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Microphysical processes affecting stratospheric aerosol particlesPhysical processes which affect stratospheric aerosol particles include nucleation, condensation, evaporation, coagulation and sedimentation. Quantitative studies of these mechanisms to determine if they can account for some of the observed properties of the aerosol are carried out. It is shown that the altitude range in which nucleation of sulfuric acid-water solution droplets can take place corresponds to that region of the stratosphere where the aerosol is generally found. Since heterogeneous nucleation is the dominant nucleation mechanism, the stratospheric solution droplets are mainly formed on particles which have been mixed up from the troposphere or injected into the stratosphere by volcanoes or meteorites. Particle growth by heteromolecular condensation can account for the observed increase in mixing ratio of large particles in the stratosphere. Coagulation is important in reducing the number of particles smaller than 0.05 micron radius. Growth by condensation, applied to the mixed nature of the particles, shows that available information is consistent with ammonium sulfate being formed by liquid phase chemical reactions in the aerosol particles. The upper altitude limit of the aerosol layer is probably due to the evaporation of sulfuric acid aerosol particles, while the lower limit is due to mixing across the tropopause.
Document ID
Document Type
Reprint (Version printed in journal)
Hamill, P.
(NASA Ames Research Center Moffett Field, CA, United States)
Toon, O. B.
(NASA Ames Research Center Theoretical and Planetary Studies Branch, Moffett Field, Calif., United States)
Kiang, C. S.
(National Center for Atmospheric Research Boulder, Colo., United States)
Date Acquired
August 9, 2013
Publication Date
July 1, 1977
Publication Information
Publication: Journal of the Atmospheric Sciences
Volume: 34
Subject Category
Accession Number
Funding Number(s)
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