The Growth Rates and Densities of Ice Crystals between −3°C and −21°C

B. F. Ryan CSIRO, Sydney, Australia

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E. R. Wishart CSIRO, Sydney, Australia

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D. E. Shaw CSIRO, Sydney, Australia

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Abstract

Ice crystals were grown in a supercooled cloud at temperatures ranging from −3°C to −21°C for periods from 30–40 s to 150–180 s. When the axial dimensions at a given time were examined as a function of temperature, there was a marked maximum along the a axis at −15°C and a secondary broader maximum along the c axis at −6°C. The growth of the axial dimensions can he adequately represented by a linear function of time.

A power function of time was fitted to the crystal mass growth measurements; these show a sharp maximum at −15°C and a secondary broader maximum at −7°C.

Crystal bulk densities estimated from the masses and axial dimensions vary with temperature in a complicated way, with a minimum of about 0.4 Mg m−2 at −5 and − 17°C, and a maximum of 0.92 Mg m−2(pure rice) at and appear to he independent of time.

Abstract

Ice crystals were grown in a supercooled cloud at temperatures ranging from −3°C to −21°C for periods from 30–40 s to 150–180 s. When the axial dimensions at a given time were examined as a function of temperature, there was a marked maximum along the a axis at −15°C and a secondary broader maximum along the c axis at −6°C. The growth of the axial dimensions can he adequately represented by a linear function of time.

A power function of time was fitted to the crystal mass growth measurements; these show a sharp maximum at −15°C and a secondary broader maximum at −7°C.

Crystal bulk densities estimated from the masses and axial dimensions vary with temperature in a complicated way, with a minimum of about 0.4 Mg m−2 at −5 and − 17°C, and a maximum of 0.92 Mg m−2(pure rice) at and appear to he independent of time.

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