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Sponginess in ice grown by accretion
Author(s) -
Roos D. V. D. S.,
Pum H.D. R.
Publication year - 1974
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.49710042611
Subject(s) - ice crystals , accretion (finance) , ice formation , materials science , geology , mineralogy , optics , atmospheric sciences , physics , astrophysics
Abstract Ice was grown by accretion on rotating embryos at air temperatures of −6, −12 and −24°C while the liquid water content ranged approximately between 1 and 4 g m −3 . The air speed in the wind tunnel and the modal droplet diameter were, respectively, 20 m s −1 and 13 μm. Details of the structure of the spongy ice were studied in thin sections after elimination of internal liquid water by centrifuging. Sponginess occurred in radial zones associated with surface protuberances but did not necessarily coincide with the indentations between them. Radial striations and tangential microlayers of some 200 μm thickness were found and point to a complex original ice‐water interface. About half of the spongy specimens were allowed to freeze undisturbed. The subsequent transparent ice contained patches of air bubbles mostly of some 20 μm in diameter showing distinctive arrangements and a log‐normal size distribution. Crystals were elongated in the growth direction while optic axes tended to lie normal to it, 67° being the average value of the angle between the projection of the c ‐axis on the plane of the hailstone section and the growth direction. This tendency confirms epitaxial growth during the later stages of freezing.