CAREER: In Situ Study of Aerosols in the Coarse Mode With Digital Holography

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This study seeks to develop and apply new concepts in digital holography to obtain three-dimensional images of airborne particles, called "coarse mode aerosols" (CMAs). These aerosols are a major source of uncertainty for radiative impacts in climate models. The planned research will use a pioneering digital holographic design, developed by the PI, to measure various optical parameters of these aerosols. The associated education plan in this CAREER award will integrate hands-on teaching in a research lab setting and the development of online modules based on the planned research. The overall planned research and educational components seek to recruit underrepresented minority students and provide a unique learning opportunity in applied optics through the university's Expanding Diversity in Astronomy and Physics Program (ED-APP). This study seeks to establish a new characterization paradigm that is free from the drawbacks of conventional light scattering and can unambiguously describe CMA particle size and shape. Optical observables will be automatically measured, which include the angular scattering pattern, total cross sections and single scatter albedo. A series of digital holographic experiments will be used to image CMAs with particle sizes of the order of 1-300 microns. A new analysis method will then be used to quantify the particle size and shape distributions. From these measured particle holograms, accurate estimates of optical observables will be extracted. The goal of this research is to solve the inverse problem, by removing the long standing difficulty relating scattering measurements to particle properties. The study also seeks to correlate particle morphology with optical observables - of critical importance in many remote sensing applications. A portable version of the laboratory holographic instrumentation will be developed for field studies. The goal here is to apply the same techniques in urban and agricultural environments.