The Lifting of Mineral Aerosols in an Arid Environment.

[摘要] Characterization of mineral aerosols in the atmosphere provides a steady foundation for evaluating the impact those aerosols have on radiative forcing and climate.Currently, the contribution of the effects of mineral aerosols is among the least understood components to global climate modeling.Here, we contribute to the knowledge of the processes that supply mineral aerosols into the atmosphere through novel instrumentation, a field study of dust ejection processes, and analysis of the unusual results of that field study.The process of saltation provides the basis for study of dust ejection from the surface.First, we develop an instrument for study of dust devils, a discrete phenomenon that initiates saltation and lifts ejected dust high into the planetary boundary layer.Measurements collected via this new instrumentation can provide valuable insights which allow for more accurate modeling of dust devils’ wind speeds and pressure perturbations, important variables for estimating the strength of saltation.Such dust devil models can provide a means of predicting the capability of a dust devil to eject mineral dust into suspension.We then study the ability of saltating soil grains to eject dust under changing environmental conditions, including various soil moisture and meteorological regimes, through a long-term field expedition to the Owens Lake salty playa.Measurements of friction velocity, soil moisture, meteorological conditions, and saltation strength via frequency of particle counts show a surprising trend of enhanced dust flux from saltation when environmental moisture increases.Indeed, observations suggest vertical flux of dust from the surface may be enhanced when soil moisture content increases.Finally, we analyze these unexpected results and present a theory for dust ejection in a salty playa that explains their occurrence and significance.The relationship between dust ejection and environmental moisture has wider implications for atmospheric dust modeling, as many of the world’s most significant mineral dust sources are, like Owens Lake, desiccated, salty, dry lake beds that may also display a tendency toward more intense dust ejection as more environmental moisture is available.

[发布机构] University of Michigan

[效力级别] Aerosol Studies

[关键词] Dust Lifting;Aerosol Studies;Saltation Physics;Atmospheric;Oceanic and Space Sciences;Science;Atmos, Oceanic & Space Sciences