Ice Particle/Water Droplet Discrimination with an Optical Ice Particle Counter

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Abstract
The capability of a Mee Industries Model 120 ice particle counter (IPC) to differentiate between ice particles and water drops was investigated in laboratory and field studies. The threshold voltage setting as well as the particle size were found to be critical in determining counting efficiency. The results show that ice crystals are counted with an efficiency more than ten times as high as are water drops of the same average size. Increasing the threshold voltage setting of the instrument increases the discrimination factor but also results in a decrease in the absolute number of particles counted. The availability of concurrent information on particle sizes and concentrations from other probes allows the Mee IPC phase determinations to be made with much greater confidence. Methods for utilizing data from the Mee IPC as well as the limitations of the instrument are discussed.