A Study of Atmospheric Turbulence Effects on Dust Emission Using Field Data and One-Dimensional Stochastic Turbulence Model

Abstract:

Soil dust corresponds to the majority of aerosol particles in the atmosphere, and it plays an important role in radiative transfer and cloud formation, therefore impacting air quality, weather and climate. Dust is primarily emitted by the high-energy impact of larger, less cohesive particles on the soil surface, a process called saltation. Usually, the horizontal saltation flux is modeled as a function of the wind friction velocity, and the dust vertical emission flux is assumed to be a fraction of the saltation flux. In this study, field data collected over sand dunes and a reduced complexity numerical model of turbulence are combined to investigate the interaction between atmospheric turbulence and the process of dust emission. Simultaneous measurements of turbulence from six levels (from 0.5 to 9 meters above ground), dust concentration from four levels (from 0.75 to 6.5 meters) and sand saltation particle counters from nine levels (from 7 to 47 centimeters) are used. A one-dimensional stochastic turbulence model that simulates the time evolution of the atmospheric boundary layer column is used to evaluate different parameterizations of the saltation process as a function of the wind shear on the vertical profiles of dust concentration. The diurnal evolution of dust concentration profiles is then compared with field measurements. The saltation flux data is also used to evaluate the models and to estimate the dust flux directly. Effects of particle size, atmospheric stability and threshold wind speed on dust concentration are also investigated.