuses only on Owens ( dry) Lake soils, we believe that the witnessed effect will occur in any soil with an abundance of dust particles interspersed among sand-sized particles.