Size Distribution and Number Density of Airborne Particles Near the Ground Level -- Vertical Distribution and Wind Speed Dependence

To enhance characterization of the propagation path of assorted Army electro-optical and electro-acoustic devices, a detailed understanding of atmospheric conditions near the ground surface is needed. This proposal concentrates on the effects due to the presence of airborne particles. The ground-level aerosol model currently implemented is rather crude and needs to be refined. In the proposed study, the generation of airborne particles from local soil sources will be investigated theoretically based on our understanding of turbulence diffusion and sediment transport processes. The results will allow us to evaluate the error in estimates of aerosol number density due to the negligence of the vertical gradient and wind dependence close to the ground. Building upon this theoretical framework, as well as field data assimilation, we will establish an aerosol model for the lower boundary layer that contains explicit functional dependence of the elevation and wind speed. The new aerosol model will be used for extinction and scatter computations, which will enable enhancement of the performance of optical and acoustic sensors in ground-level applications. The computation of extinction, visibility, transmission attenuation, target acquisition probability, image obscuration, and image resolution will be improved through more accurate estimation of the number density and size distribution of airborne particles along ground-level propagation paths.