Stratospheric Aerosol Size Distribution

Abstract

On the basis of observational results with ruby laser radar (λ=6943 Å) backscattering and data on small ions, we examined typical stratospheric aerosol size distribution so far proposed.
Power law size distribution and bimodal size distribution can explain both the laser radar backscattering coefficient and small ion density if we take into account the existence of numerous Aitken particles. Thus we cannot determine aerosol size distribution uniquely at the present stage of the investigations. We will examine here bimodal size distribution in some detail by considering the elementary physical processes.
Power law size distribution, we suppose, is produced by in situ sulfuric acid particle nucleation. This size distribution is modified by increased outer particle injection such as a meteor particle or a volcanic eruption.
When meteor particles are undergoing sedimentation, eddy diffusion, and growing by attachment of sulfuric acid particles which have a mean radius 5×10^-3μm, assuming the power law size distribution, then meteor particle size distribution is lognormal. Bimodal size distribution is formed by both the lognormal size distribution and the preexisting Aitken size sulfuric acid particles.