Abstract
The depletion of water vapor during humidification of filter samples, which introduces complications in the determination of ice nucleus concentrations, is considered in detail. A complete solution of the problem appears beyond reach because of the dependence of the depletion effect on the activation spectrum of nuclei; these spectra cannot be determined independently.
Measurements showed that depletion by activated nuclei is more important than by hygroscopic particles. A simple “area-of-effect” model was found to fit the observations relatively well. A generalized correction factor was derived with which the true concentrations of nuclei can be found from measured concentrations.
