An Examination of a Continuous Flow Diffusion Chamber's Performance: Implications for Field Measurements of Ice Nuclei
Recent field studies using the aircraft version of the Colorado State University Continuous Flow Diffusion Chamber (CFDC) indicate that the kinetic aspects of diffusional growth (both of water and ice) and ice nucleation, coupled with the limited aerosol residence time in the chamber, may result in a delay in the detection of the onset of homogeneous freezing. Through a series of controlled laboratory studies, we confirmed that the onset of homogeneous freezing of ammonium sulfate particles larger than ~100 nm was not detected at conditions consistent with expectations from theory. Current work involves modeling of the fluid dynamical and thermodynamical fields through the chamber, isolating particle trajectories from these fields, and running a microphysical model along these trajectories. The microphysical model is initialized with a distribution of dry particles of specified composition and the processes simulated include deliquescence, diffusional growth of droplets and crystals, and homogeneous freezing.
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- 9.Pruppacher, H.R., and Klett, J.D., Microphysics of Clouds and Precipitation, Boston: Kluwer (1997).Google Scholar