Variability of the Size Distributionsof Atmospheric Aerosols

Abstract

Observations of the size distribution of atmosnheric aerosols larger than 0.004 µm in radius have been m~de with an electric mobility spectrometer and an optical particle counter. And the variations of size distribution were discussed under such conditions as the normal calm weather, rain, and the exchange of air masses. The size distributions indicating the particle number concentration were converted into the particle surface and the volume distributions. The volume distribution was usually bimodal on calm days, but it sometimes changed into trimodal resulting from the exchange of air masses. The change in the size distribution at night was found to depend on two factors: the coagulation of aerosols, and the condensation of water vapor on the particles.