On the Distribution of Water-Insoluble Aerosol Particles in Hailstones and Its Possible Value as an Indication of the Hail Growth History

Abstract

The distribution of water-insoluble aerosol particles with diameters in the range 3 to 60 (m has been studied as a function of hailstone radius for a collection of large hailstones. Most of the stones had opaque (probably graupel) embryos; a few had transparent (probably frozen drop) embryos. The concentration of particles within the opaque hailstone embryos was substantially smaller than the concentration of particles within the outer parts of the same hailstones, suggesting that the bulk of the hailstone growth had occurred in a different part of the storm from the region of embryo formation. It seems that the opaque embryos (graupel) form in weak updrafts and then grow into large haillstones upon entering an updraft core which is fed by dust-laden air originating closer to the ground. The transparent embryos were found to contain many more particles than the opaque embryos, perhaps indicating a different place of origin and also indicating an active role by the large particles ingested by a storm in the development of the transparent embryos.