Abstract

Artificial accretions with cylindrical symmetry have been grown using a simple wind tunnel. The main features of the apparatus are described. Factors concerning the validity of the simulation of natural hail are discussed. Thin sections of the samples are used to study the crystal fabric of the accretions. This study is devoted mainly to the “dry” regime of growth, and the effects on the fabric of sample rotation during growth and of mixed clouds are reported. In dry growth no effects are observed for rotational speed up to 40 Hz. Marked asperities form on wet and spongy deposits formed at 30–40 Hz; their structure strongly resembles that of icicle lobes in large hailstones. Ice crystals in the airstream are readily captured by and modify the structure of wet and spongy growths. Although ice crystals do not appear to be captured by dry growths in quantities sufficient to influence the growth rates, their presence in the airstream does modify the crystal structure.

In following parts of this series, the effects of annealing on the structural fabric (Part II) and analysis techniques for the structural fabric (Part III) will be presented. Implications for the determination of growth trajectories will be discussed.

This content is only available as a PDF.