Aerosols-Climate Interactions: Development and Tests of a Dust Lifting Model

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Aerosols produce direct radiative forcing by scattering and absorbing solar and infrared radiation, and indirect radiative forcing by altering cloud processes. Since human activity has been causing significant increases in the concentration of atmospheric aerosols, it is extremely important to understand the effects of aerosols on climate. Understanding the role of natural aerosols and how they are influenced by humans is important to the quantification of aerosols' radiative forcing on climate. Recently found evidence suggests that dust electrification and the resulting electrical forces play an important role on dust lifting. This aerosol-climate problem is being addressed by developing a physically-based dust lifting model and using it to study the effects of electric forces on dust lifting and transport by regular wind-blown saltation, dust storms, and convective plumes and vortices. The model is the first to include dust electrification and the potentially important effects of electric forces on dust lifting. The model will be made available to the scientific community as soon as it is developed and tested.Electric fields as high as 100-200 kV/m have been measured in all types of natural dust lifting processes such as wind-blown saltation, dust storms and convective vortices. Laboratory research shows that these electric fields can directly lift soil particles from the surface. Calculations show that these electric fields can greatly reduce the threshold wind speed necessary to initiate saltation. Saltation is the process by which larger sand particles are moved by the wind and bounce on the surface, ejecting smaller dust particles into the air. Electrostatic effects may enhance this process. They are being measured in field and laboratory settings. These observations form the basis for including electrostatic effects in a parameterization for the dust lifting and transport by convective plumes and vortices in weather and climate simulation models. This dust flux parameterization includes the transport of both natural and man-made aerosols from the atmospheric surface layer up to the top of the convective layer.The research has several broader impacts on science and society. Besides studying an important scientific problem key to our understanding of global climate change, the dust lifting model and dust flux parameterization will be available to the scientific community for use in a wide variety of modeling contexts. An educational website is being developed with simple physical explanations of the formation of convective plumes, dust devils, and dust storms. This website compares weather phenomena on Earth and other planets. It will be expanded to include explanations of saltation, dust electrification, and the effects of electric forces on dust lifting. Finally, this research project will contribute to the training of a graduate student.