Air Bubbles in Hailstones

Roland List Dept. of Physics, University of Toronto, Toronto, Canada

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William A. Murray Dept. of Physics, University of Toronto, Toronto, Canada

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Carole Dyck Dept. of Physics, University of Toronto, Toronto, Canada

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Abstract

The investigation of air bubbles in hailstones has revealed two independent variables which may become the major clues for correlating properties of hailstone shells with icing conditions during growth. They are the characteristics of individual log-normal bubble size distributions and the bubble concentration. Average planar bubble diameters of 42 μ and planar concentrations of ∼500 cm−2 separate opaque shells with many small bubbles from clear or transparent shells with fewer but larger bubbles. The standard deviation of the logarithms of the diameters, σy, of all the cumulative distributions for both clear and opaque ice were found to be the same. This allows direct calculations of mean true (volumetric) diameters and concentrations from mean planar properties measured in hailstone sections or from replicas.

Abstract

The investigation of air bubbles in hailstones has revealed two independent variables which may become the major clues for correlating properties of hailstone shells with icing conditions during growth. They are the characteristics of individual log-normal bubble size distributions and the bubble concentration. Average planar bubble diameters of 42 μ and planar concentrations of ∼500 cm−2 separate opaque shells with many small bubbles from clear or transparent shells with fewer but larger bubbles. The standard deviation of the logarithms of the diameters, σy, of all the cumulative distributions for both clear and opaque ice were found to be the same. This allows direct calculations of mean true (volumetric) diameters and concentrations from mean planar properties measured in hailstone sections or from replicas.

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