Size Distributions of Stratospheric Aerosols and their Variations with Altitude and Time

Abstract

A description is given of the variation with altitude and time of the size distributions and concentrations of stratospheric particles collected with impactors carried on 35 Australian balloon flights from latitude 34°S in the five years May 1969 to April 1974. Seasonal variations were found to be confined mainly to the lower stratosphere, where a winter maximum of small particles was followed by a spring maximum of large particles. Longer-term trends showed only one conspicuous feature, a decrease in concentration of about one order of magnitude in 1971. The earlier concentrations were restored by the beginning of 1972 by an increase commencing in late August 1971. The size distributions as a function of attitude were very similar to those obtained by lunge and his colleagues with balloon-borne equipment in the United States 10 years earlier and with those in Wyoming in 1972. The main features are a modal diameter around 0.2 μm at the top of the layer which falls to less than 0.1 μm at lower levels. There is also some indication of an inflection in the lower-level curves at about 0.5 μm diameter.