Isotopic, Crystal and Air Bubble Structures of Hailstones

William C. Macklin National Center for Atmospheric Research, Boulder, Colo. 80303

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Charles A. Knight National Center for Atmospheric Research, Boulder, Colo. 80303

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Howard E. Moore National Center for Atmospheric Research, Boulder, Colo. 80303

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Nancy C. Knight National Center for Atmospheric Research, Boulder, Colo. 80303

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Walter H. Pollock National Center for Atmospheric Research, Boulder, Colo. 80303

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John N. Carras Department of Physics, University of Western Australia, Nedlands

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Suszanne Thwaiters Department of Physics, University of Western Australia, Nedlands

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Abstract

The deuterium, crystal and air bubble structures of 11 large hailstones from three severe storms have been examined. It is emphasized that there are a number of assumptions underlying the interpretation of such data and these are discussed. In seven of the hailstones the ambient temperatures at which they grew were inferred from the crystal size. The deuterium concentrations and ambient temperatures generally show similar variations and the crystal data thereby provide a useful way of placing an absolute temperature scale against the deuterium values. Throughout most of their growth, the hailstones grew in the updraft between about the ambient temperature levels of –17 to –30°C. The air bubble analyses showed that the hailstones grew near the wet growth limit or slightly wet and heat balance considerations give values of 2–3 g m−3 for the effective liquid water concentrations. On the assumption that the median volume radius of the cloud droplets is 10 µm, the actual liquid water concentrations are then about 4 to 5.5 g m−3.

Abstract

The deuterium, crystal and air bubble structures of 11 large hailstones from three severe storms have been examined. It is emphasized that there are a number of assumptions underlying the interpretation of such data and these are discussed. In seven of the hailstones the ambient temperatures at which they grew were inferred from the crystal size. The deuterium concentrations and ambient temperatures generally show similar variations and the crystal data thereby provide a useful way of placing an absolute temperature scale against the deuterium values. Throughout most of their growth, the hailstones grew in the updraft between about the ambient temperature levels of –17 to –30°C. The air bubble analyses showed that the hailstones grew near the wet growth limit or slightly wet and heat balance considerations give values of 2–3 g m−3 for the effective liquid water concentrations. On the assumption that the median volume radius of the cloud droplets is 10 µm, the actual liquid water concentrations are then about 4 to 5.5 g m−3.

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