Cylindrical Ice Accretions as Simulations of Had Growth:III Analysis Techniques and Application to Trajectory Determination

E. Ashworth Mining Engineering Department and Physics Department, South Dakota School of Mines and Technology, Rapid City 57701

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T. Ashworth Mining Engineering Department and Physics Department, South Dakota School of Mines and Technology, Rapid City 57701

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Charles A. Knight National Center for Atmospheric Research, Boulder, CO 80307

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Abstract

Crystal size parameters are studied, using cylindrical accretions formed from supercooled cloud in dry growth in a wind tunnel as a function of deposit temperature and cloud temperature. Effects of recrystallization, of interpretation of crystal boundaries and of the technique of making thin sections are explicitly examined. The crystal features are in general influenced in important ways by all of these variables. A shape factor is defined–a measure of grain elongation–and found to reflect the degree of recrystallization. Similarities to and differences from previous experimental results are discussed and the applicability of these results to interpreting natural hailstones is examined. Relatively crude but useful deductions of temperature (or altitude) of growth can be made with confidence, but detailed deductions would have to be verified in some independent way at the present state of knowledge.

Abstract

Crystal size parameters are studied, using cylindrical accretions formed from supercooled cloud in dry growth in a wind tunnel as a function of deposit temperature and cloud temperature. Effects of recrystallization, of interpretation of crystal boundaries and of the technique of making thin sections are explicitly examined. The crystal features are in general influenced in important ways by all of these variables. A shape factor is defined–a measure of grain elongation–and found to reflect the degree of recrystallization. Similarities to and differences from previous experimental results are discussed and the applicability of these results to interpreting natural hailstones is examined. Relatively crude but useful deductions of temperature (or altitude) of growth can be made with confidence, but detailed deductions would have to be verified in some independent way at the present state of knowledge.

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