I. Introduction The efficiencies with which atmospheric aerosols are removed form the air are not well known, either for wet or dry processes. Much effort has been spent in modeling the probabilities that coagulating particles will stick to one another, or to nascent cloud droplets or ice crystals, or to the earth's diverse surfaces, as functions of particle type and size. This research has the objective of designing a new tracer technology that detects and scales individually tagged fluorescent aerosol particles. It has been demonstrated large improvements in detection sensitivity and utility over previous techniques using fluorescent tracers, and practical calibration for size-scaling by fluorescent amplitudes. A dual-wavelength fluorescent-scattering optical particle counter that can be optimized for low count rates, with capability for in-flight measurements will be constructed as a part of this effort. Additionally improved techniques for dispersing tagged aerosols, to determine the effective ranges and times over which these particles can be detected, to measure the frequency- and size-spectra of naturally occurring fluorescent aerosols, and to measure the differential loss rated of hydrophobic and hydrophilic fluorescent aerosols, both in laboratory environmental chambers and in ambient clouds will be investigated.
